A multi-channel steam boiler and its control method

Abstract

This invention relates to the field of steam boiler technology, and more particularly to a multi-channel steam boiler and its control method, comprising a boiler drum and a furnace; the furnace contains a combustion chamber and a settling chamber; the lower part of the combustion chamber is the main combustion zone, the upper part is the re-combustion zone, and the settling chamber constitutes the burnout zone. The main combustion zone, re-combustion zone, and burnout zone form a three-stage combustion subsystem. This invention achieves a carbon burnout rate >99.5% through the three-stage combustion subsystem, reducing the initial NOx emission to 100-150 mg / Nm³, thus improving combustion efficiency. After passing through a flue gas treatment system, the final NOx emission is reduced to 50 mg / Nm³, further reducing pollutant emissions. The fuel adaptability is extended to 18 types of agricultural and forestry waste. The intelligent combustion control method monitors and regulates the boiler's operating status in real time, ensuring combustion quality.

Description

Technical Field

[0001] This invention relates to the field of steam boiler technology, specifically to a multi-channel steam boiler and its control method. Background Technology

[0002] Steam boilers are key equipment for the utilization of renewable energy. They generate steam or heat by burning agricultural and forestry waste such as straw, rice husks, and wood chips. They are widely used in industrial heating, district heating, and biomass power generation. The core technology lies in efficient combustion, pollutant control, and equipment reliability, which directly affect energy conversion efficiency and environmental compliance.

[0003] A search revealed a Chinese patent document that discloses a dual-steam boiler (application number: CN109556102B), which includes a first boiler, a second boiler, a water tank, and a burner. It makes full use of the waste heat from the combustion of energy in the first boiler, improves the boiler's thermal efficiency, and at the same time reduces fuel consumption in the combustion chamber and lowers the flue gas temperature.

[0004] However, its combustion chamber is a single-space design, which cannot achieve zoned combustion of fuel, resulting in insufficient fuel burnout rate. The ratio of the width of the combustion chamber to the width of the first boiler body is (3 / 4-4 / 5):1, which easily forms local high-temperature zones, promoting the formation of thermal NOx. NOx emissions rely entirely on the passive reduction of combustion temperature, resulting in poor environmental compliance. Furthermore, it cannot expand the adaptability to fuels. Alkali metals such as K / Na in the fuel can easily lead to poor equipment reliability and a fast high-temperature corrosion rate. At the same time, it only achieves water level safety control through water level sensors and float valves, and cannot monitor and control key parameters of the combustion process (such as air volume, furnace temperature, and fuel characteristics). Summary of the Invention

[0005] The purpose of this invention is to provide a multi-channel steam boiler and control method, which can improve combustion efficiency and reduce pollutant emissions through a three-stage combustion subsystem, further reduce NOx pollutant emissions through a flue gas treatment system, improve equipment reliability by using corrosion-resistant heating surfaces, and adapt to various fuel characteristics.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a multi-channel steam boiler, comprising a boiler body, the boiler body including a boiler drum and a furnace; the furnace is provided with a combustion chamber and a settling chamber; the lower part of the combustion chamber is the main combustion zone, the upper part is the re-combustion zone, the settling chamber constitutes the burnout zone, the main combustion zone is provided with a reciprocating grate inclined at 15°, equipped with inclined secondary air nozzles and primary air regulating dampers, the re-combustion zone is provided with a slag-collecting pipe, and the burnout zone is a cavity design; the main combustion zone, the re-combustion zone and the burnout zone constitute a three-stage combustion subsystem.

[0007] Corrosion-resistant heating surfaces: The superheater is made of high-temperature corrosion resistant ASME material; the economizer is made of corrosion-resistant steel; the air preheater is made of enamel tubes or corrosion-resistant alloy steel tubes. The enamel tubes are made of carbon steel or Corten steel as the base material, and the corrosion-resistant alloy steel tubes have a base carbon steel or Corten steel inner layer, a rare earth alloy middle layer, and a corrosion-resistant sealing agent outer layer.

[0008] The flue gas generated in the combustion zone enters the flue gas treatment system through the superheater, evaporator and economizer; the process flow of the flue gas treatment system includes: the flue gas is treated by a multi-tube dust collector, a desulfurization dry reactor, a bag dust collector and a denitrification system, and then enters the economizer, air preheater and chimney, and is finally discharged into the atmosphere.

[0009] Preferably, it also includes a composite heating surface subsystem, which includes radiant heating surfaces used in the furnace and settling chamber; convective heating surfaces used in the superheater, economizer and air preheater; flag-type heating surfaces used in the evaporator; and multi-point ash collection in conjunction with the ash hopper.

[0010] Preferably, the boiler drum is arranged horizontally, and the length of the straight section can be adjusted according to the model. There is a manhole on each end cap of the boiler drum, and a wire mesh separator and a steam equalization plate are installed inside the boiler drum. The boiler body is a front and rear arched covered furnace structure. The boiler body is surrounded by a membrane water-cooled fully sealed structure. The size of the furnace and the heating surface vary according to the boiler evaporation capacity.

[0011] Preferably, after the high-temperature flue gas turns 90° at the furnace outlet, it laterally washes over the three rows of slag-laden tube bundles formed by the water-cooled rear wall.

[0012] Preferably, the superheater, evaporator, economizer and air preheater are convective heating surfaces, and each is equipped with a convective tube bundle. The convective tube bundle adopts a horizontal serpentine tube and straight tube structure. The evaporator is arranged with a total of 3 sets of serpentine tubes, and the tube bundle at the inlet section of the heating surface is inclined upward at 10°.

[0013] Preferably, the fuel on the reciprocating grate is ignited from both sides except at the head of the fire bed. The reciprocating grate consists of a feeding hopper, a support, a movable beam, a fixed beam, a front windbreak door for the grate bars, and a transmission system. The grate bars include movable grate bars and fixed grate bars. The working surface of the reciprocating grate consists of movable grate bars and fixed grate bars. The movable grate bars move in the forward and reverse directions of the pushing beam. The movement of the movable frame is provided by the transmission system. The fixed grate bars always remain relatively stationary on the fixed beam. The two sides of the reciprocating grate surface are sealed to the support by vertical plates or blocks.

[0014] Preferably, the reciprocating grate is equipped with segmented air supply, with several independent air chambers separated from each other arranged along the longitudinal direction of the grate. The primary air entering the air chamber from the air boxes or air ducts on both sides of the grate is decelerated by airflow diffusion and evenly fills the air chamber. The air intake of each air chamber can be adjusted by an air regulating device.

[0015] Preferably, the boiler body is a frame structure, and the weight of the boiler body is supported on four support points on the lower headers of the left and right side walls, of which the right front support is a fixed point, and the other three points allow free expansion in the horizontal direction and allow the boiler body to expand freely upward.

[0016] A control method for a multi-channel steam boiler includes the following steps:

[0017] Step S1: Based on the type of fuel currently being used, obtain the key parameters of the fuel and establish a fuel characteristic database;

[0018] Key parameters include industrial analytical components, elemental composition, and lower heating value. Industrial analytical components include moisture, ash, volatile matter, and fixed carbon.

[0019] Step S2: Monitor and assess the boiler's operating status in real time;

[0020] When the boiler load is detected to be ≥30%, a real-time control strategy is triggered; the judgment is based on the percentage of rated evaporation, and the calculation data comes from the value of the main steam outlet flow meter.

[0021] Step S3: Execute real-time control strategies;

[0022] Increase the secondary air volume by 15%; reduce the grate speed by at least 20%; dynamically adjust the proportion of primary air volume to total air volume based on the current fuel composition. Implement graded air distribution, multi-stage combustion, add regulating valves to the secondary air main duct, arrange secondary air nozzles in a downward-sloping manner, and staggered alignment on the front and rear walls to increase disturbance and penetration.

[0023] Step S4: Combustion quality target control;

[0024] Ensure that the carbon content of the bottom ash is less than 8%.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. This invention comprises a three-stage combustion subsystem consisting of a main combustion zone, a re-combustion zone, and a burnout zone. The main combustion zone features a 15° inclined reciprocating grate equipped with inclined secondary air nozzles and a primary air regulating damper. The re-combustion zone incorporates a slag-collecting pipe to enhance internal circulation. The primary air regulating damper allows for flexible adjustment of grate air intake and primary air distribution. The inclined arrangement of the secondary air improves combustion. The slag-collecting pipe arrangement increases flue gas disturbance, promoting the burnout rate of the three-stage combustion. The burnout zone features a cavity design, increasing flue gas residence time by >2 seconds. This three-stage combustion subsystem achieves a carbon burnout rate of >99.5%, reducing NOx emissions from 400 mg / Nm³ to 100-150 mg / Nm³, thus improving combustion efficiency.

[0027] 2. In the flue gas treatment system of the present invention, the flue gas is treated by a multi-tube dust collector, a desulfurization dry reactor, a bag filter and a denitrification system, and then enters the economizer, air preheater and chimney before being discharged into the atmosphere. The final NOx emission is reduced to 50mg / Nm³, thus reducing the emission of pollutants.

[0028] 3. The superheater, economizer and air preheater of the present invention adopt corrosion-resistant heating surfaces, which improves the reliability of the equipment and extends its service life.

[0029] 4. The fuel adaptability of this invention is extended to 18 types of agricultural and forestry waste, saving economic costs.

[0030] 5. This invention uses an intelligent combustion control method to monitor and regulate the boiler's operating status in real time, ensuring combustion quality and achieving automated combustion control, thus reducing labor costs. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the boiler body in this invention;

[0032] Figure 2 This is a schematic diagram of the overall system structure in this invention;

[0033] Figure 3 This is a schematic diagram of the reciprocating grate structure in this invention;

[0034] Figure 4 In this invention Figure 1 A magnified view of a portion of point A;

[0035] Figure 5 This is a flowchart of the control method in this invention.

[0036] In the diagram: 1. Boiler body; 2. Boiler drum; 3. Furnace; 4. Main combustion zone; 5. Reburning zone; 6. Settling chamber; 7. Reciprocating grate; 71. Feed hopper; 72. Support frame; 73. Movable beam; 74. Fixed beam; 75. Transmission system; 76. Movable grate bars; 77. Fixed grate bars; 78. Independent air chamber; 8. Secondary air nozzle; 9. Slag condensation pipe; 10. Superheater; 11. Evaporator; 12. Economizer; 13. Multi-tube dust collector; 14. Desulfurization dry reactor; 15. Baghouse dust collector; 16. Denitrification system; 17. Air preheater; 18. Chimney; 19. Primary air regulating damper. Detailed Implementation

[0037] 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.

[0038] Please see Figures 1-4 A multi-channel steam boiler includes a boiler body 1 with a frame structure. The weight of the boiler body 1 is supported by four support points on the lower headers of the left and right side walls, with the right front support being a fixed point. The other three points allow free horizontal expansion, and the entire boiler is allowed to expand freely upwards. The boiler body 1 includes a boiler drum 2 and a furnace 3. The boiler drum 2 is arranged horizontally, with an inner diameter of 1400mm and a straight section length of 8240mm. The dimensions can be adjusted according to different models. The boiler material is Q245R or Q345R. A manhole is provided at each end of the boiler drum 2 for maintenance. The boiler drum 2 is equipped with a safety valve, pressure gauge, water level gauge, automatic water level control, and exhaust pipe seat. To ensure that the boiler's feedwater quality and steam quality meet the GB / T1576 standard, a wire mesh separator and a steam distribution plate are installed inside the boiler drum 2. A continuous blowdown pipe and a chemical dosing pipe are also installed inside the boiler drum 2.

[0039] The boiler body 1, including its surrounding walls and central partition walls, employs a fully sealed membrane water-cooled wall structure. The membrane water-cooled wall is constructed from Ф60mm×4mm or Ф51mm×4mm tubes (material: 20GB / T3087 or 20GB / T5310) and 5mm×40mm flat steel, welded on both sides using an automated membrane production line, with a pitch of 100mm. The rear wall of the passageway is constructed from Ф60mm×4mm tubes (material: 20GB / T3087) and 5mm×30mm flat steel, welded together, with a pitch of 90mm. Because the boiler features a fully enclosed membrane water-cooled wall structure, the flue gas is completely isolated from the outside environment. Therefore, only a 160mm thick layer of lightweight insulation material is needed to meet the design insulation requirements. The lightweight insulation material is fixed to the outside of the membrane wall using insulation nails welded to the membrane wall fins, along with wire mesh and self-locking pressure plates. Finally, a corrugated sheet furnace lining is applied over the insulation material.

[0040] The furnace 3 is an asymmetrical design, consisting of a combustion chamber and a settling chamber 6. The furnace 3 is 7000mm wide and 4800mm deep, with a volume of 371m³. The dimensions and heating surface of the furnace 3 vary according to the boiler's evaporation rate, ensuring a heating area ≥64m² per ton of steam. The boiler features a front and rear arched furnace structure. A refractory concrete front arch serves as an ignition arch on the lower section of the front wall of the furnace 3, while the rear arch serves as an ignition arch.

[0041] Furthermore, the lower part of the combustion chamber is the main combustion zone 4, and the upper part is the re-combustion zone 5. The main combustion zone 4 is equipped with a 15° inclined reciprocating grate 7, featuring inclined secondary air nozzles 8 and primary air regulating dampers 19. The primary air regulating damper 19 is flexible, facilitating adjustment of grate air intake and primary air distribution. The inclined arrangement of the secondary air nozzles 8 improves combustion. Except for the head of the firebed, the fuel on the reciprocating grate 7 is ignited from both sides. Due to the continuous rakeing and loosening of the fuel layer, the contact area between air and fuel increases, resulting in better fuel adaptability than chain grates. It is particularly advantageous for fuels with strong adhesion, high ash content, and difficulty in ignition. The reciprocating grate 7 has a high degree of mechanization, compact structure, and is convenient to use and maintain. The reciprocating grate 7 consists of a charging hopper 71, a support 72, a movable beam 73, a fixed beam 74, grate bars (movable grate bars 76 and fixed grate bars 77), a front damper, and a transmission system 75. The grate working surface consists of movable grate bars 76 and fixed grate bars 77. The movable grate bars 76 move in the forward and reverse directions of the push beam, so that fuel is transported, burned and discharged on the grate surface. The movement of the movable grate is provided by the transmission system 75, and the fixed grate bars 77 always remain relatively stationary on the fixed beam 74.

[0042] Furthermore, the reciprocating grate 7 employs segmented air supply, with several independent air chambers 78 separated from each other arranged longitudinally along the grate. The primary air entering the air chambers from the bellows or air ducts on both sides of the grate has its velocity reduced by airflow diffusion and is evenly filled into the air chamber. The air intake of each air chamber can be adjusted by an air regulating device. The grate surface and the support 72 are sealed with vertical plates or blocks to prevent fuel from leaking into the air chambers inside the grate.

[0043] Furthermore, the recombustion zone 5 is equipped with slag-forming tubes 9, which can increase flue gas disturbance and promote the burnout rate of the three-stage combustion. After the high-temperature flue gas is turned 90° at the outlet of the furnace 3, it is laterally swept by the three rows of slag-forming tube bundles formed by the water-cooled wall of the rear wall to increase internal circulation. The settling chamber 6 constitutes the burnout zone, which is designed with a cavity to increase the flue gas residence time to >2s. The main combustion zone 4, the recombustion zone 5 and the burnout zone form a three-stage combustion subsystem, which can achieve a carbon burnout rate of >99.5%, improve combustion efficiency and reduce the emission of original pollutants. Combustion process: Fuel enters the main combustion zone 4 of the furnace 3 through the reciprocating grate 7 and is burned. After secondary air supply through the secondary air nozzle 8, the turbulence is increased to improve combustion efficiency. It undergoes secondary combustion in the recombustion zone 5. The slag condensation tube increases the flue gas turbulence and further improves combustion efficiency. The cavity design of the burnout chamber increases the residence time of the flue gas. Finally, three-stage combustion is completed to achieve high-efficiency combustion performance. The exhaust gas temperature is reduced from 170℃ to 140℃. The flue gas generated in the burnout zone enters the flue gas treatment system through the superheater 10, evaporator 11 and economizer 12.

[0044] Superheater 10 adopts a horizontal serpentine tube structure with tube specifications of Ф38mm×3.5mm and material conforming to GB / T3087. The tubes of superheater 10 are arranged in parallel, with a transverse pitch S1=100mm, a longitudinal pitch S2=100mm, a transverse row number Z1=70, a longitudinal row number Z2=14, and a heating area of ​​152.8m². 2 Economizer 12 adopts a horizontal serpentine tube structure with tube specifications of Ф38mm×3.5mm and material of 20GB / T3087. The tubes of economizer 12 are arranged in parallel with a transverse pitch S1=100mm and a longitudinal pitch S2=100mm.

[0045] The flue gas treatment system operates as follows: First, the flue gas passes through a multi-tube dust collector 13 for dust removal. After desulfurization, it undergoes further dust removal through a bag filter 15. Then, it passes through a denitrification system 16 for denitrification, employing a low-temperature denitrification process with a temperature set at 180-240℃. After denitrification, the flue gas temperature is further reduced by an economizer 12 and an air preheater 17, finally being discharged into the atmosphere through a chimney 18. Performing denitrification after dust removal ensures high flue gas cleanliness, effectively avoiding the risk of catalyst poisoning, thus extending its service life and ensuring safe and stable system operation. The air preheater 17 is a tubular air preheater, arranged horizontally in parallel. It is constructed from Φ40mm×1.5mm enamel-lined steel pipes, with 2624 pipes in total. The transverse pitch is 90mm, and the longitudinal pitch is 80mm. Air flows inside the pipes, while flue gas flows outside. Before optimization, the boiler's original NOx emissions were 400 mg / Nm³ and its original dust emissions were 5 g / Nm³. After adopting the three-stage combustion subsystem, the original NOx emissions were 100-150 mg / Nm³ and the original dust emissions were 2 g / Nm³. After treatment by the flue gas treatment system, the final NOx emissions reached 50 mg / Nm³ and the final dust emissions reached 10 mg / Nm³, thus reducing overall pollutant emissions and making environmental protection more compliant.

[0046] Furthermore, the furnace 3 and settling chamber 6 adopt radiant heating surfaces; the superheater 10, economizer 12 and air preheater 17 adopt convective heating surfaces; the evaporator 11 adopts flag-type heating surfaces; and together with the multi-point ash collection in the ash hopper, they form a composite heating surface subsystem. Superheater 10, evaporator 11, economizer 12, and air preheater 17 are convective heating surfaces, each equipped with a convection tube bundle. The convection tube bundle adopts a horizontal serpentine tube and straight tube structure. The serpentine tube specifications are Ф38mm×3.5mm, and the material is 20GB / T3087. The tubes of the convection tube bundle are arranged in parallel, with a transverse pitch S1=90mm and a longitudinal pitch S2=100mm. Evaporator 11 has a total of 3 sets of serpentine tubes. The tube bundle at the inlet section of the heating surface is inclined upward at 10°, which is beneficial for the flushing and carrying of bubbles in the high-load area. The flue dimensions of the reference furnace type are: flue width of 7000mm and depth of 1400mm. Superheater 10, economizer 12, and air preheater 17 are all corrosion-resistant heat transfer surfaces. Superheater 10 is made of high-temperature corrosion resistant ASME material, preferably TP347H. Economizer 12 is made of corrosion-resistant steel, preferably ND steel. Air preheater 17 is made of enamel-lined tubes or corrosion-resistant alloy steel tubes, preferably carbon steel or Corten steel, preferably Q235B. The inner layer of the corrosion-resistant alloy steel tube is carbon steel or Corten steel, the middle layer is rare earth alloy, and the outer layer is a corrosion-resistant sealing agent. Preferably, the inner layer is Q235B. The corrosion-resistant heat transfer surfaces improve the corrosion resistance and reliability of the equipment and extend its service life.

[0047] The boiler is equipped with shock wave soot blowers: 9 in the boiler body 1, 6 in the economizer 12, and 2 in the air preheater 17, for a total of 17 shock wave soot blowers. The boiler is also equipped with a platform and ladder for operation, maintenance, and repair. The platform is 1000mm wide, and the ladder is 800mm wide. The platform and ladder are supported by columns, and the platform has 1100mm high handrails and 100mm high toe boards.

[0048] The performance test data of the present invention and the conventional boiler are shown in Table 1.

[0049] Table 1

[0050] Serial number index Traditional boilers This invention Increase 1 Thermal efficiency 78％ 88％ +10％ 2 NOx raw emissions 400mg / Nm³ 100-150mg / Nm³ -62.5％ 3 Corrosion rate of heated surfaces 0.4mm / y 0.07mm / y -82.5％ 4 Continuous operating cycle 7 days 180 days +2571％

[0051] Compared with traditional boilers, the present invention improves combustion efficiency by 10%, reduces NOx emissions by 62.5%, slows down the corrosion rate of heated surfaces by 82.5%, and increases continuous operating cycles by 2571%. The present invention improves combustion efficiency and environmental performance, and reduces maintenance costs.

[0052] See also Figure 5A control method for a multi-channel steam boiler includes the following steps:

[0053] Step S1: Based on the type of fuel currently being used, obtain the key parameters of the fuel and establish a fuel characteristic database;

[0054] Key parameters include industrial analytical components, elemental composition, and lower heating value. Industrial analytical components include moisture, ash, volatile matter, and fixed carbon. The database is shown in Table 2.

[0055] Table 2

[0056]

[0057] Industrial and elemental analysis of extracted fuels, combined with boiler unit thermodynamic calculation methods, are used to calculate the amount of flue gas produced by the boiler based on evaporator 11, and the data is verified based on specific operating conditions.

[0058] The database contains industrial analysis data for 18 kinds of agricultural and forestry wastes, overcoming the shortcomings of existing equipment in poor adaptability to fuels with moisture content greater than 25% and less than 40% or ash melting point less than 1100℃ (such as rice husks and distiller's grains) and large fluctuations in thermal efficiency, and saving economic costs.

[0059] Step S2: Monitor and assess the boiler's operating status in real time;

[0060] The monitoring and judgment process employs a multi-dimensional sensor network to achieve full coverage of operating conditions. When determining if the boiler load reaches the 30% threshold, the system simultaneously collects the following parameters: ① Furnace 3 temperature field distribution (detected by an infrared thermal imager); ② Flue gas oxygen content (detected by a zirconia sensor with an accuracy of ±0.1%); ③ Steam pressure fluctuations (detected by a piezoelectric sensor with a sampling frequency of 10Hz). When the load reaches the trigger point, the control center completes triple verification within 200ms: load duration ≥ 5min, feeder speed deviation < 3%, and furnace 3 negative pressure stabilized within the range of -50Pa to 50Pa, ensuring the accuracy of the operating condition judgment. Specifically, for fuel characteristics (such as the difference in calorific value between straw and sawdust), the system loads a preset fuel characteristic database for thermodynamic model correction.

[0061] Step S3: Execute real-time control strategies;

[0062] The real-time control strategy includes three-level progressive control. Secondary air volume control adopts a feedforward-feedback composite control. When the secondary air volume is increased by 15% of the baseline value, the following control method is used:

[0063] Feedforward control: Establish an air volume compensation curve based on the fuel calorific value (range of 8MJ / kg-15MJ / kg), and adjust the primary and secondary air ratio to increase the proportion of secondary air.

[0064] Feedback regulation: PID closed-loop regulation is performed based on the flue gas CO concentration (set value < 80ppm, which can be fine-tuned according to actual data during operation);

[0065] Dynamic limiting: The damper opening is adjusted according to the load, and is not less than 50% of the design maximum value; the grate speed control introduces a fuzzy logic algorithm to extend the fuel residence time when the base speed is reduced by 20%;

[0066] Input variables: calorific value, ash content, moisture content;

[0067] Output adjustment: Speed ​​step change ≤2rpm / min, to prevent fuel bed disturbance;

[0068] Safety constraints: Maintain feeding stability at minimum operating speed (≥30% of rated speed).

[0069] The dynamic adjustment of the primary air volume ratio is achieved through online thermogravimetric analysis:

[0070] Establish an air volume distribution matrix: fuel particle size (machine vision recognition) → volatile matter release curve → damper ratio; real-time optimization: update the air volume ratio every 30 seconds, with fluctuation range controlled within ±3%; emergency mode: automatically switch to the preset safe ratio when coking tendency is detected (furnace temperature > 900℃).

[0071] Step S4: Combustion quality target control;

[0072] Combustion quality target control forms a closed-loop optimization system, and the air distribution system adopts staged offset technology.

[0073] Primary air ensures the initial combustion requirements of the fuel, while secondary air is injected in stages (the front and rear air are counter-current to increase disturbance and residence time); the combustion zone creates a uniform temperature field (the temperature difference between the high-temperature zone and the low-temperature zone is <50℃).

[0074] Feed uniformity control includes: synchronous control of mechanical feeder amplitude (5mm-8mm) and grate movement phase; and feedback adjustment of feed rate based on laser detection of fuel bed thickness (resolution of 10mm).

[0075] Self-diagnosis of abnormal operating conditions: When the fuel layer thickness deviation is >20%, a clearing procedure is triggered to disturb the fuel layer and improve the smoothness of feeding.

[0076] Volatile matter emission zone (0.6m-1.5m grate length): maintained at 800℃-900℃; Fixed carbon combustion zone (1.5m-2.5m): secondary air turbulence >20%.

[0077] This invention features a specially designed anti-interference module: when a sudden change in fuel moisture content or calorific value is detected, it automatically activates air temperature compensation (raising the hot air temperature to 120℃-150℃); for different fuel types (such as rice husks and palm husks), the system can call upon 18 pre-stored combustion modes. Operational data shows that this control method increases boiler thermal efficiency to 88%, stabilizes bottom ash carbon content within the range of 5%-7%, and reduces NOx emissions by more than 30%. Through seamless integration with the plant's DCS system via a control demand protocol, it automatically generates combustion optimization reports for each shift, including extended functions such as fuel adaptability analysis and equipment loss assessment.

[0078] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply the existence of any such actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or device comprising the element.

[0079] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A multi-channel steam boiler, characterized in that, include: Boiler body (1): includes boiler drum (2) and furnace (3); the furnace (3) is equipped with combustion chamber and settling chamber (6); the lower part of the combustion chamber is the main combustion zone (4), the upper part is the re-combustion zone (5), the settling chamber (6) constitutes the burnout zone, the main combustion zone (4) is equipped with a reciprocating grate (7) inclined at 15°, and is equipped with inclined secondary air nozzles (8) and primary air regulating damper (19), the re-combustion zone (5) is equipped with slag condensation pipe (9), the burnout zone is a cavity design, the main combustion zone (4), the re-combustion zone (5) and the burnout zone constitute a three-stage combustion subsystem; Corrosion-resistant heating surfaces: The superheater (10) is made of high-temperature corrosion resistant ASME material; the economizer (12) is made of corrosion-resistant steel; The air preheater (17) is made of enamel pipe or corrosion-resistant alloy steel pipe. The enamel pipe is made of carbon steel or Corten steel as the base material. The inner layer of the corrosion-resistant alloy steel pipe is made of carbon steel or Corten steel as the base material, the middle layer is made of rare earth alloy, and the outer layer is made of corrosion-resistant sealing agent. The flue gas generated in the combustion zone enters the flue gas treatment system through the superheater (10), evaporator (11) and economizer (12); the process flow of the flue gas treatment system includes: the flue gas is treated by a multi-tube dust collector (13), a desulfurization dry reactor (14), a bag dust collector (15) and a denitrification system (16), and then enters the economizer (12), air preheater (17), chimney (18), and finally discharged into the atmosphere.

2. The multi-channel steam boiler according to claim 1, characterized in that: It also includes a composite heating surface subsystem, which includes the radiant heating surface used in the furnace (3) and settling chamber (6); the convective heating surface used in the superheater (10), economizer (12) and air preheater (17); the flag-type heating surface used in the evaporator (11); and multi-point ash collection in conjunction with the ash hopper.

3. A multi-channel steam boiler according to claim 1, characterized in that: The boiler drum (2) is arranged horizontally, and the length of the straight section can be adjusted according to the model. There is a manhole on each end cap of the boiler drum (2). The boiler drum (2) is equipped with a wire mesh separator and a steam equalization plate. The boiler body (1) is a front and rear arched covered furnace (3) structure. The boiler body (1) is fully sealed with membrane water-cooled walls around its perimeter and in the middle. The size of the furnace (3) and the heating surface vary according to the boiler evaporation rate.

4. A multi-channel steam boiler according to claim 1, characterized in that: After the high-temperature flue gas turns 90° at the outlet of the furnace (3), it laterally washes the three rows of slag tube bundles formed by the water-cooled wall of the rear wall.

5. A multi-channel steam boiler according to claim 1, characterized in that: The superheater (10), evaporator (11), economizer (12) and air preheater (17) are convective heating surfaces, and each is equipped with a convective tube bundle. The convective tube bundle adopts a horizontal serpentine tube and straight tube structure. The evaporator (11) is arranged with a total of 3 sets of serpentine tubes, and the tube bundle at the inlet section of the heating surface is inclined upward at 10°.

6. A multi-channel steam boiler according to claim 1, characterized in that: The fuel on the reciprocating grate (7) is ignited from both sides except at the head of the fire bed. The reciprocating grate (7) consists of a feeding hopper (71), a support (72), a movable beam (73), a fixed beam (74), a front windbreak door for the grate bars, and a transmission system (75). The grate bars include movable grate bars (76) and fixed grate bars (77). The working surface of the reciprocating grate consists of movable grate bars (76) and fixed grate bars (77). The movable grate bars (76) move in the forward and reverse directions of the pushing beam. The movement of the movable frame is provided by the transmission system (75). The fixed grate bars (77) always remain relatively stationary on the fixed beam (74). The two sides of the reciprocating grate surface are sealed to the support by vertical plates or blocks.

7. A multi-channel steam boiler according to claim 1, characterized in that: The reciprocating grate (7) is equipped with segmented air supply. Several independent air chambers (78) are set along the longitudinal direction of the grate. The primary air entering the air chamber from the air boxes or air ducts on both sides of the grate is reduced in speed by airflow diffusion and is evenly filled into the air chamber. The air intake of each air chamber can be adjusted by the air regulating device.

8. A multi-channel steam boiler according to claim 1, characterized in that: The boiler body (1) is a frame structure. The weight of the boiler body is supported on four support points on the lower headers of the left and right side walls. The right front support is a fixed point, while the other three points allow free expansion in the horizontal direction and allow the boiler body to expand freely upward.

9. A control method for a multi-channel steam boiler according to any one of claims 1-8, characterized in that, Includes the following steps: Step S1: Based on the type of fuel currently being used, obtain the key parameters of the fuel and establish a fuel characteristic database; Key parameters include industrial analytical components, elemental composition, and lower heating value. Industrial analytical components include moisture, ash, volatile matter, and fixed carbon. Step S2: Monitor and assess the boiler's operating status in real time; When the boiler load is detected to be ≥30%, a real-time control strategy is triggered. Step S3: Execute real-time control strategies; Increase the secondary air volume by 15%; reduce the grate speed by at least 20%; dynamically adjust the proportion of primary air volume to total air volume based on the current fuel composition. Step S4: Combustion quality target control; Ensure that the carbon content of the bottom ash is less than 8%.

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