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,
jacketed glass
reactor, 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,
decarboxylation
after extraction, 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 ,
rotovap
distillation, 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,
winterization
filtration, prevent unnecessary shutdown, and avoid the loss of products
caused by the problems of heat exchangers. —————————————————————— Disclaimer:
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