Fouling Resistances for Cooling Water

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Fouling Resistances for Cooling Water

0 INTRODUCTION/PURPOSE
1 SCOPE
2 FIELD OF APPLICATION
3 DEFINITIONS
4 GENERAL
5 COOLING WATER FOULING
6 CHROMATE SYSTEMS
6.1 General
6.2 Constraints
6.3 Requirements
6.4 Fouling resistances

7 NON-CHROMATE SYSTEMS
7.1 General
7.2 Requirements and Constraints
7.3 Fouling resistances

8 UNTREATED COOLING WATER

9 MATERIALS OTHER THAN MILD STEEL

APPENDICES

A FOULING RESISTANCES FOR COOLING WATER

B FOULING FILM THICKNESS

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Fouling Resistances for Cooling Water

  1. 1. GBH Enterprises, Ltd. Process Engineering Guide: GBHE-PEG-HEA-501 Fouling Resistances for Cooling Water 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: Fouling Resistances for Cooling Water CONTENTS SECTION 0 INTRODUCTION/PURPOSE 2 1 SCOPE 2 2 FIELD OF APPLICATION 2 3 DEFINITIONS 2 4 GENERAL 2 5 COOLING WATER FOULING 2 6 CHROMATE SYSTEMS 3 6.1 6.2 6.3 6.4 General Constraints Requirements Fouling resistances 3 3 3 3 7 NON-CHROMATE SYSTEMS 3 7.1 7.2 7.3 General Requirements and Constraints Fouling resistances 3 4 4 8 UNTREATED COOLING WATER 4 9 MATERIALS OTHER THAN MILD STEEL 4 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. APPENDICES A FOULING RESISTANCES FOR COOLING WATER 5 B FOULING FILM THICKNESS 6 DOCUMENTS REFERRED TO IN THIS PROCESS ENGINEERING GUIDE 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
  4. 4. 0 INTRODUCTION/PURPOSE The selection of fouling resistances for use in heat exchanger design is a highly subjective matter. As far as process streams are concerned reliance is generally placed on previous knowledge of the process or similar processes. However, in the case of cooling water more information is available and it is of more general applicability. 1 SCOPE This Engineering Guide outlines a standard procedure for estimating fouling resistances for cooling water, and covers both chromate and non-chromate systems. The procedure is based on experience of operating both chromate and nonchromate systems within GBH Enterprises. It is supplemented with the results from fouling test rigs at European and Gulf Coast plant locations. Design fouling resistances and temperature limitations are given for treated open evaporative cooling water systems. 2 FIELD OF APPLICATION This Guide applies to the process engineering community in GBH Enterprises worldwide. 3 DEFINITIONS For the purposes of this Guide no specific definitions apply. 4 GENERAL There are many problems in the design of water cooled heat exchangers, some of which can have a strong influence on fouling and/or corrosion; for further details, see GBHE-PEG-HEA-511 “Shell and Tube Heat Exchangers Using Cooling Water “ prior to commencement of design of such a unit. 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. The fouling resistances recommended in this Engineering Guide are, in many cases, significantly lower than values used in the past for design purposes. These values presuppose a well designed heat exchanger with adequate water velocities and good water treatment. In deciding the design fouling resistance the designer should assume that if water treatment is installed the operations are maintaining it correctly. At the commencement of a project the Process Engineer, in consultation with the appropriate Water Chemist, should confirm that operations are maintaining a suitable water treatment program. If these conditions are not met, then much higher fouling resistances may occur, and corrosion of mild steel equipment is likely. 5 COOLING WATER FOULING The principal causes of cooling water fouling are: (a) (b) (c) (d) corrosion biological growth scaling/crystallization sedimentation They can all be controlled to a greater or lesser extent by correct materials selection, good cooling water treatment and good heat exchanger design. Sedimentation fouling is strongly influenced by the water velocity; and scaling by temperature. However, provided that temperatures are kept below certain limiting values and a good program of water treatment is maintained, velocity is the only significant factor. 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. 6 CHROMATE SYSTEMS 6.1 General Provided that local environmental constraints allow their use, low chromate synergized systems are the cheapest and best available. 6.2 Constraints Chromate based treatments give very low corrosion rates on carbon steel equipment provided that water velocities are not less than 1.0 m/s. This applies equally to water in tube and water in shell exchangers. Pitting corrosion occurs at lower velocities (eg 0.5 m/s) even if the metal surface is free of all deposits. If dirt deposits do occur then pitting corrosion is likely beneath these deposits regardless of the quality of water treatment, as the deposits prevent access of the treatment chemicals to the metal surface. Velocities of less than 1.0 m/s should be avoided if at all possible; if this is not possible then a materials scientist and a Water Chemist should be consulted. A properly applied chromate treatment works equally well on unfiltered raw makeup water as it does on a potable makeup supply, providing that the heat exchangers are of sound design. See GBHE-PEG-HEA-511, “Shell and Tube Heat Exchangers Using Cooling Water”. High surface temperatures (up to 80-100°C) can be used with chromate based treatments. 6.3 Requirements The treatment is easy to monitor using simple analytical techniques and 'forgiving' with respect to minor upsets in pH value or chromate concentration. However, it is essential to have a good chlorination program in order to obtain the best results from chromate systems. Ideally, chlorination should be once a shift to give a free chlorine residual of 1 mg/l and a maximum viable bacterial count of 10,000/ml. Provided there is no significant process contamination in the cooling water circuit, then no further biocide is required. 6.4 Fouling resistances Providing that the previously mentioned criteria are observed, design fouling resistances of 0.0002 m2°C/W should be used with velocities in excess of 1.0 m/s. 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. Note: Although there is some evidence that even lower values can be used for velocities of 2 m/s or above, a constant value is recommended. The cost penalty for this is low as at this levelfouling is usually a small part of the total heat transfer resistance. 7 NON-CHROMATE SYSTEMS 7.1 General In Continental Western Europe, chromate use is, in general, prevented because of river pollution concerns. If environmental constraints prevent the use of chromate, then it is imperative that the hard won experience of continental users of non-chromate systems be applied, whether the treatment be a high pH scale inhibitor program or a low pH phosphate program. The following factors are common to all continental users who have been operating large critical single stream cooling systems on non-chromate treatment for up to 30 years. 7.2 Requirements and Constraints The make-up water to the cooling system shall be free of suspended solids and have minimum organic material to avoid annual cleaning of the exchangers. This normally necessitates pre-clarification by flocculation or lime softening, followed by filtration, or the use of high cost potable water. Raw untreated river or lake water shall not be used as make-up. Suspended materials absorb the treatment formulations making them less effective. Natural organic material acts as a nutrient for microbiological growth or as a foulant itself. The high concentration of chlorine required to combat the above may also oxidize the inhibitors and dispersants, making them non-effective. Supplementary biocides are therefore added with controlled chlorination. Between 5 and 10% of the circulation water requires to be filtered through sidestream filters in order to remove precipitates and any corrosion products. Very good analytical control is required to avoid gross fouling or corrosion, which can take place in a matter of days. Roughness of the heat transfer surface enhances fouling. Surface temperatures should not exceed 70°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
  8. 8. Water velocities below 1.0 m/s should never be used. If they are, fouling rates of 2 to 4 times those for chromate treatment are likely, and corrosion is a strong possibility. 7.3 Fouling resistances Provided that the previously mentioned criteria are met, a fouling resistance of 0.0002 m2°C/W should be used for water velocities of 2.0 m/s. For velocities of 1.0 m/s the fouling resistance is 0.0004 m2°C/W (see Appendix A). 8 UNTREATED COOLING WATER Untreated, raw water should never be used for cooling purposes unless: (a) the heat exchanger is fabricated from corrosion resistant materials (b) the water in question has a low fouling and scaling potential Materials scientist and a Water Chemists should be consulted. 9 MATERIALS OTHER THAN MILD STEEL Strictly, the fouling resistances recommended in this Engineering Guide are for mild steel equipment; lower values may be realized in practice for other materials. However, unless an adequate water velocity is maintained, problems of fouling and/or corrosion may still occur even with more corrosion resistant materials, albeit at a lower rate. 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. APPENDIX A FOULING RESISTANCES FOR COOLING WATER 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. APPENDIX B FOULING FILM THICKNESS Based on assumed thermal conductivity of 1.385 w/m°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
  11. 11. DOCUMENTS REFERRED TO IN THIS PROCESS ENGINEERING GUIDE This Process Engineering Guide makes reference to the following documents: ENGINEERING GUIDES GBHE-PEG-HEA-511 Shell and Tube Heat Exchangers Using Cooling Water (referred to in Clause 4 and 6.2). 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. 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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