In the phosphoric acid concentration process, the bonded graphite heat exchanger has always been in a dominant position. With the continuous progress of science and technology, new equipment manufacturing technologies continue to emerge, and a new type of national patented product-"Boao" brand combined shell & tube phosphoric acid concentration heat exchanger has emerged. The birth of this technology completely eliminates the stress damage caused by the obvious difference in the linear expansion coefficient of the two different materials of the binder and the impregnated graphite block on the traditional graphite heat exchanger structure, and has become a replacement product for phosphoric acid concentration equipment. Next, I will explain the elastic sealing principle and structure of the combined shell & tube graphite heat exchanger.

1) Principle Three types of rubber rings (straight ring, O-ring, trapezoidal ring) are installed at both ends of the graphite heat exchanger, and the extrusion force of the tube sheet and the supporting force of the graphite tube and the rubber ring are used to generate a joint This kind of deformation stress, thus playing a sealing role.

2) Structure The elastic seal is composed of one main seal and two auxiliary seals. The main seal is a straight ring, and the O-ring and trapezoidal ring are auxiliary seals.

3) Material The material of the elastic rubber seal is divided into two materials: EPDM rubber and fluorine rubber.

4) The straight ring is located at the innermost ends of both ends of the graphite tube and directly contacts the corrosive medium to act as the main seal; the O-ring is located between the straight ring and the trapezoidal ring and acts as an auxiliary seal under the extrusion of the trapezoidal ring. Function: The trapezoid ring is located on the outermost side of the graphite tube, which has a locking and leak-proof effect.

5) Assembling method: Process both ends of the graphite tube into a suitable size, ream holes in a certain size on the inside of the graphite tube plate, first install the straight rubber ring into the sealing position of the tube plate, and then drive one end of the graphite tube into the straight ring Then drive the graphite tube into the sealing position of the graphite tube plate on the other side. The O-ring and the trapezoidal ring are respectively installed from the outside of the graphite tube sheet.

1.2 The structural characteristics of the combined shell & tube graphite heat exchanger

Graphite is used as the structural material, and the tube plates at both ends are fixed tube plates. The tube plate and the heat exchange tube are combined with highly elastic and corrosion-resistant materials to achieve elastic sealing connection. This kind of graphite heat exchanger has simple structure, shock resistance, good heat transfer performance, low operation resistance, easy maintenance and management, and completely eliminates the linear expansion coefficient of two different materials of traditional graphite heat exchanger structure due to binder and impregnated graphite block. The operation is still stable and reliable even under the process conditions with large temperature difference caused by the obvious difference; the equipment adopts the socket type live connection, which is convenient for maintenance, simple for pipe exchange, and the heat exchange area is not reduced to avoid pipe blockage. The whole machine is scrapped.

1.3 Technical performance of combined shell & tube graphite heat exchanger

The allowable pressure is 1.0MPa; the allowable temperature is -20～150℃; the maximum vacuum degree is 93.3KPa when the tube pass is decompressed.

1.4 The scope of application of combined shell & tube graphite heat exchanger

The tube side medium is corrosive material. Because the heat exchange tube adopts phenolic impregnated graphite with good thermal conductivity, good chemical stability and thermal stability, its corrosion resistance is good, except for strong oxidizing strong acids, strong alkalis, certain solvents and It is resistant to various organic acids, inorganic acids, alkalis, salts, organic compounds and other corrosive materials except for easy crystallization and scaling media. The shell side normally passes through non-corrosive media, such as water, neutral salt water, water vapor, etc.