Thermodynamic Analysis And Reactor Simulation And Optimization Of Methane Dry Reforming

Methane dry reforming(DRM)combines the conversion of methane with the utilization of greenhouse gas CO2,which is suitable for producing syngas with low H2/CO ratio.However,there are problems of excessive temperature gradient and severe carbon deposition in the reactor during the actual industrial application of DRM.For these questions,the influence of reactor structure and operating conditions on the thermal effects in the tubular reactor were investigated,and the carbon deposition behavior in the reactor was explored by combining with the principle of equilibrium gas and the reactor model.Firstly,the Gibbs free energy minimization method was used to investigate the effects of temperature,pressure and feed ratio on the thermodynamic equilibrium composition and conversion.Furthermore,combined with the principle of equilibrium gas to draw the thermodynamic carbon deposition area,and the effects of temperature and pressure on the thermodynamic carbon deposition curve were also studied.The thermodynamic research results show that graphite carbon is easier to generate than whisker carbon.In addition,increasing the temperature and reducing the pressure at temperature higher than 700℃ can reduce the risk of carbon deposition in the DRM reaction system.Secondly,the reactor reaction-mass transfer-heat transfer simulation calculation was used to explore the effects of reactor structure and operating conditions on the performance of two archetypical tubular reactors(TR1 and TR2).The reactor simulation results show that reduce the packing density of catalyst and narrowing the tube size are beneficial to control temperature in the tubular reactor,while increasing the inlet temperature does not importantly affect the performance of the reactors.The elevated total pressure reduces the temperature gradient and also the equilibrium conversion of methane.The feed CH4/CO2 ratio only slightly changes the temperature distribution but importantly affects the equilibrium conversion of methane.Finally,we combine the principle of equilibrium gas with reactor simulation to investigate the effects of different reaction systems and operating conditions on the carbon deposition area in the tubular reactor for the three carbon deposition reactions(methane cracking reaction,CO disproportionation reaction,and CO reduction reaction).The reactor carbon deposition behavior reaults show that the problem of carbon deposition can not be avoided only by changing the ratio of CO2/CH4 in the feed and all the three carbon deposition reactions can produce coking for the DRM reaction system.For the addition of H2O to the DRM reaction system,the risk of carbon deposition in the tubular reactor can be reduced by increasing the inlet temperature and the wall temperature,reducing the total pressure and the CH4 mole fraction of feed,and appropriately elevating feed ratio of H2O mole fraction to CO2 mole fraction.The results of this paper will provide some theoretical guidance for the design of tubular reactors,optimization of DRM operating conditions,and development of carbon deposition suppression methods in tubular reactor.