What Are the Categories of Impervious Graphite for Graphite Heat Exchangers?

Graphite heat exchanger is a kind of heat transfer equipment made of impervious graphite as the base material, and is widely used in the heat exchange process of high temperature, high pressure, and strongly corrosive medium in chemical, metallurgy, power and other industries.

Impervious graphite is impervious to gases, steams, liquids and other fluid media, which makes graphite heat exchanger have excellent performance in handling various media. According to the manufacturing process, impervious graphite is divided into impregnated impervious graphite, pressed impervious graphite and cast impervious graphite.

Close up shot of animpervious graphite block on the floor
Impregnated Impervious Graphite

In order to compensate for the micropores formed in artificial graphite during the roasting and graphitization due to the decomposition and condensation of organic matters, various chemical stabilizers are used to impregnate the graphite to prevent the penetration of gases and liquids. After impregnation and solidification, the graphite material has higher mechanical strength, with compressive strength increased by 1–2.5 times, tensile strength increased by 4–5 times, flexural strength increased by 2–3 times, and impact strength increased by 2–2.5 times.

In this process, the selection of impregnating agent is very important, as its properties largely determine the chemical stability, thermal stability, mechanical strength, operating temperature and range of impregnated graphite. In the chemical industry, commonly used impregnating agents include phenolic resins, modified phenolic resins, furfural acetone resin, furfuryl alcohol resin, organosilicon resin, sodium silicate, pitch, etc.

Pressed Impervious Graphite

Pressed graphite is a kind of molded graphite product. It is made by mixing artificial graphite powder and binder in a certain proportion to form a paste, and then extruding or molding it in a mold, and then solidifying it by heating. The binder used can be thermosetting resin, thermoplastic resin, pitch or other adhesives. The pressed graphite material is dense and non-porous, and does not need to be impregnated with synthetic resin. It has good chemical stability, thermal conductivity, heat resistance, thermal stability, and mechanical processing properties. Graphite itself also has good self-lubricating properties and can be used as a wear-resistant material.

The mechanical strength of pressed graphite material is 1–1.3 times higher than that of pure carbon graphite material and impregnated graphite material. The production process of pressed graphite material is simple, with a short cycle and low cost. Equipment made with pressed graphite material is much cheaper than those made of lead, enamel, and stainless steel. Therefore, it has been widely used in the industrial sectors of chemical, petroleum, metallurgy, papermaking, textile, etc.

Cast Impervious Graphite

Cast graphite is a corrosion-resistant impervious graphite product made by using thermosetting synthetic resin as binder, artificial graphite powder as filler, and then adding a curing agent, and then casting it under normal temperature (or heating) and pressure. This material has good chemical stability, heat resistance, and compressive strength. Among them, the performance of the resin determines the chemical stability and thermal stability of the cast graphite. Cast graphite has good fluidity, and can be used to manufacture parts by using common casting methods at normal temperatures and without pressure. These parts can be cast in sand molds or metal, PVC molds (or wooden molds are also available).

Cast impervious graphite can be used to make pumps, valves. Plugs, pipes, pickling tanks, heat exchangers, reaction vessels, absorption columns, etc. Cast graphite can be used as independent structural material, or as a lining material.

In short, impervious graphite for graphite heat exchangers, as an important heat exchange material, has a broad range of application prospects in chemical, metallurgy, power and other industries. With the continuous advancement of technology and the expansion of application fields, we believe that impervious graphite heat exchangers will play an important role in an increasing fields.