【SeaChuan’s Insights from Other Sources】Maoming Petrochemical: Minor upgrades help solve the problems affecting the stable operation of the limestone processing system

Thread Content

Maoming Petrochemical: Minor technical upgrades help resolve issues affecting the stable operation of limestone systems 2019-01-18 Source: Sinopec News Network. The high failure rates of the four limestone systems in the two CFB boilers located in Maoming Petrochemical’s chemical industry zone have been a persistent problem for the employees of the Power Department 2 in that facility. Due to design reasons, the minimum operating speed of the rotary feed valve in the limestone system is too high; as a result, it is not possible to meet the operational requirements for fuels with low sulfur content. If the system operates at a low speed, the motor will shut down due to the increased torque resulting from the low speed, which leads to insufficient addition of limestone into the furnace and thus excessive SO2 emissions in the flue gases. On the other hand, if the speed is increased, excessive addition of limestone will cause an increase in NOx levels, potentially exceeding permissible limits. To ensure the stable and green operation of CFB boilers, it is necessary to completely eliminate this \"persistent problem\". To replace the motor, the best and most direct method is to use a low-power limestone rotary feed valve to drive the motor for replacement. However, the cost of four motors is over 300,000 yuan, and it is difficult to secure the funds; as a result, new motors have not been acquired. The stable operation of these four sets of limestone processing equipment has always been a source of concern for Liang Zhu, the deputy director of Workshop 2. He actively sought solutions. He obtained the original drawings of the equipment, observed the operation of the system on site, and analyzed the impact of the rotation of the rotary feed valve on the fuel supply to the furnace. Through in-depth analysis and research, Liang Zhu came up with the bold idea of changing the speed ratio between the driving sprocket of the limestone feed valve motor and the driven sprocket of the feed valve. This innovative idea was supported by the workshop’s technical team. The key technical personnel in the workshop work together to conduct technical evaluations, assess operational risks, develop practical renovation plans, as well as safety measures for the construction work. On December 1 of last year, Liang Zhu began working on the renovation of the limestone system, carrying out renovations to the drive gears of the rotary feed valves in four different systems over the course of just one week. The remanufactured drive gear increases the number of teeth from 26 to 52; by increasing the number of teeth, the rotation speed of the limestone rotary feed valve is reduced, thereby improving the operating conditions of the motor. After the modification was completed on December 8, tests showed that it was possible to reduce the rotation speed of the rotary feed valve by half while keeping the number of teeth on the motor’s driving gear unchanged. Based on the performance over more than a month, after this minor modification was implemented, the amount of limestone added was reduced by half; there were no instances of motor shutdowns, and the control of sulfur dioxide and nitrogen oxide emissions became more stable. (Weng Qiaoshu, Zou Binbin)