Energy storage steam system suitable for intermittent waste heat utilization

Abstract

The energy storage steam system comprises a main flue, a fused salt heat exchange module and a water heat exchange module are arranged in the main flue, the fused salt heat exchange module comprises a salt heat exchanger, the salt heat exchanger is arranged in the main flue, and the water heat exchange module is arranged in the main flue. The inlet end and the outlet section of the salt heat exchanger communicate with a cold salt tank and a hot salt tank through conveying pipelines correspondingly, the water heat exchange module comprises a water quality heat exchanger, the water quality heat exchanger is arranged in a main flue, and the inlet end and the outlet section of the water quality heat exchanger are arranged in a condensation water tank and a deaerator through conveying pipelines correspondingly; the output end of the deaerator communicates with the fused salt-steam generating device, and the cold salt tank and the hot salt tank communicate with the fused salt-steam generating device. Fused salt is used as a high-temperature heat transfer and storage medium, water is used as a heat transfer and storage medium of a low-temperature area, intermittent flue gas or process gas waste heat is recycled, then the recycled heat is used for generating high-parameter steam, and the requirements for external driving, heat supply, power generation or heat supply and the like are met.

Description

Technical Field

[0001] The present invention relates to an energy storage steam system suitable for intermittent waste heat utilization, and its main application scenario is in the field of industrial energy conservation. It is particularly suitable for waste heat utilization of discontinuous (or periodic) flue gas or process gas such as metal smelting and silicon material purification. The steam generated by this system can be used for driving, power generation, heating or heating, etc. Background Art

[0002] According to relevant statistical data in 2020, China's crude steel output accounts for more than 50% of the global total output. The steel industry consumes 550 million tons of standard coal annually, accounting for about 11% of the total national energy consumption, and the carbon emissions contribute more than 60% of the total global steel carbon emissions. Therefore, low carbon and energy conservation have become the main theme of the development of the steel industry in China in the coming period.

[0003] During converter steelmaking, a large amount of heat is generated due to the reaction of oxygen and reducing agent. On the one hand, this heat maintains the normal progress of the reaction, and on the other hand, a large amount of waste heat is discharged with the converter flue gas.

[0004] During electric arc furnace steelmaking, since a large amount of heat is required for the melting of scrap steel, usually a large amount of electric energy input is required to meet the process requirements, and a large amount of waste heat is also discharged with the converter flue gas.

[0005] Therefore, waste heat recovery is an important way to improve the energy utilization efficiency of the converter process. There are many scenarios for intermittent flue gas or process gas in other process flows, which will not be enumerated here.

[0006] The most common way to utilize intermittent waste heat at present is to use a water-cooled wall structure for waste heat recovery, and saturated steam with certain parameters is generated by this waste heat recovery device for power generation, heating or heating. This method has the advantages of simple system and low investment cost, but there are also the following two problems: First, the heat discharge process of the above process flow is intermittent. Due to the weak heat storage capacity of the waste heat recovery system with water as the working medium, it is difficult to fundamentally adapt to the characteristics of periodic fluctuations. The steam parameters generated by the system are usually unstable, which brings challenges to the subsequent power generation or heat use process.

[0007] Second, for the above waste heat recovery process with water as the working medium, the generated saturated steam parameters are usually low. When used for power generation, the low steam parameters limit the exergy utilization efficiency of the system and set a limit condition for the energy efficiency improvement of the waste heat process. Summary of the Invention

[0008] To solve the above technical problems, the present invention designs an energy storage steam system suitable for intermittent waste heat utilization. The system uses molten salt as the heat transfer and heat storage medium at high temperature, and water as the heat transfer and heat storage medium in the low-temperature area, recovers the intermittent flue gas or process gas waste heat, and then uses the recovered heat to generate high-parameter steam to meet the needs of external drive, heating, power generation or heating, etc.

[0009] The present invention adopts the following technical solutions: An energy storage steam system suitable for intermittent waste heat utilization, including an inlet flue, a main flue and an exhaust flue. A molten salt heat exchange module and a water heat exchange module are arranged in the main flue. The molten salt heat exchange module includes a salt heat exchanger, which is arranged in the main flue. The inlet end and the outlet section of the salt heat exchanger are respectively connected to a cold salt tank and a hot salt tank through a conveying pipeline. The water heat exchange module includes a water heat exchanger, which is arranged in the main flue. The inlet end and the outlet section of the water heat exchanger are respectively connected to a condensate tank and a deaerator through a conveying pipeline. The output end of the deaerator is connected to a molten salt-steam generating device, and the cold salt tank and the hot salt tank are connected to the molten salt-steam generating device.

[0010] Preferably, the main flue is vertically arranged, and the molten salt heat exchange module and the water heat exchange module are arranged from low to high in the height direction. This is convenient for the system to drain the internal molten salt medium when it is shut down, eliminate the risks of frozen salt and pipe blockage of the molten salt, and improve the safety and service life of the system.

[0011] Preferably, a cold salt pump is installed on the conveying pipeline between the cold salt tank and the salt heat exchanger.

[0012] Preferably, a hot salt pump is installed on the conveying pipeline between the hot salt tank and the molten salt-steam generating device.

[0013] Preferably, a condensate pump is installed on the conveying pipeline between the condensate tank and the water heat exchanger.

[0014] Preferably, a feed water pump is installed on the conveying pipeline between the deaerator and the molten salt-steam generating device.

[0015] The beneficial effects of the present invention are as follows: (1) It can be applied to the waste heat recovery process of discontinuous (or periodic) flue gas or process gas; (2) Molten salt and water are used as heat transfer and heat storage media, and energy is stored in a stepped manner according to the quality level, improving the energy utilization efficiency of the entire system; (3) During the heat storage process, the flow rates of molten salt and water are flexibly adjusted according to the waste heat parameters (flow rate, temperature, etc.) to match the periodic emission characteristics of flue gas or process gas; (4) The preferred layout mode of this system is vertical layout, which is convenient for desalting and gas release of molten salt equipment and the system, improving the safety and service life of the system; (5) Through the heat storage and heat release processes of molten salt and water dual media, the energy recovery and waste heat utilization are decoupled, and the output thermal parameters of the system can be kept stable or adjusted flexibly according to requirements; (6) The high-temperature molten salt generated by heat improves the output steam parameters of the system. When used for power generation, it can improve the power generation efficiency of the system, and when used for heat supply, it can adapt to more heat-using scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic structural diagram of the present invention; In the figure: 1, inlet flue; 2, main flue; 3, discharge flue; 4, cold salt tank; 5, cold salt pump; 6, salt heat exchanger; 7, hot salt tank; 8, condensate tank; 9, condensate pump; 10, water heat exchanger; 11, deaerator; 12, feed water pump; 13, hot salt pump; 14, molten salt-steam generating device. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0017] The technical solution of the present invention will be further specifically described below through specific embodiments and in conjunction with the drawings: Embodiment: As Figure 1 shown, an energy storage steam system applicable to intermittent waste heat utilization includes an inlet flue 1, a main flue 2, a discharge flue 3, a cold salt tank 4, a cold salt pump 5, a salt heat exchanger 6, a hot salt tank 7, a condensate tank 8, a condensate pump 9, a water heat exchanger 10, a deaerator 11, a feed water pump 12, a hot salt pump 13, and a molten salt-steam generating device 14.

[0018] A molten salt heat exchange module and a water heat exchange module are arranged in the main flue. The molten salt heat exchange module includes a salt heat exchanger, which is arranged in the main flue. The inlet end and the outlet section of the salt heat exchanger are respectively connected to the cold salt tank and the hot salt tank through conveying pipelines. The water heat exchange module includes a water heat exchanger, which is arranged in the main flue. The inlet end and the outlet section of the water heat exchanger are respectively connected to the condensate tank and the deaerator through conveying pipelines. The output end of the deaerator is connected to the molten salt-steam generating device, and the cold salt tank and the hot salt tank are connected to the molten salt-steam generating device.

[0019] Condensate is usually generated after the externally supplied steam of this system is used for power generation or heat utilization. If the condensate cannot be recovered or only partially recovered, the system requires a make-up water device with a corresponding capacity. High-temperature flue gas or process gas passes through the inlet flue, main flue, and discharge flue in sequence; and transfers heat to molten salt and water in the main flue, and the cooled flue gas or process gas flows out of the system through the discharge flue.

[0020] The main flue is arranged vertically, and the molten salt heat exchange module and the water heat exchange module are arranged from low to high along the height direction. This facilitates the system to drain the internal molten salt medium when it is shut down, eliminates the risks of frozen salt and blocked pipes of the molten salt, and improves the safety and service life of the system.

[0021] When the present invention is in use, the heat storage process: High-temperature flue gas or process gas enters the system through the inlet flue 1, transfers heat to the molten salt and water medium in the main flue 2, and then leaves the system through the discharge flue 3.

[0022] The cold salt pump 5 pumps the relatively low-temperature molten salt out of the cold salt tank 4, enters the salt heat exchanger 6, absorbs the heat of the high-temperature section of the flue gas or process gas, becomes high-temperature molten salt and returns to the hot salt tank 7, storing the heat of the high-temperature section in the molten salt; The condensate pump 9 pumps the relatively low-temperature water from the condensate tank 8, enters the water heat exchanger 10, absorbs the heat of the low-temperature section of the flue gas or process gas, the water temperature rises and then enters the deaerator 11, storing the heat of the low-temperature section in the hot water; According to the flow rate and temperature parameters of the flue gas or process gas, adjust the medium flow rates in the salt heat exchanger 6 and the water heat exchanger 10, so that the temperatures of the corresponding media at the outlets of the salt heat exchanger 6 and the water heat exchanger 10 are basically kept stable.

[0023] The heat release process: The hot salt pump 13 pumps the high-temperature molten salt from the hot salt tank 7, enters the molten salt-steam generating device 14, transfers heat to the water working medium, and the molten salt temperature drops and then returns to the cold salt tank 4; The water working medium comes from the deaerator 11, is driven by the feed water pump 12 and then enters the molten salt-steam generating device 14, absorbs the heat released by the molten salt therein to complete the processes of temperature rise, evaporation and superheat, and becomes steam with required parameters and is sent out of the system.

[0024] The energy storage steam system applicable to intermittent waste heat utilization realizes cascaded storage and utilization of energy by using the different characteristics of molten salt and water. At the same time, it decouples the heat storage and heat utilization processes, converting unstable waste heat input into stable and adjustable steam output. The vertical layout structure design can achieve full drainage of the system during shutdown, eliminating the risks of frozen salt and blocked pipes in molten salt equipment and systems. Compared with the existing water working medium solutions, this solution improves the parameters and quality of the heat storage system. During the heat release process, it improves the output steam parameters of the system, so it has higher power generation efficiency and stronger heat supply adaptability, and is an upgraded technology for intermittent waste heat utilization. Under the background of "dual carbon" in China, this system is an important way to improve energy utilization efficiency and reduce carbon emission intensity.

[0025] The embodiments described above are only a preferred solution of the present invention, and do not impose any form of limitation on the present invention. There are other variations and modifications without exceeding the technical solutions recorded in the claims.

Claims

1. An energy storage steam system suitable for intermittent waste heat utilization, comprising an inlet flue, a main flue and an exhaust flue, characterized in that: A molten salt heat exchange module and a water heat exchange module are arranged in the main flue. The molten salt heat exchange module includes a salt heat exchanger, which is arranged in the main flue. The inlet end and the outlet section of the salt heat exchanger are connected to the cold salt tank and the hot salt tank through the conveying pipeline respectively. The water heat exchange module includes a water heat exchanger, which is arranged in the main flue. The inlet end and the outlet section of the water heat exchanger are connected to the condensation water tank and the deaerator through the conveying pipeline respectively. The output end of the deaerator is connected to the molten salt-steam generating device, and the cold salt tank and the hot salt tank are connected to the molten salt-steam generating device.

2. The energy storage steam system suitable for intermittent waste heat utilization according to claim 1 is characterized in that: The main flue is arranged vertically, and the molten salt heat exchange module and the water heat exchange module are arranged from low to high along the height direction.

3. The energy storage steam system suitable for intermittent waste heat utilization according to claim 1 is characterized in that: A cold salt pump is installed on the delivery pipeline between the cold salt tank and the salt heat exchanger.

4. The energy storage steam system suitable for intermittent waste heat utilization according to claim 1 is characterized in that: A hot salt pump is installed on the delivery pipeline between the hot salt tank and the molten salt-steam generating device.

5. The energy storage steam system suitable for intermittent waste heat utilization according to claim 1 is characterized in that: A condensate pump is installed on the delivery pipeline between the condensate tank and the water heat exchanger.

6. The energy storage steam system suitable for intermittent waste heat utilization according to claim 1 is characterized in that: A water feed pump is installed on the delivery pipeline between the deaerator and the molten salt-steam generating device.

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