【Haichuan’s Best Practices】Using finned tubes to reduce the temperature of the sampling pipeline for the water in pyrolysis furnaces

Thread Content

This post was last edited by “Fish Swimming in the Desert” on September 7, 2020, at 18:34. According to Sinopec News Network, starting from August 25, the water sampling pipeline for Furnace No. 7 of the ethylene cracking unit at Zhenhai Refining & Chemical was fitted with a new finned air-cooling system. Data from a one-week trial indicate that this innovative measure **has improved the accuracy of online furnace water analyzers while also achieving significant water savings.** The boiler water online analyzer measures in real time the data of the boiler water that enters the cracking furnace; this boiler water is used to generate ultra-high pressure steam. The accuracy of the analysis data has a direct impact on the quality of the steam, which in turn affects the operating condition of the large-scale equipment. For a long time, the online water analyzers installed in the 12 cracking furnaces of the ethylene cracking units have suffered from a high failure rate; the innovative problem-solving team at Zhenhai Refining & Chemical Co., known as the \"East Sea Furnace Kings,\" has been working continuously to address this issue. After analysis and assessment, the problem-solving team determined that the high temperature of the boiler water entering the online analyzer was the cause of scaling. The cross-section of the boiler water sampling pipeline is ring-shaped, with an inner tube surrounded by an outer tube; the fluid flowing through the inner tube is high-pressure boiler water at 300°C, while the outer layer contains circulating water used for cooling – yet the cooling effect of this circulating water is not sufficient. The first approach considered by the research team was to remove the insulation layer to allow heat to dissipate and to discharge the circulating water on-site, but this method was ineffective and resulted in significant waste of circulating water. The research team kept searching for relevant information and conducting simulations on multiple occasions; eventually, they were inspired by computer CPU fans and designed their own fan-blade-shaped air-cooling \"cover\" to increase the heat exchange area between the pipelines and the air. The air-cooling \"cover\" can be installed using clips, without the need for welding; it does not interfere with the use of existing pipelines. The design cost per unit is only 1,000 yuan, and the total cost for installing all 12 pyrolysis furnaces is 12,000 yuan. This approach allows the desired goals to be achieved with minimal overall investment and few changes. Currently, since the boiler water sampling pipeline for Reactor No. 7 was put into use, the boiler water inlet temperature at the analyzer has dropped from 180°C to around 100°C, showing significant effects. It is estimated that after the universal retrofitting of 12 pyrolysis furnaces, while reducing failures of on-line analyzers, 25 tons of circulating cooling water can be saved per hour. (Bian Jiangqi, Wang Na)