engleski

Absorption of the exhaust gases in urea production

Fertilizer industry Petrokemija d.d. Kutina suggested reconstruction of its unit for ammonium and carbon dioxide absorption which is part of urea production plant. The goal of the reconstruction project is to reduce ammonium and overall levels of exhaust gases. Current measurements of the exhaust gases show that ammonium levels in the air are much in excess of those laid down in the “ By-law on the Limit Values of Air Emissions of Pollutants from the Stationery Sources” . The existing absorption unit is undersized and incapable of further reduction of ammonium and overall levels of the exhaust gases. Substantial amounts of ammonium, together with carbon dioxide and steam from the recirculation section are released into the atmosphere and irreversibly lost. In the basic process design the exhaust gas is treated in the absorber unit comprising a packed column with accessories, heat exchanger and pumps. The scrubbing agent is aqueous ammonium solution from the evaporation section and process condensate from the desorption section. The aqueous ammonium solution is used in unrestricted amounts, whereas the use of the process condensate is limited to 2 m3/h. The suggested reconstruction would reduce the concentration of ammonium (from 650 mg/m3 to less than 50 mg/m3) and the overall amount of the exhaust gas (from 3500 m3/h to 1950 m3/h). Besides emission abatement, some economic benefits can be achieved through the amount of waste ammonium being recycled in the process (cca 7, 5 t NH3 / y). Process parameters that influence ammonium concentration in the exhaust gas, consumption of cooling water and power, flow rates of aqueous ammonium solution and the process condensate, and ratio of the saturated ammonium solution recycled from the bottom of the absorber vs. fresh solution were analyzed. Process sensitivity was also analyzed.

exhaust gas; absorption; reconstruction

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