| Blast furnace gas is a kind of combustible gas produced by steel making enterprises,its output is large and contains sulfides such as H2S and COS.The Ministry of Ecology and Environment has strictly stipulated the emission standards for sulfides in blast furnace gas in the"Opinions on Promoting the Implementation of Ultra-Low Emissions in the Iron and Steel Industry"issued in April 2019.Therefore,the deep removal of sulfide in blast furnace gas has become an urgent problem to be solved in the iron and steel industry.Firstly,according to the sulfur-containing characteristics of blast furnace gas,this paper focuses on the organic sulfur COS,which is difficult to remove,and constructs a formulated solvent desulfurization system that can remove H2S and COS efficiently.The formulated solvent is based on methyldiethanolamine（MDEA）aqueous solution,and super base1,8-diazabicyclo[5.4.0]undec-7-ene（DBU）or1,5-diazabicyclo-[4.3.0]Non-5-ene（DBN）is the first additive component,the physical solvent polyethylene glycol dimethyl ether（NHD）or sulfolane（SUL）is the second additive component.The removal rate of COS with a concentration of 450 mg/m3and the saturated absorption of H2S with a concentration of 10 vol%were used to measure the removal and absorption effects of absorbents on sulfide.The research results show that the optimal formulated solvent composition is 30 wt%MDEA+40 wt%DBN+20 wt%NHD+10 wt%H2O.At room temperature and pressure,the COS removal rate of raw gas can be maintained above 93.8%and the saturated absorption of H2S can reach 3.28 mol/kg after absorption by the formulated solvent,both of which are much higher than that of single alcohol-amine solution.Secondly,five kinds of PILs were synthesized in this paper,namely three kinds of super basic imidazole-based ILs[DBUH][IM],[DBNH][IM]and[TMG][IM]and two kinds of super basie methylurea-based ILs[DBUH][MLU]and[DBNH][MLU].All five ILs have the ability to remove COS and H2S simultaneously.Among them,[DBNH][IM]has the best performance.At 30℃～35℃and 0.1 MPa,the COS removal rate can reach more than 97.9%and the H2S saturation absorption can reach 4.67 mol/kg after the raw gas bubble is fed with ionic liquid,which are much higher than the conventional type ionic liquid.And after 5 cycles of regeneration,it can still maintain high COS removal rate and H2S saturation absorption.The successful synthesis of ionic liquids and the existence of strong chemical bonding between COS and H2S were verified by combining IR,NMR and TGA.In addition,the desulfurization effect is still good after forming a low viscosity compound system of ILs with MDEA and H2O.Finally,a deep eutectic solvent desulfurization system was constructed in this paper.First,a low-viscosity ILs-EG DES was synthesized by using ionic liquid and ethylene glycol.This solvent has a good absorption effect on sulfide and can be used in desulfurization processes with viscosity requirements.Then ternary deep eutectic solvents were synthesized by adding different molar ratios of DBU or DBN to the binary DES of choline chloride-propanetriol.The removal rate of COS and saturated absorption of H2S increased with the increase of DBU or DBN content.When the molar ratio of Ch Cl-Gly-SB（DBN,DBU）is 1:2:3,the best desulfurization effect is achieved,and DBN performs better than DBU.Under the condition of0.1MPa and 35℃～40℃,the COS removal rate can be maintained above92.6%after the raw gas is absorbed by Ch Cl-Gly-DBN ternary DES,and the saturation absorption of H2S can reach up to 4.39 mol/kg.In summary,all three desulfurization systems constructed in this paper can simultaneously remove COS and H2S from blast furnace gas,and the desulfurization effect is better than that of the traditional alcohol-amine solution,providing more options for the deep desulfurization of industrial blast furnace gas. |
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