Study On The Capacity Expansion Technology Of Urea System

Urea is a nitrogen fertilizer with the highest nitrogen content among the nitrogen fertilizer products,and it is the most widely used chemical fertilizer in agriculture.Meanwhile,urea also has extensive application in other fields such as medicine and industry.Shandong Hualu-Hengsheng Chemical CO.LTD built a number of urea units,including a device adopting carbon dioxide stripping process whose capacity is 400 kt/a constructed at 2005 and 2010.To tap the potential of the units and realize productivity improvement,the company decided to implement capacity expansion technology modification on the two units with carbon dioxide stripping process.Therefore,this thesis carried out research on the two 400 kt/a sets of urea devices,and the work is as follows.1.Aiming at the actual condition of Hualu-Hengsheng,we made a technical reform process routes and solutions allowing production and construction coexisting.Through adding Medium-pressure System,adopting high pressure system synthesis ? medium pressure system separation ? low pressure system separation process,step separation and recovery,the circulation volume of ammonium carbamate was reduced.2.Adopting a new type of combined medium pressure decomposition tower technology,the equipment number was effectively reduced.Meanwhile,the rate of equipment utilization was improved,and the area of the equipment was also reduced.3.Developing two steps dehydrogenation process,the use cycle of the catalyst was extended from 4-5 months to 38 months.4.A large granule unit with 200kt/a of production capacity was newly built.Through process reformation and application of new technology,the product quality and device stability problems was solved,controlling more than 85%large urea particle between 2.8 mm-4.0 mm with further improvement in product quality.