Pilot-scale testing on catalytic hydrolysis of carbonyl sulfur combined with absorption-oxidation of H2S for blast furnace gas purification

Abstract

About 70 % of the flue gas in the iron-steel industry has achieved multi-pollutant ultra-low emissions in China until 2023, and then the blast furnace gas purification has become the control step and bottleneck. Our research group has designed and constructed the world's first blast furnace gas desulfurization pilot plant with the scale of 2000 Nm3/h in October 2021. The pilot plant is a two-step combined desulfurization device including catalytic hydrolysis of carbonyl sulfur (COS) and absorption-oxidation of H2S, continuously running for 120 days. In the hydrolysis system, one reason for catalyst deactivation has been verified from the sulfur deposition. HCN in blast furnace gas can be hydrolyzed on the hydrolysis catalyst to produce the nitrogen deposition, which is one of the reasons for catalyst deactivation and has never been found in previous studies. The deposition forms of S and N elements are determined, S element forms elemental sulfur and sulfate, while N element forms -NH2 and NH4+. In the absorption-oxidation system, the O2 loading and the residence time have been optimized to control the oxidation of HS− to produce elemental sulfur instead of by-product S2O32−. The balance and distribution of S and N elements have been calculated for the whole multi-phase system, approximately 84.4 % of the sulfur is converted to solid sulfur product, about 1.3 % of the sulfur and 19.2 % of N element are deposited on the hydrolysis catalyst. The pilot plant provides technical support for multi-pollutant control of blast furnace.