Liquid air production device

Abstract

The utility model discloses a liquid air production device, and belongs to the technical field of air liquefaction. Aiming at the problems of high energy consumption and high cost in the prior art, the multi-stage compression, expansion refrigeration and high-efficiency heat exchanger combination is adopted, so that the matching between the supercharge and the expansion is optimized, and the refrigeration efficiency is improved. The device comprises a raw material air compression system, an air cooling, drying and purifying system, a circulating pressurization system, an expansion refrigeration system, a heat exchange cold box and a liquid air storage tank. After being compressed, cooled, dried and purified, air enters the circulating pressurization system, and liquid air is produced through multi-stage expansion refrigeration and efficient heat exchange. According to the utility model, the production efficiency is improved, the cost is reduced, the energy utilization is optimized, and the vaporization loss is reduced. The liquid expansion machine is used for recovering pressure energy, and economical efficiency is improved.

Description

Technical Field

[0001] This utility model belongs to the field of air liquefaction technology and relates to a liquid air production device. Background Technology

[0002] Liquid air (LIFO) is a liquid form of air liquefied under low-temperature conditions. Its main components include nitrogen, oxygen, and small amounts of other gases. Because LIFO is a multi-component mixture with varying boiling points, its purity is unstable. In traditional air separation (ESS) technology, LIFO is typically used only as an intermediate product and has not been widely developed or applied independently. However, with the rapid development of new energy production capacity in my country, especially the in-depth research and exploration of LIFO and compressed air energy storage technologies, LIFO, due to its low temperature, large vapor expansion coefficient, and increasingly mature transportation and storage technologies, is gradually becoming an ideal energy storage medium. The application potential of LIFO is being gradually explored in multiple fields, and its unique physicochemical properties offer new possibilities for industrial production and energy utilization.

[0003] In recent years, with the transformation of the energy structure and the increasing demand for clean energy, the application of liquid air in the field of energy storage has received widespread attention. Liquid air absorbs a large amount of heat and undergoes significant volume expansion during vaporization, a characteristic that gives it significant advantages in energy recovery and power output. For example, in liquid air energy storage systems, by converting electrical energy into the cold energy of liquid air for storage, and then releasing the energy through vaporization when needed, peak shaving and valley filling of electricity load can be effectively achieved. Furthermore, the inherent oxygen content of liquid air makes it show potential for improving efficiency in metal smelting and oxygen-enriched combustion. Oxygen-enriched combustion technology can significantly improve fuel combustion efficiency and reduce greenhouse gas emissions, and the convenience of liquid air as an oxygen source further promotes its application in this field. At the same time, due to its dry and clean characteristics, liquid air is increasingly being adopted in environments with high environmental requirements, such as precision manufacturing and cleanrooms. Its low-temperature characteristics can also be used for cooling and temperature control, further broadening its application scope.

[0004] In the operation of air separation units, the utilization of liquid air is closely related to process optimization. In traditional air separation processes, some air is compressed and expanded for cooling, but the compression work of the expanded air that does not participate in distillation is often wasted. If the cooling capacity of liquid air is recovered and coupled with the air separation unit, it can not only replace part of the expansion refrigeration process, reducing the energy consumption required for cooling, but also increase the amount of feed air needed for separation by adding liquid air, thereby reducing the electricity consumption for feed air compression. This coupling method improves energy utilization efficiency and provides a technological foundation for low-cost liquid air production. However, existing liquid air production technologies still face some challenges. For example, traditional liquefaction processes have high energy consumption, limited cooling efficiency, and significant cooling losses during heat exchange, resulting in high production costs. Furthermore, the subcooling and storage stability of liquid air need further optimization to reduce vaporization losses and improve economic efficiency. Utility Model Content

[0005] In view of this, the purpose of this utility model is to solve the above problems and provide a liquid air production device.

[0006] To achieve the above objectives, this utility model provides the following technical solution:

[0007] A liquid air production apparatus includes a raw material air compression system, an air cooling, drying and purification system, a circulating pressurization system, an expansion refrigeration system, a heat exchange cold box, and a liquid air storage tank.

[0008] The raw material air compression system includes a feed air compressor and an air cooler; the air cooling drying and purification system includes a refrigerated dryer and an adsorption dryer; the circulating pressurization system includes a circulating pressurizer and a pressurization cooler.

[0009] The expansion and refrigeration system includes a cold-end turboexpander, a cold-end turbocooler, a hot-end turboexpander, a hot-end turbocooler, a subcooled turboexpander, and a liquid expander. The cold-end turboexpander has two sets of inlets and outlets: a cold-end turbocharger air inlet and a cold-end turbocharger air outlet, and a cold-end expander air inlet and a cold-end expander air outlet. The hot-end turboexpander has two sets of inlets and outlets: a hot-end turbocharger air inlet and a hot-end turbocharger air outlet, and a hot-end expander air inlet and a hot-end expander air outlet. The subcooled turboexpander has two sets of inlets and outlets: a subcooled turbocharger air inlet and a subcooled turbocharger air outlet, and a subcooled expander air inlet and a subcooled expander air outlet. The liquid expander has one set of inlets and outlets: a liquid expander liquid-air inlet and a liquid expander liquid-air outlet.

[0010] 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 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 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.

[0011] 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.

[0012] One path is connected to the air inlet of the subcooled turbocharger. The air outlet of the subcooled turbocharger is connected to the first inlet of the hot end heat exchanger after passing through the cold turbocharger cooler. The first outlet of the hot end heat exchanger is connected to the air inlet of the hot end expander. The air outlet of the hot end expander is connected to the third inlet of the hot end heat exchanger. The third outlet of the hot end heat exchanger is connected to the inlet of the circulating turbocharger.

[0013] Another path connects to the air inlet of the cold-end booster compressor. The air outlet of the cold-end booster compressor, after passing through the cold-end booster cooler, connects to the air inlet of the hot-end booster compressor. The air outlet of the hot-end booster compressor, after passing through the hot-end booster cooler, connects to the second inlet of the hot-end heat exchanger. The second outlet of the hot-end heat exchanger splits into two paths: one path connects to the air inlet of the cold-end expander, and the other path connects to the first inlet of the cold-end heat exchanger. The air outlet of the cold-end expander also splits into two paths: one path connects to the second inlet of the cold-end heat exchanger, and the other path connects to the third inlet of the cold-end heat exchanger. The second outlet of the cold-end heat exchanger and the air outlet of the hot-end expander merge and connect to the third inlet of the hot-end heat exchanger. The third outlet of the cold-end heat exchanger connects to the air inlet of the subcooled expander. The air outlet of the subcooled expander connects to the second subcooled inlet. The second subcooled outlet connects to the fourth inlet of the cold-end heat exchanger. The fourth 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.

[0014] The first outlet of the cold end heat exchange is connected to the liquid air inlet of the liquid expander, and the liquid air outlet of the liquid expander is connected to the first subcooling inlet. The first subcooling outlet is divided into two paths: one path is connected to the liquid air storage tank, and the other path is connected to the second subcooling inlet after merging with the air outlet of the subcooling expander.

[0015] Furthermore, throttling valves are installed between the first subcooled outlet and the liquid air storage tank, and between the first subcooled outlet and the second subcooled inlet.

[0016] Furthermore, 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.

[0017] Furthermore, the circulating booster is a centrifugal booster.

[0018] Furthermore, the hot-end heat exchanger, cold-end heat exchanger, and subcooler all adopt aluminum alloy plate-fin heat exchangers and are arranged in three series within the heat exchange cold box.

[0019] Air is pressurized by a feed air compressor to obtain medium-pressure air, which then enters an 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 streams:

[0020] The air enters the subcooled booster air inlet, and after being boosted, it is cooled by the booster cooler and then enters the first inlet of the hot end heat exchanger. After being cooled in the heat exchanger, it is drawn out from the first outlet of the hot end heat exchanger and then enters the air inlet of the hot end expander. After being expanded and cooled, it is drawn out from the hot end expansion air outlet. The expanded medium-pressure air returns to the third inlet of the hot end heat exchanger.

[0021] Another path enters the air inlet of the cold-end booster compressor. The boosted air is cooled by the cold-end booster cooler and then enters the air inlet of the hot-end booster compressor. After being boosted again, it exits from the hot-end booster compressor air outlet, is cooled by the hot-end booster cooler, and then enters the second inlet of the hot-end heat exchanger. After cooling, it exits from the second outlet of the hot-end heat exchanger and then splits into two paths:

[0022] One stream of air enters the cold-end expander air inlet. After expansion and cooling, the resulting medium-pressure air is drawn out from the cold-end expander air outlet. The drawn-out medium-pressure air is then divided into two streams. One stream enters the second inlet of the cold-end heat exchanger. After heat exchange, the medium-pressure air merges with the medium-pressure air drawn from the hot-end expander air outlet and enters the third inlet of the hot-end heat exchanger. After being reheated to room temperature by the heat exchanger, it returns to the circulation booster inlet. The other stream enters the third inlet of the cold-end heat exchanger. After heat exchange, it is drawn out from the third outlet of the cold-end heat exchanger and then enters the subcooled expander air inlet. The low-pressure air after expansion and cooling is drawn out from the subcooled expander air outlet and then enters the second subcooled inlet.

[0023] Another path enters the first inlet of the cold end heat exchanger. After being cooled by the heat exchanger, the air becomes high-pressure liquid air and is drawn out from the first outlet of the cold end heat exchanger. Then it enters the liquid air inlet of the liquid expander. After being cooled and depressurized by the liquid expander, the medium-pressure liquid air is drawn out from the liquid air outlet of the liquid expander and enters the first subcooling inlet. After being subcooled by the cooler, part of the liquid air is throttled to atmospheric pressure and sent to the liquid air storage tank as liquid air product. The other part is throttled to atmospheric pressure and merges with the air outlet of the subcooled expander. It then returns to the second subcooling inlet, vaporizes and reheats, and is drawn out from the second subcooling outlet. It then enters the fourth inlet of the cold end heat exchanger. After reheating, it is drawn out from the fourth outlet of the cold end heat exchanger and 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.

[0024] Furthermore, the high-pressure air obtained by the circulating supercharger is 2.8 to 3.2 MPa (A), and is then further pressurized to 6.0 to 6.4 MPa (A) by the cold-end expansion supercharger and the hot-end expansion supercharger.

[0025] Furthermore, it is pressurized to 3.3–3.5 MPa (A) by a cold expansion booster.

[0026] Furthermore, the atmospheric air expanded by the subcooled expander and the atmospheric liquid air after throttling are combined and then passed through a cooler, a cold-end heat exchanger, and a hot-end heat exchanger. The air that is vaporized and reheated is used as the desorption gas of the adsorption dryer.

[0027] Furthermore, the circulating booster uses variable frequency start-up to reduce the impact on the power grid during startup; the liquid air production unit operates during periods of low electricity prices and shuts down during periods of high electricity prices.

[0028] The beneficial effects of this utility model are as follows:

[0029] 1. This utility model adopts a combination of multi-stage compression, expansion refrigeration and high-efficiency heat exchanger, and uses a pressurized turbine expansion mechanism to extract cooling capacity. It effectively matches the pressurization and expansion capacity, thereby improving the expansion refrigeration efficiency.

[0030] 2. The heat exchange section is divided into three parts: a hot-end heat exchanger, a cold-end heat exchanger, and a subcooler. The temperatures before and after the expander are optimized and regulated. This optimizes the energy utilization efficiency during the air liquefaction process, significantly improving the production efficiency of liquid air and reducing its production cost.

[0031] 3. This utility model uses three gas expanders, which effectively solves the contradiction between the cooling capacity balance of each heat exchanger and the subcooling of liquid air, increases the cooling capacity, reduces the temperature difference of the heat exchangers, increases the subcooling of the liquid air product, reduces the vaporization loss of the liquid air product, and reduces the unit energy consumption of the product.

[0032] 4. This utility model uses a liquid expander, which effectively recovers the pressure energy of high-pressure air, reduces the temperature before liquid air subcooling, and increases the economic efficiency of the device.

[0033] 5. This invention utilizes the reheated vapor of atmospheric pressure liquid air as the desorption gas in an adsorption dryer, saving on the compression cost of the raw material gas. It can also produce liquid air during periods of low electricity prices, thus playing a role in regulating the power grid.

[0034] Other advantages, objectives, and features of this invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination and study, or may be learned from practice of this invention. The objectives and other advantages of this invention can be realized and obtained through the following description. Attached Figure Description

[0035] To make the objectives, technical solutions, and advantages of this utility model clearer, the preferred embodiments of this utility model will be described in detail below with reference to the accompanying drawings, wherein:

[0036] Figure 1 This is a schematic diagram of the liquid air production device in this utility model.

[0037] Figure reference numerals: 1-Feed air compressor; 2-Air cooler; 3-Refrigerated dryer; 4-Adsorption dryer; 5-Circulating booster compressor; 6-Booster cooler; 7-Cold-end booster turbine expander; 8-Cold-end booster cooler; 9-Hot-end booster turbine expander; 10-Hot-end booster cooler; 11-Subcooled booster turbine expander; 12-Subcooled booster cooler; 13-Hot-end heat exchanger; 14-Cold-end heat exchanger; 15-Liquid expander; 16-Subcooler; 17-Liquid air storage tank; 1001-Feed air compressor inlet; 1002-Feed air compressor outlet; 21-Air inlet; 22-Air outlet; 23-Cooling water inlet; 24-Cooling water outlet; 31-Refrigerated dryer inlet; 32 - Refrigerated dryer outlet; 41 - Desiccant air inlet; 42 - Desiccant air outlet; 43 - Desiccant desorbed gas inlet; 44 - Desiccant desorbed gas outlet; 51 - Circulating booster inlet; 52 - Circulating booster 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 expander air inlet; 74 - Cold end expander 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 expander air inlet; 94-Hot-end expander air outlet; 101-Hot-end cooling air inlet; 102-Hot-end cooling air outlet; 103-Cooling water inlet; 104-Cooling water outlet; 111-Subcooled turbocharger air inlet; 112-Subcooled turbocharger air outlet; 113-Subcooled expander air inlet; 114-Subcooled expander air outlet; 121-Subcooled turbocharger cooling air inlet; 122-Subcooled turbocharger cooling air outlet; 103-Cooling water inlet; 104-Cooling water outlet; 131-Hot-end heat exchanger first inlet; 132-Hot-end heat exchanger first outlet; 133-Hot-end heat exchanger second inlet; 134-Hot-end heat exchanger second outlet; 135-Hot-end heat exchanger... 136 - Hot end heat exchange third outlet; 137 - Hot end heat exchange fourth outlet; 138 - Hot end heat exchange fourth inlet; 141 - Cold end heat exchange first inlet; 142 - Cold end heat exchange first outlet; 143 - Cold end heat exchange second outlet; 144 - Cold end heat exchange second inlet; 145 - Cold end heat exchange third outlet; 146 - Cold end heat exchange third inlet; 147 - Cold end heat exchange fourth outlet; 148 - Cold end heat exchange fourth inlet; 151 - Liquid expander liquid air inlet; 152 - Liquid expander liquid air outlet; 153 - Generator; 161 - Subcooling first inlet; 162 - Subcooling first outlet; 163 - Subcooling second outlet; 164 - Subcooling second inlet; 171 - Storage tank inlet. Detailed Implementation

[0038] The following specific examples illustrate the implementation of this utility model. Those skilled in the art can easily understand other advantages and effects of this utility model from the content disclosed in this specification. This utility model can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this utility model. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of this utility model. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0039] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the present invention. To better illustrate the embodiments of the present invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0040] In the accompanying drawings of this utility model, the same or similar reference numerals correspond to the same or similar components. In the description of this utility model, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting this utility model. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0041] Please see Figure 1 A liquid air production device 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 17.

[0042] The raw material air compression system includes a feed air compressor 1 and an air cooler 2; the air cooling and drying system includes a refrigerated dryer 3 and an adsorption dryer 4; the circulating booster system includes a circulating booster compressor 5 and a booster cooler 6; the air cooler 2 is equipped with two sets of inlets and outlets, namely an air inlet 21, an air outlet 22, a cooling water inlet 23, and a cooling water outlet 24; the adsorption dryer 4 is equipped with two sets of inlets and outlets, namely a dryer air inlet 41, a dryer air outlet 42, a dryer desorption gas inlet 43, and a dryer desorption gas outlet 44. The booster cooler 6 is equipped with a circulating booster air inlet 61, a circulating booster air outlet 62, a cooling water inlet 63, and a cooling water outlet 64.

[0043] The expansion refrigeration system includes a cold-end booster turbine expander 7, a cold-end booster cooler 8, a hot-end booster turbine expander 9, a hot-end booster cooler 10, a subcooled booster turbine expander 11, a subcooled booster cooler 12, and a liquid expander 15. The cold-end booster turbine expander 7 has two sets of inlets and outlets: a cold-end booster air inlet 71 and a cold-end booster air outlet 72, and a cold-end expander air inlet 73 and a cold-end expander air outlet 74. The cold-end booster cooler 8 has two sets of inlets and outlets: a cold-end cooling air inlet 81 and a cold-end cooling air outlet 82, and a cooling water inlet 83 and a cooling water outlet 84. The hot-end booster turbine expander 9 has two sets of inlets and outlets: a hot-end booster air inlet 91 and a hot-end booster air outlet 92, and a hot-end expander air inlet 93 and a hot-end expander air outlet. 94; The hot-end supercharger cooler 10 is provided with two sets of inlets and outlets, namely hot-end cooling air inlet 101, hot-end cooling air outlet 102, cooling water inlet 103, and cooling water outlet 104; The subcooled supercharger turbo expander 11 is provided with two sets of inlets and outlets, namely subcooled supercharger air inlet 111 and subcooled supercharger air outlet 112, subcooled expander air inlet 113 and subcooled expander air outlet 114; The subcooled supercharger cooler 12 is provided with two sets of inlets and outlets, namely subcooled supercharger cooling air inlet 121 and subcooled supercharger cooling air outlet 122, cooling water inlet 123, and cooling water outlet 124; The liquid expander 15 is provided with one set of inlets and outlets, namely liquid expander liquid air inlet 151 and liquid expander liquid air outlet 152; At the same time, the liquid expander 15 is braked by a generator 153.

[0044] The heat exchange cold box includes a hot-end heat exchanger 13, a cold-end heat exchanger 14, and a subcooler 16. The hot-end heat exchanger 13 has four sets of inlets and outlets: a first inlet 131 and a first outlet 132, a second inlet 133 and a second outlet 134, a third inlet 136 and a third outlet 135, and a fourth inlet 138 and a fourth outlet 137. The cold-end heat exchanger 14 has four sets of inlets and outlets: a hot-end heat exchanger 131 and a cold-end heat exchanger 14, and a subcooler 16. The first inlet 141 is connected to the first outlet 142 of the cold end heat exchange, the second inlet 144 of the cold end heat exchange is connected to the second outlet 143 of the cold end heat exchange, the third inlet 146 of the cold end heat exchange is connected to the third outlet 145 of the cold end heat exchange, and the fourth inlet 148 of the cold end heat exchange is connected to the fourth outlet 147 of the cold end heat exchange; the subcooler 16 is provided with two sets of inlets and outlets, namely the first subcooling inlet 161 and the first subcooling outlet 162, and the second subcooling inlet 164 and the second subcooling outlet 163; the liquid air storage tank 17 is provided with a storage tank inlet 171.

[0045] The following components are connected in series: air compressor 1, air cooler 2, refrigerated dryer 3, adsorption dryer 4, circulating booster compressor 5, and booster cooler 6. Specifically, the air compressor inlet 1001, air compressor outlet 1002, air inlet 21, air outlet 22, refrigerated dryer inlet 31, refrigerated dryer outlet 32, adsorption dryer air inlet 41, adsorption dryer air outlet 42, circulating booster inlet 51, circulating booster outlet 52, circulating booster air inlet 61, and circulating booster air outlet 62 are connected sequentially. The circulating booster air outlet 62 of the booster cooler 6 is divided into two paths:

[0046] One path is connected to the air inlet 111 of the subcooled turbocharger. The air outlet 112 of the subcooled turbocharger is connected to the first inlet 131 of the hot end heat exchanger after passing through the cold turbocharger cooler 12. The first outlet 132 of the hot end heat exchanger is connected to the air inlet 93 of the hot end expander. The air outlet 94 of the hot end expander is connected to the third inlet 136 of the hot end heat exchanger. The third outlet 135 of the hot end heat exchanger is connected to the circulating turbocharger inlet 51.

[0047] Another path connects to the cold-end booster air inlet 71. The cold-end booster air outlet 72, after passing through the cold-end booster cooler 8, connects to the hot-end booster air inlet 91. The hot-end booster air outlet 92, after passing through the hot-end booster cooler 10, connects to the hot-end heat exchange second inlet 133. The hot-end heat exchange second outlet 134 splits into two paths: one connects to the cold-end expander air inlet 73, and the other connects to the cold-end heat exchange first inlet 141. The cold-end expander air outlet 74 also splits into two paths: one connects to the cold-end heat exchange second inlet 144, and the other connects to the cold-end heat exchange second inlet 141. The three inlets 146, the second outlet 143 of the cold end heat exchange and the air outlet 94 of the hot end expander are connected to the third inlet 136 of the hot end heat exchange, the third outlet 145 of the cold end heat exchange is connected to the air inlet 113 of the subcooled expander, the air outlet 114 of the subcooled expander is connected to the second subcooled inlet 164, the second subcooled outlet 163 is connected to the fourth inlet 148 of the cold end heat exchange, the fourth outlet 147 of the cold end heat exchange is connected to the fourth inlet 138 of the hot end heat exchange, and the fourth outlet 137 of the hot end heat exchange is connected to the adsorption dryer 4, providing desorption gas to the adsorption dryer;

[0048] The first outlet 142 of the cold end heat exchanger is connected to the liquid air inlet 151 of the liquid expander, and the liquid air outlet 152 of the liquid expander is connected to the first subcooling inlet 161. The first subcooling outlet 162 is divided into two paths: one path is connected to the liquid air storage tank 17, and the other path is connected to the second subcooling inlet 164 after merging with the air outlet 114 of the subcooling expander.

[0049] A liquid expander 15 is used instead of a throttle valve to reduce pressure between the first outlet 142 of the cold end heat exchange and the first inlet 161 of the subcooling.

[0050] A throttling valve V2 is installed between the first subcooling outlet 162 and the liquid air storage tank 17, and a throttling valve V1 is installed between the first subcooling outlet 162 and the second subcooling inlet 164.

[0051] The liquid air storage tank 17 is equipped with a tank inlet 171 connected to the first subcooling outlet 162.

[0052] Among them, the air compressor 1 is a screw compressor, and the circulating booster 5 is a piston booster to adapt to frequent start-stop.

[0053] The hot-end heat exchanger 13, the cold-end heat exchanger 14, and the subcooler 16 all adopt aluminum alloy plate-fin heat exchangers and are arranged in three series in the heat exchange cold box.

[0054] The liquid air production process using the aforementioned liquid air production apparatus is as follows:

[0055] Air is pressurized to 0.54 MPa (A) by the feed air compressor 1 to obtain medium-pressure air, which then enters the air cooler 2. The cooled medium-pressure air is further cooled to 10°C by the refrigerated dryer 3, and then passes through the adsorption dryer 4 to remove moisture and carbon dioxide. The dried and clean medium-pressure air enters the circulating booster compressor 5 to be further pressurized to 3.0 MPa (A) to obtain high-pressure air, which is then divided into two paths:

[0056] The air enters the subcooled booster air inlet 111, and after being boosted, it is cooled by the booster cooler 12 and then enters the first inlet 131 of the hot end heat exchanger. After being cooled in the hot end heat exchanger 13, it is drawn out from the first outlet 132 of the hot end heat exchanger and then enters the hot end expander air inlet 93. After expansion and cooling, it is drawn out from the hot end expander air outlet 94. The expanded medium-pressure air returns to the third inlet 136 of the hot end heat exchanger.

[0057] Another path enters the cold-end booster air inlet 71. After being boosted, the air is cooled by the cold-end booster cooler 8 and then enters the hot-end booster air inlet 91. It is boosted again to 6.22 MPa (A) and then exits from the hot-end booster air outlet 92. After being cooled by the hot-end booster cooler 10, it enters the second inlet 133 of the hot-end heat exchanger. After being cooled, it exits from the second outlet 134 of the hot-end heat exchanger and then splits into two paths:

[0058] One stream of air enters the cold-end expander air inlet 73, expands and cools, and then exits from the cold-end expander air outlet 74. The exiting air then splits into two streams. One stream enters the second cold-end heat exchange inlet 144, where it merges with the air exiting the hot-end expander air outlet 94 and enters the third hot-end heat exchange inlet 136. After being reheated to room temperature by the heat exchanger, it returns to the circulation booster inlet 51. The other stream enters the third cold-end heat exchange inlet 146, expands and cools, and then exits from the third cold-end heat exchange outlet 145. It then enters the subcooled expander air inlet 113, expands and cools, and exits from the subcooled expander air outlet 114, entering the second subcooling inlet 164. The third stream enters the first cold-end heat exchange inlet 141, where it is cooled and becomes high-pressure liquid air, exiting from the first cold-end heat exchange outlet 142. The air then enters the liquid air inlet 151 of the liquid expander. After being cooled and depressurized by the liquid expander, the medium-pressure liquid air is drawn out from the liquid air outlet 152 of the liquid expander and enters the first subcooling inlet 161. After being subcooled by the cooler, part of the liquid air is throttled to 0.178 MPa (A) by the throttle valve V1 and sent to the liquid air storage tank 17 as liquid air product. The other part is throttled to 0.13 MPa (A) by the throttle valve V2 and merges with the air outlet 114 of the subcooled expander. It then returns to the second subcooling inlet 164, vaporizes and reheats, and is drawn out from the second subcooling outlet 163. It then enters the fourth cold end heat exchange inlet 148, is reheated, and is drawn out from the fourth cold end heat exchange outlet 147. It then enters the fourth hot end heat exchange inlet 138, continues to be reheated to room temperature, and is drawn out from the fourth hot end heat exchange outlet 137 to the adsorption dryer 4. After desorption, it is discharged into the atmosphere.

[0059] In this embodiment, the circulating booster compressor 5 adopts variable frequency start-up to reduce the impact on the power grid during startup. The liquid air production unit operates during periods of low electricity prices and shuts down during periods of high electricity prices.

[0060] The raw material air used in this embodiment is 37300 Nm³. 3 / h, 0.098MPa(A). Product liquid air obtained: 26700Nm 3 / h (converted to gaseous state).

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of this utility model and are not intended to limit it. Although this utility model has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solution of this utility model without departing from the spirit and scope of this technical solution, and all such modifications or substitutions should be covered within the scope of the claims of this utility model.

Claims

1. A liquid air production apparatus, characterized in that: This includes a raw material air compression system, an air cooling, drying and purification 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 drying and purification 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 cold-end turboexpander, a cold-end turbocooler, a hot-end turboexpander, a hot-end turbocooler, a subcooled turboexpander, and a liquid expander. The cold-end turboexpander has two sets of inlets and outlets: a cold-end turbocharger air inlet and a cold-end turbocharger air outlet, and a cold-end expander air inlet and a cold-end expander air outlet. The hot-end turboexpander has two sets of inlets and outlets: a hot-end turbocharger air inlet and a hot-end turbocharger air outlet, and a hot-end expander air inlet and a hot-end expander air outlet. The subcooled turboexpander has two sets of inlets and outlets: a subcooled turbocharger air inlet and a subcooled turbocharger air outlet, and a subcooled expander air inlet and a subcooled expander air outlet. The liquid expander has one set of inlets and outlets: a liquid expander liquid-air inlet and a liquid expander liquid-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 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 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 air inlet of the subcooled turbocharger. The air outlet of the subcooled turbocharger is connected to the first inlet of the hot end heat exchanger after passing through the cold turbocharger cooler. The first outlet of the hot end heat exchanger is connected to the air inlet of the hot end expander. The air outlet of the hot end expander is connected to the third inlet of the hot end heat exchanger. The third outlet of the hot end heat exchanger is connected to the inlet of the circulating turbocharger. Another path connects to the air inlet of the cold-end booster compressor. The air outlet of the cold-end booster compressor, after passing through the cold-end booster cooler, connects to the air inlet of the hot-end booster compressor. The air outlet of the hot-end booster compressor, after passing through the hot-end booster cooler, connects to the second inlet of the hot-end heat exchanger. The second outlet of the hot-end heat exchanger splits into two paths: one path connects to the air inlet of the cold-end expander, and the other path connects to the first inlet of the cold-end heat exchanger. The air outlet of the cold-end expander also splits into two paths: one path connects to the second inlet of the cold-end heat exchanger, and the other path connects to the third inlet of the cold-end heat exchanger. The second outlet of the cold-end heat exchanger and the air outlet of the hot-end expander merge and connect to the third inlet of the hot-end heat exchanger. The third outlet of the cold-end heat exchanger connects to the air inlet of the subcooled expander. The air outlet of the subcooled expander connects to the second subcooled inlet. The second subcooled outlet connects to the fourth inlet of the cold-end heat exchanger. The fourth 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 first outlet of the cold end heat exchange is connected to the liquid air inlet of the liquid expander, and the liquid air outlet of the liquid expander is connected to the first subcooling inlet. The first subcooling outlet is divided into two paths: one path is connected to the liquid air storage tank, and the other path is connected to the second subcooling inlet after merging with the air outlet of the subcooling expander.

2. The liquid air production apparatus according to claim 1, characterized in that: Throttling valves are installed between the first subcooled outlet and the liquid air storage tank, and between the first subcooled outlet and the second subcooled inlet.

3. 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.

4. The liquid air production apparatus according to claim 1, characterized in that: The circulating booster is a centrifugal booster.

5. 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.

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