| CCS technology is considered to be a most promising technology for carbon capture. It is reported that CCS technology is an essential factor that achieves the CO 2 emission turning-point until 2030 in C hina. Oxy- fuel combustion, which is considered to be the most easily industrialized CCS technology, includes O2/CO2 combustion mode and O2/H2 O combustion mode. HCN is an important precursor to NOx in coal combustion, therefore, it is of great science and reality value to investigate the HCN oxidation under oxy-fuel combustion mode.The mechanism used in my study was developed by M.U.Alzueta mechanism and GRI 3.0 mechanism. This mechanism is valiadated against the experimental results, it is found that this mechanism has a satisfactory agreement between modeling and experimental results. It revealed that the updated mechanism is suitable of predicting the HCN oxidation to NO in O2/CO2, O2/H2 O, O2/CO2/H2 O atmospheres. The updated mechanism is adopted to investigate the NO characteristics under CH4/HCN mixture fuel with O2/CO2, O2/H2 O, O2/CO2/H2 O atmospheres in opposed diffusion mode.The comparison of the N conversion rate in the O2/CO2 and O2/H2 O combustion modes with that in air combustion mode shows the emission of NO is enhanced due to high concentration of CO2 and H2 O.In O2/CO2 combustion mode, the N conversion increases with the increase of CO 2 volume fraction.The main reason is that the high concentration of CO 2 enhanced the reaction R462?NH+CO2=HNO+CO?and R401,R403,R414 with the help of third-body reactions so that the R401,R403 and R414 made a great contribution to the NO production.In O2/H2 O combustion mode, the N conversion increases with the increase of H2 O volume fraction.On one hand, the high concerntration of H2 O enhanced the reaction R376 to the first rank. O n the other hand, the high concerntration of H2 O enhanced the reaction R403 to the third rank, meantime, the high concerntration of H2 O enhanced the reaction-R414 to the second rank.In O2/CO2 atmosphere, the conversion ratio from HCN to NO increases with the increase of CO2 concentration. O, HNO and NO2 radicals increase dramatically with the increasing CO2 concentration, which enhances R312, R403 and R424, and this is the main reason for the raising of conversion ratio from HCN to NO. In O 2/H2 O atmosphere, the conversion ratio from HCN to NO also increases with the increase of H2 O concentration. This is caused by that high concentration of OH radical in O2/H2 O atmosphere, which results in that R403 is enhanced to the second rank in the case of 70% H2 O.The decrease of radical N weakened the R378. In O2/CO2/H2 O atmospheres, the conversion rate has a liner decreasing trend with the increase of the H2 O concentration at a certain O2 concerntration. The main reason is that with the increase of the H2 O concentration:?1? It significantly restricted the R424 NO2+H=NO+OH;?2?The contribution of R312?NCO+O=NO+CO?to NO has decreased;?3? The contribution of R364?NH+O=NO+H?to NO has also decreased. |
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