Efficient recycling method for heat energy of medium-temperature zone in gas injection of gas storage

Abstract

The invention discloses a method for efficiently recycling heat energy of a medium-temperature zone in gas injection of a gas storage, and relates to the technical field of oil and gas field surface engineering, which comprises a medium-temperature zone heat energy recycling part: when a gas injection compressor of the gas storage runs, low-pressure natural gas is compressed into medium-temperature high-pressure natural gas, and the medium-temperature high-pressure natural gas exchanges heat with normal-temperature MgSO4. 6H2O in a first countercurrent heat exchange moving bed; mgSO4. 6H2O can be heated to lose water and become MgSO4. 2H2O when absorbing heat, the temperature of the medium-temperature and high-pressure natural gas is rapidly reduced to 40 DEG C after heat exchange, the medium-temperature and high-pressure natural gas becomes low-temperature and high-pressure natural gas and enters other production links, and recovery of heat energy of the medium-temperature zone is achieved. In the natural gas injection process, the method solves the problems that an existing air cooler is wide in occupied area, high in investment cost, large in noise, poor in flexibility and incapable of recycling heat energy of a medium-temperature zone. The natural gas medium-temperature zone heat energy can be efficiently recycled on the premise that the temperature of natural gas is rapidly reduced, meanwhile, long-time storage and cross-season or cross-distance utilization are achieved, the input cost is low, the popularization difficulty is small, and benefits are remarkable.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas field surface engineering, and particularly relates to a method for efficiently recovering and utilizing medium-temperature heat energy during gas injection into a gas storage reservoir. Background Art

[0002] Underground gas storage reservoirs have the characteristics of large volume, economy, being unaffected by climate, safety and reliability, and being able to reasonably adjust gas supply imbalance. They can alleviate the problem of uneven gas supply caused by different demands for natural gas from various users and load changes. The operation of gas storage reservoirs generally takes one year as a cycle. "Gas production in winter and spring, gas injection in summer and autumn" is the operation process of gas storage reservoirs in China. During the natural gas injection process, compressors are mainly used to compress low-pressure natural gas and then inject it into the gas storage reservoir. The compression process of natural gas will cause the temperature of natural gas to rise. Taking three-stage compression as an example, after the first-stage compression, the temperature of low-pressure natural gas rises from 10°C to 60°C. Subsequently, the natural gas cooled to below 40°C is heated to 80°C after the second-stage compression. After being cooled again, the natural gas at 40°C is heated to above 95°C after the third-stage compression. Finally, after being cooled to below 50°C, it enters the subsequent process. Calculated based on the gas injection peak shaving volume of every ten million cubic meters of gas storage reservoir operation, the recoverable waste heat is about 9.5×10 8 kJ (equivalent to 32.3 tons of standard coal). Currently, air coolers are mainly used to cool the compressed natural gas, which has problems such as large land occupation, high investment cost, and high noise. In addition, the existing cooling methods cannot recover the heat energy resources of natural gas.

[0003] Since gas injection in China mainly occurs in summer and autumn, it is difficult to use the medium-temperature heat energy generated by compressed natural gas for heating. In addition, due to the remote location of gas storage reservoirs, it is difficult to use the heat energy for summer refrigeration, and it is necessary to explore cross-seasonal or cross-distance utilization methods. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for efficiently recovering and utilizing medium-temperature heat energy during gas injection into a gas storage reservoir, which can quickly cool the natural gas during the gas injection process of the gas storage reservoir, and at the same time efficiently recover, store for a long time, and utilize across seasons or distances the heat energy thereof. This method can improve the problems of large land occupation, high investment cost, high noise, and poor flexibility of existing air coolers.

[0005] To achieve the above purpose, the technical solution of the present application is: A method for efficiently recovering and utilizing medium-temperature heat energy during gas injection into a gas storage reservoir, including:

[0006] Medium-temperature heat energy recovery part: When the gas injection compressor of the gas storage reservoir is operating, low-pressure natural gas is compressed into medium-temperature high-pressure natural gas and exchanges heat with normal-temperature MgSO 4 ·6H 2 O in the first countercurrent heat exchange moving bed, and MgSO 4 ·6H 2Upon absorbing heat, O loses water of crystallization to become MgSO 4 ·2H 2 O. After heat exchange, the medium-temperature and high-pressure natural gas rapidly cools down to 40 degrees and becomes low-temperature and high-pressure natural gas, entering the remaining production processes to recover the medium-temperature zone heat energy.

[0007] Furthermore, it also includes:

[0008] Medium-temperature zone heat energy storage part: MgSO formed in the medium-temperature zone heat energy recovery part 4 ·2H 2 O only needs to be stored at normal pressure under the conditions of being dry, sealed, and isolated from water, that is, MgSO is stored in the first sealed storage tank 4 ·2H 2 O, realizing the cross-seasonal or cross-distance utilization of its chemical energy (heat). Storing it in a sealed storage tank is convenient for handling and transportation. For the cross-seasonal utilization of medium-temperature zone heat energy, it can be used for winter heating, heating in the throttling process during gas production, etc.; for cross-distance utilization, it can be used for oil extraction in nearby oilfields, etc.

[0009] Furthermore, it also includes:

[0010] Medium-temperature zone heat energy utilization part: When using medium-temperature zone heat energy, the heated medium exchanges heat with MgSO stored in the first sealed storage tank 4 ·2H 2 O in the second countercurrent heat exchange moving bed. Wet air is introduced at the bottom of the second countercurrent heat exchange moving bed. After MgSO 4 ·2H 2 O contacts with wet air, it absorbs water and becomes MgSO 4 ·6H 2 O, and at the same time releases a large amount of heat. After the heated medium is heated and its temperature rises, it enters the remaining production processes to realize the flexible utilization of medium-temperature zone heat energy.

[0011] Furthermore, the medium-temperature zone heat energy storage part also includes: a second sealed storage tank for storing MgSO formed in the medium-temperature zone heat energy utilization part 4 ·6H 2 O. Part of MgSO 4 ·6H 2 O is recycled to the medium-temperature zone heat energy recovery part for use, and the remaining part realizes the cross-seasonal or cross-distance utilization of its chemical energy (heat).

[0012] Furthermore, in the first countercurrent heat exchange moving bed, natural gas flows upward from bottom to top in the heat exchange tube side, and normal-temperature MgSO 4 ·6H 2 O flows downward by gravity from top to bottom in the shell side to realize countercurrent heat exchange and improve the heat transfer efficiency.

[0013] Furthermore, a water vapor outlet is provided at the top of the first countercurrent heat exchange moving bed to immediately discharge the generated water vapor; after heat exchange, MgSO 4 ·2H 2 O is discharged from the bottom discharge port of the first countercurrent heat exchange moving bed and enters the first sealed storage tank.

[0014] Furthermore, in the second countercurrent heat exchange moving bed, the medium to be heated flows upward from bottom to top in the heat exchange tube pass, and MgSO 4 ·2H 2 O flows downward by gravity from top to bottom in the shell pass.

[0015] Furthermore, a medium-temperature dry air outlet is provided at the top of the second countercurrent heat exchange moving bed to immediately discharge the generated medium-temperature dry air; after heat exchange, MgSO 4 ·6H 2 O is discharged from the bottom discharge port of the second countercurrent heat exchange moving bed and enters the second sealed storage tank.

[0016] As a further step, the outlet of the first countercurrent heat exchange moving bed is connected to the inlet of the second countercurrent heat exchange moving bed through the first sealed storage tank, and the outlet of the second countercurrent heat exchange moving bed is connected to the inlet of the first countercurrent heat exchange moving bed through the second sealed storage tank.

[0017] As a further step, the medium to be heated can be petroleum, natural gas, water, etc.

[0018] Due to the adoption of the above technical solutions, the present invention can achieve the following technical effects: a technology for efficiently recovering and flexibly utilizing medium-temperature thermal energy in gas storage injection. During the natural gas injection process, it solves the problems of large land occupation, high investment cost, high noise, poor flexibility of existing air coolers, and the inability to recover medium-temperature thermal energy. It can efficiently recover the medium-temperature thermal energy in natural gas while ensuring the rapid temperature reduction of natural gas, and at the same time achieve long-term storage and cross-seasonal or cross-distance utilization, with low input cost, low promotion difficulty, and remarkable benefits (calculated based on the injection peak shaving gas volume of 10 million cubic meters per operation of the gas storage, the recovered medium-temperature thermal energy income is about 94,800 yuan, and the CO 2 emission reduction is about 80.5t). While ensuring the safe and stable operation of the gas storage project, it helps to achieve the "dual carbon" goal. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the method for efficiently recovering and utilizing medium-temperature thermal energy in gas storage injection;

[0020] Explanation of the numbers in the figure: 1 - injection compressor, 2 - first countercurrent heat exchange moving bed, 3 - first sealed storage tank, 4 - second countercurrent heat exchange moving bed, 5 - second sealed storage tank. DETAILED DESCRIPTION OF THE INVENTION

[0021] The principles of the present disclosure will be described below with reference to several exemplary embodiments shown in the accompanying drawings. Although the preferred embodiments of the present disclosure are shown in the drawings, it should be understood that the description of these embodiments is only for enabling those skilled in the art to better understand and then implement the present disclosure, rather than limiting the scope of the present disclosure in any way.

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the specification of the embodiments of the present application. Obviously, the described embodiments are some, rather than all, of the embodiments of the present application. Usually, the components of the embodiments of the present application described and illustrated in the drawings here can be arranged and designed in various different configurations.

[0023] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the present application claimed, but merely represents selected embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts shall fall within the scope of protection of the present application.

[0024] It should be noted that like reference numerals and letters denote like items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0025] It should be noted that in this document, the terms "include", "comprise", or any other variant thereof are intended to cover a non-exclusive inclusion, such that an article or device including a series of elements not only includes those elements but also includes other elements not explicitly listed, or further includes elements inherent to such process, method, article, or device. Without further limitation, an element defined by the statement "including one..." does not exclude the existence of additional identical elements in the process, method, article, or device including the element. The terms "first", "second", etc. may refer to different or the same objects. There may also be other explicit and implicit definitions hereinafter.

[0026] In the description of the present application, the orientation or positional relationship indicated by the terms "upper", "lower", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of this application is customarily placed during use. It is only for the convenience of describing the present application 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, and therefore should not be construed as a limitation to the present application.

[0027] In the description of the present application, it should also be noted that unless otherwise clearly specified and limited, the terms "arrangement" and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific situations.

[0028] This embodiment provides a method for efficiently recovering the medium-temperature heat energy in natural gas during the gas injection process of a gas storage reservoir and subsequent cross-seasonal or cross-distance utilization. This method can rapidly cool the medium-temperature natural gas, reduce the compression energy consumption, and at the same time store the recovered waste heat for a long time, enabling cross-seasonal or cross-distance utilization. It avoids the waste of heat energy resources and helps to achieve the "dual carbon" goal while ensuring the safe and stable operation of the gas storage reservoir project. This method uses MgSO 4 ·6H 2 O as the heat exchange medium and utilizes the thermochemical properties of MgSO 4 ·6H 2 O, that is, MgSO 4 ·6H 2 O will lose water when heated at 60 - 100 °C and become MgSO 4 ·2H 2 O and absorb heat, and MgSO 4 ·2H 2 O will increase in temperature by 55 - 70 °C and become MgSO 4 ·6H 2 O and release heat when contacting water. Combining with the operation mode of the gas injection compressor in the gas storage reservoir, a method for efficiently recovering and utilizing the medium-temperature heat energy during gas injection in the gas storage reservoir is proposed; this method mainly includes three parts:

[0029] Medium-temperature heat energy recovery part: Low-pressure natural gas enters the gas injection compressor 1 for pressurization. The medium-temperature high-pressure natural gas after compression exchanges heat with the normal-temperature MgSO 4 ·6H 2 O stored in the second sealed storage tank 5 in the first countercurrent heat exchange moving bed 2. MgSO 4 ·6H 2 O will lose water when absorbing heat (60 - 100 °C) and become MgSO 4 ·2H 2 O (670 J / g, more than twice the phase change latent heat of paraffin), and the medium-temperature high-pressure natural gas, after heat exchange, rapidly reduces its temperature to 40 degrees and becomes low-temperature high-pressure natural gas, entering the remaining production links to achieve the recovery of medium-temperature heat energy. In the first countercurrent heat exchange moving bed, the natural gas flows upward from bottom to top in the heat exchange tube side, and the normal-temperature MgSO 4 ·6H2 O flows downward by gravity from top to bottom in the shell side to achieve countercurrent heat exchange and improve heat transfer efficiency. To ensure the immediate discharge of the generated water vapor, a water vapor outlet is provided at the top of the first countercurrent heat exchange moving bed. After heat exchange, MgSO 4 ·2H 2 O is discharged from the bottom discharge port of the first countercurrent heat exchange moving bed and enters the first sealed storage tank 3 for storage.

[0030] Mid-temperature heat storage part: The MgSO formed by the mid-temperature heat recovery part 4 ·2H 2 O and the MgSO formed by the mid-temperature heat utilization part 4 ·6H 2 O needs to be stored under normal pressure under the conditions of being dry, sealed and isolated from water. Therefore, it can be stored in a sealed storage tank (of appropriate size for easy handling and transportation). For the cross-seasonal utilization of mid-temperature heat, it can be used for winter heating, heating in the throttling process during gas production, etc.; for cross-distance utilization, it can be used for oil extraction in nearby oilfields, etc.

[0031] Mid-temperature heat utilization part: When using mid-temperature heat, the medium to be heated exchanges heat with the MgSO stored in the first sealed storage tank 3 4 ·2H 2 O in the second countercurrent heat exchange moving bed. In the second countercurrent heat exchange moving bed, the medium to be heated flows upward from bottom to top in the heat exchange tube side, and MgSO 4 ·2H 2 O flows downward by gravity from top to bottom in the shell side. Wet air is introduced into the bottom of the second countercurrent heat exchange moving bed. MgSO 4 ·2H 2 O absorbs water and turns into MgSO after contacting the water in the wet air 4 ·6H 2 O, and at the same time releases a large amount of heat (55 - 70 °C, 670 J / g). After the medium to be heated is heated and its temperature rises, it enters the remaining production links to achieve the flexible utilization of mid-temperature heat. After heat exchange, MgSO 4 ·6H 2 O is discharged from the bottom discharge port of the second countercurrent heat exchange moving bed and enters the second sealed storage tank for storage, and can be recycled to the mid-temperature heat recovery part for use. The generated mid-temperature dry air is discharged from the top of the second countercurrent heat exchange moving bed. The medium to be heated can be petroleum, natural gas, water, etc.

[0032] Through the application of the above technologies, the efficient recovery and flexible utilization of the mid-temperature heat generated during the operation of the gas storage injection compressor can be achieved.

[0033] The above description is only an optional embodiment of the present disclosure and is not intended to limit the present disclosure. For those skilled in the art, the present disclosure may have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present disclosure shall be included within the protection scope of the present disclosure.

[0034] Although the claims in this application have been formulated for specific combinations of features, it should be understood that the scope of the present disclosure also includes any novel feature or any novel combination of features that are explicitly or implicitly disclosed herein or any generalization thereof, whether or not it relates to the same solution in any of the currently claimed claims.

Claims

1. A method for efficient recovery and utilization of medium-temperature heat energy during gas injection into a gas storage reservoir, characterized in that, it includes: Mid-temperate heat recovery section: When the gas injection compressor of the gas storage reservoir operates, low-pressure natural gas is compressed into medium-temperature and high-pressure natural gas, which exchanges heat with normal-temperature MgSO 4 ·6H 2 O in the first countercurrent heat exchange moving bed. When MgSO 4 ·6H 2 O absorbs heat, it will lose water due to heating and become MgSO 4 ·2H 2 O. After the medium-temperature and high-pressure natural gas exchanges heat, its temperature rapidly drops to 40 degrees and becomes low-temperature and high-pressure natural gas, which enters the remaining production links to realize the recovery of mid-temperate heat energy.

2. The method for efficient recovery and utilization of medium-temperature heat energy during gas injection into a gas storage reservoir according to claim 1, characterized in that, it further includes: Mid-temperate thermal energy storage section: Store MgSO formed by the mid-temperate thermal energy recovery section in the first sealed storage tank 4 ·2H 2 O to realize the cross-seasonal or cross-distance utilization of its chemical energy.

3. The method for efficient recovery and utilization of medium-temperature heat energy during gas injection into a gas storage reservoir according to claim 1 or 2, characterized in that, it further includes: Mid-temperate heat energy utilization part: When using mid-temperate heat energy, the medium to be heated exchanges heat with MgSO stored in the first sealed storage tank 4 ·2H 2 O in the second counter-current heat exchange moving bed. Wet air is introduced into the bottom of the second counter-current heat exchange moving bed. After MgSO 4 ·2H 2 O contacts with the wet air, it absorbs water and becomes MgSO 4 ·6H 2 O, and at the same time releases a large amount of heat. After the medium to be heated is heated and its temperature rises, it enters the remaining production links to achieve the flexible utilization of mid-temperate heat energy.

4. The method for efficient recovery and utilization of medium-temperature heat energy during gas injection into a gas storage reservoir according to claim 3, characterized in that, The mid-temperate heat storage section also includes: a second sealed storage tank for storing MgSO formed by the mid-temperate heat utilization section 4 ·6H 2 O, and part of the MgSO 4 ·6H 2 O is recycled to the mid-temperate heat recovery section for use, and the remaining part realizes the cross-seasonal or cross-distance utilization of its chemical energy.

5. The method for efficient recovery and utilization of medium-temperature heat energy during gas injection into a gas storage reservoir according to claim 1, characterized in that, In the first countercurrent heat exchange moving bed, natural gas flows upward from bottom to top in the heat exchange tube side, and normal temperature MgSO 4 ·6H 2 O flows downward by gravity from top to bottom in the shell side to achieve countercurrent heat exchange and improve the heat transfer efficiency.

6. The method for efficient recovery and utilization of medium-temperature heat energy during gas injection into a gas storage reservoir according to claim 2, characterized in that, A steam outlet is provided at the top of the first countercurrent heat exchange moving bed; after heat exchange is completed, MgSO 4 ·2H 2 O is discharged from the bottom discharge port of the first countercurrent heat exchange moving bed and enters the first sealed storage tank.

7. The method for efficient recovery and utilization of medium-temperature heat energy during gas injection into a gas storage reservoir according to claim 3, characterized in that, In the second countercurrent heat exchange moving bed, the medium to be heated flows upward from bottom to top in the heat exchange tube pass, while MgSO 4 ·2H 2 O flows downward by gravity from top to bottom in the shell pass.

8. The method for efficient recovery and utilization of medium-temperature heat energy during gas injection into a gas storage reservoir according to claim 4, characterized in that, There is a medium-temperature dry air outlet at the top of the second countercurrent heat exchange moving bed. After heat exchange is completed, MgSO 4 ·6H 2 O is discharged from the bottom discharge port of the second countercurrent heat exchange moving bed and enters the second sealed storage tank.

9. The method for efficient recovery and utilization of medium-temperature heat energy during gas injection into a gas storage reservoir according to claim 4, characterized in that, the outlet of the first counter-current heat exchange moving bed is connected to the inlet of the second counter-current heat exchange moving bed through a first sealed storage tank, and the outlet of the second counter-current heat exchange moving bed is connected to the inlet of the first counter-current heat exchange moving bed through a second sealed storage tank.

10. The method for efficient recovery and utilization of medium-temperature heat energy during gas injection into a gas storage reservoir according to claim 3, characterized in that, the heated medium is petroleum or natural gas or water.

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