CASE STUDY

HT CATALYST DE‐HUMIDIFICATION   AT

N.F.L. VIJAIPUR‐I Presented by:

Rajan Thapar

GM(O & M)  1

CONTENTS

• Company profile • Plant History• Brief Description of plant• Case Introduction• Problem description • Possible Causes• Trouble Shooting • Performance Comparison• Conclusion

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NATIONAL FERTILIZERS LIMITED(A Govt. of India Undertaking)

• A Schedule ‘A’ and ‘Mini Ratna’ Company.

• Incorporated on 23rd Aug. 1974, manufactures and marketsUREA ( KISAN UREA).

• Country’s 2nd largest producer of nitrogenous fertilizer, withtotal Production Capacity of 35.68 Lakh Te. of urea perannum (15.5% of total Urea produced in the country).

• Operates 4 units in three States at Nangal, Panipat, Bathinda& Vijaipur

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STRATEGICALLY LOCATED –NFL UREA PLANTS

Nangal ‐ I  1961 

Nangal ‐ II 1977

(Punjab)

Bhatinda 1979

(Punjab)

Panipat 1979

(Haryana)

Vijaipur ‐ I 1988

Vijaipur ‐ II 1997

(Madhya Pradesh)

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HISTORY OF VIJAIPURGLORIOUS PAST

VIJAIPUR’S NAME IS ETCHED IN THE ANNALS OF INDIAN HISTORY. DURINGTHE FIRST WAR OF INDEPENDENCE, IN SEPTEMBER 1858 , A PITCHEDBATTLE WAS FOUGHT ON THIS VAST STRETCH OF UNDULATING TERRAINBETWEEN THE GREAT MARTYR TANTYA TOPE AND THE BRITISH.

TILL DATE THE IRON CROSS ON THE GRAVE OF ALEXANDER FAWCETTKILLED DURING THIS BATTLE STANDS AS A SILENT TESTIMONY.

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NFL VIJAIPUR AT A GLANCE

NFL Vijaipur has two streams : Vijaipur‐I

Vijaipur‐II

Vijaipur‐I: Country’s first Inland gas basedFertilizer Plant Commissioned in 1987

Vijaipur‐II: Commissioned in 1997

More energy efficient

Has dual feed (NG + Naphtha) facility

Total Capacity of Vijaipur Plant: 54 % of NFL’s total urea productioncapacity.

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NFL VIJAIPUR AT A GLANCE

The 1st Gas based inland Fertilizer plant on HVJ Gas pipe line.  

• No. of Employees :    730

• Finished Product  :    Urea

• Intermediate Product :  Ammonia

• Raw Material Used      :   NG &  RLNG 

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NFL VIJAIPUR AT A GLANCE 

VIJAIPUR‐I VIJAIPUR‐IICapital Employed Rs 533 Crores Rs 1067 Crores

Start of Commercial  Production 1st Jul’ 1988 31st Mar’1997

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Manufacturing Process 

Urea Production Process:

Urea is produced by reaction of Ammonia (NH3) and Carbondioxide (CO2 ) based on “Saipem ammonia stripping process”

Ammonia & CO2 are obtained from Ammonia plant based onHTAS’ steam reforming of Hydrocarbon (NG/RLNG) .

Power is generated in Captive Power plant having 3 nos. GasTurbine Generators in Co‐ generation mode with steamgeneration from heat recovery units

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Post revamp Production Capacities

Plant

Daily Rated Reassessed Capacity (MTPD)

Annual Capacity (MT per year based on 330 days of operation)

Ammonia Urea Ammonia Urea

Vijaipur‐I 1750 3030 577500 999900

Vijaipur‐II 1864 3231 615120 1066230

Total 3614 6261 1192620 2066130

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INTRODUCTIONAmmonia Plant of NFL Vijaipur‐I was under start up on15.07.2015 after a short shutdown attending tube leakage ofsurface condenser of Process Air Compressor Turbine and aspart of startup activities BFW circuit was charged by running theBFW Pump to take level in HP Boilers and also to check thedome flange of BFW Pre‐heater (E‐1211A/B) installed indownstream of LT CO Shift catalyst Convertor(R‐1205) as thedome flange was opened in the shutdown to check any tubeleakage in the exchanger.

Ingress of Water in HT Catalyst bed:• Water ingressed in the catalyst bed due to leakage of BFW from a 3‐

4 mm hole developed in the tube sheet of BFW Pre‐heater (E‐1210B) at HT CO Shift Convertor outlet.

Identification:• when drains of the CO Shift convertors checked for any

accumulation of water during Plant re‐start up , lot of water foundcoming through the drain of HT CO Shift convertor on continuousbasis.

• Continuous increase in the bottom bed catalyst temperature @ 4.7°C/hr.

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• On the basis of the temperature profile of the catalyst bed it wasenvisaged that water admitted up to bottom bed only.

• To identify the leaky BFW Pre‐heater one of the BFW pump waskept running and the pre‐heaters E‐1307A/B, E‐1211A/B & E‐1210A/B at LT, MT & HT Convertors outlet respectively checkedone by one by opening gas side drains. Finally leakage wasconfirmed from E‐1210A/B.

• On opening the domes of the exchanger E‐1210A/B a 3‐4 mmhole observed in the upper half tube sheet of E‐1210B.

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DEHUMIDIFICATION OF HT CATALYST

Objective:• To dry out the bottom bed of HT CO Shift catalyst that was

soaked in water.• Consultation: M/s Sud Chemie & RCF were contacted and it was

suggested to cool the catalyst in reverse direction with nitrogenbefore de‐humidification to save the boiling of absorbed water inthe catalyst mass by travel of heat from the top bed which couldotherwise led to cracking of the catalyst.

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STEPS FOLLOWED• Steps followed in consultation with M/s Sud Chemie:A. Controlled cooling of HT CO Shift catalyst:• Reverse purging of the catalyst with nitrogen at ambient

temperature: Carried out to cool the top bed which was at267 °C. This was done to avoid contact of wet bottom bedwith very hot nitrogen when heating of second bed would bedone with nitrogen blower.

• The purging was carried out for 14 hrs at 1.5 kg/cm2 nitrogenpressure with 2” nitrogen line connected in the bottom drainand vented from 2” vent at the top of the convertor.

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• Further cooling was carried out at 4 kg/cm2 nitrogen pressure for 24 hrswith nitrogen venting through 8” opening in nitrogen start up circuitconnected in HT inlet line to increase the nitrogen flow.

• Thereafter ¾” nitrogen hose connection was also given through PG pointin between the two beds. Pressurization and depressurization was carriedout for 5 times through 2” vent closing 8” opening in nitrogen start upcircuit for 1 hr.

• Further nitrogen pressure was increased to 5.5 kg/cm2 and venting donetrough to 2” vent and also through 8” opening in the nitrogen circulationcircuit for 48 hrs. In this period moisture analyzed at HT outlet and found3060 mg/Nm3.

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• Skin temperature of the vessel was also recorded by cutting pockets in theinsulation at five different locations to ensure uniform temperature profileduring the above period of cooling.

• The temperature profile of the bed after the above cooling and beforestarting nitrogen circulation.

• Bottom bed temperature (°C): 17• Top bed bottom temperature (°C): 23• Top bed top temperature (°C): 110• Total time taken in cooling the catalyst beds was 85 hrs.• Rate of cooling of the bottom bed was 2 °C /hr. Rate of cooling of the top

bed after attaining the maximum temperature was 5 °C /hr.17

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T-1

T-2

T-3

HT CO SHIFT CONVERTOR R-1204

Catalyst Details:• Catalyst: ShiftMax 120• Catalyst Volume: 64 m3• In service since 01.03.2010

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0

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100

150

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250

300

T-1T-2T-3

HT CATALYST BED COOLING WITH N2

B. HTS Heating:• Nitrogen circulation with blower started at 1.5 kg/cm2

nitrogen pressure maintaining nitrogen temperature 125 °C atthe HTS bed inlet. Gradually nitrogen pressure increased to 3kg/cm2.

• Nitrogen circulation circuit: N2 Blower– Heater‐HTS ‐ Cooler –Separator – N2 Blower.

• During heating process moisture analysis in the circulatingnitrogen at convertor outlet was carried out at every twohours. 20

• Reactor condition was held under the above condition tillthe hole catalyst bed temperature stabilized at around 125°C.

• Maximummoisture content was reported 716 mg/Nm3.• HTS inlet temperature was held at 125 °C for 4 hrs when

moisture content of last two samples was constant at 350mg/Nm3.

• The convertor inlet temperature was raised further.

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• The convertor inlet temperature was raised @ 15‐20 °C till theconvertor inlet temperature was reached to 175 °C.

• In this temperature range the maximum moisture content wasanalyzed to 4000 mg/Nm3.

• HTS inlet temperature was held at 175 °C for 4 hrs and whentwo moisture analysis became constant at 170 mg/Nm3 thenfurther heating of the catalyst bed was started.

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• Thereafter nitrogen circulation circuit was lined up throughP.Reformer as:

• Blower–Heater‐Primary Reformer–Secondary Reformer‐RG Boiler‐HTS ‐ Cooler – Separator – Blower.

• Further the convertor inlet temperature was raised up to 270 °C@15‐20 °C/h maintaining reformer WHS temperature at 200 °C.

• During entire de‐humidification process total water separated in theN2 Blower suction K.O. drum was measured and it was 1500 litre.

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• Heating of HTS catalyst bed was done with nitrogencirculation for total 45 hrs.

• During whole heating process condensate from N2Blower K.O. drum was checked to confirm release ofwater from HTS Catalyst.

• Total time taken for entire de‐humidification processwas 130 hrs (5.5 days).

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50

100

150

200

250

T-1T-2T-3

HT CATALYST BED HEATING WITH N2

• Parallel to above activity Primary Reformer temperature wasraised to make it ready for feed in.

• Before feed in water collected from the K.O. drum was100ml/h.

• Reformer feed in done and HTS was lined up through thenormal procedure.

• After feed in load was gradually increased while checking COslip and HTS bed pressure drops.

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Performance of HTS CatalystPARAMETERS BEFORE THE INCIDENT AFTER THE INCIDENT

INLET TEMP (°C) 350 349

OUTLET TEMP (°C) 415 414

TEMP DIFF. (°C) 65 65

PRESSURE DROP (Kg/cm2)

0.32 0.35

CO slip (%) 2.71 2.71

PLANT LOAD (%) 101 105 27

Conclusion• Timely and appropriate action saved the catalyst from damage.• Dehumidification with proper procedure retained the performance of the

catalyst.• The catalyst is still performing well.

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THANK YOU