Experimental study on the activation of coal gasification fly ash from industrial CFB gasifiers

Coal gasification fly ash(CGFA)is an industrial solid waste from the coal circulating fluidized bed(CFB)gasification process,and it needs to be effectively disposed to achieve sustainable development of the environment.To realize the application of CGFA as a precursor of porous carbon materials,the physicochemical properties of three kinds of CGFA from industrial CFB gasifiers are analyzed.Then,the activation potential of CGFA is acquired via steam activation experiments in a tube furnace reactor.Finally,the fluidization activation technology of CGFA is practiced in a bench-scale CFB test rig,and its advantages are highlighted.The results show that CGFA is characterized by a high carbon content in the range of 54.06%–74.09%,an ultrafine particle size(d50:16.3–26.1 μm),and a relatively developed pore structure(specific surface area SSA:139.29–551.97 m^(2)·g^(-1)).The proportion of micropores in CGFA increases gradually with the coal rank.Steam activation experiments show that the pore development of CGFA mainly includes three stages:initial pore development,dynamic equilibrium between micropores and mesopores and pore collapse.The SSA of lignite fly ash(LFA),subbituminous fly ash(SBFA)and anthracite fly ash(AFA)is maximally increased by 105%,13%and 72%after steam activation;the order of the largest carbon reaction rate and decomposition ratio of steam among the three kinds of CGFA is SBFA>LFA>AFA.As the ratio of oxygen to carbon during the fluidization activation of LFA is from 0.09 to 0.19,the carbon conversion ratio increases from 14.4%to 26.8%and the cold gas efficiency increases from 6.8%to 10.2%.The SSA of LFA increases by up to 53.9%during the fluidization activation process,which is mainly due to the mesoporous development.Relative to steam activation in a tube furnace reactor,fluidization activation takes an extremely short time(seconds)to achieve the same activation effect.It is expected to further improve the activation effect of LFA by regulating the carbon conversion ratio range of 27%–35%to create pores in the initial development stage.

Experimental study on the partial preheating combustion characteristic of Yankuang coal sludge

Coal sludge is a seriously polluted solid waste,and the rational utilization of its resources has long being an undoubtedly important research topic.This paper mainly studies the coal sludge partial preheating characteristic,combustion characteristic and the process of migration and conversion of nitrogen with preheating combustion technology.The experimental results indicate that most of the elements in the coal sludge are released during preheating,and the ratio of the fuel-N converted to the N_(2),NH_(3) and HCN are 75.5%,6.74%and 0.64%,respectively.Compared with the coal sludge,the BET surface area and cumulative pore area of preheated char are increased.The surface of preheated char is loose and porous with many fine particles,while raw coal is dense with larger particles.Meantime,the quantity of carbon defect structure,the active sites and the reactivity of preheated char are all increased.In the whole process,the NO_(x) emission is about 156 mg/m3(@6%O2),the ratio of fuel-N converted to NO_(x) was 2.98%,and the combustion efficiency is 96.5%.This experiment results will play a vital role in efficient and clean utilization of coal sludge.