06-09-2012, 01:12 PM
Aonla Unit - Urea Plant
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Two streams of Urea Plant each having capacity of 1515 MTPD have been provided in Aonla-I and Aonla-II. Urea process is based on Snamprogetti, Ammonia stripping process. Ammonia and Carbon dioxide obtained from Ammonia Plants are sent to Urea reactor operating at 150 ata pressure and 180 0C temperature. In Urea reactor, Ammonia and Carbondioxide react to form Ammonium carbamate, a part of which dehydrates to Urea. Reaction products from Urea reactor flow to a steam heated H.P. stripper where most of the unconverted carbamate gets stripped off as gaseous Ammonia and CO2. Urea solution leaving the bottom of the stripper still contains some amount of carbamate.
Further purification of urea takes place in Pre decomposer, medium pressure decomposers and low pressure decomposers. Vapours of ammonia and carbondioxide obtained from the above purification sections are converted into ammonium carbamate and recycled back to urea reactor for the production of urea. Pre concentrator and Vacuum concentrators are provided to concentrate further the urea solution to 99.8 percent. Urea melt (99.8% conc.) from the concentration sections is pumped to the top of the natural draft prilling tower and sprayed by means of rotating prill bucket. The fine droplets, while descending through the tower, come into contact with cold air and solidify to form prills. Product urea from the bottom of the prill tower is sent to urea silo or product handling plant.
Besides main Ammonia and Urea plants, Aonla Unit has Product Handling Plants to bag urea, steam and Power Generation plant to provide steam and electricity for driving different machines, DM water plant to produce high purity water for boiler, Instrument air and Service air compressors, Inert gas Generation plant, Liquid ammonia storage and bulk Urea storage (silo) etc.