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

Abstract

The invention discloses a coal-fired boiler biomass blending combustion system and a control method thereof, and the coal-fired boiler biomass blending combustion system comprises a combustor with a central air pipe; the biomass treatment equipment is used for crushing biomass to form biomass particles; the biomass storage bin is used for storing biomass particles; and the biomass feeding system communicates with the central air pipe and is used for conveying the biomass particles in the biomass storage bin to the central air pipe. According to the biomass blending combustion system of the coal-fired boiler, the flexibility of biomass blending combustion of the coal-fired boiler can be achieved, the economical efficiency of biomass blending combustion of the coal-fired boiler is improved, and the development cost and the production cost can be reduced.

Description

Technical Field

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

[0002] Biomass co-firing fully utilizes biomass resources such as agricultural and forestry waste, desert plants, and energy plants to reduce carbon emissions from coal-fired power units by coupling biomass power generation with coal-fired power units. Co-firing biomass in coal-fired boilers is one of the main pathways for carbon reduction. It is explicitly stated that coal-fired power units with a biomass co-firing ratio exceeding 10% will not participate in carbon emission quota allocation for the time being; that is, there are currently no regulations on the total carbon composition of coal-fired power units. Both the Low-Carbon Action Plan and the Ministry of Environmental Protection's carbon emission quota allocation plan actively encourage the co-firing of biomass in coal-fired units. However, due to the wide availability and volatile prices of biomass, improper selection of co-firing strategies and methods can seriously affect the economic viability of co-firing biomass in coal-fired boilers. Summary of the Invention

[0003] The present invention aims to at least solve one of the technical problems existing in the prior art. Therefore, one object of the present invention is to provide a coal-fired boiler biomass co-firing system that enables flexibility in biomass co-firing in coal-fired boilers, improves the economic efficiency of biomass co-firing in coal-fired boilers, and reduces development and production costs.

[0004] Another objective of this invention is to provide a control method for a coal-fired boiler system that incorporates biomass.

[0005] According to an embodiment of the present invention, a biomass co-firing system for a coal-fired boiler includes: a burner having a central duct; a biomass processing device for crushing biomass to form biomass pellets; a biomass storage bin for storing the biomass pellets; and a biomass feeding system connected to the central duct for conveying the biomass pellets from the biomass storage bin to the central duct.

[0006] According to an embodiment of the present invention, a biomass co-firing system for a coal-fired boiler utilizes a biomass processing device to crush biomass into biomass pellets. A biomass storage bin stores these pellets, meeting storage requirements and facilitating biomass storage. This system enhances the flexibility and economic efficiency of biomass co-firing in coal-fired boilers. Furthermore, the burner features a central duct, connected to which a biomass feeding system transports biomass pellets from the storage bin to the central duct. This allows for the supply of biomass to the burner, meeting combustion requirements. Since biomass can be supplied to the burner solely through the central duct, redesigning or complexly processing the burner to connect to the biomass feeding system is unnecessary, thus reducing development and production costs.

[0007] In addition, the biomass co-firing system for coal-fired boilers according to the above embodiments of the present invention may also have the following additional technical features: According to some embodiments of the present invention, a coal-fired boiler co-firing biomass system further includes: a first conveying system located between the biomass processing equipment and the biomass storage bin, for conveying the biomass pellets processed by the biomass processing equipment to the biomass storage bin.

[0008] According to some embodiments of the present invention, the particle size of the biomass pellets is less than or equal to 10 cm.

[0009] According to some embodiments of the present invention, the biomass co-firing system of a coal-fired boiler further includes: a biomass pulverizer, which is connected to the biomass storage bin and is used to grind the biomass particles to form biomass powder; and a biomass feeding system is used to transport the biomass powder to the central air duct.

[0010] According to some embodiments of the present invention, the biomass co-firing system of the coal-fired boiler includes: a second conveying system, the second conveying system being located between the biomass storage bin and the biomass pulverizer, for conveying the biomass particles in the biomass storage bin to the biomass pulverizer.

[0011] According to some embodiments of the present invention, the particle size of the biomass powder is less than or equal to 2 mm.

[0012] According to some embodiments of the present invention, there are multiple biomass storage bins, and the multiple biomass storage bins respectively store the biomass pellets; and / or, the burner further has a combustion chamber, and the central air duct passes through the combustion chamber and communicates with the combustion chamber.

[0013] According to some embodiments of the present invention, the central duct has a biomass inlet, which is connected to the biomass feeding system; or, a biomass pipe extending along the length of the central duct is provided inside the central duct, which is connected to both the central duct and the biomass feeding system.

[0014] A control method for a coal-fired boiler biomass co-firing system according to an embodiment of the present invention, wherein the coal-fired boiler biomass co-firing system is the coal-fired boiler biomass co-firing system according to an embodiment of the present invention, the control method comprising: It is determined that the amount of biomass pellets stored in the biomass storage bin is greater than or equal to four-fifths of the total storage capacity of the biomass storage bin; The biomass pellets in the biomass storage bin are conveyed to the biomass feeding system at a first preset conveying rate; It is determined that the amount of biomass pellets stored in the biomass storage bin is less than or equal to three-tenths of the total amount of biomass stored in the biomass storage bin; The biomass pellets in the biomass storage bin are conveyed to the biomass feeding system at a second preset conveying rate, wherein the first preset conveying rate is greater than the second preset conveying rate.

[0015] The control method for a biomass-blended coal-fired boiler system according to embodiments of the present invention utilizes a biomass processing device to crush biomass into biomass pellets, and a biomass storage bin to store the biomass pellets, meeting the storage requirements of the biomass pellets and facilitating biomass storage. This enables flexibility in biomass blending in coal-fired boilers and improves the economic efficiency of biomass blending. Furthermore, the burner has a central duct, and the biomass feeding system is connected to the central duct to transport the biomass pellets from the biomass storage bin to the central duct. This allows for the supply of biomass to the burner, meeting the required combustion needs. Moreover, the supply of biomass to the burner can be achieved solely through the central duct, avoiding the need to redesign the burner or perform complex processing to connect it to the biomass feeding system, thus reducing development and production costs.

[0016] According to some embodiments of the present invention, the coal-fired boiler co-firing biomass system further includes a coal-fired boiler, the coal-fired boiler being connected to the burner, and the control method further includes: The load output of the coal-fired boiler is determined to be less than or equal to 30%. The biomass pellets in the biomass storage bin are transported to the biomass feeding system.

[0017] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0018] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a schematic diagram of a coal-fired boiler co-firing biomass system according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of a burner according to some embodiments of the present invention; Figure 3 This is a schematic diagram of the structure of a burner according to other embodiments of the present invention.

[0019] Figure label: 100. Coal-fired boilers co-firing biomass systems; 10. Burner; 11. Central air duct; 12. Combustion chamber; 111. Biomass inlet; 112. Biomass pipeline; 113. Atmospheric air duct; 114. Atmospheric air volume control valve; 115. Central air control valve; 121. Pulverized coal inlet; 20. Biomass processing equipment; 30. Biomass storage bins; 40. Biomass feeding system; 51. First conveying system; 52. Second conveying system; 60. Biomass milling machine; 70. Coal-fired boiler; 71. Coal mill; 72. Pulverized coal pipeline. Detailed Implementation

[0020] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0021] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0022] In the description of this invention, "first feature" and "second feature" may include one or more of the features, "multiple" means two or more, "above" or "below" the second feature may include the first and second features being in direct contact, or the first and second features being in contact through another feature between them, and "above," "over," and "on top" the second feature may include the first feature being directly above or diagonally above the second feature, or simply indicate that the first feature is at a higher horizontal level than the second feature.

[0023] A biomass co-firing system 100 for a coal-fired boiler according to an embodiment of the present invention is described below with reference to the accompanying drawings.

[0024] Reference Figure 1 and Figure 2 As shown, the biomass co-firing system 100 of a coal-fired boiler according to an embodiment of the present invention may include: a burner 10, a biomass processing device 20, a biomass storage bin 30, and a biomass feeding system 40.

[0025] Specifically, the biomass processing equipment 20 can crush and granulate biomass (such as agricultural and forestry waste, desert plants, energy plants, etc.) to form biomass pellets. The biomass storage bin 30 can store the biomass pellets, meeting the storage requirements and facilitating biomass storage. When the biomass market price decreases, the biomass preparation system produces biomass pellets and stores them in the biomass storage bin 30. These pellets are then blended and burned through the burner 10, for example, in a coal-fired boiler 70 at the maximum blending ratio (approximately 10% of the heat). Excess biomass pellets are stored in the biomass storage bin 30 for later blending. Thus, when biomass market prices are low, the biomass processing equipment 20 can produce more biomass fuel, store more in the biomass storage bin 30, and blend more, increasing the flexibility of biomass blending in the coal-fired boiler 70 and improving its economic efficiency.

[0026] In addition, such as Figure 2As shown, the burner 10 has a central duct 11, and the biomass feeding system 40 is connected to the central duct 11, which enables the connection between the biomass feeding system 40 and the burner 10. The biomass feeding system 40 can transport biomass pellets from the biomass storage bin 30 to the central duct 11, thus providing biomass to the burner 10 for combustion. For example, the biomass pellets can enter the furnace of the coal-fired boiler 70 for combustion, meeting the required combustion needs. Furthermore, biomass can be supplied to the burner 10 solely through the central duct 11, avoiding the need to redesign the burner 10 or perform complex processing to connect it to the biomass feeding system 40, thereby reducing development and production costs. For example, the burner 10 can be a swirl pulverized coal burner 10.

[0027] According to an embodiment of the present invention, the biomass co-firing system 100 for a coal-fired boiler uses a biomass processing device 20 to crush biomass into biomass pellets, and a biomass storage bin 30 to store the biomass pellets, meeting the storage requirements of the biomass pellets and facilitating biomass storage. This enables the flexibility of co-firing biomass in the coal-fired boiler 70 and improves the economic efficiency of co-firing biomass in the coal-fired boiler 70. In addition, the burner 10 has a central air duct 11, and the biomass feeding system 40 is connected to the central air duct 11 to transport the biomass pellets in the biomass storage bin 30 to the central air duct 11. This enables the supply of biomass to the burner 10 to meet the required combustion requirements, and the supply of biomass to the burner 10 can be achieved solely through the central air duct 11, avoiding the need to redesign the burner 10 or perform complex processing on the burner 10 to connect with the biomass feeding system 40, thereby reducing development and production costs.

[0028] In some embodiments of the present invention, such as Figure 1 As shown, the biomass co-firing system 100 in a coal-fired boiler also includes a first conveying system 51. The first conveying system 51 is located between the biomass processing equipment 20 and the biomass storage bin 30. The first conveying system 51 can transport the biomass pellets processed by the biomass processing equipment 20 to the biomass storage bin 30, thereby realizing the transportation of biomass pellets, reducing the time spent on manual operation, adapting to a high-efficiency production rhythm, realizing automated production on the assembly line, which is conducive to improving production efficiency and reducing production costs.

[0029] According to some embodiments of the present invention, the biomass pellets have a particle size of less than or equal to 10 cm, which facilitates the storage of biomass pellets, makes them less prone to explosion or combustion during storage, ensures storage safety, and facilitates subsequent combustion operations. For example, in some specific embodiments, the particle size of the biomass pellets can be 10 cm, 9 cm, 8 cm, 7 cm, 6 cm, 5 cm, etc.

[0030] In some embodiments of the present invention, such as Figure 1 As shown, the biomass co-firing system 100 for coal-fired boilers also includes a biomass pulverizer 60, which is connected to the biomass storage bin 30. The biomass pulverizer 60 can grind biomass pellets into biomass powder. The biomass feeding system 40 can transport the biomass powder to the central air duct 11 to provide biomass to the burner 10. Furthermore, grinding the biomass pellets by the biomass pulverizer 60 can make the biomass smaller, which is easier to burn and avoids problems such as blockage, thus ensuring combustion reliability.

[0031] In some embodiments, such as Figure 2 As shown, the central duct 11 has a biomass inlet 111. The biomass feeding system 40 is connected to the central duct 11 via a pipe, and the biomass feeding system 40 is connected to the biomass inlet 111. The biomass feeding system 40 facilitates the conveying of biomass powder to the central duct 11, resulting in a simple connection structure, easy processing and assembly, and reduced production costs. For example, the direction in which the biomass powder enters the central duct 11 is as follows: Figure 2 As indicated by the middle arrow.

[0032] In some embodiments, the pipes and the central duct 11 are connected by flanges or welding to ensure reliable connection, and the structure is simple, easy to assemble, and can reduce production costs.

[0033] In some embodiments where the biomass pellet diameter is less than or equal to 10 cm, after the biomass pellets enter the biomass mill 60, the biomass pellets with a diameter of less than or equal to 10 cm are easier for the biomass mill 60 to grind, making the grinding more reliable and avoiding damage to the biomass mill 60 caused by larger biomass pellets, which helps to extend the service life of the biomass mill 60.

[0034] According to some embodiments of the present invention, such as Figure 1 As shown, the biomass co-firing system 100 in a coal-fired boiler includes a second conveying system 52, located between the biomass storage bin 30 and the biomass pulverizer 60. The second conveying system 52 transports biomass pellets from the biomass storage bin 30 to the biomass pulverizer 60, reducing manual operation time, adapting to efficient production schedules, and enabling automated production on a streamlined production line. This improves production efficiency and reduces production costs. For example, the second conveying system 52 can be a conveyor belt.

[0035] In some embodiments of the present invention, the particle size of the biomass powder is less than or equal to 2 mm, which makes the biomass powder small, facilitates the combustion of biomass, avoids problems such as clogging, and ensures combustion reliability. For example, in some specific embodiments, the particle size of the biomass powder can be 2 mm, 1.8 mm, 1.5 mm, 1.3 mm, 1.0 mm, 0.8 mm, 0.6 mm, etc.

[0036] According to some embodiments of the present invention, there are multiple biomass storage bins 30 (two or more), and the multiple biomass storage bins 30 store biomass pellets respectively. By using multiple biomass storage bins 30, as many biomass pellets as possible can be stored when the biomass market price is low, which is convenient for subsequent combustion and use. This can realize the flexibility of co-firing biomass in coal-fired boilers 70 and improve the economy of co-firing biomass in coal-fired boilers 70.

[0037] In some embodiments of the present invention, such as Figure 2 As shown, the burner 10 also has a combustion chamber 12, through which pulverized coal can enter and burn to meet the coal combustion requirements of the coal-fired boiler 70. The central air duct 11 passes through the combustion chamber 12 and is connected to the combustion chamber 12, so that biomass can enter the combustion chamber 12 through the central air duct 11 to meet the combustion requirements of biomass and thus meet the carbon reduction requirements.

[0038] In some embodiments, such as Figure 2 As shown, the burner 10 is provided with a pulverized coal inlet 121, which is connected to the combustion chamber 12. Pulverized coal can enter the combustion chamber 12 through the pulverized coal inlet 121, thereby providing pulverized coal into the combustion chamber 12. The structure is simple and easy to control.

[0039] In some embodiments, such as Figure 1 and Figure 2 As shown, the central air duct 11 has a biomass inlet 111, which is connected to the biomass feeding system 40. The biomass feeding system 40 can transport biomass pellets to the central air duct 11 through the biomass inlet 111, which makes the structure simple, easy to assemble, and conducive to reducing production costs.

[0040] In some embodiments, since the ignition temperature of biomass powder is generally low, the central air comes from the boiler's hot secondary air box, with a temperature distribution of 300℃-350℃, while the ignition temperature of biomass powder is usually between 250℃-320℃. In order to ensure that the biomass does not ignite in the central air duct 11 and ignites with the central air belt at the burner 10 nozzle, the temperature of the central air needs to be strictly controlled according to the ignition temperature of the biomass.

[0041] Therefore, as Figure 2As shown, an atmospheric duct 113 is connected to the central duct 11. An atmospheric airflow regulating damper 114 is installed on the atmospheric duct 113, and a central airflow regulating damper 115 is installed on the central duct 11. The central airflow temperature is adjusted to be lower than the biomass ignition temperature by the central airflow regulating damper 115 and the atmospheric airflow regulating damper 114, ensuring the safety of the biomass. For example, when the ignition temperature of the biomass is 280℃ and the central airflow temperature is 330℃, the atmospheric airflow regulating damper 114 is opened, and the central airflow regulating damper 115 is reduced to maintain a constant central airflow. However, after adjustment, the central airflow temperature is 270℃, ensuring that the biomass does not ignite within the central duct 11, thus ensuring safety.

[0042] In some embodiments, the central duct 11 is a copper pipe, which ensures the structural strength of the central duct 11, and the structure is simple, easy to process and manufacture, and can reduce production costs.

[0043] Or, such as Figure 1 and Figure 3 As shown, a biomass pipe 112 is installed inside the central air duct 11. The biomass pipe 112 extends along the length of the central air duct 11 and is connected to the central air duct 11 and the biomass feeding system 40. The biomass feeding system 40 can transport biomass pellets to the central air duct 11 through the biomass pipe 112. The structure is simple and easy to assemble.

[0044] In some embodiments, the biomass pipe 112 is an insulation component, which enables the biomass pipe 112 to isolate the heat conduction between the central air and the biomass in the central air duct 11. Even if the temperature of the central air is higher than the ignition temperature of the biomass, the performance of the insulation component can ensure that the temperature of the biomass fuel is always lower than the temperature of the central air, thus ensuring safety.

[0045] The control method for a coal-fired boiler biomass co-firing system 100 according to an embodiment of the present invention, wherein the coal-fired boiler biomass co-firing system 100 is a coal-fired boiler biomass co-firing system 100 according to an embodiment of the present invention, includes: It is determined that the amount of biomass pellets stored in the biomass storage bin 30 is greater than or equal to four-fifths of the total amount of biomass pellets stored in the biomass storage bin 30. In other words, the amount of biomass pellets stored in the biomass storage bin 30 is relatively large. The biomass pellets in the biomass storage bin 30 are conveyed to the biomass feeding system 40 at a first preset conveying amount. The biomass feeding system 40 can convey the biomass pellets to the central air duct 11 to provide biomass to the burner 10. It is determined that the amount of biomass pellets stored in the biomass storage bin 30 is less than or equal to three-tenths of the total amount of biomass pellets stored in the biomass storage bin 30. In other words, the amount of biomass pellets stored in the biomass storage bin 30 is relatively small. The biomass pellets in the biomass storage bin 30 are conveyed to the biomass feeding system 40 at a second preset conveying amount. The first preset conveying amount is greater than the second preset conveying amount. The biomass feeding system 40 can convey the biomass pellets to the central air duct 11 to provide biomass to the burner 10. However, the amount of biomass pellets conveyed to the biomass feeding system 40 is relatively small, thus providing less biomass to the burner 10.

[0046] Therefore, when biomass market prices decline, the biomass preparation system increases its output to produce biomass pellets, resulting in a larger quantity of biomass pellets stored in the biomass storage bin 30. This allows for the maximum proportion of biomass co-firing in the coal-fired boiler 70, with any excess pellets stored in the biomass storage bin 30 for later co-firing. Conversely, when biomass market prices rise, the biomass preparation system reduces its output to produce biomass pellets, resulting in a smaller quantity of biomass pellets stored in the biomass storage bin 30. This reduces the amount of biomass co-firing in the coal-fired boiler 70, thus enabling the system to produce, co-firing, and store more biomass when prices are low, thereby improving the economic efficiency of biomass co-firing in the coal-fired boiler 70.

[0047] It should be noted that when there are multiple biomass storage bins 30, "the amount of biomass pellets stored in the biomass storage bin 30 is greater than or equal to four-fifths of the total amount of biomass pellets stored in the biomass storage bin 30" means that the total amount of biomass pellets stored in the multiple biomass storage bins 30 is greater than or equal to four-fifths of the total amount of biomass pellets stored in the multiple biomass storage bins 30, or the amount of biomass pellets stored in any one of the biomass storage bins 30 is greater than or equal to four-fifths of the total amount of biomass pellets stored in that biomass storage bin 30; "the amount of biomass pellets stored in the biomass storage bins 30 is less than or equal to three-tenths of the total amount of biomass pellets stored in the multiple biomass storage bins 30" means that the total amount of biomass pellets stored in the multiple biomass storage bins 30 is less than or equal to three-tenths of the total amount of biomass pellets stored in the multiple biomass storage bins 30, or the amount of biomass pellets stored in any one of the biomass storage bins 30 is less than or equal to three-tenths of the total amount of biomass pellets stored in that biomass storage bin 30.

[0048] Since the biomass co-firing system 100 of the coal-fired boiler according to the embodiments of the present invention has the above-mentioned beneficial technical effects, the control method of the biomass co-firing system 100 of the coal-fired boiler according to the embodiments of the present invention uses a biomass processing device 20 to crush biomass into biomass pellets, and a biomass storage bin 30 to store biomass pellets, meeting the storage requirements of biomass pellets, facilitating biomass storage, enabling the flexibility of biomass co-firing in the coal-fired boiler 70, and improving the economy of biomass co-firing in the coal-fired boiler 70. In addition, the burner 10 has a central air duct 11, and the biomass feeding system 40 is connected to the central air duct 11 to transport the biomass pellets in the biomass storage bin 30 to the central air duct 11, enabling the supply of biomass to the burner 10 to meet the required combustion requirements, and the supply of biomass to the burner 10 can be achieved solely through the central air duct 11, avoiding the need to redesign the burner 10 or perform complex processing on the burner 10 to connect with the biomass feeding system 40, thereby reducing development and production costs.

[0049] In related technologies, when a coal-fired boiler needs to reduce its output, such as when it reaches the minimum stable combustion capacity load, plasma or micro-oil stable combustion needs to be put into operation in order to ensure stable combustion of the coal-fired boiler. This will increase the cost of electricity and fuel.

[0050] Therefore, in some embodiments of the present invention, such as Figure 1 As shown, the coal-fired boiler co-firing biomass system 100 also includes a coal-fired boiler 70, which is connected to the burner 10. For example, the coal-fired boiler 70 is a counter-current combustion system. The control method also includes: The load output of the coal-fired boiler is determined to be less than or equal to 30%; Biomass pellets in biomass storage bin 30 are transported to biomass feeding system 40. Thus, when the coal-fired boiler 70 needs stable combustion, the stable combustion capability of the coal-fired boiler 70 can be improved by co-firing biomass, eliminating the need to operate plasma or micro-oil, saving energy and costs. Furthermore, co-firing biomass is beneficial to improving the ignition capability of pulverized coal, thereby further improving the stable combustion capability of the boiler.

[0051] In some embodiments, such as Figure 1 As shown, the biomass co-firing system 100 of the coal-fired boiler also includes a coal mill 71. The coal mill 71 is connected to the burner 10 through a pulverized coal pipeline 72, so that the pulverized coal can be ground by the coal mill 71 and then enter the burner 10 through the pulverized coal pipeline 72, thereby providing pulverized coal into the burner 10. The grinding of the pulverized coal by the coal mill 71 can make the pulverized coal smaller, which is easier to burn and avoids problems such as blockage, thus ensuring combustion reliability.

[0052] The following detailed description of a specific embodiment of the coal-fired boiler biomass co-firing system 100 according to the present invention is provided with reference to the accompanying drawings. It is to be understood that the following description is merely illustrative and should not be construed as limiting the invention.

[0053] The biomass co-firing system for coal-fired boilers is applied to the direct co-firing of biomass in 600MW supercritical boiler units.

[0054] The coal-fired boiler 70 is a supercritical, variable-pressure, once-through Bunsen boiler with single reheat, opposed combustion on the front and rear walls, a single furnace, and a double flue structure at the tail end. It uses baffles to regulate reheat steam temperature, features solid ash discharge, an all-steel frame, a fully suspended structure, balanced ventilation, and is located in the open air. During wet operation, the main steam temperature is primarily regulated by primary and secondary desuperheating water; during dry operation, it is coarsely adjusted by controlling the coal-to-water ratio, with desuperheating water used for fine adjustment. Under normal conditions, the reheat steam temperature is mainly regulated by the flue gas distribution baffles; in emergencies, it is regulated by a water-spray desuperheater. The combustion equipment system is arranged on the front and rear walls, employing opposed combustion and a swirl burner system. The pulverizing system is a positive-pressure, direct-fired system, equipped with six medium-speed coal mills. The coal type and biomass blending parameters for the boiler are shown in Table 1 below.

[0055] Table 1

[0056] The coal-fired boiler 70, which co-fires biomass fuel, has a maximum calorific value of 10%. The biomass preparation system has a maximum output of 40 t / h and primarily processes the biomass through crushing and pelletizing. The biomass pellets have a diameter of less than or equal to 10 cm, producing 40 t / h of biomass pellets. The biomass pellets are transported to biomass storage bins 30 via a first conveying system 51 for safe storage. Three biomass storage bins 30 are provided, each with a storage capacity of 80 t / h. When co-firing with biomass is required, the pellets are fed into a biomass pulverizer 60 via a second conveying system 52 to be ground into biomass powder. The biomass pulverizer 60 has a maximum output of 50 t / h, producing biomass powder with a particle size of less than or equal to 2 mm. The amount of biomass powder is adjusted according to the co-firing needs. The biomass powder is then transported to the B-layer burners 10 of the coal-fired boiler 70 via a biomass feeding system 40 for combustion in the furnace. There are a total of five burners 10. The coal-fired boiler 70 uses a counter-current combustion method, and the burner 10 is a swirl pulverized coal burner 10. Biomass powder is connected to the central air duct 11 of the burner 10 through a pipeline.

[0057] The methods to improve the economic efficiency of 70% biomass co-firing in coal-fired boilers are as follows: (1) Calculations show that when the biomass market price is 700 yuan / ton, the coal-fired boiler has 70 utilization hours (4500 hours), the standard coal price is 1140 yuan / ton, and 80,000 tons of biomass are co-fired annually, the carbon emission reduction benefit is 120 yuan / ton, resulting in an annual benefit of approximately 6 million yuan. At this time, co-firing biomass is economically beneficial. When the biomass market supply is high, the biomass market price will decrease, for example, to 650 yuan / ton. Calculations show that the more biomass is co-fired, the higher the benefit. The biomass can be co-fired at the same rate of 80,000 tons per year, but the output of the biomass preparation system can be increased to produce more biomass pellets and store them in the biomass silos, filling all four silos. Calculations show that when the biomass price is 650 yuan / ton, the co-firing benefit is 8.2 million yuan. When the biomass market price rises, the biomass stored in the four silos can be used for co-firing. When the biomass price is low, more biomass can be prepared, stored, and co-fired; when the price is high, less biomass can be prepared and co-fired.

[0058] (2) When the generator set needs to participate in deep peak shaving of the power grid, the coal-fired boiler 70 needs to reduce its output, especially when it reaches the minimum stable combustion capacity load of the coal-fired boiler 70, such as 30% load output. In order to ensure the stable combustion of the coal-fired boiler 70, it is necessary to put the plasma of the A-layer burner 10 or the micro-oil stable combustion of the B-layer burner 10 into operation. The A-layer has five burners 10, each with a plasma power of 200kW, and the B-layer has five burners 10, each equipped with an oil gun with an output of 0.5t / h. Stable combustion operation for one hour consumes 1000kW of plasma power, costing 500 yuan. Fuel cost is 20,000 yuan, and deep peak shaving for about 1000 hours a year costs about 20.5 million yuan. In this application, when the coal-fired boiler 70 needs stable combustion, the stable combustion capacity of the coal-fired boiler 70 is improved by co-firing biomass, and the B-layer burner 10 does not need to be put into operation with oil guns, saving about 20 million yuan in fuel costs per year. Biomass co-firing is beneficial to improving the ignition ability of pulverized coal, thereby improving the stable combustion capability of coal-fired boilers.

[0059] Other configurations and operations of the biomass co-firing system 100 and its control method in the coal-fired boiler according to embodiments of the present invention are known to those skilled in the art and will not be described in detail here.

[0060] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0061] In the description of this specification, the references to terms such as "embodiment," "specific embodiment," and "example" indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0062] Although embodiments of the invention have been shown and described, those skilled in the art will understand 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 claims and their equivalents.

Claims

1. A biomass co-firing system for a coal-fired boiler, characterized in that, include: A burner having a central air duct; A biomass processing device, wherein the biomass processing device is used to crush biomass to form biomass pellets; A biomass storage bin for storing the biomass pellets; A biomass feeding system, which is connected to the central air duct, is used to transport the biomass pellets in the biomass storage bin to the central air duct.

2. The biomass co-firing system for a coal-fired boiler according to claim 1, characterized in that, Also includes: A first conveying system is located between the biomass processing equipment and the biomass storage bin, and is used to convey the biomass pellets processed by the biomass processing equipment to the biomass storage bin.

3. The biomass co-firing system for a coal-fired boiler according to claim 1, characterized in that, The biomass pellets have a diameter of less than or equal to 10 cm.

4. The biomass co-firing system for a coal-fired boiler according to any one of claims 1-3, characterized in that, Also includes: A biomass milling machine, which is connected to the biomass storage bin, is used to grind the biomass particles into biomass powder, and the biomass feeding system is used to transport the biomass powder to the central air duct.

5. The biomass co-firing system for a coal-fired boiler according to claim 4, characterized in that, The coal-fired boiler biomass co-firing system includes: A second conveying system is located between the biomass storage bin and the biomass milling machine, and is used to convey the biomass pellets in the biomass storage bin to the biomass milling machine.

6. The biomass co-firing system for a coal-fired boiler according to claim 4, characterized in that, The biomass powder has a particle size of less than or equal to 2 mm.

7. The biomass co-firing system for a coal-fired boiler according to claim 1, characterized in that, There are multiple biomass storage bins, and each of the multiple biomass storage bins stores the biomass pellets; And / or, the burner further has a combustion chamber, and the central air duct passes through and communicates with the combustion chamber.

8. The biomass co-firing system for a coal-fired boiler according to claim 1, characterized in that, The central duct has a biomass inlet, which is connected to the biomass feeding system. Alternatively, a biomass pipe extending along the length of the central air duct may be installed inside the central air duct, and the biomass pipe may be connected to the central air duct and the biomass feeding system.

9. A control method for a coal-fired boiler co-firing biomass system, characterized in that, The coal-fired boiler biomass co-firing system is the coal-fired boiler biomass co-firing system according to any one of claims 1-8, and the control method includes: It is determined that the amount of biomass pellets stored in the biomass storage bin is greater than or equal to four-fifths of the total storage capacity of the biomass storage bin; The biomass pellets in the biomass storage bin are conveyed to the biomass feeding system at a first preset conveying rate; It is determined that the amount of biomass pellets stored in the biomass storage bin is less than or equal to three-tenths of the total amount of biomass stored in the biomass storage bin; The biomass pellets in the biomass storage bin are conveyed to the biomass feeding system at a second preset conveying rate, wherein the first preset conveying rate is greater than the second preset conveying rate.

10. The control method for a biomass co-firing system in a coal-fired boiler according to claim 9, characterized in that, The coal-fired boiler biomass co-firing system further includes a coal-fired boiler, which is connected to the burner, and the control method further includes: The load output of the coal-fired boiler is determined to be less than or equal to 30%. The biomass pellets in the biomass storage bin are transported to the biomass feeding system.

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