Kinetics of single stage coal gasification to hydrocarbon gases.

摘要

This dissertation is a study of the Kinetics of single stage coal gasification to hydrocarbon gases. The studies were performed in a stirred batch autoclave reactor with a feed injector, using Ni-Mo on alumina, mixed with silica-alumina catalyst.; In the temperature range 440{dollar}spcirc{dollar}C-500{dollar}spcirc{dollar}C, 0-60 min, with a ratio of coal to tetralin to catalyst 1:3:1.25, the kinetic parameters of the coal gasification process were determined. It was found that coal converted very rapidly and was completed within 10 min reaction time, gas production increased rapidly in the first 10 min and then went up steadily, and liquid yields increased first, reached a maximum, then decreased as reaction proceeded. Therefore, the conversion of coal to gases involved two steps. The first step was thermal cleavage of the coal structure to produce liquid; the second step was liquids to gases. Coal to liquids occurs very rapidly and liquids to gases is the rate-determining step of the process.; Data interpretation techniques include a simplified isothermal data evaluation, similar to techniques appearing in the literature, and a more rigorous nonisothermal method to accommodate the temperature change during the reaction. The isothermal approximation showed that gas production from liquids is first order with respect to liquid. The apparent activation energy is about 23 kcal/mol. The first order kinetic treatment of the data by the more precise nonisothermal method led to an apparent activation energy of 27 kcal/mol.; Part of this study was concerned with the mechanism of liquids to gases. This provided the basis for understanding the production of C{dollar}sb2{dollar}-C{dollar}sb4{dollar} hydrocarbon gases from coal. The study utilized coal liquid model compounds, including long-chain normal paraffins, such as n-hexadecane, partially hydrogenated condensed aromatics, such as tetralin, and condensed aromatics such as anthracene and phenanthrene. The products were analyzed by GC-MS and compared with those produced by hydrocracking these model compounds, which is widely accepted as proceeding via a carbonium ion mechanism. Similar product distribution was obtained, especially for the gas composition, in which C{dollar}sb3{dollar} and C{dollar}sb4{dollar} are predominant.; A series of runs was made using coal liquid produced from previous runs as part of the hydrogen donor solvent. No decrease of coal and gas conversion were found as more and more coal liquid was used.