Experimental Study On The Lignite Thermal Upgrading Combined With Gasification

Lignite has a large reserves in China, but only a limited amount of lignite has been used because of their low calorific value, high moisture content, and low thermal efficiency, being rich in oxygen-containing groups and high spontaneous combustion tendency, lignite upgrading combined with gasification could not only settle these problems but also offer a new approach for using lignite. In this research, the Chinese typical Shengli(SL) lignite was used for study. The main aim of the work was to understand the variation behaviors of SL lignite in the thermal upgrading combined with gasification process. The SL lignite was firstly upgraded in a fixed bed reactor, and then the quality and the structural properties of the upgraded lignite were characterized in order to analyze the influencing mechanism and evaluate the upgrading efficiency; the suitable upgrading condition and the gasification reactivity of the upgraded lignite were also discussed deeply in order to achieve the research objective that combining lignite upgrading and gasification process; the catalytic effect of the inherent mineral in SL lignite and the iron-based catalyst on gasification were also studied by washing coal and catalytic loaded. The main conclusions obtained in this work as follow:The upgrading temperature and the heat rate were the primary influence factor in the SL lignite upgrading process. The upgraded lignite yield as well as its maturity depended on the upgrading temperature, the heat rate had an obvious effect on the volatiles decomposition and the chemical component of the upgraded lignite. The porosity expanded with increasing the upgrading temperature but the mesoporous and the macroporous might be blocked by some decomposed large molecular groups; the oxygen-containing groups decomposed completely at 550? and many heterocyclic groups began to decompose subsequently. The physic-chemical structure of SL lignite changed significantly when upgraded within 450?-550?.The residual volatiles component in upgraded SL lignite was beneficial to gasification; the gasification reactivity of isothermal upgraded lignite decreased as enhancing the upgrading temperature but the gasification reactivity of non-isothermal upgraded lignite increased when the heat rate increased; the pore blocking occurred in upgrading process had a slight effect on the gasification reactivity; the gasification reactivity increased at the initial gasification stage but then decreased gradually; the gas production potential of upgraded lignite increased when enhancing the upgrading temperature but the effect of heat rate on gas production potential was non-significantly. The temperature range of 450 ?-550 ? was important for SL lignite utilization process that combining lignite upgrading and gasification.The water washing process for SL lignite promoted the pyrolysis and gasification; the inherent mineral washed by hydrochloric acid had a significantly catalytic effect on the pyrolysis and gasification reaction but the inherent mineral washed by hydrofluoric acid slowed the reaction rate. The iron-based catalyst could also improve the gasification rate but only had a less significant effect than inherent mineral probably due to the uneven dispersion.