Study On Evolution Characteristics Of Light Gas Generated From Oil Shale Pyrolysis Process

A considerable amount of light gas by-product is generated in oil shale retortingprocess and is used as a fuel because of its good ignitability. The report about theinvestigation on evolution characteristics of light gas from oil shale retorting processis rarely found both domestically and internationally, thus thethermo-gravimetric-infrared-mass spectrometry (TGI) and the solid phase infrared (SI)were used for the investigation of evolution characteristics. The work was done forfollowing fields.The pyrolytic weight-loss characteristics of four oil shale samples wereinvestigated using thermos-gravimetric (TG) experiment. It turned out that theevolving trends of total volatile resembled each other during the oil shale retorting. Asmall amount of gas evolved from80to150℃, and volatile gradually evolved over150℃as temperature increased. Finally a large amount of volatile evolved between450to480℃.Through mass spectrometry and infrared experiments, the evolution rules wereinvestigated for six light gases including H2O, H2, CO, CO2, CH4and CnHmin oilshale retorting process. As temperature increased, the evolving rate curves of H2, CH4and CnHmwere basically the same, i.e. Gaussian distribution. The evolving ratecurves of CO and CO2were similar. Both slowly increased, then accelerated andreached the biggest value. Finally dropped sharply till the end of retorting. Theevolving rate curve of H2O is relatively complicated. First the oil shale internalmoisture evolved, then mineral crystallization moisture evolved, and finally pyrolyticmoisture evolved. The evolving rates of these three stages all increased to the biggestvalues, and then decreased.The activation energies and frequency factors of six light gases under differentheating rates were176～249KJ·mol-1and109～1013S-1. As heating rate increased, activation energy slightly increased, and pre-exponential factor gradually increased.In terms of thermo-gravimetric weight loss, as heating rate increased, the oil shalepyrolytic beginning and terminal temperatures gradually increased, and the weightloss rate of whole process gradually decreased. The temperature corresponding to thebiggest weight-loss rate gradually increased and the light gas evolving temperaturerange gradually widened. In terms of the characteristic temperature of light gasevolution, the beginning, terminal, and biggest evolving temperatures and thetemperature corresponding to the biggest evolving rate all increased with heating rateincreasing. In terms of the evolving cumulative production of light gas, the increaseof heating rate resulted in the slight increase of light gasevolving-cumulative-production, displaying some hysteresis.