Precautions for graphite heat exchangers

         Reminder for the precautions of graphite heat exchangers: Overtemperature and overpressure operations are strictly prohibited during use, and sudden changes in temperature and pressure should be prevented. All valves should be opened slowly and gradually adjusted to be larger or smaller. During steam heating, prevent violent impacts of steam. When operating the equipment, heat up slowly, and after the graphite components tend to reach a uniform temperature, slowly increase the pressure until it reaches the normal operating pressure. The operation during the preheating process is very important. Operating steps: First, pass through the cold carrier (material medium), and after the equipment is filled, pass through the hot carrier (steam or hot water); when stopping, first stop the hot carrier (steam or hot water), and after the equipment cools down, stop the cold carrier (material medium). Check the acidity and alkalinity of the condensate water irregularly, analyze the material composition of the tube side and shell side regularly, and verify whether there is any leakage.

        Before starting the graphite heat exchanger, clear the impurities from the process pipeline to prevent blockage of the graphite pores. Try to minimize the number of equipment start-ups and shutdowns to extend the service life of the equipment. When the heat transfer capacity of the equipment decreases, it should be shut down for inspection. If the equipment is severely scaled, appropriate physical or chemical methods can be used for cleaning; if the inside of the tube is blocked by crystalline substances, it can be heated and melted for cleaning. Since graphite is a brittle material, mechanical methods are strictly prohibited. The high (low) part of the shell is equipped with an exhaust (cleaning) pipe. When installing, a valve should be installed before connecting the exhaust (cleaning) pipe. It is strictly prohibited to use a blind plate for blind sealing. Before starting to use the equipment, the vent valve at the top of the shell should be opened, and it should be closed after the air inside the shell is completely purged. During use, it is necessary to regularly discharge the non-condensable gas at the top of the shell side and the condensed water at the bottom.

        The larger the particle size of the graphite matrix, the lower the bulk density of the material and the lower the mechanical strength. The larger the pores between particles, the more through-holes may be exposed during drilling, leading to an increase in porosity. To achieve the required compactness for application, the amount of impregnant will increase, affecting the quality of the impregnation and the thermal conductivity of the impermeable graphite. Higher density leads to greater mechanical strength. Therefore, selecting a matrix with high bulk density (fine particles, Grade B) for impregnation and heat treatment results in equipment with high quality stability and safety, and good application performance. The impregnant in graphite heat exchangers fills the voids in the graphite matrix, and the type of impregnant directly affects the corrosion resistance of the impermeable graphite. Different impregnation amounts affect the operating temperature and corrosion resistance of the impermeable graphite. Higher impregnation vacuum and pressure can reduce the number of impregnation cycles, and the heat exchange effect is also superior to traditional impregnation processes (three rounds of impregnation and heat treatment).