METHANATOR FEED/EFFLUENT EXCHANGERS Presented By Taha R Sheikh Management Associate( Projects) Case History And Way Forward

E-209(A/B) Location 200 area (Benfield area) Ammonia Plant 200 area (Benfield area) South of the Benfield towers Series configuration after C-209

E-209(A/B) Process E-209 A Syn gas from C-208 C-209 E-209 B E-212

Tube Failure history Corrosion of tube from external (shell) side Tube leakage caused synthesis gas to bypass around C-210 Carbamate formation in synthesis gas compressor loop

Inspection history Lake Charles 1965 Replacement in 1987 Tubes 3/4” OD, 14 BWG ,SA-214(CS) Tubesheet A-105-II (CS forged) Replacement in 1987 Tubes ¾” OD, 14 GA, SS-316 Tubesheet (Fixed) TS C-1/2 Mo Tubesheet (Floating) TS 1-1/4Cr-1/2Mo

Inspection history Pre mobilization 1995 Inspection conducted by M/s Industrial Technical Company (ITC) at Lake Charles, USA 20% tubes inspected around existing plugged tubes Major damage (>50% loss) tubes Moderate damage tubes Already plugged tubes Exchanger 21 100 27 E-209 A 58 123 09 E-209 B

Inspection history E 209 B 1998 51 leaked tubes found in SFT & TTS seal weld leakages 51 Tubes were plugged Unsuccessful Weld repair of TTS joints Failed attempts of PWHT bypass line across shell installed

Inspection history 1998 - 2007 E 209 A 1998 Exchanger taken in service without any internal inspection 2001 Heavy Sludge accumulation on shell side. Pressure drop of 13psig in 10 min from shell side No repair done 2003 Pressure drop of 3.5psig in 30 min from shell side Again no repair done. Till 2007 Exchanger was in service with leakage

Replacement in Ammonia BMR To Increase the ammonia plant capacity to 1570 MTPD Designed and manufactured by Descon Engineering in year 2007 Design was reviewed by Haldor Topsoe.

Enhanced exchanger design 2 Identical Horizontal Shell & Tube Heat Exchanger (BEM) Having Process gas on both tube and shell sides. Design pressure 30 kg/cm3. Design temperature 400˚C.

Enhanced exchanger design Tube Material SA-213 T12 (1Cr0.5Mo) Number 3613 Nos. Tube sheet Material SA-182 F-12 Cl.2 Thickness 105 mm Shell Material SA-387 Gr.12 Cl.2 (1Cr0.5Mo) Thickness 20 mm Diameter 1550 mm Total length 6991 mm

Findings in 2012 No inspection was conducted Until August/September 2012 Flow hindrance across Synthesis Gas compressor(K-306 A) leakage in E-209A confirmed by Laboratory analysis In September 2012 Boroscopy was conducted of E-303 A/B Leakage was detected across E-209 A/B tubes

Inspection history 2012 E-209 A Dismantled in September 2012 (gas curtailment) Benfield solution came from bonnet / tubes Benfield scale on both tubesheets SFT and hydrostatic testing revealed 119 leaked tubes Leaked tubes were plugged by hammering Final hydrostatic-test passed

Inspection history E-209 A 2012 East end Tubesheet – Tubes choked due to Benfield deposits

Inspection history E-209 A 2012 West end Tubesheet – Benfield coming from leaked tube

Number of tubes to be plugged Inspection history M/s Stamicarbon TA-2013 Performed eddy current inspection of both the exchangers Defect category Number of tubes to be plugged % in E-209 A % in E-209 A+B > 50 % 927 (+119) 29 15 > 60 % 756 (+119) 24 12 > 70 % 474 (+119) 16 8

Inspection history E-209 A TA-2013 pulled out tube leaked having Under deposit corrosion on tube outer surface

Inspection history E-209 A TA-2013 Thinning on pulled tube outer surface due to under deposit corrosion

Inspection history E-209 A TA-2013 617 plugged tubes recommended in Stamicarbon report

Reasons for Benfield Carry over High performance washing trays not in service in Absorber KO Drum (C-209) Demister pads f CO2 Absorber (C-208) and Absorber KO Drum (C-209)

Explanation of Corrosion Benfield solution droplets evaporates leaving Benfield scale on outer surface of tubes Benfield salts are corrosive in nature and cause under deposit corrosion Severe localized thickness loss which results in tube leakage. Corrosion products promote further deposition and corrosion of tube material No corrosive scale / deposits and corrosion occur after evaporation No affect on E-209B tubes and upper portion of E-209A

Explanation of Corrosion

Recommendations Improving efficiency of demisters of CO2 Absorber (C-208) and Absorber KO Drum (C-209) High efficiency washing trays in Absorber KO Drum (C-209) to be taken into service regularly Regular analysis of synthesis gas to E-209A E-209A shell side washing with detergents Replace the corroded tubes/tube bundle in E-209A with existing Grade T12 (1Cr1/2Mo) material

Thank you!