Coal pyrolysis to acetylene using dc hydrogen plasma torch: effects of system variables on acetylene concentration

Abstract

In order to unveil the inner mechanisms that determine acetylene concentration, experimental studies on the effect of several parameters such as plasma torch power, hydrogen flux and coal flux were carried out from coal pyrolysis in a dc plasma torch. Xinjiang long flame coals including volatile constituents at a level of about 42% were used in the experiment. Under the following experimental conditions, namely plasma torch power, hydrogen flow rate and pulverized coal feed speed of 2.12 MW, 32 kg h−1 and 900 kg h−1, respectively, acetylene volume concentration of about 9.4% was achieved. The experimental results indicate that parameters such as plasma torch power and coal flux play important roles in the formation of acetylene. Acetylene concentration increases inconspicuously with hydrogen flux. A chemical thermodynamic equilibrium model using the free energy method is introduced in this paper to numerically simulate each experimental condition. The numerical results are qualitatively consistent with the experimental results. Two parameters, i.e. the gas temperature and the ratio of hydrogen/carbon, are considered to be the dominant and independent factors that determine acetylene concentration.