Dosing Presentation 2012


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Introduction to Chemical Dosing Systems

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Dosing Presentation 2012

  2. 2. WHAT IS CHEMICALDOSING Chemical conditioning of feed water / steam condensate cycle, is essential to prevent corrosion and scale formation Dosing can be of two types : H.P. (High Pressure) L.P. (Low Pressure) PSI ENGG SYSTEMS P.LTD.
  3. 3. WHAT IS CHEMICALDOSING Corrosion: Corrosive components, especially O2 and CO2 have to be removed, usually by use of a deaerator. Remnants can be removed chemically, by use of oxygen scavenger. Feedwater has to be alkalized to a pH of 9 or higher, to reduce oxidation and to support the forming of a stable layer of magnetite on the water-side surface of the boiler, protecting the material underneath from further corrosion. This is usually done by dosing alkalies into the feedwater, like sodium hydroxide (caustic soda) or volatile ammonia. PSI ENGG SYSTEMS P.LTD.
  4. 4. WHAT IS CHEMICALDOSING Treating the boiler feed water The boiler feed water treatment is normally done with the following chemicals:  Hardness stabilisers  Deflocculating agents  Corrosion inhibitors  Oxygen binding agents (e.g. hydrazine)  pH value regulation (caustic soda, ammonia)  Defoaming agents Dosing of these chemicals into the tank of boiler feed water is done using dosing systems PSI ENGG SYSTEMS P.LTD.
  5. 5. WHAT IS CHEMICALDOSING H.P. DOSING Corrosion rate of M.S. surface is lowest, when pH is between 9 - 10. Dosing is therefore done , to maintain pH & reduce scaling Generally solution dosed into drum under full boiler pressure PSI ENGG SYSTEMS P.LTD.
  6. 6. WHAT IS CHEMICALDOSING L.P. DOSING Dissolved oxygen in feed water causes serious corrosion. Hence "oxygen scavengers" or "de-oxygenators" are dosed into feedwater. Dosing done into feed water stream, either at BFP suction, or at deareator, at low pressures. Other chemicals may be also added for pH adjustment of DM water PSI ENGG SYSTEMS P.LTD.
  7. 7. WHAT IS CHEMICALDOSING DOSING CHEMICALS  H.P. DOSING  Phospate solution (combination of di-sodium and tr-sodium phospate) is generally used, in concentrations from 2.5 % to 7.5 %.  Exact dosage rate depends on pH variation of water in drum.  It prevents scale formation from low remaining levels of hardness which may have escaped treatment.  Sodium phosphate causes the hardness to precipitate to the bottom of the boiler where it can be blown down. PSI ENGG SYSTEMS P.LTD.
  8. 8. WHAT IS CHEMICALDOSING DOSING CHEMICALS - L.P. DOSING Hydrazine Hydrate solution, in concentrations of about 0.10 % is used for oxygen scavenging purposes. Sodium Sulphite solution, is also used as oxygen scavenger. Ammonia solution (about 1 - 2 %) is also used, for pH control of feedwater. Similarly Morpholine is also used. Caustic Soda solution is also used, for pH control of feed water. Other proprietary chemicals are also available for same purposes. PSI ENGG SYSTEMS P.LTD.
  9. 9. WHAT IS CHEMICALDOSING Further detail on this complicated subject of water treatment, is available from water treatment specialists This is very much a matter for expert advice and professional analysis . PSI ENGG SYSTEMS P.LTD.
  10. 10. Dosing Systems - Basics A metering (dosing) pump is required to deliver a liquid or solution at specified rate of flow . The logging and control of flow rates & total quantity delivered calls for Dosing Systems (also known as Chemical Injection Skids). PSI ENGG SYSTEMS P.LTD.
  11. 11. Dosing Systems – Basics -contd These skids typically consist of:  Storage tanks or solution preparation tanks, with  Mixers (agitators)  Level Gauges  Interconnecting Piping  Pipe Fittings  Valves  Instrumentation for flow / pressure  Control Panels/ Control Systems PSI ENGG SYSTEMS P.LTD.
  12. 12. Dosing Systems – Basics -contd The total assembly is commonly referred to as DOSING SYSTEM, or, Chemical Injection Skid. A well-designed system should be:  very compact  save space and  be convenient for plant installation as well as plant operation  Advanced instrumentation features can be incorporated into the systems, for compete auto- control & data logging, through plant interface PSI ENGG SYSTEMS P.LTD.
  13. 13. Dosing Systems – Basics -contdConsiderable design and detailed engineering efforts are required for designing individual components of the skid, and in integrating the components into making a compact and efficient system. PSI ENGG SYSTEMS P.LTD.
  15. 15. Dosing Systems – UsageAreasDosing Skids are used by a wide cross section of Industry: Oil and Natural Gas Exploration & Refining Iron and Steel Chemicals processing industries Pulp & Paper manufacture Thermal Power Water & Effluent Treatment Food & Pharmaceutical industries Personal care products Machine building Industry Semiconductor manufacturing PSI ENGG SYSTEMS P.LTD.
  16. 16. Dosing Systems –ApplicationsTypical applications include: Inhibitor Dosing (Cooling water treatment) Phosphate Dosing/ Hydrazine Dosing (Boiler Feed Water treatment) Dye Dosing (Petroleum Industry) Lubrication of Rolling Mills (Steel Industry) Reagent Dosing (Pharma industry) Dosing paper chemicals (Paper Industry) PSI ENGG SYSTEMS P.LTD.
  17. 17. So what exactly is a dosingsystem? First we see some dosing pump basics…… PSI ENGG SYSTEMS P.LTD.
  18. 18. Dosing Pump basics…. The metering pump is a positive displacement chemical dosing device, with the ability to vary capacity, manually or automatically, as process conditions require. It features a high level of repetitive accuracy and is capable of pumping a wide range of chemicals including acids, bases, corrosive or viscous liquids and slurries. PSI ENGG SYSTEMS P.LTD.
  19. 19. Dosing Pump basics…. Metering pumps are generally used in applications where one or more of the following conditions exist:  Low flow rates in ml/hr or LPH are required  High system pressure exists  High accuracy feed rate is demanded  Dosing is controlled by manual control, computer, microprocessor, DCS, PLC, or flow proportioning  Corrosive, hazardous, or high temperature fluids are handled PSI ENGG SYSTEMS P.LTD.
  20. 20. Dosing Pump basics…. There are 2 main types of dosing pumps:  Plunger Type: The pumping action is developed by a reciprocating piston which is in direct contact with the process fluid,  Diaphragm Type: Piston is shielded from the fluid by a diaphragm. Diaphragms are actuated by hydraulic fluid between the piston and the diaphragm. PSI ENGG SYSTEMS P.LTD.
  21. 21. Plunger PumpHydraulic Diaphragm Pump PSI ENGG SYSTEMS P.LTD.
  22. 22. Types of Dosing PumpsDiaphragm Pump Plunger Pump PSI ENGG SYSTEMS P.LTD.
  23. 23. Dosing Pump characteristics.. The pumping action is developed by a reciprocating piston. This reciprocating motion develops a flow sine wave. PSI ENGG SYSTEMS P.LTD.
  24. 24. Dosing Pump characteristics.. Unlike centrifugal pumps, flow rate is not greatly affected by changes in discharge pressure. PSI ENGG SYSTEMS P.LTD.
  25. 25. Dosing Pump Drivemechanism The Drive mechanism translates the rotary motion of the driver into reciprocating movement. Industrial duty pumps will submerge this portion of the pump in an oil bath to assure reliability during continuous operation. PSI ENGG SYSTEMS P.LTD.
  26. 26. Flow Adjustment Pump flow rate is adjustable by varying stroke length Most metering pumps are supplied with a micrometer screw adjustment similar to the one shown here. The micrometer can also be replaced by an electronic or pneumatic actuator to adjust pump flow rate in response to a process signal. PSI ENGG SYSTEMS P.LTD.
  27. 27. Pump Drivers & Adjustment The pump is usually driven by an AC (constant speed) motor. Flow control (in manual mode) is done by rotating stroke adjuster knob, which varies stroke length, from 0 – 100% Flow control (in auto mode) is done by use of stepper motor to rotate stroke adjuster PSI ENGG SYSTEMS P.LTD.
  28. 28. Dosing Pump characteristics.. The metering pump flow vs. Stroke characteristic curve is linear. By measuring flow at 2 stroke settings, plotting both points and drawing a straight line through them, other flow rates vs. Stroke can be accurately predicted. The steady state accuracy of a correctly installed metering pump is generally +/- 1.0% or better. PSI ENGG SYSTEMS P.LTD.
  29. 29. Dosing Pump characteristics.. Although a metering pump can generally be adjusted to pump at any flow rate between 0 and its maximum capacity, its accuracy is measured over a range determined by the pumps turndown ratio. Most metering pumps have a turndown ratio of 10:1,which simply means that the pump is within its accuracy rating anywhere between 10% and 100% of capacity. PSI ENGG SYSTEMS P.LTD.
  30. 30. Dosing Pump characteristics.. •Pump stroking speeds can vary from 75 strokes/min to 200 strokes/min •Higher stroke speeds reduce pump size & give higher mechanical efficiency •Lower stroke speeds only serve to increase pump size and hence cost •Newer gland packing materials, and improved designs (such as “floating cross-head” construction), lead to near-zero wear and consequent leakage at higher stroking speeds PSI ENGG SYSTEMS P.LTD.
  31. 31. Dosing Pump liquid end.. The liquid end design and materials of construction are determined by the service conditions, and the nature of the fluid to be handled. Temperature, flow rate, fluid viscosity, corrosiveness and other factors are considered PSI ENGG SYSTEMS P.LTD.
  32. 32. Dosing System basics… In a typical boiler feed water dosing system:  The HP Dosing system doses direct into boiler drum, under high pressure.  The LP Dosing system doses into the boiler feed water pump suction line, or, de-aerator inlet line, under low pressure PSI ENGG SYSTEMS P.LTD.
  34. 34. Some boiler installations need 3-pump HP dosing systems, asshown above. Note the dissolving basket fitted in the dosing tank,and the top-mounted level switch (to stop pump on low level).
  35. 35. The General Arrangementdrawing (known as GADrawing) for a typical 2-pumpboiler feed water dosingsystem is shown on the nextslide….. PSI ENGG SYSTEMS P.LTD.
  36. 36. Dosing System - Components Typical components of a dosing system:  Dosing Pumps PSI ENGG SYSTEMS P.LTD.
  37. 37. Dosing System - Components Typical components of a dosing system:  Tanks PSI ENGG SYSTEMS P.LTD.
  38. 38. Dosing System - Components Typical components of a dosing system:  Valves PSI ENGG SYSTEMS P.LTD.
  39. 39. Dosing System - Components Typical components of a dosing system:  Level gauge for tank PSI ENGG SYSTEMS P.LTD.
  40. 40. Dosing System - Components Typical components of a dosing system:  Pressure gauge: PSI ENGG SYSTEMS P.LTD.
  41. 41. Dosing System - Components Typical components of a dosing system:  Pressure Relief Valve: PSI ENGG SYSTEMS P.LTD.
  42. 42. Dosing System - Components Typical components of a dosing system:  Pulsation dampener  Calibration Column PSI ENGG SYSTEMS P.LTD.
  45. 45. Manual & Auto-ControlSystems What we have seen till now are manually operated dosing systems, utilizing standard mechanical dosing pumps. These will satisfy the needs of most steady- state operations Auto-controlled systems are responsive to changes in process conditions, requiring frequent changes in dosing conditions, done automatically PSI ENGG SYSTEMS P.LTD.
  46. 46. Auto-Controlled Dosing Auto-control dosing systems need external logic controllers, which take signal from process sensors, and adjust dosing according to pre-determined values. PSI ENGG SYSTEMS P.LTD.
  47. 47. Standard Controllers used in Auto-Dosing Systems Conductivity & pH controllers PSI ENGG SYSTEMS P.LTD.
  48. 48. Auto-controlled Dosing A classic example is a modern boiler system, where the following process parameter changes affect dosing rates: PSI ENGG SYSTEMS P.LTD.
  49. 49. Auto-controlled Dosing - types Flow-proportional method:  Uses an instrument signal to adjust dosing rate, based on actual flow of water being treated  Instrument signal is generated from a flow- measuring device  Commonly used in boiler plants and cooling water treatment plants PSI ENGG SYSTEMS P.LTD.
  50. 50. Auto-controlled Dosing - types Parameter Measurement method:  Measurement of several parameters is taken from the process  These are analyzed to make the dosing decisions  Dosing decisions made by the central processor, based on comparison of readings with programmed control bands PSI ENGG SYSTEMS P.LTD.
  51. 51. Auto-controlled Dosing - types Parameter Measurement method:  In a boiler system, parameters such as dissolved oxygen, pH, and conductivity are continuously monitored, for dosing decisions  This method closely monitors multiple variables, such as flow rate, dissolved oxygen content, and adjusts dosing rate accordingly PSI ENGG SYSTEMS P.LTD.
  52. 52. Parametric Dosing - examples PSI ENGG SYSTEMS P.LTD.
  54. 54. Our Chemical Dosing range We focus on packaged skid-mounted dosing systems for cooling water & boiler feed water treatment. This is our core business We have been in this business for over 30 years A typical system includes metering pumps, control instrumentation, and all interconnectingENGG SYSTEMS P.LTD. PSI pipework.
  55. 55. Some DosingSystems made byus… PSI ENGG SYSTEMS P.LTD.
  56. 56. Dosing Systems(Chemical Injection Systems)(Chemical feed systems)Application areas: Oilfields Boiler Dosing Effluent treatment Petroleum industry Paper Industry Heat treatment furnaces
  57. 57. HP Dosing system,with 2 pumps& local control panelUser:Jindal Stainless
  58. 58. LP Dosing system,with 2 pumps local control panel self-cleaning filters(16 lph 5 bar)EPC Contractor:Alstom Projects IndiaLtd.User:Bokaro Power
  59. 59. Some details of HP Dosing system
  60. 60. LP Dosing system, cap.50 lph / 45 barClient: BHEL – PEM DelhiUser: NTPC Aravalli
  61. 61. LP Dosing system, cap.50 lph / 45 barClient: BHEL – PEM DelhiUser: Pipavav Power
  62. 62. Control Panel forLP Dosing systemClient: BHEL – PEMDelhiUser: PipavavPower
  63. 63. Ammonia Dosing system, with 2 tanks 6000 lit. cap., & contDosing Pump cap. 50 lph 45 barClient: BHEL Delhi. User: Kalpakkam Nuclear Power Plant
  64. 64. Anti-ScalantDosing system,(CW Dosing)with tank 5000 lit.capacityDosing Pumpcap. 250 lph 2barClient: BGREnergy.User: AP GencoKothagudem
  65. 65. IN CONCLUSION…. We focus on high reliability, high quality, water treatment dosing equipment Instead of trying to win your business by being the cheapest, we focus on giving you the best possible equipment that your budget can bear. PSI ENGG SYSTEMS P.LTD.
  66. 66. THANK YOU Dosing is an exhaustive subject We have given a brief overview of the subject We will be glad to clarify any specific queries We can custom-design systems for specific applications PSI ENGG SYSTEMS P.LTD.