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What are the advantages of graphite heat exchangers?
- 2021-02-11-

Graphite heat exchangerThe corrosion resistance and thermal conductivity of stainless steel are better than stainless steel; the pressure resistance of stainless steel heat exchanger is better than that of graphite heat exchanger. The specific material of the heat exchanger to be selected is mainly determined by the process conditions. The applicable is good, and of course the cost performance must be considered. The graphite used in the graphite heat exchanger should be impermeable. Impregnated impermeable graphite and pressed impermeable graphite are commonly used. The graphite heat exchanger has good corrosion resistance, the heat transfer surface is not easy to scale, and the heat transfer performance is good. However, graphite is easy to brittle and has low bending and tensile strength, so it can only be used at low pressure. Even with a block-shaped structure with good pressure bearing capacity, its working pressure is generally only 0.3 to 0.5 MPa. Graphite heat exchangers are expensive, bulky, and not used much. It is mainly used for the heat exchange of corrosive media such as hydrochloric acid, sulfuric acid, acetic acid and phosphoric acid, such as the condenser of acetic acid and acetic anhydride. The big difference between graphite heat exchangers is not the heat transfer performance and corrosion resistance, but the copper tube is less prone to scaling, which is not realized in China.

Foreign commercial boilers do not use water treatment equipment, but their life span is as long as 15 years. The reason is that although water can also generate scale on the copper pipe wall, what it generates is only flocculent scale. In this case, as long as the flow rate of the water is increased, the scale cannot be deposited. Secondly, it is the heat transfer performance. The thermal conductivity of copper is higher than that of stainless steel, so the heat transfer coefficient of copper pipes of the same shape is higher than that of stainless steel. Therefore, the heat exchange tubes used in the graphite evaporator condenser are basically made of copper. And the strength is higher than that of copper, so now the plates of the plate heat exchanger we see are all stainless steel, but the plates at the beginning are also copper.

According to its structure, graphite heat exchangers can be divided into three types: block-hole type, shell-and-tube type and plate type. Block hole type: It is assembled from a number of special block graphite components with holes. Shell-and-tube type: Shell-and-tube heat exchanger occupies an important position in graphite heat exchangers. According to the structure, it is divided into two types: fixed type and floating head type. Plate type: The plate heat exchanger is made of graphite plates bonded together. In addition, there are immersion type, spray type and sleeve type, etc. (see Snake tube heat exchanger, sleeve heat exchanger). The graphite heat exchanger has good corrosion resistance, the heat transfer surface is not easy to scale, and the heat transfer performance is good. Corrosion resistance: suitable for non-oxidized or weakly oxidized strong acids, alkalis, salt solutions, most organic solvents and composite media of organic acids. High thermal conductivity: thermal conductivity is higher than many metals, second only to copper and aluminum, 2 times larger than carbon steel, 5 times larger than stainless steel, ranking first among non-metallic materials, suitable for making various heat exchange equipment.

Graphite heat exchangers are increasingly widely used in cold-rolled pickling lines, chemical, petroleum, and pesticide industries. The article mainly introduces the application of graphite heat exchanger in the pickling capacity line. In the cold-rolling pickling process, the graphite heat exchanger draws acid out of the acid tank through an acid pump, pumps it into the graphite heat exchanger, and is heated by the graphite heat exchanger and discharged back to the other end of the acid tank. Continuously, so it is realized that the graphite heat exchanger heats the acid. The graphite heat exchanger changes the heating method of the acid, makes the acid temperature rise uniformly, shortens the temperature rise time, reduces steam consumption, reduces energy waste, and improves Work efficiency: The graphite heat exchanger increases the fluidity of the acid, produces a certain scouring effect on the surface of the strip steel, and accelerates the process of removing the scale. Compared with the heating method of direct steam heating of the acid solution, due to the change of the heating method, the overheated volatilization of the acid and the dilution of the acid by the condensed water are obviously weakened, and the acid consumption benefit is obviously reduced.