Characteristics Of Swiss-roll Combustors Using For Ventilation Air Methane

More than 2.5×107 ton methane is directly discharged into the atmosphere because of coal mining, of which 70% is ventilation air methane(VAM). Methane is one of the most important greenhouse gas, the greenhouse effect of the methane emitted from coal mines all over the world is equivalent to 5.2×108 ton carbon dioxide and the energy is equivalent to 50 million ton coal. In China, more than 1.5×1010 Nm3 coal mine methane (91% is of it VAM), the social cost caused by coal mine methane exceeds 1.5×1010 Yuan.Based on the theory of excess enthalpy combustion, Lloyd suggested combusting low concentration premixed gases by Swiss-roll combustor (SRC) which raises the reaction temperature by heat transfer to combust VAM. Because of the large flow of mine ventilation, the flow state, the channel structure and varies with temperature of thermal properties should be considered, and a new thermal equilibrium model for normal scale SRC was developed in this study, then the temperature distributions of the combustors were calculated. The effects of inlet velocity, channel structure, diameter of combustion chamber and heat loss on heat transfer characteristics of SRC were investigated. The results show that the SRC can obviously raise the reaction temperature by heat transfer, and VAM of 1% concentration or lower can be direct combusted in it; the reaction temperature is significantly affected by channel width and channel length, while less by inlet velocity compared with them, and the diameter of combustion chamber has little effect on it; faster inlet velocity and narrower channel width are favorable to enhance heat transfer, and longer channel length can increase the reaction temperature effectively, but the factors of temperature, flow resistance, cost, etc. should be considered comprehensively in the design of SRC; heat loss decreases the reaction temperature and the heat transfer characteristics of SRC, and the performance parameters is more sensitive to heat loss when it is small.Subsequently, the heat transfer characteristics of SRC were investigated experimentally in order to verify the thermal equilibrium model. The results show that SRC can increase the reaction temperature and the relative errors between calculated value and experimental results lower than 5%, which means that the model developed in this paper can predict the reaction temperature accurately. With the increase of inlet velocity, the reaction temperature decreases, the heat transfer coefficient increases and the heat recirculating coefficient decreases, the effect of inlet velocity on the reaction temperature reduced at high inlet velocity. With the increase of the power of combustor, the reaction temperature raises and the heat recirculating coefficient increases slightly, compared with high power of combustor, the effect of the power of combustor on reaction temperature is larger at low power.Based on the heat transfer characteristics research of SRC and reduced mechanism, the effects of inlet parameters, structure parameters and heat loss on flameout, reaction zone drifts and energy efficiency were investigated. 3 distribution types of methane concentration and 6 distribution types of temperature in channels were discovered. The results also show that if enhance the heat transfer, the reaction zone will drift into the inlet channels, and the reaction temperature will not change greatly during this process, if weaken the heat transfer, the flameout maybe happen; increase the inlet velocity, channel length or decrease channel width and methane volume concentration, at first, the reaction zone move to the combustion clamber in inlet channel, then the reaction zone is stable in combustion clamber and at last the flameout happen, but, under some conditions, the reaction zone can't be stable in combustion clamber; heat loss will move the stable combust zone to reaction drift zone.At last, based on the thermal equilibrium model of SRC, the analysis of investment revenue was carried out in the background of the utilization of VAM. The effects of operation cost, production cost, power generation income and environmental protection income on profit of SRC were considered, and then an optimization model of SRC for VAM was developed. The effects of the basic parameters on profit of SRC were investigated, the operation parameters and construct parameters is optimized.