(319h) Exploring the Potential of Ni3S2 Based Sulfur Looping Process for Efficient Production of H2 from H2s: A Thermodynamic and Kinetic Study | AIChE

(319h) Exploring the Potential of Ni3S2 Based Sulfur Looping Process for Efficient Production of H2 from H2s: A Thermodynamic and Kinetic Study


Joshi, A. - Presenter, The Ohio State University
Mohammad, Z., The Ohio State University
Fan, L. S., Ohio State University
Hydrogen Sulfide (H2S) is a poisonous gas that is released during processing of fossil fuels. Despite the rise in utilization of renewable-based energy sources, non-renewable hydrocarbon fuels dominate the world’s energy production scenario and are slated to do so until 2050. Thus, a high amount of H2S generation will be continued for next couple of decades, making its treatment critical. Claus process is state-of-the-art H2S abatement technology; however, it suffers from various issues such as unfavorable reaction thermodynamics, high capital cost and requirement of an air separation unit (ASU). Moreover, the Claus process is ineffective in extracting value from H2S, as it converts the ‘Hydrogen’ content of H2S into low-value steam (H2O) instead of valuable hydrogen (H­­2) gas. To counter this, a sulfur looping process scheme utilizing Ni3S2 as a sulfur carrier was established for effectively decomposing H2S into H2 and S. It involves two sub-steps – sulfidation and regeneration. In the sulfidation step, Ni3S2 reacts with H2S forming NiS and H2, and in the subsequent regeneration step, sulfur is recovered as NiS is thermally decomposed back into Ni3S2 in presence of CO2. The sulfur looping scheme has been demonstrated at a laboratory scale fixed bed reactor, wherein ~80% H2S conversion was achieved at a gas hourly space velocity of 5000 hr -1 [1].

In this work, process analysis of sulfur looping was performed, and the results were compared against Claus process to establish the commercial feasibility of the process. Parametric studies were carried out on the sulfur looping process in ASPEN to obtain the reaction and feed conditions for both the sulfidation and regeneration steps. The thermodynamic results obtained were validated using relevant thermogravimetric experiments and X-ray diffraction analysis. After the conditions were determined through the combination of process simulations and experiments, system evaluation parameters such as overall H2S conversion, H2 and sulfur yield were calculated for the sulfur looping process and compared against the baseline Claus process. The thermodynamic performance was further quantified by carrying out energy and exergy analysis. Results indicate that for >99% H2S conversion, ~2.4% higher sulfur yield is obtained for the sulfur looping process with 100% selectivity towards H2 generation (no steam formation). Moreover, a significant increase of ~19% and ~8% in overall energy and exergy efficiencies, respectively was observed for sulfur looping process due to H2 production and requirement of fewer processing units. This work further corroborates the superior potential of the novel sulfur looping scheme to replace the existing Claus process as it overcomes its drawbacks and creates a valuable product from a toxic industrial waste. The findings from this study can be used to develop an economical and environmentally sustainable process.

[1] Jangam, Kalyani V., Anuj S. Joshi, Yu-Yen Chen, Shailaja Mahalingam, Ashin A. Sunny, and Liang-Shih Fan. "Synergistic decomposition of H2S into H2 by Ni3S2 over ZrO2 support via a sulfur looping scheme with CO2 enabled carrier regeneration." Chemical Engineering Journal 426 (2021): 131815.