Method and device for producing liquid air

Abstract

The invention discloses a liquid air production method and device, and belongs to the technical field of air liquefaction. In order to solve the problems of high energy consumption and high cost in the prior art, through combination of multi-stage compression, expansion refrigeration and the efficient heat exchanger, matching of the supercharge amount and the expansion amount 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. According to the method, air is compressed, cooled, dried and purified and then enters a circulating pressurization system, and liquid air is produced through multi-stage expansion refrigeration and efficient heat exchange. According to the invention, the production efficiency is improved, the cost is reduced, the energy utilization is optimized, and the vaporization loss is reduced. And the effect of adjusting the load of the power grid is achieved by utilizing low-electricity-price period production. The liquid expansion machine is used for recovering pressure energy, and economical efficiency is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of air liquefaction, and relates to a method and device for producing liquid air. Background Art

[0002] Liquid air (abbreviated as liquid oxygen) is a liquid form formed by the liquefaction of air under low-temperature conditions. Its main components include nitrogen, oxygen and a small amount of other gases. Since liquid air is a multi-component mixture and the boiling points of its components are different, it has unstable characteristics in terms of purity. In traditional air separation (abbreviated as AS) technology, liquid air is usually only used as an intermediate product in the process and has not been widely developed and independently applied. However, with the rapid development of new quality productivity in China, especially the in-depth research and exploration of liquid air energy storage and compressed air energy storage technologies, liquid air has gradually become an ideal energy storage carrier due to its low temperature, large vaporization expansion coefficient and the increasing maturity of transportation and storage technologies. The application potential of liquid air is being gradually explored in multiple fields, and its unique physical and chemical properties provide 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 wide attention. Liquid air can absorb a large amount of heat and produce a significant volume expansion during the vaporization process, which makes it have significant advantages in energy recovery and power output. For example, in a liquid air energy storage system, by converting electrical energy into the cold energy of liquid air for storage and then releasing the energy through vaporization when needed, the peak shaving and valley filling of the power load can be effectively achieved. In addition, the inherent oxygen content characteristics of liquid air make it show the application potential of improving efficiency in the fields of metal smelting and oxy-fuel combustion. Oxy-fuel combustion technology can significantly improve the combustion efficiency of fuels and reduce greenhouse gas emissions, and the convenience of liquid air as a source of oxygen further promotes its application in this field. At the same time, due to its dry and clean characteristics, liquid air is gradually being adopted in scenarios with high environmental requirements such as precision manufacturing and dust-free workshops, and its low-temperature characteristics can also be used for cooling and temperature control, further expanding its application scope.

[0004] In the operation of an air separation unit, the utilization of liquid air is closely related to process optimization. In traditional air separation processes, part of the air is used for cold supply after compression and expansion refrigeration, but the compression work of the expanded air that does not participate in rectification is often wasted. If the cold energy of liquid air is recovered and coupled with the air separation unit, it can not only replace part of the expansion refrigeration process, reduce the energy consumption required for refrigeration, but also increase the raw material air required for separation by adding liquid air, thereby reducing the power consumption for raw material air compression. This coupling method improves the energy utilization efficiency while providing a technical basis for the low-cost production of liquid air. However, existing liquid air production technologies still face some challenges. For example, traditional liquefaction processes have high energy consumption, limited refrigeration efficiency, and significant cold energy losses during heat exchange, resulting in high production costs. In addition, the subcooling degree and storage stability of liquid air also need to be further optimized to reduce vaporization losses and improve economic efficiency. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to solve the above problems and provide a method and device for producing liquid air.

[0006] To achieve the above purpose, the present invention provides the following technical solutions:

[0007] A liquid air production device 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 feeding air compressor and an air cooler; the air cooling, drying, and purification system includes a cold dryer and an adsorption dryer; the circulating pressurization system includes a circulating pressurizer and a pressurization cooler;

[0009] The expansion refrigeration system includes a cold-end pressurized turboexpander, a cold-end pressurization cooler, a hot-end pressurized turboexpander, a hot-end pressurization cooler, a subcooling pressurized turboexpander, and a liquid expander; the cold-end pressurized turboexpander is provided with two sets of inlets and outlets, namely a cold-end pressurizer air inlet and a cold-end pressurizer air outlet, a cold-end expander air inlet and a cold-end expander air outlet; the hot-end pressurized turboexpander is provided with two sets of inlets and outlets, namely a hot-end pressurizer air inlet and a hot-end pressurizer air outlet, a hot-end expander air inlet and a hot-end expander air outlet; the subcooling pressurized turboexpander is provided with two sets of inlets and outlets, namely a subcooling pressurizer air inlet and a subcooling pressurizer air outlet, a subcooling expander air inlet and a subcooling expander air outlet; the liquid expander is provided with a set of inlets and outlets, namely 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 is provided with four groups of inlets and outlets, namely the first hot end heat exchange inlet and the first hot end heat exchange outlet, the second hot end heat exchange inlet and the second hot end heat exchange outlet, the third hot end heat exchange inlet and the third hot end heat exchange outlet, and the fourth hot end heat exchange inlet and the fourth hot end heat exchange outlet; the cold end heat exchanger is provided with four groups of inlets and outlets, namely the first cold end heat exchange inlet and the first cold end heat exchange outlet, the second cold end heat exchange inlet and the second cold end heat exchange outlet, the third cold end heat exchange inlet and the third cold end heat exchange outlet, and the fourth cold end heat exchange inlet and the fourth cold end heat exchange outlet; the subcooler is provided with two groups of inlets and outlets, namely the first subcooling inlet and the first subcooling outlet, and the second subcooling inlet and the second subcooling outlet;

[0011] The feeding air compressor, air cooler, cold dryer, adsorption dryer, recycle booster, and booster cooler are connected in series in sequence. The outlet of the booster cooler is divided into two paths:

[0012] One path is communicated with the air inlet of the subcooling booster. The air outlet of the subcooling booster is communicated with the first hot end heat exchange inlet after passing through the subcooling booster cooler. The first hot end heat exchange outlet is communicated with the air inlet of the hot end expander. The air outlet of the hot end expander is communicated with the third hot end heat exchange inlet. The third hot end heat exchange outlet is communicated with the inlet of the recycle booster;

[0013] The other path is communicated with the air inlet of the cold end booster. The air outlet of the cold end booster is communicated with the air inlet of the hot end booster after passing through the cold end booster cooler. The air outlet of the hot end booster is communicated with the second hot end heat exchange inlet after passing through the hot end booster cooler. The second hot end heat exchange outlet is divided into two paths. One path is communicated with the air inlet of the cold end expander, and the other path is communicated with the first cold end heat exchange inlet; the air outlet of the cold end expander is further divided into two paths. One path is communicated with the second cold end heat exchange inlet, and the other path is communicated with the third cold end heat exchange inlet. The second cold end heat exchange outlet converges with the air outlet of the hot end expander and then is connected to the third hot end heat exchange inlet. The third cold end heat exchange outlet is communicated with the air inlet of the subcooling expander. The air outlet of the subcooling expander is communicated with the second subcooling inlet. The second subcooling outlet is communicated with the fourth cold end heat exchange inlet. The fourth cold end heat exchange outlet is communicated with the fourth hot end heat exchange inlet. The fourth hot end heat exchange outlet is communicated with the adsorption dryer to provide desorbed gas to the adsorption dryer;

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

[0015] Furthermore, throttle valves are provided between the first subcooling outlet and the liquid air storage tank, and between the first subcooling outlet and the second subcooling inlet.

[0016] Further, a vapor outlet is provided on the liquid air storage tank, and the liquid air vapor outlet is communicated with the third inlet of the cold end heat exchanger.

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

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

[0019] A method for producing liquid air uses the above-described liquid air production device to produce liquid air;

[0020] Air is pressurized by a feed air compressor to obtain medium-pressure air, which enters an air cooler; the cooled medium-pressure air is further cooled by a cold dryer, and then moisture and carbon dioxide are removed by an adsorption dryer; the dry and clean medium-pressure air enters a circulating booster to be further pressurized to obtain high-pressure air, which is then divided into two paths:

[0021] One path enters the air inlet of the subcooling booster. The pressurized air is cooled by a booster cooler and then enters the first inlet of the hot end heat exchanger. After being cooled in the heat exchanger, it is led out from the first outlet of the hot end heat exchanger, and then enters the air inlet of the hot end expander. After expansion refrigeration, it is led out from the air outlet of the hot end expander. The expanded medium-pressure air returns to the third inlet of the hot end heat exchanger;

[0022] The other path enters the air inlet of the cold end booster. The pressurized air is cooled by a cold end booster cooler and then enters the air inlet of the hot end booster. After being pressurized again, it is led out from the air outlet of the hot end booster. After being cooled by the hot end booster cooler, it enters the second inlet of the hot end heat exchanger. After being cooled, it is led out from the second outlet of the hot end heat exchanger, and then is divided into two paths:

[0023] One path enters the air inlet of the cold end expander. The medium-pressure air obtained after expansion refrigeration is led out from the air outlet of the cold end expander. The led-out medium-pressure air is again divided into two paths. One path enters the second inlet of the cold end heat exchanger. After heat exchange, the medium-pressure air converges with the medium-pressure air led out from the air outlet of the hot end expander, and then enters the third inlet of the hot end heat exchanger together. After being reheated to room temperature in the heat exchanger, it returns to the circulating booster inlet; the other path enters the third inlet of the cold end heat exchanger. After heat exchange, it is led out from the third outlet of the cold end heat exchanger, and then enters the air inlet of the subcooling expander. The low-pressure air after expansion refrigeration is led out from the air outlet of the subcooling expander. The led-out air enters the second subcooling inlet;

[0024] Another path enters the first inlet of the cold-end heat exchanger. After the air is cooled through heat exchange, it becomes high-pressure liquid air and is led out from the first outlet of the cold-end heat exchanger. Then it enters the liquid inlet of the liquid expander. The medium-pressure liquid air after being cooled and depressurized by the liquid expander is led out from the liquid outlet of the liquid expander and enters the first inlet of the subcooler. A part of the liquid air after being subcooled by the subcooler is throttled to atmospheric pressure and sent to the liquid air storage tank as the liquid air product. Another part is throttled to atmospheric pressure, converges with the air outlet of the subcooled expander, then returns to the second inlet of the subcooler, is vaporized and reheated, and is led out from the second outlet of the subcooler. Then it enters the fourth inlet of the cold-end heat exchanger, is reheated and led out from the fourth outlet of the cold-end heat exchanger. Then it enters the fourth inlet of the hot-end heat exchanger, continues to be reheated to room temperature and is led out from the fourth outlet of the hot-end heat exchanger to the adsorption dryer, and is discharged to the atmosphere after desorption.

[0025] Further, the high-pressure air obtained by being pressurized by the circulating booster is at a pressure of 2.8 - 3.2 MPa(A), and is further pressurized to 6.0 - 6.4 MPa(A) by the cold-end expansion booster and the hot-end expansion booster.

[0026] Further, it is pressurized to 3.3 - 3.5 MPa(A) by the subcooled expansion booster.

[0027] Further, the atmospheric-pressure air after expansion by the subcooled expander converges with the throttled atmospheric-pressure liquid air, then passes through the subcooler, the cold-end heat exchanger, and the hot-end heat exchanger, and the air after being vaporized and reheated is used as the desorption gas of the adsorption dryer.

[0028] Further, the circulating booster adopts frequency conversion start to reduce the impact on the power grid during startup; the production device of liquid air operates during the low electricity price period and stops during the high electricity price period.

[0029] The beneficial effects of the present invention are as follows:

[0030] 1. By adopting the method of multi-stage compression, expansion refrigeration and combination of high-efficiency heat exchangers, and using a turbo-expander to obtain cold energy, the present invention effectively matches the pressurization amount and the expansion amount, and improves the expansion refrigeration efficiency.

[0031] 2. The heat exchange part is divided into three sections, including the hot-end heat exchanger, the cold-end heat exchanger and the subcooler, which optimally adjusts the temperature before and after the expander. The energy utilization efficiency in the air liquefaction process is optimized, the production efficiency of liquid air is significantly improved, and the production cost of liquid air is reduced.

[0032] 3. The present invention adopts three gas expanders, effectively solves the contradiction between the cold energy balance of each heat exchanger and the subcooling degree of liquid air, increases the refrigeration capacity, reduces the temperature difference of the heat exchanger, increases the subcooling degree of the liquid air product, reduces the gasification loss of the liquid air product, and reduces the unit energy consumption of the product.

[0033] 4. The present invention employs a liquid expander, effectively recovering the pressure energy of high-pressure air, reducing the temperature before liquid air subcooling, and increasing the economy of the device.

[0034] 5. The present invention produces liquid air during periods of low electricity prices, which has the effect of regulating the power grid.

[0035] 6. The present invention uses the vapor of normal-pressure liquid air after reheating as the desorbing gas of the adsorption dryer, saving the compression cost of the raw material gas. Other advantages, objectives, and features of the present invention will be described to some extent in the subsequent specification, and to some extent, will be obvious to those skilled in the art based on the study of the following text, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be achieved and obtained through the following specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be described in detail preferably with reference to the accompanying drawings, where:

[0037] Figure 1 It is the schematic diagram of the production device of liquid air in the present invention.

[0038] Reference Numerals: 1 - Feed Air Compressor; 2 - Air Cooler; 3 - Refrigerated Dryer; 4 - Adsorption Dryer; 5 - Circulation Booster; 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 - Sub - cooled Booster Turbine Expander; 12 - Sub - cooled Booster Cooler; 13 - Hot - end Heat Exchanger; 14 - Cold - end Heat Exchanger; 15 - Liquid Expander; 16 - Sub - cooler; 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 - Adsorber Air Inlet; 42 - Adsorber Air Outlet; 43 - Adsorber Regenerated Gas Inlet; 44 - Adsorber Regenerated Gas Outlet; 51 - Circulation Booster Inlet; 52 - Circulation Booster Outlet; 61 - Circulation Booster Air Inlet; 62 - Circulation Booster Air Outlet; 63 - Cooling Water Inlet; 64 - Cooling Water Outlet; 71 - Cold - end Booster Compressor Air Inlet; 72 - Cold - end Booster Compressor 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 Compressor Air Inlet; 92 - Hot - end Booster Compressor 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 - Sub - cooled Booster Compressor Air Inlet; 112 - Sub - cooled Booster Compressor Air Outlet; 113 - Sub - cooled Expander Air Inlet; 114 - Sub - cooled Expander Air Outlet; 121 - Sub - cooled Booster Cooling Air Inlet; 122 - Sub - cooled Booster Cooling Air Outlet; 103 - Cooling Water Inlet; 104 - Cooling Water Outlet; 131 - Hot - end Heat Exchange First Inlet; 132 - Hot - end Heat Exchange First Outlet; 133 - Hot - end Heat Exchange Second Inlet; 134 - Hot - end Heat Exchange Second Outlet; 135 - Hot - end Heat Exchange Third Outlet; 136 - Hot - end Heat Exchange Third Inlet; 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 - Sub - cooling First Inlet; 162 - Sub - cooling First Outlet; 163 - Sub - cooling Second Outlet; 164 - Sub - cooling Second Inlet; 171 - Storage Tank Inlet. Detailed Embodiments

[0039] The following describes the embodiments of the present invention through specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the drawings provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0040] Among them, the drawings are only for illustrative purposes, showing only schematic diagrams, not physical diagrams, and should not be construed as a limitation on the present invention; in order to better illustrate the embodiments of the present invention, some components in the drawings will be omitted, enlarged or reduced, which does 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 may be omitted.

[0041] In the drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", "front", "rear", etc. indicating the orientation or positional relationship, they are based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the terms describing the positional relationship in the drawings are only for illustrative purposes and should not be construed as a limitation on the present invention. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0042] Please refer to Figure 1 , which is a production device for liquid air, including a raw air compression system, an air cooling and drying system, a circulation pressurization system, an expansion refrigeration system, a heat exchange cold box, and a liquid air storage tank 17;

[0043] The raw air compression system includes a feed air compressor 1 and an air cooler 2; the air cooling and drying system includes a cold dryer 3 and an adsorption dryer 4; the circulation pressurization system includes a circulation booster 5 and a booster cooler 6; the air cooler 2 is provided 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 provided with two sets of inlets and outlets, namely a dryer air inlet 41, a dryer air outlet 42, a dryer regeneration gas inlet 43, and a dryer regeneration gas outlet 44. The booster cooler 6 is provided with a circulation pressurized air inlet 61, a circulation pressurized air outlet 62, a cooling water inlet 63, and a cooling water outlet 64.

[0044] 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 subcooling booster turbine expander 11, and a subcooling booster cooler 12; a liquid expander 15; the cold-end booster turbine expander 7 is provided with two sets of inlets and outlets, namely a cold-end booster air inlet 71 and a cold-end booster air outlet 72, a cold-end expander air inlet 73 and a cold-end expander air outlet 74; the cold-end booster cooler 8 is provided with two sets 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; the hot-end booster turbine expander 9 is provided with two sets of inlets and outlets, namely a hot-end booster air inlet 91 and a hot-end booster air outlet 92, a hot-end expander air inlet 93 and a hot-end expander air outlet 94; the hot-end booster cooler 10 is provided with two sets 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 subcooling booster turbine expander 11 is provided with two sets of inlets and outlets, namely a subcooling booster air inlet 111 and a subcooling booster air outlet 112, a subcooling expander air inlet 113 and a subcooling expander air outlet 114; the subcooling booster cooler 12 is provided with two sets of inlets and outlets, namely a subcooling booster cooling air inlet 121, a subcooling booster cooling air outlet 122, a cooling water inlet 123, and a cooling water outlet 124; the liquid expander 15 is provided with a set of inlets and outlets, namely a liquid expander liquid air inlet 151 and a liquid expander liquid air outlet 152; at the same time, the liquid expander 15 is braked by a generator 153.

[0045] 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 is provided with four sets of inlets and outlets, namely a hot-end heat exchange first inlet 131 and a hot-end heat exchange first outlet 132, a hot-end heat exchange second inlet 133 and a hot-end heat exchange second outlet 134, a hot-end heat exchange third inlet 136 and a hot-end heat exchange third outlet 135, a hot-end heat exchange fourth inlet 138 and a hot-end heat exchange fourth outlet 137; the cold-end heat exchanger 14 is provided with four sets of inlets and outlets, namely a cold-end heat exchange first inlet 141 and a cold-end heat exchange first outlet 142, a cold-end heat exchange second inlet 144 and a cold-end heat exchange second outlet 143, a cold-end heat exchange third inlet 146 and a cold-end heat exchange third outlet 145, a cold-end heat exchange fourth inlet 148 and a cold-end heat exchange fourth outlet 147; the subcooler 16 is provided with two sets of inlets and outlets, namely a subcooling first inlet 161 and a subcooling first outlet 162, a subcooling second inlet 164 and a subcooling second outlet 163; the liquid air storage tank 17 is provided with a storage tank inlet 171.

[0046] The feed air compressor 1, air cooler 2, refrigerated dryer 3, adsorption dryer 4, circulating booster 5, and booster cooler 6 are connected in series in sequence, that is, the feed air compressor inlet 1001, feed air compressor outlet 1002, air inlet 21, air outlet 22, refrigerated dryer inlet 31, refrigerated dryer outlet 32, dryer air inlet 41, 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 in sequence; the circulating booster air outlet 62 of the booster cooler 6 is divided into two paths:

[0047] One path is connected to the subcooled booster air inlet 111. The subcooled booster air outlet 112 is connected to the first inlet 131 of the hot-end heat exchanger after passing through the subcooled booster cooler 12. The first outlet 132 of the hot-end heat exchanger is connected to the hot-end expander air inlet 93. The hot-end expander air outlet 94 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 booster inlet 51;

[0048] The other path is connected to the cold-end booster air inlet 71. The cold-end booster air outlet 72 is connected to the hot-end booster air inlet 91 after passing through the cold-end booster cooler 8. The hot-end booster air outlet 92 is connected to the second inlet 133 of the hot-end heat exchanger after passing through the hot-end booster cooler 10. The second outlet 134 of the hot-end heat exchanger is divided into two paths. One path is connected to the cold-end expander air inlet 73, and the other path is connected to the first inlet 141 of the cold-end heat exchanger; the cold-end expander air outlet 74 is also divided into two paths. One path is connected to the second inlet 144 of the cold-end heat exchanger, and the other path is connected to the third inlet 146 of the cold-end heat exchanger. The second outlet 143 of the cold-end heat exchanger converges with the hot-end expander air outlet 94 and then is connected to the third inlet 136 of the hot-end heat exchanger. The third outlet 145 of the cold-end heat exchanger is connected to the subcooled expander air inlet 113. The subcooled expander air outlet 114 is connected to the second inlet 164 of the subcooling. The second outlet 163 of the subcooling is connected to the fourth inlet 148 of the cold-end heat exchanger. The fourth outlet 147 of the cold-end heat exchanger is connected to the fourth inlet 138 of the hot-end heat exchanger. The fourth outlet 137 of the hot-end heat exchanger is connected to the adsorption dryer 4 to provide desorption gas to the adsorption dryer;

[0049] The first outlet 142 of the cold-end heat exchanger is connected to the liquid inlet 151 of the liquid expander. The liquid outlet 152 of the liquid expander is connected to the first inlet 161 of the subcooling. The first outlet 162 of the subcooling is divided into two paths. One path is connected to the liquid air storage tank 17, and the other path converges with the subcooled expander air outlet 114 and then is connected to the second inlet 164 of the subcooling.

[0050] A liquid expander 15 is used instead of a throttle valve to reduce the pressure between the first outlet 142 of the cold-end heat exchanger and the first inlet 161 of the subcooling.

[0051] A throttle valve V2 is provided between the subcooled first outlet 162 and the liquid air storage tank 17, and a throttle valve V1 is provided between the subcooled first outlet 162 and the subcooled second inlet 164.

[0052] A storage tank inlet 171 is provided on the liquid air storage tank 17 and is communicated with the subcooled first outlet 162.

[0053] Among them, the feeding air compressor 1 uses a screw compressor, and the circulating booster 5 is a piston booster to adapt to frequent start and stop.

[0054] 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 a three-section series connection in the heat exchange cold box.

[0055] A method for producing liquid air uses the above-mentioned liquid air production device to produce liquid air. The specific implementation process is as follows:

[0056] Air is pressurized to 0.54 MPa(A) by the feeding air compressor 1 to obtain medium-pressure air, and enters the air cooler 2; the cooled medium-pressure air is further cooled to 10 °C by the cold dryer 3, and then the moisture and carbon dioxide are removed by the adsorption dryer 4; the dry and clean medium-pressure air enters the circulating booster 5 to be further pressurized to 3.0 MPa(A) to obtain high-pressure air, and then is divided into two paths:

[0057] One path enters the supercharging booster air inlet 111, the pressurized air is cooled by the supercharging booster cooler 12 and then enters the hot end heat exchange first inlet 131, is cooled in the hot end heat exchanger 13 and then is led out from the hot end heat exchange first outlet 132, and then enters the hot end expander air inlet 93, and after expansion refrigeration, is led out from the hot end expander air outlet 94, and the expanded medium-pressure air returns to the hot end heat exchange third inlet 136;

[0058] The other path enters the cold end booster air inlet 71, the pressurized air is cooled by the cold end booster cooler 8 and then enters the hot end booster air inlet 91, is further pressurized to 6.22 MPa(A) and then is led out from the hot end booster air outlet 92, is cooled by the hot end booster cooler 10 and then enters the hot end heat exchange second inlet 133, is cooled and then is led out from the hot end heat exchange second outlet 134, and then is divided into two paths again:

[0059] One way enters the cold-end expander air inlet 73, and after expansion refrigeration, it is led out from the cold-end expander air outlet 74. The led-out air is again divided into two paths. One path enters the second cold-end heat exchange inlet 144. After heat exchange, the air converges with the air led out from the hot-end expander air outlet 94, and then they enter the third hot-end heat exchange inlet 136 together. After being reheated to normal temperature in the heat exchanger, they return to the circulating booster inlet 51. The other path enters the third cold-end heat exchange inlet 146, and after heat exchange, it is led out from the third cold-end heat exchange outlet 145, then enters the subcooling expander air inlet 113. The air after expansion refrigeration is led out from the subcooling expander air outlet 114, and the led-out air enters the second subcooling inlet 164. Another path enters the first cold-end heat exchange inlet 141. The air is cooled down after heat exchange and becomes high-pressure liquid air, which is led out from the first cold-end heat exchange outlet 142, then enters the liquid expander liquid air inlet 151. The medium-pressure liquid air after being cooled down and depressurized by the liquid expander is led out from the liquid expander liquid air outlet 152 and enters the first subcooling inlet 161. Part of the liquid air after being subcooled by the subcooler 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. Another part is throttled to 0.13 MPa(A) by the throttle valve V2, then converges with the subcooling expander air outlet 114, returns to the second subcooling inlet 164, is vaporized and reheated, and is led out from the second subcooling outlet 163, then enters the fourth cold-end heat exchange inlet 148, is reheated and led out from the fourth cold-end heat exchange outlet 147, then enters the fourth hot-end heat exchange inlet 138, and continues to be reheated to normal temperature and led out from the fourth hot-end heat exchange outlet 137 to the adsorption dryer 4, and is discharged to the atmosphere after desorption.

[0060] In this embodiment, the circulating booster 5 is started by frequency conversion to reduce the impact on the power grid during startup. The liquid air production device operates during the low electricity price period of electricity consumption and stops during the high electricity price period of electricity consumption.

[0061] The raw material air adopted in this embodiment: 37300 Nm 3 / h, 0.098 MPa(A). The obtained product liquid air: 26700 Nm 3 / h (converted to gaseous state).

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not restrictive. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the purpose and scope of the present technical solution, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A liquid air production device, characterized in that: Including raw air compression system, air cooling, drying and purification system, circulating pressurization system, expansion refrigeration system, heat exchange cold box, liquid air storage tank; The raw air compression system includes a feed air compressor and an air cooler; the air cooling, drying and purification system includes a cold dryer and an adsorption dryer; the circulating pressurization system includes a circulating supercharger and a supercharger cooler; The expansion refrigeration system includes a cold-end booster turbine expander, a cold-end booster cooler, a hot-end booster turbine expander, a hot-end booster cooler, a subcooled booster turbine expander, and a liquid expander; the cold-end booster turbine expander is provided with two groups of inlets and outlets, namely, the cold-end booster air inlet and the cold-end booster air outlet, and the cold-end expander air inlet and the cold-end expander air outlet; the hot-end booster turbine expander is provided with two groups of inlets and outlets, namely, the hot-end booster air inlet and the hot-end booster air outlet, and the hot-end expander air inlet and the hot-end expander air outlet; the subcooled booster turbine expander is provided with two groups of inlets and outlets, namely, the subcooled booster air inlet and the subcooled booster air outlet, and the subcooled expander air inlet and the subcooled expander air outlet; the liquid expander is provided with a group of inlets and outlets, namely, the liquid air inlet of the liquid expander and the liquid air outlet of the liquid expander; The heat exchange cold box includes a hot-end heat exchanger, a cold-end heat exchanger, and a subcooler; the hot-end heat exchanger is provided with four groups of inlets and outlets, namely, a first inlet and a first outlet of the hot-end heat exchange, a second inlet and a second outlet of the hot-end heat exchange, a third inlet and a third outlet of the hot-end heat exchange, and a fourth inlet and a fourth outlet of the hot-end heat exchange; the cold-end heat exchanger is provided with four groups of inlets and outlets, namely, a first inlet and a first outlet of the cold-end heat exchange, a second inlet and a second outlet of the cold-end heat exchange, a third inlet and a third outlet of the cold-end heat exchange, and a fourth inlet and a fourth outlet of the cold-end heat exchange; the subcooler is provided with two groups of inlets and outlets, namely, a first subcooling inlet and a first subcooling outlet, and a second subcooling inlet and a second subcooling outlet; The air-feeding air compressor, air cooler, cold dryer, adsorption dryer, circulating supercharger, and supercharge cooler are connected in series in sequence, and the outlet of the supercharge cooler is divided into two routes: One path is connected to the air inlet of the supercooling compressor, the air outlet of the supercooling compressor is connected to the first inlet of the hot end heat exchange after passing through the cold boost cooler, the first outlet of the hot end heat exchange 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 exchange, and the third outlet of the hot end heat exchange is connected to the inlet of the circulating compressor; The other route is connected to the cold end booster air inlet, and the cold end booster air outlet is connected to the hot end booster air inlet after passing through the cold end booster cooler, and the hot end booster air outlet is connected to the hot end heat exchange second inlet after passing through the hot end booster cooler, and the hot end heat exchange second outlet is divided into two routes, one route is connected to the cold end expander air inlet, and the other route is connected to the cold end heat exchange first inlet; the cold end expander air outlet is divided into two routes, one route is connected to the cold end heat exchange second inlet, and the other route is connected to the cold end heat exchange third inlet, the cold end heat exchange second outlet merges with the hot end expander air outlet and is connected to the hot end heat exchange third inlet, the cold end heat exchange third outlet is connected to the subcooled expander air inlet, the subcooled expander air outlet is connected to the subcooled second inlet, the subcooled second outlet is connected to the cold end heat exchange fourth inlet, the cold end heat exchange fourth outlet is connected to the hot end heat exchange fourth inlet, and the hot end heat exchange fourth outlet is connected to the adsorption dryer to provide analytical gas to the adsorption dryer; The first outlet of the cold end heat exchange is connected to the liquid-to-air inlet of the liquid expander, the liquid-to-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-to-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 device according to claim 1, characterized in that: A throttle valve is arranged between the first supercooling outlet and the liquid air storage tank, and between the first supercooling outlet and the second supercooling inlet.

3. The liquid air production device according to claim 1, characterized in that: The liquid-air storage tank is provided with a storage tank vapor outlet, and the liquid-air vapor outlet is communicated with the third inlet of the cold end heat exchange.

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

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

6. A method for producing liquid air, characterized in that: Using the liquid air production device as described in any one of claims 1 to 5 to produce liquid air; The air is pressurized by the air-feeding air compressor to obtain medium-pressure air, which then enters the air cooler; The cooled medium-pressure air is further cooled by the cold dryer, and then the moisture and carbon dioxide are removed by the adsorption dryer; the dry and clean medium-pressure air enters the circulating booster for further pressurization to obtain high-pressure air, and then is divided into two routes: The air enters the air inlet of the supercooling compressor all the way, and the supercharged air enters the first heat exchange inlet of the hot end after being cooled by the supercharger cooler. After being cooled in the heat exchanger, it is led out from the first heat exchange outlet of the hot end, and then enters the air inlet of the hot end expander. After expansion and refrigeration, it is led out from the hot end expansion air outlet. The expanded medium-pressure air returns to the third heat exchange inlet of the hot end. The other route enters the cold end booster air inlet. The boosted air is cooled by the cold end booster cooler and then enters the hot end booster air inlet. It is boosted again and then led out from the hot end booster air outlet. It enters the hot end heat exchange second inlet after being cooled by the hot end booster cooler. It is then led out from the hot end heat exchange second outlet and then divided into two routes: One path enters the air inlet of the cold end expander, and the medium-pressure air obtained after expansion and refrigeration is led out from the air outlet of the cold end expander. The led-out medium-pressure air is divided into two paths again. One path enters the second inlet of the cold end heat exchanger. After the medium-pressure air after heat exchange merges with the medium-pressure air led out from the air outlet of the hot end expander, they enter the third inlet of the hot end heat exchanger together, are reheated to room temperature by the heat exchanger, and then return to the circulating boost inlet; the other path enters the third inlet of the cold end heat exchanger, is led out from the third outlet of the cold end heat exchanger after heat exchange, and then enters the air inlet of the subcooling expander. The low-pressure air after expansion and refrigeration is led out from the air outlet of the subcooling expander, and the led-out air enters the second inlet of the subcooling; The other route enters the first inlet of the cold end heat exchanger. After heat exchange and cooling, the air becomes high-pressure liquid air and is led out from the first outlet of the cold end heat exchanger, and then enters the liquid air inlet of the liquid expander. The medium-pressure liquid air after cooling and depressurization by the liquid expander is led out from the liquid air outlet of the liquid expander and enters the first inlet of the subcooling. After being supercooled by the cooler, part of the liquid air is throttled to normal pressure and sent to the liquid air storage tank as a liquid air product, and the other part is throttled to normal pressure and merged with the air outlet of the subcooling expander, and then returns to the second inlet of the subcooling, is vaporized and reheated, and is led out from the second outlet of the subcooling, and then enters the fourth inlet of the cold end heat exchanger, and is led out from the fourth outlet of the cold end heat exchanger after reheating, and then enters the fourth inlet of the hot end heat exchanger, and continues to be reheated to normal temperature and is led out from the fourth outlet of the hot end heat exchanger to the adsorption dryer, and is discharged into the atmosphere after analysis.

7. The method for producing liquid air according to claim 6, characterized in that: The high-pressure air pressure obtained by the circulation booster is 2.8~3.2MPa, and then it is boosted to 6.0~6.4MPa by the cold-end expansion booster and the hot-end expansion booster.

8. The method for producing liquid air according to claim 6, characterized in that: The pressure is increased to 3.3-3.5MPa by a cold expansion booster.

9. The method for producing liquid air according to claim 6, characterized in that: The atmospheric pressure air expanded by the subcooling expander merges with the atmospheric pressure liquid air after throttling and passes through the cooler, cold end heat exchanger, and hot end heat exchanger. The gasified and reheated air is used as the analytical gas of the adsorption dryer.

10. The method for producing liquid air according to claim 6, characterized in that: The circulating booster adopts variable frequency starting to reduce the impact of starting on the power grid; the liquid air production equipment operates during the period of low electricity prices and stops during the period of high electricity prices.

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