Anti-blocking flue gas waste heat utilization system for air pre-heater

Abstract

The invention belongs to the field of flue gas waste heat utilization, and particularly discloses an air pre-heater anti-blocking flue gas waste heat utilization system which comprises an air pre-heater and a first heat exchanger, and a flue gas outlet of the air pre-heater is connected with a dust removal device through the first heat exchanger so that flue gas can be used for heating cold primary air entering the air pre-heater; and one path of the second air outlet is connected with the hot secondary air duct, the other path of the second air outlet is connected with the second air inlet, and meanwhile, the second air inlet is further connected with the cold secondary air duct, so that the cold secondary air entering the air pre-heater is heated by using the hot secondary air which is cyclically converged, the temperature of the cold end of the air pre-heater is increased, and the air pre-heater is prevented from being blocked. According to the air pre-heater, the temperature of the cold end of the air pre-heater can be effectively increased, condensation of ammonium hydrogen sulfate in the air pre-heater is effectively restrained, condensation of the ammonium hydrogen sulfate can be transferred into the first heat exchanger, and therefore the anti-blocking effect of the air pre-heater is effectively improved.

Description

Technical Field

[0001] The present application belongs to the field of flue gas waste heat utilization, and more specifically, relates to a flue gas waste heat utilization system with air preheater anti-blocking function. Background Art

[0002] At present, most domestic power plants have the problem of ammonia leakage during SCR operation. After leakage, ammonia will react with SO3 in the flue gas to form ammonium bisulfate. After the ammonium bisulfate enters the air preheater, it will slowly condense at the cold end of the air preheater, causing blockage of the air preheater after a period of operation.

[0003] Currently, the main methods for solving air preheater blockage include (1) optimizing SCR operation to reduce ammonia slip; and (2) injecting SO3 adsorbent between the air preheater and SCR to reduce the generation of ammonium bisulfate. These methods can reduce the generation of ammonium bisulfate to varying degrees and inhibit air preheater blockage. However, the situation varies greatly among different power plants, and long-term operation has found that the problem of air preheater blockage still exists. Summary of the Invention

[0004] In response to the defects of the existing technology, the present application provides a flue gas waste heat utilization system with air preheater anti-blocking, which aims to solve the problem of air preheater blockage in the existing flue gas waste heat utilization system.

[0005] The present application provides a flue gas waste heat utilization system for preventing blockage of an air preheater, which specifically includes an air preheater and a first heat exchanger, wherein the cold end of the air preheater is provided with a first air inlet, a second air inlet and a flue gas outlet, and the hot end is provided with a first air outlet, a second air outlet and a flue gas inlet, the first air inlet is connected to the cold primary air duct through the first heat exchanger, and the flue gas outlet is connected to the dust removal device through the first heat exchanger, so as to use the flue gas in the first heat exchanger to heat the cold primary air entering the air preheater; the second air outlet is connected to the hot secondary air duct on one path, and is connected to the second air inlet on the other path, and the second air inlet is also connected to the cold secondary air duct at the same time, so as to use the circulated hot secondary air to heat the cold secondary air entering the air preheater, thereby increasing the temperature of the cold end of the air preheater and avoiding blockage of the air preheater.

[0006] Through the above technical solution conceived by the present application, compared with the existing technology, since the present application realizes the increase of the cold end temperature of the air preheater by adding a first heat exchanger and hot secondary air circulation, on the one hand, it can inhibit the condensation of ammonium bisulfate in the air preheater, and on the other hand, it can transfer the condensation of ammonium bisulfate to the first heat exchanger, thereby effectively improving the anti-blocking effect of the air preheater.

[0007] As a further preference, a bypass is provided on the flue gas side of the first heat exchanger so that the flue gas outlet is directly connected to the dust removal device for easy cleaning.

[0008] As a further preference, the first heat exchanger uses water as the heat transfer medium to transfer the heat in the flue gas to the cold primary air.

[0009] As a further preferred embodiment, the flue gas waste heat utilization system also includes a second heat exchanger, the hot fluid inlet of the second heat exchanger is connected to the second air outlet, the hot fluid outlet is connected to the second air inlet, the cold fluid inlet is connected to the turbine condenser outlet, and the cold fluid outlet is connected to the deaerator inlet to achieve the discharge of low-pressure cylinder extraction steam.

[0010] As a further preference, the flue gas waste heat utilization system also includes a third heat exchanger, which is arranged between the second heat exchanger and the turbine condenser. The hot fluid inlet of the third heat exchanger is connected to the outlet of the dust removal device, the hot fluid outlet is connected to the inlet of the desulfurization tower, the cold fluid inlet is connected to the outlet of the turbine condenser, and the cold fluid outlet is connected to the cold fluid inlet of the second heat exchanger, so as to use the flue gas to preliminarily heat the turbine feed water before sending it into the second heat exchanger.

[0011] As a further preference, the temperature of the cold primary air entering the air preheater is the ambient temperature.

[0012] As a further preference, the temperature of the cold secondary air entering the air preheater is the ambient temperature.

[0013] As a further preference, the circulation ratio of the hot secondary air is 0 to 25%.

[0014] In general, the above technical solutions conceived by this application have the following technical advantages compared with the existing technologies: 1. This application adds a first heat exchanger to the flue gas waste heat utilization system, allowing flue gas to heat the cold primary air entering the air preheater. Simultaneously, the hot secondary air circulation heats the cold secondary air entering the air preheater, effectively raising the temperature at the cold end of the air preheater. This not only effectively suppresses the condensation of ammonium bisulfate in the air preheater, but also transfers the condensed ammonium bisulfate to the first heat exchanger, effectively improving the air preheater's anti-clogging effect. 2. In particular, by providing a bypass on the flue gas side of the first heat exchanger, this application not only facilitates regular cleaning of the first heat exchanger to prevent condensed ammonium bisulfate from clogging the first heat exchanger, but also controls the flue gas flow entering the first heat exchanger to adjust the temperature of the cold primary air entering the air preheater. 3. At the same time, the present application introduces the feed water at the outlet of the turbine condenser into the second heat exchanger for heat absorption and then sends it to the deaerator, which can achieve the effect of displacing the steam extracted from the low-pressure cylinder. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1It is a structural schematic diagram of the flue gas waste heat utilization system for preventing air preheater blockage provided in an embodiment of the present application.

[0016] Throughout the drawings, the same reference numerals are used to denote the same elements or structures, wherein: 1-air preheater, 11-flue gas outlet, 12-first air inlet, 13-second air inlet, 14-flue gas inlet, 15-first air outlet, 16-second air outlet, 2-first heat exchanger, 3-second heat exchanger, 4-dust removal device, 5-third heat exchanger, 6-cold primary air duct, 7-cold secondary air duct, 8-hot primary air duct, 9-hot secondary air duct. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solutions and advantages of this application more clear, the following further describes this application in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0018] like Figure 1 As shown, the present application provides a flue gas waste heat utilization system with air preheater anti-blocking, specifically comprising an air preheater 1 and a first heat exchanger 2, wherein: The cold end of the air preheater 1 is provided with a first air inlet 12, a second air inlet 13 and a flue gas outlet 11, which are respectively used to introduce cold primary air, cold secondary air and discharge the flue gas after heat exchange. The hot end is provided with a first air outlet 15, a second air outlet 16 and a flue gas inlet 14, which are respectively used to discharge hot primary air, hot secondary air and the flue gas introduced into the outlet of the SCR denitrification device; The first air inlet 12 is connected to the cold primary air duct 6 through the first heat exchanger 2, and the flue gas outlet 11 is connected to the dust removal device 4 through the first heat exchanger 2, so that the flue gas is used to heat the cold primary air entering the air preheater 1 in the first heat exchanger 2. On the one hand, it can effectively increase the temperature of the cold end of the air preheater 1, inhibit the condensation of ammonium bisulfate in the air preheater 1, and transfer the condensed ammonium bisulfate to the first heat exchanger 2, thereby reducing the blockage of the air preheater. On the other hand, as the temperature of the cold end of the air preheater 1 increases, the salt discharge temperature of the flue gas will increase. By setting the first heat exchanger 2, this part of the heat can be effectively utilized, thereby improving the thermal efficiency of the flue gas waste heat utilization system; the first air outlet 15 is connected to the hot primary air duct 8, and the discharged hot primary air is sent to the coal mill for pulverizing; The second air outlet 16 is connected to the hot secondary air duct 9 on one side to be fed into the furnace for combustion support, and is connected to the second air inlet 13 on the other side. The second air inlet 13 is also connected to the cold secondary air duct 7 to utilize the circulating hot secondary air to heat the cold secondary air entering the air preheater 1, thereby increasing the cold end temperature of the air preheater 1 and preventing the air preheater 1 from being blocked. The present application increases the temperature of the cold end of the air preheater 1 by adding a first heat exchanger 2 and circulating hot secondary air. On the one hand, it can inhibit the condensation of ammonium bisulfate in the air preheater 1, and on the other hand, it can transfer the condensed ammonium bisulfate to the first heat exchanger, thereby effectively improving the anti-blocking effect of the air preheater.

[0019] Furthermore, a bypass is provided on the flue gas side of the first heat exchanger 2 so that the flue gas outlet 11 is directly connected to the dust removal device 4. On the one hand, the first heat exchanger 2 can be shut down for cleaning when it is blocked. On the other hand, the temperature of the cold primary air entering the air preheater 1 can be adjusted by controlling the flue gas flow entering the first heat exchanger 2.

[0020] Furthermore, the first heat exchanger 2 uses water as a heat transfer medium to transfer heat in the flue gas to the cold primary air.

[0021] Furthermore, the flue gas waste heat utilization system also includes a second heat exchanger 3, the hot fluid inlet of the second heat exchanger 3 is connected to the second air outlet 16, and the hot fluid outlet is connected to the second air inlet 13, so as to circulate the hot secondary air and mix it with the cold secondary air to increase the cold end temperature of the air preheater 1; the cold fluid inlet of the second heat exchanger 3 is connected to the turbine condenser outlet to pass the condensate of the turbine condenser, and the cold fluid outlet is connected to the deaerator inlet to use the hot secondary air to heat the condensate at the turbine condenser outlet, and to discharge the low-pressure cylinder steam by sending it into the deaerator.

[0022] Furthermore, the flue gas waste heat utilization system also includes a third heat exchanger 5, which is arranged in front of the second heat exchanger 3 along the flow direction of the turbine feed water, and is arranged behind the dust removal device 4 along the flow direction of the flue gas. The hot fluid inlet of the third heat exchanger 5 is connected to the outlet of the dust removal device 4, the hot fluid outlet is connected to the inlet of the desulfurization tower, the cold fluid inlet is connected to the outlet of the turbine condenser, and the cold fluid outlet is connected to the cold fluid inlet of the second heat exchanger 3, so that the turbine feed water is preliminarily heated by the flue gas before being sent to the second heat exchanger 3.

[0023] Furthermore, the temperature of the cold primary air entering the air preheater 1 is the ambient temperature, and the temperature of the cold secondary air entering the air preheater 1 is the ambient temperature. By optimizing the temperatures of the cold primary air and cold secondary air entering the air preheater 1, the cold end temperature of the air preheater 1 can be effectively increased, and the condensation of ammonium bisulfate in the air preheater 1 can be suppressed.

[0024] Furthermore, the circulation ratio of the hot secondary air is 0-25%. By optimizing the circulation ratio of the hot secondary air, the cold end temperature of the air preheater 1 can be effectively increased while ensuring the normal operation of the furnace.

[0025] In the description of this application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, "plurality" means two or more, unless otherwise specifically defined.

[0026] Additionally, references throughout this specification to "one embodiment," "one embodiment," "an example," or similar language indicate that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present application. Thus, appearances of the phrase "in one embodiment," "in one embodiment," and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.

[0027] It is easy for those skilled in the art to understand that the above is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A flue gas waste heat utilization system with air preheater anti-blocking function, characterized in that: The invention comprises an air preheater (1) and a first heat exchanger (2), wherein the cold end of the air preheater (1) is provided with a first air inlet (12), a second air inlet (13) and a flue gas outlet (11), and the hot end thereof is provided with a first air outlet (15), a second air outlet (16) and a flue gas inlet (14), the first air inlet (12) is connected to a cold primary air duct (6) through the first heat exchanger (2), and the flue gas outlet (11) is connected to a dust removal device (4) through the first heat exchanger (2). The second air outlet (16) is connected to the hot secondary air duct (9) on one side and to the second air inlet (13) on the other side. The second air inlet (13) is also connected to the cold secondary air duct (7) to heat the cold secondary air entering the air preheater (1) by utilizing the circulated hot secondary air, thereby increasing the cold end temperature of the air preheater (1) and avoiding blockage of the air preheater (1).

2. The flue gas waste heat utilization system according to claim 1, characterized in that: A bypass is provided on the flue gas side of the first heat exchanger (2), so that the flue gas outlet (11) is directly connected to the dust removal device (4), facilitating cleaning.

3. The flue gas waste heat utilization system according to claim 1, characterized in that: The first heat exchanger (2) uses water as a heat transfer medium to transfer heat in the flue gas to the cold primary air.

4. The flue gas waste heat utilization system according to claim 1, characterized in that: The flue gas waste heat utilization system further comprises a second heat exchanger (3), wherein the hot fluid inlet of the second heat exchanger (3) is connected to the second air outlet (16), the hot fluid outlet is connected to the second air inlet (13), the cold fluid inlet is connected to the turbine condenser outlet, and the cold fluid outlet is connected to the deaerator inlet, so as to realize the displacement of low-pressure cylinder extraction steam.

5. The flue gas waste heat utilization system according to claim 4, characterized in that: The flue gas waste heat utilization system also includes a third heat exchanger (5), which is arranged between the second heat exchanger (3) and the turbine condenser. The hot fluid inlet of the third heat exchanger (5) is connected to the outlet of the dust removal device (4), the hot fluid outlet is connected to the inlet of the desulfurization tower, the cold fluid inlet is connected to the outlet of the turbine condenser, and the cold fluid outlet is connected to the cold fluid inlet of the second heat exchanger (3), so that the flue gas is used to preliminarily heat the turbine feed water before sending it to the second heat exchanger (3).

6. The flue gas waste heat utilization system according to any one of claims 1 to 5, characterized in that: The temperature of the cold primary air entering the air preheater (1) is the ambient temperature.

7. The flue gas waste heat utilization system according to any one of claims 1 to 5, characterized in that: The temperature of the cold secondary air entering the air preheater (1) is the ambient temperature.

8. The flue gas waste heat utilization system according to any one of claims 1 to 5, characterized in that: The circulation ratio of hot secondary air is 0-25%.

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