Sunday, 19 November 2017

Ammonia Plant CO2 Absorption Process


































 Benfield system

  1. 1. AMMONIA PLANT CO2 ABSORPTION PROCESS Prem Baboo Sr. manager(Prod) National Fertilizers Ltd, India FIE ,Institution of Engineers( India) Technical Advisor & an Expert for www.ureaknowhow.com
  2. 2. CO2ABSORBER&REGENERATOR CO2 TO UREA PLANT .6 Kg/Cm2 43.2KNM3 9.14 P-1307 P1301 (A,B&C) E302 A&B 4 8 % 48% IN CO2-17.10% Ar-.75% N2-21.3% CH4-0.4% CO-0.11% H2-60.84% OUT CO2-.11% Ar—0.30% N2—25.65% CH4—0.5% CO--.13% H2—73.51% 13FIC 20 13-FIC-2 1 8.548.54 FLOW 1135M3 FLOW 345M3 104 M3 104M3 3.94M PALL RINGS 1.5” ..01M TOTAL 517M32”PALLRINGS L.P. STEAM 30 TON 13 FIC02 P.G.
  3. 3. BENFIELD PROCESS FLOW DIAGRAM 13 FIC02 13HIC101 DM WATER FROM TANK 307 MT/Hr. PROCESS GAS TO METHENATOR 600 C 345M3 FAN COOLER E 1303 ABSORBER F 1302 28.45MT/Hr 1100 C PROCESS CONDENSATE TX-1301 CICULATION PUMP BOOSTER PUMP REGENATOR F-1301 B-1305 E-1302 A/B B1306- TO FGR FLASH GAS 1590C PROCESS GAS CONDENSATE E1308 E1306 LP STEAM B1301 1130 C1162M3/ Hr B-1303 T0 DE-AERATOR C.W.
  4. 4. REMOVAL OF CO2:- PROCESS FOR REMOVAL OF CO2 ARE BASED UPON SCRUBBING OF GAS WITH SOME SOVENT (PHYSICAL OR CHEMICAL) THE SOLVENT SHOULD HAVE THE FOLLOWING PROPERTIES:- i. HIGH CO2 SOLUBILITY ii. LOW VISCOSITY iii. HIGH STABILITY UNDER OPERATING CONDITION iv. NO REACTIVITY UNDER OPERATING CONDITION v. VERY LOW VAPOUR PR UNDER OPERATING TEMP
  5. 5. GENERAL CONSIDERATION IN PROCESS SELECTION 1. PARTIAL PR OF CO2 IN FEED GAS AND TOTAL PR OF ABSORPTION 2. CO2 PURITY 3. GAS CONTAINING CO 4. AVAILABILITY OF UTILITY AND COST TWO TYPE OF PROCESSESS A. PHYSICAL PROCESS SOLVENT 1. WATER SCRUBBING WATER 2. LINDE’S RECTISOL METHANOL 3. ALLIED SELEXOL POLYPROPYLENE GLYCOL DIMETHYL EITHER 4. FLUOR’S PROCESS PROPYLENE CARBONATE 5. PURISOL N METHYL- 2 PYRROLIDINE 6. SULPHINOL TETRAHYDRO THIOPHENE 1, 1 DIOZIDE
  6. 6. B. CHEMICAL ABSORPTION BEST SUITED FOR LOW CO2 PARTIAL PRESSURE 1. MEA PROCESS:- MONO ETHANOL AMINE (REBOILER ENERGY IS HIGH 2NH2(CH2)2 OH + CO2+H2O=[HO(CH2)2NH3]2CO3 DISADVANTAGE:- (i)[HO(CH2)2NH3]2CO3+CO2+H2O= 2HO(CH2)2NH3HCO3 (ii) HO(CH2)2NH2+CO2= HO(CH2)2NHCOONH3(CH2)2OH CARBOMATE IS CORROSSIVE IN HOTER PARTS OF MEA • GV PROCESS • CATACARB PROCESS • BENFIELD PROCESS C. PHYSIOCHEMICAL PROCESS 1. MDEA PROCESS( METHYLDIETHANOAMINE
  7. 7. BENFIELD PROCESS OVER 700 BENFIELF PLANTS IN WORLD ENERGY 660 – 1140 KILO CALORIE PER NORMALM3CO2 45% FOR REGENERATION 55% FOR ABSORPTION K2CO3+CO2+H2O=2KHCO3+HEAT( MILD EXOTHERMIC) CO2+H2O=HCO3- +H+ CO3-- +H2O=HCO3- +OH- CO2+CO3-- H2O=2HCO3 1M3 30% K2CO3 SOLN ABSORBED 10M3 CO2 WITHOUT ANY ACTIVATOR ACTIVATOR ACTION:- DEA (R2NH) R=CH2CH2OH R2NH+CO2=R2NCOOH (INTERMIDIATE PRODUCT) R2NCOOH+K2CO3+H2O= R2NH+2KHCO3 K2CO3+CO2+H2O=2KHCO3
  8. 8. PROPERTIES OF DEA MW = 105.14, SP GR = 1.0966, MELTING PT = 28O C , BP = 10/100/760MMHG= 150/205/260 ANALYSIS OF LEAN SOLUTION / RICH SOLN K2CO3 KHCO3 EQ K2CO3 F/C TV V+5 DEA FE 17.22 15.32 27.80 .38 10.4 .4 2.42 42.1 10.67 25.52 28.30 .67 .85 .67 2.8 ---- CALCULATION OF F/C 1 _ _%AGE K2CO3 %EQ K2CO3 % EQ K2CO3 = % K2CO3+(MW KHCO3)100 % KHCO3 MW K2CO3)138 17.22+(0.69)X15.32=27.8016 1- FC 1_ (17.22) = 0.38 IN LEAN SOLN 27.8016 F/C IN RICH / LEAN SOLN = 0.858/0.352 (DESIGN VALUE) F/C = F/C RICH – F/C LEAN (ACTUAL) . F/C RICH – F/C LEAN (DESIGN)
  9. 9. COMPARISON BETWEEN PLANTS RECTISOL PHYSICAL ABSORPTION . LOWER ENERGY .REMOVAL OF ALL IMPURITIES SUCH AS ORGANICS, H2S, BENZENE, GUM FOAMING AND HYDROCARBON .PRODUCTION OF GAS WITH NEGLIGIBLE WATER GAS SOLVENT METHANOL . HIGH CO SLIP FROM CO SHIFT SECTION .FINAL REMOVAL OF CO,CO2 BY N2 WASH INI BENFIELD CHEMICAL ABSORPTION 612KCAL/NM3 CO2 B-1306 YES LP BOILER AFTER REBOILER NO REGN SINGLE ACTIVATOR SINGLE DEA HYDROLLIC TURB SINGLE( POWER GENERATION) AERATION OF SOLN NO FAVOURABLE CO2 BLOWER NO GV CHEMICAL ABSORPTION 713.5KCAL/NM3 CO2 B-1306 NO YES DOUBLE DUAL (DEA+GLYCINE) DUAL PUMP DRIVEN AVAILABLE CO2 BLOWER VENEZEULA CHEMICAL ABSORPTION 700KCAL/NM3 CO2 B 1306 YES YES YES DOUBLE DUAL DEA+GLYCINE) DUAL PUMP DRIVEN AVAILABLE CO2 BLOWER NO
  10. 10. contd CO2 BLOWER YES DISADVANTAGE NO PGR NO OF PUMP AND COLUMN MORE INITIAL COST HIGH CO2 EXCESS VENT NO CO2 EXCESS PGR AMMONIA PRODUCTION NO CO2 EXCESS UTILIZE CO2 EXCESS VENT PGR AVAILABLE
  11. 11. CORROSION CO2 ITSELF WEAKLY ACIDIC HOT POTASSIUM CARBONATE SOLN AGGRESSIVE FOR CORROSION COMPOUND MAY FORM WITH THE SCRUBBING SOLN CORROSIVE TO STEEL THEREFORE, A VANADIUM SALT V+5 IS USED IN THE SOLN AS A CORROSION INHIBITOR THE VANADIUM OXIDISES THE IRON ON MET AL SURFACES (VANADATION) BY ADDING V2O5 THE RESULTANT OXIDES FE3O4 MAGNETITE PRODUCE A TIGHT ADHERENT FILM ON THE SURFACE WHICH RESULTS IN ESSENTIALLY NO CORROSION DURING OPERATION UNLESS THE FILM IS DISTURBED V+5 +Fe2e = V+4 +Fe3e FERRIC Fe2O3 MOST STABLE FORM V2O5 CONVERTS Fe2O3 TO Fe3O4 2FeO +V2O5 = Fe2O3 + V2O4 FeO + Fe2O3 = Fe3O4 (MAGNETITE) MAINTAIN PENTAVALENT VANADIUM NOT LESS THAN 0.2 WT % INCREASE V+5 CONTENT BY ADDITION FRESH V2O5 (VANADIUM PENTAOXIDE) ADDITION OF KNO2 IS RECOMMENDED FOR OXIDATIION METHOD KNO2 +V2O4 = V2O5 +KNO
  12. 12. CORROSION AND PROBLEMS IN PLANTS • 1 – 1986 AND 1992 IN RCF ( HALDOR TOPSOE PLANT) • 2 – 1986 : PRECIPITATED BICARBONATE PEELS-OFF THE PASSIVATIION LAYER IRON • AND VANADIUM IN THE SOLN CO-PRECIPITATE WITH THE BICARBONATE FORMING • A SLURRY PLANT WAS SHUT DOWN 30 DAYS CIRCULATION PUMPS REPAIRED • NOV 1994 – HYDRO AGRI TRINIDAD’S TRINGEN II – 33 DAYS SHUT DOWN • PROTECTIVE MAGNETITE LAYER IN THE ABSORBER BOTTOM AND DISTRIBUTER BECOME DAMAGED FORMATION OF IRON CARBONATE CORROSION RATE INCREASED COMPLETE DEPLETION OF VANADIUM • 1992 – KRIBHCO HAZIRA – KELLOG’S DESIGN • FOLLOWING A NUMBER OF CRASH SHUT DOWN DUE TO NG AND MAINTENANCE JOB • THE CO2 PRODUCT PURITY OF BOTH UNITS CAME UP TO 97.96% DUE TO FAILURE OF FLOATING HEAD GASKET IN THE FLOATING HEAD TYPE EXCHANGER (REBOILERS) • SUSPECTABLE FAILURE AND THIS ALLOWED LEAKING PROCESS GAS TO ATTACK AND DESTROY THE PASSIVATION LAYER OF CS WALL OF REGENATOR • 2001 – VENEZUELA JOSE FERTILISERS . AFTER REDUCTION OF LT CO SHIFT CONV CATALYST – CATALYST DUST BEFORE LINE UP TO GV DID NOT BLOW / REMOVE PROPERLY Fe CONTENT IN GV SOLN -~ 5000 PPM VISCOSITY OF SOLN INCREASED FREQUENT CHOCKING OF STRAINERS AND DRAIN LINES OCCURS WHOLE SOLN FILTERS THROUGH Fe CONTENT CAME DOWN AND VISCOSITY NORMALISED
  13. 13. BENFIELD SYSTEM: START UP CHECK LIST :- 1. TRIP SYSTEM: IS-4, IS-5, IS-301A, B, C, IS 303, IS 304 ARE IN RESET CONDITION 2. STROKE CHECKING OF ALL CONTROL VALVES 3. CHECK a. 13 HV- 10 ------------CLOSE b. 13 HIC 101-------------CLOSE c. 13 FCV 02 -------------BY PASS & CV F/C d. ISOLATION VALVES OF 13 FIC -01, LIC -01, 13LIC-20- I/2, 13PV 28 13 LCV- - 26-1/2 CLOSE e. DM WATER CIRCULATIION – NORMAL f. CW TO E -1308 A/B – OPEN g. F 1302 PR NORMAL WITH NG > 15KG/CM2 h. N2 TO F 1301 OPEN j. PUMPS – P-1307/ P- 1301 PROPERLY LINED UP k. PUMPS ELECTRICALLY ENERGISED l. PUMPS L.O. CIRCULATION & SEALING WATER SYSTEM NORM
  14. 14. Contd. m. LEVEL IN B 1305 LESS THAN 100% n. O2 CONTENT IN THE SYSTEM LESS THAN 100PPM 4. START CIRCULATION KEEP E 1303 FANS IN STOPPED CONDITION 5. KEEP 13HV 10 CLOSE AND START INDIRECT HEATING BY SM STEAM PR LESS THAN 5 KG/ CM2 , TEMP LESS THAN 1800 C F 1301 PR 2 KG/CM2 (N2) OBTAIN BENFIELD SOLN TEMP 105O C PASSIVATION A. STATIC – E 1302 A/B FLOODED CONDITION TEMP=130O C DURATION 48 HRS B. DYNAMIC – CIRCULATION RATE 80% DURATION 36 HRS MAINTAIN V+5 EQUAL 0.5% K2CO3 KHCO3 EQ K2CO3 F/C V+5 DEA FE 20.96 6.37 25.33 0.172 0.47 2.18 66.74PPM LOCAL DRAINING B 1303 ON R1205 BY PASS MOV45 FULL CLOSED
  15. 15. FOR INDIRECT HEATING STOPPED CONDITION NG FLOW TO PRIMARY REF 6000NM3, STEAM FLOW 30 TE/HR RECYLE GAS FLOW ( 12FIC 02 +12 FIC 17) EQUAL 4000NM3 ( 800 +2200) 12TJR 1/12, 06 =5000 C / 7500 C 13 PI C11= 0.6KG/CM2 B 1305 STEAM EJECTORS , X 1301 A/B/C/D I/VS OF VAPOURS AND SL STEAM I/V MOTIVE STEAM TO BE OPENED FOR LINING UP SEQ 1. X 1301D 2. X 1301C 3. X 1301B 4. X 1301A FROM CCR 13 HIC O4, O5, O6, O7, INITIALLY TO BE CLOSED AND TO BE OPENED AFTERWARDS. 13 FIC O2 I/VS TO BE OPENED
  16. 16. contd 13 HIC 101 TO BE OPENED LINE UP 13 TIC O9 STOP NG TO F 1302 AND N2 TO F 1301 BLIND TO BE PROVIDED STOP LOCAL DRAINING OF 1303 AND LINE UP TO PC HEADER
  17. 17. BENFIELD THEORY a. FAVOURABLE PARAMETERS FOR ABSORPTION 1. HIGH PRESSURE ( LIMITATION REF PRESSURE) 2. BETTER ACTIVATOR ( DEA, IN LINE II GLYCINE ALSO) 3. LOWEST F/C 4. BETTER FILTERATION ( 10 MICRONS OR LESS) 5. OPTIMUM SPLIT STREAM TEMP 6. IMPROVED PACKED BEDS AND INTERNALS b. FAVOURABLE PARAMETERS FOR REGENERATION 1. LOW PRESSURE 2. PROPER DISTRIBUTION OF RICH SOLN 3. IMPROVED PACKED BED AND INTERNALS 4. REGN STEAM FLOW/ PR / TEMP OPTIMUM
  18. 18. FOAMING CAUSES: IMPURITIES i. SODIUM:- <1.0 % Na LIMITED NaHCO3 SOLUBILITY ii. CHLORIDE:- AS CL- >100PPM iii. INERTS SALTS:- FORMATE, THIOSULPHATE ETC. CAN JOLERATE UPTO MINIMUM INNNERTS IN SOLUTION DEENSITY AND ABSORPTION AFFECTED. iv. HEAVY METALS:- POTENTIAL FOR LOSS OF PASSIVATION. v. SOLUBLE Fe CONTEST:- CONTENT UPTO 150PPM (NORMAL) MAX SOLUBLE 200 – 250 PPM – CORROSION OCCURING. vi. SOLIDS IN SOLUTION:- ABRASIVE, LOSS CORROSION PROTECTION, FOAMING OF SOLUTION. vii. SOLUBLE INORGANIC CONTAMINATES:- - TOTAL SALTS HIGH - PROCESS TEMP INCREASES - LOSS OF ABSORPTION EFFICIENCY viii. SOLUBLE ORGANIC CONTAMINATES:- - FREQUENT CAUSE OF FOAMING OF SOLUTION - SOME LOSS OF ABSORPTION EFFICIENCY ix. GREASE AND OIL.. x. INTERNALS DISTURBES
  19. 19. FOAMING CAUSES i. DUST OF ACTIVATED CARBON ii. SUSPENDED METALLIC COMPOUNDS, WHICH MAY DISTURB SURFACE TENTION iii. DECOMPOSITION PRODUCTS iv. ORGANIC SUBSTANCES, GREASE, LUBEOIL, PAINT BITUMIN EPOXY RASINS. v. SULPHIDES FOAMING IS INDICATED BY :- 1. HIGH PDI OF ABSORBER, REGENERATOR 2. SOLUTION CARRY OVER 3. SOLUTION HOLD UP IN PACKINGS 4. LEVEL INSTABILITY 5. INCREASE IN CO2 SLIP
  20. 20. FOAMING CONTROL 1. SIDE STREAM FILTRATION – A) MECH FILTER~ 10 MICRONS FLOW – 5% TO 10% OF CIRCULATION RATE. (CONTINUOUS REMOVAL OF SOLIDS ) B) ACTIVATED CARBON FILTER:- TO REMOVE i. ORGANIC MATTER AND CONTEMINANTS ii. DECOMPOSED COMPOUNDS iii. IF COLOUR OF SOLN IS DARK, IMPROVE TRANSPARENCY 2. LIMITED USE ( 20ML) OF ANTIFOAM AGENT (UCON 50 HB 5100, POLYGLYCOLS , SILICONES. 3. DEMISTERS OF ABSORBER AND REGENERATOR FLUSHING BY BFW
  21. 21. FOAMING TEST 50 ML FILTERED BENFIELD SOLUTION AT 90OC SHAKEN VIGOROUSLY OR N2 IS BUBBLED FOR ONE MINUTE HIGHT OF FOAM > 40 MM COLLASPE TIME > 10SEC CAUSE OF INCREASE IN CO2 SLIP 1. INCORRECT SOLUTION FLOW RATE. 2. HIGH Fe OF HPC SOLUTION. 3. INCORRECT LEAN/ TOP SOLUTION TEMP. 4. INCORRECT SOLN COMPOSITION 5. FOAMING 6. INCORRECT SOLN / GAS – DISTRIBUTION IIN BEDS 7. DDISTURBANCE IN PACKING ARRANGEMENTS 8. DAMAGE / DISLOCATE INTERALS OF ABSORBER/ REGENERATOR
  22. 22. CAUSES OF BAD REGENERATION 1. LOW REGENERATION STEAM FLOW / TEMP / PR 2. HIGH SOLUTION FLOW RATE 3. ABSORBER GAS INLET TEMP LOW 4. REGENERATOR PR HIGH 5. INCORRECT STEAM / SOLUTION TEMP PROCESS FOR REMOVAL OF CO2 ARE BASED UPON SCRUBBING OF GAS WITH SOME SOVENT (PHYSICAL OR CHEMICAL) THE SOLVENT SHOULD HAVE THE FOLLOWING PROPERTIES:- i. HIGH CO2 SOLUBILITY ii. LOW VISCOSITY iii. HIGH STABILITY UNDER OPERATING CONDITION iv. NO REACTIVITY UNDER OPERATING CONDITION v. VERY LOW VAPOUR PR UNDER OPERATING TEMP *************************************************************************************




















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