Combustible industrial tail gas coupling adiabatic compressed air energy storage system

Abstract

The invention relates to the technical field of compressed air energy storage, in particular to a combustible industrial tail gas coupling adiabatic compressed air energy storage system which comprises an adiabatic compression energy storage module, an adiabatic compression heat recovery module, a fused salt heating and heat storage module and a high-temperature expansion power generation module. The adiabatic compression energy storage module achieves multi-section compression of air and stores compression heat in the adiabatic compression heat recovery module, and the molten salt heating heat storage module combusts combustible industrial tail gas in a molten salt heating furnace and stores combustion heat. The high-temperature expansion power generation module receives combustion heat provided by the fused salt heating heat storage module and compression heat stored by the adiabatic compression heat recovery module, and compressed gas expansion power generation is completed; the low-ebb-period electric energy and the combustible industrial tail gas heat energy are fully utilized, coupling of the industrial combustible tail gas and the compressed air energy storage system is achieved, the quality of compressed air at an inlet of the expansion machine is greatly improved, the problem of insufficient preheating of the compressed air in the expansion energy release process is solved, and the electricity-electricity conversion efficiency of the compressed air system is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of compressed air energy storage, and in particular to a combustible industrial tail gas coupled adiabatic compressed air energy storage system. Background Art

[0002] Compressed air energy storage technology refers to a storage method that uses electrical energy to compress air during the low load period of the power grid, seals the air at high pressure in abandoned salt caverns, mines, sunken seabed gas storage containers, caves, expired oil and gas wells or newly built gas storage wells, and releases the compressed air to drive the expander to generate electricity during the peak load period of the power grid.

[0003] The engineering practice research on compressed air energy storage technology in my country mainly focuses on the research of adiabatic non-supplementary compressed air energy storage technology. An adiabatic non-supplementary compressed air energy storage system refers to a compressed air energy storage system that does not require an external heat source when working. The system relies on storing heat energy in the compression stage and then uses it to heat the high-pressure air entering each section of the expander in the expansion stage to improve the system's electric-to-electric conversion efficiency.

[0004] At present, the domestic compressed air energy storage market generally adopts the adiabatic non-supplementary compressed air energy storage technology solution. This technical solution is implemented as follows: when storing energy, the low-valley electricity drive motor drives the compressor, and the compressor outlet gas is input into the gas storage container for storage after heat exchange, and the compressed heat energy is stored in the high-temperature storage tank by the heat storage medium; when releasing energy, the stored compressed air is heated by the reheater to form high-temperature and high-pressure gas, which enters the expander to work and drives the generator to generate electricity and send it to the power grid. The advantage of this method is that it can transmit stable electricity to the power grid by controlling the work of the expander, but its disadvantage is that there is a certain amount of heat energy loss in the storage and release and heat exchange of the compression heat, resulting in the quality of the compressed air entering the expander is not high, thus affecting the efficiency of the compressed air energy storage technology.

[0005] Industrial production emits combustible gases into the atmosphere, mainly referring to gases generated in the production process of petrochemical, chemical, coal mining and other industries. These gases are used as flare gases or directly discharged, which will cause environmental pollution and energy waste. With the continuous adjustment of the energy structure, how to reasonably and high-value recycle unconventional combustible industrial tail gases such as coking tail gas, blast furnace gas, biomass gas and industrial tail gas is an important issue in the energy field. These process combustible tail gases such as blast furnace tail gas and petroleum refining industrial tail gas are mostly hydrogen-rich fuel gases (for example, the hydrogen volume content of the industrial combustible tail gas of a certain petroleum refinery is 64.98%, which cannot be directly used by industrial gas turbines / internal combustion engines). They have limited utilization methods and low utilization value.

[0006] In the prior art, the utility model with patent publication number CN 220870963 U discloses a multi-energy cogeneration system including energy storage. It mainly solves the regional cooling, heating, electricity and other energy supply needs by coupling the compressed air energy storage system with the regional cooling and heating needs, and achieves the technical problems of reducing the operating costs of cooling and heating and low heat / pressure decoupling. However, the adiabatic compression technology solution used in its compressed air energy storage has a low compression calorific value, which in turn affects the electricity-to-electricity conversion efficiency during the expansion power generation process. Summary of the invention

[0007] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to propose a combustible industrial exhaust gas coupled with an adiabatic compressed air energy storage system, which stores low-period electrical energy in compressed gas through adiabatic compression, and couples the combustion heat of the combustible industrial exhaust gas in the molten salt heating furnace and the compression heat generated by adiabatic compression, which are used for heating and power generation of the expansion unit; the present invention makes full use of the combustible industrial exhaust gas and the compression heat generated by adiabatic compression, thereby improving the energy utilization rate of the compressed energy storage system as a whole.

[0008] A combustible industrial tail gas coupled with an adiabatic compressed air energy storage system comprises an adiabatic compression energy storage module, an adiabatic compression heat recovery module, a molten salt heating heat storage module, and a high-temperature expansion power generation module. The adiabatic compression energy storage module utilizes low-valley electricity to achieve multi-stage air compression and converts the electricity into internal energy and stores it in compressed gas. The adiabatic compression heat recovery module is used to recover and store the compression heat generated when the air in the adiabatic compression energy storage module is compressed in multiple stages. The molten salt heating heat storage module burns the combustible industrial tail gas in a molten salt heating furnace and stores the combustion heat, and transfers the combustion heat to the high-temperature expansion power generation module when needed. The high-temperature expansion power generation module receives the combustion heat provided by the molten salt heating heat storage module and the compression heat provided by the adiabatic compression heat recovery module to complete the compressed gas expansion power generation.

[0009] Furthermore, the adiabatic compression energy storage module comprises an nth (n=1, 2, ..., n)th compressor unit, a qth (q=1, 2, ..., n-1)th heat exchange unit, a cooling unit, an air storage unit and an intake pipe, each compressor unit comprises a compressor unit and a motor, each compressor unit comprises an sth (s=1, 2, ..., s)th compressor, each compressor of each compressor unit is axially connected in series, and the motor is connected to the compressor to realize the air boosting function; the outside air passes through the first compressor unit, the first heat exchange unit, the second compressor unit, the second heat exchange unit, ..., the n-1 heat exchange unit, the nth compressor unit, and the cooling unit in sequence through the intake pipe, and finally enters the air storage unit to realize air compression and storage; the qth (q=1, 2, ..., n-1)th heat exchange unit comprises a heat exchanger to realize the recovery and utilization of the compression heat generated by each compressor unit; the cooling unit comprises a cooler to realize the cooling and regulation of the compression heat generated by the nth compressor unit; the air storage unit comprises an air storage container.

[0010] Furthermore, the adiabatic compression heat recovery module includes a medium-temperature water cooling tank, a medium-temperature water hot tank, the mth (m=1, 2, ..., m)th medium-temperature water heat exchange unit and a medium-temperature water pipe. The medium-temperature water cooling tank is connected to the qth (q=1, 2, ..., n-1)th heat exchange unit, the medium-temperature water hot tank and the mth (m=1, 2, ..., m)th medium-temperature water heat exchange unit in sequence through the medium-temperature water pipe to form a closed loop. The qth (q=1, 2, ..., n-1)th heat exchange unit in the adiabatic compression energy storage module is connected in parallel with the medium-temperature water cooling tank and the medium-temperature water hot tank through the medium-temperature water pipe. The condensed water in the medium-temperature water cooling tank exchanges heat with the qth (q=1, 2, ..., n-1)th heat exchange unit under the action of pump pressure through the medium-temperature water pipe and then enters the medium-temperature water hot tank for heat storage; each section of the medium-temperature water heat exchange units is connected in parallel.

[0011] Furthermore, the molten salt heating and heat storage module includes a molten salt heating furnace, a high-temperature molten salt tank, an mth (m=1, 2, ..., m)th molten salt heat exchange unit, a low-temperature molten salt tank and a molten salt pipeline, the molten salt pipeline sequentially connects the molten salt heating furnace, the high-temperature molten salt tank, the mth (m=1, 2, ..., m)th molten salt heat exchange unit and the low-temperature molten salt tank to form a closed loop, and each section of the molten salt heat exchange units is connected in parallel; the combustible industrial tail gas enters the molten salt heating furnace to burn and heat the molten salt from the low-temperature molten salt tank, and the molten salt enters the high-temperature molten salt tank after the temperature is increased to realize heat storage, and the molten salt in the high-temperature molten salt tank enters the low-temperature molten salt tank after heat exchange with the high-temperature expansion power generation module through the mth (m=1, 2, ..., m)th molten salt heat exchange unit.

[0012] Furthermore, the high-temperature expansion power generation module comprises an mth (m=1, 2, ..., m)th expansion machine unit, a generator and an outlet pipe, each expansion machine unit comprises an expansion machine group, and the expansion machine group is connected to the generator; the outlet pipe is connected in sequence to the gas storage unit, the first section medium-temperature water heat exchange unit, the first section molten salt heat exchange unit, the first section expansion machine unit, ..., the mth section medium-temperature water heat exchange unit, the mth section molten salt heat exchange unit, and the mth section expansion machine unit; the compressed air can be heated and expanded to do work in one of the following two ways: (1) the compressed air in the gas storage unit passes through the mth (m=1, 2, ..., m)th section medium-temperature water heat exchange unit and the mth (m=1, 2, ..., m)th section molten salt heat exchange unit in sequence through the outlet pipe, and then enters the mth (m=1, 2, ..., m)th section medium-temperature water heat exchange unit. The compressed air discharged from each expansion unit enters the next medium-temperature water heat exchange unit again, and the cycle continues. The compressed air is finally discharged from the outlet of the mth expansion unit; (2) The compressed air in the gas storage unit passes through the first medium-temperature water heat exchange unit and the first molten salt heat exchange unit through the outlet pipe, and then enters the first expansion unit for heating, driving the generator to generate electricity. The compressed air discharged from the first expansion unit for heating is heated by the mth (m=2, ..., m)th molten salt heat exchange unit, and then enters the mth (m=2, ..., m)th expansion unit for heating. The compressed air discharged from each expansion unit enters the next molten salt heat exchange unit again, and the cycle continues. The compressed air is finally discharged from the outlet of the mth expansion unit.

[0013] Furthermore, the number of stages n of the nth (n=1, 2, ..., n) compressor unit is 3-8, the outlet air temperature of the nth (n=1, 2, ..., n) compressor unit is 150-250°C, and the inlet air temperature of the nth (n=2, 3, ..., n) compressor unit or air storage unit is 30-50°C.

[0014] Furthermore, the water storage temperature of the medium-temperature water cooling tank is 20-30°C, and the water storage temperature of the medium-temperature water heating tank is 135-235°C.

[0015] Furthermore, the operating temperature of the molten salt used in the molten salt heating furnace is not higher than 565° C., and the industrial combustible tail gas used in the molten salt heating heat storage module is hydrogen-rich gas, and the volume content of hydrogen in the hydrogen-rich gas is greater than 40%.

[0016] Furthermore, the number of sections m of the mth (m=1, 2, ..., m) expansion machine units is 2-5.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. Compared with the isothermal compression method, the adiabatic compression method in the adiabatic compression energy storage module can significantly increase the compression heat through the multi-stage setting of the compression unit and the multi-stage compressor setting in each compression unit, raising the compressed air temperature to 180-200°C, and storing it through the adiabatic compression heat recovery module for high-temperature expansion power generation, making full use of the low-peak period electricity to complete energy storage.

[0019] 2. The molten salt heating and heat storage module makes full use of waste combustible industrial exhaust gas, stores the waste energy through molten salt heating, and uses it to preheat the air before high-temperature expansion power generation, effectively achieving energy conservation and environmental protection.

[0020] 3. The present invention couples the process flow in the adiabatic compression energy storage module, the adiabatic compression heat recovery module, the molten salt heating heat storage module, and the high-temperature expansion power generation module to fully realize the separate storage and distribution of low-peak electricity and combustible industrial tail gas, and has a high electricity-to-electricity conversion efficiency.

[0021] In summary, the present invention makes full use of off-peak electricity and combustible industrial exhaust thermal energy, realizes the perfect coupling of waste energy in industrial processes with the compressed air energy storage system, greatly improves the quality of compressed air at the expander inlet, solves the problem of insufficient preheating of compressed air during expansion energy release, and improves the electric-to-electric conversion efficiency of the compressed air system. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the combustible industrial tail gas coupled adiabatic compressed air energy storage system of the present invention. DETAILED DESCRIPTION

[0023] Combine the following Figure 1 The present invention is described in further detail:

[0024] like Figure 1 As shown, a combustible industrial tail gas coupled with an adiabatic compressed air energy storage system comprises an adiabatic compression energy storage module, an adiabatic compression heat recovery module, a molten salt heating heat storage module, and a high-temperature expansion power generation module. The adiabatic compression energy storage module utilizes low-period electric energy to realize multi-stage air compression and converts the electric energy into internal energy and stores it in compressed gas. The adiabatic compression heat recovery module is used to recover and store the compression heat generated during the multi-stage compression of the air in the adiabatic compression energy storage module. The molten salt heating heat storage module burns the combustible industrial tail gas in a molten salt heating furnace and stores the combustion heat, and transfers the combustion heat to the high-temperature expansion power generation module when needed. The high-temperature expansion power generation module receives the combustion heat provided by the molten salt heating heat storage module and the compression heat provided by the adiabatic compression heat recovery module to complete the compressed gas expansion power generation.

[0025] Furthermore, the adiabatic compression energy storage module comprises an nth (n=1, 2, ..., n)th compressor unit, a qth (q=1, 2, ..., n-1)th heat exchange unit, a cooling unit, an air storage unit and an intake pipe, each compressor unit comprises a compressor unit and a motor, each compressor unit comprises an sth (s=1, 2, ..., s)th compressor, each compressor of each compressor unit is axially connected in series, and the motor is connected to the compressor to realize the air boosting function; the outside air passes through the first compressor unit, the first heat exchange unit, the second compressor unit, the second heat exchange unit, ..., the n-1 heat exchange unit, the nth compressor unit, and the cooling unit in sequence through the intake pipe, and finally enters the air storage unit to realize air compression and storage; during the adiabatic compression process, there is no heat exchange inside each compressor unit, and the compression heat generation efficiency is high , compact structure; the qth (q=1, 2, ..., n-1) heat exchange unit comprises a heat exchanger, and the compression heat generated by the compressed air of each compressor unit is transferred to the adiabatic compression heat recovery module through each heat exchange unit directly connected thereto, so as to realize the recovery and utilization of the compression heat generated by each compressor unit; the cooling unit comprises a cooler, so as to realize the cooling and regulation of the compression heat generated by the nth compressor unit; the gas storage unit comprises a gas storage container, and the gas storage container is used to store the high-pressure gas generated by the compressor unit, and its form is divided into above-ground gas storage containers (including steel storage tanks, pipeline steel, etc.) and underground gas storage containers (including underground salt caverns, artificial chambers, etc.). The gas storage container is determined according to the project scale and the actual conditions of the location. The gas storage pressure bearing capacity of the gas storage container is higher than the pressure of the stored compressed air, and a certain design margin is considered.

[0026] Furthermore, the number of stages n of the nth (n=1, 2, ..., n) compressor unit is 3-8, the outlet air temperature of the nth (n=1, 2, ..., n) compressor unit is 150-250°C, and the inlet air temperature of the nth (n=2, 3, ..., n) compressor unit or air storage unit is 30-50°C.

[0027] The adiabatic compression energy storage module is used to realize the function of air compression and storage. In order to ensure the realization of adiabatic compression, each compressor unit is generally connected in series. The number n of the nth (n = 1, 2, ..., n) compressor units is determined according to the storage pressure level flow rate of the system design. n is generally 3-8 stages. Each compressor in each compressor unit can be an axial compressor or a centrifugal compressor. The number of axial compressor stages is 3-7, and the number of centrifugal compressor stages is 10-20; the outlet air temperature of each compressor unit is controlled between 150-250℃; except for the nth compressor, the outlet air temperature of each compressor unit is controlled between 150-250℃. The outlet air temperature of each compressor unit outside the unit is controlled between 150-250℃, and the temperature difference is not more than 10℃. The high-pressure air at the outlet of each compressor unit is heat exchanged by each heat exchange unit connected to it to ensure that the inlet air temperature of the next compressor unit drops to 30-50℃. Since the pressure change of the air storage unit causes the back pressure change, the flow rate of the nth compressor unit is designed to be adjustable. The outlet compressed air temperature of the nth compressor unit changes according to the flow conditions (generally below 250℃). The compressed air enters the air storage unit after being reduced to 30-50℃ through the cooler.

[0028] At the same time, in order to ensure that the inlet air temperature of each compressor unit except the first compressor unit is around 30-50°C, a heat exchange unit is set before the inlet of each compressor unit (except the first compressor unit); each heat exchange unit includes a heat exchanger, generally a multi-stage air-water heat exchanger is used to recover the compression heat of the air at the outlet of each compressor unit, reduce the inlet air temperature of the next compressor unit, and reduce the compression power consumption.

[0029] Furthermore, the adiabatic compression heat recovery module comprises a medium-temperature water cooling tank, a medium-temperature water hot tank, an mth (m=1, 2, ..., m)th medium-temperature water heat exchange unit and a medium-temperature water pipe. Generally, the value of m in the mth (m=1, 2, ..., m)th medium-temperature water heat exchange unit is 2; the medium-temperature water cooling tank is connected to the qth (q=1, 2, ..., n-1)th heat exchange unit, the medium-temperature water hot tank and the mth (m=1, 2, ..., m)th medium-temperature water heat exchange unit in sequence through the medium-temperature water pipe to form a closed loop. The qth (q=1 , 2, ..., n-1)-th heat exchange unit is connected in parallel with the medium-temperature water cooling tank and the medium-temperature water hot tank through a medium-temperature water pipe. Under the action of pump pressure, the condensed water in the medium-temperature water cooling tank passes through the medium-temperature water pipe and exchanges heat with the qth (q=1, 2, ..., n-1)-th heat exchange unit and then enters the medium-temperature water hot tank for heat storage; each section of the medium-temperature water heat exchange units is connected in parallel; when the high-temperature expansion power generation module needs it, the hot water in the medium-temperature water hot tank passes through the mth (m=1, 2, ..., m)-th medium-temperature water heat exchange unit for heat exchange with the high-temperature expansion power generation module and then enters the medium-temperature water cooling tank.

[0030] Furthermore, the water storage temperature of the medium-temperature water cooling tank is 20-30°C. The low-temperature condensed water in the medium-temperature water cooling tank is increased to 135-235°C after heat exchange with the qth (q=1, 2, ..., n-1) heat exchange unit and enters the medium-temperature water heating tank for storage.

[0031] The pressure and temperature of the compressed air after being compressed by the nth (n=1, 2, ..., n-1)th compressor unit increase. Before entering the next compressor unit, it is first heat exchanged through the corresponding heat exchange unit, so that the heat in the compressed air can be transferred to the low-temperature condensate from the medium-temperature water cooling tank. Specifically, the storage temperature of the low-temperature condensate in the medium-temperature water cooling tank is generally 20-30°C. The medium-temperature water cooling tank transports the low-temperature condensate to the qth (q=1, 2, ..., n-1)th heat exchange unit through a high-pressure water pump, and exchanges heat with the corresponding medium-temperature and high-pressure air (generally 150-250°C) at the outlet of the nth (n=1, 2, ..., n-1)th compressor unit. The temperature of the low-temperature condensate rises to 135-235°C and enters the medium-temperature water tank for storage. The low-temperature condensate in the heat exchange unit cools the compressed air to 30-50°C and enters the next compressor unit or the air storage unit.

[0032] Furthermore, the molten salt heating and heat storage module includes a molten salt heating furnace, a high-temperature molten salt tank, an mth (m=1, 2, ..., m) section molten salt heat exchange unit, a low-temperature molten salt tank and a molten salt pipeline, the molten salt pipeline sequentially connects the molten salt heating furnace, the high-temperature molten salt tank, the mth (m=1, 2, ..., m) section molten salt heat exchange unit and the low-temperature molten salt tank to form a closed loop, and each section of the molten salt heat exchange units is connected in parallel; the combustible industrial tail gas from the industrial process enters the molten salt heating furnace for combustion, and the heat generated by the combustion heats the low-temperature molten salt from the low-temperature molten salt tank, and the high-temperature molten salt formed after the low-temperature molten salt is heated enters the high-temperature molten salt tank to realize heat storage; when the high-temperature expansion power generation module needs it, the high-temperature molten salt in the high-temperature molten salt tank enters the low-temperature molten salt tank after heat exchange with the high-temperature expansion power generation module through the mth (m=1, 2, ..., m) section molten salt heat exchange unit.

[0033] Furthermore, the operating temperature of the molten salt used in the molten salt heating furnace is not higher than 565°C; specifically, it is a binary molten salt or a ternary molten salt. The operating temperature of the binary molten salt after heating is not higher than 565°C, and the operating temperature of the ternary molten salt after heating is not higher than 420°C. The industrial combustible tail gas used in the molten salt heating heat storage module is hydrogen-rich gas, and the hydrogen volume content in the hydrogen-rich gas is greater than 40%.

[0034] The molten salt heating heat storage module pumps low-temperature molten salt into the molten salt heating furnace through a molten salt pump. The low-temperature molten salt is heated by burning industrial combustible tail gas and then enters the high-temperature molten salt tank for storage. The high-temperature flue gas discharged from the industrial combustible tail gas entering the molten salt heating furnace is preheated by an air preheater and a gas preheater respectively, and the gas exhaust temperature is reduced to below 100°C, thereby improving the overall energy utilization efficiency.

[0035] In order to ensure the stable operation of the main process of industrial process users and the stable consumption of combustible industrial tail gas, the molten salt heating furnace operates 24 hours a day, the expansion power generation time of the high-temperature expansion power generation module is s hours / day, and the ratio of the molten salt flow rate (kg / s) of the molten salt heating furnace and the molten salt heat exchange unit flow rate (kg / s) is: s / 24. According to different project requirements, the molten salt heating and heat storage module can select binary molten salt or ternary molten salt as the heat storage medium, among which the working range of binary molten salt is 280-565℃, and the working range of ternary molten salt is 180-420℃. The inlet temperature of the expansion unit needs to be given according to the project and the selected equipment, generally in the range of 300-565℃.

[0036] Furthermore, the high-temperature expansion power generation module includes an mth (m=1, 2, ..., m) expansion machine unit, a generator and an outlet pipe, each expansion machine unit includes an expansion machine group, the expansion machine group is connected to the generator, and the outlet pipe is connected in sequence to the gas storage unit, the first-stage medium-temperature water heat exchange unit, the first-stage molten salt heat exchange unit, the first-stage expansion machine unit, the second-stage medium-temperature water heat exchange unit, the second-stage molten salt heat exchange unit, the second-stage expansion machine unit, ..., the mth medium-temperature water heat exchange unit, the mth molten salt heat exchange unit, and the mth expansion machine unit.

[0037] The compressed air can be heated and expanded to perform work in the following two ways: (1) The compressed air in the gas storage unit passes through the outlet pipe in turn through the mth (m=1, 2, ..., m) section medium-temperature water heat exchange unit and the mth (m=1, 2, ..., m) section molten salt heat exchange unit for heating, and then enters the mth (m=1, 2, ..., m) section expansion unit for heating, thereby driving the generator to generate electricity. The compressed air discharged from each expansion unit enters the next section medium-temperature water heat exchange unit again, and the cycle is repeated in sequence. The compressed air is finally discharged from the outlet of the mth section expansion unit; (2) The compressed air in the gas storage unit passes through the outlet pipe in turn through the 1st section medium-temperature water heat exchange unit and the 1st section molten salt heat exchange unit for heating, and then enters the 1st section expansion unit for heating, thereby driving the generator to generate electricity. The motor generates electricity, and the compressed air discharged from the first expansion unit is heated by the mth (m=2, ..., m)th molten salt heat exchange unit and then enters the mth (m=2, ..., m)th expansion unit to do work. The compressed air discharged from each expansion unit enters the next molten salt heat exchange unit again, and circulates in sequence. The compressed air is finally discharged from the outlet of the mth expansion unit; the compressed air is heated, cooled by work, reheated to do work, and finally discharged from the outlet of the mth expansion unit through a continuous cycle, thereby realizing the power generation function of the high-temperature expansion power generation module; usually, the temperature of the compressed air discharged from the first expansion unit is below 150°C, and it can be chosen not to pass through the subsequent medium-temperature water heat exchange unit but to be directly heated by the molten salt heat exchange unit.

[0038] Specifically, during the high-temperature expansion power generation process, the 30-50°C low-temperature compressed air in the gas storage unit passes through the control valve and the air outlet pipe and enters the first section medium-temperature water heat exchange unit (i.e., water-gas heat exchanger), and the temperature of the compressed air is increased to 135-235°C, and then passes through the first section molten salt heat exchange unit (i.e., molten salt heat exchanger) and the temperature is increased again to a high-temperature range of 280-535°C (the specific temperature range will be set in advance). The compressed air after the two temperature increases enters the first section expander unit (i.e., expansion unit) to do work, thereby improving the work capacity of the expansion unit; the temperature and pressure of the air that has done work in the first section expander unit are reduced (generally to below 150°C), and then after the temperature is increased through the second section medium-temperature water heat exchange unit (or not) and the second section molten salt heat exchange unit (molten salt heat exchanger), the second section expander unit is driven to do work and generate electricity, and the temperature and pressure of the air output from the output end of the second section expander unit are further reduced after doing work, and the compressed air is continuously circulated for heating, cooling down, and reheating.

[0039] Furthermore, generally, the process involves an m-th (m=1, 2, ..., m) expansion machine unit with a stage number m of 2-5; after multiple stages of expansion and work, the air temperature and pressure are reduced to the discharge conditions and then discharged directly.

[0040] The condensed water in the adiabatic compression heat recovery module releases heat through each section of the medium-temperature water heat exchange unit and enters the medium-temperature water cooling tank, and is pumped into each section of the heat exchange unit again to absorb compression heat and is stored in the medium-temperature water hot tank, forming a cycle; the molten salt in the molten salt heating heat storage module releases heat and enters the low-temperature molten salt tank, and is pumped into the molten salt heating furnace again for heating and then stored in the high-temperature molten salt tank, forming a cycle.

[0041] Embodiment 1

[0042] In this embodiment, a compressed air energy storage project with an expansion power generation capacity of 30MW is selected. The operation mode of the project is set to compress and store energy for 8 hours per cycle, expand and release energy for 8 hours, and compress the gas storage pressure to 3-10MPa, and the expansion release pressure to 6MPa. In this embodiment, the compressed air energy storage system is mainly divided into three processes during operation: compression energy storage, molten salt heating heat storage, and energy release.

[0043] Compression energy storage process: The compressor is driven by valley electricity, and the air is compressed to a high-pressure state through multiple stages of compression and stored in a gas storage device. The compression heat generated during the compression process is stored through an adiabatic compression heat recovery module. This solution uses a four-stage adiabatic compressor unit, with a compressor unit outlet pressure of 10.5MPa at the end and an exhaust temperature of 40°C.

[0044] Molten salt heating and heat storage process: The high-temperature molten salt heat storage and exchange system consists of a molten salt heating furnace, a low-temperature molten salt tank, a high-temperature molten salt tank, a molten salt heat exchange unit, etc. The working fluid pump drives the heat storage medium, i.e., molten salt, to circulate in the molten salt heating and heat storage module; the heat storage medium is heated in the molten salt heating furnace by introducing hydrogen-rich gas, and the low-temperature molten salt is heated to 375°C and then stored in the high-temperature heat storage tank. After the molten salt heat exchange unit heats the high-pressure air that has been heated to 170°C by medium-temperature water to 350°C, the molten salt is reduced from 375°C to 185°C and enters the low-temperature molten salt tank.

[0045] Energy release process: High-pressure air is released from the gas storage container, and the heat stored in the adiabatic compression heat recovery module and the molten salt heating heat storage module is heated to 350°C before entering the turbine to expand and do work. After expansion and work, the pressure and temperature of the air are reduced to 105°C, and it needs to be heated again to 350°C by the heat stored in the adiabatic compression heat recovery module and the molten salt heating heat storage module, and then enter the next level of turbine to do work and complete expansion and power generation. In this process, the three energies of pressure potential energy, compression heat energy, and combustible industrial exhaust combustion heat energy are coupled to drive the turbine to generate electricity, realizing the coupled energy release power generation of the system.

[0046] The main calculation process of energy conversion in Example 1 is as follows:

[0047] (1) Multi-stage compressor unit parameters

[0048] In the first embodiment, the adiabatic compression energy storage module adopts a multi-combination compressor unit, and the total power of the four-stage compressor unit is 38MW; it is completed by a set of four-stage compressor units connected in series, the outlet pressure of the last stage compressor unit is 10.5MPa, and the exhaust temperature of the first three stages is 200°C; after heat exchange with the multi-stage heat exchange unit and the cooling unit, the high-pressure compressed air is stored in the air storage container at a pressure of 10.5MPa and a temperature of 40°C. The parameters of the multi-stage compressor unit are shown in Table 1:

[0049] Table 1 Multi-stage compressor unit parameters

[0050]

[0051]

[0052] (2) Multi-stage expander unit parameters

[0053] In the first embodiment, the high-temperature expansion power generation module is set with two stages of reheating and two stages of expansion. Each stage of reheating undergoes two stages of heat exchange and temperature rise. The compressed air (air temperature 40°C, pressure 6.06MPa) coming out of the gas storage unit absorbs the compression heat transmitted by the first stage heat exchange unit to heat the air to 170°C, and then passes through the first stage molten salt heat exchange unit to heat the air to 350°C, and enters the first stage expander unit for expansion and power generation. The compressed air temperature drops to 105°C, and then absorbs the compression heat transmitted by the second stage heat exchange unit again and heats up to 350°C in the second stage molten salt heat exchange unit, and finally enters the second stage expander unit for expansion and power generation. The parameters of the multi-stage expander unit are shown in Table 2:

[0054] Table 2 Multi-stage expander unit (turbine unit) parameter table

[0055]

[0056] (3) Heat storage and heat exchange process parameters

[0057] This embodiment 1 has two sets of heat storage and heat exchange modules, namely, an adiabatic compression heat recovery module and a molten salt heating heat storage module.

[0058] 1) Adiabatic compression heat recovery module

[0059] 1. Workflow

[0060] The adiabatic compression heat recovery module is mainly used to recover compression heat, and to first heat the low-temperature compressed air at the inlet of the two-stage expansion unit during the energy release process; this embodiment 1 adopts a 185°C adiabatic compression heat recovery module, and the compressed air at the outlet of each compressor unit in the compression section is about 200°C. After entering the medium-temperature water heat exchange unit, the compressed air is reduced to 40°C, and the medium-temperature water is heated to 185°C; expansion section heat exchange: the inlet air temperature of the first section expansion unit before heat exchange is 40°C, and the air temperature at the outlet of the first section expansion unit, i.e. the inlet of the second section, is 105°C, and both are heated to 170°C through medium-temperature water heat exchange.

[0061] 2. Heat can be stored during compression

[0062] According to the adiabatic compressed air energy storage system, the compression heat of the last compressor unit is not recovered, and only the compression heat of the first three stages is recovered. The compression heat parameters are shown in Table 3:

[0063] Table 3 Compression heat parameters of adiabatic compression energy storage module

[0064]

[0065] The total heat storage during the compression process is calculated as follows:

[0066] M1=Q1×h1(1)

[0067] In formula (1), M1 represents the total heat of the compression process, kWh; Q1 represents the power of the compression process, kW; h1 represents the compression time, h.

[0068] Among them, the calculation formula of compression process power Q1 is as follows:

[0069] Q=C P ×(T2-T1)×q(2)

[0070] In formula (2), Q represents the required heat, kJ; C P represents the specific heat of gas, KJ·(K·kg); T2-T1 represents the temperature rise, K; q represents the gas flow rate, Kg / s.

[0071] According to calculation, the total heat that can be stored in the compression process is M1=Q1×h1=(10517.43+10846.1+10885.54)×8=257992.6kWh.

[0072] 3 Utilization of compression heat during the first stage of expansion:

[0073] The main compression heat utilization of the first expansion process is two reheat processes: (1) The air temperature at the outlet of the gas storage unit, i.e. the inlet air temperature of the first expansion unit before heat exchange is 40°C; (2) The air temperature at the outlet of the first expansion unit, i.e. the inlet air temperature of the second expansion unit, is 105°C; both are heated to 170°C through medium-temperature water storage compression heat exchange. The compression heat utilization in the expansion power generation stage is shown in Table 4:

[0074] Table 4 Parameters of compression heat utilization in expansion power generation stage

[0075]

[0076] The total heat of compression absorbed during the first expansion process is calculated as follows:

[0077] M2=Q2×h2(3)

[0078] In formula (3), M2 represents the total heat of the first stage expansion absorption compression heat, kWh; Q2 represents the first stage expansion absorption compression power, kW; h2 represents the first stage expansion time, h.

[0079] After calculation, the total heat absorbed by the compression heat of the first expansion stage is M2=Q2×h2=(8545.414+4272.707)×8=102545kWh.

[0080] 4Compression heat surplus

[0081] The total heat of excess compression is calculated as follows:

[0082] M3=M1-M2 / η2(4)

[0083] In formula (4), M3 represents the total surplus compression heat in the compression heat cycle, kWh; η2 represents the total heat transfer coefficient of the medium-temperature water storage, which is 0.8.

[0084] After calculation, the total surplus compression heat in the compression heat cycle is M3=M1-M2 / η2=257992.6-102545÷0.8=129811.4kWh.

[0085] In the first embodiment, a certain amount of medium-temperature heat source is available, which can be used in process flows with heat demand, such as heating process condensate and preheating process medium, etc. In addition, it can also provide heat to surrounding areas.

[0086] 2) Molten salt heating and heat storage module

[0087] In this embodiment, ternary mixed nitrate (53% KNO3-40% NaNO2-7% NaNO3) is selected as molten salt, i.e., heat storage medium. Combining the project experience of existing molten salt heat storage projects such as solar thermal power generation and the parameter requirements of adiabatic compressed air energy storage systems, the temperature of the molten salt low temperature tank of the molten salt heating heat storage module is set to 185°C (corresponding to the high-pressure air inlet temperature of 170°C), and the temperature of the molten salt high temperature tank is set to 375°C (corresponding to the high-pressure air outlet temperature of 350°C).

[0088] Molten salt heating process: The molten salt (185°C) in the low-temperature molten salt tank is pumped into the molten salt heating furnace through a molten salt pump, and hydrogen-rich gas is introduced for combustion and heating, so that the molten salt temperature rises to 375°C and enters the high-temperature molten salt storage. During the energy release process of the compressed air energy storage system, the high-pressure air before expansion is heat exchanged; the compressed air system works intermittently (charging for 8 hours and discharging for 8 hours), while the molten salt heating system is designed to work continuously for 24 hours; the composition of the hydrogen-rich gas is shown in Table 5:

[0089] Table 5 Reference table for calculation of hydrogen-rich fuel gas components

[0090] Components <![CDATA[H2]]> CO <![CDATA[CH4]]> C2 %mol 84％ 0.05％ 16％ 0.00％

[0091] The molten salt heating heat storage module mainly includes a high-temperature molten salt tank, a low-temperature molten salt tank, a molten salt heating furnace, 2-stage molten salt heat exchange units, molten salt pipelines and molten salt pumps. The design temperature of the low-temperature molten salt tank is ≤200℃, and the design temperature of the high-temperature molten salt tank is ≤400℃. The molten salt pipeline, valve and molten salt pump group (6 groups) are connected to the molten salt heat exchanger and molten salt heating furnace. The parameters of the molten salt heating heat storage module are shown in Table 6:

[0092] Table 6 Molten salt heating thermal storage module parameters

[0093]

[0094] 1 The calculation formula for the effective total heat of combustible industrial tail gas combustion is as follows:

[0095] M4=Q4×h4=V4×q4×h4(5)

[0096] In formula (5), M4 represents the total effective heat of the combustible industrial tail gas combustion, kWh; Q4 represents the combustion power of the molten salt heating furnace, kW; h4 represents the working time of the molten salt heating furnace, h; V4 represents the volume flow rate of the combustible industrial tail gas, Nm 3 / h; q4 represents the calorific value of combustible industrial tail gas, kJ / Nm 3 .

[0097] According to calculation, the total effective heat of combustible industrial exhaust gas combustion is M4=Q4×h4=V4×q4×h4=2654×14.86×24=946560MJ=262933kWh.

[0098] 2 The total heat required for the second expansion process is calculated as follows:

[0099] M5=Q5×h5(6)

[0100] In formula (6), M5 represents the total heat required for the second expansion process, kWh; Q5 represents the power required for the second expansion process, kW; and h5 represents the second expansion time, h.

[0101] After calculation, the total heat required for the second expansion process is M5=Q5×h5=(11832+11832)×8=189312kWh.

[0102] Calculated according to the overall efficiency conversion coefficient η (0.72-0.75) of the molten salt heating heat storage and exchange system, its heat energy can fully meet the total heat required for the second stage of expansion energy release.

[0103] (4) Calculation of electricity-to-electricity conversion efficiency

[0104] 1 The total power consumption during compression is calculated as follows:

[0105]

[0106] In formula (7), W 压 Represents the total power consumption of compression, kWh; W i represents the power of each compressor unit, kW; h2 represents the compression time, h.

[0107] After calculation, the total power consumption of compression

[0108] 2 The calculation formula for the total amount of electricity released by expansion is as follows:

[0109] W2=K2×N2×h2(8)

[0110] In formula (8), W2 represents the total expansion power generation, kWh; K2 represents the expansion power loss coefficient; N2 represents the total expansion power, kW; h2 represents the expansion time, h.

[0111] According to calculation, the total power generation during the expansion energy release process is W2=K2×N2×h2=0.96×30449×8=233848kWh.

[0112] 3 The calculation formula of electricity-to-electricity conversion efficiency is as follows:

[0113] η1=W2÷W 压 (9)

[0114] In formula (9), η1 represents the electricity-to-electricity conversion efficiency; W2 represents the total expanded power generation, kWh; W压 Represents the total power consumption of compression, kWh.

[0115] After calculation, the electricity-to-electricity conversion efficiency in this system is η1=W2÷W 压 =233848÷303424=77%.

[0116] According to calculations, the electric-to-electric conversion efficiency of this scheme after the coupling of combustible industrial tail gas and adiabatic compressed air energy storage technology reaches 77%, which is much higher than the electric-to-electric conversion efficiency (about 60%) of the existing conventional adiabatic non-supplementary compressed air energy storage technology of the same specifications. After considering the heat storage and exchange losses of molten salt heating, the system can be fully guaranteed to operate reliably and efficiently. The total amount of electricity released by expansion after heat supplementation increases, and the electric-to-electric conversion efficiency is significantly improved, which effectively improves the energy utilization rate.

[0117] The working principle of the present invention is:

[0118] In the present invention, the multi-stage compressor unit in the adiabatic compression energy storage module uses low-temperature electricity to achieve multi-stage air compression, and transmits the generated high calorific value compression heat to the adiabatic compression heat recovery module through the multi-stage heat exchange unit, and the high-pressure air after multi-stage compression is stored in the air storage container; the adiabatic compression heat recovery module stores the compression heat through medium-temperature water, and provides the first heating for the compressed air before entering each stage of the expansion unit through the medium-temperature water heat exchange unit; the molten salt heating heat storage module burns the combustible industrial exhaust gas in the molten salt heating furnace and stores the combustion heat, and provides the second heating for the compressed air before entering each stage of the expansion unit through the molten salt heat exchange unit; the multi-stage expansion unit in the expansion power generation module uses the high-pressure compressed air after twice heating to expand and generate power, thereby realizing energy conversion.

Claims

1. A combustible industrial tail gas coupled adiabatic compressed air energy storage system, comprising an adiabatic compression energy storage module, an adiabatic compression heat recovery module, a molten salt heating heat storage module, and a high-temperature expansion power generation module, characterized in that: The adiabatic compression energy storage module utilizes low-period electric energy to achieve multi-stage air compression and converts the electric energy into internal energy and stores it in compressed gas. The adiabatic compression heat recovery module is used to recover and store the compression heat generated during the multi-stage compression of air in the adiabatic compression energy storage module. The molten salt heating heat storage module burns the combustible industrial tail gas in a molten salt heating furnace and stores the combustion heat, and transfers the combustion heat to the high-temperature expansion power generation module when needed. The high-temperature expansion power generation module receives the combustion heat provided by the molten salt heating heat storage module and the compression heat provided by the adiabatic compression heat recovery module to complete the compressed gas expansion power generation.

2. The adiabatic compressed air energy storage system according to claim 1, characterized in that: The adiabatic compression energy storage module comprises an nth (n=1, 2, ..., n)th compressor unit, a qth (q=1, 2, ..., n-1)th heat exchange unit, a cooling unit, an air storage unit and an intake pipe, each compressor unit comprises a compressor unit and a motor, each compressor unit comprises an sth (s=1, 2, ..., s)th compressor, each compressor of each compressor unit is axially connected in series, and the motor is connected to the compressor to realize the air boosting function; the outside air passes through the first compressor unit, the first heat exchange unit, the second compressor unit, the second heat exchange unit, ..., the n-1 heat exchange unit, the nth compressor unit, and the cooling unit in sequence through the intake pipe, and finally enters the air storage unit to realize air compression and storage; the qth (q=1, 2, ..., n-1)th heat exchange unit comprises a heat exchanger to realize the recovery and utilization of the compression heat generated by each compressor unit; the cooling unit comprises a cooler to realize the cooling and regulation of the compression heat generated by the nth compressor unit; the air storage unit comprises an air storage container.

3. The adiabatic compressed air energy storage system according to claim 1, characterized in that: The adiabatic compression heat recovery module comprises a medium-temperature water cooling tank, a medium-temperature water hot tank, an mth (m=1, 2, ..., m)th medium-temperature water heat exchange unit and a medium-temperature water pipe. The medium-temperature water cooling tank is connected to the qth (q=1, 2, ..., n-1)th heat exchange unit, the medium-temperature water hot tank and the mth (m=1, 2, ..., m)th medium-temperature water heat exchange unit in sequence through the medium-temperature water pipe to form a closed loop. The qth (q=1, 2, ..., n-1)th heat exchange unit in the adiabatic compression energy storage module is connected in parallel with the medium-temperature water cooling tank and the medium-temperature water hot tank through the medium-temperature water pipe. The condensed water in the medium-temperature water cooling tank exchanges heat with the qth (q=1, 2, ..., n-1)th heat exchange unit under the action of pump pressure through the medium-temperature water pipe and then enters the medium-temperature water hot tank for heat storage; each section of the medium-temperature water heat exchange units is connected in parallel.

4. The adiabatic compressed air energy storage system according to claim 1, characterized in that: The molten salt heating and heat storage module comprises a molten salt heating furnace, a high-temperature molten salt tank, an mth (m=1, 2, ..., m)th molten salt heat exchange unit, a low-temperature molten salt tank and a molten salt pipeline, wherein the molten salt pipeline sequentially connects the molten salt heating furnace, the high-temperature molten salt tank, the mth (m=1, 2, ..., m)th molten salt heat exchange unit and the low-temperature molten salt tank to form a closed loop, and each section of the molten salt heat exchange units is connected in parallel; the combustible industrial tail gas enters the molten salt heating furnace to burn and heat the molten salt from the low-temperature molten salt tank, and the molten salt enters the high-temperature molten salt tank after the temperature is increased to realize heat storage, and the molten salt in the high-temperature molten salt tank enters the low-temperature molten salt tank after heat exchange with the high-temperature expansion power generation module through the mth (m=1, 2, ..., m)th molten salt heat exchange unit.

5. The adiabatic compressed air energy storage system according to claim 1, characterized in that: The high-temperature expansion power generation module comprises an mth (m=1, 2, ..., m)th expansion machine unit, a generator and an outlet pipe, each expansion machine unit comprises an expansion machine group, and the expansion machine group is connected to the generator; the outlet pipe is connected to the gas storage unit, the first section medium-temperature water heat exchange unit, the first section molten salt heat exchange unit, the first section expansion machine unit, ..., the mth section medium-temperature water heat exchange unit, the mth section molten salt heat exchange unit, and the mth section expansion machine unit in sequence; the compressed air can be heated and expanded to perform work in one of the following two ways: (1) the compressed air in the gas storage unit passes through the mth (m=1, 2, ..., m)th section medium-temperature water heat exchange unit and the mth (m=1, 2, ..., m)th section molten salt heat exchange unit in sequence through the outlet pipe, and then enters the mth (m=1, 2, ..., m)th section expansion machine unit for heating, thereby driving the generator to generate electricity, and the compressed air discharged from each expansion machine unit enters the next section medium-temperature water heat exchange unit again, and circulates in sequence, and the compressed air is finally discharged from the outlet of the mth section expansion machine unit; (2) The compressed air in the gas storage unit passes through the outlet pipe in turn through the first section medium-temperature water heat exchange unit and the first section molten salt heat exchange unit for heating, and then enters the first section expander unit to perform work, thereby driving the generator to generate electricity. The compressed air discharged from the first section expander unit after performing work is heated by the mth (m=2, ..., m)th section molten salt heat exchange unit, and then enters the mth (m=2, ..., m)th section expander unit to perform work. The compressed air discharged from each section expander unit enters the next section molten salt heat exchange unit again, and the cycle is repeated in sequence. The compressed air is finally discharged from the outlet of the mth section expander unit.

6. The adiabatic compressed air energy storage system according to claim 2, characterized in that: The number of stages n of the nth (n=1, 2, ..., n) compressor unit is 3-8, the outlet air temperature of the nth (n=1, 2, ..., n) compressor unit is 150-250°C, and the inlet air temperature of the nth (n=2, 3, ..., n) compressor unit or air storage unit is 30-50°C.

7. The adiabatic compressed air energy storage system according to claim 3, characterized in that: The water storage temperature of the medium-temperature water cooling tank is 20-30°C, and the water storage temperature of the medium-temperature water heating tank is 135-235°C.

8. The adiabatic compressed air energy storage system according to claim 4, characterized in that: The working temperature of the molten salt used in the molten salt heating furnace is not higher than 565° C. The industrial combustible tail gas used in the molten salt heating heat storage module is hydrogen-rich gas, and the volume content of hydrogen in the hydrogen-rich gas is greater than 40%.

9. The adiabatic compressed air energy storage system according to claim 5, characterized in that: The number of expansion unit sections m of the mth (m=1, 2, ..., m) stage is 2-5.

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