Biomass blending combustion system of coal-fired boiler and blending combustion method

Abstract

The invention relates to the technical field of biomass treatment, in particular to a coal-fired boiler biomass blending combustion system and a blending combustion method. The biomass blending combustion system of the coal-fired boiler comprises a pretreatment device which comprises a sorting mechanism and a drying and tempering mechanism which are connected in sequence; the crushing device comprises a first-stage crushing mechanism, a second-stage crushing mechanism and a third-stage crushing mechanism which are connected in sequence, the first-stage crushing mechanism is suitable for crushing the dried biomass until the particle size is 80-110 mm, the second-stage crushing mechanism is suitable for crushing the biomass subjected to first-stage crushing until the particle size is 17-22 mm, and the third-stage crushing mechanism is suitable for crushing the biomass subjected to second-stage crushing until the particle size is 17-22 mm; the third-stage crushing mechanism is suitable for crushing the biomass subjected to the second-stage crushing until the particle size is 5mm-8mm; and the powder bin is respectively connected with the coal-fired boiler and the three-stage crushing mechanism through pipelines. According to the biomass crushing device, the biomass crushing uniformity is improved, meanwhile, the energy consumption is low, and the blending combustion effect with pulverized coal is better.

Description

Technical Field

[0001] This invention relates to the field of biomass treatment technology, specifically to a biomass co-firing system and method for coal-fired boilers. Background Technology

[0002] Biomass raw materials mainly include various urban and rural organic wastes such as crop straw, livestock farm waste, domestic garbage, and industrial organic wastewater. Biogas, a combustible gas mainly containing methane, is produced from biomass through thermochemical or biochemical conversion. Biogas falls into two main categories: one is gasified gas, produced by incomplete combustion and pyrolysis of biomass under high-temperature, oxygen-deficient conditions, mainly consisting of carbon monoxide, hydrogen, and nitrogen; the other is biogas, produced by the decomposition of biomass by anaerobic bacteria under anaerobic conditions, mainly consisting of methane and carbon dioxide. Biogas, produced through pyrolysis and gasification of biomass, has significant carbon reduction potential in industrial furnaces such as cement kilns, lime kilns, heating furnaces, and boilers, and is currently the lowest-cost fossil fuel alternative. Further synthesis of methanol, aviation kerosene, and hydrogen from biogas for use in shipping, aviation, and land transportation reduces carbon emissions by over 65% compared to traditional fuel oil. However, existing methods of co-firing biomass into coal-fired boilers suffer from uneven biomass pulverization, affecting the co-firing effect. Summary of the Invention

[0003] This invention provides a biomass co-firing system and method for coal-fired boilers, which solves the problem of uneven biomass pulverization affecting the co-firing effect in existing biomass co-firing systems and methods for coal-fired boilers.

[0004] On one hand, the present invention provides a system for co-firing biomass in a coal-fired boiler, comprising:

[0005] The pretreatment device includes a sorting mechanism and a drying and conditioning mechanism connected in sequence. The sorting mechanism is suitable for classifying biomass according to hardness, and the drying and conditioning mechanism is suitable for adjusting the moisture content of the classified biomass until a predetermined moisture content is reached. The pulverizing device includes a primary pulverizing mechanism, a secondary pulverizing mechanism and a tertiary pulverizing mechanism connected in sequence. The primary pulverizing mechanism is suitable for pulverizing the dried biomass to a particle size of 80mm-110mm, the secondary pulverizing mechanism is suitable for pulverizing the biomass after primary pulverization to a particle size of 17mm-22mm, and the tertiary pulverizing mechanism is suitable for pulverizing the biomass after secondary pulverization to a particle size of 5mm-8mm. The powder silo is connected to the coal-fired boiler and the three-stage crushing mechanism via pipelines.

[0006] Beneficial effects: Biomass undergoes sequential sorting, drying and conditioning, primary grinding, secondary grinding, and tertiary grinding before being transported to a coal-fired boiler via a powder silo for mixing with pulverized coal and combustion. Because the biomass is pre-sorted according to hardness, it can be ground to different degrees based on its hardness, avoiding incomplete grinding of hard raw materials due to excessively large particle sizes. Then, it is dried or conditioned according to its moisture content, preventing adhesion and blockage caused by excessive moisture content or excessive dust caused by excessive moisture content, thus initially ensuring the uniformity of grinding. Further tertiary grinding further ensures uniformity, while also resulting in lower energy consumption and better co-firing with pulverized coal.

[0007] In one alternative embodiment, the drying and conditioning mechanism includes a drum dryer and a steam conditioner, wherein the drum dryer is suitable for drying biomass with high moisture content, and the steam conditioner is suitable for steam conditioning biomass with low moisture content.

[0008] A rotary drum dryer is used to dry biomass with high moisture content, resulting in uniform and efficient drying. A steam conditioner is used to moderately humidify biomass with low moisture content to improve its toughness, reducing dust and pollution during the crushing process. The combined effect of these two methods narrows the gap in physical properties between different raw materials and initially improves the uniformity of subsequent crushing.

[0009] In one alternative embodiment, a buffer mechanism is provided between the primary crushing mechanism and the secondary crushing mechanism.

[0010] The buffer mechanism ensures that the pulverized biomass can be stably conveyed to the next stage, guaranteeing the continuous and efficient operation of the pulverizing device and further improving the uniformity of pulverization.

[0011] In one alternative embodiment, a cyclone separator and a dust collector are sequentially arranged between the three-stage crushing mechanism and the powder silo.

[0012] The installation of cyclone separators and dust collectors can efficiently separate the pulverized biomass from other impurities, minimizing dust pollution.

[0013] In one alternative implementation, the discharge port of the powder silo is equipped with a blower, which is connected to the material inlet of the coal-fired boiler.

[0014] The crushed material is transported to the coal-fired boiler by a blower, ensuring conveying efficiency and reducing material waste.

[0015] In one alternative embodiment, the blower is a Roots blower, and the rotor surface of the Roots blower is provided with a hydrophobic coating.

[0016] Roots blowers use stable airflow to suspend and flow biomass powder, which can meet the needs of long-distance transportation while avoiding blockage inside the pipeline. The hydrophobic coating on the rotor surface further reduces the adhesion between the powder and the rotor, preventing powder from clumping and improving transportation efficiency.

[0017] In one alternative implementation, a weighing device is provided at the material inlet of the coal-fired boiler.

[0018] The weighing device ensures the accuracy of the biomass powder entering the coal-fired boiler, thus guaranteeing combustion efficiency.

[0019] In one alternative implementation, the weighing device is a rotor scale.

[0020] Rotary scales are highly accurate, stable, and have strong anti-interference capabilities. They are suitable for a wide range of materials, are not prone to clogging, and are more convenient to use.

[0021] In one alternative implementation, a coal mill is provided at the material inlet of the coal-fired boiler.

[0022] The raw coal is thoroughly ground by a coal mill, resulting in more uniform particle size and higher combustion efficiency when mixed with biomass powder.

[0023] On the other hand, a method for co-firing biomass using a coal-fired boiler system is also provided, including the following steps: Biomass is sequentially sorted, dried and conditioned, then crushed in three stages (primary, secondary, and tertiary) before being transported to a coal-fired boiler via a powder silo, where it is mixed with pulverized coal and then burned.

[0024] Beneficial effects: Biomass undergoes sequential sorting, drying and conditioning, primary grinding, secondary grinding, and tertiary grinding before being transported to a coal-fired boiler via a powder silo for mixing with pulverized coal and combustion. Because the biomass is pre-sorted according to hardness, it can be ground to different degrees based on its hardness, avoiding incomplete grinding of hard raw materials due to excessively large particle sizes. Then, it is dried or conditioned according to its moisture content, preventing adhesion and blockage caused by excessive moisture content or excessive dust caused by excessive moisture content, thus initially ensuring the uniformity of grinding. Further tertiary grinding further ensures uniformity, while also resulting in lower energy consumption and better co-firing with pulverized coal. Attached Figure Description

[0025] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of a biomass co-firing system in a coal-fired boiler according to an embodiment of the present invention.

[0027] Explanation of reference numerals in the attached figures: 1. Pretreatment device; 101. Sorting mechanism; 102. Drying and conditioning mechanism; 2. Crushing device; 201. Primary crushing mechanism; 202. Secondary crushing mechanism; 203. Tertiary crushing mechanism; 3. Powder silo; 4. Coal-fired boiler; 5. Dry material shed; 6. Buffer mechanism; 7. Cyclone separator; 8. Dust collector; 9. Fan; 10. Weighing device; 11. Coal mill; 12. Burner. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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, 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.

[0029] The following is combined Figure 1 Embodiments of the present invention are described.

[0030] According to an embodiment of the present invention, a biomass co-firing system for a coal-fired boiler is provided, comprising: The pretreatment device 1 includes a sorting mechanism 101 and a drying and conditioning mechanism 102 connected in sequence. The sorting mechanism 101 is adapted to classify biomass according to hardness, and the drying and conditioning mechanism 102 is adapted to adjust the moisture content of the classified biomass until a predetermined moisture content is reached. The pulverizing device 2 includes a primary pulverizing mechanism 201, a secondary pulverizing mechanism 202, and a tertiary pulverizing mechanism 203 connected in sequence. The primary pulverizing mechanism 201 is adapted to pulverize the dried biomass to a particle size of 80mm-110mm, the secondary pulverizing mechanism 202 is adapted to pulverize the biomass after primary pulverization to a particle size of 17mm-22mm, and the tertiary pulverizing mechanism 203 is adapted to pulverize the biomass after secondary pulverization to a particle size of 5mm-8mm. The powder hopper 3 is connected to the coal-fired boiler 4 and the three-stage crushing mechanism 203 via pipelines.

[0031] The biomass raw materials in this embodiment include various types, such as wheat straw, rice straw, sawdust, and cotton stalks. Wheat straw and rice straw have lower hardness, while sawdust and cotton stalks have higher hardness. Wheat straw, rice straw, and cotton stalks can be bundled and transported to the drying shed 5. In the drying shed 5, they are sorted by the sorting mechanism 101 and stored separately. The optimal moisture content for grinding different biomass varies, with straw requiring 18%-22% and sawdust requiring 10%-15%. Different drying and conditioning mechanisms 102 can be used for different biomass according to their optimal moisture content until the optimal grinding moisture content is achieved. The primary grinding mechanism 201, secondary grinding mechanism 202, and tertiary grinding mechanism 203 are connected in series. Different types of grinders can be selected according to actual needs, such as jaw grinders, shear grinders, ring die grinders, and graded hammer mills, etc., without specific limitations. Since smaller particle size is not always better for biomass pulverization, and pulverizing to a particle size of 1mm requires extremely high energy consumption, this embodiment limits the particle size of each pulverizing stage. Through step-by-step pulverization, the predetermined particle size is achieved while ensuring the uniformity of pulverization. The powder bin 3 is used to temporarily store the pulverized biomass. It can be designed with a conical bottom for easy material feeding. The powder bin 3 can also be a cuboid, cylinder, etc., and no specific limitation is made here.

[0032] Beneficial effects: After being sorted, dried and conditioned, and then subjected to primary, secondary, and tertiary grinding, the biomass is conveyed to the coal-fired boiler via silo 3 and mixed with pulverized coal for combustion. Because the biomass is pre-sorted according to hardness, it can be ground to different degrees based on its hardness, avoiding incomplete grinding of hard raw materials due to excessively large particle sizes. Then, it is dried or conditioned according to its moisture content, preventing adhesion and blockage caused by excessive moisture content or excessive dust caused by excessive moisture content, thus initially ensuring the uniformity of grinding. Further tertiary grinding further ensures uniformity, while also resulting in lower energy consumption and better co-firing with pulverized coal.

[0033] In one embodiment, the drying and conditioning mechanism 102 includes a drum dryer and a steam conditioner. The drum dryer is suitable for drying biomass with high moisture content, and the steam conditioner is suitable for steam conditioning biomass with low moisture content.

[0034] Both the rotary drum dryer and the steam conditioner are located in the dry material shed 5. One or more units can be set up according to actual needs. The rotary drum dryer and the steam conditioner can be placed on the side or in a row. No specific restrictions are made here.

[0035] A rotary drum dryer is used to dry biomass with high moisture content, resulting in uniform and efficient drying. A steam conditioner is used to moderately humidify biomass with low moisture content to improve its toughness, reducing dust and pollution during the crushing process. The combined effect of these two methods narrows the gap in physical properties between different raw materials and initially improves the uniformity of subsequent crushing.

[0036] In one embodiment, a buffer mechanism 6 is provided between the primary crushing mechanism 201 and the secondary crushing mechanism 202.

[0037] The buffer mechanism 6 can be a buffer tank. The core of multi-stage crushing is coarse crushing for volume reduction and fine crushing for quality improvement. Coarse crushing equipment, such as the primary crushing mechanism 201, is characterized by a large processing capacity and a large feed / discharge volume per unit time, but the output particle size is relatively coarse. Fine crushing equipment, such as the secondary crushing mechanism 202, is characterized by a relatively small processing capacity and high requirements for feed stability, but the output particle size is fine. If the two stages are directly and rigidly connected, the instantaneous output of the coarse crusher can easily exceed the maximum processing load of the fine crusher, leading to material blockage. Conversely, if the coarse crusher temporarily shuts down due to a malfunction, the fine crusher will run idle due to material shortage, resulting in energy waste and equipment wear. The buffer tank acts as a "material reservoir": when the coarse crusher's capacity is greater than the fine crusher's capacity, excess material is temporarily stored in the buffer tank; when the coarse crusher's capacity is less than the fine crusher's capacity, the buffer tank replenishes material, ensuring the fine crusher continues to operate at full load, achieving a process effect of fluctuating upstream and stable downstream.

[0038] The buffer mechanism 6 ensures that the crushed biomass can be stably conveyed to the next stage, ensuring the continuous and efficient operation of the crushing device 2 and further improving the uniformity of crushing.

[0039] In one embodiment, a cyclone separator 7 and a dust collector 8 are sequentially provided between the three-stage crushing mechanism 203 and the powder hopper 3.

[0040] The cyclone separator 7 can efficiently separate the crushed biomass from other impurities and collect them through the dust collector 8, minimizing dust pollution.

[0041] In one embodiment, the discharge port of the powder silo 3 is equipped with a blower 9, which is connected to the material inlet of the coal-fired boiler 4.

[0042] The material in the powder silo 3 can automatically enter the coal-fired boiler 4 under gravity. However, this requires the outlet of the powder silo 3 to be positioned higher than the material inlet of the coal-fired boiler 4, and the connecting pipeline between the two to be inclined, which places high demands on the installation work. Therefore, this application adopts a scheme of installing a blower 9 between the outlet of the powder silo 3 and the material inlet of the coal-fired boiler 4, which reduces the difficulty of equipment installation. The crushed material is conveyed to the coal-fired boiler 4 under the action of the blower 9, ensuring conveying efficiency and reducing material waste.

[0043] In one embodiment, the blower 9 is a Roots blower, and the rotor surface of the Roots blower is provided with a hydrophobic coating.

[0044] Roots blowers use stable airflow to suspend and flow biomass powder, which can meet the needs of long-distance transportation while avoiding blockage inside the pipeline. The hydrophobic coating can be Teflon coating, nano-ceramic coating, etc. The surface tension of the coating is extremely low. The hydrophobic coating on the rotor surface further reduces the adhesion between the powder and the rotor, avoids powder agglomeration and adhesion, and improves the transportation efficiency.

[0045] In one embodiment, a weighing device 10 is provided at the material inlet of the coal-fired boiler 4.

[0046] The weighing device 10 ensures the accuracy of the biomass powder entering the coal-fired boiler 4, thus ensuring combustion efficiency.

[0047] In one embodiment, the weighing device 10 is a rotor scale.

[0048] The rotor scale features high precision, strong stability, strong anti-interference ability, a wide range of applicable materials, is less prone to material blockage, and is more convenient to use. Of course, the weighing device 10 can also be other electronic scales, such as balances, etc., without specific limitations.

[0049] In one embodiment, a coal mill 11 is provided at the material inlet of the coal-fired boiler 4.

[0050] The raw coal is thoroughly ground by the coal mill 11, resulting in more uniform particle size and higher combustion efficiency after mixing with biomass powder. A burner 12 can also be installed at the material inlet of the coal-fired boiler 4 to ignite the coal powder conveyed by the coal mill 11 and the biomass powder conveyed by the powder silo 3 before feeding it into the coal-fired boiler 4.

[0051] On the other hand, a method for co-firing biomass using a coal-fired boiler system is also provided, including the following steps: After being sorted, dried and conditioned, and then crushed in three stages (primary, secondary, and tertiary), the biomass is transported to the coal-fired boiler via silo 3, where it is mixed with pulverized coal and then burned.

[0052] Beneficial effects: After being sorted, dried and conditioned, and then subjected to primary, secondary, and tertiary grinding, the biomass is conveyed to the coal-fired boiler via silo 3 and mixed with pulverized coal for combustion. Because the biomass is pre-sorted according to hardness, it can be ground to different degrees based on its hardness, avoiding incomplete grinding of hard raw materials due to excessively large particle sizes. Then, it is dried or conditioned according to its moisture content, preventing adhesion and blockage caused by excessive moisture content or excessive dust caused by excessive moisture content, thus initially ensuring the uniformity of grinding. Further tertiary grinding further ensures uniformity, while also resulting in lower energy consumption and better co-firing with pulverized coal.

[0053] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and all such modifications and variations fall within the scope defined by the appended claims.

Claims

1. A biomass co-firing system for a coal-fired boiler, characterized in that, include: The pretreatment device (1) includes a sorting mechanism (101) and a drying and conditioning mechanism (102) connected in sequence. The sorting mechanism (101) is adapted to classify biomass according to hardness, and the drying and conditioning mechanism (102) is adapted to adjust the moisture content of the classified biomass until a predetermined moisture content is reached. The pulverizing device (2) includes a primary pulverizing mechanism (201), a secondary pulverizing mechanism (202) and a tertiary pulverizing mechanism (203) connected in sequence. The primary pulverizing mechanism (201) is adapted to pulverize the dried biomass to a particle size of 80mm-110mm. The secondary pulverizing mechanism (202) is adapted to pulverize the biomass after primary pulverization to a particle size of 17mm-22mm. The tertiary pulverizing mechanism (203) is adapted to pulverize the biomass after secondary pulverization to a particle size of 5mm-8mm. The powder hopper (3) is connected to the coal-fired boiler (4) and the three-stage crushing mechanism (203) respectively through pipelines.

2. The biomass co-firing system for a coal-fired boiler according to claim 1, characterized in that, The drying and conditioning mechanism (102) includes a drum dryer and a steam conditioner. The drum dryer is suitable for drying biomass with high moisture content, and the steam conditioner is suitable for steam conditioning biomass with low moisture content.

3. The biomass co-firing system for a coal-fired boiler according to claim 1, characterized in that, A buffer mechanism (6) is provided between the primary crushing mechanism (201) and the secondary crushing mechanism (202).

4. The biomass co-firing system for a coal-fired boiler according to claim 3, characterized in that, A cyclone separator (7) and a dust collector (8) are sequentially provided between the three-stage crushing mechanism (203) and the powder hopper (3).

5. The biomass co-firing system for a coal-fired boiler according to claim 4, characterized in that, The discharge port of the powder silo (3) is equipped with a blower (9), which is connected to the material inlet of the coal-fired boiler (4).

6. The biomass co-firing system for a coal-fired boiler according to claim 5, characterized in that, The blower (9) is a Roots blower, and the rotor surface of the Roots blower is provided with a hydrophobic coating.

7. The biomass co-firing system for a coal-fired boiler according to any one of claims 1 to 6, characterized in that, The coal-fired boiler (4) is equipped with a weighing device (10) at the material inlet.

8. The biomass co-firing system for a coal-fired boiler according to claim 7, characterized in that, The weighing device (10) is a rotor scale.

9. The biomass co-firing system for a coal-fired boiler according to any one of claims 1 to 6, characterized in that, The coal-fired boiler (4) is equipped with a coal mill (11) at the material inlet.

10. A method for co-firing biomass using a coal-fired boiler co-firing system according to any one of claims 1 to 9, characterized in that, Includes the following steps: After being sorted, dried and conditioned, crushed in three stages (first, second, and third stages), the biomass is transported to the coal-fired boiler (4) through the powder silo (3) and mixed with pulverized coal for combustion.

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