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Overview
Urea

The Urea Plant is designed based on the CO2 stripping process, licensed by Stamicarbon b.v., the Netherlands. Ammonia (NH3) and Carbon Dioxide (CO2) are the main raw materials for Urea production. Initially, NH3 and CO2 are passed through a High Pressure Condenser where Ammonium Carbamate solution is formed. This is sent to an Autoclave where a portion of it gets converted to Urea. The unconverted Ammonium Carbamate is stripped into NH3 and CO2 gases in a High Pressure Stripper using fresh CO2 and then recycled back to the HP Condenser along with fresh Ammonia and dilute Ammonium Carbamate to again form a concentrated solution of Ammonium carbamate. This is a continuous cycle.

The Urea solution that comes from the Stripper is separated and concentrated in a low pressure section consisting of a rectification column, a flash vessel, pre evaporator and two stages of evaporation. The molten Urea solution coming from the final evaporator is taken to a revolving perforated prill bucket at the top of the prill tower. The Urea solution is sprayed in the form of fine droplets by rotation of the prill bucket. The droplets solidify into prills before reaching the bottom of the prill tower as they come in contact with an upward flow of air. The prills are collected and sent for bagging or alternatively for storage in the Silo.

The Urea plant was revamped in March 2002. This resulted in improvement in the product quality with a marginal increase in production quantity. For better control of the operations, a new Distributed Control System replaced the obsolete pneumatic controls. In 2006, HP Scrubber, the ammonia recovery unit, was replaced with MP Scrubber which can be operated at low pressure and Hydrogen converter was installed to improve the overall process safety.

The Company’s original industrial license was to produce 3,40,000 MT of Urea annually. Subsequent to the revamp, the Government of India has recognised the enhancement in the capacity to 3,80,000 MT per annum. Maximum production of 3,80,000 MT has been achieved in the year 2002-03.
 
Di Ammonium Phosphate (DAP)

To diversify into phosphatic fertilizers, the Company commissioned a DAP Plant in 1986 with a licensed capacity of 1,38,000 MT per year. Imported Ammonia and Phosphoric Acid (H3PO4) are the main raw materials. Toyo Engineering Corporation, Japan and Toyo Engineering India Ltd., Mumbai, were the contractors. A shore terminal was set up to receive and store these materials.

Ammonia and Phosphoric Acid react in a Preneutraliser (reactor) to produce slurry of Mono Ammonium Phosphate (MAP). The slurry is then sprayed in a rotary granulator
on a rolling bed of recycle seed material with simultaneous ammoniation to produce DAP. The wet granules obtained are dried to less than 1% moisture in a rotary drier and sent for screening. The product is cooled in a fluidised cooler and bagged.

In March/April 2002, the Plant was modernized by installing a pipe reactor system in the granulator with technology from Incro S.A., Spain. The controls have been upgraded to a Distributed Control System. The advantage from the revamp is the flexibility to produce additional fertilizer grades (i.e., 20:20:00:13 and 16:20:00) apart from DAP of a better quality in terms of size, shape and crushing strength.

With the introduction of improved operation and maintenance techniques and the resultant increase in the on stream efficiency of the plant, production of 2,60,000 MT per annum of DAP and complex fertilizers can be achieved.

Ammonia (an intermediate product for urea production)

ICI, U.K, technology utilizing steam naphtha reforming process.

The erstwhile engineering firm, Humphreys & Glasgow Ltd., London (now merged with Jacobs Engineering, U.S.A.), designed, engineered and constructed the Ammonia and Urea plants.

Naphtha, a petroleum product, is the main raw material for producing Ammonia. It is first desulphurized and passed through primary reformer tubes, filled with catalyst,
along with the required quantity of steam to yield a gaseous mixture of Hydrogen (H2), Carbon Monoxide (CO), Carbon Dioxide (CO2) and Methane (CH4). The heat needed to complete the reaction is supplied by burning the fuel Naphtha in the Primary Reformer furnace. The gas is then passed through the Secondary Reformer along with the required quantity of air and steam to yield CO2. H2 and Nitrogen (N2). The remaining CO is converted into CO2 in two stages and then separated for use in Urea synthesis. The product gases consisting of N2 and H2 are compressed to about 180 kg/cm2 pressure and passed through the Ammonia Synthesis Converter at about 480’C to produce gaseous Ammonia. This is further condensed and the liquid Ammonia obtained is either sent to the Urea plant or stored in the Horton Sphere.

The annual production capacity is 217,800 MT. (The highest annual production of 227,028 MT has been achieved in the year 2005-06.)

Ammonium Bi Carbonate (ABC)

The plant is capable of producing 15,000 MT per year of ABC and is based on indigenous technology. The main raw materials, NH3 and CO2, are first bubbled through water in a carbonation tower to form Ammonium Carbonate solution. This solution is fed to a Bi carbonation tower where it is further reacted with CO2 to form slurry of ABC. This slurry is pumped to a centrifuge to separate crystals of ABC from the mother liquor. The wet ABC crystals are dried in a rotary drier and then bagged.

Sulphuric Acid and Utilies
 
Manufacture of Sulphuric Acid
The Sulfuric Acid Plant technology is based on double conversion, double absorption contact sulfuric acid process using powder sulphur as raw material. It consists of three principal steps:
  1. Combustion of Sulfur to produce Sulfur Dioxide gas. S + O2 = SO2
  2. Conversion of Sulfur Dioxide gas to Sulfur Trioxide gas in the presence of vanadium catalysts. SO2 + ˝ O2 = SO3
  3. Absorption of Sulfur Trioxide in sulfuric acid and reaction of water with Sulfur Trioxide to form Sulfuric Acid. SO3 + H2O = H2SO4
Raw sulphur is melted in pits with the help of steam coils using LP steam of 5kg/cm2. This raw sulphur contains impurities like ash and organics which are removed by filtration using ‘Leaf Filter’. The molten sulphur, stored in a Clean pit at 135oC is charged to the furnace through a sulphur gun which atomises the sulphur. Dry combustion air is introduced into the furnace. Sulphur burns to form sulphur-dioxide.

Sulphur-dioxide is converted into sulphur- trioxide using Vanadium Pentoxide as catalyst in first three beds of conversion maintaining gas inlet temperature of 410oC to 450oC at each stage. Third Converter bed outlet is taken to IAT (Intermediate

Absorption Tower) where SO3 is Absorbed in sulphuric acid to produce sulphuric acid. The SO3 free gases left after this absorption are taken through heat exchanger for further conversion in fourth and fifth beds . Thus five beds of catalyst are used in 5 stages to achieve maximum conversion.
 
The advantage of this technology is that much better SO2 to SO3 conversion efficiencies are obtained due to this intermediate absorption, since the ‘product’ formed i.e. SO3 has been removed and so the reaction tends to proceed more towards the product side. It is possible to get conversion efficiencies up to 99.8% compared to about 98% of earlier single absorption technology. Such high conversion efficiencies naturally result in lower SO2 emissions to the environment from the process.

Conversion from SO2 to SO3 is Exothermic and heat is removed at each stage to
produce steam. Fifth Converter bed outlet after complete conversion (99.8%) passes through final absorption tower to produce Sulphuric acid. Hence the process is called Double Conversion Double Absorption Process.
 

Utilities

The following systems cater to the requirement of different plants:
  • Cooling water system - 16,600 m3/h circulation rate.
  • Water De-mineralizing plant - 120 m3/h capacity.
  • Nitrogen plant - 650 Nm3/h of gaseous nitrogen and equivalent 50 Nm3/h of liquid nitrogen.
  • Instrument Air Compressor with Instrument Air drier of 1,500 Nm3/h capacity.
Product Handling
There are in all four streams for Urea and three streams for phosphatic fertilizers for bagging and dispatch.

Auxiliary Boiler
The Ammonia and Urea plants are supplemented with an auxiliary boiler of 60 MT/h steam capacity at 75 kg/cm2 pressure and 480°C.

Purge Gas Recovery Unit (PGRU)
The productivity of the Ammonia plant was increased by installing a PGRU in May 1984 of 4,800 NM3/h.
 
Captive Power Plant (CPP)
To overcome the frequent interruptions in power supply, resulting in equipment failure and wastage of energy during shut down and start ups of the plants, a Captive Power Plant with eight Wartsila Diesel Engine was commissioned. This has ensured smooth functioning and improved life of all the plants and critical equipment through the steady supply of quality power captively produced. The power plant meets the total power needs (35 MW) for the entire complex.

 
Imported Ammonia & Phosphoric Acid Terminal (IAT)
The terminal facilitates direct unloading from a ship. Ammonia is stored in a 10,000 MT atmospheric pressure storage tank. Phosphoric Acid is unloaded into two tanks of 8,000 MT each capacity.




 
 
Imported fertilizer handling facility
MCFL has installed Imported Fertilizer handling facility. The fertilizer imported through ships will be brought from the port by trucks/tippers and discharged inside the Bulk Storage Silo or to a receiving Hopper outside the silo for bagging and dispatch. The Silo capacity is 20,000 MT.

Imported Material transfer from silo to bagging plant - A partly underground receiving hopper of capacity 20 MT has been provided outside the silo for receiving the material directly from trucks. Pay loaders will be used for reclaiming previously dumped material inside the silo into the receiving hopper. A set of conveyors of capacity 150 tons per hour is provided to transfer material from receiving hopper to bagging plant.

Bagging Plant (imported fertilizer) - The material brought from port is transferred to the Bagging plant through bulk handling conveyors of capacity 150 tons per hour. The Bagging plant has two streams of 60 tons per hour capacity each which can either be loaded to wagons or truck.

The bagging capacity is 2000 MT per day for 2 streams.

 
 
Water Reservoir
The entire complex requires 2 Million Gallons (MG) per day of clarified water which is supplied by the Mangalore City Corporation from the Netravathi River. In order to overcome the problem of water shortages, especially during summer months, two reservoirs of 6 MG and 18 MG capacity were constructed within the factory premises.
Bulk Storage (Silo)
There are two separate silos to store 30,000 MT and 10,000 MT of Urea and Phosphatic fertilizers respectively.

 
 
 
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