Effect of radicals recombination on acetylene yield in process of coal pyrolysis by hydrogen plasma

Abstract

A new process for production of acetylene by pyrolysis of coal in hydrogen plasma overcomes the disadvantage of discontinuity and pollution in the conventional carbide method. Complex homogeneous reactions take place after pulverized coal is injected into a high-temperature plasma reactor. In order to preserve C{sub 2}H{sub 2} in low-temperature gas, quenching is needed to avoid the dissociation of acetylene. The objective of this paper is to indicate that radicals recombination is also important in acetylene production. Therefore the quenching process should be optimized to obtain high yield of acetylene. In this work, C-H equilibrium system in high-temperature range of 2000-5000 K is obtained using the free energy minimization method. At lower temperature, the decomposition of acetylene can be avoided while the recombination reaction of radicals C{sub 2}H and H will not be interrupted. As a result, the acetylene concentration in quenched gas will increase. The theoretical acetylene content in quenched gas is computed using the radical recombination mechanism based on the composition of thermal equilibrium, and the optimized C/H ratio is determined simultaneously. The maximum acetylene content is 59.9% in volume. 4 refs., 3 figs., 1 tab.