System and method for producing superheated steam from recovered waste heat

Abstract

The application discloses a system and method for producing superheated steam by recycling waste heat, which comprises a flue structure including a vaporization cooling flue and a high-temperature medium heat exchange flue which are communicated along the conveying direction of flue gas; a steam generating mechanism which is communicated with the vaporization cooling flue and is formed with at least one first heat exchange loop; a superheated steam generating mechanism which comprises a heat exchange structure, the heat exchange structure being communicated with the high-temperature medium heat exchange flue and being formed with at least one second heat exchange loop, and the heat exchange structure being further communicated with the steam output end of the steam generating mechanism; wherein water can exchange heat with the flue gas in the vaporization cooling flue to generate steam, low-temperature molten salt can exchange heat with the flue gas in the high-temperature medium heat exchange flue to generate high-temperature molten salt, and steam can exchange heat with the high-temperature molten salt in the second heat exchange loop to generate superheated steam. The application can generate superheated steam by recycling the waste heat of flue gas, improve the energy recycling efficiency, reduce the energy consumption level in the steel converter steelmaking production process, and reduce the production cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of smelting waste heat recovery, in particular to a system and method for recovering waste heat to produce superheated steam. BACKGROUND

[0002] As a major energy consumer, the steel industry gradually becomes one of the important tasks of energy saving and emission reduction for steel development. Under this background, the maximum recovery of heat energy in a large amount of high-temperature flue gas released in the production process of steel products becomes the key to energy saving and emission reduction. In the converter steelmaking process, the oxygen sprayed by the oxygen lance reacts with carbon and other elements in the molten iron to generate a large amount of mixed high-temperature flue gas mainly composed of carbon monoxide. The temperature of the flue gas at the outlet of the converter can be as high as 1600℃, and this part of flue gas contains a large amount of sensible heat.

[0003] The traditional converter steelmaking converter flue gas waste heat recovery technology uses water as the heat recovery medium to absorb heat from each section of the flue to cool the flue gas, and at the same time, the water generates medium-pressure steam due to heat absorption, which is collected in the steam drum and transmitted to the regenerator, and then converted into low-pressure steam to be supplied to the plant network. The low-pressure steam produced is low-quality saturated steam at about 200℃, but it is easy to condense due to high humidity, and the temperature of the flue gas at the outlet of the flue can only be reduced to 800℃-900℃. SUMMARY

[0004] The purpose of the present application is to provide a system and method for recovering waste heat to produce superheated steam, in order to solve the technical problems of low waste heat recovery efficiency and poor steam quality caused by the current water circulating absorption of heat from each section of the flue to cool the flue gas while the water absorbs heat to generate steam.

[0005] The above-mentioned purpose of the present application can be achieved by using the following technical solutions:

[0006] The present application provides a system for recovering waste heat to produce superheated steam, comprising: a flue structure including a vaporization cooling flue and a high-temperature medium heat exchange flue which are communicated along the conveying direction of the flue gas; a steam generating mechanism which is communicated with the vaporization cooling flue and forms at least one first heat exchange circuit; a superheated steam generating mechanism including a heat exchange structure which is communicated with the high-temperature medium heat exchange flue and forms at least one second heat exchange circuit, and the heat exchange structure is also communicated with the steam output end of the steam generating mechanism; wherein water can exchange heat with the flue gas in the vaporization cooling flue through the first heat exchange circuit to generate steam, low-temperature molten salt can exchange heat with the flue gas in the high-temperature medium heat exchange flue through the second heat exchange circuit to generate high-temperature molten salt, the steam can exchange heat with the high-temperature molten salt in the second heat exchange circuit through the heat exchange structure to generate superheated steam, and the high-temperature molten salt is cooled to form the low-temperature molten salt.

[0007] In the embodiment of the present application, the superheated steam generating mechanism is in communication with the high-temperature medium heat exchange flue, and a low-temperature molten salt circulation loop is further formed, and the low-temperature molten salt in the second heat exchange loop after heat exchange and cooling can enter the low-temperature molten salt circulation loop for circulation.

[0008] In the embodiment of the present application, the heat exchange structure has a high-temperature molten salt input end, a low-temperature molten salt output end, a steam input end and a superheated steam output end, the high-temperature molten salt input end of the heat exchange structure is in communication with the molten salt output end of the high-temperature medium heat exchange flue, the low-temperature molten salt output end of the heat exchange structure is in communication with the molten salt input end of the high-temperature medium heat exchange flue, and the steam input end is in communication with the steam output end of the steam generating mechanism.

[0009] In the embodiment of the present application, the superheated steam generating mechanism further comprises at least one molten salt tank, at least one of the molten salt tanks is in communication with the molten salt output end and the molten salt input end of the high-temperature medium heat exchange flue, and at least one of the molten salt tanks is further in communication with the high-temperature molten salt input end and the low-temperature molten salt output end of the heat exchange structure.

[0010] In the embodiment of the present application, the number of the molten salt tanks is multiple, and the multiple molten salt tanks are low-temperature molten salt tanks and high-temperature molten salt tanks, the high-temperature molten salt input end of the heat exchange structure is in communication with the high-temperature medium heat exchange flue through the high-temperature molten salt tank, and the low-temperature molten salt output end of the heat exchange structure is in communication with the high-temperature medium heat exchange flue through the low-temperature molten salt tank.

[0011] In the embodiment of the present application, a switching valve is arranged between the high-temperature molten salt tank and the molten salt output end of the high-temperature medium heat exchange flue, the switching valve has an input end and first and second output ends, the input end of the switching valve is in communication with the molten salt output end of the high-temperature medium heat exchange flue, the first output end of the switching valve is in communication with the high-temperature molten salt tank, and the second output end of the switching valve is in communication with the low-temperature molten salt tank.

[0012] In the embodiment of the present application, a high-temperature molten salt pump is arranged between the molten salt tank and the heat exchange structure, and a low-temperature molten salt pump is arranged between the molten salt tank and the molten salt input end of the high-temperature medium heat exchange flue.

[0013] In the embodiment of the present application, the high-temperature medium heat exchange flue comprises a flue body, a lower header, an upper header and a plurality of heat exchange pipes, the flue body is communicated with the vaporization cooling flue, the heat exchange pipes are arranged in a spiral shape in the flue body, the input end of the heat exchange pipe is arranged close to the output end of the flue body and is communicated with the molten salt output end of the superheated steam generating mechanism through the lower header, and the output end of the heat exchange pipe is arranged close to the input end of the flue body and is communicated with the molten salt input end of the superheated steam generating mechanism through the upper header.

[0014] In the embodiment of the present application, the input end of the plurality of heat exchange pipes is communicated with the lower header through a plurality of input branch pipes arranged on the flue body, and the output end of the plurality of heat exchange pipes is communicated with the upper header through a plurality of output branch pipes arranged on the flue body.

[0015] In the embodiment of the present application, the high-temperature medium heat exchange flue further comprises a cooling base arranged on the flue body and close to the output end of the flue body, and a cavity for water flow cooling is arranged in the cooling base.

[0016] In the embodiment of the present application, the steam generating mechanism comprises a deaerator, a steam drum and a regenerator, a plurality of output ends and a plurality of input ends of the steam drum are communicated with a plurality of positions of the vaporization cooling flue to form a plurality of first heat exchange circuits, the steam drum and / or the regenerator are communicated with the heat exchange structure, one output end and one input end of the deaerator are communicated with the vaporization cooling flue to form a third heat exchange circuit, and another output end of the deaerator is communicated with the steam drum.

[0017] The present application provides a method for producing superheated steam by recycling waste heat, comprising the following steps: heat storage: flue gas is sequentially delivered to a vaporization cooling flue and a high-temperature medium heat exchange flue, water exchanges heat with flue gas in the vaporization cooling flue through a first heat exchange circuit to generate steam, and low-temperature molten salt exchanges heat with flue gas in the high-temperature medium heat exchange flue through a second heat exchange circuit to generate high-temperature molten salt; heat release: the steam is delivered to a heat exchange structure and exchanges heat with the high-temperature molten salt in the second heat exchange circuit to generate superheated steam, and the high-temperature molten salt is cooled to form the low-temperature molten salt.

[0018] In the embodiment of the present application, the heat storage step is performed during a smelting period, the heat release step is performed during a non-smelting period, and the method further comprises the following steps: during the smelting period, the high-temperature molten salt is delivered to a high-temperature molten salt tank; and during the non-smelting period, the high-temperature medium heat exchange flue is communicated with a low-temperature molten salt tank to form a low-temperature molten salt circulation loop, and the low-temperature molten salt is delivered to the low-temperature molten salt circulation loop for circulation.

[0019] In the embodiment of the present application, the heat storage step is performed when no superheated steam demand of a steam user is received, and the heat release step is performed when the superheated steam demand of the steam user is received, and the method further comprises the following steps: in the heat storage step, low-temperature molten salt is transported from a molten salt tank to the high-temperature medium heat exchange flue to exchange heat with flue gas to generate high-temperature molten salt which is returned to the molten salt tank; in the heat release step, high-temperature molten salt is transported from the molten salt tank to the heat exchange structure to be cooled to form low-temperature molten salt which is returned to the molten salt tank.

[0020] The present application has the following characteristics and advantages:

[0021] The system for producing superheated steam by recycling waste heat according to the present application first makes flue gas enter a vaporization and cooling flue to exchange heat with water through a first heat exchange loop, so that the water absorbs heat to generate steam, and then makes the cooled flue gas enter a high-temperature medium heat exchange flue to exchange heat with low-temperature molten salt through a second heat exchange loop, so that the low-temperature molten salt absorbs heat to generate high-temperature molten salt, and then makes the steam and the high-temperature molten salt exchange heat through the heat exchange structure of the second heat exchange loop, so that the high-temperature molten salt is cooled to low-temperature molten salt which can exchange heat with flue gas in the next cycle, and the steam is further heated to generate high-quality superheated steam, thereby improving the waste heat recovery rate of flue gas.

[0022] The method for producing superheated steam by recycling waste heat according to the present application first makes a large amount of high-temperature flue gas generated during smelting exchange heat with water, and then exchange heat with low-temperature molten salt, so that the water absorbs heat to generate steam and the low-temperature molten salt absorbs heat to generate high-temperature molten salt, and then makes the high-temperature molten salt exchange heat with steam during non-smelting period, so that the steam is further heated to generate high-quality superheated steam, and the high-temperature molten salt is cooled to low-temperature molten salt which can exchange heat with flue gas in the next smelting period.

[0023] The method for producing superheated steam by recycling waste heat according to the present application first makes a large amount of high-temperature flue gas generated during smelting exchange heat with water, and then exchange heat with low-temperature molten salt, so that the water absorbs heat to generate steam and the low-temperature molten salt absorbs heat to generate high-temperature molten salt, and then makes the high-temperature molten salt exchange heat with steam during non-smelting period, so that the steam is further heated to generate high-quality superheated steam, and the high-temperature molten salt is cooled to low-temperature molten salt which can exchange heat with flue gas in the next smelting period. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort based on these drawings.

[0025] Figure 1 The figure is a structural schematic diagram of the system for producing superheated steam by recycling waste heat according to an embodiment of the present application.

[0026] Figure 2 The use state diagram of the system for recovering waste heat to produce superheated steam in a smelting period according to an embodiment of the present application.

[0027] Figure 3 The use state diagram of the system for recovering waste heat to produce superheated steam in a non-smelting period according to an embodiment of the present application.

[0028] Figure 4 The use state diagram of the system for recovering waste heat to produce superheated steam in a smelting period according to another embodiment of the present application.

[0029] Figure 5 The use state diagram of the system for recovering waste heat to produce superheated steam in a non-smelting period according to the present application.

[0030] Figure 6 The internal structure diagram of the high-temperature medium heat exchange flue according to the present application.

[0031] Figure 7 The cross-sectional diagram at A-A in the figure. Figure 6

[0032] The figure:

[0033] 11, vaporization cooling flue; 111, movable smoke hood; 112, furnace mouth section; 113, moving section; 114, inclined section; 115, elbow flue; 12, high-temperature medium heat exchange flue; 121, flue main body; 122, lower header; 123, upper header; 124, heat exchange pipe; 125, input branch pipe; 126, output branch pipe; 127, cooling base;

[0034] 2, steam generating mechanism; 21, deaerator; 22, steam drum; 23, accumulator; 24, first water pump; 25, second water pump;

[0035] 3, superheated steam generating mechanism; 31, heat exchange structure; 32, high-temperature molten salt tank; 33, low-temperature molten salt tank; 34, switching valve; 35, high-temperature molten salt pump; 36, low-temperature molten salt pump; 37, molten salt tank;

[0036] 4, plant steam pipe network. DETAILED DESCRIPTION

[0037] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0038] ​Embodiment one

[0039] As shown in Figure 1 , Figure 2 and Figure 3 , the present application provides a system for producing superheated steam by recycling waste heat, comprising: a flue structure comprising a vaporization cooling flue 11 and a high-temperature medium heat exchange flue 12 which are communicated along the conveying direction of flue gas; a steam generation mechanism 2 which is communicated with the vaporization cooling flue 11 and is formed with at least one first heat exchange loop; a superheated steam generation mechanism 3 comprising a heat exchange structure 31 which is communicated with the high-temperature medium heat exchange flue 12 and is formed with at least one second heat exchange loop, and the heat exchange structure 31 is further communicated with the steam output end of the steam generation mechanism 2; wherein water can be heated by the first heat exchange loop to produce steam by exchanging heat with the flue gas in the vaporization cooling flue 11, low-temperature molten salt can be heated by the second heat exchange loop to produce high-temperature molten salt by exchanging heat with the flue gas in the high-temperature medium heat exchange flue 12, and steam can be heated by the heat exchange structure 31 to produce superheated steam by exchanging heat with the high-temperature molten salt in the second heat exchange loop, and the high-temperature molten salt is cooled to form low-temperature molten salt.

[0040] The system for producing superheated steam by recycling waste heat of the present application, flue gas first enters the vaporization cooling flue 11 to exchange heat with water by the first heat exchange loop, so that the water absorbs heat to generate steam, and the cooled flue gas then enters the high-temperature medium heat exchange flue 12 to exchange heat with low-temperature molten salt by the second heat exchange loop, so that the low-temperature molten salt absorbs heat to generate high-temperature molten salt, and then the heat exchange structure 31 on the second heat exchange loop exchanges heat between the steam and the high-temperature molten salt, so that the high-temperature molten salt is cooled to low-temperature molten salt which can exchange heat with flue gas in the next cycle, and the steam is further heated to generate high-quality superheated steam, thereby improving the waste heat recovery rate of flue gas.

[0041] The system for producing superheated steam by recycling waste heat of the present application is suitable for application in the technical field of converter steelmaking, and the superheated steam output by the heat exchange structure 31 can be sent to steam users (such as a steelmaking refining system, an RH furnace vacuum pumping system, or a waste heat power generation system) by a plant steam pipe network 4, thereby improving the energy recycling efficiency, reducing the energy consumption level in the steel converter steelmaking production process, and reducing production costs.

[0042] As shown in Figure 2 and Figure 3As shown, in some embodiments of the present application, the system for recovering waste heat to produce superheated steam carries out waste heat recovery of flue gas, including the following steps: during smelting period, flue gas is sequentially sent to vaporization cooling flue 11 and high-temperature medium heat exchange flue 12, water exchanges heat with flue gas in vaporization cooling flue 11 through the first heat exchange loop to produce steam, and low-temperature molten salt exchanges heat with flue gas in high-temperature medium heat exchange flue 12 through the second heat exchange loop to produce high-temperature molten salt; during non-smelting period, steam is sent to heat exchange structure 31 and exchanges heat with high-temperature molten salt in the second heat exchange loop to produce superheated steam, and high-temperature molten salt is cooled to form low-temperature molten salt.

[0043] Wherein, the production cycle of one furnace of steel is about 40 minutes; the smelting period is the stage of blowing oxygen in the converter, about 15 minutes, and oxygen blown out by the oxygen lance will react with carbon and other elements in the molten iron in the converter to generate a large amount of mixed high-temperature flue gas mainly containing carbon monoxide, and the flue gas temperature at the outlet of the converter can be as high as 1600℃; the non-smelting period is the stage of not blowing oxygen in the converter, about 25 minutes.

[0044] For example, Figure 4 and Figure 5As shown, in some other embodiments of the present application, the system for producing superheated steam by recovering waste heat from flue gas recovers waste heat from flue gas, including the following steps: when no superheated steam demand from steam users is received, the flue gas is sequentially sent to the vaporization cooling flue 11 and the high-temperature medium heat exchange flue 12, water exchanges heat with the flue gas in the vaporization cooling flue 11 through the first heat exchange circuit to generate steam, and low-temperature molten salt exchanges heat with the flue gas in the high-temperature medium heat exchange flue 12 through the second heat exchange circuit to generate high-temperature molten salt; when the superheated steam demand from steam users is received, the steam is sent to the heat exchange structure 31 and exchanges heat with the high-temperature molten salt in the second heat exchange circuit to generate superheated steam, and the high-temperature molten salt is cooled to form low-temperature molten salt. Specifically, the molten salt includes but is not limited to binary solar salt (components are 40% KNO3 and 60% NaNO3), which can be heated in a molten state (for example, from low-temperature molten salt at 280℃ to high-temperature molten salt at 560℃). The first heat exchange circuit includes the steam generation mechanism 2, the vaporization cooling flue 11, and the communication structure between the steam generation mechanism 2 and the vaporization cooling flue 11. The heat exchange structure 31 has a high-temperature molten salt input end, a low-temperature molten salt output end, a steam input end, and a superheated steam output end, and the high-temperature molten salt input end and the low-temperature molten salt output end are in communication with the high-temperature medium heat exchange flue 12, and the steam input end is in communication with the steam generation mechanism 2. The heat exchange structure 31 is provided with a molten salt heat exchange channel and a steam heat exchange channel, and the second heat exchange circuit includes the molten salt heat exchange channel, the high-temperature medium heat exchange flue 12, and the communication structure between the molten salt heat exchange channel and the high-temperature medium heat exchange flue 12. The steam heat exchange channel is in communication with the steam generation mechanism 2. The two ends of the molten salt heat exchange channel are the high-temperature molten salt input end and the low-temperature molten salt output end, and the two ends of the steam heat exchange channel are the steam input end and the superheated steam output end. Among them, the heat exchange structure 31 can be a superheater. The steam generated by the steam generation mechanism 2 is low-pressure saturated steam. The high-temperature medium heat exchange flue 12 has a molten salt input end, a molten salt output end, a flue gas input end, and a flue gas output end, and the molten salt input end and the molten salt output end of the high-temperature medium heat exchange flue 12 are in communication with the superheated steam generation mechanism 3, and the flue gas input end of the high-temperature medium heat exchange flue 12 is in communication with the flue gas output end of the vaporization cooling flue 11. The flue gas cooled after heat exchange with the low-temperature molten salt is discharged from the flue gas output end of the high-temperature medium heat exchange flue 12 to the flue gas dust removal system.

[0045] As Figure 3As shown, in the embodiment of the present application, the superheated steam generating mechanism 3 is in communication with the high-temperature medium heat exchange flue 12 and further forms a low-temperature molten salt circulation loop. The low-temperature molten salt cooled in the second heat exchange loop can enter the low-temperature molten salt circulation loop for circulation. By setting the low-temperature molten salt circulation loop to circulate the cooled low-temperature molten salt, not only can the second heat exchange loop be prevented from being blocked due to the solidification of the low-temperature molten salt caused by cooling, but also the low-temperature molten salt can be further cooled by circulation during the non-smelting period, thereby facilitating the improvement of the heat exchange efficiency between the low-temperature molten salt and the flue gas during the smelting period, and thus improving the waste heat recovery rate. Specifically, the molten salt output end of the high-temperature medium heat exchange flue 12 is in communication with a switching valve 34. The low-temperature molten salt output from the high-temperature medium heat exchange flue 12 during the non-smelting period is controlled by the switching valve 34 to not enter the heat exchange structure 31 but circulate in the low-temperature molten salt circulation loop.

[0046] In the embodiment of the present application, the superheated steam generating mechanism 3 further comprises at least one molten salt tank. The at least one molten salt tank is in communication with the molten salt output end of the high-temperature medium heat exchange flue 12 and the molten salt input end thereof, and is further in communication with the high-temperature molten salt input end of the heat exchange structure 31 and the low-temperature molten salt output end thereof. Specifically, a high-temperature molten salt pump 35 is arranged between the molten salt tank and the heat exchange structure 31, and a low-temperature molten salt pump 36 is arranged between the molten salt tank and the molten salt input end of the high-temperature medium heat exchange flue 12.

[0047] As shown in FIG. 1, the superheated steam generating mechanism 3 comprises a heat exchange structure 31 and a high-temperature medium heat exchange flue 12. The heat exchange structure 31 is in communication with the high-temperature medium heat exchange flue 12. The heat exchange structure 31 comprises a high-temperature molten salt input end and a low-temperature molten salt output end. The high-temperature medium heat exchange flue 12 is in communication with the high-temperature molten salt input end of the heat exchange structure 31 and the low-temperature molten salt output end thereof. The high-temperature medium heat exchange flue 12 is in communication with a flue gas inlet end and a flue gas outlet end. The flue gas inlet end of the high-temperature medium heat exchange flue 12 is in communication with a flue gas inlet pipe 13, and the flue gas outlet end of the high-temperature medium heat exchange flue 12 is in communication with a flue gas outlet pipe 14. Figure 2 and Figure 3 As shown in FIG. 1, the superheated steam generating mechanism 3 further comprises a low-temperature molten salt tank 33 and a high-temperature molten salt tank 32. The high-temperature molten salt input end is in communication with the high-temperature medium heat exchange flue 12 through the high-temperature molten salt tank 32, and the low-temperature molten salt output end is in communication with the high-temperature medium heat exchange flue 12 through the low-temperature molten salt tank 33.

[0048] During the smelting period, the switching valve 34 is controlled to be in a communication state between the high-temperature molten salt tank 32 and the molten salt output end of the high-temperature medium heat exchange flue 12, and in a disconnected state between the low-temperature molten salt tank 33 and the molten salt output end of the high-temperature medium heat exchange flue 12. The low-temperature molten salt is transported from the low-temperature molten salt tank 33 to the high-temperature medium heat exchange flue 12 to exchange heat with the flue gas, so that the flue gas is cooled, and the low-temperature molten salt is heated to form high-temperature molten salt, which is then transported to the high-temperature molten salt tank 32.

[0049] In the non-smelting period, the switching valve 34 is controlled to be in the disconnected state between the high-temperature molten salt tank 32 and the molten salt output end of the high-temperature medium heat exchange flue 12, and in the connected state between the low-temperature molten salt tank 33 and the molten salt output end of the high-temperature medium heat exchange flue 12. The steam in the steam generating mechanism 2 is transported into the heat exchange structure 31, and at the same time, the high-temperature molten salt in the high-temperature molten salt tank 32 is transported from the high-temperature molten salt input end into the heat exchange structure 31 to exchange heat with the steam, so that the steam absorbs heat to generate superheated steam, and the high-temperature molten salt is cooled to form low-temperature molten salt. The low-temperature molten salt after cooling enters the low-temperature molten salt tank 33, and then circulates in the low-temperature molten salt circulation loop.

[0050] Specifically, the low-temperature molten salt circulation loop includes the low-temperature molten salt tank 33, the high-temperature medium heat exchange flue 12, and the switching valve 34. The second heat exchange loop includes the low-temperature molten salt tank 33, the high-temperature medium heat exchange flue 12, the switching valve 34, the high-temperature molten salt tank 32, and the molten salt heat exchange channel. The switching valve 34 is arranged on the communication pipeline between the high-temperature molten salt tank 32 and the molten salt output end of the high-temperature medium heat exchange flue 12. The switching valve 34 has an input end and first and second output ends. The input end of the switching valve 34 communicates with the high-temperature medium heat exchange flue 12. The first output end of the switching valve 34 communicates with the high-temperature molten salt tank 32. The second output end of the switching valve 34 communicates with the low-temperature molten salt tank 33. The high-temperature molten salt tank 32 and the low-temperature molten salt tank 33 are both atmospheric storage tank structures. As shown in Figure 2 and Figure 3 The high-temperature molten salt tank 32 and the heat exchange structure 31 are provided with a high-temperature molten salt pump 35, and the low-temperature molten salt tank 33 and the molten salt input end of the high-temperature medium heat exchange flue 12 are provided with a low-temperature molten salt pump 36. The low-temperature molten salt pump 36 operates at variable frequency. In the smelting period, the low-temperature molten salt pump 36 operates at full load, so that the low-temperature molten salt can be pressurized by the low-temperature molten salt pump 36, enter the high-temperature medium heat exchange flue 12 from the low-temperature molten salt tank 33 to exchange heat, and after being cooled to low-temperature molten salt, enter the high-temperature molten salt tank 32 through the switching valve 34 for storage. In the non-smelting period, the low-temperature molten salt pump 36 operates at low load, and the molten salt is pressurized after flowing through the high-temperature medium heat exchange flue 12 from the low-temperature molten salt tank 33, and then flows back to the low-temperature molten salt tank 33 through the switching valve 34. At the same time, in the non-smelting period, the high-temperature molten salt in the high-temperature molten salt tank 32 is pressurized by the high-temperature molten salt pump 35 and enters the heat exchange structure 31 to heat the low-pressure saturated steam to form superheated steam. The molten salt is cooled to low-temperature molten salt and enters the low-temperature molten salt tank 33.

[0051] Optionally, the relative height of the low-temperature molten salt tank 33 and the high-temperature medium heat exchange flue 12 is arranged to enable the molten salt to provide transport power by using its own gravity. Optionally, the relative height of the high-temperature molten salt tank 32 and the heat exchange structure 31 is arranged to enable the molten salt to provide transport power by using its own gravity.

[0052] As shown in Figure 4 and Figure 5 In some embodiments of the present application, the number of molten salt tanks 37 is one. When no superheated steam demand from steam users is received, low-temperature molten salt is transported from the molten salt tank 37 to the high-temperature medium heat exchange flue 12 to exchange heat with flue gas to generate high-temperature molten salt, which is returned to the molten salt tank 37; when superheated steam demand from steam users is received, high-temperature molten salt is transported from the molten salt tank 37 to the heat exchange structure 31 to be cooled to form low-temperature molten salt, which is returned to the molten salt tank 37. Specifically, the molten salt tank 37 is in communication with the molten salt input end and the molten salt output end of the high-temperature medium heat exchange flue 12 to form a circulation loop. In the heat storage stage, the molten salt can be circulated in the circulation loop to continuously store heat, while in the heat release stage, the circulation loop can serve as a low-temperature molten salt circulation loop to avoid the molten salt from solidifying due to cooling.

[0053] As shown in Figure 6 and Figure 7 In some embodiments of the present application, the high-temperature medium heat exchange flue 12 includes a flue body 121, a lower header 122, an upper header 123, and a plurality of heat exchange pipes 124. The flue body 121 is in communication with the vaporization and cooling flue 11. The heat exchange pipes 124 are arranged in a spiral shape in the flue body 121. The input end of the heat exchange pipe 124 is arranged close to the output end of the flue body 121 and is in communication with the molten salt output end of the superheated steam generating mechanism 3 through the lower header 122. The output end of the heat exchange pipe 124 is arranged close to the input end of the flue body 121 and is in communication with the molten salt input end of the superheated steam generating mechanism 3 through the upper header 123. The low-temperature molten salt first enters the lower header 122 and is then distributed and transported to the plurality of heat exchange pipes 124 to exchange heat with the flue gas in the flue body 121. In combination with Figure 2 and Figure 3 In some embodiments of the present application, the lower header 122 is in communication with the molten salt output end of the low-temperature molten salt tank 33 of the superheated steam generating mechanism 3, and the upper header 123 is in communication with the molten salt input end of the high-temperature molten salt tank 32 of the superheated steam generating mechanism 3. In combination with Figure 4 and Figure 5 In some embodiments of the present application, the lower header 122 and the upper header 123 are in communication with the same molten salt tank 37.

[0054] The flue gas is transported in the flue main body 121 from the input end of the flue main body 121 to the output end of the flue main body 121, and the temperature gradually decreases; the flue gas is transported in the heat exchange pipe 124 from the input end of the heat exchange pipe 124 to the output end of the heat exchange pipe 124, and the temperature gradually increases; by setting the input end of the heat exchange pipe 124 close to the output end of the flue main body 121 and setting the output end of the heat exchange pipe 124 close to the input end of the flue main body 121, the molten salt in the heat exchange pipe 124 and the flue gas nearby always have a certain temperature difference, thereby facilitating the improvement of the heat exchange efficiency between the molten salt and the flue gas.

[0055] Specifically, the flue main body 121 is generally in a tubular structure. The heat exchange pipe 124 is generally in a threaded tubular structure, spirals from the position close to the output end of the flue main body 121 to the position close to the input end of the flue main body 121. The plurality of heat exchange pipes 124 are densely arranged on the inner wall surface of the flue main body 121, so that the low-temperature molten salt in the heat exchange pipe 124 and the flue gas in the flue main body 121 fully exchange heat, thereby facilitating the improvement of the waste heat recovery rate of the flue gas. The wall body of the flue main body 121 is filled with heat insulation material to avoid heat transfer to the outside, thereby improving the waste heat recovery rate. The input ends of the plurality of heat exchange pipes 124 are connected with the lower header 122 through the plurality of input branch pipes 125 penetrating the flue main body 121; the output ends of the plurality of heat exchange pipes 124 are connected with the upper header 123 through the plurality of output branch pipes 126 penetrating the flue main body 121.

[0056] The high-temperature medium heat exchange flue 12 further comprises a cooling base 127, which is arranged on the flue main body 121 and close to the input end of the flue main body 121, and the cooling base 127 is provided with a cavity for water flow cooling. By arranging the cooling base 127, the temperature of the molten salt transported to the heat exchange pipe 124 can be further reduced, and the cooling effect on the flue gas can be improved.

[0057] In the embodiment of the application, the steam generating mechanism 2 comprises a deaerator 21, a steam drum 22 and a regenerator 23, the plurality of output ends and the plurality of input ends of the steam drum 22 are connected with the plurality of positions of the vaporization and cooling flue 11 to form a plurality of first heat exchange circuits, and the steam drum 22 and / or the regenerator 23 are connected with the heat exchange structure 31; one output end and one input end of the deaerator 21 are connected with the vaporization and cooling flue 11 to form a third heat exchange circuit, and the other output end of the deaerator 21 is connected with the steam drum 22.

[0058] Specifically, the vaporization cooling flue 11 includes, in sequence along the conveying direction of the flue gas, a furnace mouth section 112, a moving section 113, an inclined section 114, a bent flue 115, and a movable smoke hood 111 arranged near the inlet of the furnace mouth section 112; the vaporization cooling flue 11 has a more specific structure same as the prior art, which is not described here. The output end and the input end of the steam drum 22 are communicated with the furnace mouth section 112 to form a first heat exchange loop, the output end and the input end of the steam drum 22 are communicated with the moving section 113 to form a first heat exchange loop, the output end and the input end of the steam drum 22 are communicated with the inclined section 114 to form a first heat exchange loop, and the output end and the input end of the steam drum 22 are communicated with the bent flue 115 to form a first heat exchange loop. The flue main body 121 of the high-temperature medium heat exchange flue 12 is connected with the output end of the bent flue 115 in a substantially bent pipe structure. The output end and the input end of the deaerator 21 are communicated with the movable smoke hood 111 to form a third heat exchange loop. The steam drum 22 pumps the water pressurized by the first water pump 24 to the furnace mouth section 112, the moving section 113, the inclined section 114, and the bent flue 115 of the vaporization cooling flue 11 for heat exchange; the deaerator 21 pumps the water pressurized by the second water pump 25 to the movable smoke hood 111 for heat exchange.

[0059] In the third heat exchange loop, the working medium water is heated in the movable smoke hood 111 and then evaporated in the water tank of the deaerator 21 to heat the water in the water tank, so as to achieve the purpose of further deoxygenation. The water in the water tank is delivered to the steam drum 22, the boiler water in the steam drum 22 is heated in the furnace mouth section 112, the moving section 113, the inclined section 114, and the bent flue 115 of the vaporization cooling flue 11 and then returns to the steam drum 22, in which steam is generated after steam-water separation, and the continuous and stable low-pressure saturated steam is generated after the accumulator 23. At the same time, the flue gas is sequentially heated and cooled to about 1000℃ by the movable smoke hood 111, the furnace mouth section 112, the moving section 113, the inclined section 114, and the bent flue 115 of the vaporization cooling flue 11, and then enters the high-temperature medium heat exchange flue 12 to be further cooled by the low-temperature molten salt.

[0060] Embodiment two

[0061] Combination Figures 2 to 5As shown, the present application provides a method for producing superheated steam by recovering waste heat, which can be implemented by the system for producing superheated steam by recovering waste heat in the first embodiment, and includes the following steps: heat storage: the flue gas is sequentially delivered to the vaporization and cooling flue 11 and the high-temperature medium heat exchange flue 12, and the water exchanges heat with the flue gas in the vaporization and cooling flue 11 through the first heat exchange loop to generate steam, while the low-temperature molten salt exchanges heat with the flue gas in the high-temperature medium heat exchange flue 12 through the second heat exchange loop to generate high-temperature molten salt; heat release: the steam is delivered to the heat exchange structure 31 and exchanges heat with the high-temperature molten salt in the second heat exchange loop to generate superheated steam, and the high-temperature molten salt is cooled to form low-temperature molten salt. In combination Figure 2 and Figure 3 As shown, in some embodiments of the present application, the heat storage step is performed during the smelting period, and the heat release step is performed during the non-smelting period. The method for producing superheated steam by recovering waste heat of the present application, during the smelting period, a large amount of high-temperature flue gas is first exchanged heat with water, and then exchanged heat with low-temperature molten salt, so that the water absorbs heat to generate steam and the low-temperature molten salt absorbs heat to generate high-temperature molten salt, and then during the non-smelting period, the high-temperature molten salt exchanges heat with the steam, so that the steam further absorbs heat to generate high-quality superheated steam, and the high-temperature molten salt is also cooled to form low-temperature molten salt for exchanging heat with the flue gas in the next smelting period. Specifically, the method further includes the following steps: during the smelting period, the high-temperature molten salt is delivered to the high-temperature molten salt tank 32; during the non-smelting period, the high-temperature medium heat exchange flue 12 is communicated with the low-temperature molten salt tank 33 to form a low-temperature molten salt circulation loop, and the low-temperature molten salt is delivered to the low-temperature molten salt circulation loop for circulation.

[0062] In combination Figure 4 and Figure 5 As shown, in some embodiments of the present application, the heat storage step is performed during the smelting period, and the heat release step is performed during the non-smelting period. The method for producing superheated steam by recovering waste heat of the present application, during the smelting period, a large amount of high-temperature flue gas is first exchanged heat with water, and then exchanged heat with low-temperature molten salt, so that the water absorbs heat to generate steam and the low-temperature molten salt absorbs heat to generate high-temperature molten salt, and then during the non-smelting period, the high-temperature molten salt exchanges heat with the steam, so that the steam further absorbs heat to generate high-quality superheated steam, and the high-temperature molten salt is also cooled to form low-temperature molten salt for exchanging heat with the flue gas in the next smelting period. Specifically, the method further includes the following steps: during the smelting period, the high-temperature molten salt is delivered to the high-temperature molten salt tank 32; during the non-smelting period, the high-temperature medium heat exchange flue 12 is communicated with the low-temperature molten salt tank 33 to form a low-temperature molten salt circulation loop, and the low-temperature molten salt is delivered to the low-temperature molten salt circulation loop for circulation.

[0063] Specifically, the method further includes the following steps: in the heat storage step, the low-temperature molten salt is delivered from the molten salt tank 37 to the high-temperature medium heat exchange flue 12, and the high-temperature molten salt generated by exchanging heat with the flue gas is returned to the molten salt tank 37; in the heat release step, the high-temperature molten salt is delivered from the molten salt tank 37 to the heat exchange structure 31, and the low-temperature molten salt formed by cooling is returned to the molten salt tank 37.

[0064] The above merely describes several embodiments of the present application, and those skilled in the art can make various modifications or variations to the embodiments of the present application according to the content disclosed in the application file without departing from the spirit and scope of the present application.

Claims

1. A system for recovering waste heat to produce superheated steam, characterized in that, include: The flue structure includes a vaporization cooling flue and a high-temperature medium heat exchange flue that are connected along the flue gas conveying direction; A steam generating mechanism is connected to the vaporization cooling flue and forms at least one first heat exchange circuit; A superheated steam generating mechanism includes a heat exchange structure, which is connected to the high-temperature medium heat exchange flue and forms at least one second heat exchange circuit. The heat exchange structure is also connected to the steam output end of the steam generating mechanism. In this process, water can exchange heat with the flue gas in the vaporization cooling flue through the first heat exchange circuit to generate steam, low-temperature molten salt can exchange heat with the flue gas in the high-temperature medium heat exchange flue through the second heat exchange circuit to generate high-temperature molten salt, the steam can exchange heat with the high-temperature molten salt in the second heat exchange circuit through the heat exchange structure to generate superheated steam, and the high-temperature molten salt cools down to form the low-temperature molten salt. The superheated steam generating mechanism is connected to the high-temperature medium heat exchange flue and also forms a low-temperature molten salt circulation loop. The low-temperature molten salt that has been cooled down by heat exchange in the second heat exchange loop can enter the low-temperature molten salt circulation loop for circulation. The heat exchange structure has a high-temperature molten salt input end, a low-temperature molten salt output end, a steam input end, and a superheated steam output end. The high-temperature molten salt input end of the heat exchange structure is connected to the molten salt output end of the high-temperature medium heat exchange flue. The low-temperature molten salt output end of the heat exchange structure is connected to the molten salt input end of the high-temperature medium heat exchange flue. The steam input end is connected to the steam output end of the steam generating mechanism. The high-temperature medium heat exchange flue includes a flue body, a lower header, an upper header, and multiple heat exchange tubes. The flue body is connected to the vaporization cooling flue. The heat exchange tubes are arranged in a spiral shape inside the flue body. The input end of the heat exchange tube is located near the output end of the flue body and is connected to the molten salt output end of the superheated steam generating mechanism through the lower header. The output end of the heat exchange tube is located near the input end of the flue body and is connected to the molten salt input end of the superheated steam generating mechanism through the upper header. The steam generating mechanism includes a deaerator, a steam drum, and a heat accumulator. Multiple output and input terminals of the steam drum are connected to multiple locations of the vaporization cooling flue to form multiple first heat exchange circuits. The steam drum and / or the heat accumulator are connected to the heat exchange structure. One output and one input terminal of the deaerator are connected to the vaporization cooling flue to form a third heat exchange circuit. The other output terminal of the deaerator is connected to the steam drum.

2. The system for recovering waste heat to produce superheated steam according to claim 1, characterized in that, The superheated steam generating mechanism further includes at least one molten salt tank, which is connected to the molten salt output end and the molten salt input end of the high-temperature medium heat exchange flue, and is also connected to the high-temperature molten salt input end and the low-temperature molten salt output end of the heat exchange structure.

3. The system for recovering waste heat to produce superheated steam according to claim 2, characterized in that, The number of molten salt tanks is multiple, including low-temperature molten salt tanks and high-temperature molten salt tanks. The high-temperature molten salt input end of the heat exchange structure is connected to the molten salt output end of the high-temperature medium heat exchange flue through the high-temperature molten salt tank, and the low-temperature molten salt output end of the heat exchange structure is connected to the molten salt input end of the high-temperature medium heat exchange flue through the low-temperature molten salt tank.

4. The system for recovering waste heat to produce superheated steam according to claim 3, characterized in that, A switching valve is provided between the high-temperature molten salt tank and the molten salt output end of the high-temperature medium heat exchange flue. The switching valve has an input end, a first output end, and a second output end. The input end of the switching valve is connected to the molten salt output end of the high-temperature medium heat exchange flue, the first output end of the switching valve is connected to the high-temperature molten salt tank, and the second output end of the switching valve is connected to the low-temperature molten salt tank.

5. The system for recovering waste heat to produce superheated steam according to claim 1, characterized in that, The input ends of the multiple heat exchange tubes are connected to the lower header through multiple input branch pipes passing through the main body of the flue; the output ends of the multiple heat exchange tubes are connected to the upper header through multiple output branch pipes passing through the main body of the flue.

6. The system for recovering waste heat to produce superheated steam according to claim 5, characterized in that, The high-temperature medium heat exchange flue also includes a cooling base, which is disposed on the flue body and located near the output end of the flue body. The cooling base has a cavity for water flow cooling.

7. A method for recovering waste heat to produce superheated steam, characterized in that, The system for producing superheated steam by recovering waste heat according to any one of claims 1-6, the method comprising the following steps: Heat storage: Flue gas is sequentially transported to vaporization cooling flue and high-temperature medium heat exchange flue. Water exchanges heat with the flue gas in the vaporization cooling flue through the first heat exchange circuit to generate steam. At the same time, low-temperature molten salt exchanges heat with the flue gas in the high-temperature medium heat exchange flue through the second heat exchange circuit to generate high-temperature molten salt. Heat release: The steam is transported to the heat exchange structure and exchanges heat with the high-temperature molten salt in the second heat exchange circuit to generate superheated steam, and the high-temperature molten salt cools down to form the low-temperature molten salt.

8. The method for recovering waste heat to produce superheated steam according to claim 7, characterized in that, The heat storage step is carried out during the smelting period, and the heat release step is carried out during the non-smelting period. The method further includes the following steps: During the smelting period, the high-temperature molten salt is transported to a high-temperature molten salt tank; During the non-smelting period, the high-temperature medium heat exchange flue is connected to the low-temperature molten salt tank to form a low-temperature molten salt circulation loop, and the low-temperature molten salt is transported to the low-temperature molten salt circulation loop for circulation.

9. The method for recovering waste heat to produce superheated steam according to claim 7, characterized in that, The heat storage step is performed when no superheated steam demand from the steam user is received, and the heat release step is performed when a superheated steam demand from the steam user is received. The method further includes the following steps: In the heat storage step, the low-temperature molten salt is transported from the molten salt tank to the high-temperature medium heat exchange flue, and the high-temperature molten salt generated by heat exchange with the flue gas is returned to the molten salt tank. In the heat release step, the high-temperature molten salt is transported from the molten salt tank to the heat exchange structure, and the low-temperature molten salt formed by cooling is returned to the molten salt tank.

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