Salisu Ibrahim

The low and fluctuating demand and sales price of sulfur and its increasing production due to the discovery of new sour fields have mandated optimization studies to reduce the production cost in sulfur recovery units. Natural gas (mainly methane) is continuously co-fired with acid gas (H₂S and CO₂) in the Claus furnace to maintain temperatures above 1050°C, which adds to the operating cost. This study aims at optimizing the usage of natural gas in sulfur recovery units and enhancing sulfur yield simultaneously using a detailed reaction mechanism for Claus feed combustion, while ensuring complete BTEX destruction. An optimal combination of feed-preheating using natural gas and its co-firing in the furnace is determined through furnace and fired heater simulations. Through simulation studies by varying natural gas flow rates into the Claus furnace and to the air preheater, it is observed that a considerable amount of natural gas can be saved to maintain the required furnace temperature, if air is preheated to a higher temperature rather than natural gas co-firing (also validated in an operational sulfur recovery plant), (b) a reduction in natural gas to the furnace improves the sulfur recovery efficiency, and (c) the destruction of aromatic contaminants (that are harmful for the catalysts present downstream) in the furnace is enhanced with decreasing natural gas co-firing and increasing feed temperature. With multi-objective optimization, further increase in sulfur yield by 8% and a reduction in fuel gas demand is achieved.

Numerical examination of acid gas pyrolysis is presented with a focus to determine optimum condition for producing both sulfur and syngas that can be used in industry at high conversion efficiency of acid gas. Detailed simulation of acid gas to produce sulfur and syngas is presented that provides the feasibility of establishing plausible reactor conditions for such a recovery. This is a much different approach of producing thermal energy and sulfur. The results revealed that only pyrolysis of specific acid gas composition leads to the production of syngas and that temperature plays an important role in the conversion process. The simulation results provided here reveal the role of acid gas composition on high sulfur and syngas recovery under different operational conditions of the reactor with minimal adverse effect on the environment. The produced syngas can be utilized to enhance energy generation or produce valuable chemicals. The operational conditions provide means to seek different composition of the syngas. The syngas can then be used to produce value added products or liquid fuels. Detailed results under various input and operational conditions of the reactor are presented in the paper.