Formation of nitrogen compounds during coal water slurry gasification in an entrained flow gasifier

摘要

A laboratory gasifier with the opposed multi-burners (OMB) was used to investigate the formation of nitrogen compounds during coal water slurry (CWS) gasification. Various axial and radial concentrations of HCN, NH3, NO and N2 (nitrogen compounds) in the gasifier were measured. The concentrations of HCN, NH3 and NO (nitrogen pollutants) were maximal at the nozzle plane and decreased along the axial distances. Moreover, the ordering of nitrogen compounds in aft-region was N2>HCN>NH3>NO. An increase in O2/C ratio tends to favour the formation of N2. Flow field distribution resulted in the radial concentrations uniform at the exit and low near the side-wall at other axial positions. The results showed the majority of nitrogen pollutants formed from coal volatile nitrogen during the rapid devolatilization. HCN and NH3 formed mainly from devolatilization at the nozzle plane but were not thoroughly converted from the reduction of NO. H2O in CWS played a vital role in converting coal-N into NH3 and HCN by providing H radical.