Product Distribution And Chlorine Migration In Co-pyrolysis Of Coal And Polyvinyl Chloride

Plastics because of their excellent properties, are widely used in people’s production and life, but also produce a lot of waste plastics, known as "white pollution"; the co-pyrolysis of coal and waste plastics is one of the effective methods in clean and efficient use of waste plastics and coal. Not only can get valuable gas, tar, semi-coke, but also to control the "white pollution." The waste plastics inevitably mixed with polyvinyl chloride (PVC), thus chlorine is introduced into the pyrolysis products, and the chlorine will eventually be released in the form of HCl, which can cause serious pollution to the environment. Therefore, the research of how chlorine effects on coal and PVC co-pyrolysis process and chlorine distribution in the co-pyrolysis products is of great significance on the development of co-pyrolysis and dechlorination process.In this paper, a fixed bed pyrolysis apparatus is used to study the pyrolysis and of co-pyrolysis Hesigwula lignite, shenmu bituminous coal and PVC. The artical investigated the effects of pyrolysis conditions (pyrolysis temperature, residence time, and the carrier gas flow rate) on Hesigwula lignite, shenmu bituminous coal and PVC pyrolysis products, thus screening the optimal pyrolysis conditions. Under this condition, investigated the effects of pyrolysis temperature, mass ratio of PVC and coal on co-pyrolysis product distribution and the migration of chlorine, then obtain the regular pattern of the migration of chlorine.From the TD-DTG analysis of Hesigwula lignite, shenmu bituminous coal and PVC and Coast-Redfern method adopted to calculate the activation energy are54kJ/mol、143kJ/mol、196kJ/mol, respectively. The activation energy decreases after co-pyrolysis of PVC and coal. In the fixed-bed pyrolysis experiments, pyrolysis process conditions affect the pyrolysis of coal, including temperature had the greatest influence. When the residence time more than20min and carrier gas flow rate is greater than200ml/min, the residence time and carrier gas flow rate has almost no effect on the distribution of pyrolysis products. Hesigwula lignite obtain its highest lignite tar production rate of8.33%(dry basis, wt), under the pyrolysis temperature of520℃, carrier gas flow of200ml/min, residence time of20min conditions, while shenmu bituminous coal obtain its highest lignite tar production rate of9.00%(dry basis, wt), under the pyrolysis temperature of540℃, carrier gas flow of200ml/min, residence time of20min conditions. Selecting the maximum tar yield of pyrolysis conditions on PVC and coal co-pyrolysis, PVC and coal mass ratio and pyrolysis temperature all have effects on pyrolysis products yields. When PVC co-pyrolysis with coal, the pyrolysis tar and aquatic rate both increased.For the analysis of pyrolysis products, the chlorine content of semi-coke, moisture, volatile matter and H/C decreased with the increase of pyrolysis temperature, ash content, fixed carbon as the pyrolysis temperature increases rises. Pyrolysis tar chlorine content is generally about2%, with an increase in the proportion of PVC slightly elevated and temperature on the impact of the regular pattern is not obvious. Finally, acid wash treatment of tar derived acidic, basic points, polarity, aromatics and fat points, research tar constituents by GC-MS, found that low levels of chlorine compounds in the tar, mainly in chlorobenzene form.