A system and method for coupling liquefied air energy storage with calcium carbide production

Abstract

The application provides a system and method for coupling of liquefied air energy storage and calcium carbide production. The system comprises an air separation unit, an oxygen thermal method calcium carbide production unit, a nitrogen liquefaction unit, an energy release power generation unit, a steam Rankine unit, an organic Rankine unit and a heat storage unit. The method is as follows: in the energy storage stage, air is separated into oxygen and nitrogen by the air separation unit, and the oxygen and nitrogen enter the oxygen thermal method calcium carbide production unit and the nitrogen liquefaction unit respectively to obtain calcium carbide and liquid nitrogen, and the calcium carbide waste heat drives the steam Rankine unit to output electric energy; in the energy release stage, the energy release power generation unit and the organic Rankine unit output electric energy, and the compressed waste heat and the expanded waste cold are used for regional heating and refrigeration. The application can effectively reduce the energy consumption of calcium carbide production, ensure the stable operation of air separation and calcium carbide production, reduce the thermal pollution in the calcium carbide production process, improve the energy efficiency and energy storage density of the system, and has the beneficial technical effects of less transportation link, high equipment utilization and the like.

Description

Technical Field

[0001] This invention belongs to the field of renewable energy power generation and energy storage technology, specifically relating to a liquefied air energy storage and calcium carbide production coupling system and its working method. Background Technology

[0002] Liquefied air energy storage technology is an effective support for building new power systems, but its insufficient utilization of compressed heat energy and low energy efficiency have hindered its commercialization. From the perspective of improving heat energy quality and efficient utilization, liquefied air energy storage coupling technology coupled with external energy systems or industrial processes holds promise for improving system energy storage efficiency and density.

[0003] Industrial processes generate significant amounts of high-grade waste heat, and energy-intensive industrial settings are characterized by high energy consumption and challenging energy conservation and emission reduction tasks. To meet my country's "carbon peak and carbon neutrality" development requirements, related industries have begun industrial transformation and upgrading. Among them, the calcium carbide (calcium carbide) production industry is one of my country's important coal chemical industries, belonging to a key area of ​​high-energy-consuming industries with a large scale of development, facing severe challenges in low-carbon transformation. Furthermore, calcium carbide products reach temperatures as high as 2000℃, and the waste heat is not effectively utilized, causing environmental degradation during production. Summary of the Invention

[0004] The purpose of this invention is to provide a liquefied air energy storage and calcium carbide production coupling system and its working method. The system can reduce energy consumption in calcium carbide production, fully recover waste heat from calcium carbide, and improve the energy efficiency and density of the energy storage system. It also has the advantages of fewer storage and transportation links, high equipment utilization, and low equipment investment and operating costs.

[0005] To achieve the above objectives, the liquefied air energy storage and calcium carbide production coupling system of the present invention includes an air separation unit, an oxygen-thermal calcium carbide production unit, a steam Rankine unit, a liquefied air energy storage system, an organic Rankine unit, a heat storage unit, and a heat transfer medium; the liquefied air energy storage system includes a nitrogen liquefaction unit and an energy release and power generation unit;

[0006] The inlet of the air separation unit is connected to the ambient air, the oxygen outlet of the air separation unit is connected to the inlet of the oxythermal calcium carbide production unit, the tail gas outlet of the oxythermal calcium carbide production unit is connected to the atmosphere, and the calcium carbide product outlet of the oxythermal calcium carbide production unit leads to an external storage tank via a steam Rankine unit and an energy release power generation unit; the nitrogen outlet of the air separation unit is connected to the inlet of the nitrogen liquefaction unit, and the outlet of the nitrogen liquefaction unit is connected to the inlet of the energy release power generation unit.

[0007] The thermal storage unit, the nitrogen liquefaction unit, and the energy release power generation unit form a first circulation loop through a heat transfer medium, while the thermal storage unit, the nitrogen liquefaction unit, and the organic Rankine unit form a second circulation loop through a heat transfer medium.

[0008] The air separation unit adopts a two-stage distillation tower structure based on internal thermal integration.

[0009] The air separation unit is equipped with a heat storage medium to recover the heat generated by its own compression.

[0010] The liquefied air energy storage system also includes a cold storage unit, which forms a third circulation loop with the nitrogen liquefaction unit and the energy release power generation unit through a cold storage medium.

[0011] The cold storage unit uses liquid refrigerant and liquid storage tanks for cold energy recovery and storage, or a filled bed cold storage device or a phase change cold storage device.

[0012] The heat transfer medium is heat transfer oil or pressurized water.

[0013] Both the air separation unit and the liquefied air energy storage system are equipped with air purification devices.

[0014] The above-mentioned system's coupling operation method for liquefied air energy storage and calcium carbide production includes an energy storage stage and an energy release stage;

[0015] During the energy storage stage: air is separated into oxygen and nitrogen by the air separation unit. The oxygen produced after separation enters the oxythermal calcium carbide production unit to produce calcium carbide. The high-temperature waste heat generated during calcium carbide production is transferred to the steam Rankine unit along with the calcium carbide product outlet to drive the steam Rankine unit to output electrical energy. The calcium carbide after heat release and cooling is stored in an internal storage tank. The nitrogen produced after separation enters the nitrogen liquefaction unit to obtain liquid nitrogen. At the same time, the heat of compression generated during nitrogen liquefaction is recovered and stored in the heat storage unit through the heat transfer medium.

[0016] During the energy release phase: Liquid nitrogen from the nitrogen liquefaction unit enters the energy release power generation unit, absorbing the remaining heat energy of the calcium carbide and the compression heat generated by the nitrogen liquefaction unit to drive the turbine of the energy release power generation unit to output electrical energy; the remaining compression heat of the nitrogen liquefaction unit is transferred to the organic Rankine unit to drive the turbine of the organic Rankine unit to do work and output electrical energy.

[0017] The heat storage medium in the air separation unit recovers and stores the heat of compression generated during the separation of air.

[0018] The cold storage unit recovers and stores the cold energy of liquid nitrogen from the energy release power generation unit through a cold storage medium. The cold storage medium transfers the stored cold energy to the nitrogen liquefaction unit for liquefying nitrogen. After the nitrogen liquefaction unit releases cold and reheats, the cycle is completed.

[0019] The beneficial effects of this invention are as follows:

[0020] (1) The air is separated into oxygen and nitrogen by the air separation unit. The oxygen enters the oxygen-thermal calcium carbide production unit to produce calcium carbide, and the nitrogen enters the nitrogen liquefaction unit to liquefy liquid nitrogen. The nitrogen liquefaction unit and the energy release power generation unit constitute a liquefied air energy storage system, thus forming a coupling between liquefied air energy storage and calcium carbide production, which can ensure the stable operation of air separation and calcium carbide production.

[0021] (2) The waste heat generated during the calcium carbide production process is used to drive the steam Rankine unit and the energy release power generation unit to output electrical energy. At the same time, the heat storage unit is used to recover the compression heat of the nitrogen energy storage system during nitrogen liquefaction. The compression heat can be transferred to the energy release power generation unit and the organic Rankine unit through the heat transfer medium in the circulation loop, driving them to output additional electrical energy. This effectively utilizes the waste heat of high-temperature calcium carbide and the compression waste heat during nitrogen liquefaction, reduces thermal pollution in the calcium carbide production process, and improves the energy utilization rate of the system.

[0022] (3) The oxygen and nitrogen products generated by the air separation unit can be directly introduced into the downstream process, thereby eliminating the storage and transportation links. Furthermore, the nitrogen liquefaction unit and the air separation unit of the liquefied air energy storage system share an air purification device, which has the advantages of fewer transportation links, higher equipment utilization rate, and cost savings. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the system structure of the coupling of liquefied air energy storage and calcium carbide production according to the present invention.

[0024] In the diagram: 1—Air separation unit, 2—Oxythermal calcium carbide production unit, 3—Steam Rankine unit, 4—Nitrogen liquefaction unit, 5—Energy release power generation unit, 6—Organic Rankine unit, 7—Heat storage unit.

[0025] Figure 2 This is the air separation result of the air separation unit 1 of the present invention.

[0026] Figure 3 The results show the operation of the oxygen-thermal calcium carbide production unit 2 and the liquefied air energy storage system under different air separation conditions of the present invention.

[0027] Figure 4 The results show the performance parameters of the coupling system of the present invention as a function of the calcium carbide reaction temperature in the oxythermal calcium carbide production unit 2. Detailed Implementation

[0028] The present invention will now be described in further detail with reference to the accompanying drawings.

[0029] like Figure 1The system shown is a coupling system of liquefied air energy storage and calcium carbide production, comprising an air separation unit 1, an oxythermal calcium carbide production unit 2, a steam Rankine unit 3, a nitrogen liquefaction unit 4, an energy release power generation unit 5, an organic Rankine unit 6, a heat storage unit 7, and a heat transfer medium. The inlet of the air separation unit 1 is connected to the ambient air, producing oxygen and nitrogen. The oxygen outlet of the air separation unit 1 is connected to the oxygen inlet of the oxythermal calcium carbide production unit 2. The separated oxygen enters the oxythermal calcium carbide production unit 2 and reacts with calcium carbide raw materials to produce calcium carbide. The exhaust outlet of the oxythermal calcium carbide production unit 2 is connected to the atmosphere. The calcium carbide product outlet of the oxythermal calcium carbide production unit 2 is connected to an external storage tank via the steam Rankine unit 3 and the energy release power generation unit 5. Simultaneously, heat energy is transferred to the steam Rankine unit 3 and the energy release power generation unit 5 through the calcium carbide product outlet pipe to drive the steam Rankine unit 3 and increase the turbine operating temperature of the energy release power generation unit 5. Nitrogen is used as the energy storage medium, and a liquefied air energy storage system is formed by nitrogen liquefaction unit 4 and energy release power generation unit 5. The nitrogen outlet of air separation unit 1 is connected to the inlet of nitrogen liquefaction unit 4. The separated nitrogen enters nitrogen liquefaction unit 4 to form liquid nitrogen and generates heat of compression. The outlet of nitrogen liquefaction unit 4 is connected to the inlet of energy release power generation unit 5. Liquid nitrogen enters energy release power generation unit 5 and transfers the heat of compression to energy release power generation unit 5 and organic Rankine unit 6 through a heat transfer medium. The heat of compression heats the nitrogen at the turbine inlet of energy release power generation unit 5, and the waste heat of compression can drive organic Rankine unit 6 to output additional electrical energy. The heat of compression is recovered and stored by heat storage unit 7. Heat storage unit 7, nitrogen liquefaction unit 4, and energy release power generation unit 5 form a first circulation loop through a heat transfer medium. At the same time, heat storage unit 7, nitrogen liquefaction unit 4, and organic Rankine unit 6 form a second circulation loop through a heat transfer medium. The heat transfer medium is heat transfer oil or pressurized water. This combination of liquefied air energy storage and calcium carbide production not only effectively recovers the high-temperature waste heat from calcium carbide production, alleviating thermal pollution problems, but also improves the energy efficiency and energy storage density of the liquefied air energy storage system.

[0030] It should be noted that the air separation unit 1 adopts a two-stage distillation tower structure based on internal thermal integration and uses atmospheric pressure water as the heat storage medium to recover the heat of compression generated during air separation and use it for district heating. The exhaust temperature of the final turbine of the energy release power generation unit 5 is relatively low, and its expansion waste cooling is used for district cooling to further improve the system energy efficiency.

[0031] Furthermore, the inlet of the oxythermal calcium carbide production unit 2 also includes a carbon feedstock and a calcium source feedstock. The carbon feedstock is coal or coke, and the calcium source is limestone, quicklime, or hydrated lime. A portion of the carbon feedstock is burned with oxygen from the air separation unit 1 to provide heat for calcium carbide production, while the remainder reacts with the calcium source to produce calcium carbide. Thus, by using carbon combustion for heating, the energy consumption of calcium carbide production can be significantly reduced compared to traditional electrothermal calcium carbide production.

[0032] The liquefied air energy storage system further includes a cold storage unit. This unit, along with the nitrogen liquefaction unit 4 and the energy release power generation unit 5, forms a third circulation loop via a cold storage medium. The cold storage unit recovers and stores the cold energy from the liquid nitrogen in the energy release power generation unit 5 through the cold storage medium. The cold energy stored in the cold storage medium is transferred to the nitrogen liquefaction unit 4 for nitrogen liquefaction. After being released and reheated by the nitrogen liquefaction unit 4, the cycle is completed. The cold storage unit uses a liquid refrigerant and a liquid storage tank, or it can use a packed bed cold storage device or a phase change cold storage device.

[0033] Preferably, the nitrogen liquefaction unit 4 and the air separation unit 1 of the liquefied air energy storage system share an air purification device. This improves equipment utilization and reduces equipment investment costs.

[0034] The working method of the liquefied air energy storage and calcium carbide production coupling system of the present invention is as follows:

[0035] During the energy storage phase, driven by electricity from a renewable energy power plant or the grid, ambient air is separated by air separation unit 1 to obtain oxygen with a concentration of 91-97 mol% and nitrogen with a concentration of 99-98 mol%. The separated oxygen enters the oxythermal calcium carbide production unit 2 through the oxygen outlet of air separation unit 1 to react with carbon raw materials and calcium source to produce calcium carbide. The separated nitrogen enters the nitrogen liquefaction unit 4 of the liquefied air energy storage system through the nitrogen outlet of air separation unit 1 to obtain liquid nitrogen. The liquid nitrogen at the outlet of nitrogen liquefaction unit 4 is stored in a cryogenic storage tank. In this way, the oxygen and nitrogen products from air separation unit 1 can directly enter the downstream process, thereby eliminating the storage and transportation links, realizing energy supply and demand management, and ensuring stable system operation.

[0036] The high-temperature waste heat of calcium carbide is used to drive the steam Rankine unit 3 to generate electricity, in order to compensate for the electrical energy consumed by the air separation unit 1 and the nitrogen liquefaction unit 4. The calcium carbide at the outlet of the oxygen thermal calcium carbide production unit 2 is cooled and stored in an internal storage tank. The heat storage medium of the air separation unit 1 is atmospheric pressure water to recover and store the heat of compression generated during the separation of air. The heat of compression generated by the nitrogen liquefaction unit 4 is stored in the heat storage unit 7 through the heat transfer medium.

[0037] During the energy release phase, the obtained liquid nitrogen enters the energy release power generation unit 5, absorbs the waste heat of calcium carbide and the compression heat of nitrogen liquefaction unit 4 to raise the temperature, drives the turbine of energy release power generation unit 5 to output electrical energy, and the low-temperature nitrogen at the turbine outlet of energy release power generation unit 5 can be used for district cooling; the compression heat generated by nitrogen liquefaction unit 4 simultaneously drives organic Rankine unit 6 to output additional electrical energy, and uses the compression heat of air separation unit 1 to achieve district heating.

[0038] The system of this invention utilizes the waste heat from calcium carbide in a tiered manner. First, water is heated to obtain supercritical superheated steam, which drives the steam Rankine unit 3 to generate electricity, ensuring the safe and effective recovery of high-temperature calcium carbide waste heat. Then, the remaining sensible heat of the calcium carbide is used to heat the nitrogen at the inlet of the first-stage turbine of the energy release power generation unit 5, thereby increasing the power / capacity level of the energy storage system. Furthermore, the compression heat generated by the nitrogen liquefaction unit 4 is used to raise the inlet temperature of the intermediate and final-stage turbines of the energy release power generation unit 5, and the compression heat drives the organic Rankine unit 6. This achieves full utilization of the waste heat from calcium carbide and the compression heat in the coupled system. Since the calcium carbide mass flow rate of the oxygen-thermal calcium carbide production unit 2 is much lower than the nitrogen mass flow rate of the energy release power generation unit 5, the remaining heat after the calcium carbide drives the steam Rankine unit 3 is insufficient to heat the nitrogen in the energy release power generation unit 5 in multiple stages. To this end, the coupling system of this invention first utilizes the residual high-temperature heat energy of calcium carbide to heat the nitrogen gas at the inlet of the first-stage turbine, thereby increasing the operating temperature of the energy release and power generation unit 5. Then, the medium-temperature compression heat of the nitrogen liquefaction unit 4 is used to drive the turbine output power of the subsequent working stage, while the turbine obtains turbine exhaust gas at a temperature lower than the ambient temperature under the condition of a lower inlet temperature, thereby providing regional cooling. This achieves efficient utilization of waste heat and waste cooling in the coupling system.

[0039] Figure 2 This paper presents the air separation results of air separation unit 1 in the liquefied air energy storage and calcium carbide production coupling system of the present invention. Under an inlet air flow rate of 132.69 kg / s, when the separated oxygen concentration increased from 91 mol% to 97 mol%, the nitrogen concentration decreased from 99 mol% to 98 mol%; when the separated oxygen concentration increased from 97 mol% to 99 mol%, the nitrogen concentration decreased significantly, from 98 mol% to 94.3 mol%. Conventional air separation products typically have oxygen and nitrogen concentrations of 99.99 mol% or higher. Such high-purity separation conditions place high demands on air separation equipment and operational control, leading to higher costs. Therefore, air separation unit 2 of the coupling system of the present invention operates under lower oxygen and nitrogen separation purity conditions, reducing system costs. Simultaneously, both the oxythermal calcium carbide production unit 2 and the liquefied air energy storage system exhibit good performance at lower nitrogen and oxygen concentrations.

[0040] Figure 3 The results show the operation of the oxygen-thermal calcium carbide production unit 2 and the liquefied air energy storage system in the coupled system of this invention. It can be found that when the oxygen concentration is 91-97 mol% and the nitrogen concentration is 99-98 mol%, the calcium carbide product of the oxygen-thermal calcium carbide production unit 2 has higher yield and purity, and the liquefied air energy storage system also has higher energy storage density, both of which are superior to the calcium carbide parameters and energy storage system performance under high oxygen / nitrogen concentrations.

[0041] Figure 4The results show the performance parameters of the coupling system of the present invention as a function of the calcium carbide reaction temperature in the oxythermal calcium carbide production unit 2. Analysis indicates that when the calcium carbide reaction temperature varies between 1900-2300℃, it has completely opposite effects on the performance of the oxythermal calcium carbide production unit 2 and the liquefied air energy storage system; preferably, the optimal design for calcium carbide production and energy storage can be obtained at a reaction temperature of 2200℃.

[0042] The coupling system of this invention ingeniously combines the oxygen-thermal calcium carbide production unit 1 and the liquefied air energy storage system through the air separation unit 1, achieving a high degree of integration of the raw material layer, equipment layer and system layer, effectively improving the overall performance of the coupling system and expanding the industrial application functions of the liquefied air energy storage system.

Claims

1. A liquefied air energy storage and calcium carbide production coupling system, characterized in that: It includes an air separation unit (1), an oxygen-thermal calcium carbide production unit (2), a steam Rankine unit (3), a liquefied air energy storage system, an organic Rankine unit (6), a thermal storage unit (7), and a heat transfer medium; the liquefied air energy storage system includes a nitrogen liquefaction unit (4) and an energy release power generation unit (5). The inlet of the air separation unit (1) is connected to the ambient air, the oxygen outlet of the air separation unit (1) is connected to the inlet of the oxythermal calcium carbide production unit (2), the tail gas outlet of the oxythermal calcium carbide production unit (2) is connected to the atmosphere, and the calcium carbide product outlet of the oxythermal calcium carbide production unit (2) is connected to an external storage tank via a steam Rankine unit (3) and an energy release power generation unit (5); the nitrogen outlet of the air separation unit (1) is connected to the inlet of the nitrogen liquefaction unit (4), and the outlet of the nitrogen liquefaction unit (4) is connected to the inlet of the energy release power generation unit (5); The thermal storage unit (7), the nitrogen liquefaction unit (4), and the energy release power generation unit (5) form a first circulation loop through a heat transfer medium. At the same time, the thermal storage unit (7), the nitrogen liquefaction unit (4), and the organic Rankine unit (6) form a second circulation loop through a heat transfer medium.

2. The liquefied air energy storage and calcium carbide production coupling system as described in claim 1, characterized in that: The air separation unit (1) adopts a two-stage distillation tower structure based on internal thermal integration.

3. The liquefied air energy storage and calcium carbide production coupling system as described in claim 1, characterized in that: The air separation unit (1) is equipped with a heat storage medium that recovers the heat of compression it generates.

4. The liquefied air energy storage and calcium carbide production coupling system as described in claim 1, characterized in that: The liquefied air energy storage system also includes a cold storage unit, which forms a third circulation loop with the nitrogen liquefaction unit (4) and the energy release power generation unit (5) through a cold storage medium.

5. The liquefied air energy storage and calcium carbide production coupling system as described in claim 4, characterized in that: The cold storage unit uses liquid refrigerant and liquid storage tanks for cold energy recovery and storage, or a filled bed cold storage device or a phase change cold storage device.

6. The liquefied air energy storage and calcium carbide production coupling system as described in claim 1, characterized in that: The heat transfer medium is heat transfer oil or pressurized water.

7. The liquefied air energy storage and calcium carbide production coupling system as described in claim 1, characterized in that: Both the air separation unit (1) and the liquefied air energy storage system are equipped with air purification devices.

8. A method for coupling liquefied air energy storage and calcium carbide production in a system as described in any one of claims 1 to 7, characterized in that: Includes the energy storage stage and the energy release stage; In the energy storage stage: air is separated into oxygen and nitrogen by the air separation unit (1). The oxygen produced after separation enters the oxythermal calcium carbide production unit (2) to prepare calcium carbide. The high-temperature waste heat generated during the preparation of calcium carbide is transferred to the steam Rankine unit (3) along with the calcium carbide product outlet to drive the steam Rankine unit (3) to output electrical energy. The calcium carbide after heat release and cooling is stored in the internal storage tank. The nitrogen produced after separation enters the nitrogen liquefaction unit (4) to obtain liquid nitrogen. At the same time, the compression heat generated during nitrogen liquefaction is recovered and stored in the heat storage unit (7) through the heat transfer medium. During the energy release stage: the liquid nitrogen in the nitrogen liquefaction unit (4) enters the energy release power generation unit (5), absorbing the remaining heat energy of the calcium carbide and the compression heat generated by the nitrogen liquefaction unit (4) to drive the turbine of the energy release power generation unit (5) to output electrical energy; the remaining compression heat of the nitrogen liquefaction unit (4) is transferred to the organic Rankine unit (6) to drive the turbine of the organic Rankine unit (6) to do work and output electrical energy.

9. The method for coupling liquefied air energy storage with calcium carbide production as described in claim 8, characterized in that: The heat storage medium in the air separation unit (1) recovers and stores the heat generated during the separation of air.

10. A method for coupling liquefied air energy storage and calcium carbide production in a system as described in any one of claims 4 to 5, characterized in that: Includes the energy storage stage and the energy release stage; In the energy storage stage: air is separated into oxygen and nitrogen by the air separation unit (1). The oxygen produced after separation enters the oxythermal calcium carbide production unit (2) to prepare calcium carbide. The high-temperature waste heat generated during the preparation of calcium carbide is transferred to the steam Rankine unit (3) along with the calcium carbide product outlet to drive the steam Rankine unit (3) to output electrical energy. The calcium carbide after heat release and cooling is stored in the internal storage tank. The nitrogen produced after separation enters the nitrogen liquefaction unit (4) to obtain liquid nitrogen. At the same time, the compression heat generated during nitrogen liquefaction is recovered and stored in the heat storage unit (7) through the heat transfer medium. During the energy release stage: liquid nitrogen in the nitrogen liquefaction unit (4) enters the energy release power generation unit (5), absorbing the remaining heat energy of calcium carbide and the compression heat generated by the nitrogen liquefaction unit (4) to drive the turbine of the energy release power generation unit (5) to output electrical energy; the remaining compression heat of the nitrogen liquefaction unit (4) is transferred to the organic Rankine unit (6) to drive the turbine of the organic Rankine unit (6) to do work and output electrical energy; The cold storage unit recovers and stores the cold energy of liquid nitrogen from the energy release and power generation unit (5) through the cold storage medium. The cold storage medium transfers the stored cold energy to the nitrogen liquefaction unit (4) for liquefying nitrogen. After the nitrogen liquefaction unit (4) releases cold and reheats, the cycle is completed.

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