Investigation on the Cause of the SO2 Generation during Hot Gas Desulfurization (HGD) Process

Abstract

In the integrated gasification combined cycle (IGCC) process, the sulfur compounds present in coal are converted to hydrogen sulfide (H2S) when the coal is gasified. Due to its harmful effects on sorbent/solvent and environmental regulations, H2S needs to be removed from the product gas stream. To simulate the H2S removal process, desulfurization was carried out using a dry sorbent as a fluidizing material within a bubbling, high-temperature fluidized bed reactor. The ZnO-based sorbent showed not only an excellent capacity of H2S removal but also long-term stability. However, unexpected SO2 gas at a concentration of several hundred ppm was detected during the desulfurization reaction. Thus, we determined that there is an unknown source that supplies oxygen to ZnS, and identified the oxygen supplier through three possibilities: oxygen by reactant (fresh sorbent, ZnO), byproduct (ZnSO4), and product (H2O). From the experiment results, we found that the H2O produced from the reaction reacts with ZnS, resulting in SO2 gas being generated during desulfurization. The unknown oxygen source during desulfurization was deduced to be oxygen from H2O produced during desulfurization. That is, the oxygen from produced H2O reacts with ZnS, leading to SO2 generation at high temperature.

A Review on Recent Progress in the Integrated Green Hydrogen Production Processes

“…It produces syngas followed by purifying it from dust and hydrogen sulphide which is then sent to the combined cycle gas turbine (SCGT) to generate power. Producing one MWh of electricity using natural gas and coal resulted in high carbon dioxide emissions of about 350-400 and 800-900 kg, respectively [59,60]. The mitigation costs of carbon dioxide in 2030 are predicated to be about 11, 26, and 19 €/t for IGCC, natural gas combined cycle (NGCC), and pulverized coal (PC) power plants [61].…”