Catalytic Combustion Of Methane And Dimethyl Ether In Micro Scale Parallel Plate Combustor

With miniaturization of portable devices and development of micro process technology,micro scale combustion becomes an very important part of micro energy systems and core requirement of micro devices.Until now,there are several problems in micro catalytic combustion.For example,instability in combustion,degradation of catalyst,ambiguity in interactions between gas-phase reaction and catalytic reaction are included.Catalytic combustion of methane and dimethyl ether in micro scale parallel plate combustor was studied by experimental and numerical methods.Catalytic combustion characteristics of methane and DME were studied.Effects of inlet flow,equivalent ratio,external heater temperature,wall material thermal conductivity and heat exchange coefficient of combustor external wall on catalytic combustion were studied.Relation of Pt particles agglomeration,sintering,valence state and catalytic activity was also investigated.Interactions between methane gas-phase reaction and catalytic reaction were investigated at last.By recording and analyzing conversion rate of fuel and combustor internal wall temperature,several results were revealed:Inlet flow has effect on absorption of fuel on catalyst.If inlet flow is too low,combustor temperature will be low.If inlet flow is too high,resident time and conversion rate will be low.Equivalent ratio changes quantity of oxygen and fuel.Too high or too low equivalent ratio has negative influence on catalytic combustion.External heater can raise conversion rate of catalytic combustion.Low thermal conductivity means low heat loss and nonuniformity of wall temperature,while high thermal conductivity means high heat loss and uniformity of wall temperature.Heat exchange coefficient of combustor external wall enhances heat loss process.If it is enough high,catalytic combustion will not occur in micro combustor.By using TEM and XPS on catalyst samples in 24 h continuous catalytic combustion,reasons for Pt/ZSM-5 degradation were revealed.The reasons are agglomeration,sintering of Pt particles and oxidation of Pt0.By investigating wall temperature,reaction heat and OH mass fraction of methane catalytic combustion in micro parallel plate combustor,some results were revealed:Gas-phase reaction of methane is caused by catalytic reaction of methane;In micro parallel plate combustor of 0.2 mm gap,gas-phase reaction promotes catalytic reaction evidently;In micro parallel plate combustor of 1 mm gap,negative effect of gas-phase reaction on catalytic reaction is more obvious.