Study On The Precipitation Law Of H₂S In The Process Of Coal Pyrolysis

Nowadays,many coal mines in China have problems that H₂S concentration exceeds permissible standard??6.6ppm?,which has a negative effect on the safety and efficient production of coal mines as well as people's health.According to Scholars'studies from the geologic examples of coal mines,believing that H₂S is mainly caused by the effect of Thermochemical Sulfate Reduction?TSR?,however,no futher studies have been conducted through experiments.Consulting the research results made by scholars in the generation of H₂S in oil and gas field,this paper has used two kinds of sulfur-containing coal samples?meagre coal in Xin'an coal mine and non-caking coal in Xi'shan coal mine?as research objects,thermal simulation experiments have conducted by putting in different sulphate solution,and the pyrolysis experiments of coal with water are as reference,studying the capacity of generating H₂S in different conditions.Thermal simulation experiments have been done in the vacuum condition and adopting temperature programming,the content of gaseous products collected in different temperature spots were measured by 7890B gas chromatograghy produced by Agilent corporation in America.By analyzing the change features of content of gaseous products with temperatures in pyrolysis process,the main conclusions are as follows:Sulfur-containing coals,especially those with medium-high sulfur,can produce a certain amount of H₂S with water in pyrolysis process,which is mainly attributed to the thermolysis of aliphatic sulfur compounds and pyrite in coal.Both Xin'an coal and Xi'shan coal,the content of H₂S produced after adding sulphate solution is obviously higher than that in coal with water,indicating that addition to the H₂S produced by the thermolysis of coal itself,thermochemical Sulfate Reduction?TSR?can be triggered caused by the adding of sulphate solution to the pyrolysis system,which can promote the generation of H₂S significantly.The content of sulfur in coal can determine the thermochemical Sulfate Reduction?TSR?to some extent.In the process of thermochemical Sulfate Reduction taking place and generating H₂S,hydrocarbon gas was consumed,normally macromolecule hydrocarbon gas whose carbon number is higher can be prior consumed,since their activation energy is lower and chemical activity is more active,CH₄ is not involved in the reaction because of its activation energy is higher.According to the reaction formula,CO₂ is also the production of thermochemical Sulfate Reduction,it can present the degree of TSR to some extent.Accompanied with the consumption of hydrocarbon gas as well as the generation of H₂S and CO₂,the content of other gas composition also changes respectively.