Waste heat utilization of mixed refrigerant compressor unit and circulating refrigeration device

Abstract

The present invention discloses a mixed refrigerant compressor unit waste heat utilization and circulating refrigeration device, including a high-temperature refrigerant cooling module, a heat recovery module, a raw gas cooling module and a high-pressure refrigerant cooling module; the high-temperature refrigerant cooling module is used to cool the mixed refrigerant through medium-temperature hot water and output a normal-temperature high-pressure refrigerant; the heat recovery module is used to recover heat and output chilled water and medium-temperature hot water; the raw gas cooling module is used to input raw gas and chilled water and heat exchange and cool the raw gas; the high-pressure refrigerant cooling module is used to heat exchange and cool the chilled water with a normal-temperature high-pressure gas phase refrigerant to obtain a refrigerated high-pressure refrigerant, and to balance the cold and output the liquefied natural gas. The present invention can effectively recover the high-grade part of the process gas waste heat through effective cold and heat conversion and matching, greatly reduce the compression power consumption of the liquefaction device and the adsorption regeneration energy consumption of the molecular sieve system, and improve the energy efficiency of the device.

Description

Technical Field

[0001] The invention belongs to the field of natural gas liquefaction and coke oven gas deep cold separation, and in particular relates to a mixed refrigerant compressor unit waste heat utilization and circulating refrigeration device. Background Art

[0002] In recent years, excessive coal consumption has led to increasingly serious environmental pollution. Using clean energy such as natural gas to gradually replace coal is one of the powerful measures to improve environmental quality. After entering 2017, driven by the national top-down "coal to gas" policy, domestic natural gas consumption has increased significantly, reaching 280.3 billion m in 2018. 3 LNG (liquefied natural gas) is an effective supplement to natural gas. During the production process, raw materials such as coke oven gas, coalbed methane, and natural gas need to be fully purified, circulated, refrigerated, and separated to produce LNG products.

[0003] In the LNG production process, the energy required for refrigeration and liquefaction accounts for almost 70% to 85% of the entire device. A large amount of waste heat is generated and discarded during the refrigerant compression process. This heat is discharged into the air and not only cannot generate effective value, but also requires additional energy (closed-loop water cooling or air cooling) for cooling. The higher the temperature of the gas entering the refrigerant compressor, the greater the power consumption of the refrigeration compressor, and the higher the temperature of the discharged gas, which will have a great impact on production. In actual production, circulating water cooling is mainly used, which not only consumes a large amount of circulating water and power, but also causes a large waste of waste heat energy and water resources and pollution to the environment. This is an important reason for the current low energy efficiency. Summary of the invention

[0004] The object of the present invention is to provide a mixed refrigerant compressor unit waste heat utilization and circulation refrigeration device to solve the problems of resource waste and serious energy loss in the LNG production process in the prior art.

[0005] In order to achieve the above tasks, the present invention adopts the following technical solutions:

[0006] A mixed refrigerant compressor unit waste heat utilization and circulation refrigeration device, comprising a high-temperature refrigerant cooling module, a heat recovery module, a raw gas cooling module and a high-pressure refrigerant cooling module;

[0007] The high-temperature refrigerant cooling module is used to cool the mixed refrigerant by medium-temperature hot water and output a normal-temperature high-pressure refrigerant. The high-temperature refrigerant cooling module also includes a gas-liquid separation unit, which is used to separate the normal-temperature high-pressure refrigerant output by the high-temperature refrigerant cooling module into a normal-temperature high-pressure liquid-phase refrigerant and a normal-temperature high-pressure gas-phase refrigerant. The mixed refrigerant includes the high-temperature high-pressure refrigerant compressed by the compressor and the low-pressure gas-phase refrigerant obtained by the high-pressure refrigerant cooling module;

[0008] The heat energy recovery module is used to recover the coldness of the chilled water after heat exchange in the raw gas cooling module, the coldness of the chilled water after heat exchange in the high-pressure refrigerant cooling module, and the heat of the high-temperature hot water after heat exchange in the high-temperature refrigerant cooling module, and outputs chilled water and medium-temperature hot water;

[0009] The raw gas cooling module is used to input the raw gas and exchange heat with the chilled water generated by the heat recovery module and cool the raw gas to obtain refrigerated raw gas;

[0010] The high-pressure refrigerant cooling module is used to exchange heat and cool the chilled water generated by the heat recovery module with the normal-temperature high-pressure gas-phase refrigerant obtained by the high-temperature refrigerant cooling module to obtain refrigerated high-pressure refrigerant, and to balance the cooling capacity of the refrigerated raw gas generated by the raw gas cooling module and the refrigerated high-pressure refrigerant, throttling to obtain low-pressure gas-phase refrigerant and liquefied natural gas, and outputting liquefied natural gas.

[0011] Furthermore, the high-temperature refrigerant cooling module includes a first mixed refrigerant compressor and a second mixed refrigerant compressor, the output end of the first mixed refrigerant compressor is connected to the first hot water heat exchanger and the first cooling water heat exchanger in sequence, the input end of the second mixed refrigerant compressor is connected to the first cooling water heat exchanger, and the output end of the second mixed refrigerant compressor is connected to the second hot water heat exchanger and the second cooling water heat exchanger in sequence.

[0012] Furthermore, the gas-liquid separation unit includes a first gas-liquid separator arranged between the first cooling water heat exchanger and the second mixed refrigerant compressor, and also includes a second gas-liquid separator arranged between the second cooling water heat exchanger and the high-pressure refrigerant cooling module.

[0013] Furthermore, the heat recovery module includes a lithium bromide refrigeration unit, a hot water circulation pump and a chilled water circulation pump, wherein the hot water circulation pump is arranged at the input end of the lithium bromide refrigeration unit, and the chilled water circulation pump is arranged at the output end of the lithium bromide refrigeration unit;

[0014] Furthermore, the raw gas cooling module includes a first cooler and a molecular sieve system connected in sequence, the input end of the first cooler is connected to the output end of the heat recovery module and the raw natural gas feed end, and the output end of the molecular sieve system is respectively connected to a chilled water circulation pump and a high-pressure refrigerant cooling module.

[0015] Furthermore, the high-pressure refrigerant cooling module includes a second cooler, an aluminum plate-fin heat exchanger and a feed gas heavy hydrocarbon separator;

[0016] The input end of the second cooler is respectively connected to the output end of the second gas-liquid separator and the lithium bromide refrigeration unit, and the output end of the second cooler is respectively connected to the chilled water circulation pump and the aluminum plate-fin heat exchanger;

[0017] The input end of the aluminum plate-fin heat exchanger is respectively connected to the second cooler, the molecular sieve system and the second gas-liquid separator, and the output end of the aluminum plate-fin heat exchanger is respectively connected to the raw gas heavy hydrocarbon separator, the first mixed refrigerant compressor and the liquefied natural gas output port.

[0018] Furthermore, the temperature-exchanging hot water includes two temperatures: hot water of 65 to 80° C. is used in the first hot water heat exchanger and the second hot water heat exchanger, and normal temperature cooling water of 32° C. is used in the first cooling water heat exchanger and the second cooling water heat exchanger.

[0019] Furthermore, the hot water connecting pipes between the modules and inside the modules are made of heat-insulating materials, and the connecting pipes for chilled water and low-temperature refrigerant are made of cold-insulating materials.

[0020] Compared with the prior art, the present invention has the following technical features:

[0021] (1) The present invention utilizes the waste heat of compression of the mixed refrigerant compressor unit through reasonable recovery and conversion for use in the existing natural gas liquefaction refrigeration field, which not only utilizes the waste heat and other energy of the mixed refrigerant compressor unit, but also saves the energy consumed by the mixed refrigerant cycle compression required for natural gas liquefaction refrigeration.

[0022] (2) The present invention exchanges the waste heat of the process gas of the compressor through two small pressure difference heat exchangers and then provides it to the hot water type absorption lithium bromide refrigeration unit. The endothermic chiller produces chilled water and then provides it to the high-pressure gas phase refrigerant heat exchanger and the raw gas molecular sieve dehydration pre-cooler for refrigeration. When the cooling capacity of the refrigerated refrigerant and the raw gas is balanced in the aluminum plate-fin heat exchanger, the driving power consumption of the mixed refrigerant compressor unit will be further reduced. On the one hand, the high-temperature process gas after compression of the compressor is cooled to avoid the need to consume a large amount of circulating cooling water for direct cooling of the high-temperature process gas. On the other hand, the energy of the absorbed high-temperature gas is used to drive the endothermic chiller. This method of combined cold and heat supply saves a lot of refrigeration power and saves industrial costs.

[0023] (3) The present invention cools the raw gas in the cooler before the raw gas molecular sieve is dehydrated, thereby reducing the water content of the raw gas entering the molecular sieve system, improving the adsorption effect of the molecular sieve system, and effectively reducing the regeneration energy consumption of the molecular sieve. In addition, the service life of the molecular sieve adsorbent of the device can be extended as a whole, the operating consumption of the device can be reduced, and the technical equipment level of the device can be further improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1It is a schematic diagram of the connection of each module of the present invention;

[0025] Figure 2 It is a schematic diagram of the device connection of the present invention.

[0026] The meaning of each number in the accompanying drawings: 101-mixed refrigerant compressor unit, 102-first hot water heat exchanger, 103-first cooling water heat exchanger, 104-first gas-liquid separator, 105-first hot water heat exchanger, 106-second cooling water heat exchanger, 107-second gas-liquid separator, 108-first cooler, 109-second cooler, 110-aluminum plate-fin heat exchanger, 111-raw gas heavy hydrocarbon separator, 112-lithium bromide refrigeration unit, 113-hot water circulation pump, 114-chilled water circulation pump; 101-1-first mixed refrigerant compressor, 101-2-second mixed refrigerant compressor.

[0027] The specific contents of the present invention are further explained in detail below in conjunction with the accompanying drawings and specific embodiments. DETAILED DESCRIPTION

[0028] The specific implementation methods of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent changes made on the basis of the technical solution of this application fall within the protection scope of the present invention.

[0029] A mixed refrigerant compressor unit waste heat utilization and circulation refrigeration device, comprising a high-temperature refrigerant cooling module, a heat recovery module, a raw gas cooling module and a high-pressure refrigerant cooling module;

[0030] The high-temperature refrigerant cooling module is used to cool the mixed refrigerant through medium-temperature hot water and output high-pressure refrigerant at room temperature. Its function is to cool the high-pressure and high-temperature refrigerant compressed by the compressor to room temperature for the next stage of compression or external transmission system, so as to improve the compression efficiency of the compression process.

[0031] The high-temperature refrigerant cooling module also includes a gas-liquid separation unit, which is used to separate the normal temperature and high pressure refrigerant output by the high-temperature refrigerant cooling module into normal temperature and high pressure liquid phase refrigerant and normal temperature and high pressure gas phase refrigerant. The mixed refrigerant includes the high temperature and high pressure refrigerant compressed by the compressor and the low pressure gas phase refrigerant obtained by the high pressure refrigerant cooling module in the aluminum plate-fin heat exchanger after refrigeration and throttling. The function of the gas-liquid separation unit is to separate the high boiling point condensate that may be carried in the normal temperature mixed refrigerant from the aluminum plate-fin heat exchanger or the high pressure mixed refrigerant compressed and cooled by the compressor, so as to achieve the purpose of protecting the compressor unit and the stable transportation of the pipeline system.

[0032] The heat recovery module is used to recover the coldness of the chilled water after heat exchange in the raw gas cooling module, the coldness of the chilled water after heat exchange in the high-pressure refrigerant cooling module, and the heat of the high-temperature hot water after heat exchange in the high-temperature refrigerant cooling module, and outputs chilled water and medium-temperature hot water;

[0033] Its function is to input the high-temperature hot water obtained by taking heat from the hot water heat exchanger between the high-temperature refrigerant and the medium-temperature hot water into the lithium bromide unit, so as to achieve the purpose of using waste heat energy to produce cold energy;

[0034] The raw gas cooling module is used to input the raw gas and exchange heat and cool the chilled water generated by the heat recovery module with the raw gas to obtain refrigerated raw gas;

[0035] Its function is to cool the chilled water produced by the system and the raw gas before the molecular sieve to remove the saturated water in the raw gas, reduce the water content of the raw gas entering the molecular sieve system, and achieve the purpose of reducing the dehydration load and regeneration load of the molecular sieve system;

[0036] The high-pressure refrigerant cooling module is used to exchange heat and cool the chilled water generated by the heat recovery module with the normal-temperature high-pressure gas-phase refrigerant obtained by the high-temperature refrigerant cooling module to obtain refrigerated high-pressure refrigerant, and to balance the cooling capacity of the refrigerated raw gas generated by the raw gas cooling module and the refrigerated high-pressure refrigerant, throttling to obtain low-pressure gas-phase refrigerant and liquefied natural gas, and outputting liquefied natural gas;

[0037] Its function is to exchange heat between the chilled water produced by the system and the normal temperature high-pressure gas phase refrigerant, so as to reduce the temperature of the high-pressure gas phase refrigerant and the cooling capacity required by the aluminum plate-fin heat exchanger to cool the raw gas.

[0038] Specifically, the high-temperature refrigerant cooling module includes a first mixed refrigerant compressor 101-1 and a second mixed refrigerant compressor 101-2. The output end of the first mixed refrigerant compressor 101-1 is connected to the first hot water heat exchanger 102 and the first cooling water heat exchanger 103 in sequence, the input end of the second mixed refrigerant compressor 101-2 is connected to the first cooling water heat exchanger 103, and the output end of the second mixed refrigerant compressor 101-2 is connected to the second hot water heat exchanger 105 and the second cooling water heat exchanger 106 in sequence.

[0039] Specifically, the gas-liquid separation unit includes a first gas-liquid separator 104 disposed between the first cooling water heat exchanger 103 and the second mixed refrigerant compressor 101 - 2 , and also includes a second gas-liquid separator 107 disposed between the second cooling water heat exchanger 106 and the high-pressure refrigerant cooling module.

[0040] Specifically, the heat recovery module includes a lithium bromide refrigeration unit 112, a hot water circulation pump 113 and a chilled water circulation pump 114, the hot water circulation pump 113 is arranged at the input end of the lithium bromide refrigeration unit 112, and the chilled water circulation pump 114 is arranged at the output end of the lithium bromide refrigeration unit 112;

[0041] Specifically, the raw gas cooling module includes a first cooler 109 and a molecular sieve system connected in sequence, the input end of the first cooler 109 is connected to the output end of the heat recovery module and the raw natural gas feed end, and the output end of the molecular sieve system is respectively connected to the chilled water circulation pump 114 and the high-pressure refrigerant cooling module.

[0042] Specifically, the high-pressure refrigerant cooling module includes a second cooler 108, an aluminum plate-fin heat exchanger 110, and a feed gas heavy hydrocarbon separator 111;

[0043] The input end of the second cooler 108 is connected to the output end of the second gas-liquid separator 107 and the lithium bromide refrigeration unit 112 respectively, and the output end of the second cooler 108 is connected to the chilled water circulation pump 114 and the aluminum plate-fin heat exchanger 110 respectively;

[0044] The input end of the aluminum plate-fin heat exchanger 110 is respectively connected to the second cooler 108, the molecular sieve system and the second gas-liquid separator 107, and the output end of the aluminum plate-fin heat exchanger 110 is respectively connected to the raw gas heavy hydrocarbon separator 111, the first mixed refrigerant compressor 101-1 and the liquefied natural gas output port.

[0045] Preferably, the warm water for warming includes two temperatures, 65-80°C hot water is used at the first hot water heat exchanger 102 and the second hot water heat exchanger 105, and 32°C normal temperature cooling water is used at the first cooling water heat exchanger 103 and the second cooling water heat exchanger 106. The warm water for warming is a hot water medium, and the replenishment water comes from normal temperature soft water. After the connected water pump boosts the pressure and the system heats up, it enters the small pressure difference heat exchanger of each compressor to exchange heat with the high temperature refrigerant gas, and the water with the increased temperature after the heat exchange is sent to the lithium bromide refrigeration unit through the pipeline and the control valve. The generated chilled water is connected to the dehydration cooler and the high pressure gas phase refrigerant heat exchanger before the molecular sieve system through the pipeline and the control valve. The high pressure gas phase refrigerant heat exchanger and the dehydration cooler of the molecular sieve system are small pressure difference heat exchangers, which provide cold capacity and then return to the lithium bromide unit for circulating refrigeration.

[0046] Specifically, the hot water connecting pipes between modules and inside the modules use thermal insulation materials, and the connecting pipes for chilled water and low-temperature refrigerant use cold insulation materials, so as to reduce the heat loss and cold loss of the system and improve the energy utilization efficiency.

[0047] Specifically, the aluminum plate-fin heat exchanger refrigeration system further cools and throttles the high-pressure gas-phase refrigerant and the high-pressure liquid-phase refrigerant itself, and provides the cooling capacity required for the liquefaction and cooling of the raw gas into LNG. The low-pressure mixed refrigerant that is reheated after providing the cooling capacity is mixed and recycled to the inlet of the mixed refrigerant compressor unit C301 for circulation.

[0048] The working process of the present invention is as follows: when the high-temperature refrigerant process gas of the compressor passes through the interstage cooling and the final stage cooling E-303, a small pressure difference heat exchanger and 65℃~80℃ hot water are first used for heat exchange and heat extraction, and the temperature of the process gas itself is reduced. Then, the process gas after heat extraction continues to be cooled by a conventional circulating cooling water heat exchanger. The hot water after heat extraction through the small pressure difference heat exchanger is heated to 75℃~90℃. After the high-temperature hot water is collected, it enters the hot water type absorption lithium bromide refrigeration unit to provide a heat source to prepare 7℃~15℃ chilled water. After the high-temperature hot water provides heat in the lithium bromide unit, the temperature is reduced to 65℃~80℃, and then it returns to the interstage and final stage small pressure difference heat exchangers of the compressor for continuous heat extraction in a cycle. The 7℃~15℃ chilled water prepared by the lithium bromide unit is sent to the high-pressure gas-phase refrigerant heat exchanger and the raw gas molecular sieve dehydration pre-cooler to cool the high-pressure gas-phase refrigerant and the raw gas. The cooled high-pressure gas-phase refrigerant and the raw gas enter the aluminum plate-fin heat exchanger through different flow channels. After the system cooling capacity is balanced, the low-pressure gas-phase refrigerant returns to the inlet of the mixed refrigerant compressor unit. When the cooling capacity of the cooled refrigerant and the raw gas is balanced in the aluminum plate-fin heat exchanger, the driving power consumption of the mixed refrigerant compressor unit will be greatly reduced.

[0049] The present invention reduces the temperature of the high-temperature refrigerant process gas discharged from the interstage and the last stage of the mixed refrigerant compressor to 40°C through a multi-stage heat exchange device, wherein the high-quality heat (≥75°C) in the high-temperature refrigerant process gas is recycled and utilized, and then the high-quality heat is converted into high-temperature hot water (75°C to 90°C) for chilled water production. After the high-temperature hot water provides heat, it becomes medium-temperature hot water (65°C to 80°C) and is then sent to the hot water pump and the heat exchanger for circulation and heating. The entire hot water circulation system pipeline is insulated with thermal insulation materials to reduce system heat loss and improve thermal energy utilization efficiency. In this way, the waste heat of the high-temperature gas discharged from the mixed refrigerant compressor is recycled, and the use of circulating hot water also saves the use of circulating cooling water, reduces the power consumption and processing volume of the circulating cooling water of the entire device, and saves a large amount of circulating water and power resources.

[0050] Example

[0051] Take the 1 million cubic meters / day LNG liquefaction unit of a certain LNG liquefaction plant as an example:

[0052] Serial number Equipment Project Quantity (unit) Total power (kW) 1 Raw material gas compressor unit 1 2000 2 Original mixed refrigerant compressor unit 1 13500 3 Original dehydration molecular sieve heater 1 600 4 New lithium bromide unit 1 10 5 Added hot water circulation pump 2 45 6 New chilled water circulation pump 2 70

[0053] Aspen software is used to perform numerical simulation and heat exchanger selection calculation on the thermal data of high-temperature process gas waste heat of mixed refrigerant compressor unit, such as Figure 1 As shown, the total amount of waste heat that can be utilized after the system is balanced, as well as the specific parameters of each module, are obtained through analysis and calculation.

[0054] The 1 million cubic meters / day LNG liquefaction unit can save 625 to 850kw of energy overall on the basis of current operation. Among them, a small pressure difference heat exchanger is used to extract waste heat from the compressor unit cooler through medium-temperature hot water to produce high-temperature hot water. After the high-temperature hot water is used to produce chilled water through the lithium bromide unit, the cold is transferred to the high-pressure gas phase refrigerant and raw gas through different coolers. After the cold balance is performed through the aluminum plate-fin heat exchanger, the power consumption of the mixed refrigerant compressor unit can be effectively reduced by about 650 to 900kw; the new equipment will increase the power consumption of the circulating water pump and other equipment by about 125kw; after the low-temperature waste heat is used for the dehydration of the raw gas before the molecular sieve, the adsorption effect of the molecular sieve system can be greatly improved, and the regeneration energy consumption of the molecular sieve can be effectively reduced by 15 to 20%, about 110kw.

[0055] After the implementation of the present invention, after improving the adsorption effect of the molecular sieve system, the service life of the molecular sieve adsorbent of the device can be extended on the basis of the current operation, the operating consumption of the device can be reduced, and the technical equipment level of the device can be further improved.

Claims

1. A mixed refrigerant compressor unit waste heat utilization and circulating refrigeration device, characterized in that: It includes a high-temperature refrigerant cooling module, a heat recovery module, a raw gas cooling module and a high-pressure refrigerant cooling module; The high-temperature refrigerant cooling module is used to cool the mixed refrigerant by medium-temperature hot water and output a normal-temperature high-pressure refrigerant. The high-temperature refrigerant cooling module also includes a gas-liquid separation unit, which is used to separate the normal-temperature high-pressure refrigerant output by the high-temperature refrigerant cooling module into a normal-temperature high-pressure liquid-phase refrigerant and a normal-temperature high-pressure gas-phase refrigerant. The mixed refrigerant includes the high-temperature high-pressure refrigerant compressed by the compressor and the low-pressure gas-phase refrigerant obtained by the high-pressure refrigerant cooling module through refrigeration throttling in the aluminum plate-fin heat exchanger; The heat energy recovery module is used to recover the coldness of the chilled water after heat exchange in the raw gas cooling module, the coldness of the chilled water after heat exchange in the high-pressure refrigerant cooling module, and the heat of the high-temperature hot water after heat exchange in the high-temperature refrigerant cooling module, and outputs chilled water and medium-temperature hot water; The raw gas cooling module is used to input the raw gas and exchange heat with the chilled water generated by the heat recovery module and cool the raw gas to obtain refrigerated raw gas; The high-pressure refrigerant cooling module is used to exchange heat and cool the chilled water generated by the heat recovery module with the normal-temperature high-pressure gas-phase refrigerant obtained by the high-temperature refrigerant cooling module to obtain refrigerated high-pressure refrigerant, and to balance the refrigerated raw gas generated by the raw gas cooling module with the refrigerated high-pressure refrigerant, throttling to obtain low-pressure gas-phase refrigerant and liquefied natural gas, and outputting liquefied natural gas; The high-temperature refrigerant cooling module comprises a first mixed refrigerant compressor (101-1) and a second mixed refrigerant compressor (101-2), the output end of the first mixed refrigerant compressor (101-1) being connected in sequence to a first hot water heat exchanger (102) and a first cooling water heat exchanger (103), the input end of the second mixed refrigerant compressor (101-2) being connected to the first cooling water heat exchanger (103), and the output end of the second mixed refrigerant compressor (101-2) being connected in sequence to a second hot water heat exchanger (105) and a second cooling water heat exchanger (106); The gas-liquid separation unit comprises a first gas-liquid separator (104) arranged between the first cooling water heat exchanger (103) and the second mixed refrigerant compressor (101-2), and also comprises a second gas-liquid separator (107) arranged between the second cooling water heat exchanger (106) and the high-pressure refrigerant cooling module; The heat energy recovery module comprises a lithium bromide refrigeration unit (112), a hot water circulation pump (113) and a chilled water circulation pump (114); the hot water circulation pump (113) is arranged at the input end of the lithium bromide refrigeration unit (112), and the chilled water circulation pump (114) is arranged at the output end of the lithium bromide refrigeration unit (112); The raw gas cooling module comprises a first cooler (109) and a molecular sieve system connected in sequence, the input end of the first cooler (109) being connected to the output end of the heat recovery module and the raw natural gas feed end, and the output end of the molecular sieve system being connected to a chilled water circulation pump (114) and a high-pressure refrigerant cooling module respectively; The high-pressure refrigerant cooling module comprises a second cooler (108), an aluminum plate-fin heat exchanger (110) and a feed gas heavy hydrocarbon separator (111); The input end of the second cooler (108) is respectively connected to the output end of the second gas-liquid separator (107) and the lithium bromide refrigeration unit (112), and the output end of the second cooler (108) is respectively connected to the chilled water circulation pump (114) and the aluminum plate-fin heat exchanger (110); The input end of the aluminum plate-fin heat exchanger (110) is respectively connected to the second cooler (108), the molecular sieve system and the second gas-liquid separator (107), and the output end of the aluminum plate-fin heat exchanger (110) is respectively connected to the raw gas heavy hydrocarbon separator (111), the first mixed refrigerant compressor (101-1) and the liquefied natural gas output port; Hot water at 65-80° C. is used in the first hot water heat exchanger (102) and the second hot water heat exchanger (105), and normal temperature cooling water at 32° C. is used in the first cooling water heat exchanger (103) and the second cooling water heat exchanger (106).

2. The mixed refrigerant compressor unit waste heat utilization and circulating refrigeration device according to claim 1, characterized in that: The hot water connecting pipes between each module and inside the module are made of thermal insulation materials, and the connecting pipes of chilled water and low-temperature refrigerant are made of cold insulation materials.

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