Method for heat exchange of molten salt boiler and molten salt boiler system

Abstract

The application discloses a molten salt boiler heat exchange method and a molten salt boiler system. The molten salt boiler heat exchange method comprises the following steps: conveying high-temperature molten salt into a first superheater, the high-temperature molten salt can exchange heat with slightly superheated steam, and then secondary high-temperature molten salt and high-temperature superheated steam are obtained; conveying the secondary high-temperature molten salt into a second superheater, conveying waste heat molten salt into the second superheater, the secondary high-temperature molten salt and the waste heat molten salt can exchange heat with saturated steam, and then intermediate molten salt and slightly superheated steam are obtained; conveying the intermediate molten salt into an evaporator, and exchanging heat between the intermediate molten salt and saturated water in the evaporator, which is conveyed into the evaporator by a steam drum, so that heat exchange molten salt and a steam-water mixture are obtained, and the steam-water mixture is returned to the steam drum; conveying the heat exchange molten salt into an economizer, and exchanging heat between the heat exchange molten salt and feed water in the economizer, so that low-temperature molten salt and secondary saturated water are obtained; and conveying the secondary saturated water into the steam drum as make-up water. The application can effectively improve the quality of steam and effectively realize the step-by-step utilization of molten salt energy.

Description

Technical Field

[0001] The present invention relates to the field of boilers, and in particular to a molten salt boiler heat exchange method and a molten salt boiler system. Background Art

[0002] Molten salt furnaces utilize the lower melting point of salts to heat and melt the material. A variety of salts are used in molten salt furnaces, including potassium chloride, sodium chloride, calcium chloride, and lithium chloride. Currently, dual-heat-source molten salt boilers are the most common. However, these boilers typically use two molten salts simultaneously as heat sources, resulting in inefficient cascaded energy utilization. Summary of the Invention

[0003] The object of the present invention is to provide a molten salt boiler heat exchange method and a molten salt boiler system, which can effectively improve the quality of steam and effectively realize the cascade utilization of molten salt energy.

[0004] The purpose of the present invention can be achieved by adopting the following technical solutions:

[0005] The present invention provides a molten salt boiler heat exchange method, comprising:

[0006] The high-temperature molten salt is transported to the first superheater, where it can exchange heat with the slightly superheated steam obtained from the second superheater to obtain sub-high-temperature molten salt and high-temperature superheated steam;

[0007] The sub-high temperature molten salt is transported to the second superheater, and the waste heat molten salt is transported to the second superheater. The sub-high temperature molten salt and the waste heat molten salt can exchange heat with the saturated steam transported from the drum to the second superheater to obtain intermediate molten salt and slightly superheated steam;

[0008] The intermediate molten salt is transported to the evaporator and exchanges heat with the saturated water transported to the evaporator from the drum to obtain a heat exchange molten salt and steam-water mixture, which is then returned to the drum;

[0009] The heat exchange molten salt is transported to the economizer and exchanges heat with the feed water transported to the economizer to obtain low-temperature molten salt and subsaturated water;

[0010] The sub-saturated water is transported to the steam drum as make-up water.

[0011] In a preferred embodiment of the present invention, the molten salt boiler heat exchange method further includes: transporting the low-temperature molten salt obtained after heat exchange in the economizer into a low-temperature molten salt tank.

[0012] In a preferred embodiment of the present invention, the molten salt boiler heat exchange method further includes: transporting at least part of the low-temperature molten salt in the low-temperature molten salt tank to the molten salt furnace; and transporting at least part of the low-temperature molten salt in the low-temperature molten salt tank to the steel plant process equipment.

[0013] In a preferred embodiment of the present invention, the high-temperature molten salt comes from a molten salt furnace.

[0014] In a preferred embodiment of the present invention, the temperature of the high-temperature molten salt is 500-580°C, the temperature of the waste heat molten salt is 400-500°C, the temperature of the low-temperature molten salt is less than 300°C, the temperature of the high-temperature superheated steam is greater than 450°C, and the temperature of the slightly superheated steam is less than 450°C.

[0015] In a preferred embodiment of the present invention, the waste heat molten salt is obtained by heat exchange of molten salt through steel plant process equipment, and the steel plant process equipment includes the converter flue of the steelmaking plant, the waste heat boiler of the steel rolling and the steel rolling process cooling equipment.

[0016] The present invention also provides a molten salt boiler system, comprising a molten salt furnace, a first superheater, a second superheater, an evaporator, an economizer, a low-temperature molten salt tank and a steam drum; the molten salt inlet and the molten salt outlet of the first superheater are respectively connected to the outlet of the molten salt furnace and the first molten salt inlet of the second superheater, the steam inlet and the steam outlet of the first superheater are respectively connected to a slightly superheated steam pipeline and a high-temperature superheated steam pipeline, the second molten salt inlet, the molten salt outlet, the saturated steam inlet and the steam outlet of the second superheater are respectively connected to the waste heat molten salt pipeline, the molten salt inlet, the saturated steam pipeline and the slightly superheated steam pipeline of the evaporator, and the waste heat molten salt pipeline is used to transport waste heat molten salt; the molten salt outlet of the evaporator is connected to the molten salt inlet of the economizer, and the circulating liquid inlet and the circulating liquid outlet of the evaporator are both connected to the steam drum; the molten salt outlet, the feed water inlet and the sub-saturated water outlet of the economizer are respectively connected to the low-temperature molten salt tank, the feed water pipeline and the steam drum.

[0017] In a preferred embodiment of the present invention, the end of the waste heat molten salt pipeline extending into the second superheater is connected to a plurality of branch pipelines.

[0018] In a preferred embodiment of the present invention, the outlet of the low-temperature molten salt tank is further connected to a first outlet pipeline and a second outlet pipeline, the first outlet pipeline is connected to the molten salt furnace, and the second outlet pipeline is used to connect to the steel plant process equipment.

[0019] In a preferred embodiment of the present invention, the molten salt boiler system adopts the above-mentioned molten salt boiler heat exchange method for heat exchange.

[0020] As described above, the heat exchange method and system of the present invention utilize two superheaters, wherein high-temperature molten salt is passed into the first superheater for heat exchange and then into the second superheater, and waste heat molten salt is passed into the second superheater. The cooled high-temperature molten salt and waste heat molten salt are first used to heat the saturated steam to obtain slightly superheated steam, and then the high-temperature molten salt is used to further heat the slightly superheated steam to obtain high-temperature superheated steam. The saturated steam generated by the drum can be gradually heated to high-temperature superheated steam, and the temperature of the high-temperature superheated steam is as high as possible. At the same time, the high-temperature molten salt is fed into the first superheater, and the waste heat molten salt is fed into the second superheater. After the molten salt is fully released in the superheater, it flows out of the superheater, enters the evaporator and economizer in sequence, and flows out after cooling. In this way, the waste heat of the molten salt can be fully utilized, effectively realizing the cascade utilization of the waste heat molten salt and the energy of the high-temperature molten salt, and generating high-quality high-temperature superheated steam. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The following drawings are only intended to illustrate and explain the present invention, and are not intended to limit the scope of the present invention.

[0022] in:

[0023] Figure 1 This is a structural schematic diagram of the molten salt boiler system provided by the present invention.

[0024] Description of Figure Numbers:

[0025] 100. Molten salt furnace;

[0026] 200, first superheater; 201, slightly superheated steam pipeline; 202, high-temperature superheated steam pipeline;

[0027] 300, second superheater; 301, waste heat molten salt pipeline; 302, saturated steam pipeline;

[0028] 400, evaporator;

[0029] 500, economizer;

[0030] 600. Low-temperature molten salt tank; 601. First outlet pipeline; 602. Second outlet pipeline. DETAILED DESCRIPTION

[0031] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described with reference to the accompanying drawings.

[0032] like Figure 1 As shown, the present application provides a molten salt boiler heat exchange method, comprising:

[0033] The high-temperature molten salt is transported to the first superheater 200, where it can exchange heat with the slightly superheated steam obtained in the second superheater 300 to obtain sub-high-temperature molten salt and high-temperature superheated steam;

[0034] The sub-high temperature molten salt is transported to the second superheater 300, and the waste heat molten salt is transported to the second superheater 300. The sub-high temperature molten salt and the waste heat molten salt can exchange heat with the saturated steam transported from the drum to the second superheater 300 to obtain intermediate molten salt and slightly superheated steam;

[0035] The intermediate molten salt is transported to the evaporator 400 and exchanges heat with the saturated water transported to the evaporator 400 from the steam drum to obtain a heat exchange molten salt and a steam-water mixture, which is then returned to the steam drum;

[0036] The heat exchange molten salt is transported into the economizer 500 and exchanges heat with the feed water transported into the economizer 500 to obtain low-temperature molten salt and subsaturated water;

[0037] The sub-saturated water is transported to the steam drum as make-up water.

[0038] Therefore, the heat exchange method of the present application utilizes two superheaters, and the high-temperature molten salt is passed into the first superheater 200 for heat exchange and then into the second superheater 300, and the waste heat molten salt is passed into the second superheater 300. The cooled high-temperature molten salt and the waste heat molten salt are first used to heat the saturated steam to obtain slightly superheated steam, and then the high-temperature molten salt is used to further heat the slightly superheated steam to obtain high-temperature superheated steam, which can gradually heat the saturated steam generated by the drum to high-temperature superheated steam, and the temperature of the high-temperature superheated steam is as high as possible. At the same time, the high-temperature molten salt is fed into the first superheater 200, and the waste heat molten salt is fed into the second superheater 300. After the molten salt is fully released in the superheater, it flows out of the superheater and enters the evaporator 400 and the economizer 500 in sequence. It flows out after cooling, and then the waste heat of the molten salt can be fully utilized, effectively realizing the cascade utilization of the waste heat molten salt and the energy of the high-temperature molten salt, and generating high-quality high-temperature superheated steam.

[0039] In a specific implementation, the molten salt boiler heat exchange method further includes: transporting the low-temperature molten salt obtained after heat exchange in the economizer 500 into the low-temperature molten salt tank 600 .

[0040] Furthermore, in order to realize the recycling of low-temperature molten salt with a relatively low temperature, the molten salt boiler heat exchange method further includes:

[0041] transporting at least a portion of the low-temperature molten salt in the low-temperature molten salt tank 600 into the molten salt furnace 100;

[0042] At least a portion of the low-temperature molten salt in the low-temperature molten salt tank 600 is transported to the process equipment of the steel plant.

[0043] The high-temperature molten salt mentioned above comes from the molten salt furnace 100 .

[0044] The molten salt furnace 100 heats the molten salt by introducing coal gas to produce high-temperature molten salt. It should be noted that the solution of this embodiment is primarily applicable to operating conditions where the flow rate of high-temperature molten salt is insufficient and saturated steam cannot be superheated to high-temperature superheated steam alone. Steel mills generally have excess coal gas, and the amount of excess coal gas determines the amount of high-temperature molten salt that can be produced using the molten salt furnace 100. When the steel mill has less excess coal gas, the amount of high-temperature molten salt produced by the molten salt furnace 100 is also less, making it impossible to heat saturated steam to high-temperature superheated steam alone.

[0045] Therefore, in this embodiment, two superheaters are provided. After the high-temperature molten salt enters the molten salt inlet of the first superheater 200, it first heats the already preliminarily superheated superheated steam (i.e., slightly superheated steam delivered by the second superheater 300), further increasing the temperature of the superheated steam to obtain high-temperature superheated steam. After the high-temperature molten salt absorbs heat, its temperature decreases to form a sub-high-temperature molten salt. The temperature of the sub-high-temperature molten salt is set to be consistent with the temperature of the waste heat molten salt (the two temperatures are close). The waste heat molten salt is connected to the second superheater 300 and is evenly delivered to the second superheater 300. Afterwards, the sub-high-temperature molten salt and the waste heat molten salt jointly heat the saturated steam, heating the saturated steam to slightly superheated steam.

[0046] In this embodiment, the temperature of the high-temperature molten salt is 500-580°C, the temperature of the waste heat molten salt is 400-500°C, the temperature of the low-temperature molten salt is less than 300°C, the temperature of the high-temperature superheated steam is greater than 450°C, and the temperature of the slightly superheated steam is less than 450°C.

[0047] Waste heat molten salt can also be called medium-temperature molten salt, which can be transported intermittently or continuously according to actual working conditions. Waste heat molten salt is obtained by heat exchange between molten salt and steel mill process equipment. The steel mill process equipment includes the converter flue of the steel mill, the waste heat boiler of the steel rolling mill, and the cooling equipment of the steel rolling process. That is, the waste heat molten salt in this embodiment is formed by heat exchange between molten salt and the steel mill process equipment, and the steel mill process equipment transfers waste heat to the molten salt, so that the molten salt is heated and formed into molten salt with waste heat. For example, the steel mill process equipment can be the converter flue of the steel mill, and the molten salt is heat exchanged with the flue gas in the converter flue to obtain waste heat molten salt; for another example, the steel mill process equipment can also be the waste heat boiler of the steel rolling mill, and the molten salt is heat exchanged with the waste heat of the waste heat boiler to obtain waste heat molten salt; for another example, the steel mill process equipment can also be the cooling equipment of the steel rolling process, and the molten salt is heat exchanged with the high-temperature material in the equipment to obtain waste heat molten salt, while achieving a cooling effect on the high-temperature material.

[0048] Generally, the two superheaters are made of high temperature resistant materials, and the evaporator 400 is generally made of carbon steel pipe.

[0049] Further, refer to Figure 1The present application also provides a dual-channel molten salt boiler system, comprising a molten salt furnace 100, a first superheater 200, a second superheater 300, an evaporator 400, an economizer 500, a low-temperature molten salt tank 600 and a steam drum; the molten salt inlet and the molten salt outlet of the first superheater 200 are respectively connected to the outlet of the molten salt furnace 100 and the first molten salt inlet of the second superheater 300, the steam inlet and the steam outlet of the first superheater 200 are respectively connected to the micro-superheated steam pipeline 201 and the high-temperature superheated steam pipeline 202, and the second molten salt inlet of the second superheater 300 is respectively connected to the micro-superheated steam pipeline 201 and the high-temperature superheated steam pipeline 202. The inlet, molten salt outlet, saturated steam inlet and steam outlet are respectively connected to the waste heat molten salt pipeline 301, the molten salt inlet of the evaporator 400, the saturated steam pipeline 302 and the slightly superheated steam pipeline 201. The waste heat molten salt pipeline 301 is used to transport waste heat molten salt; the molten salt outlet of the evaporator 400 is connected to the molten salt inlet of the economizer 500, and the circulating liquid inlet and circulating liquid outlet of the evaporator 400 are both connected to the steam drum; the molten salt outlet, feed water inlet and subsaturated water outlet of the economizer 500 are respectively connected to the low-temperature molten salt tank 600, the feed water pipeline and the steam drum.

[0050] The entire system can make full use of the heat of molten salt, realize cascade utilization of energy, and generate high-temperature superheated steam.

[0051] Furthermore, the end of the waste heat molten salt pipeline 301 extending into the second superheater 300 is connected to a plurality of branched pipelines, so that the waste heat molten salt can be transported to the second superheater 300 more evenly.

[0052] In order to achieve the recycling of low-temperature molten salt with a lower temperature, the outlet of the low-temperature molten salt tank 600 is also connected to a first outlet pipeline 601 and a second outlet pipeline 602. The first outlet pipeline 601 is connected to the molten salt furnace 100; the second outlet pipeline 602 is used to connect to the steel plant process equipment to reheat the low-temperature molten salt to form waste heat molten salt for recycling.

[0053] The system in this embodiment can use the above-mentioned heat exchange method to perform heat exchange.

[0054] In more detail, the working process of the dual heat source molten salt boiler structure in this embodiment is as follows:

[0055] Two steam superheaters are set up, and the high-temperature molten salt obtained from the outlet of the molten salt furnace 100 is introduced into the molten salt inlet of the first superheater 200 to heat the slightly superheated steam, further increasing the superheat of the slightly superheated steam to obtain high-temperature superheated steam. The medium-temperature molten salt recovered from waste heat (that is, waste heat molten salt) is introduced into the second molten salt inlet of the second superheater 300, and after mixing with the cooled high-temperature molten salt (that is, sub-high temperature molten salt) obtained from the first superheater 200, the saturated steam transported from the steam drum through the saturated steam pipeline 302 is heated to heat the saturated steam into slightly superheated steam (because the temperature of the sub-high temperature molten salt and the waste heat molten salt is not high enough, the superheat of the saturated steam is not enough, and high-temperature superheated steam cannot be obtained. At this time, slightly superheated steam with a temperature lower than that of the high-temperature superheated steam is obtained), thereby improving the system. Efficiency. The steam superheater is an indirect heat exchanger, with one side being the molten salt side and the other side being the steam side.

[0056] The intermediate molten salt obtained from the second superheater 300 is transported to the evaporator 400, and the saturated water in the steam drum enters the evaporator 400 through the circulating liquid inlet. The intermediate molten salt heats the saturated water entering the evaporator 400, turning the saturated water into a steam-water mixture and entering the steam drum through the circulating liquid outlet. The steam-water mixture is separated in the steam drum, and the saturated steam generated after separation enters the second superheater 300 through the saturated steam pipeline 302. The saturated water generated after separation drops to the steam drum and then returns to the evaporator 400 through the circulating liquid inlet to enter the next cycle.

[0057] After heat exchange, the intermediate molten salt is converted into lowered heat exchange molten salt. This heat exchange molten salt enters economizer 500, where it heats the feed water entering economizer 500. The heated feed water becomes subsaturated water, which then enters the steam drum to replenish the water supply. After heat exchange, the heat exchange molten salt becomes even lower-temperature molten salt, which enters low-temperature molten salt tank 600.

[0058] The above is only an illustrative embodiment of the present invention and is not intended to limit the scope of the present invention. Any equivalent changes and modifications made by those skilled in the art without departing from the concept and principle of the present invention should fall within the scope of protection of the present invention.

Claims

1. A molten salt boiler heat exchange method, characterized in that: include: The high-temperature molten salt is transported to the first superheater (200), and the high-temperature molten salt can exchange heat with the slightly superheated steam obtained from the second superheater (300) to obtain sub-high-temperature molten salt and high-temperature superheated steam; The sub-high temperature molten salt is transported into the second superheater (300), and the waste heat molten salt is transported into the second superheater (300), wherein the sub-high temperature molten salt and the waste heat molten salt can exchange heat with the saturated steam transported from the drum to the second superheater (300), thereby obtaining intermediate molten salt and slightly superheated steam; The intermediate molten salt is transported into the evaporator (400) and heat-exchanged with the saturated water transported into the evaporator (400) by the steam drum to obtain a heat-exchanged molten salt and a steam-water mixture, and the steam-water mixture is returned and transported into the steam drum; The heat exchange molten salt is transported into the economizer (500) and heat-exchanged with the feed water transported into the economizer (500) to obtain low-temperature molten salt and subsaturated water; The sub-saturated water is transported to the steam drum as makeup water.

2. The molten salt boiler heat exchange method according to claim 1, characterized in that: The molten salt boiler heat exchange method further includes: The low-temperature molten salt obtained after heat exchange in the economizer (500) is transported to a low-temperature molten salt tank (600).

3. The molten salt boiler heat exchange method according to claim 2, characterized in that: The molten salt boiler heat exchange method further includes: transporting at least a portion of the low-temperature molten salt in the low-temperature molten salt tank (600) into the molten salt furnace (100); At least a portion of the low-temperature molten salt in the low-temperature molten salt tank (600) is transported to process equipment in a steel plant.

4. The molten salt boiler heat exchange method according to claim 1, characterized in that: The high-temperature molten salt comes from a molten salt furnace (100).

5. The molten salt boiler heat exchange method according to claim 1, characterized in that: The temperature of the high-temperature molten salt is 500-580°C, the temperature of the waste heat molten salt is 400-500°C, the temperature of the low-temperature molten salt is less than 300°C, the temperature of the high-temperature superheated steam is greater than 450°C, and the temperature of the slightly superheated steam is less than 450°C.

6. The molten salt boiler heat exchange method according to claim 1, characterized in that: The waste heat molten salt is obtained by heat exchange of molten salt through steel plant process equipment, and the steel plant process equipment includes the converter flue of the steel plant, the waste heat boiler of the steel rolling and the steel rolling process cooling equipment.

7. A molten salt boiler system, characterized in that: It includes a molten salt furnace (100), a first superheater (200), a second superheater (300), an evaporator (400), an economizer (500), a low-temperature molten salt tank (600) and a steam drum; The molten salt inlet and the molten salt outlet of the first superheater (200) are respectively connected to the outlet of the molten salt furnace (100) and the first molten salt inlet of the second superheater (300); the steam inlet and the steam outlet of the first superheater (200) are respectively connected to the slightly superheated steam pipeline (201) and the high-temperature superheated steam pipeline (202); the second molten salt inlet, the molten salt outlet, the saturated steam inlet and the steam outlet of the second superheater (300) are respectively connected to the waste heat molten salt pipeline (301), the evaporator (400) The molten salt inlet, the saturated steam pipeline (302) and the slightly superheated steam pipeline (201) are connected to the evaporator (400), and the waste heat molten salt pipeline (301) is used to transport waste heat molten salt; the molten salt outlet of the evaporator (400) is connected to the molten salt inlet of the economizer (500), and the circulating liquid inlet and circulating liquid outlet of the evaporator (400) are both connected to the steam drum; the molten salt outlet, the feed water inlet and the subsaturated water outlet of the economizer (500) are respectively connected to the low-temperature molten salt tank (600), the feed water pipeline and the steam drum.

8. The molten salt boiler system according to claim 7, characterized in that: The end of the waste heat molten salt pipeline (301) extending into the second superheater (300) is connected to a plurality of branched pipelines.

9. The molten salt boiler system according to claim 7, characterized in that: The outlet of the low-temperature molten salt tank (600) is also connected to a first outlet pipeline (601) and a second outlet pipeline (602), wherein the first outlet pipeline (601) is connected to the molten salt furnace (100), and the second outlet pipeline (602) is used to connect to steel plant process equipment.

10. The molten salt boiler system according to claim 7, characterized in that: The molten salt boiler system performs heat exchange using the molten salt boiler heat exchange method according to any one of claims 1 to 6.

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