Deep hydrolysis of urea to achieve zero discharge of sewage

December 29, 2018

On January 6, a message from Shijiazhuang Zhengyuan Fertilizer Co., Ltd. came out. The deep urea waste hydrolysis project jointly undertaken by Hebei Zhengyuan Chemical Engineering Design Co., Ltd. and Shijiazhuang Zhengyuan Tower Equipment Co., Ltd. was successfully put into operation. The operating results show that Zhengyuan’s self-developed low-pressure hydrolysis gas extraction energy-saving process effectively solved the nitrogen pollution problem during the production process, and achieved zero discharge of sewage. The ammonia content in the residual liquid was 3×10-6, and the urea content was almost 0, tons of urea ammonia consumption reduced 15 kg, daily production of urea increased by about 10 tons, process wastewater can also be used as boiler feed water.

The process adopts a new type of vertical sieve plate technology exclusively used by Zhengyuan to manufacture the internal parts of the hydrolysis tower. The gas and liquid in the tower are fully in contact, the liquid residence time is long, and the hydrolysis efficiency is high. The hydrolysis tower and the desorption tower are combined into one, and the wastewater from the ammonia plant can be treated together with the urea process condensate. The ammonia, carbon dioxide, and water recovered in the hydrolysis unit are returned to the urea plant's medium pressure system in liquid form, greatly reducing the load on the circulatory system. The heat at the top of the tower is used for the urea evaporation system, energy is recovered, power consumption is reduced, and energy consumption is reduced. At the same time, the equipment used reasonable materials and structures. According to a conservative estimate, the investment amount has been reduced by about 1/3 compared to similar domestic equipment.

According to Xu Liangming, a senior engineer of Zhengyuan Chemical Design Company, China's small and medium-sized urea plant will produce about 400 kilograms of effluent per ton of urea. This part of the effluent contains about 5% of ammonia and 2% of urea. In order to effectively recover the ammonia and urea from the wastewater, the majority of companies have adopted analytical methods to control the ammonia in the effluent to be below 0.07%, but the analytical process cannot recover the urea. Can not meet the standard emissions. Although some enterprises do not discharge waste water, the ammonia nitrogen in the circulating water is likely to cause corrosion and blockage of the pipeline, thus affecting the system operation. For enterprises that do not have zero emission conditions, the excessive discharge of ammonia-based wastewater has become a major issue affecting the continued survival of enterprises.

It is understood that deep hydrolysis technology is an effective solution to the process of urea production process nitrogen pollution ** pollution technology, but the existing technology due to technical defects in the country, the operation effect is not very satisfactory, and high investment so that many companies daunting.

At present, in addition to Shijiazhuang Zhengyuan fertilizer production project, Shijiazhuang Bopo Zhengyuan Fertilizer Company's urea deep hydrolysis project is being debugged.

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