Integrated Process Of Coal Pyrolysis With CO₂ Reforming Of Methane By Spark-discharge Plasma

Coal plays an important position in energy resources of China in a long term. However, great waste of energy and increasing environmental pollution make it important to promote clean and high efficiency utilization of coal. Pyrolysis, as the primary and important step, is one of the coal staged conversion and clean coal technologies. Spark discharge plasma, with the advantages of high density, high discharge channel temperature, high reactant conversion and low energy consumption is an effective approach for activate the CO2 and CH4 to produce syngas production. Our previous studies showed that integrated process of CO2 reforming of methane with coal pyrolysis can improve the tar yield. However, the optimum temperature mismatch between two processes requires further studies. CO2 reforming of methane by spark-discharge plasma can provide a great number of radicals and activated particles for coal pyrolysis, which is expected to solve the problem of the mismatch temperature between methane activation and coal pyrolysis. This dissertation is aimed to develop the integrated process of coal pyrolysis with CH4-CO2 activation by spark discharge plasma to improve the tar yield.(1) In the process of CO2 reforming of methane by spark discharge plasma, the plasma reactor is developed, and the effects of the reactor configuration parameters (input power, electrode size and discharge distance) and process conditions are investigated. The results showed that the conversions of CH4 and CO2 increase with the increasing discharge input power. H2 and CO selectivity also increase. The increase of the gas flow rate results in gradual decrease of the conversion of CH4 and CO2. However, the electrode with a big diameter and long discharge distance are unbeneficial to conversion of CO2 and CH4. The temperature has little effect on the conversion of reaction gases. Better catalytic performance can be obtained when the electrode is ?3 × 1 mm and electrodes gap is 8 mm, respectively.(2) Integrated process of coal pyrolysis with CO2 reforming of methane by spark-discharge plasma is investigated on the plasma reactor and the influence of process condition on the tar yield was examined in detail. The results showed that the tar and water yields increase with increasing the pyrolysis temperature. But the char yield decreases. Long pyrolysis holding time promotes the coal to produce more tar. But after 20 min, the tar yield has a slight increase. The pyrolysis atmosphere will influence the tar yield. Compared with the pyrolysis under N2 (BLG-N2) or the mixture gas of CO2 and CH4(BLG-MG), the integrated process of CO2 reforming of CH4 with coal pyrolysis can produce more tar. At the pyrolysis temperature of 550 ?, the tar yield is 1.41 times as BLG-MG, and 1.54 times as BLG-N2.