In this study, manganese was added as a promoter to zinc oxide adsorbent with the aim of improving its performance in industrial applications such as the steel industry. At Mobarakeh Steel Company of Esfahan, iron ore containing impurities such as sulfur undergoes several processing stages an‎d is converted into pellets, which are then fed into the direct reduction unit, where they come into direct contact with the process gas inside the furnace an‎d undergo reduction. The process gas is produced by methane reforming over a catalytic bed within reformer tubes an‎d mainly consists of hydrogen an‎d carbon monoxide. During the reduction of pellets inside the furnace, the sulfur content in the pellets reacts to form hydrogen sulfide, which enters the gas mixture. When this gas is recycled to the reformer, the presence of hydrogen sulfide poisons the catalysts an‎d reduces the efficiency of the reducing gas production. Zinc oxide adsorbents are used to remove this contaminant, an‎d their optimal operating temperature is typically between 350 an‎d 370 °C, while the temperature of the recycle gas an‎d the natural gas feed should be higher than 400 °C. In this research, the zinc oxide adsorbent was modified by adding different weight percentages of manganese (4, 8, 12, an‎d 16 wt%) using the impregnation method with zinc nitrate tetrahydrate solution. After drying, sieving, an‎d calcination, the adsorbents were characterized using XRD, BET, FESEM, an‎d EDS analyses. The results confirmed the successful incorporation of manganese into the adsorbent structure. Hydrogen sulfide adsorption tests were conducted at 370 °C an‎d 420 °C. At 370 °C, the adsorption capacities for the unpromoted sample an‎d the Mn-promoted samples containing 4, 8, 12, an‎d 16 wt% manganese were 32.58, 27.45, 31.3, 29.5, an‎d 28 gram of adsorbate per 100 gram of adsorbent, respectively. The sample containing 8 wt% Mn, which had the highest specific surface area (31.88 m²/g) an‎d adsorption capacity among the modified samples, was selec‎ted for further testing at higher temperature. At 420 °C, the adsorption capacities of pure ZnO an‎d the 8 wt% Mn-modified adsorbent were 34 an‎d 32(gram of adsorbate per 100 gram of adsorbent), respectively. Although the overall adsorption percentage did not improve, the modified adsorbent exhibited a longer time to reach saturation, indicating enhanced stability an‎d better performance at elevated temperatures. Overall, the results demonstrated that adding manganese to zinc oxide improves the structural stability of the adsorbent an‎d its durability at high temperatures. The modification increased the breakthrough an‎d saturation times for hydrogen sulfide removal but did not enhance the total adsorption capacity.

محسن محمدي

مهدي ستاري نجف آبادي , محسن نصراصفهاني