Multi-layer adjustable in-furnace dry powder injection denitration system and method

Abstract

According to the multi-layer adjustable in-furnace dry powder injection denitration system and method, urea dry powder is adopted to replace a traditional liquid reducing agent, and pneumatic conveying, multi-layer adjustable injection and intelligent temperature control strategies are combined; a plurality of technical problems existing in an existing denitration system are effectively solved, the potential safety hazards of crystallization blockage and leakage corrosion of a urea solution in a pipeline are thoroughly avoided in a dry powder storage and supply and full pneumatic conveying mode, a plurality of spraying units are arranged at different heights of a hearth, and the temperature sensing unit is used for real-time feedback and boiler load pre-judgment; the control unit automatically starts the injection layer of the effective denitration window at 850-1100 DEG C, the injection temperature matching performance and the denitration efficiency are remarkably improved, meanwhile, the system does not need to arrange wet injection equipment at a tail flue, the problem that the energy efficiency of the boiler is reduced due to dust deposition and scaling is solved, the overall structure is safe, efficient and reliable, and the application range is wide. And the method is particularly suitable for wide-load operation and old unit transformation scenes.

Description

Technical Field

[0001] This invention relates to the technical field of boiler flue gas denitrification systems, and in particular to a multi-layer adjustable in-furnace dry powder injection denitrification system and method. Background Technology

[0002] Coal-fired or gas-fired boilers are widely used in thermal power generation, industrial heating, and chemical production, and their combustion process produces large amounts of nitrogen oxides (NOx). x To meet increasingly stringent environmental emission standards, selective non-catalytic reduction (SNCR) denitrification technology is widely used due to its low investment and simple retrofitting. This technology typically involves injecting a reducing agent, such as ammonia or urea solution, into the boiler furnace, where it reacts with NO within a specific temperature window, generally 850–1100℃. x The reaction produces harmless nitrogen and water, thus reducing pollutant emissions. However, with increasingly stringent environmental protection requirements, traditional SNCR technology has gradually revealed some limitations.

[0003] However, existing SNCR systems still face numerous technical bottlenecks: First, traditional systems often use liquid ammonia as a reducing agent, posing risks of explosion and leakage during transportation, storage, and use, which have been gradually restricted by the state. Second, even the relatively safe urea solution system relies on electric heat tracing systems to maintain operation because the delivery pipelines are prone to crystallization and blockage at low temperatures, increasing energy consumption and causing system paralysis in the event of power outages or temperature control failures. Furthermore, conventional injection points are located in the boiler tail flue, where flue gas temperature fluctuates greatly with load, making it difficult to maintain the optimal reaction range, resulting in low denitrification efficiency, typically only 50%–60%, which cannot meet the current ultra-low emission requirements of ≤30 mg / m³ or even more stringent requirements in the future. In addition, the injection location is close to heat exchange equipment such as air preheaters, which easily causes ash accumulation and scaling, requiring frequent boiler shutdowns for cleaning, affecting boiler thermal efficiency and operational stability. For dry SNCR systems, although using dry powder as a reducing agent avoids the crystallization problem of liquid systems, most existing dry powder injection systems adopt a single-layer fixed injection method, which cannot dynamically adjust the injection position according to boiler load changes, resulting in unstable denitrification efficiency and difficulty in continuously meeting ultra-low emission standards.

[0004] Therefore, there is an urgent need for a new type of denitrification system that is structurally sound, inherently safe, adaptable to load changes, and highly efficient in denitrification, which can effectively address the challenges of ultra-low emissions while ensuring operational reliability, and avoid the safety hazards and energy loss problems existing in traditional technologies. Summary of the Invention

[0005] The purpose of this invention is to address the problems of reducing agent safety hazards, easy crystallization and blockage of urea pipelines, poor matching of injection temperature windows, low denitrification efficiency, and easy ash accumulation in equipment affecting boiler energy efficiency in existing denitrification systems. This invention provides a multi-layer adjustable in-furnace dry powder injection denitrification system and method, employing the following technical solution: A multi-layer adjustable in-furnace dry powder injection denitrification system includes: Dry powder storage and supply unit, used to store and measure urea dry powder; A pneumatic conveying unit, which is connected to the dry powder storage and supply unit, is used to convey urea dry powder to the injection point by compressed gas. At least two injection units are respectively set in different height areas inside the boiler furnace. Each injection unit includes at least one spray gun, which is used to spray urea dry powder into the flue gas area at the corresponding height. An injection switching control valve group is connected between the pneumatic delivery unit and each injection unit, and the injection switching control valve group is used to selectively activate one or more of the injection units; A temperature sensing unit is used to monitor the flue gas temperature at different heights within the boiler furnace in real time. The control unit is electrically connected to the temperature sensing unit and the injection switching control valve group. The control unit is configured to automatically activate the injection unit within the temperature window of 850℃ to 1100℃ to carry out the denitrification reaction according to the flue gas temperature distribution corresponding to the current boiler load.

[0006] As described above, a multi-layer adjustable in-furnace dry powder injection denitrification system includes a dry powder storage and supply unit comprising a large silo, a small silo, and an electronic scale disposed below the small silo. The large silo is connected to the small silo via a feed valve.

[0007] As described above, in a multi-layer adjustable in-furnace dry powder injection denitrification system, the pneumatic conveying unit includes at least one Roots blower. The outlet of the Roots blower is connected to the inlet of multiple chamber pumps via a main pipeline. The outlet of each chamber pump is connected to the corresponding injection unit via a branch pipeline. The chamber pumps include a left front chamber pump, a left rear chamber pump, a right front chamber pump, and a right rear chamber pump, which are used to supply material to the spray guns on the left front wall, left rear wall, right front wall, and right rear wall of the boiler furnace, respectively.

[0008] As described above, a multi-layer adjustable in-furnace dry powder injection denitrification system includes an injection switching control valve group comprising a feed control valve, a fluidization control valve, and an injection path switching valve respectively disposed at the discharge port of each of the silo pumps. Each silo pump discharge port is sequentially connected to at least one spray gun on the corresponding wall via the feed control valve and the injection path switching valve. The injection path switching valve is a pneumatic three-way valve, with its three ports connected to the silo pump discharge port, the front wall spray gun, and the rear wall spray gun, respectively, for selectively guiding the injection path of the front or rear wall. The fluidization control valve connects a compressed air source to the fluidization air inlet of the silo pump, for fluidizing the urea dry powder in the silo pump before feeding.

[0009] As described above, in a multi-layer adjustable in-furnace dry powder injection denitrification system, the temperature sensing unit includes multiple temperature sensors. These temperature sensors are respectively installed in the flue gas channels corresponding to the elevations of each injection unit inside the boiler furnace, and are used to collect the flue gas temperature in each injection height area in real time and transmit the signal to the control unit.

[0010] As described above, in a multi-layer adjustable in-furnace dry powder injection denitrification system, the control unit is also electrically connected to the boiler distributed control system to receive the current boiler load signal. The control unit is configured to: predict the flue gas temperature change trend in each height area of ​​the furnace based on the boiler load signal, and dynamically select and activate the injection unit that is about to enter the effective denitrification temperature range of ℃ to ℃ in advance, in conjunction with the actual flue gas temperature fed back in real time by the temperature sensing unit.

[0011] The multi-layer adjustable in-furnace dry powder injection denitrification system described above further includes an economizer flue gas bypass regulating device. The economizer flue gas bypass regulating device includes an economizer flue gas bypass inlet electric valve and an economizer flue gas bypass adjusting valve. The economizer flue gas bypass inlet electric valve is installed on the main flue at the economizer inlet, and the economizer flue gas bypass adjusting valve is installed on the bypass flue connecting the main flue and the economizer outlet flue. Both the economizer flue gas bypass inlet electric valve and the economizer flue gas bypass adjusting valve are electrically connected to the control unit.

[0012] The multi-layer adjustable in-furnace dry powder injection denitrification system described above also includes multiple pressure sensors. The pressure sensors are respectively installed on the outlet pipe of the Roots blower, the air inlet and discharge outlet of each of the silo pumps, and the branch pipe connecting the silo pumps and the spray gun. All pressure sensors are electrically connected to the control unit and are used to monitor the pipeline pressure in real time during the pneumatic conveying process.

[0013] As described above, in a multi-layer adjustable in-furnace dry powder injection denitrification system, each of the spray guns is provided with a cooling air interface, which is connected to a cooling air source through a cooling air duct to introduce cooling air into the outer wall or internal interlayer of the spray gun.

[0014] The multi-layer adjustable in-furnace dry powder injection denitrification method described above includes the following steps: S1. The temperature of flue gas in different height areas inside the boiler furnace is collected in real time through the temperature sensing unit; S2. Obtain the current load signal of the boiler; S3. Based on the boiler load signal and the flue gas temperature, determine whether there is at least one injection unit whose flue gas temperature is within the effective denitrification temperature range of 850°C to 1100°C. S4. If present, the corresponding injection unit is activated by the injection switching control valve group, and the urea dry powder is transported to the injection unit via the pneumatic conveying unit for injection. S5. If the flue gas temperature in the area where all injection units are located is below 850℃, open the electric door of the economizer flue gas bypass inlet and adjust the opening of the economizer flue gas bypass adjustment door so that some high-temperature flue gas bypasses the economizer to increase the flue gas temperature at the rear of the furnace, and return to step S1 to re-judge. S6. During the spraying process, the pressure status of the pneumatic delivery pipeline is continuously monitored by the pressure sensor, and cooling air is introduced into each spray gun.

[0015] Implementing the embodiments of the present invention has the following beneficial effects: 1. In this invention, by using dry urea powder to replace the traditional liquid reducing agent, and combining it with pneumatic conveying, multi-layer adjustable injection, and intelligent temperature control strategies, several technical problems existing in the current denitrification system are effectively solved: the dry powder storage and supply and the full pneumatic conveying method completely avoid the safety hazards of urea solution crystallization blockage and leakage corrosion in the pipeline. By setting multiple injection units at different heights in the furnace, and based on real-time feedback from the temperature sensing unit and boiler load prediction, the control unit automatically activates the injection layer in the effective denitrification window of 850℃–1100℃, which significantly improves the injection temperature matching and denitrification efficiency. At the same time, the system does not need to install wet injection equipment in the tail flue, eliminating the problem of boiler energy efficiency reduction caused by ash accumulation and scaling. The overall structure is safe, efficient, and reliable, and is especially suitable for wide-load operation and old unit renovation scenarios. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a block diagram of a multi-layer adjustable in-furnace dry powder injection denitrification system according to the present invention.

[0018] Explanation of reference numerals in the attached figures 100. Dry powder storage and supply unit; 110. Large silo; 120. Small silo; 130. Electronic scale; 200. Pneumatic conveying unit; 210. Roots blower; 300. Injection unit; 310. Spray gun; 320. Silo pump; 400. Injection switching control valve group; 410. Feed control valve; 420. Fluidization control valve; 430. Injection path switching valve; 500. Temperature sensing unit; 510. Temperature sensor; 600. Control unit; 700. Economizer flue gas bypass regulating device; 710. Economizer flue gas bypass inlet electric door; 720. Economizer flue gas bypass adjusting door; 910. Cooling air interface. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] like Figure 1 As shown, the present invention proposes a multi-layer adjustable in-furnace dry powder injection denitrification system, wherein the dry powder storage and supply unit 100 is used to store and measure urea dry powder. A pneumatic conveying unit 200 is connected to the dry powder storage and supply unit 100 and is used to convey urea dry powder to the injection point by compressed gas. At least two injection units 300 are respectively arranged in different height areas inside the boiler furnace. Each injection unit 300 includes at least one spray gun 310, which is used to spray urea dry powder into the flue gas area at the corresponding height. Injection switching control valve group 400 is connected between the pneumatic delivery unit 200 and each injection unit 300. The injection switching control valve group 400 is used to selectively activate one or more of the injection units 300. Temperature sensing unit 500, the temperature sensing unit 500 is used to monitor the flue gas temperature in different height areas inside the boiler furnace in real time; Control unit 600, which is electrically connected to temperature sensing unit 500 and injection switching control valve group 400, is configured to automatically activate injection unit 300 within a temperature window of 850℃ to 1100℃ to carry out denitrification reaction according to the flue gas temperature distribution corresponding to the current boiler load.

[0021] Furthermore, as a preferred embodiment of the present invention and not a limitation thereof, the dry powder storage and supply unit 100 includes a large hopper 110, a small hopper 120, and an electronic scale 130 disposed below the small hopper 120. The large hopper 110 is connected to the small hopper 120 through a feed valve.

[0022] Furthermore, as a preferred embodiment of the present invention and not a limitation thereof, the pneumatic conveying unit 200 includes at least one Roots blower 210. The air outlet of the Roots blower 210 is connected to the air inlet of multiple silo pumps 320 through a main pipe. The discharge port of each silo pump 320 is connected to the corresponding spraying unit 300 through a branch pipe. The silo pumps 320 include a left front silo pump, a left rear silo pump, a right front silo pump, and a right rear silo pump, which are respectively used to supply material to the spray guns 310 on the left front wall, left rear wall, right front wall, and right rear wall of the boiler furnace.

[0023] Furthermore, as a preferred embodiment of the present invention and not a limitation thereof, the injection switching control valve group 400 includes a feed control valve 410, a fluidization control valve 420, and an injection path switching valve 430 respectively disposed at the discharge port of each of the silo pumps 320. The discharge port of each silo pump 320 is sequentially connected to at least one spray gun 310 on the corresponding wall via the feed control valve 410 and the injection path switching valve 430. The injection path switching valve 430 is a pneumatic three-way valve, with its three ports connected to the silo pump discharge port, the front wall spray gun, and the rear wall spray gun, respectively, for selectively guiding the injection path of the front or rear wall. The fluidization control valve 420 connects a compressed air source to the fluidization air inlet of the silo pump 320, for fluidizing the urea powder in the silo pump before feeding.

[0024] Furthermore, as a preferred embodiment of the present invention and not a limitation thereof, the temperature sensing unit 500 includes a plurality of temperature sensors 510, which are respectively installed on the flue gas channels corresponding to the elevation of each injection unit 300 in the boiler furnace, for real-time acquisition of flue gas temperature in each injection height area and transmission of the signal to the control unit 600.

[0025] Furthermore, as a preferred embodiment of the present invention and not a limitation thereof, the control unit 600 is also electrically connected to the boiler distributed control system for receiving the current boiler load signal. The control unit 600 is configured to: predict the flue gas temperature change trend in each height region of the furnace based on the boiler load signal, and combine the actual flue gas temperature fed back in real time by the temperature sensing unit 500, dynamically select and activate the injection unit 300 in advance when it is about to enter the effective denitrification temperature range of 850°C to 1100°C.

[0026] Furthermore, as a preferred embodiment of the present invention and not a limitation thereof, it also includes an economizer flue gas bypass regulating device 700, which includes an economizer flue gas bypass inlet electric door 710 and an economizer flue gas bypass adjusting door 720. The economizer flue gas bypass inlet electric door 710 is disposed on the main flue at the economizer inlet, and the economizer flue gas bypass adjusting door 720 is disposed on the bypass flue connecting the main flue and the economizer outlet flue. Both the economizer flue gas bypass inlet electric door 710 and the economizer flue gas bypass adjusting door 720 are electrically connected to the control unit 600.

[0027] Furthermore, as a preferred embodiment of the present invention and not a limitation thereof, it also includes a plurality of pressure sensors, which are respectively disposed on the outlet pipe of the Roots blower 210, the air inlet and discharge outlet of each of the silo pumps 320, and the branch pipe connecting the silo pumps 320 and the spray gun 310. All pressure sensors are electrically connected to the control unit 600 and are used to monitor the pipeline pressure in real time during the pneumatic conveying process.

[0028] Furthermore, as a preferred embodiment of the present invention and not a limitation thereof, each of the spray guns 310 is provided with a cooling air interface 910, which is connected to a cooling air source through a cooling air duct for introducing cooling air into the outer wall or internal interlayer of the spray gun 310. Example

[0029] This embodiment provides a multi-layer adjustable in-furnace dry powder injection denitrification system, the system including a dry powder storage and supply unit 100, a pneumatic conveying unit 200, at least two injection units 300, an injection switching control valve group 400, a temperature sensing unit 500, a control unit 600, and an economizer flue gas bypass regulating device 700.

[0030] The dry powder storage and supply unit 100 includes a large silo 110, a small silo 120, and an electronic scale 130 disposed below the small silo 120. The large silo 110 is connected to the small silo 120 through a control valve and is used for buffer storage and precise measurement of urea dry powder.

[0031] The pneumatic conveying unit 200 includes at least one Roots blower 210. In this embodiment, two Roots blowers 210 are used, and their outlets are connected to the inlets of multiple silo pumps 320 via main pipes. The outlet of each silo pump 320 is connected to a corresponding spraying unit 300 via branch pipes. The silo pumps 320 include a left front silo pump, a left rear silo pump, a right front silo pump, and a right rear silo pump, which are used to supply material to the spray guns 310 on the left front wall, left rear wall, right front wall, and right rear wall of the boiler furnace, respectively.

[0032] Each of the spraying units 300 includes at least one spray gun 310, which is installed in three height zones at elevations of 62,000 mm, 66,000 mm and 71,000 mm in the boiler furnace, respectively, for spraying urea dry powder into the flue gas zone at the corresponding height.

[0033] The spray switching control valve group 400 includes a feed control valve 410, a fluidization control valve 420, and a spray path switching valve 430 respectively disposed at the discharge port of each silo pump 320. The discharge port of each silo pump 320 is connected to the spray gun 310 on the corresponding wall through the feed control valve 410 and the spray path switching valve 430 in sequence. The spray path switching valve 430 is a pneumatic three-way valve, and its three ports are respectively connected to the discharge port of the silo pump, the front wall spray gun, and the rear wall spray gun. The fluidization control valve 420 is connected to the compressed air source and the fluidization air inlet of the silo pump 320.

[0034] The temperature sensing unit 500 includes multiple temperature sensors 510, specifically including a first temperature sensor 510a set at an elevation of 62,000 mm, a second temperature sensor 510b set at an elevation of 66,000 mm, and a third temperature sensor 510c set at an elevation of 71,000 mm, for real-time acquisition of flue gas temperature in each injection height area and transmission of the signal to the control unit 600.

[0035] The control unit 600 is electrically connected to the temperature sensing unit 500, the injection switching control valve group 400 and the Roots blower 210, and is electrically connected to the boiler distributed control system via a signal line. It is used to receive the current load signal of the boiler. The control unit 600 is configured to automatically activate the injection unit 300, which is within the temperature window of 850℃ to 1100℃, according to the flue gas temperature distribution corresponding to the current boiler load.

[0036] The system also includes an economizer flue gas bypass regulating device 700, which includes an economizer flue gas bypass inlet electric door 710 and an economizer flue gas bypass adjusting door 720. The economizer flue gas bypass inlet electric door 710 is located on the main flue at the economizer inlet, and the economizer flue gas bypass adjusting door 720 is located on the bypass flue connecting the main flue and the economizer outlet flue. Both the economizer flue gas bypass inlet electric door 710 and the economizer flue gas bypass adjusting door 720 are electrically connected to the control unit 600.

[0037] In addition, the system is equipped with multiple pressure sensors, which are respectively installed on the outlet pipe of the Roots blower 210, the air inlet and discharge outlet of each chamber pump 320, and the branch pipe connecting the chamber pump 320 and the spray gun 310. All pressure sensors are electrically connected to the control unit 600 and are used to monitor the pipeline pressure in real time during the pneumatic conveying process.

[0038] Each of the spray guns 310 is provided with a cooling air inlet 910, which is connected to a cooling air source through a cooling air duct to introduce cooling air into the outer wall or internal interlayer of the spray gun 310.

[0039] The work process is as follows: When the boiler operating load is 450 MW, the control unit 600 receives feedback from the third temperature sensor 510c at an elevation of 71000 mm that the flue gas temperature is 920℃, while the temperatures at 62000 mm and 66000 mm are 780℃ and ℃ respectively. Therefore, it is determined that only the upper layer is within the effective denitrification temperature range. The control unit 600 then opens the feed control valves 410 and injection path switching valves 430 corresponding to the left front chamber pump, left rear chamber pump, right front chamber pump, and right rear chamber pump, starts a Roots blower 210 and adjusts its frequency conversion output to deliver urea dry powder to each spray gun 310 in the upper layer for injection. At the same time, cooling air is continuously introduced into all spray guns 310 through the cooling air interface 910. If the boiler load drops to 200 MW and the temperatures of all three layers are below 800℃, the control unit 600 will open the economizer flue gas bypass inlet electric door 710 and adjust the opening of the economizer flue gas bypass adjusting door 720 to allow some high-temperature flue gas to bypass the economizer. After the temperature in the 71000 mm area rises back to 860℃, the upper layer injection will be restarted. Example

[0040] The difference between this embodiment and Embodiment 1 is that it is suitable for smaller capacity boilers. The injection unit 300 has only two layers, located in the lower and middle areas of the furnace, respectively. There are two silo pumps 320, corresponding to the left and right front walls, respectively. No rear wall spray guns are provided. Therefore, the injection path switching valve 430 is only used for unidirectional flow. The dry powder storage and supply unit 100 adopts a combination of a single large silo and a single small silo. The pneumatic conveying unit 200 is equipped with a Roots blower 210. The temperature sensing unit 500 includes two temperature sensors 510, corresponding to the injection heights of the two layers mentioned above. The connection methods and control logic of the remaining components, including the injection switching control valve group 400, the economizer flue gas bypass regulating device 700, the pressure sensor, the cooling air interface 910, and the control unit 600, are consistent with those of Embodiment 1.

[0041] The work process is as follows: When the boiler is under medium to high load, if the flue gas temperature in the upper injection zone is within the effective denitrification temperature range of 850℃ to 1100℃, the control unit 600 will activate the corresponding silo pump 320 and spray gun 310 for injection. When the load is further reduced, causing the temperature of all injection zones to be below 850℃, the control unit 600 will open the economizer flue gas bypass inlet electric door 710 and adjust the opening of the economizer flue gas bypass adjusting door 720 to allow some high-temperature flue gas to bypass the economizer, thereby increasing the flue gas temperature at the furnace outlet. After the temperature in the upper zone rises back to the effective window, the system will automatically resume injection, thus maintaining denitrification efficiency within a wide load range. Example

[0042] The main difference between this embodiment and Embodiment 1 is that the economizer flue gas bypass regulating device 700 is not installed in the system, that is, the economizer flue gas bypass inlet electric door 710 and the economizer flue gas bypass regulating door 720 are not included. The structure, quantity and connection relationship of the remaining components, including the dry powder storage and supply unit 100, the pneumatic conveying unit 200, the three-layer injection unit 300, the injection switching control valve group 400, the temperature sensing unit 500, the control unit 600, the pressure sensor and the cooling air interface 910, are exactly the same as those in Embodiment 1.

[0043] Accordingly, the control strategy is simplified as follows: the control unit 600 selects the layer in the three-layer injection unit 300 that is in the effective denitrification temperature range of 850°C to 1100°C based only on the flue gas temperature fed back by each temperature sensor 510. When the temperature of all layers exceeds this range, the system stops injection and issues a prompt, and no longer performs bypass adjustment.

[0044] The work process is as follows: During normal boiler operation, the control unit 600 continuously receives flue gas temperature signals from three temperature sensors 510. When the temperature of a certain layer, such as the 71,000 mm elevation layer, is within the effective denitrification window of 850°C to 1100°C, the control unit 600 opens the feed control valve 410 of the corresponding silo pump 320 and the injection path switching valve 430, starts the Roots blower 210 to deliver urea dry powder to the spray guns 310 of that layer, and simultaneously introduces cooling air into all spray guns.

[0045] If the boiler load increases, causing the temperature of all three spray layers to exceed 1100℃ (overheating condition), or if the load decreases, causing the temperature of all three spray layers to fall below 850℃ (deep peak shaving), the control unit 600 will automatically stop all injection operations and issue a "No effective denitrification temperature range" prompt signal through the human-machine interface. After the boiler operating conditions are adjusted back and any spray layer re-enters the 850℃–1100℃ range, the system will automatically resume injection. Example

[0046] The main difference between this embodiment and Embodiment 1 is that the injection unit 300 is only arranged on the right front wall and right rear wall of the boiler furnace, and no injection gun 310 is installed on the left side. Correspondingly, the silo pump 320 is only provided with two pumps, the right front silo pump and the right rear silo pump, and the injection path switching valve 430 in the injection switching control valve group 400 is only connected to the injection guns on the right front and rear walls. The structure and connection relationship of the remaining components, including the dry powder storage and supply unit 100, the pneumatic conveying unit 200, the three-layer injection height corresponding elevation area, the temperature sensing unit 500, the control unit 600, the economizer flue gas bypass regulating device 700, the pressure sensor, and the cooling air interface 910, are the same as in Embodiment 1.

[0047] The work process is as follows: The control unit 600 determines which layer is within the effective denitrification window of 850℃ to 1100℃ based on the flue gas temperature in the right-side area of ​​the furnace fed back by the three temperature sensors 510. For example, when the flue gas temperature on the right side of the 71000 mm elevation is 920℃, while the temperatures of other layers do not meet the requirements, the control unit 600 opens the feed control valves 410 corresponding to the right front chamber pump and the right rear chamber pump, and selects to activate the upper spray guns 310 on the right front wall and / or rear wall for urea dry powder injection through the injection path switching valve 430.

[0048] Because the spray guns are only positioned on the right side, the system compensates for the reduced coverage area by improving the uniformity of spraying on one side, such as by coordinating with the front and rear walls and extending the spraying time. Even when the temperature of the entire layer is below 850°C due to low load, the economizer flue gas bypass regulating device 700 can still be activated to raise the flue gas temperature, and spraying can continue on the effective layer on the right side after the temperature recovers. Based on the above system, the present invention also provides a multi-layer adjustable in-furnace dry powder injection denitrification method, which specifically includes the following steps: S1. Real-time temperature data acquisition Multiple temperature sensors 510 in the temperature sensing unit 500 are installed in the boiler furnace in areas corresponding to each injection height to continuously collect the flue gas temperature in each area and transmit the temperature signal to the control unit 600 in analog or digital communication mode to ensure that the temperature change trend can be captured in a timely manner.

[0049] S2. Obtain the current load signal of the boiler. The control unit 600 obtains the current boiler load signal from the distributed boiler control system via hardwire or communication interface, and uses it as a feedforward variable to predict the flue gas temperature distribution trend.

[0050] S3. Comprehensive assessment of the effective denitrification window The control unit 600 compares the current load signal with the "load-temperature field" mapping relationship in the historical operation database to preliminarily predict the flue gas temperature changes of each injection layer in the next 3-5 minutes. Simultaneously, it combines this with real-time feedback from the temperature sensor 510 to determine whether at least one injection unit 300's area has a flue gas temperature within the effective denitrification temperature range of 850℃ to 1100℃. If a layer's temperature is at the edge of this range, such as 840℃ or 1120℃, the system can initiate "trend judgment": if the temperature is trending upwards, it prepares to activate in advance; if it is trending downwards, it delays activation to avoid frequent switching.

[0051] S4. Activate the corresponding injection unit and execute injection. If a valid layer exists, the control unit 600 outputs the following command: Open the fluidization control valve 420 of the corresponding silo pump 320 and introduce compressed air to fluidize the dry powder for 10–15 seconds; Then, open the feed control valve 410 and the injection path switching valve 430 to select the front wall or rear wall path. Start the Roots blower 210 synchronously and adjust its frequency converter to stabilize the delivered air pressure at 0.25–0.35 MPa; Urea powder is delivered to the target spray gun 310 via pneumatic conveying unit 200 for atomized spraying; Meanwhile, cooling air is continuously supplied to all spray guns 310 through cooling air inlet 910 to prevent burn-out.

[0052] S5. Bypass linkage regulation under low temperature conditions If the temperature of all sprayed layers is below 850°C, the control unit 600 performs the following operations: Pause all jetting actions; Open the economizer flue gas bypass inlet electric door 710; The opening of the economizer flue gas bypass regulating valve 720 is dynamically adjusted according to the current load and the rate of temperature drop. This allows some of the high-temperature flue gas to bypass the economizer and directly enter the tail flue, thereby increasing the flue gas temperature at the furnace outlet and in the horizontal flue area. Return to step S1 and continue monitoring the temperature until any spray layer rises back to above 850°C, then proceed to step S4.

[0053] S6. Throughout the injection process, the system continuously implements the following safety measures: The pressure sensor monitors the pressure at the outlet of the Roots blower, the inlet and outlet of the silo pump, and the branch pipes in real time. If the pressure in a branch increases abnormally, such as exceeding the set threshold of 0.4 MPa, it is determined to be a pipe blockage. The feed control valve 410 and the fluidization control valve 420 of that branch are immediately closed, and an audible and visual alarm is triggered. If the pressure remains low, it is determined to be an air leak or a fan malfunction. When the cooling air pressure or flow rate is lower than the set value, the spray gun must not be put into operation to prevent dry burning.

[0054] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A multi-layer adjustable in-furnace dry powder injection denitrification system, characterized in that, include: Dry powder storage and supply unit (100) is used to store and meter urea dry powder; A pneumatic conveying unit (200) is connected to the dry powder storage and supply unit (100) and is used to convey urea dry powder to the injection point by compressed gas. At least two injection units (300) are respectively arranged in different height areas inside the boiler furnace. Each injection unit (300) includes at least one spray gun (310), which is used to spray urea dry powder into the flue gas area at the corresponding height. Injection switching control valve assembly (400) is connected between the pneumatic delivery unit (200) and each injection unit (300), and the injection switching control valve assembly (400) is used to selectively activate one or more of the injection units (300). Temperature sensing unit (500) is used to monitor the flue gas temperature at different heights in the boiler furnace in real time. Control unit (600), which is electrically connected to temperature sensing unit (500) and injection switching control valve group (400), is configured to automatically activate injection unit (300) within the temperature window of 850℃ to 1100℃ to carry out denitrification reaction according to the flue gas temperature distribution corresponding to the current boiler load.

2. The multi-layer adjustable in-furnace dry powder injection denitrification system according to claim 1, characterized in that, The dry powder storage and supply unit (100) includes a large silo (110), a small silo (120), and an electronic scale (130) located below the small silo (120). The large silo (110) is connected to the small silo (120) through a feed valve.

3. The multi-layer adjustable in-furnace dry powder injection denitrification system according to claim 1, characterized in that, The pneumatic conveying unit (200) includes at least one Roots blower (210). The air outlet of the Roots blower (210) is connected to the air inlet of multiple silo pumps (320) through a main pipe. The discharge port of each silo pump (320) is connected to the corresponding spraying unit (300) through a branch pipe. The silo pump (320) includes a left front silo pump, a left rear silo pump, a right front silo pump, and a right rear silo pump, which are used to supply material to the spray guns (310) on the left front wall, left rear wall, right front wall, and right rear wall of the boiler furnace, respectively.

4. The multi-layer adjustable in-furnace dry powder injection denitrification system according to claim 3, characterized in that, The injection switching control valve group (400) includes a feed control valve (410), a fluidization control valve (420), and an injection path switching valve (430) respectively disposed at the discharge port of each of the silo pumps (320). The discharge port of each silo pump (320) is connected to at least one of the spray guns (310) on the corresponding wall through the feed control valve (410) and the injection path switching valve (430). The injection path switching valve (430) is a pneumatic three-way valve, and its three ports are respectively connected to the discharge port of the silo pump, the front wall spray gun, and the rear wall spray gun, for selectively guiding the injection path of the front wall or the rear wall. The fluidization control valve (420) is connected to the compressed air source and the fluidization air inlet of the silo pump (320), for fluidizing the urea dry powder in the silo pump before feeding.

5. The multi-layer adjustable in-furnace dry powder injection denitrification system according to claim 1, characterized in that, The temperature sensing unit (500) includes multiple temperature sensors (510), which are respectively installed on the flue gas channels corresponding to the elevation of each injection unit (300) in the boiler furnace, for real-time collection of flue gas temperature in each injection height area and transmission of the signal to the control unit (600).

6. The multi-layer adjustable in-furnace dry powder injection denitrification system according to claim 1, characterized in that, The control unit (600) is also electrically connected to the boiler distributed control system to receive the current load signal of the boiler. The control unit (600) is configured to: predict the flue gas temperature change trend in each height area of ​​the furnace based on the boiler load signal, and dynamically select and activate the injection unit (300) that is about to enter the effective denitrification temperature range of (850)℃ to (1100)℃ in advance, in combination with the actual flue gas temperature fed back in real time by the temperature sensing unit (500).

7. A multi-layer adjustable in-furnace dry powder injection denitrification system according to claim 1, characterized in that, It also includes an economizer flue gas bypass regulating device (700), which includes an economizer flue gas bypass inlet electric valve (710) and an economizer flue gas bypass adjusting valve (720). The economizer flue gas bypass inlet electric valve (710) is located on the main flue at the economizer inlet, and the economizer flue gas bypass adjusting valve (720) is located on the bypass flue connecting the main flue and the economizer outlet flue. Both the economizer flue gas bypass inlet electric valve (710) and the economizer flue gas bypass adjusting valve (720) are electrically connected to the control unit (600).

8. A multi-layer adjustable in-furnace dry powder injection denitrification system according to claim 3, characterized in that, It also includes multiple pressure sensors, which are respectively installed on the outlet pipe of the Roots blower (210), the air inlet and discharge outlet of each of the silo pumps (320), and the branch pipe connecting the silo pumps (320) and the spray gun (310). All pressure sensors are electrically connected to the control unit (600) and are used to monitor the pipeline pressure in real time during the pneumatic conveying process.

9. A multi-layer adjustable in-furnace dry powder injection denitrification system according to claim 1, characterized in that, Each of the spray guns (310) is provided with a cooling air inlet (910), which is connected to a cooling air source through a cooling air duct to introduce cooling air into the outer wall or inner interlayer of the spray gun (310).

10. A multi-layer adjustable in-furnace dry powder injection denitrification method according to any one of claims 1 to 9, characterized in that, Includes the following steps: S1. The flue gas temperature in different height areas inside the boiler furnace is collected in real time through the temperature sensing unit (500); S2. Obtain the current load signal of the boiler; S3. Based on the boiler load signal and the flue gas temperature, determine whether there is at least one area where the flue gas temperature of the injection unit 300 is located is within the effective denitrification temperature range of 850°C to 1100°C. S4. If present, the corresponding injection unit (300) is activated by the injection switching control valve group (400), and the urea dry powder is conveyed to the injection unit (300) via the pneumatic conveying unit (200) for injection; S5. If the flue gas temperature in the area where all injection units (300) are located is lower than 850°C, open the economizer flue gas bypass inlet electric door (710) and adjust the opening of the economizer flue gas bypass adjustment door (720) so that some high-temperature flue gas bypasses the economizer, thereby increasing the flue gas temperature at the rear of the furnace, and return to step S1 to re-judge. S6. During the spraying process, the pressure status of the pneumatic delivery pipeline is continuously monitored by the pressure sensor, and cooling air is introduced into each spray gun (310).

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