The Effect of H2S on Production of Carbon Black From Sub-Quality Natural Gas

Abstract

The objective of this paper is computational investigation of the carbon black production through thermal decomposition of waste gases containing CH4 and H2S, without requiring a H2S separation process. The chemical reaction model, which involves solid carbon, sulfur compounds and precursor species for formation carbon black, based on an assumed Probability Density Function (PDF) parameterized by the mean and variance of mixture fraction and β-PDF shape. The soot formation is modeled by using the soot particle number density and the mass density based on acetylene concentrations. The effects of feedstock mass flow rate and reactor temperature on carbon black, soot, CO, S2, SO2, COS and CS2 formation are investigated. The results show that the major factor influencing CH4 and H2S conversions is reactor temperature. The results reveal that at any temperature, H2S conversion is less than that of CH4. For temperatures higher than 1100°K, the reactor CH4 conversion reaches 100%. At temperatures below 1300°K, H2S conversion is too low and usually less than 5%. For temperatures higher than 1300°K, H2S conversion increases sharply with temperature and the major products of the process are S2 and SO2 while COS and CS2 are minor products. The results also show that the production of carbon black from sub-quality natural gas, process involving the formation of carbon monoxide which is occurring in parallel, play a very significant role. For lower values of feedstock flow rate, CH4 mostly burns to CO and consequently, the production of carbon black is low.