A full-load denitration bypass system and denitration method for a multi-fuel gas boiler with flue gas recirculation

Abstract

A full-load denitration bypass system and denitration method applied to a multi-fuel gas boiler with flue gas recirculation relates to a gas boiler denitration system and a denitration method. The invention is to solve the problem of low denitration efficiency of the denitration system of the existing multi-fuel gas boiler due to excessively high flue gas temperature at the denitration inlet. The present invention is applied to a multi-fuel gas boiler with a flue gas recirculation system and is adapted to a full-load denitration system comprising a bypass main pipe, a shut-off door, a regulating door, a plurality of bypass branches and a recirculation flue regulating door; when the denitration efficiency is reduced due to excessively high flue gas temperature at the denitration inlet due to the burning of high calorific value gas in the gas boiler, the present invention can adjust the opening of the shut-off door, the regulating door and the recirculation flue regulating door to mix the cold flue of the recirculation outlet pipe with the high-temperature flue gas in the denitration inlet flue, and finally make the mixed flue temperature meet the operation requirements of the denitration catalyst, thereby ensuring the full-load operation of the denitration system.

Description

Technical Field

[0001] The invention relates to a gas boiler denitration system and a denitration method. Background Art

[0002] In the petrochemical industry, the gas fuels used in power boilers are often very complex, with calorific values ​​varying significantly between different fuels, sometimes by more than a factor of ten. The fuels used by power boilers vary significantly throughout their lifecycle. During the startup phase, high-calorific-value gases, such as natural gas and C4, are generally used. Once the entire plant is operating normally, low-calorific-value gases such as syngas and purge gas, which are byproducts of refining, become the primary fuel for the power boilers. The SCR reactor is a flue gas denitrification device used with gas-fired boilers. The SCR reactor uses ammonia as a reducing agent. Within a temperature range of 340-400°C, ammonia reacts with NO in the flue gas to produce nitrogen and HO. If the boiler is designed for low-calorific-value gases and uses high-calorific-value gases during startup, the flue gas temperature at the denitrification inlet will exceed the upper limit of the catalyst's operating temperature, failing to meet the requirements of the denitrification catalyst and resulting in low denitrification efficiency. Summary of the Invention

[0003] In order to solve the problem of low denitration efficiency of the existing gas boiler denitration system, the present invention proposes a full-load denitration bypass system and a denitration method for a multi-fuel gas boiler with flue gas recirculation.

[0004] The present invention is applied to a full-load denitrification bypass system of a multi-fuel gas boiler with flue gas recirculation, comprising a bypass main pipe, a shutoff door, a regulating door, a plurality of bypass branches and a recirculation flue regulating door;

[0005] The flue gas circulation system in the multi-fuel gas boiler with a flue gas recirculation system is composed of a recirculation fan inlet flue, a recirculation fan and a recirculation fan outlet flue; the recirculation fan is arranged between the recirculation fan inlet flue and the recirculation fan outlet flue; the air inlet end of the recirculation fan inlet flue is connected to the preheater outlet flue in the multi-fuel gas boiler, and the air outlet end of the recirculation fan outlet flue is connected to the hot air duct in the multi-fuel gas boiler;

[0006] The recirculation flue regulating door is arranged in the recirculation fan outlet flue, the air inlet end of the bypass main pipe is connected to the recirculation fan outlet flue between the recirculation fan and the recirculation flue regulating door, the air outlet end of the bypass main pipe is connected to multiple bypass branch pipes, and the air outlet ends of the bypass branch pipes are respectively connected to the denitrification inlet flue in the denitrification reactor; the shut-off door and the regulating door are set on the bypass main pipe, and the regulating door is set on the side close to the bypass branch pipe.

[0007] The denitration method using the above-mentioned full-load denitration bypass system applied to a multi-fuel gas boiler with flue gas recirculation is carried out in the following steps:

[0008] During operation, the flue gas temperature at the denitrification inlet is adjusted by adjusting the opening of the shut-off door, regulating door, and recirculation flue regulating door in combination with the flue gas temperature at the denitrification inlet;

[0009] When the flue gas temperature at the denitrification inlet exceeds the upper limit, the opening of the regulating door of the recirculation flue is reduced, and the openings of the shut-off door and the regulating door are increased. The low-temperature flue gas is introduced into the denitrification inlet flue through the bypass main pipe, the shut-off door, the regulating door, and the bypass branch pipe, so that the low-temperature flue gas in the recirculation outlet pipe is mixed with the high-temperature flue gas in the denitrification inlet flue, and finally the mixed flue gas temperature meets the requirements for the operation of the denitrification catalyst; when the flue gas temperature at the denitrification inlet is normal, the opening of the regulating door of the circulation flue is increased, and the openings of the shut-off door and the regulating door are reduced.

[0010] The present invention has the following beneficial effects:

[0011] The present invention can adjust the openings of the shut-off door, the regulating door, and the regulating door of the recirculation flue when the denitrification efficiency of the multi-fuel gas boiler is reduced due to excessively high flue temperature in the denitrification inlet flue caused by the burning of high calorific value gas. This allows the cold flue gas in the recirculation outlet pipe to mix with the high-temperature flue gas in the denitrification inlet flue, and ultimately makes the temperature of the mixed flue gas meet the requirements for the operation of the denitrification catalyst, thereby ensuring the full-load operation of the denitrification system. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a schematic structural diagram of a full-load denitrification system adapted to a multi-fuel gas boiler with a flue gas recirculation system in Example 1.

[0013] The technical solution of the present invention is not limited to the specific implementation methods listed below, but also includes any reasonable combination of the specific implementation methods.

[0014] Specific embodiment 1: This embodiment is applied to a full-load denitrification bypass system of a multi-fuel gas boiler with flue gas recirculation, comprising a bypass main pipe (1), a shutoff door (2), a regulating door (3), a plurality of bypass branches (4) and a recirculation flue regulating door (5);

[0015] The flue gas circulation system in the multi-fuel gas boiler with a flue gas recirculation system is composed of a recirculation fan inlet flue (6), a recirculation fan (7) and a recirculation fan outlet flue (8); the recirculation fan (7) is arranged between the recirculation fan inlet flue (6) and the recirculation fan outlet flue (8); the air inlet end of the recirculation fan inlet flue (6) is connected to the preheater outlet flue in the multi-fuel gas boiler, and the air outlet end of the recirculation fan outlet flue (8) is connected to the hot air duct (9) in the multi-fuel gas boiler;

[0016] The recirculation flue regulating door (5) is arranged in the recirculation fan outlet flue (8); the air inlet end of the bypass main pipe (1) is connected to the recirculation fan outlet flue (8) between the recirculation fan (7) and the recirculation flue regulating door (5); the air outlet end of the bypass main pipe (1) is connected to a plurality of bypass branch pipes (4); the air outlet ends of the bypass branch pipes (4) are respectively connected to the denitration inlet flue in the denitration reactor; the shutoff door (2) and the regulating door (3) are arranged on the bypass main pipe (1), and the regulating door (3) is arranged on the side close to the bypass branch pipe (4).

[0017] This embodiment can adjust the openings of the shutoff door (2), the regulating door (3), and the recirculation flue regulating door (5) when the denitration inlet flue gas temperature of the multi-fuel gas boiler is too high due to the combustion of high calorific value gas, resulting in a decrease in denitration efficiency, so that the cold flue gas in the recirculation outlet pipe is mixed with the high-temperature flue gas in the denitration inlet flue gas, and finally the temperature of the mixed flue gas meets the requirements for the operation of the denitration catalyst, thereby ensuring the full-load operation of the denitration system.

[0018] Specific embodiment 2: This embodiment differs from specific embodiment 1 in that the denitration reactor is an SCR reactor.

[0019] Specific embodiment three: This embodiment differs from specific embodiment one or two in that the shutoff door (2) and the regulating door (3) are respectively connected to the bypass main pipe (1) by welding.

[0020] Specific embodiment 4: This embodiment differs from any one of specific embodiments 1 to 3 in that: the bypass main pipe (1) and the bypass branch pipe (4) are connected by welding.

[0021] Specific embodiment 5: This embodiment differs from any one of specific embodiments 1 to 4 in that the bypass branch pipe (4) is connected to the denitration inlet by welding.

[0022] Specific embodiment 6: This embodiment utilizes a denitrification method for a full-load denitrification bypass system applied to a multi-fuel gas boiler with flue gas recirculation, and is carried out in the following steps:

[0023] During operation, the flue gas temperature at the denitrification inlet is adjusted by adjusting the openings of the shutoff door (2), the regulating door (3), and the recirculation flue regulating door (5) in combination with the flue gas temperature at the denitrification inlet;

[0024] When the flue gas temperature at the denitrification inlet exceeds the upper limit, the opening of the recirculation flue regulating door (5) is reduced, and at the same time, the openings of the shutoff door (2) and the regulating door (3) are increased, and the low-temperature flue gas is introduced into the denitrification inlet flue through the bypass main pipe (1), the shutoff door (2), the regulating door (3), and the bypass branch pipe (4), so that the low-temperature flue gas in the recirculation outlet pipe is mixed with the high-temperature flue gas in the denitrification inlet flue, and finally the temperature of the mixed flue gas meets the operation requirement of the denitrification catalyst; when the flue gas temperature at the denitrification inlet is normal, the opening of the recirculation flue regulating door (5) is increased, and at the same time, the openings of the shutoff door (2) and the regulating door (3) are reduced.

[0025] This embodiment can adjust the openings of the shutoff door (2), the regulating door (3), and the recirculation flue regulating door (5) when the denitration inlet flue gas temperature is too high due to the combustion of high calorific value gas in the gas boiler, resulting in a decrease in denitration efficiency, so that the cold flue gas in the recirculation outlet pipe is mixed with the high-temperature flue gas in the denitration inlet flue gas, and finally the temperature of the mixed flue gas meets the requirements for the operation of the denitration catalyst, thereby ensuring the full-load operation of the denitration system.

[0026] Example 1:

[0027] like Figure 1 The present embodiment is applied to a full-load denitration bypass system of a multi-fuel gas boiler with flue gas recirculation, comprising a bypass main pipe (1), a shutoff door (2), a regulating door (3), a plurality of bypass branches (4) and a recirculation flue regulating door (5); the denitration reactor is an SCR reactor; the flue gas circulation system in the multi-fuel gas boiler with a flue gas recirculation system is composed of a recirculation fan inlet flue (6), a recirculation fan (7) and a recirculation fan outlet flue (8); the recirculation fan (7) is arranged between the recirculation fan inlet flue (6) and the recirculation fan outlet flue (8); the air inlet end of the recirculation fan inlet flue (6) is connected to the preheater outlet flue in the multi-fuel gas boiler, and the air outlet end of the recirculation fan outlet flue (8) is connected to the preheater outlet flue in the multi-fuel gas boiler. The air duct (9) is connected; the recirculation flue regulating door (5) is arranged in the recirculation fan outlet flue (8); the air inlet end of the bypass main pipe (1) is connected to the recirculation fan outlet flue (8) between the recirculation fan (7) and the recirculation flue regulating door (5); the air outlet end of the bypass main pipe (1) is connected to a plurality of bypass branch pipes (4); the bypass main pipe (1) and the bypass branch pipe (4) are connected by welding, and the bypass branch pipe (4) and the denitration inlet are connected by welding; the air outlet end of the bypass branch pipe (4) is respectively connected to the denitration inlet flue in the denitration reactor; the shutoff door (2) and the regulating door (3) are arranged on the bypass main pipe (1), and the regulating door (3) is arranged on the side close to the bypass branch pipe (4); the shutoff door (2) and the regulating door (3) are respectively connected to the bypass main pipe (1) by welding;

[0028] The denitration method for a multi-fuel gas boiler with a flue gas recirculation system adapted to a full-load denitration system is carried out in the following steps: during operation, the flue gas temperature at the denitration inlet is adjusted by adjusting the openings of a shutoff door (2), a regulating door (3), and a recirculation flue regulating door (5) in combination with the flue gas temperature at the denitration inlet; when the flue gas temperature at the denitration inlet exceeds the temperature, the opening of the recirculation flue regulating door (5) is reduced, and at the same time, the openings of the shutoff door (2) and the regulating door (3) are increased, and low-temperature flue gas is introduced into the denitration inlet flue through a bypass main pipe (1), a shutoff door (2), a regulating door (3), and a bypass branch pipe (4), so that the low-temperature flue gas at the recirculation outlet pipe is mixed with the high-temperature flue gas in the denitration inlet flue, and finally the mixed flue gas temperature meets the operation requirement of the denitration catalyst; when the flue gas temperature at the denitration inlet is normal, the opening of the recirculation flue regulating door (5) is increased, and at the same time, the openings of the shutoff door (2) and the regulating door (3) are reduced. This embodiment can adjust the openings of the shutoff door (2), the regulating door (3), and the recirculation flue regulating door (5) when the denitration inlet flue gas temperature of the multi-fuel gas boiler is too high due to the combustion of high calorific value gas, resulting in a decrease in denitration efficiency, so that the cold flue gas in the recirculation outlet pipe is mixed with the high-temperature flue gas in the denitration inlet flue gas, and finally the temperature of the mixed flue gas meets the operation requirements of the denitration catalyst, thereby ensuring the full-load operation of the denitration system.

Claims

1. A full-load denitrification bypass system for a multi-fuel gas boiler with flue gas recirculation, characterized by: A full-load denitrification system for a multi-fuel gas boiler with a flue gas recirculation system includes a bypass main pipe (1), a shutoff valve (2), a regulating valve (3), a plurality of bypass branches (4), and a recirculation flue regulating valve (5); The flue gas circulation system in the multi-fuel gas boiler with a flue gas recirculation system is composed of a recirculation fan inlet flue (6), a recirculation fan (7) and a recirculation fan outlet flue (8); the recirculation fan (7) is arranged between the recirculation fan inlet flue (6) and the recirculation fan outlet flue (8); the air inlet end of the recirculation fan inlet flue (6) is connected to the condenser outlet flue in the multi-fuel gas boiler, and the air outlet end of the recirculation fan outlet flue (8) is connected to the hot air duct (9) in the multi-fuel gas boiler; The recirculation flue regulating door (5) is arranged in the recirculation fan outlet flue (8), the air inlet end of the bypass main pipe (1) is connected to the recirculation fan outlet flue (8) between the recirculation fan (7) and the recirculation flue regulating door (5), the air outlet end of the bypass main pipe (1) is connected to a plurality of bypass branch pipes (4), and the air outlet ends of the bypass branch pipes (4) are respectively connected to the denitration inlet flue in the denitration reactor; the shutoff door (2) and the regulating door (3) are arranged on the bypass main pipe (1), and the regulating door (3) is arranged on the side close to the bypass branch pipe (4); The denitration reactor is an SCR reactor; The denitrification method using a full-load denitrification bypass system for a multi-fuel gas boiler with flue gas recirculation is carried out in the following steps: During operation, the flue gas temperature at the denitrification inlet is adjusted by adjusting the openings of the shutoff door (2), the regulating door (3), and the recirculation flue regulating door (5) in combination with the flue gas temperature at the denitrification inlet; When the flue gas temperature at the denitrification inlet exceeds the upper limit, the opening of the recirculation flue regulating door (5) is reduced, and at the same time, the openings of the shutoff door (2) and the regulating door (3) are increased, and the low-temperature flue gas is introduced into the denitrification inlet flue through the bypass main pipe (1), the shutoff door (2), the regulating door (3), and the bypass branch pipe (4), so that the low-temperature flue gas in the recirculation outlet pipe is mixed with the high-temperature flue gas in the denitrification inlet flue, and finally the temperature of the mixed flue gas meets the operation requirement of the denitrification catalyst; when the flue gas temperature at the denitrification inlet is normal, the opening of the recirculation flue regulating door (5) is increased, and at the same time, the openings of the shutoff door (2) and the regulating door (3) are reduced.

2. The full-load denitrification bypass system for a multi-fuel gas boiler with flue gas recirculation according to claim 1 is characterized in that: The shutoff door (2) and the regulating door (3) are respectively connected to the bypass main pipe (1) by welding.

3. The full-load denitrification bypass system for a multi-fuel gas boiler with flue gas recirculation according to claim 1 is characterized in that: The bypass main pipe (1) and the bypass branch pipe (4) are connected by welding.

4. The full-load denitrification bypass system for a multi-fuel gas boiler with flue gas recirculation according to claim 1 is characterized in that: The bypass branch pipe (4) is connected to the denitration inlet by welding.

Images