An experimental study on the characteristics of ammonia/coal mild gasification-combustion and the Fuel-N transformation
Ammonia(NH3)is a carbon-free and hydrogen-rich fuel.NH3 co-firing in coal-fired boiler is an effective ap-proach to reduce carbon emissions from the combustion source.However,it can lead to problems such as high NOx emis-sions and poor coal burnout.To address the issues above,this paper investigated the Fuel-N conversion and NOx emis-sions during co-firing 20%NH3 in gasifier(G-20%NH3)and in combustor(C-20%NH3)using a self-built mild gasification-combustion experimental rig.The research found that the co-firing NH3 in the gasifier can decrease the gasifier temperat-ure.However,it has little effect on the coal gasification reactions in gasifier.Compared with a pure coal condition,the conversion ratio of coal-nitrogen was only reduced by 3.64%,and the conversion ratio of volatile matter and fixed carbon decreased by only 0.70%and 2.54%,respectively.Besides,the conversion of NH3 in the gasifier can reach 69.55%during the condition of G-20%NH3.The 68.88%of total fuel-N was conversed to N2 in the gasifier,with NH3-N converting to N2 was 67.73%in G-20%NH3.In addition,the NH3 co-firing in the gasifier promoted the transformation of coal-N and NH3-N to HCN,with the value of 0.36%.Moreover,the coal pyrolysis in the gasifier promoted the NH3 pyrolysis.Compared with pure coal,the NH3 co-firing in the gasifier increased the H2 concentration at the outlet of the gasifier by 69.23%than that of pure coal.The NH3 co-firing also decreased the temperature during the preliminary stage of combustion.Com-pared with pure coal,the NH3 co-firing in the gasifier and combustor decreased the temperature peak by 46℃and 62℃,respectively.Simultaneously,the NH3 co-firing delayed the occurrence of temperature peaks.Additionally,the NH3 co-fir-ing delayed the gasified char combustion in the combustor.The average temperature in the burnout zone increased by 135.8℃and 72.8℃during G-20%NH3 and C-20%NH3,respectively,compared to PC.It was more conducive to the burnout of pulverized coal.The NH3-cofiring in combustor had more significant promoting effects on the burnout of pul-verized coal,in which the unburned carbon in fly ash decreased by 1.8%compared PC.However,the NH3 co-firing in gas-ifier was more effective in reducing NOx emissions.During the G-20%NH3,NO emissions were decreased by 23.51%compared to C-20%NH3.The study offers some innovative ideas and data reference for the development of low NOx emis-sion technology for NH3 co-firing in coal-fired boiler.
万方数据
维普
