Clean hydrogen energy production via purification of hydrogen sulfide thermolysis products employing supersonic separator

Abstract

Catalytic thermolysis of hydrogen sulfide rich acid gases at elevated temperatures is a novel process to produce clean hydrogen fuel. Separation of the hydrogen gas from furnace effluents is rather a difficult task. Several approaches such as membranes, adsorption and absorption processes are traditionally used to achieve this goal. Each of these conventional processes has its own difficulties such as high capital and operation investments, large equipment sizes and elevated corrosion rates. Employment of supersonic separators for the above purpose strongly alleviates the above problems. The present work investigates the use of supersonic separator units both as a final separation device and also as a hybrid pre-treatment method via numerical simulation using MATLAB-Simulink toolbox. It was noticed that a single supersonic separator unit is unable to accomplish the target specification as a final separation device. Hence, consecutive combination of supersonic separator units is used to obtain the desired hydrogen purity. The performance of the entire supersonic separator network strongly depends on the inlet pressure of each individual supersonic separator unit. Detailed optimization of the entire process revealed that for the case study at hand, the optimal inlet pressure for all eleven required supersonic separator units would be around 7 MPa. The number of required 3S units and the overall power of compressors required between the 3S stages are used as the optimization merit functions. Furthermore, in a hybrid approach, a combination of supersonic separator units is used prior to absorption process to reduce the hydrogen sulfide concentration of the hydrogen gas product to less than 4 ppm. Use of four consecutive supersonic separator units along with the absorption process can lead to more than 95% saving both in DEA circulation rate and reboiler duty. The entire above issues have not been addressed previously in the literature.