Boiler chemical cleaning_


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Boiler chemical cleaning_

  1. 1. Advance Techniques in Boiler Chemical CleaningChemical Cleaning of Boilers with EDTA By: HC Madan SS Chauhan Dhruv Garg Bharat Heavy Electricals Limited 1 Power Sector: Technical Services
  2. 2. Agenda1 Need for Chemical Cleaning of Boilers2 What is EDTA Cleaning?3 BHEL’s Experience with EDTA Cleaning4 EDTA Cleaning Process5 EDTA vis-à-vis HCl Cleaning– Advantages6 Conclusion 2 Bharat Heavy Electricals Limited Power Sector: Technical Services
  3. 3. Need for Chemical Cleaning of Boilers Bharat Heavy Electricals Limited Power Sector: Technical Services
  4. 4. Need for Chemical Cleaning of Boilers? Pre-operative • Maintaining steam quality at the turbine inlet. • Minimizing corrosion of the metal surface of boiler. Post-operative • Improving heat transfer in the system. • Enhancing efficiency of the power plant. • Minimizing under-deposit corrosion of the metal surface of boiler. • Minimizing plant outage due to boiler tube failures. Bharat Heavy Electricals Limited 4 Power Sector: Technical Services
  5. 5. Need for Chemical Cleaning of Boilers? Pre-operative Chemical Cleaning System • Evaporator System Economizer Downcomers Bottom Ring Headers Water Walls Boiler Drum (Only water touched surface) Bharat Heavy Electricals Limited 5 Power Sector: Technical Services
  6. 6. Need for Chemical Cleaning of Boilers? Iron metal surface with corrosion layers Bharat Heavy Electricals Limited 6 Power Sector: Technical Services
  7. 7. What is EDTA Cleaning?Bharat Heavy Electricals Limited 7Power Sector: Technical Services
  8. 8. What is EDTA?EDTA or Ethylene Di-amine Tetra acetic Acid is a strongchelating agent having ability to form stable complexeswith transition metal ions present in boiler such as of Ironand Copper etc. Bharat Heavy Electricals Limited 8 Power Sector: Technical Services
  9. 9. EDTA and EDTA-Fe Complex StructureEDTA EDTA-Fe Complex Bharat Heavy Electricals Limited 9 Power Sector: Technical Services
  10. 10. EDTA Pickling & its Reaction Bharat Heavy Electricals Limited 10 Power Sector: Technical Services
  11. 11. Magnetite Layer• A protective layer of Magnetite (Fe3O4) is formed on the water touched metal surfaces in the steam generator.• Magnetite layer acts as a coherent media that stops further corrosion of the base metal.• Magnetite is a combination of FeO and Fe2O3. Bharat Heavy Electricals Limited 11 Power Sector: Technical Services
  12. 12. BHEL’s Experience with EDTA Cleaning Bharat Heavy Electricals Limited 12 Power Sector: Technical Services
  13. 13. EDTA Process - World Scenario• EDTA process is at present executed by : Dow chemical Co – USA Halliburton Services – UK Alstom, MHI, & Siemens• Process details & chemical formulations especially inhibitor for the process are being held under proprietary rights by these companies.Bharat Heavy Electricals Limited 13Power Sector: Technical Services
  14. 14. EDTA Process - World Scenario• BHEL has joined the select band of few companies in the world to possess & establish this advanced cleaning process.• BHEL has marked the giant leap by developing its own inhibitors and chemical formulations for EDTA Cleaning Process.Bharat Heavy Electricals Limited 14Power Sector: Technical Services
  15. 15. Inhibitors• EDTA Process developed by R&D Centre of BHEL-Trichy; involved in-house development of inhibitors: BHEL MAX BHEL SOL• These inhibitors are patented by BHEL: Patent Nos.: 177 & 332 / 2004• These inhibitors act by forming an invariable layer between the base metal surface and the chemical solution as the deposits are removed.Bharat Heavy Electricals Limited 15Power Sector: Technical Services
  16. 16. Experience with EDTA Cleaning• EDTA Cleaning Process was introduced in BHEL in 2003-2004.• Chemical cleaning of boilers with EDTA completed in 43 projects of different ratings, till Feb 2009. Year No. of Projects 2003 – 2004 1 2004 – 2005 3 2005 – 2006 3 2006 – 2007 7 2007 - 2008 13 2008 - 2009 16 Total 43 Bharat Heavy Electricals Limited 16 Power Sector: Technical Services
  17. 17. Experience with EDTA Cleaning Rating wise – 2003-04 to 2008-09 (upto Feb 2009) Rating No. of Projects 500 MW 4 250 MW 22 210 MW 9 75 / 120 / 125 MW 8 Total 43Bharat Heavy Electricals Limited 17Power Sector: Technical Services
  18. 18. Exceptions during reigns of EDTA Process Besides EDTA Cleaning, BHEL has also conducted HCl cleaning at following 7 projects during the same period. Rihand # 4 (500 MW) Vindhyachal # 9 (500 MW) Vindhyachal # 10 (500 MW) Sipat # 4 (500 MW) Sipat # 5 (500 MW) Kahalgaon # 6 (500 MW) Kahalgaon # 7 (500 MW) Bharat Heavy Electricals Limited 18 Power Sector: Technical Services
  19. 19. Projects expected in 2009-10 Rating No. of Projects 500 MW 9 250 MW 11 210 MW 1 125 MW 6 Total 27Bharat Heavy Electricals Limited 19Power Sector: Technical Services
  20. 20. EDTA Cleaning ProcessBharat Heavy Electricals Limited 20Power Sector: Technical Services
  21. 21. EDTA Cleaning Process Alkali Flushing Alkali Flushing Hot Water Flushing Cold Water Rinse EDTA Cleaning EDTA Pickling & Passivation Treated DM Water Rinsing Inspection SH Back FlushingBharat Heavy Electricals Limited 21Power Sector: Technical Services
  22. 22. EDTA Cleaning Process Alkali Flushing - Purpose Alkali Flushing – Removes polar organic materials such as oil, grease etc. from the metal surface. – Alkali reacts with polar organic materials to form soluble glycerols and salts. – Loose deposits, dust etc. are also removed. – TSP and DSP is used as alkali. Hot Water Flushing Cold Water RinseBharat Heavy Electricals Limited 22Power Sector: Technical Services
  23. 23. EDTA Cleaning ProcessAlkali Flushing- Procedure Alkali Flushing Alkali solution made by adding TSP(0.1%) & DSP (0.05%) with DM water. Solution is filled into boiler through bottom ring header & economizer drains up to NWL. Boiler is fired. Water temperature is raised to 140ºC and boiler tripped. Solution is allowed to cool till 95ºC and then drained.Bharat Heavy Electricals Limited 23Power Sector: Technical Services
  24. 24. EDTA Cleaning ProcessAlkali Flushing- Procedure (Contd..) Hot Water Flushing System is filled with DM water and temperature raised to 1400C and allowed to cool to 950C and drained subsequently. Cold Water Rinse System is filled with DM water and drained. The process is repeated till phosphate level is less than 10 ppm.Bharat Heavy Electricals Limited 24Power Sector: Technical Services
  25. 25. EDTA Cleaning ProcessPreparing EDTA SolutionEDTA solution is prepared for total boiler volume bymixing.1.EDTA Ammoniated (40%) : 4%2.BHEL MAX (inhibitor) : 0.15-0.2% w/v3.BHEL SOL (inhibitor) : 0.15-0.2% v/v4.Hydrazine hydrate : 1000 ppm5.Ammonia : for setting pH as 9.5-9.8Bharat Heavy Electricals Limited 25Power Sector: Technical Services
  26. 26. EDTA Cleaning ProcessEDTA Pickling and Passivation The system is filled with EDTA solution upto drum NWL The boiler is lighted up and temperature raised to 1400C and maintained for 4 hours and sample solution checked for iron, pH and EDTA concentration every ½ an hour. The boiler is tripped on achieving 3 consecutive readings of iron concentration. The solution is allowed to cool till 950C and drained.Bharat Heavy Electricals Limited 26Power Sector: Technical Services
  27. 27. EDTA Cleaning Process Treated DM Water Rinsing A solution of hydrazine (0.01-0.02%) and ammonia with DM water is prepared (pH 9.5 – 9.8) and the system is filled with this solution. Boiler is fired and temperature raised to 120⁰C. Boiler is tripped and allowed to cool. When the temperature comes down to 95⁰C, the solution is drained.Bharat Heavy Electricals Limited 27Power Sector: Technical Services
  28. 28. EDTA Cleaning Process Inspection Boiler drum Bottom ring headers Water wall tubes Super heater back flushing Super heater is filled with a solution of hydrazine (N2H4 >50 ppm) & Ammonia (pH>9.5) in DM water through SH drain header. When the solution comes through SH openings in the drum, the back flushing is continued for 10-30 minutes and drained.Bharat Heavy Electricals Limited 28Power Sector: Technical Services
  29. 29. EDTA Cleaning ProcessEDTA Cleaning ResultsBharat Heavy Electricals Limited 29Power Sector: Technical Services
  30. 30. EDTA Cleaning ProcessEDTA Cleaning ResultsBharat Heavy Electricals Limited 30Power Sector: Technical Services
  31. 31. EDTA Cleaning Process EDTA Cleaning ResultsBharat Heavy Electricals Limited 31Power Sector: Technical Services
  32. 32. EDTA vis-à-vis HCl Cleaning-Advantages Bharat Heavy Electricals Limited 32 Power Sector: Technical Services
  33. 33. EDTA vis-à-vis HCl Cleaning–Advantages HCl Cleaning Process • Preliminary Cleaning – Alkali Cleaning Hot Water Flushing Alkali Boil-out Cold Water Rinsing • Acid Cleaning HCl Cleaning DM Water Rinsing Citric Acid Rinsing DM Water Rinsing Neutralization Passivation (1st and 2nd Stage) • Inspection Bharat Heavy Electricals Limited 33 Power Sector: Technical Services
  34. 34. EDTA vis-à-vis HCl Cleaning–AdvantagesDisadvantages of HCl Cleaning Process• Lot of temporary piping required.• More number of chemicals (12 Nos.) required.• Nitrogen gas in huge volume & its piping system required.• Auxiliary steam required in huge quantity, which is a problem in green field projects.• DM water and fuel consumption is very high.• Process handling is difficult and hazardous due to corrosive nature of chemicals.• Large cycle time (17 days).• Effluent treatment & disposal requires huge investments. Bharat Heavy Electricals Limited 34 Power Sector: Technical Services
  35. 35. EDTA vis-à-vis HCl Cleaning– Advantages EDTA Cleaning– Advantages • Technological advantages EDTA is a strong chelating agent with transition metal ions and hence has an efficient action as metal remover. • Process advantages Use of Nitrogen & its system is eliminated. Auxiliary steam is not required at all. DM water and fuel consumption is less. Shorter cycle time (5 days). Bharat Heavy Electricals Limited 35 Power Sector: Technical Services
  36. 36. EDTA vis-à-vis HCl Cleaning– AdvantagesEDTA Cleaning– Advantages• Process advantages (contd.) Less temporary piping required Less number of chemicals required. Ease of handling. Effluent treatment easy.• Other advantages Economical. Bharat Heavy Electricals Limited 36 Power Sector: Technical Services
  37. 37. ConclusionBharat Heavy Electricals Limited 37Power Sector: Technical Services
  38. 38. Conclusion• EDTA cleaning process ensures efficient cleaning and passivation of boiler internal surfaces.• Inhibitor for EDTA cleaning process being used has been developed by BHEL. Inhibitors are patented as – “BHEL MAX” and “BHEL SOL”.• EDTA Cleaning has obvious advantages over conventional HCl Cleaning with minimum effect on the base metal surface. Bharat Heavy Electricals Limited 38 Power Sector: Technical Services
  39. 39. Thank youBharat Heavy Electricals Limited 39Power Sector: Technical Services