Study On The Co-pyrolysis Of Bituminous Coal And Cornstalk

Co-pyrolysis is an necessary process of co-utilization of coal and biomass, which is not only the necessary step, but also anadjoint process. In this paper, based on thermogravimetric analyzer and a fixed bed reactor, an experimental study on the co-pyrolysis process of cornstalk and Yanchang bituminous coal was performed.The effects of different pyrolysis temperatures and different biomass blending ratios on the gas component yields and the total yield of pyrolysis products even the tar components were investigated.In the thermogravimetric analyzer experiment, the result indicated that there were synergistic effects during the co-pyrolysis process. Meanwhile, to investigate the effect of their inner alkaline-earth metals on the co-pyrolysis process, we gave the cornstalk and Yanchang bituminous coal an ash removal treatment. The calculated results showed that the activation energy and frequency factor changed with the mixture ratio of the biomass. Compared to the demineralization co-pyrolysis, the activation energy increased but the frequency factor decreased.In the fixed bed pyrolysis experiment, we studyed the influence of different pyrolysis temperatures and the blending ratios of cornstalk on the co-pyrolysis process. The results showed that:Yan chang bituminous coal and cornstalk have synergistic effects. Compared to the theoretical value, the char yields decreased, but liquid yields and gas yields showed different trends. According to the analysis of gas components, compared with the theoretical value, the yield of gas components mainly including CO2,CO,CH4, H2 showed different trends during the co-pyrolysis process, the yields of CO and CH4 increased. Compared to the co-pyrolysis of Yan chang bituminous coal and cornstalk, the gas yields decreased,while the liquid yields increased and the solid yields showed different trends in the acid-washed cornstalk and Yan chang bituminous co-pyrolysis process, meanwhile the yields of the each gas components including CO2,CO,CH4, H2 decreased, especially H2, CO2 yields significantly changed. Compared to the co-pyrolysis of Yan chang bituminous coal and cornstalk, as well as the products yields of co-pyrolysis of the acid-washed Yan chang bituminous coal and cornstalk at 600℃ and 700℃, the difference is small, but at 800℃, the gas yields decreased, the liquid yields increased. The yield of H2, CH4 declined, while the yield of CO2, CO had slightly decreased.By adding the KCl、CaCl2、MgCl2、in the fixed bed pyrolysis experiment, we mainly investigated the influence of potassium, calcium, magnesium on the co-pyrolysis process. Compared to the co-pyrolysis of Yan chang bituminous coal and cornstalk, adding KCl could result in an increase of gas yield, reduced the liquid yield, meanwhile promoting the release of CO2, CO, CH4, H2. With the increase of pyrolysis temperature, adding CaCl2 increased the yield of gas and solid, while reduced the yield of liquid. Adding CaCl2 facilitated the release of H2, CO2, CO, but playing a slight role in promoting the yield of CH4. Adding MgCl2 had no significant impact on the co-pyrolysis of Yan chang bituminous coal and cornstalkFor co-pyrolysis tar, we used the column chromatography way to analyse the tar, compared to theoretical calculation, the yield of asphaltenes and non-hydrocarbon decreased, while the aliphatic and aromatic increased. As for the acid treatment of cornstalk, the content of asphaltene substances and non-hydrocarbon improved, aliphatic hydrocarbons and aromatic substance decreased in the co-pyrolysis tar. Adding KCl increased the yield of aromatic and aliphatic hydrocarbons, and reduced non-hydrocarbon content, meanwhile the yield of asphaltene had a slight decrease in co-pyrolysis tar. According to the GC-MS analysis of co-pyrolysis tar, compared with the theoretical value, the content of total long-chain alkanes inpyrolysis tar decreased, and aromatic component and ethylbenzene dimethyl benzene aromatic compounds with side chains decreased, while the content of phenol, cresol, naphthalene increased. After the cornstalk being acid-washed, the content of phenol increased, while the content of naphthenic decreased. Adding KCl increased the content of naphthenic hydrocarbon of aliphatic component, as well as the content of Benzene, naphthalene and other components in the aromatic components, while reduced the content of phenolic compounds.