水煤浆气化过程中N元素分布规律的研究

Distribution regularity of element N in coal-water slurry gasification process

以多个工程实例为基础,研究了水煤浆气化过程中,N元素的转化和含N物质在气化及后续流程中的分布规律。研究发现,煤中N元素在气化过程中99.95%以上转化为N2(85%—98%)和NH3(4%—15%)。NH3随灰水和变换凝液在气化系统内部循环,是造成铵盐结晶和外排废水氨氮质量浓度超标的主要原因。提出了改进的变换汽提塔流程,在汽提塔中实现NH3和酸性气的分步汽提,从汽提塔中段回收粗氨产品,可以显著降低气化系统中NH3的质量分数,解决了铵盐结晶和外排废水氨氮质量浓度超标问题,同时取得了可观的经济效益。

The conversion of element N and distribution regularity of nitrogenous substances in coal-water slurry gasification process was studied based on several practical projects. N2 accounts for 85%-98% of the element N conversion product in the gasification process, while NH3 accounts for 4% -15%. NH3 dissolved in grey water and shift condensate circulates inside the gasification system, which causes the crystallization of ammonium salt and excessive ammonia in waste water. A new stripper process in the shift section was proposed to solve these problems. Ammonia and acid gas were stripped in one stripper simultaneously. Raw ammonia product was obtained and drawn from the middle of the stripper, so the ammonia accumulated in gasification system was reduced significantly. This improved method can eliminate the crystallization of ammonium salt and excessive ammonia in waste water, thus achieving the considerable economic benefits at the same time.