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How much do you know (Nov 28, 2022)
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Original title: How much do you know about the types, uses and principles of heat exchangers in the petrochemical industry? At this stage, in the petrochemical industry, the application of heat exchanger is very extensive. Next, Xiaobian shares with you the types and use principles of heat exchangers in the petrochemical industry. Heat pipe heat exchanger in petrochemical industry Generally, the heat pipe heat exchanger is widely used in the harsh conditions of recovering waste heat in the petrochemical industry, mainly including the production of high-sulfur fuels and other harsh conditions. In the production process of petrochemical industry, the key facilities are high-temperature heating and cracking facilities. Specifically, the temperature of the exhaust gas of the high-temperature petroleum brain cracking furnace selected in the production of small molecular olefins can reach 200 ℃ ~ 400 ℃, and the harsh working conditions are not conducive to the evacuation of tail gas formed by industrial production. The air preheating heat pipe type heat exchanger can heat the air by means of the residual temperature of the waste gas, thereby playing a role in supporting combustion, on the one hand, playing a role in saving energy and reducing consumption, and on the other hand, being beneficial to recovering tail gas and avoiding the deterioration of air pollution. In today's era, a variety of tubular heat exchanger combinations have been widely promoted at home and abroad, which can achieve a good effect of energy drainage. Expand the full text Heat pipe is a kind of heat transfer element with extremely high thermal conductivity, which transfers heat through the evaporation and condensation of working fluid in a fully enclosed vacuum tube. It has a series of advantages, such as extremely high thermal conductivity, good isothermal property, the heat transfer area of both cold and hot sides can be changed arbitrarily, long-distance heat transfer, temperature control and so on. The heat exchanger composed of heat pipes has the advantages of high heat transfer efficiency, compact structure and low fluid resistance loss. Because of its special heat transfer characteristics, it can control the wall temperature and avoid dew point corrosion, and has been widely used in metallurgy, chemical industry, oil refining, boilers, ceramics, transportation, textile, machinery and other industries for heat recovery and comprehensive utilization of heat energy in the process, which has achieved remarkable economic benefits. There are three main types: Gas-gas heat pipe heat exchanger (heat pipe air preheater) Gas-gas heat pipe heat exchanger is a new type of heat exchanger which absorbs waste heat from the discharged hot air and then transfers the heat to the cold air, similar to the air preheater commonly used in boilers. Air preheaters,decarboxylation after extraction, like Economizers and superheaters, are a normal and necessary part of a large boiler. The air preheat accelerates that fuel dry process, reduces the difficulty of igniting low-value fuel and wet fuels, expands the economic combustion of these fuels, and also increases the overall steam production of the boiler. Gas-liquid heat pipe heat exchanger (heat pipe economizer) Heat pipe has a broad field in industrial waste heat recovery and energy utilization. Gas-liquid heat pipe heat exchangers are used to recover heat from flue gas to heat water for reuse. It is very economical and easy to achieve, and the effect is very satisfactory, especially for the high temperature smoke exhaust furnace, the smoke exhaust temperature is high, which is more superior. The gas-liquid heat pipe heat exchanger inserts one end of the heat pipe from the exhaust end, and each heat pipe is wound with fins on the pipe wall to increase the heat absorption surface. The other end is placed in the water tank, and when the high-temperature flue gas passes through the heat absorption section, the heat pipe medium evaporates to generate steam to the other end to release heat and heat the water in the water tank. And is particularly suitable for high flue gas waste heat utilization. Gas-steam heat pipe heat exchanger In that gas-steam heat pipe heat exchange structure, a condensation section of a heat pipe is arranged in a boil,rotovap distillation, an evaporation section of the heat pipe is inserted into an exhaust flue of the boiler, heat is transferred through the heat pipe, and cold wat is added to 100 deg C to obtain required boiling water and also can be heated into steam of which the temperature is more than 100 deg C. Spiral Baffle Heat Exchanger in Petrochemical Industry Helical baffle heat exchanger is a modern and efficient heat exchange facility, which has been widely used in many countries and regions in the world. Since the 1950s, China's petrochemical industry began to promote the application of spiral baffle heat exchangers, and at the same time, in the mid-1960s, the batch production of roll bed rolling was realized. At the same time, the development of spiral baffle heat exchanger technology in China is also very fast. Compared with the traditional heat exchanger, the spiral plate heat exchanger has many advantages. It can heat and cool alcohols, resins, urea, small molecular monomer polymerization olefins, gasoline and diesel oil, ammonia water, chlorine water, saline, strong base and strong acid, nitrogen-hydrogen-ammonia mixed gas and the like. Baffle is an important component to improve the efficiency of heat exchanger. The most commonly used baffle in the traditional heat exchanger is the segmental baffle, which is gradually replaced by the helical baffle in recent years because of the existence of large resistance and pressure drop, flow stagnation, easy fouling, small average temperature difference of heat transfer, easy failure under vibration conditions and other defects. An ideal helical baffle should have a continuous helical surface. Because of the difficulty of processing, wiped film evaporator ,winterization filtration, the folding willow plate used at present is generally connected by several 1/4 fan-shaped flat plates instead of curved surfaces to form an approximate spiral surface. When baffling, the fluid is in a state of approximate spiral flow. Compared with segmental baffles, such baffles (called discontinuous helical baffles) can reduce the pressure drop by about 45% under the same working conditions, while the overall heat transfer coefficient can be increased by 20% -30%, and the size of the heat exchanger can be greatly reduced under the same heat load. The difference between the spiral baffle heat exchanger and the ordinary shell-and-tube heat exchanger is that the baffles in the shell side are arranged in a spiral shape, so that the medium in the shell side is spirally and continuously rotated from the inlet to the outlet, and the traditional transverse baffle mode is changed into a longitudinal spiral baffle mode. As that medium in the shell pas of the heat exchanger is in a spiral plunge flow mode, a velocity gradient is generated in the radial direction of the cross section of the shell pass, and each heat exchange tube is arranged in a vortex of the heat exchange medium, the radial turbulence degree of fluid is improve, which is beneficial to scouring particles and sediments in the shell pass and preventing fouling deposition. Thin film evaporators in petrochemical industry According to the causes of film formation and flow direction, it can be divided into three types: climbing film evaporator, falling film evaporator and wiped film evaporator. The film evaporator unit is composed of evaporator, vapor-liquid separator, preheater and a simple separator. The evaporator is a rising film tube heat exchanger. The thin film evaporator consists of one or more heated cylinders with jackets and a rotating film scraper in the cylinder. The wipers continuously scrape the feed into a uniform film on the heating surface and move it downward; in the process, the low-boiling components are evaporated and the residue is discharged from the bottom of the evaporator. In general, thin film evaporators are mainly used in caustic soda concentration, sodium sulfide evaporation, resin and rubber drying and other processes in the petrochemical industry, and the application of thin film evaporators can achieve very huge economic profits. Thin-film evaporators have the following advantages over conventional, general-purpose facilities such as cast-iron cauldrons. 1) that occupy area is relatively small, the mechanized evaporation can be carry out, the use is very simple, and the operation efficiency is very high. 2) Under the driving force of the rotor scraper, the thin film evaporator can achieve a very good heat transfer effect, and the surface evaporation time of the thin film evaporator becomes shorter, so that it is difficult to scale and coke, and it will not cause the accumulation of excessive sediment, which is conducive to scale removal. And 3) the heat-conducting oil furnace matched with the film evaporator does not consume too much fuel such as coal mine and the like, and can save a large amount of energy. 4) The use of thin film evaporator is conducive to the design of process scale-up, can replace the kettle dryer, and is conducive to reducing the error in the scale-up production process. However, in the process of practical application, the application of thin film evaporator also has some bottlenecks. The material of the groove scraper of the thin film evaporator is polytetrafluoroethylene, which has strong corrosion resistance, but it is difficult to resist high temperature. In order to deal with this problem, corrosion resistant and high temperature resistant materials such as graphite can be used. At the same time, the process pipeline of the thin film evaporator is seamless pipe, which must be replaced once a month. In order to deal with this problem, stainless steel or pipes with corrosion-resistant lining, such as fluoroplastic heat exchanger lining, can be used to ensure that the pipes are not corroded. 4 High efficiency plate heat exchanger in petrochemical industry The high efficiency plate heat exchanger is realized by using different commutator segments and different assembly methods, which can be divided into single process, multi-process and mixed process, and should be selected according to the process requirements. For the medium with general temperature difference greater than 1.8 times of logarithmic mean temperature difference, multi-flow process shall be adopted, and the adaptive value of flow rate between plates shall be 0.3 ~ 0.5m/s. When the flow rate is too low, double or multi-flow process shall be adopted. High efficiency plate heat exchangers are used for liquid heat exchange in the pharmaceutical, food and chemical industries, as well as for pasteurization in certain applications. In the petrochemical industry, the types and quantities of heat exchangers are very numerous, and they also have very high requirements for pressure and temperature. High efficiency plate heat exchangers are better able to cope with higher pressures and higher temperatures. In particular, the welded plate heat exchanger is convenient, small in size, light in weight, has good heat transfer performance, and low in price, so that the welded plate heat exchanger is well used in the offshore oil production process, and can be used for cooling mechanical lubricating oil and fresh water, cooling related intermediate products in an oil field, and heating crude oil. The application of high efficiency plate heat exchanger in the petrochemical industry also has some bottlenecks, that is to say, it is difficult to accurately design and calculate the process flow. In the production practice of the petrochemical industry, huge economic losses often occur due to the unreasonable design of the process flow. In order to solve this problem, we can calculate and analyze the resistance of the plate heat exchanger for cooling in the petrochemical industry. According to the characteristics of the heat exchanger and the assumption of the heat conduction principle that the liquid phase on the wall increases linearly along the flow channel, we can simulate the relationship between the length of the flow channel, the real mass gas content and the volume gas content, which is close to the actual data. In the cooling process of petrochemical industry, there is partial collective condensation, which will form a liquid film on the heat exchange surface. Therefore, compact heat exchangers such as plate-fin heat exchangers can be selected. At the same time, in order to achieve a reasonable and economical heat exchanger, the heat exchanger must be adjusted from the perspective of structural parameters. It is not perfect to consider only the heat exchange area and margin. Editor Sum up Being familiar with the types, uses and principles of heat exchangers in the petrochemical industry can effectively avoid the premature damage of heat exchangers, improve the energy efficiency of the petrochemical industry,thin film distillation, prevent unnecessary shutdown, and avoid the loss of products caused by the problems of heat exchangers. —————————————————————— Disclaimer: The copyright of this article belongs to the original author. If copyright is involved, please contact to delete and return to Sohu to see more. Responsible Editor:. toptiontech.com
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