Mixing of Miscible Liquids

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Mixing of Miscible Liquids

Mixing of Miscible Liquids
0 INTRODUCTION/PURPOSE
1 SCOPE
2 FIELD OF APPLICATION
3 DEFINITIONS
4 SELECTION OF EQUIPMENT
4.1 Mechanically Agitated Vessels
4.2 Jet Mixed Vessels
4.3 Tubular ('Flow') Mixers

5 AGITATED VESSELS
5.1 Mixing Time for Liquids in Stirred Tanks
5.2 Power Requirements
5.3 Vortex Formation and Surface Entrainment in Unbaffled and Baffled Vessels
5.4 Heat-Transfer in Stirred Vessels
5.5 Flow and Circulation

6 JET MIXED TANKS
6.1 Introduction
6.2 Recommended Configuration
6.3 Design Procedure
6.4 Design for Continuous Mixing

7 TUBULAR JET FLOW MIXERS FOR MISCIBLE LIQUIDS
7.1 Recommended Configurations
7.2 Mixer Design
7.3 Additional Considerations

8 MOTIONLESS MIXERS
8.1 Recommended Types
8.2 Correlations

TABLES

1 TYPICAL CONSTANTS FOR EQUATION (1)
2 POWER CURVES FIGURES AND CORRECTION FACTORS
3 VORTEX PARAMETERS, TURBINE, PROPELLER AND SAWTOOTH
4 CHARGING A HOT VESSEL WITH A COLD PRODUCT
5 INJECTING A HOT FLUID INTO THE JACKET OF A COLD VESSEL
6 TYPICAL DISCHARGE COEFFICIENTS
7 CONSTRAINTS FOR LAMINAR FLOW MOTIONLESS MIXERS
8 CONSTANTS FOR TURBULENT FLOW MOTIONLESS MIXERS
9 LENGTH FACTORS FOR HIGH VISCOSITY RATIOS

FIGURES
1 POWER NUMBERS FOR 45° ANGLED-BLADE TURBINES
2 CORRECTION FACTORS FOR DIAMETER RATIOS
3 BLADE ANGLE AND THICKNESS CORRECTION FACTORS
4 POWER NUMBERS FOR SINGLE 60° ANGLED-BLADE TURBINES
5 POWER NUMBERS FOR TWIN 60° ANGLED-BLADE TURBINES
6 POWER NUMBERS FOR TRIPLE 60° ANGLED-BLADE TURBINES
7 BAFFLE WIDTH AND NUMBER CORRECTION FACTORS FOR DIFFERENT DIAMETER RATIOS
8 CORRECTION FACTORS FOR SUBMERGENCE
9 CORRECTION FACTORS FOR SEPARATION
10 POWER NUMBERS FOR DISC-TURBINES
11 CORRECTION FACTORS FOR BAFFLES
12 CORRECTION FACTORS FOR BASE CLEARANCE
13 CORRECTION FACTORS FOR SUBMERGENCE
14 POWER NUMBERS FOR RETREAT-CURVE IMPELLERS
15 CORRECTION FACTORS FOR PARTIAL BAFFLES
16 POWER NUMBERS CORRECTION FACTORS FOR RETREAT-CURVE AND IMPELLERS H/T RATIOS OF 2.0
17 POWER NUMBERS FOR FLAT-BLADED TURBINES
18 BOTTOM CLEARANCE CORRECTION FACTOR
19 POWER NUMBERS FOR ANCHOR AND GATE AGITATORS
20 POWER NUMBERS FOR PROPELLERS
21 IMPELLER SPACING CORRECTION FACTORS
22 STANDARD NOTATION FOR VORTEX CALCULATIONS
23 VORTEX DATA FOR 2 - BLADED PADDLES
(W/D = 0.33, T/D = 2)
24 VORTEX CORRECTION FACTORS FOR PADDLES
25 JET DIRECTION
26 SINGLE JET MIXERS
27 MULTIJET MIXERS
28 SERIES ARRANGEMENT OF MIXERS
29 BATCH MIXERS
30 DESIGN PROCEDURE
31 EMPIRICAL FACTORS
32 RECIRCULATION ZONES
33 FRICTION FACTOR DATA FOR KENICS AND SULZER MIXERS

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Mixing of Miscible Liquids

  1. 1. GBH Enterprises, Ltd. Process Engineering Guide: GBHE-PEG-MIX-701 Mixing of Miscible Liquids Information contained in this publication or as otherwise supplied to Users is believed to be accurate and correct at time of going to press, and is given in good faith, but it is for the User to satisfy itself of the suitability of the information for its own particular purpose. GBHE gives no warranty as to the fitness of this information for any particular purpose and any implied warranty or condition (statutory or otherwise) is excluded except to the extent that exclusion is prevented by law. GBHE accepts no liability resulting from reliance on this information. Freedom under Patent, Copyright and Designs cannot be assumed. Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  2. 2. Process Engineering Guide: Mixing of Miscible Liquids CONTENTS SECTION 0 INTRODUCTION/PURPOSE 4 1 SCOPE 4 2 FIELD OF APPLICATION 4 3 DEFINITIONS 4 4 SELECTION OF EQUIPMENT 4 4.1 4.2 4.3 Mechanically Agitated Vessels Jet Mixed Vessels Tubular ('Flow') Mixers 4 4 5 5 AGITATED VESSELS 5 5.1 5.2 5.3 6 9 5.4 5.5 Mixing Time for Liquids in Stirred Tanks Power Requirements Vortex Formation and Surface Entrainment in Unbaffled and Baffled Vessels Heat-Transfer in Stirred Vessels Flow and Circulation 34 39 44 6 JET MIXED TANKS 45 6.1 6.2 6.3 6.4 Introduction Recommended Configuration Design Procedure Design for Continuous Mixing 45 45 46 51 Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  3. 3. 7 TUBULAR JET FLOW MIXERS FOR MISCIBLE LIQUIDS 51 7.1 7.2 7.3 Recommended Configurations Mixer Design Additional Considerations 55 55 60 8 MOTIONLESS MIXERS 63 8.1 8.2 Recommended Types Correlations 63 63 TABLES 1 TYPICAL CONSTANTS FOR EQUATION (1) 7 2 POWER CURVES FIGURES AND CORRECTION FACTORS 10 VORTEX PARAMETERS, TURBINE, PROPELLER AND SAWTOOTH 35 4 CHARGING A HOT VESSEL WITH A COLD PRODUCT 43 5 INJECTING A HOT FLUID INTO THE JACKET OF A COLD VESSEL 44 6 TYPICAL DISCHARGE COEFFICIENTS 45 7 CONSTRAINTS FOR LAMINAR FLOW MOTIONLESS MIXERS 64 CONSTANTS FOR TURBULENT FLOW MOTIONLESS MIXERS 65 LENGTH FACTORS FOR HIGH VISCOSITY RATIOS 65 3 8 9 Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  4. 4. FIGURES 1 POWER NUMBERS FOR 45° ANGLED-BLADE TURBINES 12 2 CORRECTION FACTORS FOR DIAMETER RATIOS 13 3 BLADE ANGLE AND THICKNESS CORRECTION FACTORS 13 4 POWER NUMBERS FOR SINGLE 60° ANGLED-BLADE TURBINES 14 POWER NUMBERS FOR TWIN 60° ANGLED-BLADE TURBINES 15 POWER NUMBERS FOR TRIPLE 60° ANGLED-BLADE TURBINES 16 BAFFLE WIDTH AND NUMBER CORRECTION FACTORS FOR DIFFERENT DIAMETER RATIOS 19 8 CORRECTION FACTORS FOR SUBMERGENCE 19 9 CORRECTION FACTORS FOR SEPARATION 19 10 POWER NUMBERS FOR DISC-TURBINES 20 11 CORRECTION FACTORS FOR BAFFLES 22 12 CORRECTION FACTORS FOR BASE CLEARANCE 22 13 CORRECTION FACTORS FOR SUBMERGENCE 23 14 POWER NUMBERS FOR RETREAT-CURVE IMPELLERS 24 15 CORRECTION FACTORS FOR PARTIAL BAFFLES 26 16 POWER NUMBERS CORRECTION FACTORS FOR RETREATCURVE AND IMPELLERS H/T RATIOS OF 2.0 26 17 POWER NUMBERS FOR FLAT-BLADED TURBINES 27 18 BOTTOM CLEARANCE CORRECTION FACTOR 29 5 6 7 Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  5. 5. 19 POWER NUMBERS FOR ANCHOR AND GATE AGITATORS 30 20 POWER NUMBERS FOR PROPELLERS 32 21 IMPELLER SPACING CORRECTION FACTORS 33 22 STANDARD NOTATION FOR VORTEX CALCULATIONS 37 23 VORTEX DATA FOR 2 - BLADED PADDLES (W/D = 0.33, T/D = 2) 37 24 VORTEX CORRECTION FACTORS FOR PADDLES 38 25 JET DIRECTION 47 26 SINGLE JET MIXERS 52 27 MULTIJET MIXERS 53 28 SERIES ARRANGEMENT OF MIXERS 54 29 BATCH MIXERS 54 30 DESIGN PROCEDURE 56 31 EMPIRICAL FACTORS 60 32 RECIRCULATION ZONES 62 33 FRICTION FACTOR DATA FOR KENICS AND SULZER MIXERS 66 DOCUMENTS REFERRED TO IN THIS PROCESS ENGINEERING GUIDE 67 Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  6. 6. 0 INTRODUCTION This Guide is one in a series of Mixing Guides and has been produced for GBH Enterprises. 1 SCOPE This Guide caters for the majority of mixing duties for miscible liquids, but does not cover the more specialized cases for which reference should be made to mixing experts. The Guide is divided into 4 main sections dealing with the mixing devices most commonly employed for miscible liquid systems, namely Stirred Vessels, Jetmixed Vessels, Jet Flow Mixers and Static (or Motionless) Mixers. 2 FIELD OF APPLICATION This Guide applies to Process Engineers in GBH Enterprises worldwide. 3 DEFINITIONS No specific definitions apply to this Guide. 4 SELECTION OF EQUIPMENT All considerations refer to macro-mixing, i.e. blending and uniformity throughout the vessel. Mixing on smaller, local scales (micro-mixing) is not covered at present, and will follow different trends and rules. The operating costs, as measured by the energy required per unit throughput, for the mixers are likely to be similar. Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  7. 7. 4.1 Mechanically Agitated Vessels Mechanically agitated vessels are very versatile. They can be operated in either a batch or continuous mode. They are suitable for use where long mixing times (10 - 10000 secs or longer) can be tolerated and where long residence times are desirable. The mixing time is generally independent of throughput, in contrast to 'flow' mixers. With the appropriate choice of agitator they can handle the entire range of liquid viscosities. Power input per unit volume is usually low. The capital cost of the tank and agitator system is high. Heat transfer area per unit volume is not large, especially for large vessels. It can be extended either by the use of internal coils, or by an external recycle pumped through a heat exchanger. Exotherms can also be handled by boiling and condensation and, since the vessel is backmixed, some of the heat of reaction can be absorbed by feeding in ”cold” inlet streams. 4.2 Jet Mixed Vessels Jet mixed tanks are usually used only to blend low viscosity liquids (so that Re j 1000) with a jet to bulk density difference of less than about 30%. They can be operated in either a batch or continuous mode. Mixing times are of the same order of magnitude as stirred tanks. For the same mixing duty, a jet mixed tank has a lower energy efficiency than a mechanically agitated tank. For a given duty the capital cost of a jet mixed tank will be lower than that of a mechanically agitated vessel. Jet mixing can be particularly attractive in terms of capital cost for very large, irregularly shaped vessels such as lagoons and reservoirs. 4.3 Tubular ('Flow') Mixers Tubular mixers e.g. jet mixers, motionless mixers, orifice plates, venturis, etc are essentially continuous flow devices although they can be used in batch loop recycle systems. Their principal uses are: Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  8. 8. (a) the continuous blending of miscible liquids over the whole range of liquid viscosity; (b) the rapid (0.01 - 5 seconds) contacting of low viscosity reactants for a `”fast” reaction especially when the product spectrum is affected by the mixing rate; (c) the processing of hazardous liquids where the amount being processed at any instant must necessarily be small. High heat transfer rates are possible with these devices because of the intense turbulence and the high surface area to volume ratio. The capital costs of this type of mixer are very low compared with jet mixed and mechanically agitated tanks. However, the continuous, plug flow short residence time characteristics of these devices may mean that instrumentation costs are higher. When used in 'single pass' configurations the mixing performance depends upon the throughput. The requirement of mixing intensity determines the diameter and residence time fixes the length for a given process flowrate. This means that the tube gets narrower and longer with scale-down. 5 AGITATED VESSELS The main parameters in the design of agitated (or stirred) vessels for mixing miscible liquids are: (a) Mixing time; (b) Power requirements; (c) Vortex formation; (d) Heat transfer; (e) Flow and circulation. Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  9. 9. 5.1 Mixing Time for Liquids in Stirred Tanks In many processes it is important to mix reactants quickly and thoroughly. This can be assessed for any system by the overall 'mixing time', which is the time taken to reduce the root mean square concentration variations by a factor, frequently 20. This is the 95% mixing time, tm95%. Prediction of mixing time from the literature is not easy and values should not be relied on to better than ± 50%. In practice the designer usually only wants to know if a vessel is "adequately mixed" so this degree of precision is normally sufficient. If more precise values are required, specific experiments carefully related to the particular problem are recommended. If scale model measurements can be done easily, they are more reliable than prediction from the correlations given below. Mixing time depends strongly on circulation flows through the vessel, especially for low viscosity systems, so results in the turbulent region (Re > 104) scale up well with the relation "mixing time × agitator speed = constant". The constant is called 'the dimensionless mixing time'. 5.1.1 Low Viscosity Newtonian Liquids For low viscosity Newtonian liquids mixing is usually best performed with a turbine or propeller type agitator. The best configuration is with: (See Figure 1 for definition of symbols. Pitch is the liquid progression distance per revolution; a is the angle of the blade to the horizontal. Down-pumping turbines have a!< 90°.) Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  10. 10. Baffles increase the vertical circulation and thus are an effective means of shortening mixing time (but at the cost of increase power) and also reduce the complicating factors of vortex formation on prediction. Data on mixing times in unbaffled vessels is sparse but for a crude estimate the mixing time for the same vessel with baffles, at the same power, can be used. Fluid density differences can significantly increase mixing time. Mixing times (95%) for these systems can be predicted from correlations involving the power number (Po). These can be calculated by the methods given in 5.2. For low viscosity liquids; The density and viscosity is that of the mixed liquid. First calculate Po1/3 × Re. If the value is greater than or equal to 6400 then use the appropriate constant as listed in Table 1. For values less than 6400 use equation (3) developed for high viscosity Newtonian liquids. Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  11. 11. TABLE 1 TYPICAL CONSTANTS FOR EQUATION (1) 5.1.2 High Viscosity Liquids For high viscosity liquids the best agitators are either stacked pitched blade turbines, helical screws, straight anchors or bent anchors (see GBHE-PEG-MIX700). As fluid motion decays more rapidly with distance from the agitator than with low viscosity fluids, relatively larger agitators are needed which sweep a greater volume of liquid. To estimate mixing times (and power) with Newtonian liquids use: For turbine-type agitators with Newtonian liquids the formula developed by FMP can be used. Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  12. 12. If the liquid is known or suspected to be non-Newtonian a rheogram of shear stress versus shear rate should be obtained (see GBHE-PEG-FLO-302). If the data is not available it should be measured. If the shear stress is low at low shear rates, then the mixing time should be calculated as if the liquid were Newtonian. (If in doubt calculate Ns as described below and check it is an order of magnitude smaller than the working speed.) For determination of the appropriate "apparent" viscosity use the Metzner and Otto relation: Values of k s for typical configurations are: If there is a significant shear stress at zero shear rate (a "yield stress") and a turbine-type agitator is being used then a cavern of well mixed material may form round the agitator while the material near the walls and surface of the vessel remains unmixed. In this case rather than try to estimate mixing times it is better to use a correlation from the work of Solomon (1981) and Elson (1985) to estimate the minimum agitator speed for the cavern size to equal the vessel size (equation 5). Under this condition the vessel can be considered well mixed. Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  13. 13. It is assumed that the agitator is half way up the vessel. If this is not so, for a safe design, replace H by twice the distance from the agitator to the surface or twice the distance from the agitator to the bottom, whichever is the greater. Etchells (1987) suggests that this approach should apply to materials where the "yield stress" is at least (5 × the viscosity at infinite shear × the shear rate). This is the case for many slurries. 5.2 Power Requirements 5.2.1 Levels of Power Input Power inputs from agitators to low-viscosity Newtonian liquids are usually in the range 100 to 2000 W/m3; though for some applications, inputs of 4000 to 10000 W/m3 are used. Power inputs above this level are rare in stirred tanks and are difficult to achieve using conventional agitators. They tend to be restricted to tanks of 2 m3 capacity or smaller, where very short mixing times are required, as in polythene reactors which run at 100 to 200 W/m3. Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  14. 14. 5.2.2 Factors Affecting Power Dissipation Power dissipation is a function of agitator geometry, speed of rotation, fluid properties, vessel fittings, vessel geometry and fluid aspect ratio. Fluid properties are characterized by Reynolds and/or Froude Numbers: up to Re of the order of 10 to 30 the flow is mainly viscous and power dissipation is proportional to viscosity and independent of density. As Re increases above about 1000, the flow is essentially turbulent and the power is much more dependent on density than viscosity. Geometries, fittings and speed are usually interdependent in complex ways and their effects vary between systems. 5.2.3 Power Correlation It has been shown that the power supplied by an agitator can be expressed by: P/(ρ N3 D5) = fn ((N D2 u/µ).(N2 D/g). R1....RI) where R1....Ri represent the various geometric ratios describing the agitator and vessel. For a given agitator-vessel system this gives: P/(ρ N3 D5) = Po = K (N D2 ρ/µ)m. (N2 D/g)n where Po is the Power Number of the agitator-vessel system and is comparable to the drag coefficient in a flowing fluid system. At Re < 10, m tends to -1 and at high Re it tends to zero, especially in baffled vessels. In fully baffled vessels and systems with no free liquid surface, n becomes zero. K depends upon the geometry. The correlation of Po with Re is universally recognized as a reliable means of predicting power requirements at widely differing scales of operation for geometrically similar vessels. The correlation must be established experimentally for each geometric system, which has a unique Po-Re relationship. Graphs of Po vs Re data for a number of basic impeller designs are presented here: deviations from the "standard" designs have to be allowed for by using a series of correction factors. Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  15. 15. 5.2.4 Calculation of Power (a) Calculate the agitator Reynolds Number (ND ρ/µ). (b) Select appropriate power curve for the type and geometry of agitator (see Table 2), and read the value of Po for Re obtained under (a). (c) Tabulate the variations between the actual agitator and the "standard" design, as illustrated in the same Figure as the power curve. (d) Use appropriate Figure for the agitator (as listed in Table 2). (e) Determine the relevant correction factors for each variation from the "standard". (f) Multiply the value of Po by these correction factors. (g) Calculate the power (P = Po ρ N D ). 2 3 5 Note: that commercially available programs are available to calculate the power. Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  16. 16. TABLE 2 POWER CURVES FIGURES AND CORRECTION FACTORS Power numbers for 'hydrofoils' can be found in the GBHE Mixing and Agitation Manual. 5.2.5 Correction Factors for Power Numbers of 45° Angled-Blade Turbines For impellers and vessel configurations different from the standard system shown in Figure 1, multiply the standard power number by each correction factor described below: (a) Vessel diameter (T ) No correction factor recommended. (b) Baffle-width (W b ) T/10 flat baffles, Cb = T/12 flat baffles, Cb = 1.10 1.0 no wall gap no wall gap. Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  17. 17. (c) Non-standard internals: assume an otherwise unbaffled vessel except for the helical coil: Single finger baffle, Twin finger baffles, Beavertail baffle, Triangular wall baffle, Single dip-pipe, Ringlet coil (a), C i = 0.71 C i = 0.81 C i = 0.74 C i = 0.97 ... projected W b = T/9 C i = 0.56 ... diameter = T/23 C i = 0.73 ... tube od = T/55 pitch!= T/34 coil pitch = T/8 Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  18. 18. (j) Blade angle and thickness (a and X) The correction factor Ca is plotted in Figure 3, note that Po is a very strong function of angle and errors of 2.5 will alter Po by 10%. All the data refers to downward pumping impellers; for upward pumping impellers use an additional correction factor of 0.9. Data from 3 bladed turbines will probably be within 10% of that for 4 blades. FIGURE 1 POWER NUMBERS FOR 45° ANGLED-BLADE TURBINES Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  19. 19. Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  20. 20. FIGURE 2 CORRECTION FACTORS FOR DIAMETER RATIOS FIGURE 3 BLADE ANGLE AND THICKNESS CORRECTION FACTORS Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  21. 21. FIGURE 4 POWER NUMBERS FOR SINGLE 60° ANGLED-BLADE TURBINES Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  22. 22. FIGURE 5 POWER NUMBERS FOR TWIN 60° ANGLED-BLADE TURBINES Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  23. 23. FIGURE 6 POWER NUMBERS FOR TRIPLE 60° ANGLED-BLADE TURBINES Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  24. 24. Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  25. 25. 5.2.6 Correction Factors for Power Numbers of 60° Angled-Blade Turbines For impellers and vessel configurations different from the standard system shown in Figure 4, multiply the standard power number by each correction factor described below. Note that these correction factors, where relevant, also apply to dual and triple 60° angled-blade impellers. (a) Vessel diameter (T ) C t = (T/0.304) -0.08 (b) range 0.2 T 3.0 m Baffle width (W b ) Use Figure 7. (c) Non-standard internals: assume an otherwise unbaffled vessel, except for the helical coil: 4 × T/12 flat wall baffles + T/40 wall-gap 4 × T/10 flat wall baffles + no wall-gap 4 × T/10 profiled (triangular) wall baffles 4 × T/12 + wall gap.....half vessel height 1 × finger baffle 2 × finger baffles 1 × beavertail baffle 2 × beavertail baffles 1 × ringlet coil 1 × dip-pipe or tubular thermopocket 2 × dip-pipes or tubular thermopockets Helical coil (coil pitch > tube diameter) Helical coil....treat supports as baffles. (d) Ci = 1.00 Ci = 1.10 Ci = 0.97 Ci = 0 92 Ci = 0.70 Ci = 0.80 Ci = 0.84 Ci = 1.10 Ci = 0.73 Ci = 0.40 Ci = 0.50 Ci = 1.00 Diameter ratio (D/T ) See Figure 2, also for 45° impellers. (e) Bottom clearance (Z/D) Cc = (Z/0.537D) -0.20 range 0.33 Z/D 1.10 Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  26. 26. (f) Submergence (S/T ) See Figure 8. (g) Number of blades (n) n Cn =2 = 0.60 (h) Blade width (Wp) 3 0.87 4 1.00 5 1.17 6 1.28 C w = (Wp/0.336D)1.17 (j) 0.34 Blade angle (a to the horizontal) range 55° a 75° Blade thickness (X ) C x = 1.0 (l) 8 1.41 range 0.2 Wp/D Ca = ( [sin a ] /0.866)2.10 (k) 7 1.31 range 0.04 X/W 0.10 Blade roundness Cr = 0.95 r/W = 0.2 X/W = 0.05 to 0.08 Cr = 0.56 (m) corner radius, blade thickness, corner radius, blade thickness, r/W = 0.5 X/W = 0.30 Pumping direction Pumping down Cp = 1.00; Pumping up Cp = 0.91 Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  27. 27. (n) Vessel base shape Dished base C v = 1.00; (p) Flat base C v = 0.98 Multiple impellers For multiple impellers of the same geometry, use Figures!5 and 6. For multiple impellers of mixed geometries, use Figure 21 or the sum of the individual power numbers, which would give high (safe) values. (q) Impeller separation Use Figure 9. FIGURE 7 BAFFLE WIDTH AND NUMBER CORRECTION FACTORS FOR DIFFERENT DIAMETER RATIOS Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  28. 28. FIGURE 8 CORRECTION FACTORS FOR SUBMERGENCE FIGURE 9 CORRECTION FACTORS FOR SEPARATION Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  29. 29. FIGURE 10 POWER NUMBERS FOR DISC-TURBINES Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  30. 30. 5.2.7 Correction Factors for Flat-Bladed "RUSHTON" Disc-Turbines For impellers and vessel configurations different from the standard shown in Figure 10, multiply the standard power number by each correction factor described below: (a) Vessel diameter (T ) Ct = T0.065. (b) Baffle width (W b) Use Figure 11. (c) Non-standard internal fittings No information. Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  31. 31. (d) Diameter ratio (D/T ) Cd = 1.0 (at Z/T = 0.30) (e) range 0.14 D/T 0.70 Bottom clearance (Z/T ) Use Figure 12. (f) Submergence (S) Use Figure 13. (g) Number of blades (n) Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  32. 32. (n) Multiple impellers Use Figure 21 or the sum of individual impellers, where multiple impeller power number data is not available: this gives high (safe) values. FIGURE 11 CORRECTION FACTORS FOR BAFFLES FIGURE 12 CORRECTION FACTORS FOR BASE CLEARANCE Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  33. 33. FIGURE 13 CORRECTION FACTORS FOR SUBMERGENCE FIGURE 14 POWER NUMBERS FOR RETREAT-CURVE IMPELLERS Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  34. 34. 5.2.8 Correction Factors for Power Numbers of Retreat-Curve Impellers For impellers and vessel configurations different from the standard system shown in Figure 14, multiply the standard power number by each correction factor described below. (a) Vessel diameter (T ) No information available. (b) Baffle-width (W b) T/10 flat baffles, C b = 1.0 no wall gap T/12 flat baffles, C b = 1.0 T/40 wall gap Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  35. 35. (c) Non-standard internals: 4x flat wall-baffles taken as the reference power number Also see Figure 15. (d) Diameter ratio (D/T ) C d = (0.8T/D)0.58 (e) Bottom clearance (Z/D) No information available (f) range, 0.5 D/T 0.80 normally, 0.061 Z/D 0.1 Submergence (S/T ) No information available. (g) Batch height (H/T ) See Figure 16. (h) Blade width (W/D) C w = (W/0.125D)0.6 (i) range, 0.1 W/D 0.194 Blade angle and thickness (a and X ) No information available normally, a is 10° or 15°. Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  36. 36. FIGURE 15 CORRECTION FACTORS FOR PARTIAL BAFFLES FIGURE 16 POWER NUMBERS CORRECTION FACTORS FOR RETREATCURVE AND IMPELLERS H/T RATIOS OF 2.0 Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  37. 37. FIGURE 17 POWER NUMBERS FOR FLAT-BLADED TURBINES Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  38. 38. 5.2.9 Correction Factors for Power Numbers of Flat-Bladed Turbines For impeller and vessel configurations different from the standard system shown in Figure 17, multiply the standard power number by each correction factor described below: (a) Vessel diameter (T ) No correction factor recommended. (b) Baffle width (W b) Use Figure 7. (c) Non-standard internals: assume an otherwise unbaffled vessel apart from the helical-coil, which is located on a 4x flat wall-baffle cage: (d) Diameter ratio (D/T ) Use Figure 7. (e) Bottom clearance (Z/T ) Use Figure 18. (f) Submergence (S/T ) Use Figure 13. Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  39. 39. (g) Number of blades (n) See the relationships for Blade width (h) below. (h) Blade width (W ) (j) Blade thickness (X ) Po varies by less than 5% in the range, 0.01 X/D 0.0332 (k) Vessel shape (V ) Flat bottom Dished bottom C v = 1.11 Cv = 1.00 Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  40. 40. FIGURE 18 BOTTOM CLEARANCE CORRECTION FACTOR FIGURE 19 POWER NUMBERS FOR ANCHOR AND GATE AGITATORS Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  41. 41. 5.2.10 Correction Factors for Power Numbers of Anchor and Gate Agitators For impellers and vessel configurations different from the standard system shown in Figure 19, multiply the standard power number by each correction factor described below: (a) Vessel diameter (T ) No correction factor recommended. (b) Blade height (L/D) C l = 0.86L/D + 0.11. Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  42. 42. (c) Agitator shape Cf = 0.89L/D + 0.11n Cf ' = C f (1 + (D i /D)5) (d) n = number of cross-bars for gates > 2 vertical bars Diameter ratio (D/T ) See (e) below. (e) Side & bottom clearance (e/T ) (f) Number of blades (n) No correction factors recommended. (g) Blade width (W/D) C w = 1.0 W/D = 0.083 to 0.125 Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  43. 43. FIGURE 20 POWER NUMBERS FOR PROPELLERS Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  44. 44. 5.2.11 Correction Factors for Power Numbers of Propellers (a) Vessel diameter (T ) No correction factor recommended. (b) Baffle width (W b) FIGURE 21 IMPELLER SPACING CORRECTION FACTORS 1 2 Disc turbines Angled-blade turbines & propellers (pumping in the same direction) Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  45. 45. 5.2.12 Power Numbers for Multiple Impellers Notation Po(c) = Po(1) = Po(2) = Po(n) = combination power number bottom impeller power number 2nd impeller power number nth. Impeller power number (a) Twin impellers - Po(1) + Po(2) × (Po(n)/Po). (b) Triple impellers - Po(1) + [Po(2) + Po(3)] × [Po(n)/Po]. MIXED IMPELLERS, use Po(n)/Po = 1.0 until data becomes available. 5.3 Vortex Formation and Surface Entrainment in Unbaffled and Baffled Vessels Unbaffled vessels were formerly preferred for liquid blending and solid suspension duties. The impeller is usually mounted centrally and except in the case of a sawtooth disc, the designer must check that the vortex does not reach it. The rise of the vortex is obviously critical in open vessels and could be critical in closed vessels where instrument probes or vent lines need to be kept clear of liquid. The general configuration of vessel, impeller and vortex is shown in Figure!22. Off-centre mounting of the agitator can give a flow regime closer to that of a baffled vessel but causes large fluctuating forces on the agitator shaft. Little design information is available and this option is not recommended. A major vortex is not normally generated in fully baffled vessels. In both baffled and unbaffled systems, it may be necessary to avoid gas entrainment into the liquid or to specify conditions under which a light solid may be rapidly incorporated into a liquid surface. (a) Agitator types Data are given for disc-turbines, flat bladed paddles, sawtooth, propeller and anchor agitators. Extensive information is available in the GBHE Mixing and Agitation Manual on paddle mixers, covering a wide range of geometries. Table 3 gives vortex parameters for modern mixers and Figure 22 shows h1 and h2: the displacement of the vortex below and above the original liquid level. Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  46. 46. (b) Parameters covered Vortex depths are related to impeller Reynolds Number (ND2ρ/µ) and Froude Number!(N2D/g). Experimental checks at GBHE have shown that separate equations are not needed for Froude Numbers less than 0.1. 5.3.1 Recommendations Vortex configuration in unbaffled vessels (a) Turbine, propeller and sawtooth relevant k values are in Table 3. (1) For all T/D ratios and Re below 2000: (2) At Reynolds Numbers greater than 5000: Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  47. 47. TABLE 3 VORTEX PARAMETERS, TURBINE, PROPELLER AND SAWTOOTH Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  48. 48. where: Vortex Parameter is shown in Figure 23, and generally f = f1 gives correction factors for h1 and f = f 2 for h2 from the respective graphs in Figure 24. This work performed for GBHE, is the most comprehensive range of correction factors available for paddles. 5.3.2 Avoidance of Gas Entrainment in Standard Baffled Vessels It may be necessary to avoid gas entrainment from the surface in a standard baffled vessel, in which case a maximum impeller speed, above which entrainment could occur, is given below for agitator/vessel diameter ratios in the range 0.33 to 0.47. Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  49. 49. FIGURE 22 STANDARD NOTATION FOR VORTEX CALCULATIONS Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  50. 50. FIGURE 23 VORTEX DATA FOR 2 - BLADED PADDLES (W/D = 0.33, T/D = 2) FIGURE 24 VORTEX CORRECTION FACTORS FOR PADDLES Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  51. 51. 5.4 Heat-Transfer in Stirred Vessels It is seldom that heat-transfer is the only operation to be promoted by agitation and the choice is often a compromise between conflicting requirements. In those cases where heat-transfer considerations are a prime factor in the design, the aim should be to select an impeller design which gives high bulk flowrates of the fluid with good general mixing and high fluid velocities close to the heat-transfer surfaces. Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  52. 52. For low viscosity fluids (up to 1 N.s/m2) flat paddles, angled blade turbines, disc turbines or propellers with D/T ratios of 1/3 to 1/2 can meet these requirements and give broadly similar rates of heat-transfer. The choice between them can be based on other mixing criteria for the process, e.g. suspension of solids, gas dispersion. Note however that relatively small changes of viscosity can influence heat-transfer performance quite markedly. As viscosity increases further to about 3 N.s/m2 the impeller diameter should be increased to give D/T = 2/3 or more, whilst at the same time reducing the blade width to conserve power. At higher viscosities (> 3 N.s/m2) anchor stirrers and dual or triple wide-diameter impellers are used whilst at very high viscosities (> 25 N.s/m2) screw and helix impellers are preferred. Jackets and limpet coils are used extensively on carbon steel, stainless steel and glassed steel vessels. Limpet coils show advantages over jackets in cost, pressure rating and heat-transfer performance. However there can be fatigue problems on limpet coils subjected to thermal cycling. Typical pressure ratings of jackets and limpet coils are 6 bar and 14 bar respectively. Jackets and limpet coils are preferred to internal coils when processing viscous liquids. Jacket heat-transfer performance can be influenced markedly by the use of aids such as jetted feed, tangential inlets, baffles, and multiple outlets. Internal coils are used primarily to supplement heat-transfer area in jacketed vessels and in cases where heat-transfer through the wall is very poor or impracticable, e.g. rubber lined tanks, GRP tanks. Coils are suitable for higher pressure service fluids and in cases where a large corrosion allowance must be provided. Large helical coils are used in twopiece vessels when a long service life is expected. Hairpin and ringlet coils are used in one-piece vessels and often act as baffles in the agitation system. They have the advantage of being easily removed if the process duty changes or in the event of failure. Broadly speaking, jackets, helical coils and ringlet coils of reasonable proportions in a given vessel, are capable of meeting similar heat transfer duties. Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  53. 53. 5.4.1 Correlations and Design Guides Heat-transfer in stirred vessels is brought about primarily through conduction and forced convection. The process is assumed to be governed by the combined resistance of: (a) the wall separating the service and process fluids; (b) the dirt films on each side of the wall and (c) laminar films of process and service fluids adjacent to the wall. Correlations for local coefficients of heat-transfer are of the form: ᵞ = bulk liquid viscosity/viscosity at the wall. (1) Use any Standards which apply, e.g. vessels, jackets, limpet coils, helical coils, ringlet coils, impellers, service pumps, etc. (2) Check that the batch depth lies between about 0.8 and 1.0 vessel diameters. If below this range consider using a smaller vessel; if above the range consider putting additional impellers on the shaft. (3) With low viscosity fluids (< 1 N.s/m2) use an impeller which meets other process duties. A simple, cheap design should be chosen giving high circulation rates and moderate power inputs, e.g. 0.5 to 0.7 kW/m3 in baffled vessels, 0.2 to 0.5 kW/m 3 in unbaffled vessels. Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  54. 54. (4) In viscous fluids, impeller blades should reach close to the fluid surface, even if this means adding additional impellers or crossmembers. Blade widths and wall clearances should be about 1/10 of the vessel diameter. (5) In non-jacketed vessels, helical coil diameters are close to the tank diameter: the coil often being supported by the tank wall about 50 to 150 mm away from it. In jacketed vessels where the coil is supplementing the jacket, the coil diameter should be about 90% of the vessel diameter. (6) When multiple concentric helical coils are used, care must be taken to stagger and increase the pitch to ensure they do not shield each other. (7) Tube diameters for coils vary between 25 and 100 mm; by far the most common sizes being 37 to 50 mm. Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  55. 55. 5.4.2 Correlations (a) Service-Side Heat Transfer Coefficients (1) (2) Conventional Jackets with low flows [ velocity < 0.03 m/s, no phase change ] (enhanced natural convection) Conventional jackets with high flows (sensible heating/cooling) Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  56. 56. All physical properties, except µw, are evaluated at bulk temperature. Two cases arise: (i) Radial fluid inlet (ii) Tangential fluid inlet: (3) Conventional jackets with condensing heating medium (ii) [Re i > 9000] (ie no swirl) [Re i > 20000] Turbulent condensate film, see HTFS Design Report Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  57. 57. (4) Limpet coils (sensible heating/cooling) (5) Limpet coils (condensing service fluid) See HTFS Design Report (6) Spiral jackets (sensible heating/cooling) Use the same correlation as the limpet coils. (7) Immersed coils (sensible heating/cooling) where: di Dc = = pipe inside diameter coil diameter Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  58. 58. (8) Immersed coils (condensing service fluid) As for limpet coils. (b) Process-Side Heat Transfer Coefficients (1) Vessel Wall Surface 5.4.3 Thermal Shock in Glass-Lined Steel (GLS) Vessels When using a GLS vessel for heating or cooling duties, it is important to prevent thermal shock from damaging the glass lining. Table 4 shows the maximum allowable temperature difference when charging into a heated vessel. Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  59. 59. TABLE 4 CHARGING A HOT VESSEL WITH A COLD PRODUCT * use this ΔT for vessel temperatures up to 121°C. Table 5 shows the maximum allowable temperature difference when charging into a cooled vessel. TABLE 5 INJECTING A HOT FLUID INTO THE JACKET OF A COLD VESSEL * use this ΔT for vessel temperatures up to 121°C. Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  60. 60. 5.5 Flow and Circulation Details of flow patterns, velocities and local concentrations may be obtained from the CFD computer program. The following other measurements are sometimes used in mixing vessels: (a) Agitator discharge volumetric flowrate, Q p Where Flρ is a discharge coefficient for the agitator (because of entrainment the actual circulation flow will usually be much greater than, Qp). Values of Flp are given in Table 6. (b) Circulation time, tc tc is the average time interval for successive passages of a fluid element through the agitator. For a 6 bladed disc turbine (D/T = 0.3 to 0.5; Z/T = 0.3 to 0.5; H/D = 0.2; L/D = 0.25): As this is not dimensionless, V must be in m 3. For turbulent, baffled stirred vessels the following rule of thumb is frequently used: Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  61. 61. TABLE 6 TYPICAL DISCHARGE COEFFICIENTS 6 JET MIXED TANKS 6.1 Introduction Jet mixing in tanks can be used for the batch or continuous mixing of miscible low viscosity (µj < 0.1 Ns/m2) liquid systems. In tank jet mixing, a fast moving stream of liquid, the 'jet' liquid, is injected into a very slow moving, almost stationary liquid, the 'bulk' or 'tank' or 'secondary' liquid. The velocity gradient between the jet and bulk liquids creates a mixing layer at the jet bulk boundary. This mixing layer entrains bulk liquid into the jet flow. Turbulence within the jet flow then mixes the jet and bulk liquids. Side entry jets (i.e. jets through the tank wall) or axial jets (i.e. jets directed along the axis of the tank) are commonly used. Such jets are usually positioned either near the tank floor pointing towards the liquid surface or near the liquid surface pointing towards the tank floor. Swirl decreases the efficiency of mixing. Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  62. 62. 6.2 Recommended Configuration The design objective should be to produce liquid motion throughout the whole tank. The tank should be cylindrical with a vertical axis, for other shapes consult the GBHE Mixing and Agitation Manual. The liquid height, HL, to tank diameter, T, ratio should preferably be in the range: although other HL /T ratios are permissible. Depending on the tank geometry and the mixing duty, a single jet through the tank wall (a side entry jet) or a single jet on the axis of the tank (an axial jet) or multiple jets may be used. The jet can be positioned either near the tank floor pointing towards the liquid surface or near the liquid surface pointing towards the tank floor. The jet nozzle should always be submerged during the mixing operation. The side entry jet should protrude no more than 5 nozzle diameters either from the tank wall or from the tank base or liquid surface. The axial jet nozzle should be as close to the tank floor or liquid surface as possible. The side entry jet should be installed along a radius to the tank wall and the axial jet on the tank axis perpendicular to the tank floor or liquid surface. For the same mixing duty, the mixing rates achieved by axial and side entry jets are essentially the same. Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  63. 63. 6.3 Design Procedure The procedure for design for a given mixing time t99 for a given volume, V, of liquid is as follows: (a) Choose a tank diameter such that: This, of course, may not be possible if either T and/or HL are fixed by site or mechanical considerations, or if the tank already exists. The recommended tank/jet configuration, which depends on HL/T, is: The design for side entry or axial jets is detailed below. For multiple jets the tank should be considered as divided into separate volumes of H/T 1, each with their own jet, see the GBHE Mixing and Agitation Manual for more detail. (b) Jet direction A jet can be positioned pointing either upwards or downwards, see Figure 25. If the jet is pointed upwards then it may break the surface and give rise to spray. Aeration may occur. The spray may induce a build up of static charge. These problems will not occur when the jet is pointed downwards towards the base of the tank and is adequately submerged. The centre line exit velocity should be 1 to 2 m/s. When the mixing duty is merely to maintain homogeneity in a tank, the density of the jet liquid is essentially the same as the density of the bulk liquid, and stratification is not a problem. In this case the choice of jet direction is arbitrary. Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  64. 64. FIGURE 25 JET DIRECTION Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  65. 65. FIGURE 25 JET DIRECTION (Continued) Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  66. 66. (c) Position of recycle suction For an upward pointing side entry jet in a flat base tank the recycle suction should be positioned either as near as possible to the tank floor on the opposite side of the tank to the jet, or as near as possible to the liquid surface on the same side of the tank as the jet. For a dished base tank the recycle suction must be placed at, or very near, the lowest point of the base. For a downward pointing side entry jet in a flat base tank the recycle suction should be positioned either as near as possible to the liquid surface, on the opposite side of the jet, or as near to the tank floor on the same side as the jet. Again, for this type of jet in a dished base tank, the recycle suction must be placed at, or very near, the lowest point of the base. For an upward pointing axial jet in a flat base tank the recycle suction should be positioned either as near as possible to the tank floor, or as near as possible to the liquid surface in a tank with a dished base. Jet protrusion should be as small as possible in a dished base tank. For a downward pointing axial jet in a flat base tank the recycle suction should be placed either as near as possible to the liquid surface or as near as possible to the tank floor. For this type of jet in a dished base tank, the recycle suction should be placed near the liquid surface. (d) Mixing time (1) Upward pointing jets The mixing time, t99, for upward pointing jets is given by: Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  67. 67. where for both side entry and axial jets: This correlation is based on experimental work on small tanks, (T up to about 1 m) for low viscosity liquid mixing, The correlation is for flat based tanks. It applies to side entry jets with nozzles which are no more than 5 nozzle diameters either from the nearest tank wall or from the tank base and axial jets with nozzles which are close to the tank base. (2) Downward pointing jets For downward pointing jets in tanks where Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  68. 68. (3) Hemispherical based tanks The mixing time in hemispherical based tanks is less than that in flat bottomed tanks: (e) Jet diameter The jet diameter, Dj, should be chosen such that: Here, X is the jet path length, for both upward and downward side entry jets placed as recommended above: Initially choose the smallest Dj. The choice of jet velocity, vj, depends on the mixing duty being undertaken. If one liquid is being mixed with a second liquid of different density there is a danger of stratification (see GBHE Mixing and Agitation Manual) if the jet velocity is too low. Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  69. 69. (f) Number of jets As stated in (a), multiple jets should only be used for HL /T > 3.0. There is no advantage in mixing from multiple jets for the same overall flowrate in other cases. 6.4 Design for Continuous Mixing If the tank is run at a constant level, HL, and the fresh feed fed through a nozzle near the recycle line nozzle, then the tank will be well mixed if: VT is the volume of liquid in the tank and Qf is the fresh liquid feed rate. t99 is the batch mixing time calculated by the method given in 6.3. 7 TUBULAR JET FLOW MIXERS FOR MISCIBLE LIQUIDS Jet flow mixers are recommended for mixing low viscosity liquid phase systems i.e. systems where turbulent pipe flow can be achieved (Re > 5000). Mixing times from a few milliseconds on the small scale to several seconds on the large scale are possible with this type of device. In jet flow mixers a stream of liquid, the primary liquid is injected into another liquid, the secondary liquid. The velocity gradient between the jet and secondary liquids creates a turbulent mixing layer at the jet boundary. The mixing layer grows in the direction of the jet flow entraining and mixing the jet with the secondary liquid. Pressure drop at and along the pipe after the mixing point provides the energy required for mixing the two streams. Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  70. 70. There are three basic types of jet flow mixer geometries, the coaxial jet mixer, the side entry jet mixer and the impinging jet mixer, see Figure 26. In the coaxial jet mixer the jet liquid is introduced through a small diameter pipe running coaxially inside a large diameter pipe. In the side entry jet mixer the jet liquid is introduced at an angle (usually 90 degrees) into the secondary liquid stream. In the impinging jet mixer the two feed streams are fed through directly opposing branches of a tee-piece. Multiple jet flow mixers, see Figure 27, are also sometimes used. A series arrangement of mixers, Figure 28, can be used to mix more than two streams. This arrangement can also be used either when the flowrate ratio of the feed streams is very high or when the mix temperature rise due to mixing would be unacceptably high if the mixing were to be carried out in one stage. Interstage cooling can then be used. A series arrangement of mixers, Figure 28, can be used to mix more than two streams. This arrangement can also be used either when the flowrate ratio of the feed streams is very high or when the mix temperature rise due to mixing would be unacceptably high if the mixing were to be carried out in one stage. Interstage cooling can then be used. Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  71. 71. FIGURE 26 SINGLE JET MIXERS Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  72. 72. FIGURE 27 MULTIJET MIXERS Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com
  73. 73. FIGURE 28 SERIES ARRANGEMENT OF MIXERS Refinery Process Stream Purification Refinery Process Catalysts Troubleshooting Refinery Process Catalyst Start-Up / Shutdown Activation Reduction In-situ Ex-situ Sulfiding Specializing in Refinery Process Catalyst Performance Evaluation Heat & Mass Balance Analysis Catalyst Remaining Life Determination Catalyst Deactivation Assessment Catalyst Performance Characterization Refining & Gas Processing & Petrochemical Industries Catalysts / Process Technology - Hydrogen Catalysts / Process Technology – Ammonia Catalyst Process Technology - Methanol Catalysts / process Technology – Petrochemicals Specializing in the Development & Commercialization of New Technology in the Refining & Petrochemical Industries Web Site: www.GBHEnterprises.com

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