CN204830683U - Polypropylene tail gas recovery unit - Google Patents

Abstract

The utility model discloses a polypropylene tail gas recovery device, which comprises a compression unit, a drying unit, a membrane separation unit and a cryogenic separation unit which are sequentially connected; the compression unit comprises at least one compressor and a heat exchanger which are sequentially connected and a gas-liquid separator; the drying unit includes at least two adsorption towers connected in sequence, and desiccant is housed in the adsorption tower; the membrane separation unit includes a membrane separator; the cryogenic separation unit includes At least one high-efficiency multi-channel heat exchanger, at least one cryogenic gas-liquid separator, at least one gas expansion device, and at least one liquid expansion device. The utility model recovers the polypropylene tail gas through the method of expansion and refrigeration, so that the propylene in the polypropylene tail gas is liquefied, realizes the recovery of propylene, and purifies the nitrogen at the same time to meet the requirements of nitrogen recycling; combined with the membrane separation technology, removes the propylene in the polypropylene tail gas Hydrogen; achieve a recovery rate of more than 98% of propylene in polypropylene tail gas.

Description

A polypropylene tail gas recovery device

technical field

The utility model relates to the field of polyolefins, in particular to a recovery device for propylene and nitrogen in tail gas discharged during the production process of polypropylene.

Background technique

In the production process of polypropylene, during the refining of propylene monomer, polymerization reaction and degassing process of polypropylene resin, tail gas containing a large amount of propylene monomer will be discharged. For example, the small stream of light components coming out of the top of the degassing tower during the propylene refining process, and the reaction purge gas used to control the content of inert gases during the polymerization reaction, the mixed gas of nitrogen + steam is sent from the bottom of the degassing chamber to Removal of hydrocarbons and deactivation of residual catalysts resulting in debinning tail gas, etc. These gases are collectively referred to as polypropylene tail gas, and its main components are nitrogen, propylene and a small amount of propane, ethane, ethylene, water, etc. Generally, the concentration of propylene is about 6-50% (V), and the scale is 300,000 tons/year. In the polypropylene plant, the tail gas contains up to 3,000 tons of propylene and more than 5,000 tons of nitrogen per year, so the recovery of hydrocarbons and nitrogen in the tail gas has very high economic benefits.

US Patent No. 5,769,927 proposes a process for treating polypropylene tail gas by adopting an integrated method of compression, condensation and membrane separation. The flow is described below. First, the polypropylene tail gas is pressurized, and then the gas temperature is lowered below the dew point through the condenser, and a part of the propylene becomes liquid and separated; the other part of the propylene in the gas phase enters the membrane separation part, and the membrane is used to preferentially permeate the propylene. Separation of propylene and nitrogen is achieved, and the obtained propylene-rich gas is returned to the compression and condensation part for further recovery of propylene. This process can realize the recycling of propylene and nitrogen, but because the propylene-rich gas of the membrane returns to the compression and condensation part, the compressed and condensed gas volume after the cycle is 1.5 to 3 times the initial discharge gas volume, which makes the investment of compression and refrigeration equipment Both energy consumption and energy consumption are significantly increased, reducing the economics of the process.

Chinese patent CN101357291B discloses that high-purity product nitrogen is obtained by adsorption at normal temperature and pressure, desorbed under negative pressure, and then the desorbed gas is compressed and condensed to obtain high-purity product propylene liquid. However, this method needs to use a vacuum pump to analyze the adsorption tower, and at least two compressors are required to pressurize the recovered hydrocarbon gas and nitrogen respectively. There are many moving equipment and complicated operation. The vacuum analysis process will easily cause air to infiltrate into the recovery system, which is safe. Hidden danger, when the exhaust gas contains a certain concentration of hydrogen, the adsorption process cannot realize the separation of hydrogen from nitrogen, resulting in nitrogen that cannot be recycled and can only be discharged to the torch, resulting in waste of resources and environmental pollution. At the same time, the equipment occupies a large area .

Utility model content

In view of the above-mentioned problems in the prior art, the utility model aims to provide a polypropylene tail gas recovery device with high recovery rate of propylene, simple reusable process of nitrogen, low energy consumption, low investment and small footprint.

The purpose of this utility model is to provide a polypropylene tail gas recovery device, said device comprising:

A compression unit comprising at least one compressor, a heat exchanger and a gas-liquid separator. It is used to increase the pressure of polypropylene tail gas to meet the operating pressure requirements of expansion refrigeration, cryogenic separation and membrane separation. At the same time, the compressed gas is cooled to normal temperature, and the condensed high boiling point liquid is separated in the gas-liquid separator to obtain Condensate flow and compressed air flow at normal temperature.

The drying unit includes at least two adsorption towers, and the towers are equipped with desiccant, which is used to process the normal temperature compressed gas output from the compression unit, remove the moisture in the gas, and obtain a dry gas flow.

The membrane separation unit, including a membrane separator and a hydrogen separation membrane, is used to process the gas flow output from the drying unit, separate the hydrogen in the gas, and obtain a hydrogen-deficient gas flow.

Cryogenic separation unit: including at least one high-efficiency multi-channel heat exchanger, at least one low-temperature gas-liquid separator, at least one gas expansion device and at least one liquid expansion device. The outlet of the membrane separator is sequentially connected to the hot medium channel C-C of the high-efficiency multi-channel heat exchanger and the inlet of the low-temperature gas-liquid separator; the bottom outlet of the low-temperature gas-liquid separator is connected to the liquid expansion device and the cold medium channel of the high-efficiency multi-channel heat exchanger in sequence D-D, pipeline k; the top outlet of the low-temperature gas-liquid separator is sequentially connected to the cold medium channel A-A of the high-efficiency multi-channel heat exchanger, the gas expansion device, the cold medium channel B-B of the high-efficiency multi-channel heat exchanger, and pipeline o; used for processing The hydrogen-depleted gas stream output from the membrane separation unit further reduces the temperature of the gas through expansion refrigeration and multi-fluid heat exchange to realize the liquefaction of propylene, and through gas-liquid separation, the recovered propylene stream and nitrogen stream are obtained.

Further, in the above technical solution, in the drying unit, the desiccant is selected from activated alumina, silica gel, and molecular sieves.

Further, in the above technical solution, the hydrogen separation membrane refers to various separation membranes that can preferentially permeate hydrogen relative to hydrocarbons and nitrogen, such as polyimide, polysulfone, polyaramid, acetate fiber, Separation membranes of polymer materials such as polyphenylene oxide, or metal membranes such as palladium membranes.

Further, in the above technical solution, the expansion device refers to a refrigeration device that converts the pressure energy of the fluid into cooling capacity, and the liquid expansion device is selected from a throttling expansion valve.

The gas expansion device is selected from a turbo expander and a gas wave refrigerator.

Further, in the above technical solution, the high-efficiency multi-channel heat exchanger refers to a plate-fin heat exchanger or a coiled-tube heat exchanger.

The device of the utility model can effectively recover propylene and nitrogen in the tail gas through the organic combination of the compression unit, the drying unit, the membrane separation unit and the cryogenic separation unit. The recovery rate of propylene is above 98%, and the purity of the recovered nitrogen is 97.5% %above.

Another purpose of this utility model is to provide a kind of method utilizing described polypropylene tail gas recovery device to reclaim propylene and nitrogen, it comprises the following steps:

In the compression step, the polypropylene tail gas first passes through the compressor to increase the pressure of the gas to 0.6-3.0MPaA, and then passes through the heat exchanger to reduce the temperature of the compressed high-temperature gas to normal temperature. The cooling medium uses circulating water, and the cooled gas is in the The gas-liquid separation is carried out in the gas-liquid separator, and a part of the high boiling point components in the tail gas, such as water and heavy hydrocarbons, will turn into a liquid phase and be discharged from the bottom of the gas-liquid separator as a condensate.

In the drying step, the gas phase from the gas-liquid separator enters the dehydration adsorption tower to remove the moisture in the exhaust gas and lower the water dew point to below -30~-130°C.

In the membrane separation step, the dehydrated and dried gas enters the membrane separator, which is equipped with a hydrogen separation membrane. The membrane is characterized by preferentially permeating the hydrogen component, which can separate the hydrogen in the tail gas, and the permeated hydrogen-rich gas is discharged to the torch. The gas, freed of most of the hydrogen, enters a cryogenic separation step.

In the cryogenic separation step, the gas from which most of the hydrogen has been removed enters the high-efficiency multi-channel heat exchanger and is cooled step by step. The heat exchanger is equipped with one or more heat medium channels and one or more cold medium channels. After the heat exchanger, the temperature of the gas is reduced to -30~-130°C, and then enters the low-temperature gas-liquid separator for gas-liquid separation. The obtained liquid propylene is decompressed by the liquid expansion device, and then returns to the high-efficiency multi-channel heat exchanger for exchange. The propylene evaporated into the gas phase after cooling is the gas from the low-temperature gas-liquid separator, which is mainly composed of nitrogen, and returns to the high-efficiency multi-channel heat exchanger, and is recovered after reheating to recover the cooling capacity.

Further, in the above technical solution, the nitrogen gas after reheating and recovering cooling capacity enters the expansion device for expansion and refrigeration, and the expanded low-temperature gas returns to the high-efficiency multi-channel heat exchanger to provide cooling capacity for the entire system. After reheating, as recycled nitrogen, return to the polypropylene unit for reuse.

Further, in the above technical scheme, the recovered propylene can be sent directly or after pressurization to the ethylene plant, and then the propylene is refined into polymer-grade propylene; the gas phase propylene can also be liquefied by compression condensation to make a liquid propylene.

Beneficial effects of utility model

1) Through the method of expansion and refrigeration, the propylene in the polypropylene tail gas is liquefied, the propylene is recovered, and the nitrogen is purified at the same time to meet the requirements of nitrogen recycling;

2) Combining membrane separation technology to remove hydrogen from polypropylene tail gas;

3) Realize a recovery rate of more than 98% of propylene in the polypropylene tail gas, which is much higher than the recovery rate of propylene in the prior art, greatly reducing the unit consumption of the polypropylene plant;

4) Less equipment investment, low operating energy consumption, and small footprint.

Description of drawings

Fig. 1 is a system diagram of the utility model polypropylene tail gas recovery device and method;

In the figure, 100, compression unit; 110, tail gas compressor; 120, circulating water cooler; 130, normal temperature gas-liquid separator; 200, drying unit; 201, adsorption tower; 300, membrane separator unit; 310, membrane separation 400, cryogenic separation unit; 410, high-efficiency multi-channel heat exchanger; 420, low-temperature gas-liquid separator; 430, liquid expansion equipment; 440, gas expansion equipment; 10, pipeline a; 11, pipeline b; 12, pipeline c; 13, pipeline d; 14, pipeline e; 15, pipeline j; 16, pipeline h; 17, pipeline i; 18, pipeline j; 19, pipeline k; 20, Pipeline l; 21, pipeline m; 22, pipeline n; 23, pipeline o; 24, pipeline f; 29, pipeline p.

Detailed ways

Now in conjunction with accompanying drawing, the utility model is described in further detail.

As shown in accompanying drawing 1, a kind of polypropylene tail gas recovery device provided by the utility model comprises:

The compression unit 100 includes a tail gas compressor 110 , a circulating water cooler 120 and a normal temperature gas-liquid separator 130 . The tail gas in the polypropylene production process is connected to the inlet of the tail gas compressor 110 through the pipeline a10. The tail gas compressor 110 raises the pressure of the gas to 0.6-3.0 MPaA to meet the operating pressure requirements of expansion refrigeration, cryogenic separation and membrane separation. The compressed gas is connected to the circulating water cooler 120 through the pipeline b11, the compressed gas is cooled to normal temperature, and connected to the normal temperature gas-liquid separator 130 through the pipeline c12 for gas-liquid separation, and the condensate obtained at the bottom passes through The pipeline p29 sends out the device; the normal temperature airflow obtained at its top enters the drying unit 200 through the pipeline d13.

The drying unit 200 includes an adsorption tower 210 equipped with a dehydrating desiccant, and the number of the adsorption towers 201 is set to 2, 3 or 4 according to the size of the treated gas volume and the selected regeneration gas. After passing through the adsorption tower 210, the water dew point of the gas decreases to -30~-130°C, and then enters the membrane separator unit 300 through the pipeline e14.

The membrane separator unit 300 includes a membrane separator 310 equipped with a membrane module. When the airflow output from the drying unit passes through the membrane separator 310, the hydrogen gas preferentially permeates through the membrane, and a low-pressure hydrogen-rich airflow is obtained on the permeation side of the membrane. The pipeline f24 is discharged to the flare, and the hydrogen-depleted gas flow enters the cryogenic separation unit 400 through the pipeline g15.

The cryogenic separation unit 400 includes a high-efficiency multi-channel heat exchanger 410 , a low-temperature gas-liquid separator 420 , a gas expansion device 440 and a liquid expansion device 430 . The hydrogen-deficient gas output from the membrane separation unit 300 passes through the pipeline g15 and enters the high-efficiency multi-channel heat exchanger 410. The plate-fin heat exchanger is preferred in this utility model. After passing through the heat medium channel C-C, the temperature of the gas gradually drops to -30~ -130°C, enter the low-temperature gas-liquid separator 420 through the pipeline h16 for gas-liquid separation, and obtain recovered propylene at the bottom of the low-temperature gas-liquid separator 420. The liquid propylene is connected to the liquid expansion device 430 through the pipeline i17. The utility model The throttling expansion valve is preferred. The temperature and pressure of the liquid will decrease after throttling and expansion, and then return to the high-efficiency multi-channel heat exchanger 410 through the pipeline j18 to exchange heat with the heat medium to provide cooling capacity. After passing through the cold medium channel D-D , the recovered propylene stream is transported out of the device through the pipeline k19, and can be directly sent to the ethylene plant after being pressurized, and then the propylene is refined into polymer-grade propylene; the gas phase propylene can also be liquefied by compression condensation, Made into liquid propylene. The non-condensable gas at the top of the low-temperature gas-liquid separator 420, mainly nitrogen, returns to the high-efficiency multi-channel heat exchanger 410 through the pipeline 120, and exchanges heat with the heat medium to provide cooling capacity. After passing through the cold medium channel A-A, it passes through the tube The path m21 enters the gas expansion device 440 for expansion and refrigeration. In the utility model, the gas expansion device is preferably a turbo expander, and the low-temperature gas obtained after the turbo expansion returns to the high-efficiency multi-channel heat exchanger 410 through the pipeline n22. Exchange heat with the heat medium to provide cooling capacity. After passing through the cold medium channel B-B, the recovered nitrogen stream is obtained, sent to the device through the pipeline o23, and returned to the polypropylene device for reuse.

In a preferred embodiment of the present utility model, according to the pressure and gas volume of the gas, the gas expansion device 440 can use one or more than one turbo expander to operate in series or in parallel, thereby providing a cryogenic separation unit More cooling.

The utility model also provides a method for recovering propylene and nitrogen by using the polypropylene tail gas recovery device. The utility model will be further described in detail below in conjunction with the accompanying drawings and examples, so that those skilled in the art can understand more comprehensively This utility model, but does not limit the utility model in any way. Pressures stated herein are gauge pressures.

Example 1

In the schematic diagram of the technological process for recovering propylene and nitrogen from polypropylene tail gas shown in Figure 1, the pressure of polypropylene tail gas is 0.05MPa, the temperature is 50°C, the gas volume is ^1000Nm3 /hr, and the composition is as follows:

components H ₂ Acrylic propane Vinyl Hexane H ₂ O N ₂ Content%V/V 1.28 8.10 0.10 6.50 0.25 0.27 83.50

The tail gas first enters the compression unit 100, and the tail gas compressor 110 raises the pressure of the gas to 1.6MPa, and then enters the circulating water cooler 120 to cool the compressed gas to 40°C. The cooled gas enters the normal-temperature gas-liquid separator 130 for gas-liquid separation, and the condensate delivery device obtained at the bottom; the normal-temperature airflow obtained at the top enters the drying unit 200 . In the drying unit, the gas passes through the adsorption tower, and the adsorbent is a composite bed composed of activated alumina and molecular sieve, which reduces the H ₂ O content to below 1ppmv and prevents ice blockage in the subsequent cryogenic separation process. The dried gas enters the membrane separator unit 300. The membrane separator is equipped with a membrane module. The membrane material used is polyimide. After passing through the separation membrane, the permeate gas flow of the membrane is obtained. The pressure is 0.05MPa and the temperature is At 40°C, the gas volume is 33Nm ³ /hr, and the composition is as follows:

components H ₂ Acrylic propane Vinyl Hexane H ₂ O N ₂ Content%V/V 14.82 3.23 0.02 4.94 0.04 0.00 76.95

The permeate gas stream is discharged to the flare; the retentate side of the membrane separation is a hydrogen-depleted gas stream entering the cryogenic separation unit 400 .

The hydrogen-depleted gas flow first enters the plate-fin heat exchanger, and after passing through the heat medium channel CC, the temperature of the gas gradually drops to -120°C. At this time, more than 99% of the propylene has been liquefied, and then in the low-temperature gas-liquid separator 420, The gas-liquid separation is carried out, and the recovered propylene is obtained at the bottom of the low-temperature gas-liquid separator 420. The liquid propylene passes through the throttling expansion valve, and the temperature and pressure decrease after expansion, and then returns to the plate-fin heat exchanger for heat exchange with the heat medium. Provide cooling capacity and pass through the cold medium channel DD to obtain recovered propylene stream with a pressure of 0.25MPa, a temperature of 30°C, and a gas volume of 143Nm ³ /hr. The composition is as follows:

components H ₂ Acrylic propane Vinyl Hexane H ₂ O N ₂ Content%V/V 0.005 55.778 0.728 37.428 1.726 0.000 4.336

This stream is sent directly to an ethylene plant where the propylene is refined to polymer grade propylene.

The non-condensable gas at the top of the low-temperature gas-liquid separator 420, mainly nitrogen, returns to the plate-fin heat exchanger 410, exchanges heat with the heat medium, provides cooling capacity, and enters the turbo expander after passing through the cold medium channel AA. Expansion refrigeration is performed. In this embodiment, an expander is used for single-stage expansion. The low-temperature gas obtained after expansion by the turbine returns to the plate-fin heat exchanger to exchange heat with the heat medium to provide cooling capacity. After the medium channel BB, the recovered nitrogen stream is obtained, the pressure is 0.22MPa, the temperature is 20°C, the gas volume is 821Nm ³ /hr, and the composition is as follows:

components H ₂ Acrylic propane Vinyl Hexane H ₂ O N ₂ Content%V/V 0.96 0.04 0.00 1.21 0.00 0.00 97.79

According to the actual situation, all or part of it can be returned to the polypropylene plant for reuse.

Example 2

In the schematic diagram of the technological process for recovering propylene and nitrogen from polypropylene tail gas shown in Figure 1, the pressure of polypropylene tail gas is 0.02MPa, the temperature is 51°C, and the gas volume is 900Nm ³ /hr. The composition is as follows:

components H ₂ Acrylic propane Vinyl Hexane H ₂ O N ₂ Content%V/V 0.60 27.67 5.55 1.40 0.00 0.99 63.79

The tail gas first enters the compression unit 100, and the tail gas compressor 110 raises the pressure of the gas to 1.7MPa, and then enters the circulating water cooler 120 to cool the compressed gas to 40°C. The cooled gas enters the normal-temperature gas-liquid separator 130 for gas-liquid separation, and the condensate obtained at the bottom passes through the delivery device; the normal-temperature airflow obtained at the top enters the drying unit 200 . In the drying unit, the gas passes through the adsorption tower, and the adsorbent is a composite bed composed of activated alumina and molecular sieve, which reduces the H ₂ O content to below 1ppmv and prevents ice blockage in the subsequent cryogenic separation process. The dried gas enters the membrane separator unit 300. The membrane separator is equipped with a membrane module. The membrane material used is polyimide. After passing through the separation membrane, the permeate gas flow of the membrane is obtained. The pressure is 0.05MPa and the temperature is At 38°C, the gas volume is 38Nm ³ /hr, and the composition is as follows:

components H ₂ Acrylic propane Vinyl Hexane H ₂ O N ₂ Content%V/V 6.72 14.45 1.58 1.38 0.00 0.00 75.86

The permeate gas stream is discharged to the flare; the retentate side of the membrane separation is a hydrogen-depleted gas stream entering the cryogenic separation unit 400 .

The hydrogen-poor gas flow first enters the plate-fin heat exchanger, and after passing through the heat medium channel CC, the temperature of the gas gradually drops to -110°C. At this time, more than 99% of the propylene has been liquefied, and then in the low-temperature gas-liquid separator 420, The gas-liquid separation is carried out, and the recovered propylene is obtained at the bottom of the low-temperature gas-liquid separator 420. The liquid propylene passes through the throttling expansion valve, and the temperature and pressure decrease after expansion, and then returns to the plate-fin heat exchanger for heat exchange with the heat medium. Provide cooling capacity and pass through the cold medium channel DD to obtain recovered propylene stream with a pressure of 0.05MPa, a temperature of 25°C, and a gas volume of 314Nm ³ /hr. The composition is as follows:

components H ₂ Acrylic propane Vinyl Hexane H ₂ O N ₂ Content%V/V 0.00 77.27 15.66 3.50 0.00 0.00 3.57

This stream needs to be sent to the ethylene plant through further pressurization, and then the propylene is refined into polymer grade propylene.

The non-condensable gas at the top of the low-temperature gas-liquid separator 420, mainly nitrogen, returns to the plate-fin heat exchanger to exchange heat with the heat medium to provide cooling capacity. After passing through the cold medium channel AA, it enters the turbo expander for Expansion refrigeration, in this embodiment, two expanders are used in series to operate, and the low-temperature gas obtained after the expansion of the turbine returns to the plate-fin heat exchanger, exchanges heat with the heat medium, provides cooling capacity, and passes through the cold medium channel BB Finally, the recovered nitrogen stream is obtained, the pressure is 0.25MPa, the temperature is 15°C, the gas volume is 5381Nm ³ /hr, and the composition is as follows:

components H ₂ Acrylic propane Vinyl Hexane H ₂ O N ₂ Content%V/V 0.52 0.14 0.02 0.21 0.00 0.00 99.11

The nitrogen stream can be returned to the polypropylene unit for reuse in whole or in part according to the actual situation.

It can be seen from the examples provided by the utility model that the method of the utility model can better recover propylene and nitrogen in the tail gas of polypropylene, so that the recovery rate of propylene in the tail gas is greater than 98%, and the purity of nitrogen is more than 97.5%. In addition, the method of the utility model also converts pressure energy into low-temperature cooling capacity through a turbo expansion device, and has the advantages of high energy utilization rate, low investment cost, and easy operation.

The above is only a preferred embodiment of the utility model, but the scope of protection of the utility model is not limited thereto. The equivalent replacement or change of the new technical solution and the concept of the utility model shall be covered by the protection scope of the utility model.

Claims (6)

1. a polypropylene tail gas recovery device, is characterized in that:

Comprise the compression unit, drying unit, film separation unit and the cryogenic separation unit that connect successively;

Described compression unit, comprises at least one compressor connected successively, a heat exchanger and a gas-liquid separator;

Described drying unit, comprise at least two adsorption towers connected successively, described adsorption tower is built with drier;

Described film separation unit, comprises membrane separator;

Described cryogenic separation unit, comprises at least one efficient multi-channel heat exchanger, at least one low temperature gas-liquid separator, at least one gas expansion equipment and at least one expansion of liquids equipment; Described membrane separator outlet connects hot media channel C-C, the low temperature gas-liquid separator entrance of efficient multi-channel heat exchanger successively; Low temperature gas-liquid separator outlet at bottom is connecting fluid volume expansion equipment, the cold medium channel D-D of efficient multi-channel heat exchanger, pipeline k successively; Low temperature gas-liquid separator top exit connects cold medium channel A-A, the gas expansion equipment of efficient multi-channel heat exchanger successively, the cold medium channel B-B of efficient multi-channel heat exchanger, pipeline o.

2. polypropylene tail gas recovery device according to claim 1, it is characterized in that: in drying unit, described drier is selected from activated alumina, silica gel, molecular sieve.

3. polypropylene tail gas recovery device according to claim 1, is characterized in that: in film separation unit, is provided with Hydrogen Separation film in described membrane separator;

Described Hydrogen Separation film is selected from the one in the metal films such as polyimides, polysulfones, Nomex, acetate fiber, polyphenylene oxide, palladium film.

4. polypropylene tail gas recovery device according to claim 1, it is characterized in that: in cryogenic separation unit, described expansion of liquids equipment is selected from throttle expansion valve.

5. polypropylene tail gas recovery device according to claim 1, it is characterized in that: in cryogenic separation unit, described gas expansion equipment is selected from turbo-expander, air wave refrigerating device.

6. polypropylene tail gas recovery device according to claim 1, is characterized in that: in cryogenic separation unit, and described efficient multi-channel heat exchanger is selected from plate-fin heat exchanger or around heat exchange of heat pipe.