Multi-channel steam boiler and control method

Abstract

The invention relates to the technical field of steam boilers, in particular to a multi-channel steam boiler and a control method. A combustion chamber and a settling chamber are arranged in the hearth; the lower part of the combustion chamber is a main combustion area, the upper part of the combustion chamber is a recombustion area, the settling chamber forms a burnout area, and the main combustion area, the recombustion area and the burnout area form a three-stage combustion subsystem; according to the invention, the carbon burnout rate gt can be realized through the three-stage combustion subsystem; according to the invention, the combustion efficiency is improved, the final emission of NOx is reduced to 50 mg / Nm through a flue gas treatment system, the emission of pollutants is reduced, the fuel adaptability is expanded to 18 types of forestry and agricultural residues, the operation state of the boiler is monitored and regulated in real time through an intelligent combustion control method, and the combustion quality is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of steam boilers, and in particular to a multi-channel steam boiler and a control method thereof. Background Art

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

[0003] After searching, it was found that Chinese patent literature discloses a double steam boiler (application number: CN109556102B), which includes a first boiler, a second boiler, a water storage tank and a burner. It fully utilizes the waste heat of the combustion energy in the first boiler, improves the thermal efficiency of the boiler, and reduces the fuel consumption in the combustion chamber and the exhaust gas temperature.

[0004] However, its combustion chamber is designed as a single space, 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 furnace is (3 / 4-4 / 5):1, which easily forms local high-temperature areas and promotes the generation of thermal NOx. NOx emissions are completely dependent on the passive reduction of combustion temperature, with poor environmental compliance and inability to expand fuel adaptability. Alkali metals such as K / Na in the fuel can easily lead to poor equipment reliability and a rapid high-temperature corrosion rate. At the same time, it only uses water level sensors and float valves to achieve water level safety control, and cannot monitor and regulate key parameters of the combustion process (such as air volume, furnace temperature, and fuel characteristics). Summary of the Invention

[0005] The object of the present 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 the characteristics of various fuels.

[0006] To achieve the above objectives, the present invention provides the following technical solutions: a multi-channel steam boiler comprising a boiler body, the boiler body comprising a drum and a furnace; a combustion chamber and a settling chamber disposed within the furnace; the lower portion of the combustion chamber serving as a primary combustion zone, the upper portion serving as a reburning zone, and the settling chamber constituting a burnout zone; a reciprocating grate inclined at 15°, equipped with inclined secondary air nozzles and a primary air damper, a slag condensing pipe disposed within the reburning zone, and a hollow burnout zone; the primary combustion zone, the reburning zone, and the burnout zone forming a three-stage combustion subsystem;

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

[0008] Preferably, 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, chimney, and finally discharged into the atmosphere.

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

[0010] Preferably, the boiler drum is arranged horizontally, the length of the straight section can be adjusted according to the model, a manhole is opened on each end head of the boiler drum, and a wire mesh separator and a steam uniforming hole plate are provided inside the boiler drum; the boiler body is a front and rear arch covered furnace structure, and the four sides of the boiler body and the middle partition wall adopt a membrane water-cooled wall fully sealed structure. The size of the furnace and the heating surface vary according to the size of the boiler evaporation capacity.

[0011] Preferably, the high-temperature flue gas turns 90 degrees at the furnace outlet and laterally flushes the three rows of slag-condensing tube bundles formed by the rear wall water-cooled wall.

[0012] Preferably, the superheater, evaporator, economizer and air preheater are convection heating surfaces, and are all provided with convection tube bundles inside. The convection tube bundles adopt horizontal serpentine tubes and straight tube structures. The evaporator is arranged with a total of 3 groups of serpentine tubes, and the tube bundles at the inlet section of the heating surface are inclined upward by 10°.

[0013] Preferably, the ignition of the fuel on the reciprocating grate is double-sided ignition except for the head of the fire bed. The reciprocating grate is composed of a feeding hopper, a bracket, a movable beam, a fixed beam, a grate plate front damper and a transmission system. The grate plates include movable grate plates and fixed grate plates. The working surface of the reciprocating grate is composed of movable grate plates and fixed grate plates. The movable grate plates move in the positive and negative directions of the pushing beam. The movement of the movable frame is provided by the transmission system. The fixed grate plates always remain relatively stationary on the fixed beam. The two sides of the reciprocating grate surface and the bracket are sealed with vertical plates or blocks.

[0014] Preferably, segmented air supply is adopted inside the reciprocating grate, and a number of independent air chambers separated from each other are arranged along the longitudinal direction of the grate. The primary air entering the air chamber from the bellows or air ducts on both sides of the grate has its speed reduced by air flow 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 supporting points on the left and right side wall lower headers, of which the right front support is a fixed point, and the remaining 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 comprises the following steps:

[0017] Step S1: According to the type of fuel currently input, key parameters of the fuel are obtained and a fuel characteristic database is established;

[0018] Key parameters include industrial analysis composition, elemental composition and lower calorific value. Industrial analysis composition is moisture, ash, volatile matter, fixed carbon;

[0019] Step S2: monitor and judge the operating status of the boiler in real time;

[0020] When the boiler load is monitored to be ≥30%, the real-time control strategy is triggered; the judgment basis is: the proportion of rated evaporation capacity, and the calculation data comes from the value of the main steam outlet flow meter;

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

[0022] Increase the secondary air volume by 15% compared to the original level; reduce the grate speed by at least 20% compared to the original level; dynamically adjust the primary air volume to the total air volume ratio based on the current fuel composition. Implement graded air distribution, multi-stage combustion, add regulating valves to the secondary air main pipe, arrange the secondary air nozzles downward, and stagger the front and rear walls to increase disturbance and penetration.

[0023] Step S4: combustion quality target control;

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

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

[0026] 1. The present invention comprises a three-stage combustion subsystem consisting of a main combustion zone, a reburning zone and a burnout zone. The main combustion zone is provided with a reciprocating grate inclined at 15°, equipped with an inclined secondary air nozzle and a primary air damper. A slag condensation pipe is provided in the reburning zone to increase internal circulation. The primary air damper is flexible and convenient for adjusting the grate air intake and primary air distribution. The inclined arrangement of the secondary air can improve combustion. The arrangement of the slag condensation pipe increases flue gas disturbance and promotes the burnout rate of the three-stage combustion. The burnout zone is designed as a cavity, which can increase the flue gas residence time by more than 2s. The three-stage combustion subsystem can achieve a carbon burnout rate of more than 99.5%, and the original NOx emission is reduced from the original 400mg / Nm³ to 100-150mg / Nm³, thereby improving combustion efficiency.

[0027] 2. In the flue gas treatment system of the present invention, the flue gas passes through a multi-tube dust collector, a desulfurization dry reactor, a bag filter and a denitrification system, and then enters an economizer, an air preheater, a chimney and is discharged into the atmosphere. The final NOx emission is reduced to 50mg / Nm³, thereby 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 the service life of the equipment.

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

[0030] 5. The present invention uses an intelligent combustion control method to monitor and regulate the boiler operating status in real time, ensuring combustion quality, realizing automated combustion control, and reducing labor costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a structural schematic diagram of the boiler body in the present invention;

[0032] Figure 2 Schematic diagram of the structure of the overall system of the present invention;

[0033] Figure 3 It is a structural schematic diagram of the reciprocating grate in the present invention;

[0034] Figure 4 For the present invention Figure 1 A local enlarged schematic diagram of point A;

[0035] Figure 5 This is a flow chart of the control method in the present invention.

[0036] In the figure: 1. Boiler body; 2. Boiler drum; 3. Furnace; 4. Main combustion zone; 5. Reburning zone; 6. Settling chamber; 7. Reciprocating grate; 71. Charging hopper; 72. Bracket; 73. Movable beam; 74. Fixed beam; 75. Transmission system; 76. Movable grate; 77. Fixed grate; 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. Bag dust collector; 16. Denitrification system; 17. Air preheater; 18. Chimney; 19. Primary air damper. DETAILED DESCRIPTION

[0037] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0038] See also Figure 1-Figure 4 A multi-channel steam boiler comprises a boiler body 1. The boiler has a frame structure, with the weight of the boiler body 1 supported by four support points on the left and right sidewall lower headers. The right front support is a fixed point, while the remaining three points allow for free horizontal expansion. The entire boiler is also allowed to expand freely upward. The boiler body 1 comprises a drum 2 and a furnace 3. The drum 2 is arranged horizontally, with an inner diameter of 1400 mm and a straight section length of 8240 mm. This dimension can be adjusted to suit different models, and the boiler is made of Q245R or Q345R. A manhole is provided on each end of the drum 2 for maintenance. The drum 2 is equipped with a safety valve, a pressure gauge, a water level gauge, an automatic water level control, and an exhaust pipe seat. To ensure that the boiler's feed water and steam quality meet the GB / T1576 standard, a wire mesh separator and a steam-leveling orifice plate are installed inside the drum 2. A continuous sewage pipe and a dosing pipe are also provided inside the drum 2.

[0039] The boiler body 1 utilizes a fully sealed membrane water-cooled wall structure on all sides and in the middle of the partition wall. The membrane water-cooled wall is constructed by double-sided welding of Ø60mm×4mm or Ø51mm×4mm tubes (material: 20GB / T3087 or 20GB / T5310) and 5mm×40mm flat steel using an automated membrane production line, with a pitch of 100mm. The rear channel wall is welded from Ø60mm×4mm tubes (material: 20GB / T3087) and 5mm×30mm flat steel, with a pitch of 90mm. Because the boiler features a fully enclosed membrane water-cooled wall structure, flue gases are completely isolated from the outside world. Therefore, only a 160mm thick layer of lightweight insulation material is required to meet the design insulation requirements. This lightweight insulation is secured to the membrane wall using insulation pins welded to the membrane wall fins, along with steel mesh and self-locking pressure plates. Finally, the insulation is covered with a corrugated sheet furnace lining.

[0040] Furnace 3 is an asymmetrical design, consisting of a combustion chamber and a settling chamber 6. It is 7,000 mm wide and 4,800 mm deep, with a capacity of 371 m³. The dimensions and heating surface of furnace 3 vary according to the boiler's evaporation capacity, ensuring a heating area of ​​≥64 m² per ton of steam. The boiler features a front and rear arch-covered furnace structure. A refractory concrete front arch serves as the ignition arch, while a rear arch serves as the pilot arch, built in the lower section of the front wall of furnace 3.

[0041] Furthermore, the lower portion of the combustion chamber serves as the primary combustion zone 4, while the upper portion serves as the reburning zone 5. Within the primary combustion zone 4, a reciprocating grate 7 is installed, tilted at 15°. It is equipped with tilted secondary air nozzles 8 and a primary air damper 19. The primary air damper 19 is flexible, facilitating adjustment of grate air intake and primary air distribution. The tilted arrangement of the secondary air nozzles 8 improves combustion. Fuel ignition on the reciprocating grate 7 is dual-sided, except at the head of the fire bed. Because the fuel layer is constantly raked and loosened, the contact surface between air and fuel increases, resulting in better fuel adaptability than a chain grate. This is particularly effective for fuels with strong adhesion, high ash content, and difficulty in igniting. The reciprocating grate 7 features a high degree of mechanization, a compact structure, and is easy to use and maintain. The reciprocating grate 7 consists of a hopper 71, a bracket 72, a movable beam 73, a fixed beam 74, grate plates (movable grate plate 76 and fixed grate plate 77), a front damper, and a transmission system 75. The grate working surface consists of movable grate plates 76 and fixed grate plates 77. The movable grate plates 76 move in the forward and reverse directions of the propulsion beam, allowing fuel to be transported and burned on the grate surface and for slag to be discharged. The movement of the movable frame is provided by the transmission system 75, while the fixed grate plates 77 remain relatively stationary on the fixed beam 74.

[0042] Furthermore, the reciprocating grate 7 employs segmented air supply. Several independent, mutually separated air chambers 78 are provided along the longitudinal direction of the grate. Primary air entering the air chambers from the bellows or air ducts on either side of the grate is diffused, slowed down, and evenly fills the air chambers. The air volume entering each air chamber can be adjusted using an air control device. The grate surface and brackets 72 are sealed with vertical plates or blocks to prevent fuel from leaking into the air chambers within the grate.

[0043] Furthermore, a slag condensation tube 9 is provided inside the reburning zone 5, which can increase the flue gas disturbance and promote the burnout rate of the three-stage combustion; after the high-temperature flue gas turns 90 degrees at the outlet of the furnace 3, it horizontally flushes the three rows of slag condensation tube bundles formed by the rear wall water-cooled wall to increase internal circulation; the settling chamber 6 constitutes the burnout zone, and the burnout zone is a cavity design, which increases the flue gas residence time by >2s; the main combustion zone 4, the reburning zone 5 and the burnout zone constitute a three-stage combustion subsystem, which can achieve a carbon burnout rate of >99.5%, improve the combustion efficiency, and reduce the emission of original pollutants. Combustion process: The fuel enters the main combustion zone 4 of the furnace 3 through the reciprocating grate 7 for combustion. After secondary air is supplied through the secondary air nozzle 8, disturbance is increased to improve combustion efficiency. Secondary combustion is carried out in the reburning zone 5. The slag condensation pipe increases flue gas disturbance to further improve combustion efficiency. The cavity design of the burnout chamber increases the residence time of the smoke, and finally completes the three-stage combustion to achieve high-efficiency combustion performance. The exhaust temperature is reduced from 170°C to 140°C; the flue gas generated in the burnout zone enters the flue gas treatment system through the superheater 10, evaporator 11 and economizer 12.

[0044] The superheater 10 adopts a horizontal serpentine tube structure, the tube specification is Ф38mm×3.5mm, the material is 20GB / T3087, the superheater 10 tubes are arranged in series, the transverse pitch S1=100mm, the longitudinal pitch S2=100mm, the transverse row number Z1=70, the longitudinal row number Z2=14, and the heating area is 152.8m 2 The economizer 12 adopts a horizontal serpentine tube structure, the tube specification is Ф38mm×3.5mm, the material is 20GB / T3087, the tubes of the economizer 12 are arranged in series, the horizontal pitch S1=100mm, and the longitudinal pitch S2=100mm.

[0045] The flue gas treatment system operates as follows: the flue gas first passes through a multi-tube dust collector 13 for dust removal, then undergoes desulfurization and further dust removal through a bag filter 15. The flue gas then passes through a denitrification system 16 for denitrification. Low-temperature denitrification is used, with a temperature set at 180-240°C. After the denitrification process is complete, the exhaust gas temperature is lowered through an economizer 12 and an air preheater 17, and finally discharged into the atmosphere through a chimney 18. Denitrification treatment is implemented after the dust removal process is complete. The flue gas purified by the catalyst has a high degree of cleanliness, effectively avoiding the risk of catalyst poisoning, thereby extending its service life and ensuring safe and stable operation of the system. The air preheater 17 is a tubular air preheater, arranged horizontally and in series. It is made of 2,624 Φ40mm × 1.5mm enameled steel pipes, with a horizontal pitch of 90mm and a vertical pitch of 80mm. Air flows inside the pipes, while flue gas flows outside. Before optimization, the boiler's original NOx emissions were 400mg / Nm³, and the original dust emissions were 5g / Nm³. After adopting the three-stage combustion subsystem, the boiler's original NOx emissions were 100-150mg / Nm³, and the original dust emissions were 2g / Nm³. After treatment by the flue gas treatment system, the final NOx emissions reached 50mg / Nm³, and the final dust emissions were 10mg / Nm³, which overall reduced pollutant emissions and made environmental protection more compliant.

[0046] Furthermore, the furnace 3 and the settling chamber 6 use radiation heating surfaces; the superheater 10, the economizer 12 and the air preheater 17 use convection heating surfaces; the evaporator 11 uses a flag-type heating surface; and at the same time, the ash hopper is combined with multi-point ash collection to form a composite heating surface subsystem. The superheater 10, evaporator 11, economizer 12 and air preheater 17 are convection heating surfaces, and are all equipped with convection tube bundles. The convection tube bundles adopt horizontal serpentine tubes and straight tube structures. The serpentine tube specifications are Ф38mm×3.5mm, and the material is 20GB / T3087. The tubes of the convection tube bundles are arranged in series with a transverse pitch S1=90mm and a longitudinal pitch S2=100mm. There are three groups of serpentine tubes in total in the evaporator 11. The tube bundles at the inlet section of the heating surface are tilted upward by 10°, which is conducive to the flushing and carrying of bubbles in the high-load area. The flue dimensions of the reference furnace are: the flue width is 7000mm and the depth is 1400mm. The superheater 10, economizer 12 and air preheater 17 are all corrosion-resistant heating surfaces. The superheater 10 is made of corrosion-resistant stainless steel or high-temperature corrosion-resistant ASME material. Preferably, the corrosion-resistant stainless steel is 12Cr1MoVG GB / T5310, and the high-temperature corrosion-resistant ASME material is TP347H; the economizer 12 is made of carbon steel or corrosion-resistant steel. Preferably, the carbon steel is 20GB / T3087, and the corrosion-resistant steel is ND steel; the air preheater 17 is made of Cow-Ten steel or corrosion-resistant steel or enameled tube or corrosion-resistant alloy steel tube. Preferably, the corrosion-resistant steel is ND steel, and the enameled tube is made of base carbon steel or Cow-Ten steel. Preferably, the base carbon steel is Q235B. The inner layer of the corrosion-resistant alloy steel tube is base carbon steel or Cow-Ten steel, the middle layer is rare earth alloy, and the outer layer is corrosion-resistant sealing agent. Preferably, the base carbon steel of the inner layer is Q235B. The corrosion-resistant heating surface improves the corrosion resistance and reliability of the equipment and extends the service life of the equipment.

[0047] The boiler is equipped with shock wave soot blowers: nine in the boiler body 1, six in the economizer 12, and two in the air preheater 17, for a total of 17. A platform ladder is provided for operation, operation, and maintenance. The platform is 1000mm wide and the ladder is 800mm wide. The platform ladder is supported by columns and has 1100mm-high handrails and 100mm-high toeboards.

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

[0049] Table 1 Serial number index Traditional boiler The present invention Improvement 1 Thermal efficiency 78％ 88％ +10％ 2 Original NOx emissions 400mg / Nm³ 100-150mg / Nm³ -62.5％ 3 Heating surface corrosion rate 0.4mm / y 0.07mm / y -82.5％ 4 Continuous operation cycle 7 days 180 days +2571％

[0050] Compared with traditional boilers, the combustion efficiency of the present invention is improved by 10%, the original NOx emissions are reduced by 62.5%, the corrosion rate of the heating surface is slowed down by 82.5%, and the continuous operation cycle is increased by 2571%. The present invention improves combustion efficiency and environmental protection performance and reduces maintenance costs.

[0051] See also Figure 5 , a control method for a multi-channel steam boiler, comprising the following steps:

[0052] Step S1: According to the type of fuel currently input, key parameters of the fuel are obtained and a fuel characteristic database is established;

[0053] Key parameters include industrial analytical composition, elemental composition, and lower heating value. The industrial analytical composition includes moisture, ash, volatile matter, and fixed carbon. The database is established as shown in Table 2.

[0054] Table 2

[0055] The industrial analysis and elemental analysis of the fuel are extracted, and combined with the thermal calculation method of the boiler unit, the amount of flue gas generated by the boiler is calculated according to the evaporator 11, and the data is calculated according to the specific working conditions.

[0056] The database contains industrial analysis data for 18 types of agricultural and forestry wastes, overcoming the shortcomings of existing equipment, such as poor adaptability to fuels with a moisture content greater than 25% and less than 40% or an ash melting point less than 1100°C (such as rice husks and distiller's grains), large fluctuations in thermal efficiency, and saving economic costs.

[0057] Step S2: monitor and judge the operating status of the boiler in real time;

[0058] The monitoring and judgment process utilizes a multi-dimensional sensor network to achieve full operating condition coverage. To determine when the boiler load reaches the 30% threshold, the system simultaneously collects the following parameters: ① Furnace 3 temperature distribution (detected by an infrared thermal imager); ② Flue gas oxygen content (detected by a zirconia sensor with an accuracy of ±0.1%); and ③ Steam pressure fluctuation (detected by a piezoelectric sensor with a sampling frequency of 10Hz). When the load reaches the trigger point, the control center completes a triple check within 200ms: load duration ≥ 5 minutes, feeder speed deviation < 3%, and furnace 3 negative pressure stable within the range of -50Pa to 50Pa, ensuring accurate operating condition judgment. Specifically, the system loads a pre-set fuel property database to modify the thermodynamic model based on fuel characteristics (such as the calorific value difference between straw and sawdust).

[0059] Step S3: Execute real-time control strategy;

[0060] The real-time control strategy includes three-level progressive control. The secondary air volume control adopts feedforward-feedback compound control. When the secondary air volume is increased by 15% of the baseline value, the following control method is adopted:

[0061] Feedforward control: Establish an air volume compensation curve based on the fuel calorific value (8MJ / kg-15MJ / kg range), and adjust the primary and secondary air ratio to increase the proportion of secondary air;

[0062] Feedback regulation: PID closed-loop regulation is performed through the flue gas CO concentration (set value < 80ppm, which can be fine-tuned according to actual data during operation);

[0063] Dynamic limiting: Adjust according to load, the air damper opening should not be less than 50% of the design maximum value; the grate speed control introduces fuzzy logic algorithm to extend the fuel residence time when the base speed is reduced by 20%;

[0064] Input variables: calorific value, ash content, moisture content;

[0065] Output adjustment: speed step change ≤ 2rpm / min to prevent fuel layer disturbance;

[0066] Safety constraint: Minimum speed to maintain feeding stability (≥30% of rated speed).

[0067] Dynamic adjustment of primary air volume ratio is achieved through online thermogravimetric analysis:

[0068] 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, and control the fluctuation range to ±3%; emergency mode: automatically switch to the preset safety ratio when coking tendency is detected (furnace temperature > 900°C).

[0069] Step S4: combustion quality target control;

[0070] The combustion quality target control forms a closed-loop optimization system, and the air distribution system adopts graded hedging technology:

[0071] The primary air ensures the initial combustion requirements of the fuel, and the secondary air is injected in stages (the front and back hedging increases disturbance and increases residence time); the temperature field in the burning area is uniform (the temperature difference between the high temperature area and the low temperature area is less than 50℃).

[0072] Feeding uniformity control includes: mechanical feeder amplitude (5mm-8mm) and grate motion phase synchronization control; fuel layer thickness laser detection (resolution of 10mm) feedback adjustment of feeding amount;

[0073] Self-diagnosis of abnormal working conditions: When the fuel layer thickness deviation is greater than 20%, the clearing program is triggered to perform disturbance and improve the smoothness of feeding;

[0074] Volatile analysis zone (0.6m-1.5m grate length area): maintain 800℃-900℃; fixed carbon combustion zone (1.5m-2.5m): secondary air turbulence >20%.

[0075] This invention features a specially designed anti-interference module: When a sudden change in fuel moisture or calorific value is detected, air temperature compensation is automatically activated (raising the hot air temperature to 120°C-150°C). The system also utilizes 18 pre-stored combustion modes for different fuel types (such as rice husks and palm oil shells). Operational data indicates that this control method has increased boiler thermal efficiency to 88%, stabilized bottom ash carbon content within the 5%-7% range, and reduced NOx emissions by over 30%. Seamless integration with the plant's DCS system via a control demand protocol enables automatic generation of combustion optimization reports for each shift, including extended functions such as fuel compatibility analysis and equipment loss assessment.

[0076] 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.

[0077] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A multi-channel steam boiler, characterized in that: include: Boiler body (1): including a drum (2) and a furnace (3); a combustion chamber and a settling chamber (6) are provided inside the furnace (3); the lower part of the combustion chamber is a main combustion zone (4), the upper part is a reburning zone (5), and the settling chamber (6) constitutes a burnout zone. A reciprocating grate (7) inclined at 15° is provided inside the main combustion zone (4), equipped with an inclined secondary air nozzle (8) and a primary air damper (19), a slag condensing pipe (9) is provided inside the reburning zone (5), and the burnout zone is a cavity design. The main combustion zone (4), the reburning zone (5) and the burnout zone constitute a three-stage combustion subsystem; Corrosion-resistant heating surface: The superheater (10) is made of corrosion-resistant stainless steel or high-temperature corrosion-resistant ASME material; the economizer (12) is made of carbon steel or corrosion-resistant steel; the air preheater (17) is made of Corten steel or corrosion-resistant steel or enameled tube or corrosion-resistant alloy steel tube. The enameled tube is made of carbon steel or Corten steel as the base material. The inner layer of the corrosion-resistant alloy steel tube 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.

2. A multi-channel steam boiler according to claim 1, characterized in that: The flue gas generated in the combustion zone enters the flue gas treatment system through the superheater (10), the evaporator (11) and the economizer (12); the process flow of the flue gas treatment system includes: the flue gas is treated by the multi-tube dust collector (13), the desulfurization dry reactor (14), the bag dust collector (15) and the denitrification system (16), and then enters the economizer (12), the air preheater (17), the chimney (18), and finally discharged into the atmosphere.

3. The multi-channel steam boiler according to claim 1, characterized in that: The system also includes a composite heating surface subsystem, which includes radiation heating surfaces used in the furnace (3) and the settling chamber (6); convection heating surfaces used in the superheater (10), the economizer (12) and the air preheater (17); and a flag-type heating surface used in the evaporator (11); and is combined with an ash hopper for multi-point ash collection.

4. The 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. A manhole is opened on each end head of the boiler drum (2). A wire mesh separator and a steam uniforming plate are arranged inside the boiler drum (2); the boiler body (1) is a front and rear arch covered furnace (3) structure, and the surrounding and middle partition walls of the boiler body (1) are all membrane water-cooled wall fully sealed structures. The size and heating surface of the furnace (3) vary according to the size of the boiler evaporation capacity.

5. The multi-channel steam boiler according to claim 1, characterized in that: After the high-temperature flue gas passes through the furnace (3) outlet and turns 90 degrees, it laterally flushes the three rows of slag-condensing tube bundles formed by the rear wall water-cooled wall.

6. The multi-channel steam boiler according to claim 1, characterized in that: The superheater (10), evaporator (11), economizer (12) and air preheater (17) are convection heating surfaces, and are all provided with convection tube bundles inside. The convection tube bundles adopt a horizontal serpentine tube and straight tube structure. The evaporator (11) is arranged with a total of three groups of serpentine tubes, and the tube bundles at the inlet section of the heating surface are inclined upward by 10 degrees.

7. The multi-channel steam boiler according to claim 1, characterized in that: The ignition of the fuel on the reciprocating grate (7) is double-sided ignition except for the head of the fire bed; the reciprocating grate (7) is composed of a charging hopper (71), a bracket (72), a movable beam (73), a fixed beam (74), a grate plate front damper and a transmission system (75); the grate plate includes a movable grate plate (76) and a fixed grate plate (77); the reciprocating grate working surface is composed of a movable grate plate (76) and a fixed grate plate (77); the movable grate plate (76) moves in the forward and reverse directions of the push beam, the movement of the movable frame is provided by the transmission system (75), and the fixed grate plate (77) always remains relatively stationary on the fixed beam (74); both sides of the reciprocating grate surface and the bracket are sealed by vertical plates or blocks.

8. The multi-channel steam boiler according to claim 1, characterized in that: The reciprocating grate (7) adopts segmented air supply inside, and a plurality of independent air chambers (78) separated from each other are arranged along the longitudinal direction of the grate. The primary air entering the air chamber from the bellows or air ducts on both sides of the grate is reduced in speed by air flow diffusion and evenly fills the air chamber. The air intake of each air chamber can be adjusted by an air regulating device.

9. The multi-channel steam boiler according to claim 1, characterized in that: The boiler body (1) is a frame structure, and the weight of the boiler body is supported on four supporting points on the left and right side wall lower headers, wherein 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.

10. A control method for a multi-channel steam boiler, characterized in that: The following steps are involved: Step S1: According to the type of fuel currently input, key parameters of the fuel are obtained and a fuel characteristic database is established; Key parameters include industrial analysis composition, elemental composition and lower calorific value. Industrial analysis composition is moisture, ash, volatile matter, fixed carbon; Step S2: monitor and judge the operating status of the boiler in real time; When the boiler load is monitored to be ≥30%, the real-time control strategy is triggered; Step S3: Execute real-time control strategy; Increase the secondary air volume by 15% from the original level; reduce the grate speed by at least 20% from the original level; dynamically adjust the proportion of primary air volume to the total air volume based on the current fuel composition; Step S4: combustion quality target control; Ensure that the carbon content of bottom ash is less than 8%.

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