Dead steam waste heat recovery device system and method based on steam generator

Abstract

The invention relates to an exhaust steam waste heat recovery device system and method based on a steam generator, and the system comprises an exhaust steam waste heat recovery subsystem which comprises a refrigerant direct-expansion efficient heat exchanger; the high-temperature steam heat pump subsystem comprises a steam generator; a replenished water outlet of the replenished water preheating subsystem is connected with a replenished water inlet of the steam generator, and the replenished water preheating subsystem is used for preheating replenished water; and the fused salt subsystem comprises a fused salt storage tank, an outlet of the fused salt storage tank is connected with a heat source inlet of the steam generator and the water supplementing and preheating subsystem, and the fused salt subsystem is used for heating fused salt for energy storage in the electricity consumption trough and providing heat for preheating supplemented water and / or providing heat for the steam generator. The waste steam heat can be recycled to produce steam, the energy utilization efficiency is improved, fossil fuel combustion is reduced, and pollutant emission is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of exhaust steam waste heat recovery, and in particular to an exhaust steam waste heat recovery device system and method based on a steam generator. Background Art

[0002] According to statistics, only 40% of the heat generated by fossil energy in the industrial sector is effectively utilized, while 60% is ultimately converted into waste heat. Waste heat is categorized by grade as high, medium, and low. Medium and high-grade waste heat is recycled through waste heat power generation and steam generation in waste heat boilers. Low-grade waste heat has a low temperature, low energy density, and is relatively dispersed. This is especially true for low-grade exhaust steam from thermal power plants, which is more difficult to utilize. Most of this heat is discharged through cooling towers or air-cooled islands. Furthermore, chemical production processes produce numerous byproducts with complex compositions, and the resulting waste steam often contains many impurities, making it difficult to reuse. Therefore, most industrial waste steam is currently discharged directly. In the power, chemical, building materials, metallurgy, papermaking, petrochemical and other industries, there are a large number of exhaust steam and waste heat resources. For example: in the power generation process, the exhaust steam discharged by the steam turbine has a high temperature and pressure; the chemical reaction waste heat generated in petroleum and chemical production; the cement production and metal smelting processes generate a large amount of high-temperature flue gas and steam; in the drying field, after the hot air dries the moisture of the material, the exhaust air carries a large amount of heat energy.

[0003] At the same time, according to statistics from the International Energy Agency, heat demand on the energy demand side accounts for 50%. The heat demand in the industrial field is mostly concentrated in the range of 80 to 170°C, and steam is usually used as the heat carrier. The existing steam sources are mainly direct supply from thermal power plants and self-contained coal-fired and steam-fired boilers.

[0004] It can be seen that there is a contradiction between the serious waste of waste heat and the strong demand for steam in the industrial field. If the exhaust steam is recovered to produce industrial steam and the energy conversion process is optimized, it will greatly improve energy utilization and reduce carbon emissions. However, the exhaust steam in the industrial field is large in volume and contains a lot of heat. The recovery of low-grade waste heat is difficult, and the direct discharge of waste heat causes energy waste and environmental thermal pollution. At the same time, there is a strong demand for steam in the industrial production process. The use of coal-fired / gas-fired boilers to produce steam will consume a large amount of fossil energy, which is not in line with carbon reduction policies. The direct supply of steam from thermal power plants has the disadvantages of a small heating radius, large heat loss and high initial investment.

[0005] Therefore, providing a steam generator-based exhaust steam heat recovery device system and method to recover the exhaust steam heat lost in the industrial process to generate steam is a technical problem that needs to be solved in the current field. Summary of the Invention

[0006] In response to the shortcomings of the existing technology, the purpose of the present invention is to provide a waste steam heat recovery device system and method based on a steam generator. Compared with the existing technology, the present invention can recycle the waste steam heat lost in the industrial process to produce industrial steam as a substitute or supplement for the existing industrial steam, thereby improving energy utilization efficiency, reducing fossil fuel combustion, and reducing pollutant emissions.

[0007] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a steam generator exhaust heat recovery device system, the exhaust heat recovery device system comprising:

[0009] The exhaust steam heat recovery subsystem includes a refrigerant direct expansion high-efficiency heat exchanger. The exhaust steam heat recovery subsystem uses low-temperature, low-pressure refrigerant to directly absorb the waste heat of the hot and wet exhaust steam. The refrigerant evaporates from liquid to gas, and the hot and wet exhaust steam condenses from gas to liquid, achieving heat transfer through dual phase change on both sides.

[0010] A high-temperature steam heat pump subsystem, comprising a steam generator, configured to convert water into steam using the heat of exhaust steam;

[0011] A water supply preheating subsystem, wherein the water supply outlet of the water supply preheating subsystem is connected to the water supply inlet of the steam generator, and the water supply preheating subsystem is used to preheat the water supply;

[0012] The molten salt subsystem includes a molten salt storage tank, the outlet of which is respectively connected to the heat source inlet of the steam generator and the water preheating subsystem. The molten salt subsystem is used to heat the molten salt energy storage during low electricity consumption, and to provide heat for preheating water and / or heat for the steam generator.

[0013] In the device system provided by the present invention, the exhaust steam heat lost during the process is recovered to produce industrial steam as a supplement or substitute for existing industrial steam. Compared with steam prepared with fossil fuels, this part is zero-carbon energy, no fossil fuel is burned, and no pollutants are emitted.

[0014] Preferably, the refrigerant direct expansion high-efficiency heat exchanger in the exhaust steam waste heat recovery subsystem includes a primary evaporator and a secondary evaporator.

[0015] Preferably, the high-temperature steam heat pump subsystem further includes a refrigerant compressor and a return air throttle valve.

[0016] Preferably, the heat source inlet of the first-stage evaporator is connected to the exhaust steam, the heat source outlet of the first-stage evaporator is connected to the heat source inlet of the second-stage evaporator, the refrigerant outlet of the first-stage evaporator is connected to the refrigerant compressor via a return air throttle valve, the refrigerant outlet of the second-stage evaporator is connected to the refrigerant compressor, the outlet of the refrigerant compressor is connected to the heat source inlet of the steam generator via a first control valve, and the heat source outlet of the steam generator is connected to the refrigerant inlets of the first-stage evaporator and the second-stage evaporator, respectively.

[0017] In the present invention, the heat source inlet of the first-stage evaporator is connected to the exhaust steam, and the heat source outlet of the first-stage evaporator is connected to the heat source inlet of the second-stage evaporator, which means that the exhaust steam first enters the heat source side of the first-stage evaporator to release heat, and the exhaust steam after releasing heat in the first-stage evaporator enters the heat source side of the second-stage evaporator to further release heat, thereby realizing the cascade utilization of heat.

[0018] Preferably, the high-temperature steam heat pump subsystem further includes an expansion valve and an economizer.

[0019] Preferably, the heat source outlet of the steam generator is connected to the heat source inlet of the economizer through the second control valve, and the heat source outlet of the steam generator is also connected to the cold source inlet of the economizer through the second control valve and the first expansion valve in sequence, the heat source outlet of the economizer is connected to the refrigerant inlet of the secondary evaporator through the second expansion valve, and the heat source outlet of the economizer is also connected to the refrigerant inlet of the primary evaporator through the third expansion valve, and the cold source outlet of the economizer is connected to the refrigerant compressor.

[0020] Preferably, the high-temperature steam heat pump subsystem further includes a first steam outlet and a second steam outlet, the steam outlet of the steam generator is connected to the first steam outlet via a third control valve, and the steam outlet of the steam generator is connected to the second steam outlet via a fourth control valve and a water vapor compressor in turn.

[0021] Preferably, the molten salt subsystem includes a molten salt storage tank, an electric heater and a molten salt circulation pump.

[0022] Preferably, the molten salt storage tank is connected to the heat source inlet of the steam generator through a molten salt circulation pump, a fifth control valve is arranged between the molten salt circulation pump and the heat source inlet of the steam generator, the heat source outlet of the steam generator is connected to the molten salt storage tank through a sixth control valve, and an electric heater is arranged in the molten salt storage tank.

[0023] Preferably, the water replenishment preheating subsystem includes an exhaust steam preheater, a molten salt preheater and a water replenishment port.

[0024] Preferably, the heat source inlet of the exhaust steam preheater is connected to the heat source outlet of the secondary evaporator, the water supply port is connected to the cold source inlet of the exhaust steam preheater through the seventh control valve, and the cold source outlet of the exhaust steam preheater is connected to the water supply inlet of the steam generator.

[0025] In the present invention, the heat source inlet of the exhaust steam preheater is connected to the heat source outlet of the secondary evaporator, which means that the exhaust steam after releasing heat in the secondary evaporator enters the exhaust steam preheater to continue to release heat to preheat and replenish water, thereby further improving the utilization rate of heat.

[0026] Preferably, the water supply port is also connected to the cold source inlet of the molten salt preheater through an eighth control valve, the molten salt storage tank is connected to the heat source inlet of the molten salt preheater through a molten salt circulation pump, the heat source outlet of the molten salt preheater is connected to the molten salt storage tank via a ninth control valve, and the cold source outlet of the molten salt preheater is connected to the water supply inlet of the steam generator.

[0027] Preferably, the exhaust steam waste heat recovery device system also includes a control subsystem.

[0028] Preferably, the control subsystem includes a temperature sensor and a pressure sensor.

[0029] Preferably, a first temperature sensor is provided at the heat source inlet of the first-stage evaporator for monitoring the temperature of the exhaust steam entering the first-stage evaporator.

[0030] Preferably, a second temperature sensor is provided at the water replenishment inlet of the steam generator.

[0031] Preferably, a third temperature sensor is provided in the molten salt storage tank.

[0032] Preferably, a first pressure sensor is provided at the steam outlet of the steam generator.

[0033] Preferably, a second pressure sensor is provided at the outlet of the water vapor compressor.

[0034] In a second aspect, the present invention provides a method for recovering waste heat from exhaust steam of a steam generator, the method using the device system for recovering waste heat from exhaust steam of a steam generator described in the first aspect of the present invention, the method comprising the following steps:

[0035] Control the exhaust steam waste heat recovery subsystem, using low-temperature and low-pressure refrigerant to directly absorb the waste heat of hot and wet exhaust steam. The refrigerant evaporates from liquid to gas, and the hot and wet exhaust steam condenses from gas to liquid, achieving heat transfer through dual phase change on both sides.

[0036] Control the high-temperature steam heat pump subsystem to absorb heat from the exhaust steam and transfer the heat to the steam generator, which converts water into steam;

[0037] Controlling the feed water preheating subsystem to absorb heat from exhaust steam and / or molten salt to preheat feed water, and then feeding the preheated feed water into the steam generator as feed water for steam production;

[0038] The molten salt subsystem is controlled to provide heat to the steam generator so that the steam generator converts water into steam and / or to provide heat to the feed water preheating subsystem so as to preheat the feed water.

[0039] The method provided by the present invention utilizes the aforementioned device system, combining an exhaust steam heat recovery subsystem, a high-temperature steam heat pump subsystem, and a molten salt subsystem. When the exhaust steam is stable and meets the required temperature, the exhaust steam heat recovery and high-temperature steam heat pump subsystems are activated to produce industrial steam. When the exhaust steam is unstable or the temperature does not meet the requirements for the high-temperature steam heat pump subsystem, the exhaust steam heat recovery and high-temperature steam heat pump subsystems are shut down, and the molten salt subsystem is activated to release heat to the steam generator. This coupling of subsystems ensures a stable and continuous steam supply.

[0040] Preferably, the method comprises the following steps:

[0041] When the exhaust steam temperature meets the requirements, open the first and second control valves, close the fifth and sixth control valves, and the exhaust steam heat recovery subsystem and high-temperature steam heat pump subsystem start operation:

[0042] The exhaust steam flows through the heat source side of the primary evaporator and the secondary evaporator in sequence, releasing heat to the refrigerant to generate refrigerant steam. The refrigerant steam generated by the primary evaporator passes through the return air throttle valve and mixes with the refrigerant steam generated by the secondary evaporator. The mixed refrigerant steam is compressed by the refrigerant compressor and then enters the steam generator to release heat and heat the water into low-pressure steam. The condensed refrigerant is divided into two streams, one of which flows into the heat source side of the economizer to release heat, and the other flows into the cold source side of the economizer after being reduced in pressure by the first expansion valve to absorb heat to obtain saturated or supersaturated refrigerant steam. It then enters the refrigerant compressor for compression and continues to be sent to the steam generator to provide heat. The refrigerant that has released heat in the economizer passes through the third expansion valve and the second expansion valve respectively and returns to the cold source side of the primary evaporator and the secondary evaporator and continues to absorb the heat of the exhaust steam. The low-pressure steam generated by the steam generator is divided into two streams, one of which is discharged through the first steam outlet, and the other is discharged through the second steam outlet after the water vapor compressor increases its pressure.

[0043] When the exhaust steam is unstable or the temperature does not meet the requirements, the first control valve and the second control valve are closed, the fifth control valve and the sixth control valve are opened, and the molten salt heat release subsystem operates: the molten salt circulation pump transports the molten salt in the molten salt storage tank to the steam generator to release heat and heat the water into low-pressure steam. The molten salt after releasing heat returns to the molten salt storage tank.

[0044] Preferably, the method includes the following steps: a second temperature sensor located at the feed water inlet of the steam generator monitors the feed water temperature in real time; when the exhaust steam temperature meets the preheating feed water requirement, the seventh control valve is opened and the eighth control valve is closed, and the feed water entering from the feed water inlet enters the steam generator after heat exchange in the exhaust steam preheater; when the exhaust steam temperature cannot meet the preheating feed water requirement, the seventh control valve and the eighth control valve are opened and the opening degree is adjusted to adjust the distribution of the feed water between the exhaust steam preheater and the molten salt preheater; one stream of the feed water entering from the feed water inlet enters the steam generator after heat exchange in the exhaust steam preheater, and the other stream enters the steam generator after heat exchange in the molten salt preheater; the molten salt circulation pump transports the molten salt in the molten salt storage tank to the molten salt preheater to provide heat, and then returns to the molten salt storage tank through the ninth control valve.

[0045] Preferably, the method comprises the following steps: a third temperature sensor in the molten salt storage tank monitors the temperature of the molten salt, and when the temperature does not meet the requirement, the electric heater utilizes valley electricity to heat the molten salt.

[0046] Preferably, the method includes the following steps: a first pressure sensor located at the steam outlet of the steam generator monitors the steam pressure in real time; when the steam pressure does not meet the requirement, the third control valve and the fourth control valve are closed until the pressure meets the requirement; when low-pressure steam is required, the third control valve is opened and the fourth control valve is closed to discharge the low-pressure steam from the first steam outlet; when high-pressure steam is required, the fourth control valve is opened and the third control valve is closed to discharge the low-pressure steam from the second steam outlet after being compressed by the steam compressor.

[0047] Preferably, a second pressure sensor located at the second steam outlet monitors the pressure of the steam, and the operating frequency of the water vapor compressor is controlled according to the difference between the pressure actually measured by the second pressure sensor and the required pressure.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] (1) This invention recovers the heat lost during the process to produce industrial steam, which can replace or supplement existing process steam. Compared with steam generated by burning fossil fuels, this part is a zero-carbon energy source, with no fossil fuel combustion and no pollutant emissions.

[0050] (2) The present invention utilizes the waste heat of exhaust steam in a cascade manner, thereby reducing the irreversible loss in the heat exchange process. When the same amount of exhaust steam heat is recovered, the area of the heat exchanger can be reduced.

[0051] (3) The present invention combines the exhaust steam heat recovery subsystem, the high-temperature steam heat pump subsystem, and the molten salt subsystem. When the exhaust steam is stable and the temperature meets the requirements, the exhaust steam heat recovery subsystem and the high-temperature steam heat pump subsystem are turned on to produce industrial steam. When the exhaust steam is unstable or the temperature does not meet the use requirements of the high-temperature steam heat pump subsystem, the high-temperature steam heat pump subsystem and the exhaust steam heat recovery subsystem are turned off, and the molten salt subsystem is turned on to release heat to the steam generator. The coupling of the above subsystems ensures the stability and continuity of the steam supply.

[0052] (4) In the molten salt subsystem provided by the present invention, the molten salt is preferentially heated by valley electricity, which optimizes the grid load, reduces the system operating cost, and shortens the investment payback period.

[0053] (5) Compared with the existing electric compression high-temperature steam heat pump, the high-temperature steam heat pump subsystem provided by the present invention has a steam generator that directly generates steam, which is different from the conventional hot water plus flash evaporation form. There is no flash evaporation loss, and the overall efficiency is higher.

[0054] (6) The control subsystem provided by the present invention can realize system control through temperature sensors and pressure sensors, and is linked with valves, pumps, and compressors in the system, and the principle and operation are simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 A schematic structural diagram of a steam generator exhaust heat recovery device system is provided in accordance with a specific embodiment of the present invention;

[0056] Among them, 1-first-stage evaporator; 2-second-stage evaporator; 3-exhaust steam preheater; 4-refrigerant compressor; 5-water vapor compressor; 6-steam generator; 7-economizer; 8-molten salt preheater; 9-electric heater; 10-molten salt circulation pump; 11-first steam outlet; 12-second steam outlet; 13-water inlet; 14-molten salt storage tank;

[0057] 101 - return air throttle valve; 102 - first expansion valve; 103 - second expansion valve; 104 - third expansion valve; 105 - first control valve; 106 - second control valve; 107 - third control valve; 108 - fourth control valve; 109 - fifth control valve; 110 - sixth control valve; 111 - seventh control valve; 112 - eighth control valve; 113 - ninth control valve;

[0058] 201 - first temperature sensor; 202 - second temperature sensor; 203 - third temperature sensor; 204 - first pressure sensor; 205 - second pressure sensor. DETAILED DESCRIPTION

[0059] It should be understood that, in the description of the present invention, the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0060] It should be noted that, in the description of the present invention, unless otherwise expressly specified or limited, the terms "disposed," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to direct connections, indirect connections via an intermediate medium, or internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0061] The technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific implementation methods.

[0062] In a specific embodiment, the present invention provides a waste heat recovery device system based on a steam generator, such as Figure 1 As shown, the exhaust steam waste heat recovery device system includes:

[0063] The exhaust steam heat recovery subsystem includes a refrigerant direct expansion high-efficiency heat exchanger. The exhaust steam heat recovery subsystem uses low-temperature, low-pressure refrigerant to directly absorb the waste heat of the hot and wet exhaust steam. The refrigerant evaporates from liquid to gas, and the hot and wet exhaust steam condenses from gas to liquid, achieving heat transfer through dual phase change on both sides.

[0064] A high-temperature steam heat pump subsystem, comprising a steam generator 6, configured to convert water into steam using the heat of exhaust steam;

[0065] A water replenishment preheating subsystem, wherein the water replenishment outlet of the water replenishment preheating subsystem is connected to the water replenishment inlet of the steam generator 6, and the water replenishment preheating subsystem is used to preheat the replenishment water;

[0066] The molten salt subsystem includes a molten salt storage tank 14, the outlet of which is respectively connected to the heat source inlet of the steam generator 6 and the water supply preheating subsystem. The molten salt subsystem is used to heat the molten salt energy storage during low electricity consumption, and to provide heat for preheating water supply and / or heat for the steam generator 6.

[0067] In the steam generator 6 provided by the present invention, when using refrigerant as the heat source, the heat source side is the refrigerant's heat release process, while the cold source side is the water's heat absorption and evaporation process. Both the hot and cold sides undergo phase change heat transfer, improving the overall heat transfer coefficient. The exhaust steam heat recovery subsystem includes a high-efficiency refrigerant direct expansion heat exchanger, the refrigerant outlet of which is connected to the heat source inlet of the steam generator 6. Compared to methods that heat water to a high temperature and then reduce the pressure for flash evaporation to produce steam, the steam generation method of the present invention using the steam generator 6 eliminates pressure differentials and heat energy losses, resulting in improved overall efficiency.

[0068] In some embodiments, the refrigerant direct expansion high-efficiency heat exchanger in the exhaust steam waste heat recovery subsystem includes a primary evaporator 1 and a secondary evaporator 2.

[0069] In some embodiments, the high-temperature steam heat pump subsystem further includes a refrigerant compressor 4 and a return air throttle valve 101 .

[0070] In some embodiments, the heat source inlet of the primary evaporator 1 is connected to the exhaust steam, the heat source outlet of the primary evaporator 1 is connected to the heat source inlet of the secondary evaporator 2, the refrigerant outlet of the primary evaporator 1 is connected to the refrigerant compressor 4 via the return air throttle valve 101, the refrigerant outlet of the secondary evaporator 2 is connected to the refrigerant compressor 4, the outlet of the refrigerant compressor 4 is connected to the heat source inlet of the steam generator 6 via the first control valve 105, and the heat source outlet of the steam generator 6 is connected to the refrigerant inlets of the primary evaporator 1 and the secondary evaporator 2, respectively.

[0071] In the present invention, exhaust steam from the process flows through the primary and secondary evaporators 1 and 2, where it is cooled and releases heat to the refrigerant. The low-temperature, low-pressure refrigerant flows through the two evaporators, absorbing the heat from the exhaust steam and transforming into refrigerant vapor. The refrigerant vapor then passes through the refrigerant compressor 4, where its temperature and pressure increase. The high-temperature, high-pressure refrigerant vapor then flows through the steam generator 6, where it condenses and transfers heat to the feed water, directly heating it to low-pressure steam.

[0072] In some embodiments, the high-temperature steam heat pump subsystem further includes an expansion valve and an economizer 7 .

[0073] In some embodiments, the heat source outlet of the steam generator 6 is connected to the heat source inlet of the economizer 7 via the second control valve 106. The heat source outlet of the steam generator 6 is also connected to the cold source inlet of the economizer 7 via the second control valve 106 and the first expansion valve 102 in sequence. The heat source outlet of the economizer 7 is connected to the refrigerant inlet of the secondary evaporator 2 via the second expansion valve 103. The heat source outlet of the economizer 7 is also connected to the refrigerant inlet of the primary evaporator 1 via the third expansion valve 104. The cold source outlet of the economizer 7 is connected to the refrigerant compressor 4.

[0074] In the present invention, the outlet pipe of steam generator 6 is divided into two paths: one path flows to economizer 7 to release heat, and the other path is reduced in pressure by first expansion valve 102. After being reduced to an intermediate pressure, it flows through economizer 7 to absorb heat, becoming saturated or superheated before entering refrigerant compressor 4 for compression. By providing economizer 7, the present invention further releases heat from the refrigerant, achieving heat recovery and reuse, reducing system energy consumption, and improving the efficiency and performance of the heat pump system.

[0075] In the present invention, the refrigerant at the outlet of the economizer 7 is split into two paths, passing through the second expansion valve 103 and the third expansion valve 104, respectively, before entering the secondary evaporator 2 and the primary evaporator 1. This achieves two-stage evaporation heat exchange, recovering waste heat in a cascaded manner and reducing irreversible heat exchange losses within the evaporators. The refrigerant at the outlet of the primary evaporator 1 passes through the return air throttle valve 101, mixes with the refrigerant at the outlet of the secondary evaporator 2, and enters the refrigerant compressor 4.

[0076] In some embodiments, the high-temperature steam heat pump subsystem further includes a first steam outlet 11 and a second steam outlet 12, the steam outlet of the steam generator 6 is connected to the first steam outlet 11 via a third control valve 107, and the steam outlet of the steam generator 6 is connected to the second steam outlet 12 via a fourth control valve 108 and the water vapor compressor 5 in turn.

[0077] In the present invention, the outlet steam pressure of the steam generator 6 is relatively low. If the process requires a higher quality of steam, a steam compressor 5 is added, and the low-pressure steam is further pressurized by the steam compressor 5 to meet the process requirements.

[0078] In some embodiments, the molten salt subsystem includes a molten salt storage tank 14 , an electric heater 9 and a molten salt circulation pump 10 .

[0079] In the present invention, molten salt storage tank 14 is used to store high-temperature molten salt as a heat energy carrier. An electric heater 9 is provided in molten salt storage tank 14 to heat the molten salt to a predetermined temperature or maintain the temperature of the molten salt. A molten salt circulation pump 10 is used to drive the molten salt stored in molten salt storage tank 14 to perform heat exchange with the make-up water in steam generator 6, thereby evaporating the make-up water to form low-pressure steam.

[0080] In some embodiments, the molten salt storage tank 14 is connected to the heat source inlet of the steam generator 6 through a molten salt circulation pump 10, a fifth control valve 109 is arranged between the molten salt circulation pump 10 and the heat source inlet of the steam generator 6, the heat source outlet of the steam generator 6 is connected to the molten salt storage tank 14 through a sixth control valve 110, and an electric heater 9 is arranged in the molten salt storage tank 14.

[0081] In the present invention, during the energy storage phase, the electric heater 9 heats the molten salt in the molten salt storage tank 14 to a predetermined temperature, or maintains its temperature, to ensure that the molten salt can continuously provide stable thermal energy. During the heat release phase, the molten salt is extracted from the molten salt storage tank 14 by the molten salt circulation pump 10 and transported to the steam generator 6. In the steam generator 6, the molten salt exchanges heat with the make-up water, causing it to evaporate and form steam. After the molten salt releases heat in the steam generator 6, it enters the molten salt storage tank 14 again for heating. The present invention sets up a molten salt storage tank 14 to store a large amount of high-temperature molten salt. When the exhaust steam resource is unstable, the exhaust steam waste heat recovery subsystem and the high-temperature steam heat pump subsystem stop working, and the molten salt storage tank 14 quickly transfers heat energy to the steam generator 6 through the molten salt circulation pump 10, thereby improving the stability and continuity of the entire steam supply. Among them, the electric heater 9 in the molten salt storage tank 14 preferably uses valley electricity for heating, optimizes the grid load, reduces the system operating cost, and shortens the investment payback period.

[0082] In some embodiments, the water replenishment preheating subsystem includes an exhaust steam preheater 3 , a molten salt preheater 8 and a water replenishment port 13 .

[0083] In some embodiments, the heat source inlet of the exhaust steam preheater 3 is connected to the heat source outlet of the secondary evaporator 2, the water supply port 13 is connected to the cold source inlet of the exhaust steam preheater 3 through the seventh control valve 111, and the cold source outlet of the exhaust steam preheater 3 is connected to the water supply inlet of the steam generator 6.

[0084] In the present invention, exhaust steam typically carries some usable thermal energy after heat exchange through the primary and secondary evaporators 1 and 2. Therefore, an exhaust steam preheater 3 is provided to exchange heat between the exhaust steam at the outlets of the two evaporators and feed water, further lowering the exhaust steam temperature and raising the feed water temperature at the inlet of the steam generator 6. If the exhaust steam heat is insufficient to heat the feed water to the target temperature, the heat from molten salt can be used to heat the feed water. Specifically, the feed water in the present invention is divided into two routes: one route is heated by the exhaust steam preheater 3, and the other route is heated by the molten salt preheater 8. The two routes of feed water are then mixed and enter the steam generator 6, where they are then heated to low-pressure steam by the heat medium within the steam generator 6.

[0085] In the present invention, the primary evaporator 1, the secondary evaporator 2 and the exhaust steam preheater 3 are specifically heat exchangers. For example, a heat exchanger with a wide flow channel can be used, and a higher exhaust steam flow rate can be designed to prevent blockage. When the exhaust steam contains high-viscosity pollutants, solid particles or a large amount of fibers, a fin plate heat exchanger can be used.

[0086] In some embodiments, the water supply port 13 is also connected to the cold source inlet of the molten salt preheater 8 through the eighth control valve 112, the molten salt storage tank 14 is connected to the heat source inlet of the molten salt preheater 8 through the molten salt circulation pump 10, the heat source outlet of the molten salt preheater 8 is connected to the molten salt storage tank 14 via the ninth control valve 113, and the cold source outlet of the molten salt preheater 8 is connected to the water supply inlet of the steam generator 6.

[0087] In some embodiments, the exhaust steam heat recovery device system further includes a control subsystem.

[0088] In some embodiments, the control subsystem includes a temperature sensor and a pressure sensor.

[0089] In some embodiments, a first temperature sensor 201 is provided at the heat source inlet of the primary evaporator 1 to monitor the temperature of the exhaust steam entering the primary evaporator 1 .

[0090] In some embodiments, a second temperature sensor 202 is provided at the water supply inlet of the steam generator 6 .

[0091] In some embodiments, a third temperature sensor 203 is provided in the molten salt storage tank 14 .

[0092] In some embodiments, a first pressure sensor 204 is provided at the steam outlet of the steam generator 6 .

[0093] In some embodiments, a second pressure sensor 205 is provided at the outlet of the water vapor compressor 5 .

[0094] In another specific embodiment, the present invention provides a method for recovering waste heat from exhaust steam of a steam generator 6. The method uses a device system for recovering waste heat from exhaust steam of a steam generator 6 provided in a specific embodiment of the present invention. The method includes the following steps:

[0095] Control the exhaust steam waste heat recovery subsystem, using low-temperature and low-pressure refrigerant to directly absorb the waste heat of hot and wet exhaust steam. The refrigerant evaporates from liquid to gas, and the hot and wet exhaust steam condenses from gas to liquid, achieving heat transfer through dual phase change on both sides.

[0096] Controlling the high-temperature steam heat pump subsystem to absorb heat from the exhaust steam and transfer the heat to the steam generator 6, so that the steam generator 6 converts water into steam;

[0097] Controlling the feed water preheating subsystem to absorb heat from exhaust steam and / or molten salt to preheat feed water, and feeding the preheated feed water into the steam generator 6 as feed water for producing steam;

[0098] The molten salt subsystem is controlled to provide heat to the steam generator 6 so that the steam generator 6 converts water into steam and / or to provide heat to the feed water preheating subsystem so as to preheat the feed water.

[0099] The method provided by the present invention utilizes the aforementioned device system, combining an exhaust steam heat recovery subsystem, a high-temperature steam heat pump subsystem, and a molten salt subsystem. When the exhaust steam is stable and meets the required temperature, the exhaust steam heat recovery and high-temperature steam heat pump subsystems are activated to produce industrial steam. When the exhaust steam is unstable or the temperature does not meet the requirements for the high-temperature steam heat pump subsystem, the exhaust steam heat recovery and high-temperature steam heat pump subsystems are shut down, and the molten salt subsystem is activated to release heat to the steam generator 6. This coupling of subsystems ensures a stable and continuous steam supply.

[0100] In some embodiments, the method comprises the following steps:

[0101] When the exhaust steam temperature meets the requirement, the first control valve 105 and the second control valve 106 are opened, the fifth control valve 109 and the sixth control valve 110 are closed, and the exhaust steam heat recovery subsystem and the high-temperature steam heat pump subsystem are put into operation (during operation, the return air throttle valve 101, the first expansion valve 102, the second expansion valve 103, the third expansion valve 104 and the refrigerant compressor 4 are all opened):

[0102] The exhaust steam flows through the heat source side of the primary evaporator 1 and the secondary evaporator 2 in sequence, releasing heat to the refrigerant to generate refrigerant steam. The refrigerant steam generated by the primary evaporator 1 passes through the return air throttle valve 101 and mixes with the refrigerant steam generated by the secondary evaporator 2. The mixed refrigerant steam is compressed by the refrigerant compressor 4, and then enters the steam generator 6 to release heat and heat water into low-pressure steam. The condensed refrigerant is divided into two streams, one of which flows into the heat source side of the economizer 7 to release heat, and the other flows into the coolant of the economizer 7 after being reduced in pressure by the first expansion valve 102. The refrigerant is then compressed in the refrigerant compressor 4 and sent to the steam generator 6 to provide heat. After releasing heat in the economizer 7, the refrigerant passes through the third expansion valve 104 and the second expansion valve 103 and returns to the cold source side of the first evaporator 1 and the second evaporator 2 respectively to continue absorbing the heat of the exhaust steam. The low-pressure steam generated by the steam generator 6 is divided into two streams, one of which is discharged through the first steam outlet 11, and the other is discharged through the second steam outlet 12 after the pressure is increased by the water vapor compressor 5.

[0103] When the exhaust steam is unstable or the temperature does not meet the requirements, the first control valve 105 and the second control valve 106 are closed, the fifth control valve 109 and the sixth control valve 110 are opened, and the molten salt heat release subsystem operates (during operation, the refrigerant compressor 4, the first expansion valve 102, the second expansion valve 103, the third expansion valve 104 and the return air throttle valve 101 in the high-temperature steam heat pump subsystem remain closed): the molten salt circulation pump 10 transports the molten salt in the molten salt storage tank 14 to the steam generator 6 to release heat and heat the water into low-pressure steam. The molten salt after releasing heat returns to the molten salt storage tank 14.

[0104] In some embodiments, the method includes the following steps: a second temperature sensor 202 located at the feed water inlet of the steam generator 6 monitors the feed water temperature in real time; when the exhaust steam temperature meets the preheating feed water requirement, the seventh control valve 111 is opened and the eighth control valve 112 is closed, and the feed water entering from the feed water inlet 13 enters the steam generator 6 after heat exchange in the exhaust steam preheater 3; when the exhaust steam temperature cannot meet the preheating feed water requirement, the seventh control valve 111 and the eighth control valve 112 are opened and the opening degree is adjusted to adjust the distribution of the feed water between the exhaust steam preheater 3 and the molten salt preheater 8, and one stream of the feed water entering from the feed water inlet 13 enters the steam generator 6 after heat exchange in the exhaust steam preheater 3, and the other stream enters the steam generator 6 after heat exchange in the molten salt preheater 8; the molten salt circulation pump 10 transports the molten salt in the molten salt storage tank 14 to the molten salt preheater 8 to provide heat, and then returns to the molten salt storage tank 14 through the ninth control valve 113.

[0105] In some embodiments, the method includes the following steps: the third temperature sensor 203 in the molten salt storage tank 14 monitors the temperature of the molten salt, and when the temperature does not meet the requirement, the electric heater 9 uses valley electricity to heat the molten salt.

[0106] In some embodiments, the method includes the following steps: the first pressure sensor 204 located at the steam outlet of the steam generator 6 monitors the steam pressure in real time; when the steam pressure does not meet the requirement, the third control valve 107 and the fourth control valve 108 are closed until the pressure meets the requirement; when low-pressure steam is required, the third control valve 107 is opened and the fourth control valve 108 is closed, so that the low-pressure steam is discharged from the first steam outlet 11; when high-pressure steam is required, the fourth control valve 108 is opened and the third control valve 107 is closed, so that the low-pressure steam is compressed by the steam compressor and discharged from the second steam outlet 12.

[0107] In some embodiments, the second pressure sensor 205 located at the second steam outlet 12 monitors the steam pressure, and the operating frequency of the water vapor compressor 5 is controlled according to the difference between the pressure measured by the second pressure sensor 205 and the required pressure.

[0108] In the present invention, the molten salt circulation pump 10 is a variable frequency pump, and its frequency is controlled by both the temperature of the first temperature sensor 201 and the temperature of the second temperature sensor 202: when the temperature of the first temperature sensor 201 is too low, the molten salt subsystem is turned on, and the molten salt circulation pump 10 is required to provide the driving force for the flow of molten salt; when the make-up water also requires molten salt heating, the second temperature sensor 202 controls the flow distribution of the make-up water in the exhaust steam preheater 3 and the molten salt preheater 8. Only when the exhaust steam can meet all the heat supply for make-up water heating, molten salt heating is not required, and at this time, the molten salt circulation pump 10 is no longer required to provide power for the molten salt to flow through the molten salt preheater 8.

[0109] In summary, the present invention can recycle the heat of exhaust steam lost in industrial processes to produce industrial steam as a substitute or supplement for existing industrial steam, thereby improving energy utilization efficiency, reducing fossil fuel combustion, and reducing pollutant emissions.

[0110] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A steam generator exhaust heat recovery device system, characterized in that: The exhaust steam waste heat recovery device system includes: The exhaust steam heat recovery subsystem includes a refrigerant direct expansion high-efficiency heat exchanger. The exhaust steam heat recovery subsystem uses low-temperature, low-pressure refrigerant to directly absorb the waste heat of the hot and wet exhaust steam. The refrigerant evaporates from liquid to gas, and the hot and wet exhaust steam condenses from gas to liquid, achieving heat transfer through dual phase change on both sides. A high-temperature steam heat pump subsystem, comprising a steam generator, configured to convert water into steam using the heat of exhaust steam; A water supply preheating subsystem, wherein the water supply outlet of the water supply preheating subsystem is connected to the water supply inlet of the steam generator, and the water supply preheating subsystem is used to preheat the water supply; The molten salt subsystem includes a molten salt storage tank, the outlet of which is respectively connected to the heat source inlet of the steam generator and the water preheating subsystem. The molten salt subsystem is used to heat the molten salt energy storage during low electricity consumption, and to provide heat for preheating water and / or heat for the steam generator.

2. The exhaust steam waste heat recovery device system according to claim 1, characterized in that: The refrigerant direct expansion high-efficiency heat exchanger in the exhaust steam waste heat recovery subsystem includes a primary evaporator and a secondary evaporator; Preferably, the high-temperature steam heat pump subsystem further includes a refrigerant compressor and a return air throttle valve; Preferably, the heat source inlet of the primary evaporator is connected to the exhaust steam, the heat source outlet of the primary evaporator is connected to the heat source inlet of the secondary evaporator, the refrigerant outlet of the primary evaporator is connected to the refrigerant compressor via a return air throttle valve, the refrigerant outlet of the secondary evaporator is connected to the refrigerant compressor, the outlet of the refrigerant compressor is connected to the heat source inlet of the steam generator via a first control valve, and the heat source outlet of the steam generator is connected to the refrigerant inlets of the primary evaporator and the secondary evaporator respectively; Preferably, the high-temperature steam heat pump subsystem further includes an expansion valve and an economizer; Preferably, the heat source outlet of the steam generator is connected to the heat source inlet of the economizer via a second control valve, the heat source outlet of the steam generator is further connected to the cold source inlet of the economizer via the second control valve and the first expansion valve in sequence, the heat source outlet of the economizer is connected to the refrigerant inlet of the secondary evaporator via the second expansion valve, the heat source outlet of the economizer is further connected to the refrigerant inlet of the primary evaporator via a third expansion valve, and the cold source outlet of the economizer is connected to the refrigerant compressor; Preferably, the high-temperature steam heat pump subsystem further includes a first steam outlet and a second steam outlet, the steam outlet of the steam generator is connected to the first steam outlet via a third control valve, and the steam outlet of the steam generator is connected to the second steam outlet via a fourth control valve and a water vapor compressor in turn.

3. The exhaust steam waste heat recovery device system according to claim 1 or 2, characterized in that: The molten salt subsystem includes a molten salt storage tank, an electric heater and a molten salt circulation pump; Preferably, the molten salt storage tank is connected to the heat source inlet of the steam generator through a molten salt circulation pump, a fifth control valve is arranged between the molten salt circulation pump and the heat source inlet of the steam generator, the heat source outlet of the steam generator is connected to the molten salt storage tank through a sixth control valve, and an electric heater is arranged in the molten salt storage tank.

4. The exhaust steam waste heat recovery device system according to claim 3, characterized in that: The water replenishment and preheating subsystem includes an exhaust steam preheater, a molten salt preheater and a water replenishment port; Preferably, the heat source inlet of the exhaust steam preheater is connected to the heat source outlet of the secondary evaporator, the water supply port is connected to the cold source inlet of the exhaust steam preheater through a seventh control valve, and the cold source outlet of the exhaust steam preheater is connected to the water supply inlet of the steam generator; Preferably, the water supply port is also connected to the cold source inlet of the molten salt preheater through an eighth control valve, the molten salt storage tank is connected to the heat source inlet of the molten salt preheater through a molten salt circulation pump, the heat source outlet of the molten salt preheater is connected to the molten salt storage tank via a ninth control valve, and the cold source outlet of the molten salt preheater is connected to the water supply inlet of the steam generator.

5. The exhaust steam waste heat recovery device system according to claim 4, characterized in that: The exhaust steam waste heat recovery device system also includes a control subsystem; Preferably, the control subsystem includes a temperature sensor and a pressure sensor; Preferably, a first temperature sensor is provided at the heat source inlet of the first-stage evaporator for monitoring the exhaust steam temperature entering the first-stage evaporator; Preferably, a second temperature sensor is provided at the water supply inlet of the steam generator; Preferably, a third temperature sensor is provided in the molten salt storage tank; Preferably, a first pressure sensor is provided at the steam outlet of the steam generator; Preferably, a second pressure sensor is provided at the outlet of the water vapor compressor.

6. A method for recovering waste heat from exhaust steam of a steam generator, characterized in that: The method adopts the device system based on exhaust steam heat recovery of a steam generator according to any one of claims 1 to 5, and the method comprises the following steps: Control the exhaust steam waste heat recovery subsystem, using low-temperature and low-pressure refrigerant to directly absorb the waste heat of hot and wet exhaust steam. The refrigerant evaporates from liquid to gas, and the hot and wet exhaust steam condenses from gas to liquid, achieving heat transfer through dual phase change on both sides. Control the high-temperature steam heat pump subsystem to absorb heat from the exhaust steam and transfer the heat to the steam generator, which converts water into steam; Controlling the feed water preheating subsystem to absorb heat from exhaust steam and / or molten salt to preheat feed water, and then feeding the preheated feed water into the steam generator as feed water for steam production; The molten salt subsystem is controlled to provide heat to the steam generator so that the steam generator converts water into steam and / or to provide heat to the feed water preheating subsystem so as to preheat the feed water.

7. The method according to claim 6, characterized in that The method comprises the following steps: When the exhaust steam temperature meets the requirements, open the first and second control valves, close the fifth and sixth control valves, and the exhaust steam heat recovery subsystem and high-temperature steam heat pump subsystem start operation: The exhaust steam flows through the heat source side of the primary evaporator and the secondary evaporator in sequence, releasing heat to the refrigerant to generate refrigerant steam. The refrigerant steam generated by the primary evaporator passes through the return air throttle valve and mixes with the refrigerant steam generated by the secondary evaporator. The mixed refrigerant steam is compressed by the refrigerant compressor and then enters the steam generator to release heat and heat the water into low-pressure steam. The condensed refrigerant is divided into two streams, one of which flows into the heat source side of the economizer to release heat, and the other flows into the cold source side of the economizer after being reduced in pressure by the first expansion valve to absorb heat to obtain saturated or supersaturated refrigerant steam. It then enters the refrigerant compressor for compression and continues to be sent to the steam generator to provide heat. The refrigerant that has released heat in the economizer passes through the third expansion valve and the second expansion valve respectively and returns to the cold source side of the primary evaporator and the secondary evaporator and continues to absorb the heat of the exhaust steam. The low-pressure steam generated by the steam generator is divided into two streams, one of which is discharged through the first steam outlet, and the other is discharged through the second steam outlet after the water vapor compressor increases its pressure. When the exhaust steam is unstable or the temperature does not meet the requirements, the first control valve and the second control valve are closed, the fifth control valve and the sixth control valve are opened, and the molten salt heat release subsystem operates: the molten salt circulation pump transports the molten salt in the molten salt storage tank to the steam generator to release heat and heat the water into low-pressure steam. The molten salt after releasing heat returns to the molten salt storage tank.

8. The method according to claim 7, characterized in that The method comprises the following steps: a second temperature sensor located at a feed water inlet of a steam generator monitors the feed water temperature in real time; when the exhaust steam temperature meets the requirement for preheating feed water, a seventh control valve is opened and an eighth control valve is closed, so that the feed water entering from the feed water inlet undergoes heat exchange in an exhaust steam preheater before entering the steam generator; when the exhaust steam temperature does not meet the requirement for preheating feed water, the seventh control valve and the eighth control valve are opened and their openings are adjusted to adjust the distribution of the feed water between the exhaust steam preheater and the molten salt preheater; one stream of the feed water entering from the feed water inlet undergoes heat exchange in the exhaust steam preheater before entering the steam generator, and the other stream of the feed water undergoes heat exchange in the molten salt preheater before entering the steam generator; a molten salt circulation pump transports molten salt in a molten salt storage tank to the molten salt preheater to provide heat, and then returns to the molten salt storage tank through the ninth control valve.

9. The method according to claim 8, characterized in that The method comprises the following steps: a third temperature sensor in the molten salt storage tank monitors the temperature of the molten salt; when the temperature does not meet the requirement, an electric heater utilizes valley electricity to heat the molten salt.

10. The method according to claim 9, characterized in that The method comprises the following steps: a first pressure sensor located at a steam outlet of a steam generator monitors the steam pressure in real time; when the steam pressure does not meet the requirement, closing a third control valve and a fourth control valve until the pressure reaches the standard; when low-pressure steam is required, opening the third control valve and closing the fourth control valve to discharge the low-pressure steam from the first steam outlet; and when high-pressure steam is required, opening the fourth control valve and closing the third control valve to discharge the low-pressure steam from the second steam outlet after being compressed by a steam compressor; Preferably, a second pressure sensor located at the second steam outlet monitors the pressure of the steam, and the operating frequency of the water vapor compressor is controlled according to the difference between the pressure actually measured by the second pressure sensor and the required pressure.

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