Economizer bypass system

Abstract

The utility model provides an economizer bypass system. The economizer bypass system comprises a flue, and an upper-level economizer, an SCR denitration catalyst bed layer and a lower-level economizer are sequentially arranged in the flue in the flue gas treatment direction. The water outlet end of the upper-level economizer is connected with the steam pocket, and the steam pocket is further connected with the downcomer; the lower-level economizer is connected with a water supply source through a water supply pipeline; the water supply pipeline is connected with the downcomer through a first one-way valve; and the downcomer between the joint of the first one-way valve and the downcomer and the steam pocket is also connected with the water inlet end of the lower-stage economizer through a circulating pump and a second one-way valve. According to the system, through the arrangement, the temperature of flue gas entering the SCR denitration catalyst bed layer is increased, and the defects that due to the fact that a single economizer water supply bypass is arranged traditionally, the water flow is not easy to control, and hydrodynamic force checking is strict are overcome.

Description

Technical Field

[0001] The present application relates to the technical field of boilers, and in particular to an economizer bypass system. Background Art

[0002] In order to reduce the emission of pollutants during boiler operation and meet the national environmental protection requirements, the denitrification device needs to be put into operation at all loads of boiler operation to reduce the emission of nitrogen oxides in flue gas. In order to ensure the denitrification efficiency and the safe operation of the equipment, the operation of the denitrification device has certain requirements for the flue gas temperature, usually requiring its inlet flue gas temperature to be within the range of 295℃~420℃. The boiler is designed to reduce the exhaust gas temperature and improve the thermal efficiency. It usually sets a sufficient economizer heating area to reduce the outlet flue gas temperature of the economizer as much as possible, especially under low load. Because the outlet flue gas temperature of the economizer is low, it cannot meet the operation requirements of the denitrification device.

[0003] Therefore, in order to increase the temperature entering the deNOx catalyst bed, an economizer flue gas bypass is set up. This method is to lead out a bypass pipe from the main water supply pipe, and directly transport part of the water supply to the water-cooled wall inlet through the bypass, and the water supply does not enter the economizer for heat exchange with the flue gas, thereby reducing the flue gas heat exchange and increasing the flue gas temperature at the economizer outlet. Although this method has a simple layout, it only uses one bypass pipe to adjust the water flow entering the economizer, thereby controlling the flue gas temperature entering the deNOx catalyst bed. Therefore, strict hydrodynamic calibration is required, and the water flow is not easy to control. Utility Model Content

[0004] The present application provides an economizer bypass system to solve the problem that strict hydraulic dynamics verification is required and water flow is difficult to control in the above-mentioned method of setting an economizer flue gas bypass to increase the flue gas temperature.

[0005] The present application provides an economizer bypass system, comprising a flue, wherein the flue includes an upper economizer, an SCR denitration catalyst bed and a lower economizer in sequence along the flue gas processing direction;

[0006] The upper economizer and the lower economizer are connected, the water outlet of the upper economizer is connected to the steam drum, and the steam drum is also connected to the downcomer;

[0007] The lower economizer is connected to the water supply source through a water supply pipeline;

[0008] The water supply pipeline is connected to the downcomer through a first one-way valve;

[0009] The connection point between the first one-way valve and the downcomer and the downcomer between the steam drums are also connected to the water inlet end of the lower economizer through a circulating pump and a second one-way valve.

[0010] Optionally, the flue at the flue gas input end of the upper economizer and the flue between the upper economizer and the SCR denitration catalyst bed are also connected through a bypass flue.

[0011] Optionally, a throttle valve is provided on the bypass flue.

[0012] Optionally, an expansion joint is provided on the bypass flue, and an ash blocking net is provided inside the expansion joint, wherein the mesh openings of the ash blocking net are in the shape of elongated strips, regular hexagons or squares.

[0013] Optionally, a guide is provided between the upper economizer and the SCR denitration catalyst bed.

[0014] One side of the deflector is open and communicated with the smoke output end of the bypass flue.

[0015] Optionally, the deflector comprises a frame, a guide groove is arranged on one side of the frame, a plurality of guide plates are arranged in an array between the guide groove and a side of the frame opposite to the guide groove, and the guide plates are parallel to the traveling direction of the smoke;

[0016] One side of the guide groove is open and connected to the smoke output end of the bypass flue; a side of the guide groove close to the smoke input direction is also provided with an opening.

[0017] Optionally, a temperature detector is further provided between the upper economizer and the SCR denitration catalyst bed, and the temperature detector is electrically connected to the controller;

[0018] The controller is also electrically connected to the circulation pump and the throttle valve.

[0019] The system of the present application connects the water supply pipe with the downcomer through a pipe provided with a first one-way valve, and diverts part of the water supplied by the water supply source to the downcomer, thereby reducing the amount of circulating water entering the upper economizer, so as to reduce the heat of the flue gas absorbed by the upper economizer; and at the same time, part of the hot water in the downcomer is circulated to the upper economizer through a circulating pump, thereby increasing the temperature of the working water in the upper economizer and reducing the absorption of flue gas heat by the working water in the upper economizer. The system of the present application achieves the goal of increasing the temperature of the flue gas entering the SCR deNOx catalyst bed through the above-mentioned setting, and overcomes the disadvantages of the traditional single economizer water supply bypass, which results in difficult control of water flow and strict hydrodynamic verification.

[0020] In addition, the lower economizer connected to the upper economizer can further recover the heat in the flue gas and reduce energy waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 A schematic diagram of an economizer bypass system provided in one embodiment of the present application;

[0023] Figure 2 A schematic diagram of an economizer bypass system provided in another embodiment of the present application;

[0024] Figure 3 A schematic diagram of an economizer bypass system provided in yet another embodiment of the present application;

[0025] Figure 4 A schematic diagram of the structure of an expansion joint provided in one embodiment of the present application;

[0026] Figure 5 A schematic diagram of an economizer bypass system provided in yet another embodiment of the present application;

[0027] Figure 6 A schematic diagram of the structure of a flow guide provided in one embodiment of the present application;

[0028] Figure 7 A schematic diagram of an economizer bypass system provided in accordance with an embodiment of the present application.

[0029] Description of reference numerals:

[0030] 1. Flue; 2. Upper economizer; 3. SCR denitration catalyst bed; 4. Lower economizer; 5. Steam drum; 6. Water supply source; 7. Bypass flue; 8. Guide device; 9. Controller; 31. Temperature detector; 41. Circulation pump; 51. Downcomer; 71. Throttle valve; 72. Expansion joint; 81. Frame; 82. Guide trough; 83. Guide plate; 100. First one-way valve; 200. Second one-way valve; 721. Ash screen. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application is clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work also fall within the scope of protection of the present application.

[0032] like Figure 1As shown, the present application provides an economizer bypass system, including a flue 1, wherein the flue 1 includes an upper economizer 2, an SCR denitration catalyst bed 3 and a lower economizer 4 in sequence along the flue gas processing direction;

[0033] The upper economizer 2 is connected to the lower economizer 4, the water outlet of the upper economizer 2 is connected to the steam drum 5, and the steam drum 5 is also connected to the downcomer 51;

[0034] The lower economizer 4 is connected to the water supply source 6 through a water supply pipeline;

[0035] The water supply pipeline is connected to the downcomer 51 through the first one-way valve 100;

[0036] The downcomer 51 between the connection point of the first non-return valve 100 and the downcomer 51 and the steam drum 5 is also connected to the water inlet end of the lower economizer 4 through the circulating pump 41 and the second non-return valve 200.

[0037] Along the flow direction of the working water: When in use, the water supply source 6 supplies part of the desalinated working water to the lower economizer 4 through the water supply pipe, which is used to absorb the waste heat of the flue gas passing through the SCR denitration catalyst bed 3, and at the same time plays the role of preheating the working water entering the upper economizer 4. The other part is directly supplied to the downcomer 51 through the first one-way valve 100 to absorb the heat of the furnace combustion. The working water supplied to the lower economizer 4 will go up to the upper economizer 2 to absorb the heat of the flue gas, and at the same time heat the working water in the upper economizer 2. The heated working water is output from the economizer outlet header and enters the drum 5 for expansion. Part of the working water is vaporized to form high-temperature and high-pressure steam, and after steam-water separation, the high-temperature and high-pressure steam is output from the drum 5 and used to drive the steam turbine to do work after reheating.

[0038] The working medium water after steam-water separation in the steam drum 5 enters the downcomer 51 to absorb the heat of fuel combustion in the furnace. At the same time, part of the high-temperature working medium water in the downcomer 51 is sucked by the high-temperature resistant circulation pump 41 and supplied to the lower economizer 4 through the second one-way valve 200. The working medium water in the downcomer 51 is combined with the water supplied by the water supply source 6, which can increase the water temperature entering the lower economizer 4, thereby reducing the absorption of flue gas heat by the upper economizer 2, so as to achieve the purpose of increasing the flue gas temperature entering the SCR denitration catalyst bed 3.

[0039] Along the flue gas flow direction: When in use, the flue gas discharged from the furnace absorbs heat through the superheater and reheater, and then enters the upper economizer 2, exchanges heat with the working water in the upper economizer 2, heats the working water, and reduces the temperature of the flue gas at the same time. The flue gas after heat exchange with the upper economizer 2 goes down and enters the SCR denitration catalyst bed 3. The high-temperature flue gas entering the SCR denitration catalyst bed 3 contacts and reacts with the ammonia water or urea sprayed by the ammonia spraying device in the SCR denitration catalyst bed 3, reducing the nitrogen oxides in the flue gas into nitrogen, thereby achieving the purpose of denitration.

[0040] The flue gas that has completed denitration in the SCR denitration catalyst bed 3 enters the lower economizer 4 after passing through the SCR denitration catalyst bed 3, and exchanges heat with the working water in the lower economizer 4, further recovering the heat in the flue gas and reducing heat waste. The flue gas after passing the lower economizer 4 is discharged after subsequent dust removal, desulfurization and other treatments.

[0041] In the present application, since a bypass pipe of the first one-way valve 100 is provided to connect the water supply pipe with the downcomer 51, and the circulating pump 41 circulates part of the hot water in the downcomer 51 to the upper economizer 2, these two methods jointly adjust the water flow and water temperature of the upper economizer 2, thereby adjusting the absorption of flue gas heat by the upper economizer 2 to increase the temperature of the flue gas entering the SCR deNOx catalyst bed 3. These two methods can work together to enable the water flow rate supplied by the water supply source 6 to the upper economizer 2 to be adjusted within a wider range, which makes it easier to control the water flow rate entering the upper economizer 2, thereby avoiding the traditional practice of only setting up an economizer bypass, which requires strict calibration of the water flow rate entering the economizer (that is, hydrodynamic calibration).

[0042] The system of the present application connects the water supply pipe with the downcomer 51 through a pipe provided with a first one-way valve 100, and guides part of the water supplied by the water supply source 6 to the downcomer 51, thereby reducing the amount of circulating water entering the upper economizer 2, so as to reduce the heat of the flue gas absorbed by the upper economizer 2; and at the same time, part of the hot water in the downcomer 51 is circulated to the upper economizer 2 through the circulating pump 41, thereby increasing the temperature of the working water in the upper economizer 2 and reducing the absorption of flue gas heat by the working water in the upper economizer 2. The system of the present application realizes the improvement of the temperature of the flue gas entering the SCR denitrification catalyst bed 3 through the above-mentioned setting, and overcomes the disadvantages of the traditional single economizer water supply bypass, which results in the difficult control of water flow and strict hydrodynamic verification.

[0043] In addition, the lower economizer 4 connected to the upper economizer 2 can further recover the heat in the flue gas and reduce energy waste.

[0044] like Figure 2As shown, optionally, the flue 1 at the flue gas input end of the upper economizer 2 and the flue 1 between the upper economizer 2 and the SCR denitration catalyst bed 3 are also connected through a bypass flue 7.

[0045] In the present application, a bypass flue 7 is provided to introduce part of the high-temperature flue gas that has not exchanged heat with the upper economizer 2 into the upper part of the SCR denitrification catalyst bed 3, and combine it with the flue gas after heat exchange with the upper economizer 2 to increase the temperature of the flue gas entering the SCR denitrification catalyst bed 3.

[0046] like Figure 2 As shown, optionally, a throttle valve 71 is provided on the bypass flue 7 .

[0047] In the present application, a throttle valve 71 is provided on the bypass flue 7 , and the flow rate of the high-temperature flue gas entering the bypass flue 7 can be adjusted by the throttle valve 71 .

[0048] like Figure 3 and Figure 4 As shown, optionally, an expansion joint 72 is provided on the bypass flue 7, and an ash blocking net 721 is provided inside the expansion joint 72. The mesh of the ash blocking net 721 is in the shape of a long strip, a regular hexagon or a square.

[0049] In the present application, when the flue gas passes through the economizer, some large clumps of smoke dust therein will be intercepted by the economizer, and since the flue gas in the bypass flue 7 has not passed through the upper economizer 2, the dust content therein is relatively large. If not treated, these smoke dusts will adhere to the catalyst bed, resulting in reduced catalytic efficiency and even failure of the catalyst bed in severe cases. Therefore, the expansion joint 72 is provided to buffer the pipeline pressure on the one hand, and secondly, the flue gas entering the expansion joint 72 can reduce the air flow velocity, making it easier for the ash screen 721 to intercept the smoke dust.

[0050] like Figure 5 As shown, optionally, a guide 8 is further provided between the upper economizer 2 and the SCR denitration catalyst bed 3.

[0051] One side of the flow guide 8 is open and communicated with the smoke output end of the bypass flue 7 .

[0052] In the present application, the deflector 8 is provided to guide the flue gas introduced by the bypass flue 7 , which is beneficial for mixing with the flue gas passing through the upper economizer 2 .

[0053] like Figure 6 As shown, optionally, the deflector 8 includes a frame 81, a side surface of the frame 81 is provided with a deflection groove 82, and a plurality of deflector plates 83 are arranged in an array between the deflection groove 82 and a side surface of the frame 81 opposite to the deflection groove 82, and the deflector plates 83 are parallel to the traveling direction of the smoke;

[0054] One side of the guide groove 82 is open and communicated with the smoke output end of the bypass flue 7; one side of the guide groove 82 close to the smoke input direction is also provided with an opening.

[0055] In the present application, when in use, the flue gas in the bypass flue 7 enters from the opening of the guide groove 82 on one side of the guide device 8, and after the flow direction is adjusted by the guide groove 82, it is output from the opening on the side of the guide groove 82 close to the flue gas input direction, and merges with the flue gas passing through the upper economizer 2 to increase the temperature of the flue gas entering the SCR denitration catalyst bed 3. The heated flue gas enters the SCR denitration catalyst bed 3 through the space between the guide plates 83 in the guide device 8 that are parallel to the flue gas direction.

[0056] like Figure 7 As shown, optionally, a temperature detector 31 is further provided between the upper economizer 2 and the SCR denitration catalyst bed 3, and the temperature detector 31 is electrically connected to the controller 9;

[0057] The controller 9 is also electrically connected to the circulation pump 41 and the throttle valve 71 .

[0058] In the present application, according to the specific conditions of the flue gas temperature, the controller 9 can control the opening and closing of the circulation pump 41 and the throttle valve 71, such as opening them at the same time or keeping them closed at the same time, or opening one of them, so as to achieve flexible control of the circulation pump 41 and the throttle valve 71 according to the different flue gas temperatures.

[0059] An economizer bypass system, the working process of which is as follows:

[0060] Along the flow direction of the working water: When in use, the water supply source 6 supplies part of the desalinated working water to the lower economizer 4 through the water supply pipe, which is used to absorb the waste heat of the flue gas passing through the SCR denitration catalyst bed 3, and at the same time plays the role of preheating the working water entering the upper economizer 4. The other part is directly supplied to the downcomer 51 through the first one-way valve 100 to absorb the heat of the furnace combustion. The working water supplied to the lower economizer 4 will go up to the upper economizer 2 to absorb the heat of the flue gas, and at the same time heat the working water in the upper economizer 2. The heated working water is output from the economizer outlet header and enters the drum 5 for expansion. Part of the working water is vaporized to form high-temperature and high-pressure steam, and after steam-water separation, the high-temperature and high-pressure steam is output from the drum 5 and used to drive the steam turbine to do work after reheating.

[0061] The working medium water after steam-water separation in the drum 5 enters the downcomer 51 to absorb the heat of fuel combustion in the furnace. At the same time, the temperature detector 31 monitors the temperature of the flue gas entering the SCR denitration catalyst bed 3 in real time, and feeds back the temperature data to the controller 9. When the temperature detector 31 detects that the flue gas temperature is lower than the preset value (for example, 310°C), the temperature detector 31 transmits the temperature data to the controller 9, and the controller 9 controls the circulation pump 41 to start, and part of the high-temperature working medium water in the downcomer 51 is sucked by the high-temperature resistant circulation pump 41, and supplied to the lower economizer 4 through the second one-way valve 200. The working medium water in the downcomer 51 and the water supplied by the water supply source 6 can increase the water temperature entering the lower economizer 4, thereby reducing the absorption of flue gas heat by the upper economizer 2, so as to achieve the purpose of increasing the flue gas temperature entering the SCR denitration catalyst bed 3.

[0062] Along the flue gas flow direction: When in use, the flue gas discharged from the furnace absorbs heat through the superheater and reheater, and then enters the upper economizer 2, exchanges heat with the working water in the upper economizer 2, heats the working water, and reduces the temperature of the flue gas. The flue gas after heat exchange with the upper economizer 2 goes down to the SCR denitration catalyst bed 3, and the temperature detector 31 detects the temperature of the flue gas. When the temperature detector 31 detects that the flue gas temperature is lower than the preset value (for example, 310°C), the temperature detector 31 transmits the temperature data to the controller 9, and the controller 9 controls the throttle valve 71 to open, and guides part of the flue gas in the flue 1 that has not entered the upper economizer 2 into the bypass flue 7. The flue gas entering the bypass flue 7 enters the guide device 8 through the bypass flue 7 after the ash screen 721 intercepts the large clumps of particulate ash in the flue gas.

[0063] The flue gas in the bypass flue 7 enters from the opening of the guide groove 82 on one side of the guide device 8, and after the flow direction is adjusted by the guide groove 82, it is output from the opening on the side of the guide groove 82 close to the flue gas input direction, and merges with the flue gas passing through the upper economizer 2 to increase the temperature of the flue gas entering the SCR denitration catalyst bed 3. The heated flue gas enters the SCR denitration catalyst bed 3 through the space between the guide plates 83 in the guide device 8 that are parallel to the flue gas direction.

[0064] The high-temperature flue gas entering the SCR denitration catalyst bed 3 contacts and reacts with the ammonia water or urea sprayed by the ammonia spraying device in the SCR denitration catalyst bed 3, reducing the nitrogen oxides in the flue gas into nitrogen, thereby achieving the purpose of denitration.

[0065] The flue gas that has completed denitration in the SCR denitration catalyst bed 3 enters the lower economizer 4 after passing through the SCR denitration catalyst bed 3, and exchanges heat with the working water in the lower economizer 4, further recovering the heat in the flue gas and reducing heat waste. The flue gas after passing the lower economizer 4 is discharged after subsequent dust removal, desulfurization and other treatments.

[0066] When in use, according to the specific conditions of the flue gas temperature, the controller 9 can control the opening and closing of the circulation pump 41 and the throttle valve 71, such as opening them at the same time or keeping them closed at the same time, or opening one of them, so as to achieve flexible control of the circulation pump 41 and the throttle valve 71 according to different flue gas temperatures.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, ordinary technicians in the field should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. An economizer bypass system, characterized in that: The invention comprises a flue (1), wherein the flue (1) comprises an upper economizer (2), an SCR denitration catalyst bed (3) and a lower economizer (4) in sequence along the flue gas processing direction; The upper economizer (2) and the lower economizer (4) are connected, the water outlet end of the upper economizer (2) is connected to the steam drum (5), and the steam drum (5) is also connected to the downcomer (51); The lower economizer (4) is connected to a water supply source (6) via a water supply pipeline; The water supply pipeline is connected to the downcomer (51) via a first one-way valve (100); The connection point between the first non-return valve (100) and the downcomer (51) and the steam drum (5) is also connected to the water inlet end of the lower economizer (4) through a circulating pump (41) and a second non-return valve (200).

2. The economizer bypass system according to claim 1, characterized in that: The flue (1) at the flue gas input end of the upper economizer (2) and the flue (1) between the upper economizer (2) and the SCR denitration catalyst bed (3) are also connected via a bypass flue (7).

3. The economizer bypass system according to claim 2, characterized in that: The bypass flue (7) is provided with a throttle valve (71).

4. The economizer bypass system according to claim 2, characterized in that: The bypass flue (7) is provided with an expansion joint (72), and an ash blocking net (721) is provided inside the expansion joint (72). The mesh of the ash blocking net (721) is in the shape of a long strip, a regular hexagon or a square.

5. The economizer bypass system according to claim 2, characterized in that: A flow guide (8) is also provided between the upper economizer (2) and the SCR denitration catalyst bed (3). One side of the deflector (8) is open and communicates with the smoke output end of the bypass flue (7).

6. The economizer bypass system according to claim 5, characterized in that: The deflector (8) comprises a frame (81), A guide groove (82) is arranged on one side of the frame (81), and a plurality of guide plates (83) are arranged in an array between the guide groove (82) and a side of the frame (81) opposite to the guide groove (82), and the guide plates (83) are parallel to the traveling direction of the smoke; One side of the guide groove (82) is open and communicates with the smoke output end of the bypass flue (7); a side of the guide groove (82) close to the smoke input direction is also provided with an opening.

7. The economizer bypass system according to any one of claims 2 to 6, characterized in that: A temperature detector (31) is also provided between the upper economizer (2) and the SCR denitration catalyst bed (3), and the temperature detector (31) is electrically connected to the controller (9); The controller (9) is also electrically connected to the circulation pump (41) and the throttle valve (71).

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