Efficient recycling system for gas injection waste heat of gas storage

Abstract

The invention belongs to the field of oil and gas field surface engineering, and discloses an efficient recycling system for gas injection waste heat of a gas storage. Natural gas in the gas injection process of the gas storage is rapidly cooled by utilizing the heat absorption and heat release characteristics in the generation and decomposition processes of hydrated salt, meanwhile, residual heat is efficiently recycled and stored for a long time, and cross-seasonal utilization of the heat is achieved. According to the technology, waste heat generated in the gas injection process of the gas storage is efficiently recycled through a waste heat recycling system and is flexibly applied to other technological processes, so that comprehensive utilization of energy, energy conservation and consumption reduction are achieved.

Description

Technical Field

[0001] The invention belongs to the field of oil and gas field surface engineering, and in particular relates to a highly automated gas storage reservoir gas injection waste heat efficient recovery and utilization system. Background Art

[0002] Gas storage is one of the key infrastructures in the natural gas industry. Its main function is to store and regulate natural gas supply to cope with fluctuations in demand. Underground gas storage can effectively balance the uneven supply and demand of natural gas due to its large capacity, economy and safety. The operation cycle of a gas storage is usually one year, with gas extraction in winter and spring and gas injection in summer and autumn. During the gas injection process, natural gas needs to undergo two-stage or three-stage compression, which causes a significant increase in temperature. Cooling measures are required to ensure the safety and efficiency of the system. However, the existing air cooler cooling method cannot achieve waste heat recovery.

[0003] In the process of injecting natural gas into the gas storage, a compressor is needed to compress the natural gas, which generates a lot of heat. The existing technology has significant deficiencies in the utilization of waste heat, which is mainly reflected in the fact that the heat is simply dissipated or processed by traditional heat dissipation equipment, which not only wastes a lot of energy but also increases energy costs. In addition, most of the waste heat generated by the gas storage is not effectively stored and utilized, and it is impossible to provide additional energy support when needed. With the increase in global energy demand and the improvement of energy efficiency requirements, how to maximize the recovery and utilization of waste heat generated by the gas storage during the gas injection process has become an urgent problem to be solved. Realizing efficient recovery and utilization of waste heat can not only reduce energy waste, reduce dependence on external energy, reduce energy costs, but also have a positive impact on environmental protection. At present, although some studies have proposed the concept of waste heat recovery, most solutions are still in the theoretical stage, or face challenges such as high cost and low efficiency in practical applications. Therefore, there is an urgent need for a new technical solution to effectively recover and utilize waste heat during the gas injection process of the gas storage, so as to improve the overall energy utilization efficiency, reduce energy consumption, and promote sustainable development.

[0004] The research on the rational recovery of waste heat using thermochemical particulate heat exchange technology has broad prospects. With the growing demand for energy efficiency and environmental protection, particle heat exchange technology is attracting more and more attention from researchers. In the field of energy storage research, solid particles are used as heat storage media to improve the efficiency of heat storage and release. The development of particulate waste heat recovery technology has become mature. The gravity-driven moving bed heat exchanger is a device currently widely used in solid slag waste heat recovery. Compared with traditional heat exchange technology, the gravity-driven moving bed heat exchanger system is simpler. In the moving bed, there are currently two main heat exchange methods: one is the direct heat exchange between air and particles in the moving bed; the other is the heat exchange between particles and heat exchange tubes, and the fluid in the heat exchange tubes can be water or air. Summary of the invention

[0005] In order to overcome the shortcomings of the prior art, the present invention provides a system for efficiently recovering and utilizing waste heat from gas injection in a gas storage reservoir. By utilizing the heat absorption and heat release characteristics during the generation and decomposition of hydrated salts, the natural gas in the gas storage reservoir during the gas injection process can be quickly cooled, and the waste heat can be efficiently recovered and stored for a long time, thereby realizing the cross-seasonal utilization of heat. This technology efficiently recovers the waste heat generated by the gas storage reservoir during the gas injection process through the waste heat recovery system, and is flexibly applied to other process steps to achieve comprehensive utilization of energy and energy saving and consumption reduction.

[0006] The above-mentioned object of the present invention is achieved through the following technical scheme: a gas storage reservoir gas injection waste heat efficient recovery and utilization system, comprising: a moving bed heat exchanger a, connected to the reheater through a flexible screw feeder, the top of the reheater is connected to a high-hydrated salt sealed storage tank, the bottom of the reheater is connected to a low-hydrated salt sealed storage tank through a flexible screw feeder, the high-hydrated salt sealed storage tank, the low-hydrated salt sealed storage tank and the moving bed heat exchanger b are connected through a flexible screw feeder, wherein the moving bed heat exchanger a cools the natural gas, and the moving bed heat exchanger b heats the natural gas.

[0007] Furthermore, a high-temperature dehydrated particle outlet is provided at the bottom of the moving bed heat exchanger a, and a spiral ascending pipeline is provided inside. A high-temperature natural gas inlet a is provided at the end of the lower side pipeline, and a low-temperature natural gas outlet a is provided at the end of the upper side pipeline; a reheated hydrate particle inlet is also provided on the side of the moving bed heat exchanger a, and a hydrated salt particle inlet a is also provided on the top of the moving bed heat exchanger a. The hydrated salt particle inlet a is connected to a high-hydrated salt sealed storage tank by a pipeline. The reheated hydrate particle inlet is connected to the bottom of the reheater through a flexible screw feeder, and the high-temperature dehydrated particle outlet is connected to the top of the reheater through a flexible screw feeder.

[0008] Furthermore, a water vapor outlet is provided at the top of the moving bed heat exchanger a.

[0009] Furthermore, a hydrated salt particle inlet b is provided at the top of the reheater, and the hydrated salt particle inlet b is connected to a high hydrated salt sealed storage tank through a pipeline.

[0010] Furthermore, the composition in the highly hydrated salt sealed storage tank is a mixture of MgSO4·7H2O and CaCl2·6H2O.

[0011] Furthermore, the composition in the low hydrate salt sealed storage tank is a mixture of MgSO4·2H2O and CaCl2·2H2O.

[0012] Furthermore, a low-temperature dehydrated particle inlet is provided at the top of the moving bed heat exchanger b, and the low-temperature dehydrated particle inlet is connected to the low-hydrated salt sealed storage tank through a flexible screw feeder; a hydrated salt particle outlet is provided at the top of the moving bed heat exchanger b, and the hydrated salt particle outlet is connected to the high-hydrated salt sealed storage tank through a flexible screw feeder; a spiral ascending pipeline is provided inside the moving bed heat exchanger b, and a low-temperature natural gas inlet b is provided at the lower side pipeline end, and a high-temperature natural gas outlet b is provided at the upper side pipeline end.

[0013] Furthermore, the moving bed heat exchanger b is provided with a dry air outlet at the bottom and a wet air inlet at the top, a pipeline is provided from the dry air outlet to the wet air inlet, and a steam generator is provided on the pipeline.

[0014] Another object of the present invention is to protect the recycling method of the above-mentioned gas storage reservoir gas injection waste heat efficient recycling system, specifically: on one side, high-temperature natural gas enters the moving bed heat exchanger a, and low-temperature natural gas is discharged. The released heat is discharged to the reheater for storage through high-temperature dehydrated particles. The heat in the reheater is absorbed by the mixture of MgSO4·7H2O and CaCl2·6H2O in the high-hydrated salt sealed storage tank and dehydrated into a mixture of MgSO4·2H2O and CaCl2·2H2O in the low-hydrated salt sealed storage tank; at the same time, on the other side, the mixture of MgSO4·2H2O and CaCl2·2H2O in the low-hydrated salt sealed storage tank combines with water in the moving bed heat exchanger b to form a mixture of MgSO4·7H2O and CaCl2·6H2O in the high-hydrated salt sealed storage tank and releases heat, which is absorbed by the low-temperature natural gas in the moving bed heat exchanger b when it enters and is absorbed when the high-temperature natural gas is discharged, wherein the H2O in the moving bed heat exchanger b is circulated and generated by the steam generator.

[0015] The beneficial effects of the present invention compared with the prior art are: The present invention realizes the efficient recovery, storage and utilization of waste heat in the natural gas injection process through the combination of the screw feeder and various equipment, greatly improving the energy utilization efficiency and reducing energy waste. Compared with traditional air coolers, this technology reduces the floor space and investment costs. At the same time, due to its efficient heat recovery characteristics, it can significantly reduce operating costs. By efficiently recovering waste heat, CO2 emissions are reduced, making a positive contribution to mitigating global warming. This technology supports the long-term storage, cross-season or cross-distance utilization of natural gas waste heat, improves the flexibility and adaptability of the gas storage, can adapt to different operating conditions and needs, and realizes more flexible operation and management.

[0016] The present invention uses a spiral hose feeder to realize the transportation of thermochemical adsorption heat storage medium between the moving bed-large storage tank-small storage tank-well site, saving labor costs. The reheating system used in this solution can preheat a portion of the particles sent to the moving bed heat exchanger, further improving the utilization efficiency of heat. In addition, the system uses a flexible feeder to circulate the particles in the system for heat exchange. The flexible feeder can accurately control the flow rate and speed of the particles, which helps to achieve uniform particle distribution in the heat exchange device, reduce the accumulation and agglomeration of particles in the heat exchange device, improve the operating stability of the system, and ensure the continuous circulation of particles, thereby ensuring the stability and reliability of the heat exchange process.

[0017] According to preliminary calculations, the heat storage cost of this technical solution is only 1.3% of traditional heat storage media such as paraffin. Taking a gas storage reservoir with an annual gas injection volume of 1.5 billion standard cubic meters as an example, the total amount of waste heat is about 90 million kWh. Considering the fluctuations in its operating conditions, the theoretically recoverable waste heat is about 74 million kWh, the total amount of waste heat that can be effectively recovered is 59.2 million kWh (calculated based on a waste heat recovery rate of 80%), and the total amount of waste heat that can be effectively utilized is 47 million kWh (calculated based on a waste heat utilization rate of 80%). If 80% of the waste heat that can be effectively utilized is used to replace natural gas heating and 20% of the waste heat is used to replace electric heating, the annual income can be 11.7 million yuan (calculated based on a natural gas price of 1.68 yuan / standard cubic meter and an electricity fee of 0.52 yuan / kWh), and CO2 emissions can be reduced by about 17,300 tons each year. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. Figure 1 It is a schematic diagram of the structure of the gas storage reservoir gas injection waste heat efficient recovery and utilization system of the present invention.

[0019] In the figure, 1. high-temperature natural gas inlet a; 2. low-temperature natural gas outlet a; 3. moving bed heat exchanger a; 41. hydrated salt particle inlet a; 42. hydrated salt particle inlet b; 5. hydrated salt particle inlet after reheating; 6. high-temperature dehydrated particle outlet; 7. water vapor outlet; 8. flexible screw feeder; 9. reheater; 101. low-hydrated salt sealed storage tank; 102. high-hydrated salt sealed storage tank; 11. moving bed heat exchanger b; 12. low-temperature dehydrated particle inlet; 13. hydrated salt particle outlet; 14. wet air inlet; 15. dry air outlet; 16. low-temperature natural gas inlet b; 17. high-temperature natural gas outlet b; 18. steam generator. DETAILED DESCRIPTION

[0020] The present invention is described in detail below by specific examples, but the protection scope of the present invention is not limited. Unless otherwise specified, the experimental methods used in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can be obtained from commercial channels. Example

[0021] A gas storage reservoir gas injection waste heat efficient recovery and utilization system, comprising: a moving bed heat exchanger a3, connected to a reheater 9 through a flexible screw feeder 8, the top of the reheater 9 is connected to a high hydrated salt sealed storage tank 102, the bottom of the reheater 9 is connected to a low hydrated salt sealed storage tank 101 through a flexible screw feeder 8, the high hydrated salt sealed storage tank 102, the low hydrated salt sealed storage tank 101 and the moving bed heat exchanger b11 are connected through the flexible screw feeder 8, wherein the moving bed heat exchanger a3 cools the natural gas, The moving bed heat exchanger b11 heats natural gas; the moving bed heat exchanger a3 has a spiral upward pipeline inside, and a high-temperature natural gas inlet a1 is provided at the lower side pipeline end, and a low-temperature natural gas outlet a2 is provided at the upper side pipeline end; the moving bed heat exchanger a3 has a high-temperature dehydrated particle outlet 6 at the bottom, and a reheated hydrate particle inlet 5 is also provided on the side of the moving bed heat exchanger a3. The top of the moving bed heat exchanger a3 is also provided with a hydrated salt particle inlet a41, and the hydrated salt particle inlet a41 has a pipe The moving bed heat exchanger a3 is provided with a water vapor outlet 7 at the top; the reheater 9 is provided with a hydrated salt particle inlet b42 at the top, and the hydrated salt particle inlet b42 is connected to the high hydrated salt sealed storage tank 102 by a pipeline; the moving bed heat exchanger b11 has a spiral rising pipe inside. A low-temperature natural gas inlet b16 is provided at the lower side pipeline end, and a high-temperature natural gas outlet b17 is provided at the upper side pipeline end; a low-temperature dehydrated particle inlet 12 is provided at the top of the moving bed heat exchanger b11, and the low-temperature dehydrated particle inlet 12 is connected to the low-hydrated salt sealed storage tank 101 through a flexible screw feeder 8; a hydrated salt particle outlet 13 is provided at the top of the moving bed heat exchanger b11, and the hydrated salt particle outlet 13 is connected to the high-hydrated salt sealed storage tank 102 through a flexible screw feeder 8.

[0022] The composition in the highly hydrated salt sealed storage tank 102 is a mixture of MgSO4·7H2O and CaCl2·6H2O.

[0023] The components in the low hydrate salt sealed storage tank 101 are a mixture of MgSO4·2H2O and CaCl2·2H2O.

[0024] The present invention aims to provide a method of utilizing the endothermic characteristics of the decomposition process of thermochemical granular hydrated salt to absorb waste heat and recover the heat in the form of solid particles. The thermochemical energy storage system utilizes chemical reactions that can absorb or release thermal energy to achieve thermal energy storage and deployment. There are three operating stages: endothermic dissociation → storage of reaction products → exothermic reaction of dissociation products. Taking into account the temperature of compressed natural gas at 60~100 ℃, and the differences in the reaction temperature ranges of different endothermic hydrated salts (such as MgSO4·7H2O is dehydrated at 30~45 ℃ to MgSO4·6H2O, with an endothermic enthalpy of 100 J / g; MgSO4·6H2O is dehydrated at 60~100 ℃ to MgSO4·2H2O, with an endothermic enthalpy of 1000 J / g; CaCl2·6H2O is dehydrated at 30~100 ℃ to CaCl2·2H2O, with an endothermic enthalpy of 1450 J / g), in order to fully recover the waste heat and avoid wasting the waste heat in the low-temperature section, this patent selects a mixture of MgSO4·7H2O and CaCl2·6H2O as a heat storage hydrated salt (the cost required to absorb the same amount of heat is only 1% of that of paraffin). In addition, by mixing MgSO4·7H2O and CaCl2·6H2O, problems such as easy deliquesce of CaCl2·6H2O can be avoided.

[0025] In the heat storage process, high-temperature natural gas and MgSO4·7H2O and CaCl2·6H2O are countercurrently exchanged in a moving bed. MgSO4·7H2O and CaCl2·6H2O dehydrate and absorb heat while heating, and transform into MgSO4·2H2O and CaCl2·2H2O. Subsequently, they are stored in sealed storage tanks suitable for transportation and handling, so as to facilitate the subsequent flexible use of heat across seasons and distances.

[0026] In the process of waste heat utilization, the mixture of MgSO4·2H2O and CaCl2·2H2O is contacted with water vapor to generate MgSO4·7H2O and CaCl2·6H2O, and release a large amount of heat (55~70℃, about 1200 J / g). In the storage process, MgSO4·2H2O and CaCl2·2H2O are placed in a storage tank and sealed to achieve the flexible use of the stored heat in different seasons or distances.

[0027] The high-temperature natural gas generated during the gas injection process in summer exchanges heat with hydrated salt particles (a mixture of MgSO4·7H2O and CaCl2·6H2O) in the moving bed heat exchanger. While cooling the natural gas, MgSO4·7H2O and CaCl2·6H2O are desorbed into MgSO4·2H2O and CaCl2·2H2O, and the heat is stored in the form of chemical energy. In addition, in order to improve the waste heat recovery efficiency, the high-temperature MgSO4·2H2O and CaCl2·2H2O after desorption are used in the reheater 9 to heat part of the low-temperature MgSO4·7H2O and CaCl2·6H2O, and then the reheated hydrated salt is also introduced into the moving bed heat exchanger a3 for heat exchange. The dehydrated particles are then stored in a sealed tank for subsequent cross-season and cross-distance utilization. The dehydrated particles are then stored in sealed tanks. A continuous storage and intermittent transportation system for particles consisting of a large storage tank-flexible screw feeder-container-type small storage tank is constructed. The dehydrated particles are transported to the large storage tank by the flexible screw feeder 8 for storage, thereby realizing continuous operation of the system. After the storage tank is full, the flexible screw feeder 8 is used to load the dehydrated particles into the container storage tank of a large truck and transport them to the well site for waste heat utilization.

[0028] In the process of waste heat utilization in winter, air is sucked in through the steam generator 18 and combined with atomized water to form wet air, which enters the moving bed heat exchanger b11 from the top with a mixture of MgSO4·2H2O and CaCl2·2H2O. MgSO4·2H2O and CaCl2·2H2O come into contact with the wet air to generate MgSO4·7H2O and CaCl2·6H2O, and release a large amount of heat (55~70℃, about 1200 J / g), which is countercurrently exchanged with the low-temperature natural gas entering from the bottom. The natural gas is heated to a high temperature and then leaves the moving bed heat exchanger. After the dry air is discharged from the bottom of the moving bed heat exchanger b11, it returns to the steam generator 18 and is recycled to improve the utilization rate of thermal energy.

[0029] The transportation of particles in the entire system is completed by a flexible screw feeder, which realizes a high degree of automation of the system. It not only greatly reduces labor costs, but also can accurately control the flow and speed of particles, which helps to achieve uniform particle distribution in the heat exchange device, reduce the accumulation and agglomeration of particles in the heat exchange device, improve the operating stability of the system, ensure the continuous circulation of particles, and enhance the heat exchange effect.

[0030] When the gas storage station cannot completely consume the waste heat recovered in summer on site in winter, the recovered waste heat can be transported to the surrounding well sites for cross-distance utilization during the summer gas storage process. The process is as follows: Figure 1As shown. Specifically, a continuous storage and intermittent transportation system for particles consisting of a large storage tank-flexible spiral feeder-container-type small storage tank is constructed. The dehydrated particles are transported to the large storage tank by the flexible spiral feeder for storage, realizing the continuous operation of the system. After the storage tank is full, the dehydrated particles are loaded into the container storage tank of a large truck by the flexible spiral feeder and transported to the well site for waste heat utilization. The continuous recovery of waste heat in the gas storage and the intermittent transportation of particles between the gas storage and the well site are realized, which greatly saves the labor costs required for waste heat recovery, storage and cross-distance utilization.

[0031] The above-described embodiments are only preferred embodiments of the present invention, but not all feasible embodiments of the present invention. For those skilled in the art, any obvious changes made thereto without departing from the principles and spirit of the present invention should be considered to be included in the scope of protection of the claims of the present invention.

Claims

1. A system for efficiently recovering and utilizing waste heat from gas injection in a gas storage facility, characterized in that: include: The moving bed heat exchanger a (3) is connected to the reheater (9) through a flexible screw feeder (8); the top of the reheater (9) is connected to a high hydrated salt sealed storage tank (102); the bottom of the reheater (9) is connected to a low hydrated salt sealed storage tank (101) through a flexible screw feeder (8); the high hydrated salt sealed storage tank (102) and the low hydrated salt sealed storage tank (101) are connected to the moving bed heat exchanger b (11) through a flexible screw feeder (8); the moving bed heat exchanger a (3) cools the natural gas, and the moving bed heat exchanger b (11) heats the natural gas.

2. The gas storage reservoir gas injection waste heat efficient recovery and utilization system according to claim 1 is characterized in that: The moving bed heat exchanger a (3) has a spirally ascending pipeline inside, a high-temperature natural gas inlet a (1) is provided at the lower side pipeline end, and a low-temperature natural gas outlet a (2) is provided at the upper side pipeline end.

3. The gas storage reservoir gas injection waste heat efficient recovery and utilization system according to claim 1 is characterized in that: The bottom of the moving bed heat exchanger a (3) is provided with a high-temperature dehydrated particle outlet (6), the side of the moving bed heat exchanger a (3) is also provided with a reheated hydrated particle inlet (5), the top of the moving bed heat exchanger a (3) is also provided with a hydrated salt particle inlet a (41), the hydrated salt particle inlet a (41) is connected to a high-hydrated salt sealed storage tank (102) through a pipeline, the reheated hydrated particle inlet (5) is connected to the bottom of the reheater (9) through a flexible screw feeder (8), and the high-temperature dehydrated particle outlet (6) is connected to the top of the reheater (9) through a flexible screw feeder (8).

4. The gas storage reservoir gas injection waste heat efficient recovery and utilization system according to claim 1 is characterized in that: The top of the moving bed heat exchanger a (3) is provided with a water vapor outlet (7).

5. The gas storage reservoir gas injection waste heat efficient recovery and utilization system according to claim 1 is characterized in that: A hydrated salt particle inlet b (42) is provided at the top of the reheater (9), and the hydrated salt particle inlet b (42) is connected to a high hydrated salt sealed storage tank (102) through a pipeline.

6. The gas storage reservoir gas injection waste heat efficient recovery and utilization system according to claim 1 is characterized in that: The composition in the highly hydrated salt sealed storage tank (102) is a mixture of MgSO4·7H2O and CaCl2·6H2O.

7. The gas storage reservoir gas injection waste heat efficient recovery and utilization system according to claim 1 is characterized in that: The components in the low hydrate salt sealed storage tank (101) are a mixture of MgSO4·2H2O and CaCl2·2H2O.

8. The gas storage reservoir gas injection waste heat efficient recovery and utilization system according to claim 1 is characterized in that: The moving bed heat exchanger b (11) has a spirally ascending pipeline inside, a low-temperature natural gas inlet b (16) is provided at the lower side pipeline end, and a high-temperature natural gas outlet b (17) is provided at the upper side pipeline end.

9. The gas storage reservoir gas injection waste heat efficient recovery and utilization system according to claim 1 is characterized in that: The top of the moving bed heat exchanger b (11) is provided with a low-temperature dehydrated particle inlet (12), which is connected to a low-hydrated salt sealed storage tank (101) via a flexible screw feeder (8); the top of the moving bed heat exchanger b (11) is provided with a hydrated salt particle outlet (13), which is connected to a high-hydrated salt sealed storage tank (102) via a flexible screw feeder (8).

10. The gas storage reservoir gas injection waste heat efficient recovery and utilization system according to claim 1, characterized in that: The moving bed heat exchanger b (11) is provided with a dry air outlet (15) at the bottom and a wet air inlet (14) at the top. A pipeline is provided from the dry air outlet (15) to the wet air inlet (14), and a steam generator (18) is provided on the pipeline.

11. The method for efficiently recovering and utilizing waste heat from gas injection in a gas storage reservoir according to claim 10, characterized in that: The specific steps are as follows: high-temperature natural gas enters the moving bed heat exchanger a (3) and low-temperature natural gas is discharged. The released heat is discharged to the reheater (9) through high-temperature dehydrated particles for storage. The heat in the reheater (9) is absorbed by the mixture of MgSO4·7H2O and CaCl2·6H2O in the high-hydrated salt sealed storage tank (102) for dehydration into a mixture of MgSO4·2H2O and CaCl2·2H2O in the low-hydrated salt sealed storage tank (101); at the same time, the low-hydrated salt is discharged from the moving bed heat exchanger a (3). The mixture of MgSO4·2H2O and CaCl2·2H2O in the salt sealed storage tank (101) combines with water in the moving bed heat exchanger b (11) to form a mixture of MgSO4·7H2O and CaCl2·6H2O in the highly hydrated salt sealed storage tank (102) and releases heat, which is supplied to the low-temperature natural gas in the moving bed heat exchanger b (11) and absorbed when the high-temperature natural gas is discharged, wherein the H2O in the moving bed heat exchanger b (11) is circulated and generated by the steam generator (18).

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