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CN-122006446-A - Multi-layer adjustable in-furnace dry powder injection denitration system and method

CN122006446ACN 122006446 ACN122006446 ACN 122006446ACN-122006446-A

Abstract

The invention provides a multi-layer adjustable in-furnace dry powder injection denitration system and method, wherein urea dry powder is adopted to replace a traditional liquid reducing agent, and a pneumatic conveying, multi-layer adjustable injection and intelligent temperature control strategy are combined, so that the technical problems of the existing denitration system are effectively solved, the potential safety hazards of crystallization blockage and leakage corrosion of urea solution in a pipeline are thoroughly avoided in a dry powder storage and supply and full pneumatic conveying mode, a plurality of injection units are arranged at different heights of a hearth and based on real-time feedback of a temperature sensing unit and boiler load prejudgment, an injection layer of an effective denitration window at 850-1100 ℃ is automatically started by a control unit, injection temperature matching performance and denitration efficiency are remarkably improved, meanwhile, wet injection equipment is not required to be arranged in a tail flue of the system, the problem of energy efficiency reduction of a boiler caused by accumulated ash scaling is solved, and the system is safe, efficient and reliable in integral structure and particularly suitable for wide load operation and old unit reconstruction scenes.

Inventors

  • LI PINGYU
  • LI ZEGUANG
  • LI CHENYANG
  • LI SUZHEN
  • LI WENJING

Assignees

  • 广东亿工电力工程有限公司

Dates

Publication Date
20260512
Application Date
20260313

Claims (10)

  1. 1. An in-furnace dry powder injection denitration system with adjustable it is multilayer, characterized by comprising: a dry powder storage and supply unit (100) for storing and metering urea dry powder; the pneumatic conveying unit (200) is connected with the dry powder storage and supply unit (100) and is used for conveying the urea dry powder to an injection point through compressed gas; At least two injection units (300) respectively arranged in different height areas in a boiler furnace, wherein each injection unit (300) comprises at least one spray gun (310), and each spray gun (310) is used for injecting urea dry powder into a flue gas area with a corresponding height; An injection switching control valve group (400), wherein the injection switching control valve group (400) is connected between the pneumatic conveying unit (200) and each injection unit (300), and the injection switching control valve group (400) is used for selectively conducting one or more injection units (300); the temperature sensing unit (500) is used for monitoring the flue gas temperatures of different height areas in the boiler furnace in real time; The control unit (600) is electrically connected with the temperature sensing unit (500) and the injection switching control valve group (400), and the control unit (600) is configured to automatically start the injection unit (300) in a temperature window of 850-1100 ℃ for denitration according to the smoke temperature distribution corresponding to the current boiler load.
  2. 2. The multi-layer adjustable in-furnace dry powder injection denitration system according to claim 1, wherein the dry powder storage and supply unit (100) comprises a large bin (110), a small bin (120) and an electronic scale (130) arranged below the small bin (120), and the large bin (110) is communicated with the small bin (120) through a feed valve.
  3. 3. The multi-layer adjustable in-furnace dry powder injection denitration system according to claim 1, wherein the pneumatic conveying unit (200) comprises at least one Roots blower (210), an air outlet of the Roots blower (210) is connected to air inlets of a plurality of bin pumps (320) through a main pipeline, a discharge outlet of each bin pump (320) is connected with a corresponding injection unit (300) through a branch pipeline, and the bin pumps (320) comprise a left front bin pump, a left rear bin pump, a right front bin pump and a right rear bin pump, and are respectively used for feeding the spray guns (310) of the left front wall, the left rear wall, the right front wall and the right rear wall of the boiler furnace.
  4. 4. A multi-layer adjustable in-furnace dry powder injection denitration system according to claim 3, wherein the injection switching control valve group (400) comprises a feed control valve (410), a fluidization control valve (420) and an injection path switching valve (430) which are respectively arranged at the discharge ports of each bin pump (320), wherein the discharge port of each bin pump (320) is connected to at least one spray gun (310) on the corresponding wall surface sequentially 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, three interfaces of which are respectively connected with the bin pump discharge port, the front wall spray gun and the rear wall spray gun and are used for selectively conducting injection paths of the front wall or the rear wall, and the fluidization control valve (420) is connected with a compressed air source and a fluidization air inlet of the bin pump (320) and is used for fluidizing urea dry powder in the bin pump before feeding.
  5. 5. The multi-layer adjustable in-furnace dry powder injection denitration system according to claim 1, wherein the temperature sensing unit (500) comprises a plurality of temperature sensors (510), and the temperature sensors (510) are respectively installed on flue gas channels corresponding to elevations of each injection unit (300) in a boiler furnace, and are used for collecting flue gas temperatures of each injection height area in real time and transmitting signals to the control unit (600).
  6. 6. The multi-layer adjustable in-furnace dry powder injection denitration system according to claim 1, wherein the control unit (600) is further electrically connected with a boiler decentralized control system and is used for receiving a current load signal of a boiler, and the control unit (600) is configured to predict the flue gas temperature change trend of each height area in a hearth based on the boiler load signal, and dynamically select and start in advance the injection unit (300) which is about to enter an effective denitration temperature interval of (850) °c to (1100) °c in combination with the actual flue gas temperature fed back by the temperature sensing unit (500) in real time.
  7. 7. The multi-layer adjustable in-furnace dry powder injection denitration system according to claim 1, further comprising an economizer flue gas bypass adjustment device (700), wherein the economizer flue gas bypass adjustment device (700) comprises an economizer flue gas bypass inlet electric door (710) and an economizer flue gas bypass adjustment door (720), the economizer flue gas bypass inlet electric door (710) is arranged on a main flue of an economizer inlet, the economizer flue gas bypass adjustment door (720) is arranged on a bypass flue connecting the main flue and an economizer outlet flue, and the economizer flue gas bypass inlet electric door (710) and the economizer flue gas bypass adjustment door (720) are electrically connected with the control unit (600).
  8. 8. A multi-layer adjustable in-furnace dry powder injection denitration system according to claim 3, further comprising a plurality of pressure sensors, wherein the pressure sensors are respectively arranged on an outlet pipeline of the Roots blower (210), an air inlet and a discharge port of each bin pump (320) and a branch pipeline connecting the bin pump (320) and the spray gun (310), and the pressure sensors are electrically connected with the control unit (600) and are used for monitoring pipeline pressure in a pneumatic conveying process in real time.
  9. 9. The multi-layer adjustable in-furnace dry powder injection denitration system according to claim 1, wherein each spray gun (310) is provided with a cooling air interface (910), and the cooling air interfaces (910) are connected to a cooling air source through cooling air pipelines for introducing cooling air into an outer wall or an inner interlayer of the spray gun (310).
  10. 10. A multi-layer adjustable in-furnace dry powder spray denitration method according to any one of claims 1 to 9, comprising the steps of: S1, acquiring the flue gas temperatures of areas with different heights in a boiler hearth in real time through a temperature sensing unit (500); s2, acquiring a current load signal of a boiler; S3, judging whether an effective denitration temperature interval of 850-1100 ℃ exists in the flue gas temperature of the area where at least one injection unit 300 is located based on the boiler load signal and the flue gas temperature; s4, if the urea dry powder exists, starting an injection unit (300) with a corresponding height through an injection switching control valve group (400), and conveying the urea dry powder to the injection unit (300) for injection through a pneumatic conveying unit (200); s5, if the temperature of the flue gas in the area where all the injection units (300) are located is lower than 850 ℃, opening an electric door (710) of a flue gas bypass inlet of the economizer and adjusting the opening of a flue gas bypass adjusting door (720) of the economizer to enable part of high-temperature flue gas to bypass the economizer so as to raise the temperature of the flue gas at the rear part of the hearth, and returning to the step S1 to judge again; And S6, continuously monitoring the pressure state of the pneumatic conveying pipeline through a pressure sensor in the injection process, and introducing cooling air to each spray gun (310).

Description

Multi-layer adjustable in-furnace dry powder injection denitration system and method Technical Field The invention relates to the technical field of boiler flue gas denitration systems, in particular to a multi-layer adjustable in-furnace dry powder injection denitration system and method. Background In the fields of thermal power generation, industrial heat supply, chemical production and the like, coal-fired or gas-fired boilers are widely used, and a large amount of nitrogen oxides NO x can be generated in the combustion process. In order to meet the increasingly strict environmental emission standards, the selective non-catalytic reduction SNCR denitration technology is widely applied due to low investment and simple and convenient transformation. The technology generally realizes pollutant emission reduction by injecting a reducing agent such as ammonia water or urea solution into a boiler furnace and reacting with NO x at a specific temperature window of generally 850-1100 ℃ to generate harmless nitrogen and water. However, with the increasing environmental requirements, conventional SNCR techniques increasingly expose some limitations. However, the conventional SNCR system still has various technical bottlenecks, namely, firstly, the conventional system mostly adopts liquid ammonia as a reducing agent, explosion and leakage risks in the transportation, storage and use processes are gradually limited by the state, secondly, even a safer urea solution system is easy to crystallize and block under a low-temperature environment, an electric tracing system is required to be relied on to maintain operation, so that energy consumption is increased, the system is paralyzed once power is cut off or the temperature control fails, moreover, a conventional injection point is positioned at a tail flue of a boiler, the temperature of flue gas fluctuates greatly along with load, the flue gas is difficult to always maintain in an optimal reaction interval, the denitration efficiency is usually only 50% -60%, the ultra-low emission requirements of not more severe than 30 mg/m <3 > at present even in the future cannot be met, moreover, the injection position is close to heat exchange equipment such as an air preheater, ash accumulation and scaling are easy to be caused, the furnace shutdown and ash removal are required, and the thermal efficiency and the operation stability of the boiler are influenced. For a dry SNCR system, although dry powder is used as a reducing agent to avoid the crystallization problem of a liquid system, most of the existing dry powder injection systems adopt a single-layer fixed injection mode, and the injection position cannot be dynamically adjusted according to the load change of a boiler, so that the denitration efficiency is unstable, and the ultra-low emission standard is difficult to continuously meet. Therefore, a novel denitration system with reasonable structure, intrinsic safety, load change adaptation and high denitration efficiency is needed, and the ultra-low emission challenge can be effectively treated on the premise of ensuring the operation reliability, and the potential safety hazard and energy efficiency loss problems in the traditional technology are avoided. Disclosure of Invention The invention aims to solve the problems of potential safety hazard of reducing agent, easy crystallization and blockage of urea pipelines, poor matching property of spray temperature windows, low denitration efficiency and easy ash deposition of equipment, which influence the energy efficiency of a boiler, in the existing denitration system, and provides a multi-layer adjustable in-furnace dry powder spray denitration system and a method, wherein the invention adopts the following technical scheme: A multi-layer adjustable in-furnace dry powder injection denitration system, comprising: the dry powder storage and supply unit is used for storing and metering urea dry powder; The pneumatic conveying unit is connected with the dry powder storage and supply unit and is used for conveying the urea dry powder to an injection point through compressed gas; The spraying units are respectively arranged in areas with different heights in the boiler furnace, each spraying unit comprises at least one spray gun, and each spray gun is used for spraying urea dry powder to the flue gas area with the corresponding height; The injection switching control valve group is connected between the pneumatic conveying unit and each injection unit and is used for selectively conducting one or more injection units; the temperature sensing unit is used for monitoring the flue gas temperatures of different height areas in the boiler furnace in real time; The control unit is electrically connected with the temperature sensing unit and the injection switching control valve group and is configured to automatically start the injection unit in a temperature window from 850 ℃ to 1100 ℃ to perform denitration according to the smok