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

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.