High-efficiency heat exchange technology for porous surface high-throughput tubes
Thread Content
This is a carbon-reduction technology suitable for the utilization of low-grade heat in the petroleum and chemical industries. In the petrochemical industry, the heat exchange tubes of heat exchangers operating in boiling conditions, such as reboilers and steam generators, are usually plain tubes, which leads to a problem of low heat exchange efficiency. The enlargement of equipment is the future development trend in China’s petrochemical industry; however, issues such as large sizes and high numbers of heat exchangers due to low efficiency are particularly prominent, which hinders the utilization of low-grade heat. By replacing the optical tubes with high-throughput tubes featuring porous surfaces, the heat exchanger gains advantages such as a small required heat transfer temperature difference and high heat transfer efficiency. This enables better utilization of waste heat of lower quality, while effectively reducing the number and size of heat exchangers and improving the efficiency of the compressor. Currently, porous surface high-throughput tube heat exchangers have been successfully applied in large-scale chemical plants such as those for producing millions of tons of ethylene, 600,000 tons per year of methanol for olefin production, and 500,000 tons per year of ethylene glycol from coal, achieving good energy-saving results. This technology is a type of heat transfer enhancement technique used to improve the efficiency of boiling heat transfer; it achieves this by creating a metal porous layer on the surface of ordinary heat exchange tubes, thereby enhancing boiling heat transfer. The metal porous layer provides a large number of nucleation sites, enabling heat transfer to remain in an efficient nucleated boiling state; this results in a boiling heat transfer coefficient 3–8 times higher than that of smooth tubes, thereby effectively reducing the size and quantity of heat exchangers required ； At the same time, the porosity of the surface allows large-diameter bubbles to form easily within the medium, which reduces the superheat required to reach boiling and decreases the heat transfer temperature difference. As a result, it is possible to utilize waste heat of lower quality, improving compressor efficiency and contributing to energy savings and carbon reduction.
High-throughput tube heat exchangers and reboilers, as key devices for providing the thermal energy required in plant operations, feature high flow rates and high heat loads; their heat exchange efficiency plays a vital role in reducing the plant’s energy consumption, saving on investments, and lowering operating costs. In previous units for aromatics, ethylene glycol, etc., the bottom reboilers typically used conventional vertical shell-and-tube heat exchangers, which had disadvantages such as low heat transfer efficiency, a large heat transfer area required for the same heat transfer load, and oversized equipment. For large-scale single units, it is necessary to use two or more units in parallel; however, when multiple units operate in parallel, it is difficult to evenly distribute the thermal load and material flow, which becomes a bottleneck in the renovation of such units. Using a high-flow tube heat exchanger to replace traditional shell-and-tube heat exchangers can solve the aforementioned problems, but this high-flow tube manufacturing technology has long been monopolized by foreign patent holders. In recent years, with the overall improvement of domestic refining and chemical processing technologies, domestically produced high-throughput tube heat exchangers have seen significant development. High-throughput tube heat exchangers are created by using special processing methods such as powder metallurgy to uniformly cover the surface of ordinary heat exchange tubes with a porous metal thin coating that contains numerous micropores and interconnected tunnels, thereby forming a porous surface that increases the number of vaporization nuclei and enhances boiling heat transfer ； Therefore, its heat transfer coefficient is high, ranging from 3 to 8 times that of a light tube. Due to the strong capillary action and high recirculation rate of the porous structure, the liquid within the micropores is continuously circulated as a result of the expansion and contraction of bubbles; the flow rate of fluid on the porous surface is 10 to 15 times that of the optical tube. This extensive liquid circulation affects the surface of the heat exchange tube