Combined heat and power generation full-liquid air separation system and process

Abstract

The invention discloses a combined heat and power generation full-liquid air separation system and process, and relates to the technical field of air separation, and the air separation system comprises an air filtering unit, a steam-electricity double-drive compression unit, a precooling and purifying unit, a multi-stage supercharging unit, a main heat exchanger and a rectification system which are connected in sequence; wherein the steam-electricity double-drive compression unit provides initial pressure for the subsequent multi-stage supercharging unit and is arranged outside an air boundary area; and the multi-stage supercharging unit comprises supercharging ends of at least two expansion machines and is used for carrying out stage-by-stage supercharging on the purified air. By adopting a system architecture combining out-of-boundary single steam-electricity double-drive medium-pressure gas supply and in-boundary multi-stage expansion pressurization refrigeration, an innovative air separation solution which has the advantages that the initial investment is remarkably reduced, the energy utilization efficiency is greatly improved, industrial waste heat resources can be flexibly adapted, and the operation reliability is high is provided; the core problems that a traditional full-liquid air separation system is high in investment and energy consumption and depends on high-quality electric power are solved.

Description

Technical Field

[0001] This invention relates to the field of air separation technology, and in particular to a combined heat and power all-liquid air separation system and process. Background Technology

[0002] Air separation (ESR) technology is a core means of industrially obtaining oxygen, nitrogen, argon, and their liquid products. In the field of all-liquid air separation, its products are highly favored due to their ease of storage and transportation. Traditional all-liquid air separation units generally adopt an electric-centric technical architecture. Under this architecture, air needs to undergo multi-stage compression by multiple large electric compressors (usually including feed air compressors, recirculating compressors, etc.) within the air separation zone until it reaches a high-pressure state. Then, it is processed into liquid products through subsequent cooling, expansion, liquefaction, and distillation processes.

[0003] This traditional "all-electric, multi-stage compression within the designated area" mode has several inherent defects, which severely restrict its economic efficiency and applicability for widespread adoption: First, the initial investment is extremely high. The area not only requires multiple high-pressure, high-power electric compressors, but also the construction of a complex high-voltage power distribution system, a large circulating cooling water station, and a lubrication system. The huge equipment procurement and infrastructure costs constitute a significant investment barrier for many projects.

[0004] Secondly, the operation consumes a huge amount of energy, resulting in high energy costs. The large electric compressor is the main energy-consuming equipment in the plant, accounting for a very high proportion of its energy consumption. Furthermore, the energy conversion path of "power generation-transmission-electric drive" suffers from multiple efficiency losses, resulting in low overall energy utilization efficiency.

[0005] Furthermore, the energy structure is singular and rigid. Complete reliance on grid power makes the operating costs of the equipment extremely sensitive to fluctuations in electricity prices, and it cannot effectively utilize the low-grade waste heat steam that is widely present in industrial enterprises but is often wasted (such as by-product steam from steel, chemical, and cogeneration plants), resulting in a mismatch and waste of energy quality.

[0006] In addition, traditional processes are complex, involve numerous devices, occupy a large area, and require heavy maintenance. Furthermore, the output ratio is usually fixed during the design phase, making it difficult to adjust flexibly according to market demand, thus limiting operational economics.

[0007] Therefore, there is an urgent need in this field for a new type of all-liquid air separation system that can fundamentally reconstruct the air separation power architecture, deeply integrate the utilization of low-grade heat sources, and thus achieve breakthroughs in both investment and energy consumption. Summary of the Invention

[0008] The purpose of this invention is to provide a combined heat and power all-liquid air separation system and process to solve the problems existing in the prior art, reconstruct the air separation power architecture, deeply integrate the utilization of low-grade heat sources, and achieve a dual breakthrough in investment and energy consumption.

[0009] To achieve the above objectives, the present invention provides the following solution: A combined heat and power (CHP) all-liquid air separation system, comprising: Air filter unit; A dual-drive (gas and electric) compression unit is used to receive and compress air from the air filter unit; A pre-cooling and purification unit is used to cool and purify the medium-pressure air from the gas-electric dual-drive compression unit; A multi-stage pressurization unit, whose air inlet is connected to the air outlet of the precooling and purification unit, is used to pressurize the purified air in stages. The multi-stage pressurization unit includes pressurization ends of at least two expanders. The inlet of the high-pressure channel of the main heat exchanger is connected to the high-pressure outlet of the multi-stage booster unit. A distillation system, the feed inlet of which is connected to the cryogenic liquid outlet of the main heat exchanger; The dual-drive compression unit provides initial pressure for the subsequent multi-stage booster units and is located outside the air separation zone.

[0010] In one exemplary embodiment, the dual-drive compression unit includes a compressor and a steam turbine and an electric motor connected thereto.

[0011] In an exemplary embodiment, the multi-stage booster unit includes the booster ends of a first expander, a second expander, and a third expander connected in series to form a three-stage booster circuit. The first expander is a low-pressure expander, the second expander is a high-temperature expander, and the third expander is a low-temperature expander. The outlet of the precooling and purification unit is connected to the inlet of the pressurization end of the low-pressure expander. The outlet of the pressurization end of the low-pressure expander is connected in sequence to the pressurization end of the high-temperature expander, the second cooler, the pressurization end of the low-temperature expander, the third cooler, the main heat exchanger, and the distillation system to form the main circuit after passing through the first cooler.

[0012] In an exemplary embodiment, the system further includes an expansion and refrigeration unit corresponding to the multi-stage pressurization unit; the expansion and refrigeration unit includes the expansion end of the low-temperature expander, the expansion end of the high-temperature expander, and the expansion end of the low-pressure expander.

[0013] In an exemplary embodiment, the airflow at the pressurization end outlet of the low-pressure expander is cooled by the first cooler and then divided into two streams: one stream enters the pressurization end of the high-temperature expander as the main pressurization airflow; the other stream enters the first branch as the first expansion airflow. After the first expansion gas flow is cooled by the main heat exchanger, it is drawn out from the top of the main heat exchanger and introduced into the expansion end of the high-temperature expander to expand and form the first expanded gas flow. The main pressurized airflow from the pressurized end outlet of the cryogenic expander, after being cooled in the main heat exchanger, is partially separated from it as the second expansion airflow, which is then introduced into the expansion end of the cryogenic expander via the second branch to expand and form the second expanded airflow. The second expanded gas flow is divided into two paths: one path enters the lower column of the distillation system directly through the third branch; the other path returns to the main heat exchanger for reheating through the fourth branch, forming a reheated gas flow. After the first expanded gas flow merges with the reheated gas flow of the fourth branch, they enter the expansion end of the low-pressure expander for expansion. The expanded exhaust gas returns to the main heat exchanger to provide cooling, and is finally output as the regeneration gas source of the precooling and purification unit.

[0014] In an exemplary embodiment, a fifth branch is provided before the first branch enters the main heat exchanger. A low-temperature refrigerator is provided on the fifth branch. The pressurized air entering the fifth branch is cooled by the low-temperature refrigerator and then enters the expansion end of the high-temperature expander to expand to a low pressure.

[0015] In one exemplary embodiment, the system further includes a liquid expander; the inlet of the liquid expander is connected to the high-pressure liquid air outlet of the main heat exchanger via a pipe, and its outlet is connected to the lower column feed inlet of the distillation system.

[0016] In one exemplary embodiment, the liquid expander is a liquid turbine with power generation function, used to recover the pressure energy of high-pressure liquid air and generate electricity.

[0017] In one exemplary embodiment, the system further includes a water cooling tower, through which low-pressure exhaust gas from the main heat exchanger after reheating and / or exhaust gas from the expansion end of the low-pressure expander are partially or entirely introduced for the preparation of chilled water.

[0018] This invention also provides a combined heat and power (CHP) all-liquid air separation process, using the above-mentioned CHP all-liquid air separation system, comprising the following steps: The air filtration process removes dust from the ambient air. The compression process of the dual-drive electric system is as follows: the filtered air is compressed to medium pressure, cooled, and then delivered to the air separation zone; Pre-cooling and purification steps: The medium-pressure air is pre-cooled and purified by adsorption to remove moisture and carbon dioxide impurities; Multi-stage pressurization step: The purified air is introduced into a multi-stage pressurization unit consisting of at least two expander pressurization ends connected in series for continuous pressurization; Heat exchange and liquefaction steps: High-pressure air obtained through multi-stage pressurization is introduced into the main heat exchanger for cooling, and some of the air is liquefied in it; Distillation separation step: The liquefied air and part of the expanded air in the main heat exchanger are sent to the distillation system for separation to obtain liquid oxygen, nitrogen and argon products.

[0019] The present invention achieves the following technical effects compared to the prior art: By adopting a novel system architecture that combines "external single-unit steam-electric dual-drive medium-pressure gas supply" with "internal multi-stage expansion and pressurization refrigeration," the core pain points of traditional all-liquid air separation systems—high investment, high energy consumption, and reliance on high-quality electricity—are fundamentally solved. This provides an innovative air separation solution that significantly reduces initial investment, greatly improves energy utilization efficiency, can flexibly adapt to industrial waste heat resources, and has high operational reliability, demonstrating outstanding economic benefits and broad industrial application prospects.

[0020] Other technical solutions disclosed in this invention also have the following technical advantages: By precisely extracting air from different temperature levels of the main heat exchanger (first and second branches) to drive the corresponding expanders (K-103 and K-101), the "temperature-matched, on-demand production" of cooling capacity is achieved, greatly reducing the waste of heat exchange process and significantly improving the system's thermal efficiency.

[0021] The expanded gas flow is used for distillation feed (third branch) and confluenced to drive final stage expansion (third branch), and finally the dried exhaust gas is used as regeneration gas, forming an internal closed loop of materials and energy, which provides cooling while completing raw material supply and system self-regeneration. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the structure of a combined heat and power all-liquid air separation system disclosed in a specific embodiment of the present invention; Figure 2 for Figure 1 A schematic diagram of the structure after omitting the distillation system; The components include: 1. Air filtration unit; 2. Gas-electric dual-drive compression unit; 3. Pre-cooling and purification unit; 4. Low-temperature refrigerator; 5. Low-pressure expander; 6. High-temperature expander; 7. Low-temperature expander; 8. Liquid expander; 9. Main heat exchanger; 10. Distillation system; 11. First cooler; 12. Second cooler; 13. Third cooler; 14. First branch; 15. Second branch; 16. Third branch; 17. Fourth branch; 18. Fifth branch; K-101, Expansion end of the low-temperature expander; K-102, Pressurization end of the low-temperature expander; K-103, Expansion end of the high-temperature expander; K-104, Pressurization end of the high-temperature expander; K-105, Pressurization end of the low-pressure expander; K-106, Expansion end of the low-pressure expander. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] The purpose of this invention is to provide a combined heat and power all-liquid air separation system and process to solve the problems existing in the prior art, reconstruct the air separation power architecture, deeply integrate the utilization of low-grade heat sources, and achieve a dual breakthrough in investment and energy consumption.

[0026] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0027] Example 1 Please refer to Figure 1 and Figure 2 This embodiment provides a combined heat and power all-liquid air separation system, including: Air filter unit 1 is used for cleaning and filtering air; The dual-drive compression unit 2 is used to receive air from the air filter unit 1, compress it to 25~40 bar, and cool it to 40°C. The pre-cooling and purification unit 3, in which the medium-pressure pre-cooling system further cools the medium-pressure air from the steam-electric dual-drive compression unit 2 to 10~15℃, and then the medium-pressure purification system in the pre-cooling and purification unit 3 purifies it to remove impurities such as water and CO2. The multi-stage pressurization unit has its air inlet connected to the air outlet of the pre-cooling and purification unit 3, and is used to pressurize the purified air in stages. The multi-stage pressurization unit includes the pressurization ends of at least two expanders. The inlet of the high-pressure channel of the main heat exchanger 9 is connected to the high-pressure outlet of the multi-stage pressurization unit. The distillation system 10 has its feed inlet connected to the cryogenic liquid outlet of the main heat exchanger 9; Among them, the dual-drive compression unit 2 provides initial pressure for the subsequent multi-stage supercharging unit and is located outside the air separation zone.

[0028] Specifically, the dual-drive compressor unit 2 includes a compressor and a steam turbine and an electric motor connected to it.

[0029] This embodiment uniquely integrates the initial compression function of the entire system into a dual-drive steam-electric compression unit 2 located outside the air separation boundary area. This unit compresses the air to medium pressure (e.g., 25-40 bar) in a single operation, providing initial pressure for subsequent processes. This completely eliminates the need for all traditionally required large electric feed compressors, circulating compressors, and their associated expensive high-voltage power distribution systems, large circulating cooling water stations, and complex lubrication systems in the complex main air separation unit (within the boundary area). According to engineering estimates, this structural change alone can reduce equipment investment, civil engineering, and installation costs within the air separation boundary area by approximately 40%-50%, significantly lowering the initial investment threshold and shortening the construction period.

[0030] The steam-electric dual-drive compression unit 2 in this embodiment can preferentially utilize low-pressure waste heat steam, which is extremely low-cost or abundant in industries such as steel, chemical, and combined heat and power plants, as power. This not only directly replaces expensive electricity consumption, but more importantly, it bypasses the path of "heat energy → power generation → power transmission → electric drive," which involves multiple conversion losses, thus improving efficiency from the source of energy conversion. Compared with pure electric drive, the energy utilization efficiency of the steam direct drive mode can be improved by 10%-25%. When the steam supply fluctuates or is interrupted, it can seamlessly switch to electric drive, ensuring the continuity and safety of production. Therefore, this system can be perfectly integrated into industrial ecosystems with steam resources, achieving tiered and efficient utilization of energy.

[0031] Furthermore, the elimination of all large, high-speed rotating compressor units within the air separation zone greatly simplifies the equipment composition of the entire main unit area. This directly results in: a more compact equipment layout and reduced floor space; a significant reduction in vibration and noise sources, improving the operating environment; and a substantial reduction in maintenance points and workload, with maintenance of the main rotating equipment concentrated in a single steam-electric dual-drive unit outside the boundary, enhancing the maintainability and operational reliability of the unit.

[0032] This embodiment employs a multi-stage pressurization unit consisting of the pressurization ends of at least two expanders. Utilizing the expanders' own compression capabilities, it relays the pressurization of medium-pressure air from outside the system, thereby meeting the high-pressure conditions required for distillation. This replaces the electric circulating compressor located within the boundary area in traditional processes. This not only avoids the power consumption of adding an independent compressor, but also allows for deep thermodynamic coupling between this multi-stage pressurization process and the subsequent expansion-refrigeration process (through the expansion end). The heat generated by pressurization is effectively removed by the intercooler, while the expansion process uses the cooled air to provide the required cooling capacity at each stage, achieving coordinated production and internal circulation of pressure energy and cooling capacity. This optimizes the thermodynamic efficiency of the entire air separation unit and further reduces the overall operating energy consumption of the system.

[0033] Specifically, the multi-stage pressurization unit includes the pressurization ends of the first expander, the second expander, and the third expander connected in series, forming a three-stage pressurization circuit. Through three-stage continuous pressurization, medium-pressure air can be more precisely and smoothly boosted to the high pressure required by the process. The pressurization ratio of each stage is more reasonable, the compression efficiency is higher, and the generated heat of compression is more easily removed by the intercooler. This provides a high-pressure air source with better temperature and pressure matching for subsequent processes, laying a more optimized thermodynamic foundation for the energy cascade utilization of the entire system.

[0034] Among them, the first expander is a low-pressure expander 5, the second expander is a high-temperature expander 6, and the third expander is a low-temperature expander 7.

[0035] The outlet of the precooling and purification unit 3 is connected to the inlet of the booster end K-105 of the low-pressure expander. The outlet of the booster end K-105 of the low-pressure expander is connected to the booster end K-104 of the high-temperature expander, the second cooler 12, the booster end K-102 of the low-temperature expander, the third cooler 13, the main heat exchanger 9, and the distillation system 10 in sequence after passing through the first cooler 11 to form the main circuit.

[0036] Main path: Purified air → K-105 (low-pressure boost) → First cooler → K-104 (high-temperature boost) → Second cooler → K-102 (low-temperature boost) → Third cooler → Main heat exchanger → Distillation system.

[0037] The aforementioned main path forms the basis for high-pressure construction. Purified medium-pressure air (e.g., 30 bar) sequentially passes through the booster end of a three-stage expander, with the pressure progressively increased (e.g., to 65 bar) to the high pressure required for distillation. After each boost, the heat of compression is removed by a cooler to ensure the efficiency of the next boost and the lowest possible gas temperature entering the main heat exchanger. This path replaces the independent high-pressure circulating compressor in traditional processes, utilizing the expander's own compression function for boosting, resulting in a more direct energy conversion path. Furthermore, it provides the gas source for subsequent cooling and liquefaction in the main heat exchanger, ultimately yielding high-pressure liquid air (which proceeds to the liquid expander and the lower column).

[0038] This embodiment also includes an expansion and refrigeration unit corresponding to the multi-stage pressurization unit; the expansion and refrigeration unit includes the expansion end K-101 of the low-temperature expander, the expansion end K-103 of the high-temperature expander, and the expansion end K-106 of the low-pressure expander.

[0039] The airflow from the pressurization end K-105 outlet of the low-pressure expander is cooled by the first cooler 11 and then divided into two streams: one stream enters the main pipeline as the main pressurization airflow; the other stream enters the first branch pipeline 14 as the first expansion airflow. After being cooled by the main heat exchanger 9, the first expansion airflow is drawn out from its upper part and introduced into the expansion end K-103 of the high-temperature expander for expansion, forming the first expanded airflow.

[0040] The first branch, path 14: diverts from outlet K-105 (medium pressure, normal temperature) → enters the main heat exchanger for initial cooling → is drawn out from the upper part of the main heat exchanger (relatively high temperature, such as 10-20℃) → enters K-103 (high temperature expansion end) for expansion to low pressure.

[0041] This portion of the gas has a moderate pressure and is pre-cooled to an intermediate temperature by the reflux cold gas in the main heat exchanger 9. Expansion at this temperature results in a large absolute temperature drop, generating significant intermediate-temperature cooling.

[0042] The cryogenic gas after expansion in K-103 will return to the main heat exchanger 9 for reheating, providing the necessary cold source for the middle heat exchange section of the main heat exchanger 9 to cool the high-pressure air and other airflows in the main path. By using air that has not yet entered cryogenic conditions to produce intermediate-temperature cooling, the "energy quality waste" of using a lower-temperature air source for intermediate-temperature cooling is avoided.

[0043] The main pressurized gas flow from the main pipeline, after being cooled in the main heat exchanger 9, has a portion of it separated as the second expansion gas flow. This second expansion gas flow is introduced into the expansion end K-101 of the cryogenic expander via the second branch 15, forming the second expanded gas flow. The second expanded gas flow is divided into two paths: one path enters the lower column of the distillation system 10 directly via the third branch 16; the other path returns to the main heat exchanger 9 via the fourth branch 17 for reheating, forming the reheated gas flow.

[0044] The second branch 15 path: High-pressure air entering the main heat exchanger 9 from the main line → is extracted by the second branch 15 in the middle of the main heat exchanger 9 (the temperature is very low, such as -120℃) → and enters K-101 (low temperature expansion end) for expansion.

[0045] This part consists of highly compressed air that has undergone deep cooling. The high pressure differential expands at low temperatures, resulting in a significant temperature drop and cooling capacity, which is the primary source of low-temperature cooling for the system.

[0046] After the second expansion in the third branch 16, the gas flow enters the lower column to participate in distillation. The coldest portion of the air after expansion in the second branch 15 directly enters the lower column of the distillation column, achieving a perfect combination of "refrigeration" and "distillation feedstock supply." This gas is both one of the largest contributors to the system's cooling capacity and the rising vapor necessary for distillation separation in the lower column.

[0047] After the second expansion of the gas entering the fourth branch 17, the gas returns to the main heat exchanger 9 for reheating and is then drawn from the lower part of the main heat exchanger 9 to the expansion end K-106 of the low-pressure expander for further expansion. Another portion of the gas after expansion in the second branch 15 returns to the main heat exchanger for reheating. This serves two purposes: first, to recover its remaining cooling capacity; and second, to act as a low-temperature, low-pressure gas stream, merging with the gas stream from the first branch 14 to provide a suitable gas source for driving K-106 (the low-pressure expansion end).

[0048] After the first expanded airflow from the first branch 14 and the reheated airflow from the fourth branch 17 merge, they enter the expansion end K-106 of the low-pressure expander for expansion. The expanded exhaust gas returns to the main heat exchanger 9 to provide cooling, and is finally output as the regeneration gas source for the pre-cooling and purification unit 3.

[0049] After the first and fourth branches merge, the gas enters K-106 (low-pressure expansion end) to complete the final expansion and waste gas utilization. This is the "waste gas energy recovery station" of the system's cooling chain. The two low-temperature, low-pressure gas streams that have already undergone one expansion are combined for a final expansion, extracting their remaining work and cooling capacity. The gas temperature after expansion at K-106 (low-pressure expansion end) is extremely low. It returns to the "hottest end" of the main heat exchanger 9 for reheating, providing a strong initial cooling capacity to the upper heat exchange section of the main heat exchanger 9 (which handles the newly entered room-temperature gas). Finally, after multiple cooling, expansion, and reheating processes, this gas reaches a suitable temperature and is extremely dry (moisture and CO2 have been removed during purification). It is the ideal regeneration gas source for the molecular sieve purification system, capable of efficiently desorbing moisture and CO2 from the adsorbent.

[0050] The above-mentioned branch system configuration achieves the following synergistic effects: 1. Precise matching and tiered supply of cooling capacity: By precisely extracting air at different temperature points such as the upper and middle parts of the main heat exchanger 9, and driving different expanders, the system can produce cooling capacity at different temperature levels from high to low as needed, and accurately distribute it to the corresponding airflow that needs to be cooled, which greatly reduces the temperature difference (irreversible loss) in the heat exchange process and has extremely high thermodynamic efficiency.

[0051] 2. Closed-loop transfer and conversion of pressure energy: The pressure energy of air (from the external compressor) is gradually increased at the pressurization end of the main circuit, and then gradually released and converted into cooling energy at the expansion ends of each branch circuit. Pressurization and expansion occur in pairs on each stage of the expander, forming a highly efficient internal circulation.

[0052] 3. Functional integration and zero material waste: Each airflow is fully utilized, with part becoming product, part providing cooling, and the last dry, low-temperature exhaust gas used as regeneration gas. There are no "useless" emissions within the system, maximizing material and energy utilization.

[0053] 4. System self-balancing and simplification: Through this internal circulation design, the system's demand for external cooling capacity is minimized, eliminating the need for large external ammonia or Freon refrigeration units, thus simplifying the process and making the operation more stable.

[0054] The aforementioned piping setup is key to achieving ultra-low energy consumption in this embodiment. Through sophisticated airflow organization and equipment coupling, it upgrades the traditional linear process of "compression-cooling-throttling-distillation" into a multi-loop, multi-level, deeply coupled "energy-matter synergistic conversion network," thereby solving the two core problems of "efficient cooling" and "deep distillation" while achieving an unprecedented level of energy efficiency.

[0055] As a preferred embodiment, the first branch 14 is provided with a fifth branch 18 before entering the main heat exchanger 9. A low-temperature refrigerator 4 is provided on the fifth branch 18. The pressurized air entering the fifth branch 18 is cooled by the low-temperature refrigerator 4 and then enters the expansion end K-103 of the high-temperature expander to expand to low pressure.

[0056] By incorporating a cryogenic chiller 4, an optional and flexible auxiliary cooling capacity supply module is added, significantly enhancing the system's ability to respond to load changes and production adjustments. When the ambient temperature is too high, when liquid products need to be produced at above-design load, or when the cooling capacity provided by the main expansion refrigeration system is slightly insufficient, the cryogenic chiller 4 can be activated to deeply pre-cool a portion of the airflow through the fifth branch 18, thereby increasing the cooling capacity of the gas entering the expander, or directly providing additional cooling capacity. This transforms the system from a fixed-condition device into an intelligent production unit with flexible capacity adjustment.

[0057] In this embodiment, a liquid expander 8 is also provided between the high-pressure liquid air outlet of the main heat exchanger 9 and the distillation system 10, and its outlet is connected to the lower column feed port.

[0058] In the traditional process, high-pressure liquid air is depressurized and enters the tower through a throttling valve, resulting in a complete waste of pressure energy. In this embodiment, the addition of a liquid expander 8 converts this pressure energy into mechanical energy, which can be directly used for power generation or to drive other equipment. This directly reduces the net power consumption of the system without consuming additional energy. At the same time, the temperature of the liquid air decreases further after expansion, increasing the subcooling of the liquid entering the tower, which is beneficial to improving the distillation separation efficiency.

[0059] Specifically, the liquid expander 8 is a liquid turbine with power generation function, used to recover the pressure energy of high-pressure liquid air and generate electricity, directly converting the recovered pressure energy into the most universal and easily utilized form of electrical energy. The generated electricity can be used for internal recycling within the device or connected to the grid for output, maximizing the value of energy recovery and further improving the overall energy efficiency and economic return of the system.

[0060] In addition, this embodiment also includes a water-cooled tower. Low-pressure exhaust gas from the main heat exchanger 9 after reheating and / or exhaust gas from the expansion end K-106 of the low-pressure expander are partially or completely fed into the water-cooled tower for the production of chilled water. The exhaust gas after reheating in the main heat exchanger 9 still possesses certain dryness and low-temperature characteristics. Through the water-cooled tower, low-temperature chilled water can be efficiently produced. This portion of chilled water is reused in the front-end air precooler and compressed air aftercooler, replacing or reducing the consumption of external circulating cooling water and the power consumption of the cooling tower fan. This forms a green operating mode with internal cooling self-circulation and reduced external water and power consumption, further reducing the operating costs of the device and its environmental impact.

[0061] Example 2 This embodiment provides a combined heat and power (CHP) all-liquid air separation process, using the CHP all-liquid air separation system described in Embodiment 1, including the following steps: The air filtration process removes dust from the ambient air. The compression process of the dual-drive electric system is as follows: the filtered air is compressed to medium pressure, cooled, and then delivered to the air separation zone; Pre-cooling and purification steps: The medium-pressure air is pre-cooled and purified by adsorption to remove moisture and carbon dioxide impurities; Multi-stage pressurization step: The purified air is introduced into a multi-stage pressurization unit consisting of at least two expander pressurization ends connected in series for continuous pressurization; Heat exchange and liquefaction steps: High-pressure air obtained through multi-stage pressurization steps is introduced into the main heat exchanger (9) for cooling, and some of the air is liquefied therein; Distillation separation step: The air liquefied in the main heat exchanger (9) and part of the expanded air are sent to the distillation system (10) for separation to obtain liquid oxygen, nitrogen and argon products.

[0062] This invention is suitable for application in industrial clusters where there is both a huge demand for air separation gas and a cost-effective steam source, for example: 1. Modern large-scale integrated iron and steel enterprise Demand matching: Steel smelting is one of the largest users of air separation gases (especially oxygen and nitrogen), and has a stable and large demand for liquid oxygen and liquid nitrogen.

[0063] Energy matching: Steel companies have abundant waste heat resources (such as sintering cooling, hot blast stove, converter, rolling and other processes that generate a large amount of medium and low pressure steam). This steam has extremely low cost and is perfect for driving the steam-electric dual-drive compressor of this invention.

[0064] Economic benefits: By utilizing their own waste heat, steel companies can build their own air separation units at extremely low operating costs, achieve gas self-sufficiency, get rid of dependence on purchased gas, and significantly reduce production costs.

[0065] 2. Petrochemical and Coal Chemical Industrial Park Demand matching: Chemical production requires large amounts of oxygen (for gasifiers), nitrogen (for purging, protection and syngas conditioning), and instrument air.

[0066] Energy matching: Chemical industrial parks are locations with the richest steam resources and the most complete steam networks. Production processes generate a large amount of byproduct steam, or there are centralized thermal power plants that can provide stable and cost-effective steam.

[0067] Economic benefits: Deeply integrating the air separation unit into the energy system of the chemical park to realize the cascade utilization of steam is a perfect practice for the chemical industry to pursue "maximum energy efficiency".

[0068] 3. Integrated large-scale power plants (especially combined heat and power plants) Demand Matching: The power plant itself requires a large amount of oxygen for environmental desulfurization and denitrification, and nitrogen for purging and protection. At the same time, the surrounding industrial area has a stable demand for air separation products.

[0069] Energy matching: This is the most direct scenario for "combined heat and power". Power plants can extract low-pressure steam that has done some work in the steam turbine to drive the air separation compressor, which creates additional value for air separation products with almost no sacrifice in the main power generation efficiency.

[0070] Economic benefits: By selling both electricity and air separation products as commodities, energy is fully utilized and benefits are diversified.

[0071] 4. Green Energy and Future Industries Combined with CCUS (Carbon Capture, Utilization, and Storage): The high-purity oxygen produced by the air separation unit is a key raw material for oxygen-enriched combustion carbon capture technology. The low-cost nature of this invention can significantly reduce the operating costs of CCUS.

[0072] Preparing for a Hydrogen Economy: Liquid nitrogen is an essential cryogenic medium for the liquefaction, storage, and transportation of hydrogen. This patent enables the economical production of large quantities of liquid nitrogen, serving future hydrogen energy infrastructure.

[0073] Waste-to-energy plants: Similar to power plants, they use steam to drive air separation, producing oxygen for combustion, thereby improving waste incineration efficiency and environmental performance.

[0074] In the description of this invention, it should be understood that the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are used only for the convenience of describing the invention, and do not imply or require that the device or element referred to must have a specific orientation or construction method, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," and "third," etc., are only used to distinguish the objects of description and should not be construed as limiting importance or order, and the features defined by such terms may explicitly or implicitly include one or more of those features. Unless otherwise stated, "a plurality of" in the description of this invention refers to two or more.

[0075] The terms "installation," "connection," and "joining" should be interpreted broadly, unless otherwise explicitly defined, to include, but are not limited to, fixed connections, detachable connections, or integrally formed connections; mechanical or electrical connections; direct connections or indirect connections via an intermediate medium; and internal communication between two components. Those skilled in the art can understand their meaning based on the specific technical solution. The fixed connections involved in this invention, unless otherwise stated, include both detachable fixed connections (such as bolt and screw connections) and non-detachable fixed connections (such as riveting and welding), and may also include integral structures achieved through an integral forming process (such as casting) (except where integral forming is clearly not feasible).

[0076] Unless otherwise stated, the terms used in any of the technical solutions disclosed in this invention to indicate positional relationships or shapes cover states or shapes that are similar to, close to, or nearly similar to those states or shapes.

[0077] Any component provided by the present invention can be assembled from multiple individual components or can be a single component manufactured by a one-piece molding process.

[0078] It should be noted that the structures, proportions, sizes, etc., depicted in the accompanying drawings of this specification are only used to complement the content disclosed in the specification, so as to enable those skilled in the art to understand and read them, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0079] In the embodiments of this application, the same reference numerals are used to denote the same component or the same part.

[0080] Any adaptive changes made according to actual needs are within the scope of protection of this invention.

[0081] It should be noted that, for those skilled in the art, it is obvious that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A combined heat and power all-liquid air separation system, characterized by, The system comprises: an air filtering unit (1); a dual-drive compression unit (2) for receiving and compressing air from the air filtering unit (1); a pre-cooling and purification unit (3) for cooling and purifying medium-pressure air from the dual-drive compression unit (2); a multi-stage pressurization unit connected to the outlet of the pre-cooling and purification unit (3) for gradually pressurizing the purified air, the multi-stage pressurization unit comprising at least two pressurization ends of expanders; a main heat exchanger (9) with an inlet connected to the high-pressure outlet of the multi-stage pressurization unit; a rectification system (10) with an inlet connected to the low-temperature liquid outlet of the main heat exchanger (9); wherein the dual-drive compression unit (2) provides initial pressure for the subsequent multi-stage pressurization unit and is arranged outside the air separation boundary.

2. The combined heat and power all-liquid air separation system of claim 1, wherein: The dual-drive compression unit (2) comprises a compressor and a steam turbine and an electric motor connected to the compressor.

3. The combined heat and power all-liquid air separation system of claim 1, wherein: The multi-stage pressurization unit comprises, in series, a pressurization end of a first expander, a pressurization end of a second expander, and a pressurization end of a third expander, forming a three-stage pressurization circuit. The first expander is a low-pressure expander (5), the second expander is a high-temperature expander (6), and the third expander is a low-temperature expander (7); the outlet of the pre-cooling and purification unit (3) is connected to the inlet of the pressurization end (K-105) of the low-pressure expander, and the outlet of the pressurization end (K-105) of the low-pressure expander is connected, in sequence, to the pressurization end (K-104) of the high-temperature expander, a second cooler (12), the pressurization end (K-102) of the low-temperature expander, a third cooler (13), the main heat exchanger (9), and the rectification system (10) via a first cooler (11), forming a main circuit.

4. The combined heat and power all-liquid air separation system of claim 3, wherein: The system further comprises an expansion refrigeration unit corresponding to the multi-stage pressurization unit; the expansion refrigeration unit comprises an expansion end (K-101) of a low-temperature expander, an expansion end (K-103) of a high-temperature expander, and an expansion end (K-106) of a low-pressure expander.

5. The combined heat and power all-liquid air separation system of claim 4, wherein: The gas stream from the outlet of the pressurization end (K-105) of the low-pressure expander is divided into two streams after being cooled by the first cooler (11): one stream enters the pressurization end (K-104) of the high-temperature expander as a main pressurization gas stream; the other stream enters a first branch (14) as a first expansion gas stream. The first expansion gas stream is cooled by the main heat exchanger (9), and is extracted from the upper part of the main heat exchanger (9) and introduced into the expansion end (K-103) of the high-temperature expander to form a first expanded gas stream. The main pressurization gas stream from the outlet of the pressurization end (K-102) of the low-temperature expander is partially extracted from the main heat exchanger (9) after being cooled by the main heat exchanger (9) as a second expansion gas stream, which is introduced into the expansion end (K-101) of the low-temperature expander via a second branch (15) to form a second expanded gas stream. The second expanded gas stream is divided into two streams: one stream directly enters the lower column of the rectification system (10) via a third branch (16); the other stream returns to the main heat exchanger (9) for reheating to form a reheated gas stream via a fourth branch (17). The first expanded gas stream and the reheated gas stream of the fourth branch (17) are combined and then enter the expansion end (K-106) of the low-pressure expander for expansion. The expanded tail gas returns to the main heat exchanger (9) to provide cold energy and is finally output as the regeneration gas source of the pre-cooling and purification unit (3).

6. The combined heat and power all-liquid air separation system of claim 5, wherein: The first branch (14) is provided with a fifth branch (18) before entering the main heat exchanger (9), and the low-temperature refrigerator (4) is arranged on the fifth branch (18). The pressurized air entering the fifth branch (18) enters the low-temperature refrigerator (4) for cooling and then enters the expansion end (K-103) of the high-temperature expander for expansion to low pressure.

7. The combined heat and power all-liquid air separation system of claim 1, wherein: Further comprising a liquid expander (8); the inlet of the liquid expander (8) is connected to the high-pressure liquid air outlet of the main heat exchanger (9) through a pipeline, and the outlet is connected to the lower tower feed port of the rectification system (10).

8. The combined heat and power all-liquid air separation system of claim 8, wherein: The liquid expander (8) is a liquid turbine with power generation function, which is used to recover the pressure energy of high-pressure liquid air and generate electricity.

9. The combined heat and power all-liquid air separation system of claim 4, wherein: Further comprising a water cooling tower, part or all of the low-pressure exhaust gas reheated from the main heat exchanger (9) and / or the exhaust gas from the expansion end (K-106) of the low-pressure expander are introduced into the water cooling tower for preparing chilled water.

10. A cogeneration all-liquid air separation process characterized by, The use of the combined heat and power full-liquid air separation system according to any one of claims 1-9 comprises the following steps: Air filtration step: dust removal treatment is performed on the ambient air; Steam and electricity dual-drive compression step: the filtered air is compressed to medium pressure and then cooled and delivered to the air separation boundary area; Pre-cooling and purification step: the medium-pressure air is pre-cooled and subjected to adsorption purification to remove water and carbon dioxide impurities; Multi-stage pressurization step: the purified air is introduced into a multi-stage pressurization unit composed of at least two expander pressurization ends in series to perform continuous pressurization; Heat exchange and liquefaction step: the high-pressure air obtained by the multi-stage pressurization step is introduced into the main heat exchanger (9) for cooling, and part of the air is liquefied therein; Rectification separation step: the air liquefied in the main heat exchanger (9) and part of the expanded air are sent to the rectification system (10) for separation to obtain liquid oxygen, nitrogen and argon products.

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