Stamicarbon Urea Process Description Essay

Indian Farmers Fertiliser Co-operative’s (IFFCO) is the biggest fertiliser cooperative in the world, operating five plants across India. IFFCO owns an ammonia-urea complex in Kalol in the state of Gujarat, India.

The Kalol facility has a capacity of 0.36mtpa of ammonia and 0.55mtpa of urea. Spread over 96ha, the facility also produces 1,980tpa of dry ice and 3,960tpa of liquid carbon dioxide.

Design and construction of IFFCO’s Kalol plant

The Kalol unit was commissioned in 1975 with a capacity of 910t/d of ammonia and 1,200t/d of urea.

In 1997, it was expanded to increase the ammonia capacity to 1,100t/d and the urea capacity to 1,650t/d.

Between 2005 and 2006, IFFCO launched an energy saving project aimed at reducing energy consumption by the plant.

“IFFCO owns an ammonia-urea complex in Kalol in the state of Gujarat, India.”

As part of the project, several upgrades including the installation of a new guard bed, ammonia converter and wash unit were made to the facility.

In 2008, IFFCO announced a $1bn (INR46.6bn) expansion plan to increase the plant’s ammonia capacity to 2,200t/d and urea capacity to 4,000t/d. The new urea facility will use technology provided by Snamprogetti and the ammonia plant will use technology licensed from Haldor Topsoe.

The expansion, however, has been delayed as the government is yet to allocate additional gas supply to run the new units. The delay is expected to increase the project cost by $111m (INR5bn).

Kellogg steam reforming process

Ammonia is produced at the plant by Kellogg’s steam reforming process, which uses natural gas as feedstock. The first step in the process includes purification of gas in a desulphuriser.

The purified gas is then mixed with steam and partially reformed in the primary reformer. This mixture is then sent to the secondary reformer and treated with air.

Gases released from the secondary reformer include nitrogen, hydrogen, carbon monoxide (CO) and carbon dioxide (CO2). These gases are treated in the shift converters to convert carbon monoxide into carbon dioxide.

The processed gas is then passed through a CO2 absorber to remove the carbon dioxide and produce methyl diethyl amine (MDEA) solution. The MDEA solution is passed through a series of low pressure and high pressure flash vessels and again passed through the CO2 absorber to remove carbon oxides.

Any remaining carbon oxides are removed by passing the process gas through the methanator.

The resultant process gas mainly contains nitrogen, hydrogen and small amounts of CO, CO2 and water. These oxide components are removed by the ammonia dehydrator unit.

The final step includes passing the process gas through two ammonia synthesis converters. Nitrogen and hydrogen present in the process gas combine in the converters to form ammonia.

The converted ammonia is condensed by passing it through a series of chillers and coolers. The condensed ammonia is further purified by passing through ammonia flash drums.

The urea produced is sent to the urea plant or to the atmospheric storage tanks.

Stamicarbon’s CO2 stripping process

Urea production at the plant involves the use of Stamicarbon’s CO2 stripping process. Ammonia and carbon dioxide, the feedstock for the production of urea, are supplied by the ammonia plant.

The feedstock is passed through the synthesis section containing a reactor, stripper, carbamate condenser and a scrubber. The synthesis section produces a urea solution which is concentrated to 82.6% in the pre-evaporator.

The urea solution is converted into molten urea by passing it through two evaporators. The molten urea is then passed through a prill bucket placed on top of the prill tower.

The prill bucket contains small holes and rotates at a speed of 210-230 rotations a minute. The rotation of the bucket causes the molten urea to coagulate during its fall in the prill tower.

The urea is then transferred to the prill cooling system through a conveyor. From the cooling system, the urea is sent to the bagging facility or to the urea silos.

Process technology used in IFFCO’s Kalol unit

Liquid CO2 and dry ice are produced using technology supplied by Germany’s Borsig.

“In 2008, IFFCO announced a $1bn (INR46.6bn) expansion plan.”

Liquid CO2 is produced using the high pressure carbon dioxide released from the urea plant. The carbon dioxide is purified by passing through a bed of silica gel / alumina balls to remove water vapour.

It is then passed through an activated charcoal bed to remove odour forming organic substances. The pure CO2 produced is then cooled, condensed and stored in liquid storage tanks.

Dry ice, the solid form of CO2 liquid, is produced by cooling liquid CO2 in a revert gas heat exchanger. Liquid CO2 passing through the exchanger is converted into the form of snow drops. These drops are pressed in the pressing chamber using piston presses to form dry ice blocks. The blocks are wrapped in craft paper and stored to prevent evaporation.

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