Study On Adsorption And Separation Of Carbonyl Sulfur From Blast Furnace Gas By Transition Metal Modified γ-Al₂O₃

Blast furnace gas（BFG）is a combustible gas by-product in the ironmaking process, and it is an important secondary energy source.It is characterized by low calorific value（about 3500 k J/Nm³）and large combustion exhaust air volume.Carbonyl sulfide（COS）is a typical pollutant in blast furnace gas.The presence of COS causes corrosion of blast furnace gas pipes and pollutes the air to form acid rain when discharged into the atmosphere.Therefore,it is of great practical significance to remove COS from blast furnace gas.Activated alumina-based catalysts are commonly used for catalytic hydrolysis to remove COS,but H₂S is easily generated during the reaction process,and the activity is unstable and easily deactivated during the reaction.Therefore,in this paper,the adsorbents were prepared using transition metal as the active component andγ-Al₂O₃ as the support,and the adsorbents were prepared by the equal volume impregnation method,and the adsorbents prepared by single-metal active component modified withγ-Al₂O₃ and bimetallic active component modified withγ-Al₂O₃ were studied for the removal of COS from blast furnace gas.The optimum temperature,optimum metal loading and optimum bimetallic active components for COS removal were determined by activity evaluation.The reaction mechanism of COS removal was determined by XRD,BET,CO₂-TPD,XPS and FTIR characterization.The following conclusions were obtained:（1）The reaction temperature has a significant effect on the removal of COS.The adsorption reaction between COS andγ-Al₂O₃ at low temperature will generate a large amount of H₂S,and the amount of H₂S generation decreases with the increase of temperature.Therefore,according to the blast furnace gas source control conditions 200℃is the best reaction temperature.（2）Different transition metals and their contents have an effect on the removal of COS,and the study showed that the addition of transition metals significantly inhibited the generation of H₂S as a by-product.5-Fe A adsorbent has the best effect of COS removal,and the COS removal rate can be maintained above 99%for 381 min with a sulfur capacity of 157.42 mg·g^-1.（3）The bimetallic active components and impregnation order had significant effects on the removal of COS.The best performance for COS removal was achieved by preparing adsorbents with Fe and Co as active components.The x-Co A adsorbent was prepared first,and then 5.0 wt.%Fe（NO₃）₃ was added for equal volume impregnation.The results showed that the adsorbent prepared by this method had a significantly enhanced effect on COS removal,indicating a certain synergistic effect between the active components of Co and Fe.The 1Co-5Fe A adsorbent COS removal rate was maintained above 99%for635 min,and the sulfur capacity was as high as 262.37 mg·g^-1.（4）The experimental characterization results elucidate the reaction mechanism.Firstly, COS is adsorbed on the-OH on the adsorbent surface to generate intermediate HSCO₂^-;then part of it is oxidized by[O]on the adsorbent surface to HSO₃^-and HCO₃^-,HSO₃^-forms sulfite and is further oxidized to sulfate;the other part reacts with crystalline water or-OH to generate H₂S,which is oxidized by[O]on the adsorbent surface to sulfur monomer,sulfite and sulfate.