The hydrolysis conversion rate of organic sulfur is a key factor in the desulfurization technology for blast furnace gas

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The hydrolysis conversion rate of organic sulfur is a key factor in the desulfurization technology for blast furnace gas. The significance of desulfurizing blast furnace gas lies in the fact that it is a combustible gaseous byproduct generated during the iron smelting process in the steel industry. As one of the main pollutants in the steel industry, under normal conditions, a large amount remains aside from what is used by the blast furnace hot blast stoves themselves. If it cannot be recycled, it can only be discharged, resulting in energy waste and environmental pollution. To make full use of the remaining blast furnace gas, in general, a portion of it is mixed or burned in coal-fired power boilers for small hybrid gas boilers, resulting in a limited amount of recovery. In recent years, with the vigorous development of energy conservation, emission reduction, and the circular economy in steel plants, as well as the continuous tightening of environmental protection policies, traditional treatment methods have become increasingly unsuitable to meet the environmental requirements under the new circumstances. Therefore, steel mills must start from the source. Removal treatment is carried out for inorganic sulfur and organic sulfur. For example, the Environmental Protection Bureaus of Tangshan City and Handan City have proposed removing H2S from blast furnace gas prior to its use, followed by clean utilization, and have outlined the directions for such treatment. Therefore, desulfurization of blast furnace gas in steel mills is no longer a matter of whether companies are willing to do it or not; it must be carried out unconditionally. 2. Technical challenges: The main components of blast furnace gas are CO, CO2, N2, H2, CH4, etc. Among them, the combustible component CO accounts for about 25%; the amounts of H2 and CH4 are very small. CO2 and N2 account for 15% and 55% respectively, and its calorific value is only around 3500 kJ/m3. Compared to coke oven gas, the hydrogen sulfide content in blast furnace gas is not high, at only 300–500 mg/Nm3. However, since blast furnace gas contains a certain amount of carbonyl sulfide, around 200–300 mg/Nm3, this poses significant challenges for treatment. Whether it is for the removal of hydrogen sulfide alone or for the hydrolysis of carbonyl sulfide alone, these are already well-established processes, and they are not difficult to implement. But the key issue is how to maintain a high hydrolysis rate of carbonyl sulfide at a certain hydrogen sulfide concentration (200 mg/Nm3). We have previously handled similar process cases involving the simultaneous presence of hydrogen sulfide and organic sulfur in gases. Since the organic sulfur hydrolysis catalysts produced by most domestic manufacturers can maintain a high hydrolysis rate only when the concentration of imported H2S is very low (for example, H2S ≤ 100 mg/Nm3), a “Hamburger” type configuration is generally used for treating such gases. That is, the process gas first enters wet desulfurization to remove hydrogen sulfide from the gas, and then proceeds to organic sulfur hydrolysis. The hydrolyzed process gas enters the subsequent wet desulfurization system once again; after sulfur is removed from the gas, it is sent on to the next stage once it meets the required standards. So the question arises: if this process is used to treat blast furnace gas, then two wet desulfurization systems (one before and one after) as well as an organic sulfur hydrolysis system (in between) need to be installed. When the hydrogen sulfide content is not high to begin with, treating blast furnace gas in this manner results not only in high one-time capital costs for technical upgrades but also in high operating expenses. Breakthrough in solving the 3 problems: Tangshan Lvyuan Environmental Protection Technology Co., Ltd. is a high-tech enterprise engaged in basic research, technology development, engineering design, equipment manufacturing, and industrialization of combustible gas desulfurization technologies. It has a wide range of application records in the removal of hydrogen sulfide using the wet oxidation method. In recent years, due to **rising environmental standards and increasingly strict requirements regarding sulfur compound emissions, developing new desulfurization processes to meet the needs of modern production has become an urgent challenge that must be addressed. To this end, our company has proposed a project to develop new technologies for desulfurizing blast furnace gas, and is actively engaging in technical cooperation and research and development with other relevant organizations. The Chemical Engineering Research Group at Tianjin University has a **Key Laboratory of C1 Chemical Engineering**, jointly established by Tianjin University and Tsinghua University. Focusing on carbon monoxide utilization as the main research direction, and with the goal of efficient use of syngas, research is being conducted on new processes for syngas methanation, production of low-carbon olefins from syngas, and carbonylation of syngas to produce organic oxygen-containing compounds. Focusing on the key scientific issues in the green synthesis processes of alkyl carbonates and oxalate esters via carbonyl synthesis, as well as downstream products of oxalate esters such as ethylene glycol, ethanol, and diphenyl carbonate, systematic research is conducted in areas including catalyst design, system integration, and process scale-up. The carbonyl sulfide hydrolysis catalyst developed through research by the Chemical Engineering Research Group at Tianjin University in high hydrogen sulfide concentration environments has shown good performance. New process technologies more suitable for desulfurizing blast furnace gas. Thanks to the carbonyl sulfide hydrolysis catalyst developed by the One-Carbon Chemical Engineering Research Group at Tianjin University, which can ensure a hydrolysis conversion rate of over 90% even when the hydrogen sulfide concentration in the gas is as high as 1000 mg/Nm3, the problem of desulfurizing blast furnace gas is easily solved. That is, the blast furnace gas enters the carbonyl sulfide hydrolysis system directly, where the carbonyl sulfide in the blast furnace gas is hydrolyzed into hydrogen sulfide, and then it proceeds to the wet desulfurization system. After wet desulfurization treatment, the sulfur content meets the standards and can proceed to subsequent processes. Compared to traditional methods, this new process for purifying blast furnace gas reduces the initial investment by more than 30%. In terms of operating costs for the device, there is a reduction of at least 40%. The application of complexed iron desulfurization technology in the coal gas industry **overcomes the previous shortcomings of the PDS method, such as insufficient desulfurization accuracy and high production of by-products. This system has significant advantages: it occupies a small area, can be designed as a skid-mounted unit, and achieves a hydrogen sulfide removal rate of 99.9%. It can meet the increasingly stringent environmental requirements. Most importantly, no by-products are generated, **which reduces the environmental pressure on enterprises as well as their operating costs. 4. Application prospects: China is the world’s largest steel producer, generating a huge amount of blast furnace gas; currently, the amount of this gas that is released into the atmosphere amounts to 50 billion cubic meters per year. Therefore, it is of great significance to apply new technologies and processes to treat blast furnace gas, while strengthening its comprehensive recovery and utilization to improve the efficiency of its use.