A company's 5 000t/d cement production line employed traditional asbestos board seals at the shaft end of its kiln ID fan. This configuration presented issues such as high material brittleness, susceptibility to wear, and severe air leakage at the shaft end. Analysis indicated a large gap (2mm) between the asbestos plate and the fan shaft in this sealing structure. Furthermore, the bypass damper of the SP waste heat boiler was maintained at 8% opening, leading to cold air infiltration, reduced thermal efficiency, limited waste heat power generation load, and frequent maintenance. A modification scheme was proposed, implementing a dual sealing structure combining reinforced graphite blocks and silicone plates. This design controls the gap between the fan shaft and the silicone plate to 3mm, while achieving zero clearance between the graphite block and the fan shaft. The structure features self-compensation and self-lubrication properties, making it suitable for high-temperature and high-negative-pressure conditions. After the modification, shaft end air leakage was completely eliminated, allowing the SP boiler bypass damper to be fully closed. The inlet air temperature of the vertical mill increased stably by 10℃. The waste heat power generation load increased by approximately 10kW·h/h, resulting in an annual electricity saving of about 45 000kW·h. The comprehensive economic benefit amounts to approximately 26 200 CNY per year. The maintenance cycle for the sealing structure has been extended from about 2 months to over 10 years. This modification significantly improves system thermal efficiency and economic performance, demonstrating considerable potential for broader application.