A method and apparatus for the production of liquid air

Abstract

The present application relates to a kind of production method and device of liquid air, and the device includes raw material air compression system, air cooling drying system, circulating pressurization system, expansion refrigeration system, heat exchange cold box and liquid air storage tank.The production method realizes the efficient production of liquid air by multiple compression, cooling, drying, pressurization and expansion refrigeration etc.Steps, by optimizing energy utilization, recovering low-temperature air cooling capacity, saving compression work and power consumption, significantly reducing production cost.The present application is suitable for energy storage, metal smelting and precision manufacturing etc.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of air liquefaction, and relates to a production method and device of liquid air. BACKGROUND

[0002] Liquid air is a liquid form of air, referred to as liquid air. Because it is a multi-component mixture, the boiling points are different, and there is a characteristic of unstable purity. In the air separation field, it only exists as an intermediate product in the process, and has not been widely used. With the rapid development of China, the in-depth research and exploration of liquid air energy storage and compressed air energy storage, liquid air has become an ideal energy storage carrier due to its low temperature and large vaporization expansion coefficient, mature transportation and storage technology, and increasing application scenarios.

[0003] The inherent oxygen content characteristics of liquid air also have application scenarios for improving the efficiency of metal smelting and oxygen-enriched combustion. The drying and cleaning characteristics of liquid air also increase the application scenarios in precision manufacturing and dust-free workshops. The vaporization heat absorption potential of liquid air and the mechanical work generated by expansion contain energy. Coupling the use of liquid air with an air separation device can recover the cold energy of liquid air to replace expansion refrigeration, save the compression work of part of the expanded air that is not involved in rectification, and increase the raw air required for separation by the entry of liquid air, thereby saving part of the raw air compression power. Therefore, with the increasing application scenarios of liquid air, it is increasingly important to manufacture low-cost liquid air. SUMMARY

[0004] In view of the above problems, the present application provides a production method and device of liquid air.

[0005] To achieve the above-mentioned purpose, the present application provides the following technical scheme:

[0006] A production device of liquid air, comprising a raw air compression system, an air cooling and drying system, a circulating booster system, an expansion refrigeration system, a heat exchange cold box, and a liquid air storage tank.

[0007] The raw air compression system comprises an air feeding compressor and an air cooler; the air cooling and drying system comprises a cold dryer and an adsorption dryer; and the circulating booster system comprises a circulating booster and a booster cooler.

[0008] The expansion refrigeration system comprises a hot-end booster turbine expander, a hot-end booster cooler, a cold-end booster turbine expander, and a cold-end booster cooler; the cold-end booster turbine expander is provided with two groups of inlets and outlets, which are a cold-end booster air inlet and a cold-end booster air outlet, a cold-end expansion air inlet and a cold-end expansion air outlet; and the hot-end booster turbine expander is provided with two groups of inlets and outlets, which are a hot-end booster air inlet and a hot-end booster air outlet, a hot-end expansion air inlet and a hot-end expansion air outlet.

[0009] The heat exchange cold box comprises a hot-end heat exchanger, a cold-end heat exchanger and a supercooler; four groups of inlets and outlets are arranged on the hot-end heat exchanger, which are a hot-end heat exchange first inlet and a hot-end heat exchange first outlet, a hot-end heat exchange second inlet and a hot-end heat exchange second outlet, a hot-end heat exchange third inlet and a hot-end heat exchange third outlet and a hot-end heat exchange fourth inlet and a hot-end heat exchange fourth outlet; three groups of inlets and outlets are arranged on the cold-end heat exchanger, which are a cold-end heat exchange first inlet and a cold-end heat exchange first outlet, a cold-end heat exchange second inlet and a cold-end heat exchange second outlet and a cold-end heat exchange third inlet and a cold-end heat exchange third outlet; a side-end outlet is further led out at a middle position between the cold-end heat exchange first inlet and the cold-end heat exchange first outlet; two groups of inlets and outlets are arranged on the supercooler, which are a supercooling first inlet and a supercooling first outlet and a supercooling second inlet and a supercooling second outlet.

[0010] The air compression machine, the air cooler, the cold drying machine, the adsorption dryer, the circulating booster and the booster cooler are sequentially connected in series, and the outlet of the booster cooler is divided into two paths:

[0011] One path is communicated with the cold-end booster air inlet, the cold-end booster air outlet is communicated with the hot-end booster air inlet after passing through the cold-end booster cooler, the hot-end booster air outlet is communicated with the hot-end heat exchange first inlet after passing through the hot-end booster cooler, the hot-end heat exchange first outlet is communicated with the hot-end expansion air inlet, the hot-end expansion air outlet is communicated with the hot-end heat exchange third inlet, and the hot-end heat exchange third outlet is communicated with the inlet of the circulating booster;

[0012] The other path is communicated with the hot-end heat exchange second inlet, the hot-end heat exchange second outlet is communicated with the cold-end heat exchange first inlet, the cold-end heat exchange first outlet is communicated with the supercooling first inlet, the supercooling first outlet is divided into two paths, one path is communicated with the liquid air storage tank, and the other path is communicated with the cold-end second inlet, the supercooling second outlet is communicated with the cold-end heat exchange third inlet, the cold-end heat exchange third outlet is communicated with the hot-end heat exchange fourth inlet, and the hot-end heat exchange fourth outlet is communicated with the adsorption dryer to provide desorption gas for the adsorption dryer.

[0013] The side-end outlet is communicated with the cold-end expansion air inlet, the cold-end expansion air outlet is communicated with the cold-end heat exchange second inlet, and the cold-end heat exchange second outlet is communicated with the hot-end heat exchange third inlet.

[0014] Further, throttling valves are arranged between the cold-end heat exchange first outlet and the supercooling first inlet, between the supercooling first outlet and the liquid air storage tank and between the supercooling first outlet and the cold-end second inlet.

[0015] Further, a storage tank vapor outlet is arranged on the liquid air storage tank, and the liquid air vapor outlet is communicated with the cold-end heat exchange third inlet.

[0016] Further, the circulating booster is a piston booster.

[0017] Further, the hot end heat exchanger, the cold end heat exchanger and the supercooler are all aluminum alloy plate-fin heat exchangers and are arranged in three sections in series in the heat exchange cold box.

[0018] A liquid air production method using the above liquid air production device to produce liquid air;

[0019] The air is pressurized by the air feeding compressor to obtain medium pressure air, which enters the air cooler; the cooled medium pressure air is further cooled by the cold dryer, and then the water and carbon dioxide are removed by the adsorption dryer; the dry and clean medium pressure air enters the circulating booster to obtain high pressure air, which is then divided into two paths:

[0020] One path enters the cold end booster air inlet, is pressurized, cooled by the cold end booster cooler, enters the hot end booster air inlet, is pressurized again, is led out from the hot end booster air outlet, is cooled by the hot end booster cooler, enters the hot end heat exchange first inlet, is cooled, is led out from the hot end heat exchange first outlet, enters the hot end expansion air inlet, is expanded and refrigerated, is led out from the hot end expansion air outlet, and the expanded medium pressure air returns to the hot end heat exchange third inlet;

[0021] The other path directly enters the hot end heat exchange second inlet, is cooled, is led out from the hot end heat exchange second outlet, enters the cold end heat exchange first inlet, is cooled, and is divided into two paths in the middle of the cold end heat exchanger:

[0022] One path is led out from the side end outlet, is connected to the cold end expansion air inlet, is expanded and refrigerated, is led out from the cold end expansion air outlet, enters the cold end heat exchange second inlet, is reheated by the cold end heat exchanger, is led out from the cold end heat exchange second outlet, is combined with the medium pressure air led out from the hot end expansion air outlet, is reheated to normal temperature by the hot end heat exchanger, and returns to the circulating booster inlet;

[0023] The other path is cooled and liquefied high pressure liquid air led out from the cold end heat exchange first outlet, enters the supercooling first inlet after throttling, is supercooled, is led out from the supercooling first outlet, is divided into two parts, one part is returned to the supercooling second inlet after throttling to normal pressure, is vaporized and reheated, is led out from the supercooling second outlet, enters the cold end heat exchange third inlet, is reheated, is led out from the cold end heat exchange third outlet, enters the hot end heat exchange fourth inlet, is further reheated to normal temperature, is led out from the hot end heat exchange fourth outlet to the adsorption dryer, is analyzed, and is discharged to the atmosphere; the other part is sent to the liquid air storage tank as liquid air products.

[0024] Further, the high pressure air pressurized by the circulating booster has a pressure of 2.8-3.2 MPa, and is further pressurized by the cold end expansion booster and the hot end expansion booster to a pressure of 4.5-4.9 MPa.

[0025] Further, the vapor of the liquid air storage tank is combined with the supercooler after the normal pressure air to be used as the desorption gas of the adsorption dryer.

[0026] Further, the circulating booster is started with variable steps to reduce the impact on the power grid.

[0027] Further, the liquid air production device is operated in the low electricity price period and is stopped in the high electricity price period.

[0028] The beneficial effects of the present application are:

[0029] 1. The present application adopts the combination of multi-stage compression, expansion refrigeration and high-efficiency heat exchanger, uses the booster turbine expander to extract cold energy, effectively matches the booster amount and the expansion amount, improves the expansion refrigeration efficiency, and divides the heat exchange part into three sections, including the hot end heat exchanger, the cold end heat exchanger and the supercooler, optimizes the temperature before the expander and the temperature after the expander, optimizes the energy utilization efficiency in the air liquefaction process, significantly improves the production efficiency of liquid air, and reduces the production cost of liquid air.

[0030] 2. The present application produces liquid air in the low electricity price period, and has the effect of regulating the power grid.

[0031] 3. The present application uses supercooled gas and natural evaporation gas as the desorption gas of the adsorption dryer, and saves the compression cost of raw material gas.

[0032] 4. The present application does not set a flash evaporator for gas-liquid separation after the air is liquefied by the cold end heat exchanger, so as to maintain the stability of the liquid air composition.

[0033] Other advantages, objects, and features of the present application will be in part apparent and in part pointed out hereinafter. The objects and other advantages of the present application can be achieved and obtained by means of the following description. BRIEF DESCRIPTION OF DRAWINGS

[0034] In order to make the purposes, technical solutions and advantages of the present application clearer, the preferred detailed description of the present application will be combined with the drawings as follows, wherein:

[0035] Figure 1 The schematic diagram of the liquid air production device in the present application.

[0036] Reference: 1 - Gaseous air compressor; 2 - Air cooler; 3 - Cold dryer; 4 - Adsorption dryer; 5 - Circulating booster; 6 - Booster cooler; 7 - Cold end booster turbo expander; 8 - Cold end booster cooler; 9 - Hot end booster turbo expander; 10 - Hot end booster cooler; 11 - Hot end heat exchanger; 12 - Cold end heat exchanger; 13 - Subcooler; 14 - Liquid air storage tank; 21 - Air inlet; 22 - Air outlet; 23 - Cooling water inlet; 24 - Cooling water outlet; 41 - Adsorber air inlet; 42 - Adsorber air outlet; 43 - Adsorber purge gas inlet; 44 - Adsorber purge gas outlet; 61 - Circulating booster air inlet; 62 - Circulating booster air outlet; 63 - Cooling water inlet; 64 - Cooling water outlet; 71 - Cold end booster air inlet; 72 - Cold end booster air outlet; 73 - Cold end expanded air inlet; 74 - Cold end expanded air outlet; 81 - Cold end cooling air inlet; 82 - Cold end cooling air outlet; 83 - Cooling water inlet; 84 - Cooling water outlet; 91 - Hot end booster air inlet; 92 - Hot end booster air outlet; 93 - Hot end expanded air inlet; 94 - Hot end expanded air outlet; 101 - Hot end cooling air inlet; 102 - Hot end cooling air outlet; 103 - Cooling water inlet; 104 - Cooling water outlet; 111 - Hot end heat exchanger first inlet; 112 - Hot end heat exchanger first outlet; 113 - Hot end heat exchanger second inlet; 114 - Hot end heat exchanger second outlet; 115 - Hot end heat exchanger third outlet; 116 - Hot end heat exchanger third inlet; 117 - Hot end heat exchanger fourth outlet; 118 - Hot end heat exchanger fourth inlet; 120 - Cold end heat exchanger first outlet; 121 - Cold end heat exchanger first inlet; 122 - Side end outlet; 123 - Cold end heat exchanger second outlet; 124 - Cold end heat exchanger second inlet; 125 - Cold end heat exchanger third outlet; 126 - Cold end heat exchanger third inlet; 131 - Subcooler first inlet; 132 - Subcooler first outlet; 133 - Subcooler second outlet; 134 - Subcooler second inlet; 141 - Storage tank inlet; 142 - Storage tank vapor outlet; 53 - Storage tank liquid air outlet. DETAILED DESCRIPTION

[0037] The present application is herein described, by way of example only, with reference to certain embodiments thereof. It is readily apparent to one of ordinary skill in the art that varying implementations of the present application can be realized while still maintaining the spirit of the present application. Accordingly, it is not intended that the scope of the application be limited to the described embodiments herein but rather that it is intended the scope of the application be defined by the claims and equivalents thereof. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description, serve to explain the principles of the application.

[0038] The drawings are only used for exemplary illustration, and the representation is only a schematic diagram, not a physical diagram, and cannot be understood as a limitation on the present application; in order to better illustrate the embodiments of the present application, some components of the drawings are omitted, enlarged or reduced, and do not represent the size of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings can be omitted.

[0039] The same or similar reference numerals in the drawings of the embodiments of the present application correspond to the same or similar components; in the description of the present application, it is understood that if the terms "upper", "lower", "left", "right", "front", "back" and the like indicate the orientation or positional relationship shown in the drawings, only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore the positional relationship described in the drawings is only used for exemplary illustration, and cannot be understood as a limitation on the present application, for those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0040] Please refer to Figure 1 It is a kind of liquid air production device, including raw material air compression system, air cooling and drying system, circulating booster system, expansion refrigeration system, heat exchange cold box, liquid air storage tank 14;

[0041] The raw material air compression system includes air compressor 1, air cooler 2;Air cooling and drying system includes cold dryer 3, adsorption dryer 4;Circulating booster system includes circulating booster 5, booster cooler 6;Air cooler 2 is provided with two groups of inlet and outlet, respectively air inlet 21, air outlet 22, cooling water inlet 23, cooling water outlet 24;Adsorption dryer 4 is provided with two groups of inlet and outlet, respectively adsorption dryer air inlet 41, adsorption dryer air outlet 42, adsorption dryer desorption gas inlet 43, adsorption dryer desorption gas outlet 44.Booster cooler 6 is provided with circulating booster air inlet 61, circulating booster air outlet 62, cooling water inlet 63, cooling water outlet 64.

[0042] The expansion refrigeration system comprises a hot-end pressurized turbo-expander 9, a hot-end pressurized cooler 10, a cold-end pressurized turbo-expander 7, and a cold-end pressurized cooler 8. The cold-end pressurized turbo-expander 7 is provided with two groups of inlets and outlets, namely a cold-end pressurized air inlet 71 and a cold-end pressurized air outlet 72, a cold-end expansion air inlet 73 and a cold-end expansion air outlet 74. The hot-end pressurized turbo-expander 9 is provided with two groups of inlets and outlets, namely a hot-end pressurized air inlet 91 and a hot-end pressurized air outlet 92, a hot-end expansion air inlet 93 and a hot-end expansion air outlet 94. The hot-end pressurized cooler 10 is provided with two groups of inlets and outlets, namely a hot-end cooling air inlet 101, a hot-end cooling air outlet 102, a cooling water inlet 103 and a cooling water outlet 104. The cold-end pressurized cooler 8 is provided with two groups of inlets and outlets, namely a cold-end cooling air inlet 81, a cold-end cooling air outlet 82, a cooling water inlet 83 and a cooling water outlet 84.

[0043] The heat exchange cold box comprises a hot-end heat exchanger 11, a cold-end heat exchanger 12 and a supercooler 13. The hot-end heat exchanger 11 is provided with four groups of inlets and outlets, namely a hot-end heat exchange first inlet 111 and a hot-end heat exchange first outlet 112, a hot-end heat exchange second inlet 113 and a hot-end heat exchange second outlet 114, a hot-end heat exchange third inlet 116 and a hot-end heat exchange third outlet 115, and a hot-end heat exchange fourth inlet 118 and a hot-end heat exchange fourth outlet 117. The cold-end heat exchanger 12 is provided with three groups of inlets and outlets, namely a cold-end heat exchange first inlet 121 and a cold-end heat exchange first outlet 120, a cold-end heat exchange second inlet 124 and a cold-end heat exchange second outlet 123, and a cold-end heat exchange third inlet 126 and a cold-end heat exchange third outlet 125. The cold-end heat exchange first inlet 121 and the cold-end heat exchange first outlet 120 are further provided with a side-end outlet 122. The supercooler 13 is provided with two groups of inlets and outlets, namely a supercooling first inlet 131 and a supercooling first outlet 132, and a supercooling second inlet 134 and a supercooling second outlet 133. The liquid air storage tank 14 is provided with a storage tank inlet 141, a storage tank vapor outlet 142 and a storage tank liquid air outlet 53.

[0044] The air compression machine 1, the air cooler 2, the cold dryer 3, the adsorption dryer 4, the circulating pressurizer 5 and the pressurized cooler 6 are sequentially connected in series. The outlet of the pressurized cooler 6 is divided into two paths.

[0045] One path is communicated with the cold-end pressurized air inlet. The cold-end pressurized air outlet 72 is communicated with the hot-end pressurized air inlet 91 after passing through the cold-end pressurized cooler 8. The hot-end pressurized air outlet 92 is communicated with the hot-end heat exchange first inlet 111 after passing through the hot-end pressurized cooler 10. The hot-end heat exchange first outlet 112 is communicated with the hot-end expansion air inlet 93. The hot-end expansion air outlet 94 is communicated with the hot-end heat exchange third inlet 116. The hot-end heat exchange third outlet 115 is communicated with the inlet of the circulating pressurizer 5.

[0046] Another road with the hot end heat exchange second inlet 113 communication, the hot end heat exchange second outlet 114 and the cold end heat exchange first inlet 121 communication, the cold end heat exchange first outlet 120 and the supercooling first inlet 131 communication, the supercooling first outlet 132 is divided into two roads, one road communicates the storage tank inlet, another road passes through the supercooling second inlet 134, the supercooling second outlet 133 and the cold end heat exchange third inlet 126 communication;The cold end heat exchange third outlet 125 and the hot end heat exchange fourth inlet 118 communication;The hot end heat exchange fourth outlet 117 and the adsorption dryer 4 communication, provides the desorption gas to the adsorption dryer 4;

[0047] The side end outlet 122 and the cold end expansion air inlet 73 communication, the cold end expansion air outlet 74 and the cold end heat exchange second inlet 124 communication, the cold end heat exchange second outlet 123 and the hot end heat exchange third inlet 116 communication.

[0048] The supercooling first outlet 132 and the supercooling second inlet 134 between the throttle valve V1 is arranged, the supercooling first outlet 132 and the liquid air storage tank between the throttle valve V2 is arranged, the cold end heat exchange first outlet 120 and the supercooling first inlet 131 between the throttle valve V3 is arranged.

[0049] The liquid air storage tank 14 is provided with the storage tank vapor outlet 142, and the liquid air vapor outlet is communicated with the cold end heat exchange third inlet 126.

[0050] Wherein, the air compressor 1 adopts screw compressor, and the circulating booster 5 is piston booster to adapt to frequent start-stop.

[0051] The hot end heat exchanger 11, the cold end heat exchanger 12 and the supercooler 13 all adopt aluminum alloy plate fin heat exchanger, and are arranged in the heat exchange cold box in three sections in series.

[0052] A kind of liquid air production method, using the above liquid air production device to carry out liquid air production;

[0053] Air is pressurized to 0.5MPa by air compressor 1 to obtain medium-pressure air, and enters air cooler 2;The medium-pressure air after cooling is further cooled to 10 DEG C by cold dryer 3, and then removes moisture and carbon dioxide by adsorption dryer 4;Dry and clean medium-pressure air enters circulating booster 5 to obtain 2.9MPa high-pressure air, and then is divided into two roads:

[0054] One way into the cold end of the boost air inlet 71, after the boost through the cold end of the booster cooler 8 cooling after entering the hot end of the boost air inlet 91, again to 4.6MPa after the boost from the hot end of the boost air outlet 92, through the hot end of the cooling cooler 10 cooling after entering the hot end of the first heat exchange inlet 111, cooling from the hot end of the first heat exchange outlet 112, into the hot end of the expansion air inlet 93, after the expansion refrigeration from the hot end of the expansion air outlet 94, the expansion of the medium pressure air return to the third heat exchange inlet 116;

[0055] Another way directly into the hot end of the second heat exchange inlet 113, cooling from the hot end of the second heat exchange outlet 114, into the cold end of the first heat exchange inlet 121, cooling in the middle of the cold end of the heat exchanger 12, again into two ways:

[0056] One way from the side of the outlet 122, into the cold end of the expansion air inlet 73, after the expansion refrigeration of the medium pressure air from the cold end of the expansion air outlet 74, into the cold end of the second heat exchange inlet 124, after the reheating of the cold end of the heat exchanger 12 from the cold end of the second heat exchange outlet 123, and the medium pressure air from the hot end of the expansion air outlet 94, after the reheating of the hot end of the heat exchanger 11 to normal temperature, return to the inlet of the circulating supercharger 5;

[0057] Another way of the high pressure liquid air cooled after the cold end of the first heat exchange outlet 120, throttling to 0.55MPa after the throttling valve V3 into the supercooling first inlet 131, after the supercooling from the supercooling first outlet 132, the supercooled liquid air is divided into two parts, one part is throttled to 0.03MPa after the throttling valve V1, return to the supercooling second inlet 134, after the vaporization and reheating from the supercooling second outlet 133, into the cold end of the third heat exchange inlet 126, after the reheating from the cold end of the third heat exchange outlet 125, into the hot end of the fourth heat exchange inlet 118, continue to heat to normal temperature from the hot end of the fourth heat exchange outlet 117 to the adsorption dryer 4, after the analysis to the atmosphere discharge; another part as liquid air product to the liquid air tank.

[0058] In this embodiment, the circulating supercharger 5 uses variable step starting, which reduces the impact on the power grid. The liquid air production device is operated in the low electricity price period and stopped in the high electricity price period.

[0059] The raw material air used in this embodiment is 7500Nm 3 / h, 0.098MPa. The product liquid air obtained is 5000Nm 3 / h (equivalent to gaseous state).

[0060] Finally, it is to be explained that the above embodiments are only used to illustrate the technical solutions of the present application but not to limit the present application. Although the present application is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present application can be modified or equivalently replaced without departing from the purpose and scope of the technical solutions, and all should be covered in the scope of the claims of the present application.

Claims

1. A liquid air production apparatus, characterized in that: It includes a raw material air compression system, an air cooling and drying system, a circulating pressurization system, an expansion refrigeration system, a heat exchange cold box, and a liquid air storage tank; The raw material air compression system includes a feed air compressor and an air cooler; the air cooling and drying system includes a refrigerated dryer and an adsorption dryer; the circulating pressurization system includes a circulating pressurizer and a pressurization cooler. The expansion and refrigeration system includes a hot-end pressurized turbine expander, a hot-end pressurized cooler, a cold-end pressurized turbine expander, and a cold-end pressurized cooler. The cold-end pressurized turbine expander has two sets of inlets and outlets: a cold-end pressurized air inlet and a cold-end pressurized air outlet, and a cold-end expansion air inlet and a cold-end expansion air outlet. The hot-end pressurized turbine expander also has two sets of inlets and outlets: a hot-end pressurized air inlet and a hot-end pressurized air outlet, and a hot-end expansion air inlet and a hot-end expansion air outlet. The heat exchange cold box includes a hot-end heat exchanger, a cold-end heat exchanger, and a subcooler. The hot-end heat exchanger has four sets of inlets and outlets: a first inlet and a first outlet, a second inlet and a second outlet, a third inlet and a third outlet, and a fourth inlet and a fourth outlet. The cold-end heat exchanger has three sets of inlets and outlets: a first inlet and a first outlet, a second inlet and a second outlet, and a third inlet and a third outlet. A side outlet extends from the middle of the first inlet and the first outlet. The subcooler has two sets of inlets and outlets: a first subcooling inlet and a first subcooling outlet, and a second subcooling inlet and a second subcooling outlet. The air compressor, air cooler, refrigerated dryer, adsorption dryer, circulating booster compressor, and booster cooler are connected in series. The booster cooler has two outlets. One path is connected to the cold end pressurized air inlet. The cold end pressurized air outlet is connected to the hot end pressurized air inlet after passing through the cold end pressurized cooler. The hot end pressurized air outlet is connected to the first hot end heat exchange inlet after passing through the hot end pressurized cooler. The first hot end heat exchange outlet is connected to the hot end expansion air inlet. The hot end expansion air outlet is connected to the third hot end heat exchange inlet. The third hot end heat exchange outlet is connected to the inlet of the circulating pressurizer. Another path connects to the second inlet of the hot-end heat exchanger. The second outlet of the hot-end heat exchanger connects to the first inlet of the cold-end heat exchanger. The first outlet of the cold-end heat exchanger connects to the first subcooling inlet. The first subcooling outlet is divided into two paths: one path connects to the liquid air storage tank, and the other path connects to the second subcooling inlet. The second subcooling outlet connects to the third inlet of the cold-end heat exchanger. The third outlet of the cold-end heat exchanger connects to the fourth inlet of the hot-end heat exchanger. The fourth outlet of the hot-end heat exchanger connects to the adsorption dryer, providing desorption gas to the adsorption dryer. The side outlet is connected to the cold end expansion air inlet, the cold end expansion air outlet is connected to the cold end heat exchange second inlet, and the cold end heat exchange second outlet is connected to the hot end heat exchange third inlet. Throttling valves are installed between the first outlet of the cold end heat exchanger and the first inlet of the subcooling, between the first outlet of the subcooling and the liquid air storage tank, and between the first outlet of the subcooling and the second inlet of the subcooling; the circulating booster is a piston booster.

2. The liquid air production apparatus according to claim 1, characterized in that: The liquid air storage tank is provided with a storage tank vapor outlet, which is connected to the third inlet of the cold end heat exchange.

3. The liquid air production apparatus according to claim 1, characterized in that: The hot-end heat exchanger, cold-end heat exchanger, and subcooler all use aluminum alloy plate-fin heat exchangers and are arranged in three series within the heat exchange cold box.

4. A method for producing liquid air, characterized in that: Liquid air is produced using the liquid air production apparatus as described in any one of claims 1 to 3; The air is pressurized by the feed air compressor to obtain medium-pressure air, which then enters the air cooler. The cooled medium-pressure air is further cooled by a refrigerated dryer, and then passes through an adsorption dryer to remove moisture and carbon dioxide. The dried and clean medium-pressure air enters a circulating booster compressor for further pressurization to obtain high-pressure air, which is then divided into two paths: The air enters the cold end pressurized air inlet, is pressurized, cooled by the cold end pressurized cooler, and then enters the hot end pressurized air inlet. After being pressurized again, it is led out from the hot end pressurized air outlet, cooled by the hot end pressurized cooler, and then enters the first inlet of the hot end heat exchange. After being cooled, it is led out from the first outlet of the hot end heat exchange and then enters the hot end expansion air inlet. After being expanded and cooled, it is led out from the hot end expansion air outlet. The expanded medium-pressure air returns to the third inlet of the hot end heat exchange. The other path goes directly into the second inlet of the hot-end heat exchanger, cools down, exits from the second outlet of the hot-end heat exchanger, and then enters the first inlet of the cold-end heat exchanger. After cooling down, it splits into two paths in the middle of the cold-end heat exchanger: One path leads out from the side outlet and into the cold end expansion air inlet. The medium-pressure air obtained after expansion and cooling is led out from the cold end expansion air outlet and enters the second inlet of the cold end heat exchanger. After being reheated by the cold end heat exchanger, it is led out from the second outlet of the cold end heat exchanger and merges with the medium-pressure air led out from the hot end expansion air outlet. After being reheated to room temperature by the hot end heat exchanger, it returns to the inlet of the circulating booster compressor. Another stream of high-pressure liquid air, after being cooled and liquefied, is drawn out from the first outlet of the cold end heat exchanger, throttled, and then enters the first subcooling inlet. After subcooling, it is drawn out from the first subcooling outlet. The subcooled liquid air is divided into two parts. One part is throttled to atmospheric pressure and then returns to the second subcooling inlet. After vaporization and reheating, it is drawn out from the second subcooling outlet and then enters the third inlet of the cold end heat exchanger. After reheating, it is drawn out from the third outlet of the cold end heat exchanger and then enters the fourth inlet of the hot end heat exchanger. It continues to be reheated to room temperature and is drawn out from the fourth outlet of the hot end heat exchanger to the adsorption dryer. After desorption, it is discharged into the atmosphere. The other part is sent to the liquid air storage tank as liquid air product.

5. The method for producing liquid air according to claim 4, characterized in that: The high-pressure air obtained by the circulating booster is 2.8~3.2MPa, and then it is boosted to 4.5~4.9MPa by the cold end expansion booster and the hot end expansion booster.

6. The method for producing liquid air according to claim 4, characterized in that: The vapor from the liquid air storage tank is combined with the atmospheric pressure air after the subcooler and used as the desorption gas for the adsorption dryer.

7. The method for producing liquid air according to claim 4, characterized in that: The circulating booster uses stepless starting to reduce the impact of starting on the power grid.

8. The method for producing liquid air according to claim 4, characterized in that: Liquid air production facilities operate during periods of low electricity prices and shut down during periods of high electricity prices.

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