In a recent breakthrough, the fourth sulfur plant at Qilu Petrochemical Refinery achieved an impressive sulfur dioxide (SO₂) concentration of just 39-89 mg/m³ in flue gas. This remarkable result, obtained on July 9th by researchers from Qilu Petrochemical Research Institute, marked a major success in the development of upgraded SO₂ emission standards. The data not only confirmed the effectiveness of the new technology but also demonstrated that the sulfur recovery system has reached world-leading levels.
In March of this year, the refinery took advantage of maintenance downtime to upgrade the liquid sulfur degassing process at the fourth sulfur plant. During the renovation, the newly developed low-temperature, oxygen-resistant, and high-stability Claus tail gas hydrogenation catalyst was introduced. Additionally, desulfurization waste gas was directed into the hydrogenation reactor for treatment, while a high-efficiency desulfurization solvent was also used. Through the combined efforts of multiple teams, these new technologies significantly reduced sulfur dioxide emissions. Since mid-April, the flue gas SO₂ levels have remained consistently below 100 mg/m³—far exceeding even California’s strict standard of 143 mg/m³ and placing the facility at the forefront of global sulfur recovery technology.
With China set to implement stricter environmental regulations, the sulfur dioxide emission limit for sulfur plants is now set at less than 400 mg/m³ nationwide, and under 200 mg/m³ in special areas. These new standards pose higher demands on sulfur recovery technologies and catalysts. To meet these requirements, Qilu Petrochemical Research Institute began developing a new emission reduction process in 2012. Researchers worked closely with the refinery to implement a series of advanced technologies and strategies aimed at minimizing sulfur dioxide concentrations in flue gas.
The first step involved developing a new liquid sulfur degassing process. Traditionally, waste gas from the sulfur stream was treated in an incinerator, which contributed significantly to SOâ‚‚ emissions. The new process uses purified tail gas as a stripping agent, directing the degassed waste gas into the hydrogenation reactor. There, it undergoes hydroconversion to form hydrogen sulfide, which is then recovered by amine solution and returned to the sulfur unit for reuse. This approach greatly reduces SOâ‚‚ levels in the flue gas.
The second step focused on using a high-efficiency desulfurizer. Most of the SO₂ in flue gas originates from hydrogen sulfide in the purified gas. The new desulfurizer can reduce hydrogen sulfide content to below 20 mg/m³ under specific conditions, further lowering overall emissions.
Thirdly, the project incorporated optimized catalyst grading to maximize catalytic reactions and minimize organic sulfur compounds in the tail gas. Finally, the team adjusted process control parameters and optimized the operation of the exhaust gas purification system to ensure consistent and effective sulfur dioxide reduction.
This process improvement not only drastically lowered SOâ‚‚ emissions but also cut production costs by 50 yuan per ton of sulfur. With an annual sulfur output of 210,000 tons, the company estimates an annual cost saving of over 10 million yuan.
[Editor: Chen Guofang]
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