Study Of Heat Transfer Characteristics Of Ni-Foam Structured Catalyst And Its Application To Methanation Reaction

With the rapid development of Chinese economy and comprehensive promoting of urbanization, natural gas, as a kind of safe, clean, convenient and high-quality energy, is much fancied and its demand-supply contradiction is becoming increasingly prominent. To take advantage of our abundant coal and biomass resource to produce synthetic natural gas or substitute natural gas (SNG, substitute or synthetic natural gas) hasgreat significance. This paper mainly studied the heat transfer properties of novel Ni-foam structured catalyst and its application to methanation reaction on the basis of lab-scale test.The macrokinetics of methane synthesis over novel Ni-foam structured catalysts of 100 PPI was investigated experimentally in a fix-bed reactor at pressure of 0.5MPa, temperature of 280-580℃, space velocity of 9000-21000h-1. Inlet gas compositions are as follows:CO 0.0500-0.1500; CO2 0.0727-0.2500; H2 0.2647-0.5000; CH4 0-0.4000; N2 0.1000-0.6000. The macrokinetics models were derived according to Langmuir-Hinshelwood uniform adsorption theory, which selected CO, CO2 as the key components and CO, CO2 methanation reactions as independent reactions. The Levenberg-Marquardt method combined with Global Optimization Universal method were used to calculate the relevant parameters, and the results of residual analysis and statistical tests showed that the models were suitable.Steady-state heat transfer behavior of a gas flowing through a fixed bed packed with Ni-foam structured catalyst under various operation conditions were investigated. Experiments were carried out in a dedicated tubular reactor with inlet air temperature ranging from 160 to 200℃, heating pipe temperature inside the fixed bed ranging from 400 to 500℃ and air flow rate ranging from 4.0 to 6.0 Nm3·h-1. Effective radial conductivity (λer) and wall heat transfer coefficient (αw) were derived based on the steady-state measurements and the two-dimensional pseudo-homogeneous heat transfer model. The estimated value of λer and αw were between 2.2 and 3.4 W·m-1·K-1 and 170 to 250 W·m-2·K-1 respectively. And the parameters were correlated.Two-dimensional pseudo homogeneous mathematical models of synthetic gas methanation in adiabatic fixed-bed reactor were established and solved by finite difference method conbined with dynamics equations and heat transfer parameters correlations. The temperature and concentration distributions in the fixed bed reactor packed with Ni-foam structured catalyst were obtained and analyzed. The effects of inlet temperature, inlet pressure, outlet gas cycle ratio on the temperature and concentration distribution of the bed were investigated. The simulation results provided a reliable basis for the optimal design and operation of the reactor.