Experimental Study On The Effect Of Metal Ion In Char-NO Reaction

Coal is the chief energy in China. The combustion of coal discharge large quantities ofpollutants, in which the NOx is serious harm to environment and human’s health. Manygovernments begin to control the NOXemissions by legislation. The coal-fired electricpower plant is the main fixed source of NOx. The reburning, because of its significantadvantages, becomes a choice among many technologies to reduce NOx emissions of powerplant. The heterogeneous reaction between char and NO, which has an important position in thereaction mechanism of using pulverized coal to reburn, is quite a degree of concern.In this paper, a kind of bituminous coal and lignite were selected, respectively. Thedeashed coals were obtained by demineralized with acid washing. The chars were preparedby devolatilizing the deashed coals and their original coals in a horizontal quartz reactor at1000℃. Pore size distribution and micro-morphology of the samples were investigated andanalyzed. The result showed that the original char and deashed char from lignite had moremicro-morphology than that from bituminous.NO reduction by coal and chars were investigated in a small quartz fluidized bedreactor. It was found that the heterogeneous reaction between char and NO was the mainreaction in the NO reduction by coal. The influence of temperature, mineral matter in thecoal and micro-morphology to the char-NO reaction was studied. The results showed thatthe reduction of NO was increased with temperature for all chars. The mineral matter in thedifferent coals had different influence to the reaction. When the chars’ micro-morphologyincreased, the percent of NO reduction increased in step.The catalytic activities of sodium, calcium and iron on the reaction between char andNO were studied by adding metal ion to the deashed char. The results showed that Fe hadthe most catalytic activity. Adding1%Fe was found to have the best effect when studiedthe influence of the amount of Fe added. The influence of O2and CO was researchedthrough the change of reaction atmosphere. It was found that a little amount of O2couldpromote the char-NO reaction, but excessive O2hindered. CO enhanced the char-NOreaction remarkably.