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PMFR: Abnormal plume emission at DS column

PMFR: Abnormal plume emission at DS column

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PMFR: Abnormal plume emission at DS column

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  1. PMFR: Abnormal plume emission at DS column

  2. Contents • Background and Problem • Chronicle Incidents • Possible Causes and Investigation • Immediate Correction • Countermeasure and Further Action

  3. Background and Problem Found abnormal plume condition at DS column since 04:50 of 16 Sep’12.

  4. Background and Problem Consequences from this incident • Total downtime for LC unit = 47 hours. • LC production shortage = 1,504 tons. • LC loss to residue during start-up. • T-NH3 and T-S/LC loss to AS unit from higher acid content, bad HX quality and SA synthesis.

  5. Background and Problem Steam Found high plume emission during 4:50-16:00 of 16 Sep’12 Vent gas Normal control Temp. ; -5 ℃ ORP ; 300 mV pH ; 2.4 1210-V10 1210-C2 1210-V12 1210-E9 SO2 gas 1210-E7 1210-S2 1210-E8 1210-V8 Si liquid Temp. ; -1 ℃ 1210-E11 Nd liquid CW 1210-E10 Si liquid to Nd col. HX to Oxmation Si liquid 1210-V9 1210-V15

  6. Chronicle Incidents (1) 16 Sep’12 • 04:50 Found abnormal plume at DS column, decrease load at DS column to 76%. • 10:15 Decrease load of DS column to 40% and Ammonia oxidizers to 50% (minimum). Still found appearance of plume. • 13:40 Fill 25%AW to DS column to control reaction in the column. • 16:10 Shut down 1200 and 4150 unit due to ND and Si inventory high. • 17:30 Found 8.45wt% of free SO3 in 4140-C5, that should be a root cause of plume. • 22:00 Start up DS column after INST calibrated the analyzer and replaced solution in 4140-C5 with 98wt% SA. Still found appearance of plume.

  7. Chronicle Incidents (2) 17 Sep’12 • 01:20 Reduce load of 1300 unit to 56% to prevent HX shortage. • 05:20Shut down DS column again due to unable to control plume emission (Suspected NTS or acid is still remained in the column). • 07:00 Start emptying DS column and prepare for re-start up. (HX inventory 1600 tons) • 13:00Re-start up DS column at 20% load, but still found high plume emission • 21:00 Shut down DS column for washing

  8. Chronicle Incidents (3) 18 Sep’12 • 14:30 Finish washing DS column. • 16:00Open manhole for inspection. • 19:00 Close manhole and prepare for re-start up. • 22:00Still found high plume emission after re-started up, switch SO2 gas to Si column, also found plume emission at Si column. 19 Sep’12 • 03:00 Shut down 1300 unit due to HX shortage. • 05:30 Shut down Si column. • 13:00 Confirm condition of 4140-C5 and SOx at Si column (Start Si column for 2 hours). • 20:30Re-start up with very low operation load (~5-10%), plume condition decrease after 10 hours operation.

  9. Possible Causes Abnormal plume at first sight • Bad quality of ND/Si solution • Abnormal SO2 gas feed to DS column Problem in re-starting up (1st time) • Abnormal of solution in DS column Problem in re-starting up (2nd time) • NTS crystal remained in the column Plume emission during post-washing DS column re-started up • Misoperation from start-up procedure • SO3 contaminated in SO2 pipeline

  10. Possible Causes – Quality of ND/Si Solution ND and Si solution quality is still in control range.

  11. Possible Causes – SO2 Gas (1) Normal operation Rxn 1 : SO3 + H2O ==> 98.5 % H2SO4 + Heat Normally open by 10-30% to maintain acid conc 98.5 wt% in column Maintain temp about 95-98 deg C by CW circulation cooler

  12. Possible Causes – SO2 Gas (2) During plume emission Free SO3 goes with SO2 to 1200 unit Found analyzer value is still maintained without low conc. acid feed Valve has closed since 21:30 Found temp decreasing from 99 to 95 deg C during 23:00-02:00 Found SO3 accumulation in tank (8.45 wt%) from normal acid content 98.5 wt% on 16 Sep’12 15:00

  13. Possible Causes – SO2 Gas (3) SO2 Scrubber (4140-C5) Found column temp. decrease after stopped low conc. acid feed Decrease load Stop receive low conc. acid from 4140-C1 (Suspected error from analyzer) Found free SO3 increase from 0 to 8.5 %wtin pump tank.

  14. Possible Causes – SO2 Gas (4) Control parameters of DS column • SO2 gas feed is constant and related to operation load. • ND liquid feed is to control pH of DS solution ~2.4. • Control Si liquid feed is to control NH3/NIT ratio ~1 (ORP ~300 mV). AIC ND liquid pH DS column SO2 gas FIC ORP Si liquid AIC Main Reaction: SO2 + NH4NO2 + NH4HSO3  DS + H2O

  15. Possible Causes – SO2 Gas (5) Steam Inside solution becomes clear Vent gas 1210-V10 1210-C2 1210-V12 1210-E9 SO2 gas 1210-E7 1210-S2 1210-E8 1210-V8 Si liquid Temp. ; -1 ℃ 1210-E11 Nd liquid CW 1210-E10 Si liquid to Nd col. HX to Oxmation Si liquid Bottom temp. increases due to more heat generation from decomposition 1210-V9 1210-V15

  16. Possible Causes – SO2 Gas (6) Effect of SO3 gas to reaction in DS column • SO2 and F-NH3 remains in the column and goes out as white plume after reaction between NIT and SO3 occurred. • NH3/NIT ratio becomes higher, ORP drops. SO3 Main Reaction: SO2 + NH4NO2 + NH4HSO3  DS + H2O White Plume SO2 F-NH3

  17. Possible Causes – SO2 Gas (7) • Side-Reaction in Ds Column. • NH3 (HSi) / NH4NO2 (ANI) [mol. Ratio] > 1 : • HON(SO3NH4)2 + NH4HSO3 →N(SO3NH4)3 + H2O • (Ds) (HSi) (NTS)   ←  Color is clear. • N(SO3NH4)3 + H2O → HN(SO3NH4)2 + 1/2H2SO4+ 1/2(NH4)2SO4 • (NTS)(Imido-sulfonate)←  Color is clear. • NH3 (HSi) / NH4NO2(ANI) [mol. Ratio] < 1 : • HON(SO3NH4)2 + NH4NO2 → ON.ON(SO3NH4)2 + NH4OH • (Ds) (ANI) (Ortho-nitrosohydoxylamine Ds)←  brown. • ON.ON(SO3NH4)2 → NO(SO3NH4)2 + NO • (Ortho-nitrosohydoroxylamne Ds) (Nitrosohydoroxylamne Ds) ← Color is purple. Found more NTS , SA and AS generation and H2SO4 occurred when pH and ORP dropped

  18. Possible Causes – SO2 Gas (8) Decomposition of NTS and NIT Side reaction ; - NOH(SO3NH4)2 + (NH4)HSO3→ N(SO3NH4)3 + H2O ( Dissulfonate ; DS ) (Ammonium bi-sulfite ; HSi) ( nitrilo-trisulfamic acid ; NTS) - N(SO3NH4)3 + H2O → NH(SO3 NH4) +0.5H2SO4 + (NH4)2SO4 - NH(SO3 NH4) + H2O → NH2SO3 H+ (NH4)2SO4 - NH2SO3 H + H2O → 0.5 H2SO4+ 0.5(NH4)2SO4 - NH4NO2+ H2SO4→ 2HNO2 + (NH4)2SO4 (Ammonium Nitrite ; NIT ) - 2HNO2 → NO+ NO2+ H2O More acid coming with SO3 from 4140-C5 and NTS generation White plume emission

  19. Possible Causes – SO2 Gas (9) DS column condition before plume occurred High Plume occurred after ORP dropped Found temp. increases (Suspected SO3 is coming)

  20. Intermediate Correction – Plume at First Sight • Decrease operation load of DS column (SO2 feed) to 76%. • Adjust ORP by increasing Si feed. • Fill 25%AW from head tank around 1-2 m3 until pH = 9. From above activities, we still found high plume emission. Then, shut down 1200 unit after 1210-V14 reached to high level.

  21. Countermeasure – Plume at First Sight Re-calibrate analyzer by INST • Re-calibrate analyzer and replace solution in 4140-V5 with low conc. acid. • Re-start up after concentration was confirmed. • Still found plume emission. Replace solution in tank with low concentration acid from 4140-C1

  22. Possible Causes Abnormal plume at first sight • Bad quality of ND/Si solution • Abnormal SO2 gas feed to DS column Problem in re-starting up (1st time) • Abnormal of solution in DS column Problem in re-starting up (2nd time) • NTS crystal remained in the column Plume emission during post-washing DS column re-started up • Misoperation from start-up procedure • SO3 contaminated in SO2 pipeline

  23. Possible Causes – Abnormal of DS Solution Steam Vent gas 1210-V10 Still found plume emission after re-start up for 7 hrs. 1210-C2 1210-V12 1210-E9 SO2 gas 1210-E7 1210-S2 1210-E8 1210-V8 Si liquid Temp. ; -1 ℃ 1210-E11 Nd liquid CW 1210-E10 Si liquid to Nd col. HX to Oxmation Suspected that solution inside the column was abnormal Si liquid 1210-V9 1210-V15

  24. Countermeasure – Abnormal of DS Solution Steam Vent gas 1210-V10 1210-C2 1210-V12 1210-E9 SO2 gas 1210-E7 1210-S2 1210-E8 1210-V8 Si liquid Temp. ; -1 ℃ 1210-E11 Nd liquid CW 1210-E10 Si liquid to Nd col. HX to Oxmation Si liquid Shut down DS column and empty liquid, 1210-V9 1210-V15

  25. Possible Causes Abnormal plume at first sight • Bad quality of ND/Si solution • Abnormal SO2 gas feed to DS column Problem in re-starting up (1st time) • Abnormal of solution in DS column Problem in re-starting up (2ndtime) • NTS crystal remained in the column Plume emission during post-washing DS column re-started up • Misoperation from start-up procedure • SO3 contaminated in SO2 pipeline

  26. Possible Causes – NTS Crystal Remained Steam Re-start up with 20% load and maintain condition Suspected that NTS crystal remained in the column Vent gas 1210-V10 Still found plume emission after re-start up for 7 hrs. 1210-C2 1210-V12 1210-E9 SO2 gas 1210-E7 1210-S2 1210-E8 1210-V8 Si liquid Temp. ; -1 ℃ 1210-E11 Nd liquid CW 1210-E10 Si liquid to Nd col. HX to Oxmation Si liquid 1210-V9 1210-V15

  27. Countermeasure – NTS Crystal Remained (1) Steam Inspection inside to confirm condition Vent gas 1210-V10 1210-C2 1210-V12 1210-E9 SO2 gas 1210-E7 1210-S2 1210-E8 1210-V8 Si liquid Temp. ; -1 ℃ 1210-E11 Nd liquid CW 1210-E10 Si liquid to Nd col. HX to Oxmation Si liquid Shut down and washing column 1210-V9 1210-V15

  28. Countermeasure – NTS Crystal Remained (2) Inspection results • Found crystal like AS and Si accumulated at manhole and upper packing of liquid distributor. • However, this condition is quite same as previous time (GTA2011)

  29. Countermeasure – NTS Crystal Remained (3) Inspection results ND + Si liquid circulation SO2 gas The other parts is quite clean and in the normal condition.

  30. Possible Causes Abnormal plume at first sight • Bad quality of ND/Si solution • Abnormal SO2 gas feed to DS column Problem in re-starting up (1st time) • Abnormal of solution in DS column Problem in re-starting up (2ndtime) • NTS crystal remained in the column Plume emission during post-washing DS column re-started up • Misoperation from start-up procedure • SO3 contaminated in SO2 pipeline

  31. Possible Causes – Misoperation (1) DS column start-up procedure In case of DS column shutdown, we normally follow below steps: Feed 25%AW directly to the column in order to prevent decomposition of inside solution that NOx gas could be generated (Target pH = 9). Before start-up, circulate solution in the column until bottom temp. decreases to around -5 deg C. Start SO2 feed at 30% operation load until pH decreases to around 2.4 before increasing load.

  32. Normal Start-Up

  33. Possible Causes – Misoperation (2) Normal case: Emergency S/D on 9 Aug’12 due to 4140-B1 tripped Start SO2 feed 30% for 30 minutes until pH drop Fill 25%AW until pH = 9

  34. Possible Causes – Misoperation (3) Normal case: Control S/D on 12 Aug’12 for lube oil tank modification Start SO2 feed 40% for 30 minutes until pH drop Fill 25%AW until pH = 9

  35. Possible Causes – Misoperation (4) Normal Case: October’12 shutdown Start SO2 feed 30-40% for 30 minutes until pH drop

  36. Possible Causes – Misoperation (5) Normal Case: Repair TI-41-202/207 Start SO2 feed 30-40% for 30 minutes until pH drop

  37. Start-Up during Problem Occurred

  38. Possible Causes – Misoperation (6) Start-up after analyzer calibration Start SO2 feed 20% and maintain condition

  39. Possible Causes – Misoperation (7) Start-up after column emptying Start SO2 feed 20% and maintain condition

  40. Possible Causes – Misoperation (8) Start-up after column washing Start SO2 feed 20% for 30 minutes and still found high plume emission. Then, switch SO2 to Si Column

  41. Possible Causes – Misoperation (9) Start-up after condition confirmation Start SO2 feed 5-10% for 30 minutes until pH drop

  42. Possible Causes Abnormal plume at first sight • Bad quality of ND/Si solution • Abnormal SO2 gas feed to DS column Problem in re-starting up (1st time) • Abnormal of solution in DS column Problem in re-starting up (2ndtime) • NTS crystal remained in the column Plume emission during post-washing DS column re-started up • Misoperation from start-up procedure • SO3 contaminated in SO2 pipeline

  43. Short-Term Countermeasures Countermeasures for recurrence prevention • Manually control AT-41405 • Add routine sampling at 4140-V5

  44. Countermeasures – SO2 Scrubber Manually control by 30% opening Add routine sampling for concentration confirmation. Begin with 6 times/day after problem occurred, now is reduced to 1 time/day.

  45. Further Actions Further actions for recurrence prevention • Maintain routine sampling at 1 time/day • Install redundancy of AT-41405 • Develop monitoring program for DS column • Increase PM frequency of analyzers in SA plant • Add timer alarm to %OP of AT-41405

  46. Further Actions – AT-41405B Installation B Install parallel analyzer (AT-41405B) for cross-checking.

  47. Further Actions – Monitoring Program Add related parameters of both DS column and SO2 scrubber.

  48. Further Actions – Increase PM Frequency Since August’12, we have found many times error of acid concentration and free SO3 analyzers in SA plant. So, we would like to request for increasing PM frequency to 1 time / month.