New breakthrough achieved in China’s urea production technology

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New breakthrough achieved in China’s urea production process Source: http://www.fert.cn China Fertilizer Network 2009-9-29 7:48:39 Keywords: Urea At the 18th National Annual Conference of Urea Plants held last week, the new urea production process developed by Sichuan Jinxiang Chemical Group attracted great interest from the delegates present. This technology can increase the carbon dioxide conversion rate in traditional urea production by 5 percentage points, reaching over 73%. Compared with CO2 stripping units built during the same period, it can save more than 30% in investment costs, with steam consumption reduced to 950 kilograms per ton. More than 10 urea production enterprises conducted on-site outcome discussions with Jinxiang Chemical. According to Li Xuchu, deputy general manager of Jinxiang Chemical Group, a urea plant with a capacity of 1,000 tons per day, built using this new process, was put into operation at Jinxiang Chemical in February this year. As of September 21, the device had been in operation continuously for over 7 months. It reduced the ammonia consumption per ton of urea by 10 kilograms compared to the full-circulation method using modified aqueous solutions; steam consumption was reduced by 315 kilograms, electricity consumption by 21 kilowatt-hours, and circulating water usage by 60 cubic meters. This resulted in annual savings of over 20 million yuan in operating costs. Compared with the CO2 stripping method, ammonia consumption per ton of urea is reduced by 5 kilograms, steam consumption is reduced by 115 kilograms, electricity consumption is reduced by 5 kilowatt-hours, and circulating water consumption is decreased by 27 cubic meters, resulting in annual savings of 8.73 million yuan in operating costs. The carbon dioxide conversion rate is an important process parameter in urea production, as it directly affects steam consumption and urea yield; both domestically and internationally, efforts are being made to further improve this conversion rate. At the same time, safe production is also an issue that urea manufacturers have long paid attention to; due to the shortcomings of traditional processes, chemical explosion accidents occur from time to time in urea production facilities in China. To overcome these challenges, the technical staff at Jinxiang Chemical Technology improved the traditional full-circulation aqueous solution method in the new urea production process. Urea synthesis, by utilizing a liquid-phase heat exchange synthesis tower, improves the CO2 conversion rate and safety factor, while also preventing chemical explosion accidents in the urea synthesis tower ； Pre-distillation and combined heating are employed in medium-pressure decomposition, which improves the decomposition rate at medium pressure and reduces investment costs ； Medium-pressure recovery utilizes a low water-to-carbon ratio and multi-stage absorption; ammonia condensation is achieved with evaporative ammonia coolers, and the exhaust gases are subjected to thorough purification, which reduces consumption and prevents explosions of the exhaust gases ； Most of the heat required for low-pressure decomposition is supplied by waste heat, and one-step condensation is used in low-pressure absorption, which increases the concentration of dimethyl liquid and facilitates system hydrostatic balance. It is reported that this process is applicable not only to the construction of new plants of various scales but also to the renovation of existing urea plants. (Author: Yi Rou; Editor in charge: Bai Yun)