High-temperature high-dust-content flue gas waste heat recovery system

Abstract

The invention provides a high-temperature high-dust-content flue gas waste heat recovery system which comprises a steam superheater, a fused salt heat exchanger, a water medium pipeline and a fused salt pipeline, a flue gas outlet of the steam superheater is connected with a flue gas inlet of the fused salt heat exchanger, and high-temperature high-dust-content flue gas can sequentially flow through the steam superheater and the fused salt heat exchanger. A second heat exchange pipe is arranged in the fused salt heat exchanger and is sequentially connected with a fused salt pipeline end to end to form a fused salt circulating pipeline; a first heat exchange pipe is arranged in the steam superheater, an inlet of the first heat exchange pipe is connected with a water medium pipeline, at least one heat exchange device is arranged in the water medium pipeline, a heat exchange pipe is arranged in the heat exchange device, and the fused salt pipeline is communicated with the heat exchange pipe; according to the flue gas waste heat recovery system, in the whole waste heat recovery process of the high-temperature and high-dust-content flue gas, water vapor carried by the flue gas cannot be condensed, the situation that dust in the high-dust-content flue gas is combined with condensate water to form sludge is avoided, and the problems of sludge attachment and blockage in the system are avoided.

Description

Technical Field

[0001] The invention relates to the technical field of waste heat recovery, and in particular to a high-temperature and high-dust flue gas waste heat recovery system. Background Art

[0002] At present, the country advocates vigorously developing waste heat utilization, energy conservation and emission reduction, which plays a positive role in protecting energy and improving the quality of human living environment. For industrial production activities, the high-temperature flue gas produced often carries a large amount of heat, which needs to be recovered from the waste heat. Various flue gas waste heat recovery systems are also disclosed in the prior art.

[0003] However, for high-temperature and high-dust flue gas, the existing flue gas waste heat recovery system often has poor operating stability when performing heat exchange treatment on it. As the temperature of the high-temperature and high-dust flue gas decreases during the heat exchange process, condensed water will inevitably be generated, which will cause the dust in the high-dust flue gas to combine with the condensed water to form sludge, which is extremely easy to adhere to the inside of the flue gas waste heat recovery system, such as the heat exchange pipe wall, the inner wall of the heat exchange equipment, etc. Over time, it is easy to cause blockage of the flue gas waste heat recovery system and affect its normal operation. Summary of the invention

[0004] In view of this, the present invention aims to propose a high-temperature and high-dust flue gas waste heat recovery system to solve the problems of sludge adhesion and blockage easily occurring inside the system during the waste heat recovery process of high-temperature and high-dust flue gas in the prior art.

[0005] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0006] A high-temperature and high-dust flue gas waste heat recovery system comprises a steam superheater, a molten salt heat exchanger, a water medium pipeline, and a molten salt pipeline. The flue gas outlet of the steam superheater is connected to the flue gas inlet of the molten salt heat exchanger, and the high-temperature and high-dust flue gas can flow through the steam superheater and the molten salt heat exchanger in sequence. A second heat exchange tube is arranged in the molten salt heat exchanger, and the second heat exchange tube is connected to the molten salt pipeline in sequence end to end to form a molten salt circulation pipeline; a first heat exchange tube is arranged in the steam superheater, the inlet of the first heat exchange tube is connected to the water medium pipeline, and the outlet of the first heat exchange tube is connected to a downstream system, at least one heat exchange device is arranged in the water medium pipeline, a heat exchange tube is arranged in the heat exchange device, and the molten salt pipeline is connected to the heat exchange tube for heat exchange between molten salt and water medium.

[0007] Furthermore, along the flow direction of the water medium, a preheater and a steam generator are sequentially arranged in the water medium pipeline, a fourth heat exchange tube is arranged in the preheater, a third heat exchange tube is arranged in the steam generator, and the molten salt inlet and the molten salt outlet of the third heat exchange tube and the molten salt inlet of the fourth heat exchange tube are all connected to the molten salt pipeline.

[0008] Furthermore, the water medium pipeline includes a water pipe and a steam pipeline. The water inlet of the preheater is connected to the water supply device through the water pipe, the water outlet of the preheater is connected to the water inlet of the steam generator through the water pipe, the steam outlet of the steam generator is connected to the steam inlet of the steam superheater through the steam pipeline, and the steam outlet of the steam superheater is connected to the downstream power generation system.

[0009] Furthermore, the molten salt outlet of the second heat exchange tube is connected to the molten salt inlet of the third heat exchange tube through a molten salt pipeline, the molten salt outlet of the third heat exchange tube is connected to the molten salt inlet of the fourth heat exchange tube through a molten salt pipeline, and the molten salt outlet of the fourth heat exchange tube is connected to the molten salt inlet of the second heat exchange tube.

[0010] Furthermore, a molten salt storage tank is arranged in the molten salt pipeline.

[0011] Furthermore, the molten salt outlet of the fourth heat exchange tube is connected to the molten salt inlet of the molten salt storage tank, and the molten salt outlet of the molten salt storage tank is connected to the molten salt inlet of the second heat exchange tube.

[0012] Furthermore, a molten salt pump is provided in the molten salt pipeline.

[0013] Furthermore, in the flow direction of the water medium, the boiler water at room temperature enters the preheater, and after heat exchange with the molten salt, the water temperature is raised to 140℃-160℃; then the water enters the steam generator, and after heat exchange with the molten salt, 240℃-260℃ saturated steam is generated; the saturated steam enters the steam superheater, and heat exchange with the high-temperature and high-dust flue gas, the saturated steam is heated to 340-350℃, and superheated steam is formed. In the direction of flue gas flow, a flue cooler is arranged upstream of the steam superheater, and the high-temperature and high-dust flue gas is first cooled to 800℃ by the flue cooler, and the flue gas enters the steam superheater to exchange heat with the saturated steam, and then enters the molten salt heat exchanger to exchange heat with the molten salt, so that the flue gas is cooled to 200℃-260℃.

[0014] Compared with the prior art, the high-temperature and high-dust flue gas waste heat recovery system described in the present invention has the following advantages:

[0015] The high-temperature and high-dust flue gas waste heat recovery system described in the present invention performs a two-stage heat exchange process on the high-temperature and high-dust flue gas in sequence by arranging a steam superheater and a molten salt heat exchanger. In particular, a steam superheater is arranged before the molten salt heat exchanger, and water vapor is used to perform the first-stage heat exchange on the high-temperature and high-dust flue gas. Compared with the liquid-gas heat exchange technology that uses water and flue gas for heat exchange in the existing flue gas recovery system, since water vapor is a relatively high-temperature gaseous medium, during the gas-to-gas heat exchange process with the flue gas, the tube wall of the first heat exchange tube can maintain a relatively high temperature, and is higher than the dew point temperature of water vapor; similarly, in the molten salt heat exchanger, the molten salt in the prior art is used to perform the second-stage heat exchange on the flue gas, and the temperature of the molten salt in the second heat exchange tube is often higher than the dew point temperature of water vapor, so that the tube wall of the second heat exchange tube can also maintain a wall temperature higher than the dew point temperature of water vapor.

[0016] This ensures that the water vapor carried by the high-temperature and high-dust flue gas will not condense during the entire waste heat recovery process, preventing the dust in the high-dust flue gas from combining with condensed water to form sludge, avoiding the problem of sludge adhesion and blockage inside the system, and is conducive to maintaining the long-term normal operation of the waste heat recovery system. At the same time, the high-temperature and high-dust flue gas undergoes a two-stage heat exchange process. Since the heat exchange temperature difference is relatively not particularly large, the high-temperature and high-dust flue gas and the corresponding heat exchange equipment can be in a step-by-step cooling process, avoiding the stress deformation and even cracking of individual components in the equipment caused by the sudden cooling heat exchange process, which is conducive to ensuring the service life of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0018] Figure 1 This is a schematic structural diagram of a high-temperature and high-dust flue gas waste heat recovery system according to an embodiment of the present invention.

[0019] Description of reference numerals:

[0020] 1. Steam superheater; 11. First heat exchange tube; 2. Molten salt heat exchanger; 21. Second heat exchange tube; 3. Steam generator; 31. Third heat exchange tube; 4. Preheater; 41. Fourth heat exchange tube; 5. Molten salt storage tank; 6. Molten salt pump; 7. Steam pipeline; 8. Molten salt pipeline; 9. Water pipe. DETAILED DESCRIPTION

[0021] The inventive concepts of the present disclosure will be described below using terms commonly used by those skilled in the art to convey the essence of their work to other persons skilled in the art. However, these inventive concepts can be embodied in many different forms and should not be considered limited to the embodiments described herein.

[0022] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present invention can be combined with each other. The arrows in the drawings indicate the flow direction of the material.

[0023] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0024] For high-temperature and high-dust flue gas, the existing flue gas waste heat recovery system often has poor operating stability when performing heat exchange treatment on it. As the temperature of the high-temperature and high-dust flue gas decreases during the heat exchange process, condensed water will inevitably be generated, which will cause the dust in the high-dust flue gas to combine with the condensed water to form sludge, which is extremely easy to adhere to the inside of the flue gas waste heat recovery system, such as the heat exchange pipe wall, the inner wall of the heat exchange equipment, etc. Over time, it is easy to cause blockage of the flue gas waste heat recovery system and affect its normal operation.

[0025] In order to solve the problems of sludge adhesion and blockage in the flue gas waste heat recovery system of the prior art during the waste heat recovery process of high-temperature and high-dust flue gas, this embodiment proposes a high-temperature and high-dust flue gas waste heat recovery system, as shown in the attached Figure 1 As shown, the system includes a steam superheater 1, a molten salt heat exchanger 2, a water medium pipeline, and a molten salt pipeline 8. The flue gas outlet of the steam superheater 1 is connected to the flue gas inlet of the molten salt heat exchanger 2, and the flue gas outlet of the molten salt heat exchanger 2 is connected to the downstream flue gas purification system, that is, the high-temperature and high-dust flue gas flows through the steam superheater 1 and the molten salt heat exchanger 2 in sequence. A second heat exchange tube 21 is arranged in the molten salt heat exchanger 2, and the second heat exchange tube 21 is connected to the molten salt pipeline 8 end to end in sequence to form a molten salt circulation pipeline; a first heat exchange tube 11 is arranged in the steam superheater 1, the inlet of the first heat exchange tube 11 is connected to the water medium pipeline, and the outlet of the first heat exchange tube 11 is connected to the downstream system (such as a power generation system), at least one heat exchange device is arranged in the water medium pipeline, a heat exchange tube is arranged in the heat exchange device, and the molten salt pipeline 8 is connected to the heat exchange tube.

[0026] According to the actual heat exchange balance requirements, one, two or more heat exchange devices may be provided in the water medium pipeline. Accordingly, according to the different states of the water medium in the water medium pipeline, the water medium pipeline includes a water pipe 9 and a steam pipeline 7.

[0027] Attach Figure 1For example, along the flow direction of the water medium in the water medium pipeline, the present application sequentially arranges a preheater 4 and a steam generator 3 in the water medium pipeline, a fourth heat exchange tube 41 is arranged in the preheater 4, and a third heat exchange tube 31 is arranged in the steam generator 3, the molten salt inlet and the molten salt inlet of the third heat exchange tube 31, and the molten salt inlet and the molten salt outlet of the fourth heat exchange tube 41 are all connected to the molten salt pipeline 8, so that the molten salt can enter the preheater 4 and the steam generator 3 to exchange heat with the water medium.

[0028] Regarding the flow of water medium, the water inlet of the preheater 4 is connected to the water supply device through the water pipe 9, and boiler water is supplied to the preheater 4. In the preheater 4, the boiler water undergoes a primary preheating process, exchanges heat with molten salt, and forms hot water. The water outlet of the preheater 4 is connected to the water inlet of the steam generator 3 through the water pipe 9. In the steam generator 3, the hot water undergoes a primary steam generation process, exchanges heat with molten salt, and forms steam. The steam outlet of the steam generator 3 is connected to the steam inlet of the steam superheater 1 through the steam pipeline 7. In the steam superheater 1, the steam exchanges heat with high-temperature and high-dust flue gas to form superheated steam, and then the superheated steam is transported to the downstream system (such as a thermal network, a power generation system, etc.) through the steam outlet of the steam superheater 1. As a result, the boiler water at room temperature is subjected to a two-stage heat exchange process of primary preheating and primary steam generation to form relatively high-temperature steam, which is provided to the heat exchange process in the steam superheater 1. At the same time, the two-stage heat exchange process also fully recovers the heat carried by the molten salt to facilitate the recycling of the molten salt in the system.

[0029] Therefore, for the heat exchange process of high-temperature and high-dust flue gas, the present application sets a steam superheater 1 and a molten salt heat exchanger 2 to perform a two-stage heat exchange process on the high-temperature and high-dust flue gas in sequence, especially setting a steam superheater 1 before the molten salt heat exchanger 2, and using water vapor to perform the first-stage heat exchange on the high-temperature and high-dust flue gas. Compared with the liquid-gas heat exchange technology that uses water and flue gas for heat exchange in the existing flue gas recovery system, since water vapor is a relatively high-temperature gaseous medium, during the gas-to-gas heat exchange process with the flue gas, the tube wall of the first heat exchange tube 11 can maintain a relatively high temperature, and is higher than the dew point temperature of water vapor; similarly, in the molten salt heat exchanger 2, the molten salt in the prior art is used to perform the second-stage heat exchange on the flue gas, and the temperature of the molten salt in the second heat exchange tube 21 is often higher than the dew point temperature of water vapor, so that the tube wall of the second heat exchange tube 21 can also maintain a wall temperature higher than the dew point temperature of water vapor.

[0030] This ensures that the water vapor carried by the high-temperature and high-dust flue gas will not condense during the entire waste heat recovery process, preventing the dust in the high-dust flue gas from combining with condensed water to form sludge, avoiding the problem of sludge adhesion and blockage inside the system, and is conducive to maintaining the long-term normal operation of the waste heat recovery system. At the same time, the high-temperature and high-dust flue gas undergoes a two-stage heat exchange process. Since the heat exchange temperature difference is relatively not particularly large, the high-temperature and high-dust flue gas and the corresponding heat exchange equipment can be in a step-by-step cooling process, avoiding the stress deformation and even cracking of individual components in the equipment caused by the sudden cooling heat exchange process, which is conducive to ensuring the service life of the equipment.

[0031] In the direction of flue gas flow, a flue cooler is arranged upstream of the steam superheater 1. The high-temperature and high-dust flue gas first passes through the flue cooler and is cooled to about 800°C. The flue gas enters the steam superheater 1 to exchange heat with saturated steam, and then enters the molten salt heat exchanger 2 to exchange heat with molten salt, and the flue gas is cooled to 200°C-260°C.

[0032] In the flow direction along the water medium, boiler water at room temperature enters the preheater 4, and after heat exchange with the molten salt, the water temperature is raised to 140℃-160℃; the water is heated and enters the steam generator 3, and after heat exchange with the molten salt, 240℃-260℃ saturated steam is generated; the saturated steam enters the steam superheater 1, and heat exchange with the high-temperature and high-dust flue gas, the saturated steam is heated to 340-350℃, forming superheated steam, and the superheated steam is incorporated into the thermal network or used for power generation.

[0033] The steam superheater 1, the molten salt heat exchanger 2, the steam generator 3, and the preheater 4 are all heat exchange equipment, and any one of various heat exchange equipment in the prior art can be respectively adopted, such as: the steam superheater 1, the molten salt heat exchanger 2, the steam generator 3, and the preheater 4 are all shell and tube heat exchange equipment. In the steam superheater 1, the flue gas flows through the shell side and the water vapor flows through the tube side. In the molten salt heat exchanger 2, the flue gas flows through the shell side and the molten salt flows through the tube side. In the steam generator 3 and the preheater 4, the water medium flows through the shell side and the molten salt flows through the tube side.

[0034] Correspondingly, since the second heat exchange tube 21, the third heat exchange tube 31, and the fourth heat exchange tube 41 are all flow pipelines of molten salt, they can be regarded as molten salt circulation pipelines together with the molten salt pipeline 8. Preferably, the molten salt outlet of the second heat exchange tube 21 is connected to the molten salt inlet of the third heat exchange tube 31 through the molten salt pipeline 8, and the molten salt outlet of the third heat exchange tube 31 is connected to the molten salt inlet of the fourth heat exchange tube 41 through the molten salt pipeline 8, and the molten salt outlet of the fourth heat exchange tube 41 is connected to the molten salt inlet of the second heat exchange tube 21, so that the high-temperature molten salt after heat exchange in the molten salt heat exchanger 2 first flows into the steam generator 3 to provide heat for the steam generation process, and then flows into the preheater 4 to provide heat for the water preheating process. On the one hand, it is beneficial to ensure that the generated steam has a sufficient temperature. On the other hand, since the water medium flows from the preheater 4 to the steam generator 3, and the molten salt flows from the steam generator 3 to the preheater 4, reverse heat exchange is formed between the molten salt and the water medium, which is beneficial to improve the waste heat recovery efficiency.

[0035] For the circulation of molten salt, a molten salt pump 6 is provided in the molten salt pipeline 8 to provide power support for the circulation of molten salt. In addition, a water valve is provided in the water pipe 9 between the water inlet of the preheater 4 and the external water supply device to adjust the water inlet. At the same time, the system can adjust the molten salt pump 6 and the water valve according to the fluctuation of the flue gas flow to adjust the flow of materials such as molten salt and water medium, which is conducive to ensuring the smooth operation of the system.

[0036] Taking into account the shutdown and maintenance of the system, replacement and filling of molten salt, etc., a molten salt storage tank 5 is provided in the molten salt pipeline 8 to store the molten salt, which is convenient for system maintenance, replacement and filling of molten salt, etc.

[0037] Regarding the specific setting of the molten salt storage tank 5, with reference to the flow direction of the molten salt, the present application preferably sets the molten salt storage tank 5 downstream of the fourth heat exchange tube 41. Specifically, the molten salt outlet of the fourth heat exchange tube 41 is connected to the molten salt inlet of the molten salt storage tank 5, and the molten salt outlet of the molten salt storage tank 5 is connected to the molten salt inlet of the second heat exchange tube 21, so that the high-temperature molten salt and the water medium undergo secondary heat exchange to form a molten salt with a relatively low temperature, which is then stored in the molten salt storage tank 5. On the one hand, it is prevented that the molten salt with too high a temperature causes thermal shock to the molten salt storage tank 5, and the molten salt storage tank 5 is prevented from bearing too much heat load. On the other hand, the molten salt is first heat recovered and then stored, which ensures the waste heat recovery efficiency and is also conducive to avoiding unnecessary heat loss and waste.

[0038] Further, in the direction of movement of the molten salt, the molten salt outlet of the second heat exchange tube 21 is connected to the molten salt inlet of the third heat exchange tube 31, the molten salt outlet of the third heat exchange tube 31 is connected to the molten salt inlet of the fourth heat exchange tube 41, the molten salt outlet of the fourth heat exchange tube 41 is connected to the molten salt inlet of the molten salt storage tank 5, and the molten salt outlet of the molten salt storage tank 5 is connected to the molten salt inlet of the second heat exchange tube 21 through the molten salt pump 6. Thus, in the high-temperature and high-dust flue gas waste heat recovery system, the flow direction of the molten salt can form a cycle, which can effectively avoid material loss and avoid the loss and waste of heat carried by the material.

[0039] The present application mainly relates to a flue gas waste heat recovery system. For downstream systems connected to the flue gas waste heat recovery system, such as a flue gas purification system, a power generation system, etc., the prior art can be directly referred to and this application will not elaborate on them.

[0040] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A high-temperature and high-dust flue gas waste heat recovery system, characterized in that: The system comprises a steam superheater (1), a molten salt heat exchanger (2), a water medium pipeline, and a molten salt pipeline (8); the flue gas outlet of the steam superheater (1) is connected to the flue gas inlet of the molten salt heat exchanger (2); high-temperature and high-dust flue gas can flow through the steam superheater (1) and the molten salt heat exchanger (2) in sequence; a second heat exchange tube (21) is arranged in the molten salt heat exchanger (2); the second heat exchange tube (21) and the molten salt pipeline (8) are connected end to end in sequence to form a molten salt circulation pipeline; a first heat exchange tube (11) is arranged in the steam superheater (1); the inlet of the first heat exchange tube (11) is connected to the water medium pipeline; the outlet of the first heat exchange tube (11) is connected to a downstream system; at least one heat exchange device is arranged in the water medium pipeline; a heat exchange tube is arranged in the heat exchange device; the molten salt pipeline (8) is connected to the heat exchange tube for heat exchange between molten salt and water medium.

2. A high-temperature and high-dust flue gas waste heat recovery system according to claim 1, characterized in that: In the direction of flow of the water medium, a preheater (4) and a steam generator (3) are sequentially arranged in the water medium pipeline, a fourth heat exchange tube (41) is arranged in the preheater (4), a third heat exchange tube (31) is arranged in the steam generator (3), and a molten salt inlet and a molten salt outlet of the third heat exchange tube (31) and a molten salt inlet and a molten salt outlet of the fourth heat exchange tube (41) are all connected to the molten salt pipeline (8).

3. A high-temperature and high-dust flue gas waste heat recovery system according to claim 2, characterized in that: The water medium pipeline comprises a water pipe (9) and a steam pipe (7); the water inlet of the preheater (4) is connected to a water supply device via the water pipe (9); the water outlet of the preheater (4) is connected to a water inlet of a steam generator (3) via the water pipe (9); the steam outlet of the steam generator (3) is connected to a steam inlet of a steam superheater (1) via a steam pipe (7); and the steam outlet of the steam superheater (1) is connected to a downstream system.

4. A high-temperature and high-dust flue gas waste heat recovery system according to claim 2, characterized in that: The molten salt outlet of the second heat exchange tube (21) is connected to the molten salt inlet of the third heat exchange tube (31) through the molten salt pipeline (8), the molten salt outlet of the third heat exchange tube (31) is connected to the molten salt inlet of the fourth heat exchange tube (41) through the molten salt pipeline (8), and the molten salt outlet of the fourth heat exchange tube (41) is connected to the molten salt inlet of the second heat exchange tube (21).

5. The high-temperature and high-dust flue gas waste heat recovery system according to claim 2 is characterized in that: A molten salt storage tank (5) is arranged in the molten salt pipeline (8).

6. A high-temperature and high-dust flue gas waste heat recovery system according to claim 5, characterized in that: The molten salt outlet of the fourth heat exchange tube (41) is connected to the molten salt inlet of the molten salt storage tank (5), and the molten salt outlet of the molten salt storage tank (5) is connected to the molten salt inlet of the second heat exchange tube (21).

7. The high-temperature and high-dust flue gas waste heat recovery system according to claim 1 is characterized in that: A molten salt pump (6) is arranged in the molten salt pipeline (8).

8. The high-temperature and high-dust flue gas waste heat recovery system according to claim 2, characterized in that: In the flow direction of the water medium, boiler water at room temperature enters the preheater (4), and after heat exchange with the molten salt, the water temperature is raised to 140°C-160°C; then the water enters the steam generator (3), and after heat exchange with the molten salt, saturated steam of 240°C-260°C is generated; the saturated steam enters the steam superheater (1), and heat exchange with the high-temperature and high-dust flue gas, the saturated steam is heated to 340-350°C, forming superheated steam.

9. A high-temperature and high-dust flue gas waste heat recovery system according to claim 8, characterized in that: In the direction of flue gas flow, a flue cooler is arranged upstream of the steam superheater (1). The high-temperature and high-dust flue gas is first cooled to 800°C by the flue cooler, and then enters the steam superheater (1) to exchange heat with saturated steam, and then enters the molten salt heat exchanger (2) to exchange heat with molten salt, so that the flue gas is cooled to 200°C-260°C.

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