A split-flow sulfur recovery process for the destruction of aromatic hydrocarbon contaminants in acid gas

Abstract

Sulfur recovery from acid gas containing H2S through Claus process is an efficient process. However, the acid gas contains several impurities such as benzene, toluene, ethylbenzene and xylene (collectively known as BTEX), light aliphatic hydrocarbons, H2O, NH3, CO2, COS, CS2, and N2. Among the hydrocarbons, while the aliphatics get destroyed in the Claus furnace, the aromatics (BTEX) often survive the high-temperature environment to reach the catalytic units to form soot deposits on the catalyst active sites and reduce their activity. This necessitates catalyst replacement and increases operational cost. This paper proposes a split-flow sulfur recovery method with enhanced gas temperature to effectively destroy BTEX in the Claus furnace to reduce the operational cost, where a portion of the acid gas feed is injected at the furnace inlet while the remaining is injected in the furnace in the post-combustion zone. A detailed reaction mechanism, developed for acid gas combustion and validated with experimental data, is utilized to conduct furnace simulations with the split-flow configuration to predict temperature, BTEX destruction, and acid gas conversion to sulfur. The results indicate that the suggested configuration for the Claus furnace can significantly improve BTEX destruction in the furnace with enhance temperature and SO2 concentration in the initial part of the furnace, while the sulfur recovery efficiency remains unaltered. The novel flow configuration for BTEX destruction also evades the need to co-fire natural gas in the furnace that was mandatory earlier to ensure BTEX destruction.