Discussion on the advantages and disadvantages of various types of anti-corrosion heat exchangers

Silicon carbide heat exchangers: They effectively address issues such as corrosion resistance and high-temperature tolerance. Its main advantages are: good thermal conductivity, high strength at high temperatures, and excellent oxidation and thermal shock resistance. Long lifespan, low maintenance needs, reliable and stable performance, and easy to operate. Key features of polytetrafluoroethylene heat exchangers: excellent corrosion resistance, good anti-scaling properties, long service life, low overall cost, good heat transfer performance, low pressure loss, small size, light weight, and a compact structure. Advantages and disadvantages of graphite heat exchangers: Advantages: Suitable for non-oxidizing or weakly oxidizing strong acids, alkalis, salt solutions, most organic acids, various organic solvents, and composite media. Its thermal conductivity is higher than that of many metals, second only to copper and aluminum; it is twice that of carbon steel and five times that of stainless steel. It ranks first among non-metallic materials and is suitable for manufacturing various heat exchange devices. Low linear expansion coefficient, heat resistance, and resistance to thermal shock. It does not scale easily on its surface and is pollution-free. It has good machinability. Low density, light weight. Disadvantage: Graphite heat exchangers are divided into block-and-hole type and shell-and-tube type. The main drawback of block-hole graphite heat exchangers is that leaks are difficult to detect once they occur, and they are not easy to repair. The disadvantage of shell-and-tube graphite heat exchangers is that the strength of the graphite tubes is relatively low, and the steam pressure used cannot exceed 0.15 MPa ； The flow rate of the heated medium is low, and can only be controlled at 2 to 3 m/s ； The temperature difference between inlet and outlet can only be controlled within 2 to 4°C, and the heat exchanger has a large volume.

This post was last edited by wu95423 on 2016-12-14 at 12:55. Silicon carbide heat exchangers are good heat exchangers; O-rings are generally used for sealing between the heat exchange tubes and the tube sheet. The reliability of this sealing plays a significant role in determining the range of applications for such heat exchangers. Double tube sheets help to address the sealing issues between the tube side and the shell side. Additionally, the material of the silicon carbide tubes is also crucial. There are two types of silicon carbide tubes available on the market: those that are sintered under pressure and those that are sintered without pressure. Silicon carbide tubes sintered under pressure have better corrosion resistance, are more expensive, and have a wider range of applications. Polytetrafluoroethylene heat exchangers have poor heat transfer performance; they typically use very thin capillaries, a large number of tubes, and heat fusion welding is employed to connect the tubes to the tube sheet. Our company used it in the past, but it had a high failure rate, so it was later replaced by other heat exchangers. Graphite heat exchangers have decent overall performance and a good cost-performance ratio. The key factor is the choice of resin used to impregnate the graphite; common options include phenolic resin, furan resin, and tetrafluoro resin. Common graphite heat exchanger manufacturers use electrode graphite, which has larger particles; more resin is required for impregnation, and the overall heat transfer coefficient is not high. Corrosion resistance depends mainly on the impregnated resin. The graphite equipment purchased by our company uses ultra-fine chemical graphite with a thickness of 0.8 mm in certain critical applications; the resin used for impregnation is composite resin from a well-known domestic manufacturer. Even in extremely harsh operating conditions, it has functioned without any problems over many years.

PTFE pipes and tube sheets are welded together by heat fusion; so how is thermal stress addressed? I believe that structural design is very important for non-metallic heat exchangers

Silicon carbide, tantalum, and graphite heat exchangers all have excellent thermal conductivity as well as good corrosion resistance. Tantalum heat exchangers offer even more reliable performance, but their cost is very high and they are difficult to weld; only a few companies in China possess the necessary welding techniques for them. Glass-lined heat exchangers: they have good corrosion resistance but poor heat transfer performance, mainly due to the low heat transfer coefficient of the enamel itself. The biggest drawback is its poor resistance to thermal shock, so special care must be taken when using it. Special attention also needs to be paid to the structure. PTFE heat exchangers: good corrosion resistance, but poor temperature and pressure resistance.

Tantalum equipment requires a higher initial investment compared to other types of equipment, but its maintenance costs are very low, resulting in good long-term economic benefits. I work at a foreign-owned manufacturer of tantalum equipment; feel free to get in touch at @186-5291-8271

Due to process constraints, the tube diameter of silicon carbide heat exchangers cannot be too large; the investment required is also significant, and care must be taken when clearing blockages in the tubes

Silicon carbide is resistant to corrosion by almost all chemical agents. However, its drawback is that it tends to develop problems at high temperatures above 200 degrees Celsius and under high pressures above 2 Mpa