Sulfur Release Behaviors Of Sulfur-Containing Model Compounds And Coal During Pyrolysis

A:Automatic sulfur determination analyzer (XK-5000) was used to investigate the effects of carrier type, solvent dose, solvent type and the ultrasonic oscillation time on loading rate and adsorption rate of carriers with sulfur-containing model copounds in this study. It is found that the favorite loading condition is:active carbon as the carrier, loading rate is3%, acetone as solvent, solvent dose is4ml, the ultrasonic oscillation time as20min. Sulfur-containing model compounds, tetradecyl mercaptan, dibutyl sulfide, phenylsulfide,2-methyl thiophene, benzothiophene, dibenzothiophene, were selected to investigate their sulfur removal and release behaviors during pyrolysis under different atmosphere by thermo-gravimetric analyzer with mass spectrometer (TG-MS). Then pyrolysis connected with gas chromatogram (Py-GC).1. Sulfur release behavior under inert atmosphereIt is found that the order of sulfur removal is tetradecyl mercaptan> dibutyl sulfide>2-methyl thiophene> benzo thiophene> phenylsulfide> dibenzothiophene. Except for phenylsulfide, this rule is accord with the decomposition temperature order of the sulfur functional groups. SO2evolution was detected by MS and GC for all those model compounds; except for phenylsulfide and dibenzothiophene, COS evolution was also detected. While H2S evolution was measured only for tetradecyl mercaptan, dibutyl sulfide and2-methyl thiophene. However, SO2content is much higher than H2S and COS in pyrolysis gas for each model compound, which may be caused by that indigenous hydrogen is much less than indigenous oxygen under inert atmosphere, when active carbon used to carrier. Thus, most of sulfur radicals can connect with indigenous oxygen and release with the form of SO2. For phenyl sulfide, benzothiophene and dibenzothiophene, as their indigenous hydrogen is not enough to react with sulfur radicals, no H2S was detected during pyrolysis under inert atmosphere, while SO2content is very high in pyrolysis gas.2. Sulfur release behavior under oxygen atmosphereThe order of sulfurs release is following as dibutyl sulfide>2-methylthiophene> tetradecyl mercaptan> benzothiophene>phenylsulfide> dibenzothiophene. During pyrolysis under an oxidative atmosphere, the decomposition temperatures of all of the sulfur compounds are lower than that under inert and hydrogen atmosphere, indicating that oxygen can break C-S bonds more easily than C-C bonds. The SO2evolution of most sulfur model compounds except2-methylthiophene and dibenzothiophene is derived mainly from decomposition of their transformation compounds rather than their native forms. Most sulfur compounds can be removed under an oxidative atmosphere with little loss of carbon. B:In this study, Yima (YM), Jincheng (JC), Jiexiushuiyu(JXSYJM), Xinmeng (XMHM), Daliuta (DLTM), Yanzhou (YZ) and Pingshou (PS) coals were selected to investigate their kinetic model during pyrolysis by thermo-gravimetric analyzer with mass spectrometer (TG-MS).The following conclusions could be drawn:1. It is found that the kinetic model of coals pyrolsis is quite fit for the first order reaction model. The activation energy of all coal samples under oxidative atmosphere is smaller than that under inert atmosphere. Because oxidative atmosphere is contributes to coal pyrolysis reaction. Pre-exponential factor (A) under oxidized atmosphere is also larger that than under inert atmosphere.2. By analyzing the SO2releasd peaks of YZ coal under oxidized atmosphere, it is found that the first release peak area is much higher than the second, which indicates that not only unstable organic sulfur, but also stable organic sulfur can also decompose under oxidized atmosphere. Each peak temperature under oxidized atmosphere is obviously lower than that under inert atmosphere, and the peak intensity enhanced much higher, which illustrates oxygen is very conducive to sulfur decomposing. Thus, under oxidative atmosphere, the higher desulfurization efficiency can also be achieved with little loss of crabon during coal pyrolysis. Since oxygen can break C-S bonds more easily than C-C bonds, SO2release is previous to CO2.