Fundamental Study On Pyrolysis Of Chinese Steam Coals And Model Compounds Containing Oxygen

Prompted by the need of non-petroleum-based fuels, coal research has reemerged to center stage today. Pyrolysis research, in particular, has gained considerable momentum because of its close connection to combustion, gasification and liquefaction. The results of scientific investigations of coal pyrolysis are the indispensable basis for technology in almost all areas of utilization of coal. In the present paper, we conducted the pyrolytic experiments of coals, macerals, coal extract and coal model compounds containing oxygen groups, respectively. The aim is to describes the distribution and evolution characteristics of pyrolysis products of used samples under different thermal conditions and present a purposely view of the relationship between a coal structure and pyrolysis reactivity. The theme includes such contents as follows:10 kinds of Chinese steam coal samples were chosen and their pyrolysis experiments were done under different conditions. Distribution and evolution characteristics of products during pyrolysis were observed. Elemental analysis, FTIR spectroscopy, GC-MS, 13C-NMR and XRD techniques were employed to characterize the tars and chars in details. Mass balance of elements C, H, O in various products produced at different temperature was obtained. The results show that the formation of volatile matter was mainly in temperature range of 400-700 ℃ and the evolution of products is functions of temperature. In bituminous coals where the weight loss is dominated by tar, the ultimate yield appears to increase very little beyond 700 ℃, while in lignites a considerable fraction of the volatiles consists of CO, CO2 and hydrocarbon gases, the ultimate weight loss continues increasing with temperature beyond 700 ℃. Almost all H and O of coal converted into volatile at 900 ℃. About 75% oxygen evolution in the gas phase oxygen, the great mass of this converted into the gas phase between 400-700℃. The conversion to tar-O was always is less than10%. Coal rank is a very important factor in the amounts of evolution of various products. The evolution characteristics of gaseous products are different.As the important part of coal organic structure, low molecular weight compound is thought to play a key role in the structure of coal and has a significant effect on the process of coal pyrolysis. The extract sample was obtained from vitrain extracted bytetrahydrofuran. The thermal decomposition behavior of vitriain and its extract were investigated by means of TG and Py-FTIR, the latter can continuously obtain IR spectra of the volatiles as the sample is heated. The TG and DTG curves of extract are different from that of vitrain. The rate of weight loss of extract is higher than that of vitrain. The maximum peak in DTG curve of extract moves towards low temperature compared with vitrain. The results of experiments using Py-FTIR shows that the amounts of aliphatic evolution of extract is higher than that of vitriain, the evolution profile indicates the evolution of aliphatic is fast. The amounts of methane and CO2 evolution from extract were lower than that of vitrain. No CO was produced from extract.Pyrolysis of macerals from Shenfu coal was performed using TG and Py-FTIR techniques. It was found that vitrinite has a lower peak temperature of evolution of volatile matter and greater weight loss rate than those of coal and inertinite. Vitrinite has higher yield of paraffin than that of coal and inertinite, while coal and inertinite give more evolution of oxygen-containing products.Because of the complex, ill-defined molecular compositions and structures of coals, and because of the multiplicity of possible reactions when coal undergo pyrolysis, pure organic compounds are often used as models of some facet of the nature of coal. Understanding the reactivity and the mechanism of organic molecules is developing from studies aimed at explaining how organic matter, especially those with oxygen-containing functional groups in coal, breaks during pyrolysis. Pyrolytic reactions of 12 organic compounds containin...