Boiler biomass blending combustion method and system

Abstract

The invention discloses a boiler biomass blending combustion method and system, and relates to the technical field of biomass blending combustion and boiler combustion. Comprising a boiler with a pulverized coal burner. The biomass drying device is used for drying biomass raw materials and feeding the biomass raw materials into the premixing device according to the weight ratio; the pulverized coal mill is used for drying and crushing coal briquettes and feeding the coal briquettes into the premixing device according to the weight ratio; the premixing device comprises an annular airflow chamber which is arranged in a circular ring shape, and an annular and rotatable air distribution device is arranged at the bottom of the annular airflow chamber; and the mixing device is used for uniformly mixing flaky wood chips and pulverized coal in a suspension manner to form a mixed blending combustion material, and is connected with the pulverized coal combustor through a guide pipe. Large-particle or sheet-shaped biomass can be combed and guided into the pulverized coal burner for combustion through the premixing device, the limitation requirement of the biomass is reduced, and the requirement of an existing pulverized coal burner for combustion of mixed burning materials formed by the biomass and pulverized coal can be met.

Description

Technical Field

[0001] The invention relates to the technical field of biomass blending and boiler combustion, and in particular to a boiler biomass blending method and a system thereof. Background Art

[0002] With the continuous growth of energy demand and the improvement of environmental protection awareness, biomass energy, as a renewable energy source, has attracted more and more attention in boiler combustion. At present, boiler biomass blending mainly involves mixing biomass with traditional fuels such as coal to reduce dependence on fossil energy and reduce pollutant emissions.

[0003] However, the existing boiler biomass blending method and system have some shortcomings, especially for coal-powder burner boilers. First, in the process of mixing biomass with traditional fuels, it is often difficult to achieve uniform mixing, resulting in unstable combustion and affecting the operating efficiency of the boiler. Secondly, the existing blending system has limited processing capacity for biomass and cannot adapt well to biomass raw materials of different types and properties, limiting the scope of biomass energy utilization. In addition, the existing coal-powder burner boiler has high requirements for biomass.

[0004] It can be seen that the existing boiler biomass blending method and system of pulverized coal burner have shortcomings in terms of mixing uniformity, high biomass requirements and combustion effect. A more efficient and stable boiler biomass blending method and system are needed to solve these problems. Summary of the invention

[0005] In view of the deficiencies in the above-mentioned prior art, the present invention provides a boiler biomass blending method and system, which can enable larger particles or flakes of biomass to be combed through a premixing device and introduced into a pulverized coal burner for combustion, thereby reducing the restriction requirements on biomass, and can meet the requirements of existing pulverized coal burners for combustion of biomass and pulverized coal to form a mixed blending material, thereby improving energy utilization efficiency, reducing production costs, and reducing pollution to the environment.

[0006] The specific technical solutions are as follows:

[0007] In a first aspect, the present invention discloses a boiler biomass blending system, including a boiler with a pulverized coal burner; and further comprising:

[0008] Biomass drying device, used for drying biomass raw materials and feeding them into the pre-mixing device according to weight ratio;

[0009] Coal pulverizer, used to dry and crush coal lumps and feed them into the pre-mixing device according to weight ratio;

[0010] The premixing device comprises an annular airflow chamber arranged in a circular shape, and an annular and rotatable air distribution device is arranged at the bottom of the annular airflow chamber; a first feed port connected to a biomass drying device and a second feed port connected to a coal powder mill are arranged at one end of the annular airflow chamber, and a discharge port is arranged at the other end of the annular airflow chamber; the height of the discharge port is the same as that of the annular airflow chamber and is tangent to the annular airflow chamber; a flap for opening and closing the discharge port is arranged at the discharge port, and the flap is connected to a first motor installed on the top of the premixing device, and the flap can be driven to rotate by the first motor to form a parallel inlet or to partition the annular airflow chamber to form a V-shaped inlet; the discharge port is connected to the coal powder interface of the coal powder burner through a guide pipe; the air inlet of the air distribution device is connected to the boiler exhaust gas, and the top of the annular airflow chamber is connected to the secondary air duct of the coal powder burner through a flue gas collection pipe.

[0011] In the above scheme, the biomass drying device includes a screw drying device, a hot air inlet of the screw drying device is connected to an exhaust gas device of a boiler, and a hot air outlet of the screw drying device is connected to an air distribution device of a premixing device.

[0012] Furthermore, in the above scheme, a plurality of hoods are evenly arranged on the upper end surface of the air distribution device, the hoods are inclined in the annular direction relative to the annular airflow chamber, and the rotation direction of the air distribution device is the same as the inclination direction of the hoods; the hoods are connected to the air inlet of the air distribution device.

[0013] In the above solution, the guide pipe is a rounded rectangular pipe, and one end of the guide pipe extending into the annular airflow chamber is tangent to the contour of the side wall of the annular airflow chamber.

[0014] Furthermore, in the above scheme, the pulverized coal burner is provided with 2-4 pulverized coal interfaces, which are evenly arranged around the pulverized coal burner; the guide pipe is divided into a plurality of channels according to the number of pulverized coal interfaces, and each channel is connected to a pulverized coal interface.

[0015] Furthermore, in the above scheme, the channels are separated and arranged in the height direction of the annular airflow chamber.

[0016] In the above solution, a vibration plate is provided in the annular airflow chamber at a position corresponding to the channel interval, and the vibration plate is connected to a vibration motor located on the premixing device.

[0017] In the above scheme, the biomass raw material is in the form of flakes.

[0018] Furthermore, in the above scheme, the first feed port is arranged between the second feed port and the discharge port, and is close to the discharge port; the rotation direction of the air distribution device is to pass through the first feed port, the second feed port and the discharge port in sequence.

[0019] In another aspect, the present invention discloses a method for a boiler biomass co-firing system, comprising:

[0020] The biomass raw material is dried by a biomass drying device, and the moisture content is controlled to be less than 15% to obtain dry biofuel; the coal block and coal powder are ground and dried to obtain coal powder;

[0021] The discharge port of the premixing device is closed, and the biofuel and coal powder are continuously added into the premixing device according to the weight ratio; the air distribution device in the premixing device rotates to generate a rotating airflow so that the coal powder and the biofuel are suspended and mixed to obtain a mixed fuel, and the content of the mixed fuel per unit volume in the annular airflow chamber meets the set requirements;

[0022] Connect the pulverized coal to the pulverized coal burner's pulverized coal interface, start the boiler combustion, and stabilize the boiler temperature at 1200℃-1300℃;

[0024] Open the discharge port of the premixing device and introduce the mixed fuel into the pulverized coal interface of the pulverized coal burner through the guide pipe;

[0025] Gradually reduce the amount of pulverized coal directly connected to the pulverized coal burner, so that the boiler temperature stabilizes at 1000℃-1100℃, and close the pulverized coal directly connected to the pulverized coal burner.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The boiler biomass blending system of the present invention can efficiently blend biomass and coal powder for blending and blending, thereby improving energy utilization efficiency. The biomass raw materials and coal blocks are dried and crushed by the biomass drying device and the coal powder mill, respectively, thereby ensuring the quality of the fuel. The annular airflow chamber and the rotatable air distribution device in the premixing device can fully suspend and mix the coal powder and the biofuel to obtain a uniform blended material. The design of the guide pipe and the setting of multiple coal powder interfaces enable the blended material to be smoothly introduced into the coal powder burner.

[0028] The present invention adopts biomass coke as a blended fuel, thereby reducing the generation of pollutants NOx during the combustion process. At the same time, by introducing the boiler tail gas into a biomass drying device, a premixing device, and finally into a boiler, the heat in the tail gas is utilized to realize heat recycling. At the same time, the oxygen content in the boiler tail gas is low, and the combustion of biomass can be avoided in the premixing device, and the high-temperature tail gas can carbonize the burrs on the edges of the flaky biomass or the fine connecting fibers between the flaky biomass. One is that the gas generated in this process can be introduced into the boiler for combustion, and the other is that the flaky biomass treated with the high-temperature tail gas is more dispersed, the suspension distribution effect is enhanced, and the blockage when introducing the guide pipe and the pulverized coal burner is reduced; so that large particles or flaky wood chip biomass fuels can also meet the needs of the pulverized coal burner. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1This is a functional module framework diagram of the boiler biomass blending system of the present invention;

[0030] Figure 2 It is a schematic diagram of the structure of the premixing device of the present invention;

[0031] Figure 3 is a schematic cross-sectional view of a premixing device of the present invention;

[0032] Figure 4 It is a schematic diagram of closing the flip cover in another embodiment of the present invention;

[0033] Figure 5 It is a schematic diagram of opening the flip cover in another embodiment of the present invention;

[0034] Figure 6 It is a schematic diagram of another embodiment of the present invention in which the flip cover is opened to form a V-shaped entrance;

[0035] Figure 7 It is a schematic diagram of the structure of the discharge port of the present invention.

[0036] In the accompanying drawings, 1-biomass drying device, 2-coal powder mill, 3-premixing device, 4-coal powder burner, 5-boiler, 6-guide pipe, 7-smoke collection pipe, 8-control valve, 301-annular airflow chamber, 302-air distribution device, 303-first feed inlet 304-second feed inlet, 305-discharge port, 306-flip cover, 307-wind hood, 308-channel, 309-vibration plate, 310-vibration motor, 311-driving device. DETAILED DESCRIPTION

[0037] The following is a further detailed description of the embodiments of the invention in conjunction with the accompanying drawings to make the objectives, technical solutions and technical effects of the invention more clearly presented.

[0038] like Figure 1-Figure 3 The present invention discloses a boiler biomass blending system, comprising a boiler 5 with a pulverized coal burner 4, a biomass drying device 1, a pulverized coal mill 2 and a premixing device 3.

[0039] The biomass drying device 1 is used to dry the biomass raw materials and feed them into the premixing device 3 according to the weight ratio. The biomass drying device 1 includes a screw drying device, the hot air inlet of the screw drying device is connected to the tail gas device of the boiler 5, and the hot air outlet of the screw drying device is connected to the air distribution device 302 of the premixing device 3.

[0040] The coal powder mill 2 is used to dry and crush the coal blocks and feed them into the pre-mixing device 3 according to the weight ratio. The weight measurement here is completed by a measurable conveying device.

[0041] The premixing device 3 is used to suspend and mix the flaky wood chips and the coal powder evenly to form a mixed combustion material, and is connected to the coal powder burner 4 through the guide pipe 6.

[0042] like Figure 2-Figure 3 As shown, the premixing device 3 includes an annular airflow chamber 301 arranged in a circular shape, and an annular and rotatable air distribution device 302 is provided at the bottom of the annular airflow chamber 301, and the air distribution device 302 is connected to the boiler exhaust gas. A first feed port 303 connected to the biomass drying device 1 and a second feed port 304 connected to the coal powder mill 2 are provided at one end of the annular airflow chamber 301, and a discharge port 305 is provided at the other end of the annular airflow chamber 301. The height of the discharge port 305 is the same as that of the annular airflow chamber 301, and it is tangent to the annular airflow chamber 301. A flap 306 for opening and closing the discharge port 305 is provided at the discharge port 305. The discharge port 305 is connected to the coal powder interface of the coal powder burner 4 through the guide pipe 6. The top of the annular airflow chamber 301 is connected to the secondary air duct of the coal powder burner 4 through the flue gas collection pipe 7.

[0043] The air distribution device 302 includes a rotating part and a fixed part, the rotating part and the fixed part are connected by a rotary seal, the rotating part and the fixed part are connected, the rotating part is driven by a driving device 311 located in the premixing device 3, so that the rotating part rotates; the fixed part is connected to the boiler exhaust gas. A plurality of hoods 307 are evenly arranged on the upper end surface of the rotating part, the hoods 307 are inclined relative to the annular direction of the annular airflow chamber 301, and the rotation direction of the air distribution device 302 is the same as the inclination direction of the hoods 307; the hoods 307 are connected to the air inlet of the air distribution device 302. The rotating part and the bottom of the annular airflow chamber 301 are a rotating seal structure.

[0044] During operation, the hot exhaust gas enters from the fixed part, passes through the rotating part and the hood 307 in sequence, and is finally discharged from the air outlet of the hood 307; since the rotating part is constantly rotating, a rotating wind is formed, and the rotating wind rotates in a circle around the annular airflow chamber 301, so that the mixed and mixed materials in suspension rotate in a circle around the annular airflow chamber 301. In this process, the burrs or tiny debris of the biomass, specifically the flaky wood chips, will be carbonized by the hot air and discharged through the smoke collection pipe 7 at the top of the annular airflow chamber 301; it should be clear that the necessary screen can be set at the corresponding smoke collection pipe 7. As the mixed fuel is constantly rotating, the entanglement between the fibers of the flaky wood chips will be eliminated, so that the flaky wood chips can be evenly suspended, and the mixed fuel formed by mixing with coal powder can pass through the coal powder channel 308 of the coal powder burner 4 better. One reason is that the coal powder will fully contact the flaky wood chips and partially adhere to the surface of the flaky wood chips. When passing through the coal powder channel 308 of the coal powder burner 4 or the guide pipe 6, it plays a role in reducing friction and improving passability.

[0045] The guide pipe 6 is a rounded rectangular pipe, and one end of the guide pipe 6 extending into the annular airflow chamber 301 is tangent to the contour of the side wall of the annular airflow chamber 301 .

[0046] like Figure 4-Figure 6 As shown, the first feed port 303 is disposed between the second feed port 304 and the discharge port 305, and is close to the discharge port 305; the air distribution device 302 rotates in a direction that passes through the first feed port 303, the second feed port 304, and the discharge port 305 in sequence. Figure 4 As shown, the flip cover 306 is in a closed state; Figure 5 As shown, the flip cover 306 is generally opened to form a parallel entrance; Figure 5 As shown, the flip cover 306 is in the maximum open state, and the annular airflow chamber 301 is separated to form a V-shaped inlet.

[0047] In another embodiment, the pulverized coal burner 4 is provided with 2-4 pulverized coal interfaces, and the pulverized coal interfaces are evenly arranged relative to the pulverized coal burner 4; the guide pipe 6 is divided into a plurality of channels 308 according to the number of pulverized coal interfaces, and each channel 308 is connected to the pulverized coal interface. The channels 308 are arranged in a separated manner along the height direction of the annular airflow chamber 301. A vibration plate 309 is provided in the annular airflow chamber 301 at the interval corresponding to the channels 308, and the vibration plate 309 is connected to a vibration motor 310 located on the premixing device 3, as shown in FIG. Figure 7 shown.

[0048] like Figure 1-Figure 7 In the figure, the solid arrows indicate the flow direction of the material, and the dotted arrows indicate the flow direction of the boiler exhaust or hot gas. Figure 1 , it can be clearly understood that the method of the boiler biomass blending system disclosed in the present invention comprises the following steps:

[0049] Firstly, the biomass raw material is dried by the biomass drying device 1, and the moisture content is controlled to be lower than 15% to obtain dry biofuel; the coal block is crushed and dried by the coal powder mill 2 to obtain coal powder.

[0050] Secondly, the discharge port 305 of the premixing device 3 is closed, and the biofuel and coal powder are continuously added into the premixing device 3 according to the weight ratio; the air distribution device 302 in the premixing device 3 rotates to generate a rotating airflow so that the coal powder and the biofuel are suspended and mixed to obtain a mixed fuel, and the content of the mixed fuel per unit volume in the annular airflow chamber 301 meets the set requirements.

[0051] Then, the pulverized coal is connected to the pulverized coal interface of the pulverized coal burner 4, the boiler 5 is started to burn, and the temperature of the boiler 5 is stabilized at 1200°C-1300°C.

[0052] Furthermore, the discharge port 305 of the premixing device 3 is opened, and the mixed fuel is introduced into the pulverized coal interface of the pulverized coal burner 4 through the guide pipe 6 .

[0053] Finally, the amount of pulverized coal directly connected to the pulverized coal burner 4 is gradually reduced, so that the temperature of the boiler 5 is stabilized at 1000° C.-1100° C., and the pulverized coal directly connected to the pulverized coal burner 4 is closed.

[0054] The above scheme dries and crushes the biomass raw materials and coal blocks respectively through the biomass drying device 1 and the coal powder mill 2 to achieve the appropriate moisture content and particle size. Then, in the premixing device 3, the swirling airflow generated by the rotation of the air distribution device 302 is used to suspend and mix the coal powder and the biofuel to form a uniform mixed blending material. The design of the annular airflow chamber 301 and the adjustable structure of the discharge port 305 enable the mixed blending material to be smoothly introduced into the coal powder burner 4. Finally, by controlling the amount of coal powder directly connected to the coal powder burner 4, the temperature of the boiler 5 is stably controlled to ensure the effect of mixed blending. This scheme can overcome the situation that the existing coal powder burner 4 is easy to block the coal powder burner 4 when the biomass is large in size during biomass blending; this scheme uses hot air to treat the mixed blending material to overcome the above-mentioned shortcomings, and can enable the mixed blending material to smoothly enter the coal powder burner 4. In this solution, the biomass does not need to be granulated, but only needs to be broken into flakes with a length of no more than 4.5 cm; this reduces the need for further processing of the biomass, and can be well applied to the combustion of a boiler 5 with a pulverized coal burner 4 .

[0055] The above description is only a preferred feasible embodiment of the present invention and is not intended to limit the scope of the patent application of the present invention. All equivalent changes, equivalent substitutions or modified changes performed within the technical spirit and principles suggested by the present invention should be included in the scope of patent protection covered by the present invention.

Claims

1. A boiler biomass co-firing system, comprising a boiler with a pulverized coal burner; characterized in that: Also includes: Biomass drying device, used for drying biomass raw materials and feeding them into the pre-mixing device according to weight ratio; Coal pulverizer, used to dry and crush coal lumps and feed them into the pre-mixing device according to weight ratio; The premixing device comprises an annular airflow chamber arranged in a circular shape, and an annular and rotatable air distribution device is arranged at the bottom of the annular airflow chamber; a first feed port connected to a biomass drying device and a second feed port connected to a coal powder mill are arranged at one end of the annular airflow chamber, and a discharge port is arranged at the other end of the annular airflow chamber; the height of the discharge port is the same as that of the annular airflow chamber and is tangent to the annular airflow chamber; a flap for opening and closing the discharge port is arranged at the discharge port, and the flap is connected to a first motor installed on the top of the premixing device, and the flap can be driven to rotate by the first motor to form a parallel inlet or to partition the annular airflow chamber to form a V-shaped inlet; the discharge port is connected to the coal powder interface of the coal powder burner through a guide pipe; the air inlet of the air distribution device is connected to the boiler exhaust gas, and the top of the annular airflow chamber is connected to the secondary air duct of the coal powder burner through a flue gas collection pipe.

2. A boiler biomass co-firing system according to claim 1, characterized in that: The biomass drying device comprises a screw drying device, a hot air inlet of the screw drying device is connected to an exhaust gas device of a boiler, and a hot air outlet of the screw drying device is connected to an air distribution device of a premixing device.

3. A boiler biomass co-firing system according to claim 1, characterized in that: The upper end surface of the air distribution device is evenly provided with a plurality of hoods, the hoods are inclined relative to the annular direction of the annular airflow chamber, and the rotation direction of the air distribution device is the same as the inclination direction of the hoods; the hoods are connected to the air inlet of the air distribution device.

4. A boiler biomass co-firing system according to claim 1, characterized in that: The guide pipe is a rounded rectangular pipe, and one end of the guide pipe extending into the annular airflow chamber is tangent to the contour of the side wall of the annular airflow chamber.

5. A boiler biomass blending system according to claim 4, characterized in that: The pulverized coal burner is provided with 2-4 pulverized coal interfaces, which are evenly arranged around the pulverized coal burner; the guide pipe is divided into a plurality of channels according to the number of pulverized coal interfaces, and each channel is connected to a pulverized coal interface.

6. A boiler biomass blending system according to claim 5, characterized in that: The channels are separated and arranged along the height direction of the annular airflow chamber.

7. A boiler biomass blending system according to claim 6, characterized in that: A vibration plate is provided in the annular air flow chamber at a position corresponding to the channel interval, and the vibration plate is connected to a vibration motor located on the pre-mixing device.

8. The boiler biomass co-firing system according to claim 1, characterized in that: The biomass raw material is in flake form.

9. The boiler biomass co-firing system according to claim 1, characterized in that: The first feed port is arranged between the second feed port and the discharge port, and is close to the discharge port; the rotation direction of the air distribution device is to pass through the first feed port, the second feed port and the discharge port in sequence.

10. A method for a boiler biomass co-firing system according to any one of claims 1 to 9, characterized in that: The biomass raw material is dried by a biomass drying device, and the moisture content is controlled to be less than 15% to obtain dry biofuel; the coal block and coal powder are ground and dried to obtain coal powder; The discharge port of the premixing device is closed, and the biofuel and coal powder are continuously fed into the premixing device according to the weight ratio; The air distribution device in the premixing device rotates to generate a rotating airflow so that the coal powder and the biofuel are suspended and mixed to obtain a mixed fuel, and the content of the mixed fuel per unit volume in the annular airflow chamber meets the set requirements; Connect the pulverized coal to the pulverized coal burner's pulverized coal interface, start the boiler combustion, and stabilize the boiler temperature at 1200℃-1300℃; Open the discharge port of the premixing device and introduce the mixed fuel into the pulverized coal interface of the pulverized coal burner through the guide pipe; Gradually reduce the amount of pulverized coal directly connected to the pulverized coal burner, so that the boiler temperature stabilizes at 1000℃-1100℃, and close the pulverized coal directly connected to the pulverized coal burner.

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