Simulation of the direct production of synthesis gas from sour natural gas by Noncatalytic Partial Oxidation (NCPO): Thermodynamics and stoichiometry

Noncatalytic partial oxidation of sour natural gas is proposed in this paper as a novel scheme for the production of synthesis gas, which is generally integrated with a process for ammonia or methanol. The proposed scheme has many potential advantages vis-à-vis the existing steam-reforming process of sweet natural gas. It is a noncatalytic process in which the sour feed does not require desulfurization. The combustion of sour natural gas in oxygen under noncatalytic partial oxidation (NCPO) conditions is investigated theoretically using AspenPlus simulation techniques. The main scope of the work is to study the stoichiometry and thermodynamics of the proposed scheme. A kinetics study and the reactor characteristics are not within the domain of this paper. Separation of SC₂ gas from the synthesis gas was carried out by absorption in water to produce sulfurous acid, the feedstock to what is known as the "modified Westinghouse cycle". The role of various operating parameters in establishing the optimum yield of the H₂/CO gas mixture was investigated. This included feed temperatures of 900 and 1200 °F, an equivalence ratio (moles of O₂/moles of CH₄) between 0 and 1, and a H₂S content in methane between 0 and 10%.