Numerical Model of a Heterogeneous Pyrolysis Reactor of Methane

Abstract

A mathematical model of a high-temperature cylindrical reactor for heterogeneous pyrolysis of methane during its filtration through a moving layer formed by granules of carbonized wood is presented. The carbon matrix was modeled by spheres of the same diameter with a simple cubic packing. The carbon matrix was heated through the reactor wall. Preheated methane was fed into the lower part of the reactor. The process of pyrocarbon formation as a result of heterogeneous pyrolysis of methane was described by one gross reaction taking into account hydrogen inhibition and changes in the reaction surface. It was assumed that the rate of pyrocarbon deposition is directly proportional to the partial pressure of methane. The system of two-dimensional, nonstationary differential equations describing the operation of the reactor in a cyclic mode with periodic unloading of a portion of carbon–carbon composite and synchronous loading of carbonized wood granules was solved numerically using the DIFSUB algorithm. The reactor radius and operating parameters (specific mass flow rate of methane, carbon composite unloading frequency) were varied in calculations. Based on the obtained results, the dependences of the quality of the carbon–carbon composite (average density and maximum density spread), the composition of the hydrogen-containing gas mixture at the reactor outlet, the degree of methane conversion, the reactor productivity for carbon composite and hydrogen on the operating parameters, and the reactor radius were analyzed. Data are provided on energy consumption for heating methane and carbonized granules loaded into the reactor as well as for compensation of the endothermic effect accompanying methane pyrolysis.