NH_(4)HCO_(3)/尿素溶液SCR脱硝制氨模拟优化

Simulation and analysis of the ammonia production process for SCR denitrification with NH_(4)HCO_(3)/urea solution

为了加强对电力行业危险化学品的治理改造,急需研究开发安全高效经济的新型脱硝还原剂。NH_(4)HCO_(3)是我国第二大氮肥,使用安全且价格便宜,是潜在安全高效的新型选择性催化还原(selective catalytic reduction,SCR)脱硝还原剂。通过对比尿素水解和NH_(4)HCO_(3)溶液分解过程,对利用NH_(4)HCO_(3)作为脱硝还原剂的技术方案进行了可行性研究,分析了影响溶液分解过程的关键因素,并提出了工程应用技术方案。通过对原料分解过程建模,验证了模型在模拟制氨反应时的可靠性,并对比了影响2种原料制氨的反应速率和反应能耗的关键因素,探究了提高NH_(4)HCO_(3)制氨过程经济性的方案方法。模拟结果表明,提高反应温度对尿素水解和NH_(4)HCO_(3)分解均有利,升高压力对尿素水解反应有利,而对NH_(4)HCO_(3)分解不利,因此NH_(4)HCO_(3)溶解分解过程更适合在常压下进行;采用传统湿法制氨工艺时,NH_(4)HCO_(3)作还原剂可降低14%的原料成本,但其在分解过程中会由于水蒸发而消耗大量热能,热耗达到尿素水解法的2.7~3.5倍;通过在工艺中加入物流循环并降低NH_(4)HCO_(3)的一次转化率至40%,可以限制水蒸发吸热,降低热耗至尿素水解法的1.5~1.6倍;由于NH_(4)HCO_(3)原料成本更低,优化后的NH_(4)HCO_(3)湿法制氨工艺经济性更好。

In order to fortify regulations for potential hazards in the power industry,there is urgent need to research into and develop advanced efficient reductant for the denitrification unit.Ammonium bicarbonate(NH_(4)HCO_(3))is the second widest used fertilizer in China with no safety issue and lower price than urea,and therefore a potentially efficient material for denitrification.The article compares the urea hydrolysis and the decomposition process of ammonium bicarbonate solution,and studied the potential of utilizing NH_(4)HCO_(3)as a denitrification reductant.The key factor affecting the decomposition process is analyzed and the practical engineering solution is raised.Through the simulation of the decomposition process,the reliability of the ammonia synthesis reactions is verified.The key factors affecting reaction rate and energy consumption is analyzed,and the methods to improve the economic efficiency of NH_(4)HCO_(3)decomposition process is explored.The results show that increasing the reaction temperature and pressure is conducive to increasing the NH_(3) yield of urea hydrolysis,while temperature for NH_(4)HCO_(3)solution decomposition to will increase with increasing pressure,making it more suitable for carrying out at atmospheric pressure.In the traditional ammonia production process,the heat consumption for NH_(4)HCO_(3)solution decomposition roots in the water evaporation,which is 2.7-3.5 times that of the urea hydrolysis method.By introducing flow circulation and reducing the initial conversion rate of NH_(4)HCO_(3)to 40%,heat consumption is reduced to 1.5-1.6 times that of the urea hydrolysis method.With lower raw material cost of NH_(4)HCO_(3),the optimized NH_(4)HCO_(3)decompostion process has better economic efficiency.