Pretreatment of Process Condensate with Ammonia Degassing in CAN Fertilizer Production

摘要

In the production process of calcium ammonium nitrate (CAN) fertilizer, process-condensate isgenerated with a high content of ammonium nitrogen. Such high mass concentration of ammoniumnitrogen (approximately 2 g L–1) significantly burdens the operation of the wastewater treatmentplant, where the process condensate is treated by method of ion exchange. At CAN 1 Plant,a degassing system for process condensate was built. After pretreatment, the concentration ofammonium nitrogen in the process condensate was reduced to less than 500 mg L–1.Before upgrading with degassing system, the process condensate from CAN 1 Plant was collectedin tank TK 17 301, from which it was pumped to the wastewater treatment plant to be treated bythe method of ion exchange. When CAN 1 Plant is in normal operation, 10 m3h–1 of process condensateis formed with pH around 10, and temperatures around 50 °C. The degassing system ofprocess condensate consists of a new tank, TK 17 504, which is connected with new pipeline tothe tank TK 17 301. The process condensate input was transferred from the old to the new tank,TK 17 504. A new pump was installed for regulation of process condensate and bursting abovethe condensate level.Additional stimulation for ammonia degassing followed, after the return of 12 bar steam condensateinto the tank TK 17 504. Consequently, the process condensate temperature increasedto 80 C. Degassed ammonia is introduced into the existing system for washing gases and returnsinto the process of fertilizer production.By degassing ammonia from the process condensate at CAN 1 Plant, 10.7 kg h–1 of ammonia returnsinto the fertilizer production process.Additionally, there has been an improved performance of the wastewater treatment plant, so thatin December 2010, the volume of treated wastewater was almost 80 000 m3 which is an increaseof 86 %.