Graphite not only has acid corrosion resistance, but also has good thermal conductivity. The graphite core is made into a block hole structure with vertical and horizontal separation. When the two media pass through each other, the high-temperature medium continuously transfers heat to the graphite heat exchanger, and the low-temperature medium continuously obtains heat from the heat exchanger, thus realizing heat exchange. Graphite heat exchanger is a kind of heat exchanger whose heat transfer element is made of graphite. Graphite used to make heat exchangers should be impermeable, such as impregnated graphite and pressed graphite. According to its structure, graphite heat exchangers can be divided into three types: plug hole type, shell-and-tube type and plate type. Block hole type: it is assembled by several block graphite components with holes. Shell-and-tube heat exchanger: Shell-and-tube heat exchanger plays an important role in graphite heat exchanger, which can be divided into fixed type and floating type according to structure. Plate: The plate heat exchanger is made of bonded graphite plates.
According to its structure, graphite heat exchangers can be divided into three types: plug hole type, shell-and-tube type and plate type. Block hole type: it is assembled by several block graphite components with holes. Shell-and-tube heat exchanger: Shell-and-tube heat exchanger plays an important role in graphite heat exchanger, which can be divided into fixed type and floating type according to structure. The plate heat exchanger is made of bonded graphite plates. In addition, there are immersion type, spray type and sleeve type (see snake tube heat exchanger and sleeve type heat exchanger). Graphite heat exchanger has good corrosion resistance, heat transfer surface is not easy to scale and heat transfer performance is good. However, graphite is fragile and has low bending and tensile strength, so it can only be used at low pressure. Even for the block structure with the best bearing capacity, its working pressure is generally only 0.3 ~ 0.5 MPa. Graphite heat exchanger is expensive, bulky and not used much. 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.
Advantages: It is suitable for organic solvents and composite media that do not oxidize or weakly oxidize most strong acids, alkalis, salt solutions and organic acids. The thermal conductivity is higher than that of many metals, second only to copper and aluminum, 2 times larger than that of carbon steel and 5 times larger than that of stainless steel, ranking first among nonmetallic materials, and it is suitable for making various heat exchange equipment. Small linear expansion coefficient, high temperature resistance and thermal shock resistance. The surface is not easy to scale and has no pollution. Good machinability. Low density and light weight.
Disadvantages: Graphite heat exchangers can be divided into plug hole type and shell-and-tube type. The main disadvantage of block hole graphite heat exchanger is that it is difficult to find and repair once it leaks. The disadvantage of shell-and-tube graphite heat exchanger is that the strength of graphite tube is relatively low, and the steam pressure used cannot exceed 0.15 MPa; The flow rate of the heated medium is low, which can only be controlled at 2 ~ 3m/s; The temperature difference between the inlet and outlet can only be controlled at 2 ~ 4℃, and the heat exchanger is bulky.