The Process Design Of Ammonia Stripping Urea

At present，there are three main processes of urea including the CO2Stripping processdevised by Stamicarbon company in Netherland, NH3Stripping process by Saipemcompany in Italy and ACES process by Toyo company in Japan. NH3Stripping process issimilar to the CO2Stripping process. By increasing the ratio of ammonia-to-carbon dioxidein the urea reactor, there is an excess of ammonia in Stripper, so it can use ammonia asself-stripping agent. In the past5years, there is about70%new Urea Projects usingAmmonia Stripping process. From1980s, it is imported into China. The Saipem AmmoniaStripping process is used to design1000MTPD Urea Project in this article.There are several section in ammonia Stripping process including the CO2compress,urea synthesis and NH3, CO2recovery at high pressure, urea purification and NH3, CO2recovery at medium and low pressures, urea concentration, waste water treatment, ureaprilling. Under almost the same pressure of the Urea Reactor, the effluent solution fromUrea Reactor enters in the Stripper tower heated by the2.45MPa steam, then a part of theunconverted carbonates is decomposed into NH3and CO2. Ammonia and carbon dioxidevapors from the Stripper top, after mixing with the carbonate recycle solution from mediumpressure section, are condensed, at the same pressure level of the stripper itself, in the HighPressure Carbamate Condenser, thus producing the low pressure steam which is used indownstream sections. The solution leaving the bottom of the Stripper, E-01, enters mediumand low pressure section. More carbonate is decomposed and more ammonia flash.Then the solution enters vacuum preconcentrator,1stvacuum system,2stvacuumsystem. At last the urea melt (99.75%by wt) is sent to prilling section。Ammoniaform medium pressure decomposed gas is sent back synthesis system.The cost of Urea is about1323CNY/t by the ammonia stripping process. It islower than the market price (1700CNY/t).