A processing system for large-scale consumption of biomass in power plants and its operation method

Abstract

The present invention discloses a processing system for large-scale consumption of biomass in a power plant and an operation method thereof, comprising a biomass roasting device, a pulverizing device and a coal-fired boiler; biomass for the power plant to be extruded, crushed and roasted is introduced into a material inlet of the biomass roasting device; an extrusion and crushing device arranged inside the biomass roasting device extrude and crush the input biomass; flue gas from the coal-fired boiler is introduced into a flue gas inlet of the biomass roasting device, and the flue gas makes the interior of the biomass roasting device an oxygen-deficient environment, and the roasting temperature reaches 200°C to 300°C; pyrolysis gas outlet of the biomass roasting device discharges pyrolysis gas generated by roasting and flue gas after heat exchange, and the material outlet of the biomass roasting device discharges roasted biomass; the pulverizing device inputs coal and roasted biomass, dries and grinds the roasted biomass and coal into powder for boiler combustion, and outputs the powder; the primary air and secondary air inlets of the coal-fired boiler are introduced into the powder for boiler combustion output by the pulverizing device for combustion.

Description

Technical Field

[0001] The present invention relates to a processing system for absorbing biomass on a large scale in a power plant and an operating method thereof. Background Art

[0002] The demand for carbon reduction is increasing, and coal-fired power generation is a major source of carbon dioxide emissions. Using large, efficient coal-fired units to co-fire biomass fuels is an effective response to this need. Replacing some coal with biomass reduces coal consumption and addresses the disposal of waste such as straw. Furthermore, because biomass is a zero-CO2 fuel, using biomass for power generation can reduce CO2 emissions, offering significant social and environmental benefits.

[0003] The common existing biomass co-combustion technologies can be divided into direct co-combustion and indirect co-combustion. Among them, the indirect co-combustion technology is to send the fuel gas after biomass gasification into the boiler for combustion. The raw material adaptability of this technology is relatively wide and it can avoid phenomena such as coking and slagging, but it requires a lot of new equipment and high investment, so it is currently less used. The most widely used biomass co-combustion technology is mainly direct co-combustion technology, which is to send biomass directly into the boiler for combustion. However, due to the high moisture content and large particle size of the biomass, the biomass must be pretreated.

[0004] At present, the common pretreatment method used by power plants is to outsource biomass pretreatment to specialized crushing plants or purchase specialized equipment for crushing. Due to the large amount of biomass, the processing cost of this pretreatment method is very high, which is a relatively large burden for power plants that burn biomass. Summary of the Invention

[0005] The present invention aims to provide a biomass processing system and operating method for large-scale biomass consumption in power plants, addressing one or more of the aforementioned technical issues. By incorporating a biomass torrefaction device, the system, without modifying the existing pulverizing equipment, can improve the calorific value of biomass and boiler efficiency, while also addressing pipeline blockage caused by uneven particle size during biomass co-combustion.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A processing system for large-scale consumption of biomass in a power plant includes a biomass baking device, a pulverizing device and a coal-fired boiler;

[0008] The biomass baking device has a material inlet and a material outlet, and an extrusion crushing device is provided below the material inlet. The biomass to be processed passes through the material inlet and the extrusion crushing device into the screw feeder and is then discharged from the material outlet. A flue gas inlet is provided at one end of the screw feeder, and a pyrolysis gas outlet is provided at the other end of the screw feeder. The flue gas inlet is connected to the flue of the coal-fired boiler, and a fan is provided on the pyrolysis gas outlet. The flue gas is passed into the screw feeder to bake the crushed biomass, and the pyrolysis gas generated by baking and the flue gas after heat exchange are extracted from the pyrolysis gas outlet by the fan.

[0009] The input end of the pulverizing device is connected to the material outlet of the biomass roasting device and the raw coal feed port, and the output end of the pulverizing device is connected to the coal-fired boiler. The pulverizing device dries and grinds the coal and roasted biomass to obtain pulverized material for boiler combustion and outputs it.

[0010] The primary air and secondary air inlets of the coal-fired boiler are used to introduce the boiler combustion powder output by the powder making device.

[0011] As a further improvement, the pyrolysis gas generated by the biomass torrefaction device and the flue gas after heat exchange are input into the main combustion zone of the coal-fired boiler to assist combustion.

[0012] As a further improvement, the pyrolysis gas generated by the biomass torrefaction device and the flue gas after heat exchange are input between the main combustion zone and the sofa air of the coal-fired boiler for reburning.

[0013] As a further improvement, a first exhaust pipe is provided at the economizer outlet of the coal-fired boiler, and the first exhaust pipe is used to input flue gas to the flue gas inlet of the biomass roasting device. A first flow control valve is provided on the first exhaust pipe.

[0014] As a further improvement, the turning chamber of the coal-fired boiler is provided with a second exhaust pipe, which is used to input flue gas to the flue gas inlet of the biomass roasting device, and a second flow control valve is provided on the second exhaust pipe.

[0015] As a further improvement, the extrusion and crushing device arranged inside the biomass roasting device is a spiral compression rod.

[0016] As a further improvement, a belt conveyor is further included for inputting the roasted biomass from the material outlet of the biomass roasting device into the milling device.

[0017] As a further improvement, the flue gas and materials in the biomass roasting device adopt a countercurrent indirect contact heat exchange method.

[0018] A method for operating a biomass processing system for large-scale consumption in a power plant comprises the following steps:

[0019] S1: The material inlet of the biomass torrefaction device is fed with biomass for power plant to be crushed and torrefied;

[0020] S2: The extrusion and crushing device provided inside the biomass roasting device extrudes and crushes the input biomass;

[0021] S3: Flue gas from a coal-fired boiler is introduced into the flue gas inlet of the biomass torrefaction device, and the flue gas creates an oxygen-deficient environment inside the biomass torrefaction device, and the torrefaction temperature reaches 200°C to 300°C;

[0022] S4: The pyrolysis gas outlet of the biomass torrefaction device discharges the pyrolysis gas generated by torrefaction and the flue gas after heat exchange, and the material outlet of the biomass torrefaction device discharges the torrefied biomass;

[0023] S5: The pulverizing device inputs coal and roasted biomass, dries and grinds the roasted biomass and coal into pulverized coal for boiler combustion, and outputs the pulverized coal;

[0024] S6: The primary air and secondary air inlets of the coal-fired boiler are fed with the boiler combustion powder output by the pulverizing device for combustion.

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

[0026] The present invention specifically provides a new processing system for large-scale biomass consumption in power plants, which can fully utilize the existing equipment of the power plant to pre-treat the biomass and reduce the cost of biomass co-firing in the power plant. Specifically, the system provided by the present invention, without changing the existing pulverizing device, adds a biomass baking device to bake and crush the biomass before sending it to the furnace for combustion, thereby improving the calorific value of the biomass and boiler efficiency, while also solving the problem of pipeline blockage caused by uneven particle size of biomass co-firing. In addition, the system couples the boiler with the baking device, using the boiler's medium-temperature flue gas as the system's heat source, achieving a cascaded utilization of energy.

[0027] Specifically explained in principle, the advantages of the pretreatment system of the present invention include:

[0028] (1) Improved boiler efficiency. After pretreatment, the moisture content of biomass is greatly reduced, the fixed carbon content is increased, and the calorific value is greatly improved;

[0029] (2) No additional investment in equipment is required, and the power plant's pulverized coal processing equipment can be directly used, which can greatly reduce the cost of biomass processing and co-firing in the power plant;

[0030] (3) It can solve the problem of pipeline blockage caused by uneven biomass crushing particle size. The baking device can perform preliminary crushing of the biomass, and can also perform secondary crushing after entering the milling device;

[0031] (4) The cascade utilization of energy is realized. The high-temperature flue gas generated by the boiler is used for heat transfer and power generation, and part of the medium-temperature flue gas generated is used as the heat source of the baking device. There is no need to provide a separate heat source, which improves the energy utilization rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a schematic structural diagram of a processing system for absorbing biomass on a large scale in a power plant, provided in Example 1 of the present invention;

[0033] Figure 2 This is a schematic structural diagram of a processing system for absorbing biomass on a large scale in a power plant, provided in Example 2 of the present invention;

[0034] In the figure: 1. Biomass for power plant; 2. Biomass baking device; 3. Pulverizing device; 4. Raw coal; 5. Pyrolysis gas; 6. Sofa air; 7. Coal-fired boiler; 8. Flue gas duct; 9. Flue gas treatment system; 10. Induced draft fan. DETAILED DESCRIPTION

[0035] In order to deepen the understanding of the present invention, the present invention will be further described in detail below with reference to embodiments and drawings. The embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0036] Example 1

[0037] See also Figure 1 , a processing system for large-scale consumption of biomass in a power plant according to an embodiment of the present invention, the system comprises: a biomass baking device 2, a pulverizing device 3 and a coal-fired boiler 7;

[0038] Among them, a spiral compression rod is provided inside the biomass roasting device 2 for preliminary extrusion and crushing of the incoming power plant biomass 1. The inlet of the biomass roasting device 2 is used to input the power plant biomass 1. The interior is an oxygen-deficient environment with a temperature of 200-300°C. The outlet is connected to a belt conveyor to transport the roasted power plant biomass to the pulverizing device 3. It is also connected to the inlet of the main combustion zone of the coal-fired boiler 7 to pass the pyrolysis gas 5 generated by the roasting into the coal-fired boiler 7 for combustion. The biomass roasting device 2 is also connected to the flue gas pipe 8 from the coal-fired boiler 7. The flue gas enters from the left inlet of the biomass roasting device 2 and is connected to the main combustion zone inlet of the coal-fired boiler 7. The power plant uses biomass 1 for direct contact heat exchange and enters the main combustion zone of the boiler together with the pyrolysis gas 5; the inlet of the pulverizing device 3 receives the raw coal 4 and the roasted biomass from the power plant, dries and grinds the roasted biomass and coal into powder for boiler combustion, and the outlet is connected to the primary air and secondary air inlets of the coal-fired boiler to enter the boiler for combustion; the flue gas generated by the coal-fired boiler is treated by the flue gas treatment system 9 and then discharged. At the same time, flue gas is extracted at the outlet of the economizer at the rear of the boiler and in the boiler turning chamber respectively, and the amount of each extracted flue gas is controlled by the valve opening. After mixing, the flue gas enters the inlet of the biomass roasting device 2 through the flue gas duct 8 and the induced draft fan 10.

[0039] The embodiments of the present invention are illustrative. Generally, biomass power plant fuels are mainly divided into the following categories:

[0040] Hard straw fuels mainly include: cotton straw, wood chips, and fuel pellets made from compressed straw;

[0041] Soft straw mainly includes wheat straw, corn straw and other soft straws.

[0042] Depending on the type of straw, straw power generation will adopt different feeding methods; hard straw material transportation is mainly based on spiral transportation, while soft straw is mainly based on chain transportation.

[0043] The embodiments of the present invention are for illustrative purposes only. In the prior art, after coal is transported to a power plant, it is first stored in a coal yard. Mechanical equipment (generally an excavator, bulldozer, or bucket wheel excavator, etc.) delivers the coal into a coal hopper and then transports it to a raw coal bunker using a belt. The following operations are performed during the belt transportation process, including:

[0044] (1) The separation device removes impurities such as iron and wood mixed in the coal;

[0045] (2) Weighing by electronic scale;

[0046] (3) The coal is fed into the primary crushing equipment, where the crusher crushes the coal into coal blocks less than 50 mm in size;

[0047] (4) The coal is sent to the secondary crushing equipment. Because different types of boilers have different requirements for the particle size of coal, the equipment used is also different. Generally, the equipment used in pulverized coal boilers is a coal mill, and the circulating fluidized bed boiler is a fine coal crusher;

[0048] (5) The coal of qualified particle size is sent into the raw coal bin and then sent into the boiler for combustion by the coal feeder.

[0049] The pulverizing device used in the embodiment of the present invention has not been improved on the device itself, but has been greatly improved on the input of the device. After the improvement, the input is a mixture of raw coal and roasted biomass; the input device can be a belt conveyor device, etc.

[0050] The system provided by the present invention, without changing the existing pulverizing device, first bakes and crushes the biomass before sending it into the furnace for combustion, thereby improving the calorific value of the biomass and the boiler efficiency, and at the same time solving the problem of pipeline blockage caused by uneven particle size of biomass co-combustion. In addition, the system couples the boiler with the baking device and uses the medium-temperature flue gas of the boiler as the system heat source, realizing the cascade utilization of energy.

[0051] An embodiment of the present invention provides an operating method for a processing system for large-scale biomass consumption in a power plant, comprising the following steps:

[0052] The biomass is first sent to the biomass baking device 2 for extrusion baking. The baking device is an oxygen-deficient environment with a baking temperature between 200 and 300°C.

[0053] The roasted biomass is conveyed by belt conveyor together with raw coal 4 into the pulverizing device 3, dried and ground in the pulverizing system, and then fed into the primary air and secondary air inlets of the coal-fired boiler;

[0054] The coal-fired boiler burns the fed coal and biomass powder to generate electricity. Part of the flue gas is drawn out from the economizer outlet at the rear of the boiler and the boiler turning chamber and sent to the biomass roasting device 2 for direct contact heat exchange, providing heat for the device.

[0055] The pyrolysis gas 5 generated by the biomass roasting device 2 and the flue gas after heat exchange are sent into the main combustion zone of the boiler for combustion.

[0056] The significant improvements of the operating method of the present invention include: improving boiler efficiency, greatly reducing the moisture content of the pretreated biomass, increasing the fixed carbon content, and greatly improving the calorific value; no additional investment in more equipment is required, and the coal powder processing equipment of the power plant can be directly used, which can greatly reduce the processing and blending costs of biomass in the power plant; it can solve the pipeline blockage problem caused by uneven particle size of biomass crushing, and the baking device can perform preliminary crushing on the biomass, and can also perform secondary crushing after entering the pulverizing device; it realizes the cascade utilization of energy, and the high-temperature flue gas generated by the boiler is used for heat transfer and power generation, and part of the medium-temperature flue gas generated is used as the heat source of the baking device, without the need to provide a separate heat source, thereby improving energy utilization.

[0057] Example 2

[0058] See also Figure 2 , an embodiment of the present invention provides a processing system for large-scale consumption of biomass in a power plant, the system comprising a biomass baking device 2, a pulverizing device 3 and a coal-fired boiler 7;

[0059] Among them, the biomass baking device 2 is divided into inner and outer sides, the inner side is a spiral compression rod, which can perform preliminary extrusion and crushing on the incoming biomass, the internal inlet enters the biomass, the internal is an oxygen-deficient environment, the baking temperature is between 200 and 300 ° C, the biomass produced at the outlet is connected to the belt conveyor, and the baked biomass is transported to the pulverizing device 3. At the same time, the high calorific value pyrolysis oil and gas produced can be sent to the boiler between the main combustion zone and the sofa wind 6 through the pipeline as reburning fuel, and can also be sent to the boiler as combustion-supporting wind at the main combustion zone. The outer inlet of the baking device is connected to the flue gas pipe 8 from the coal-fired boiler, and the flue gas enters from the right side of the baking device. The air enters the boiler and exits from the left side outlet in a countercurrent indirect contact manner. The outlet is connected to the air preheater outlet of the boiler and directly enters the dust collector and the flue gas treatment system 9 of the boiler to treat the flue gas. The inlet of the pulverizing device 3 receives the raw coal 4 and the roasted biomass from the power plant, dries and grinds the roasted biomass and coal into powder for boiler combustion, and the outlet is connected to the primary air and secondary air inlets of the coal-fired boiler. The flue gas generated by the coal-fired boiler is treated by the flue gas treatment system 9 and then discharged. At the same time, part of the flue gas is drawn out from the economizer outlet at the rear of the boiler and the turning chamber of the boiler, and enters the outer inlet of the biomass roasting device 2 through the flue gas duct 8 and the induced draft fan 10.

[0060] An embodiment of the present invention provides an operating method for a processing system for large-scale biomass consumption in a power plant, comprising the following steps:

[0061] The biomass is first sent to the biomass baking device 2 for extrusion baking. The baking device is an oxygen-deficient environment with a baking temperature between 200 and 300°C.

[0062] The roasted biomass is conveyed by belt conveyor together with raw coal 4 into the pulverizing device 3, dried and ground in the pulverizing system, and then fed into the primary air and secondary air inlets of the coal-fired boiler;

[0063] The coal-fired boiler burns the fed coal powder and biomass powder to generate electricity. Part of the flue gas is drawn out from the economizer outlet at the rear of the boiler and the boiler turning chamber and sent to the outer sleeve of the biomass roasting device 2 for heat exchange, providing heat for the device.

[0064] The pyrolysis oil and gas produced by the biomass roasting device 2 is sent to the boiler for combustion. It can be sent to the main combustion zone of the boiler for combustion assistance, or sent between the main combustion zone and the sofa air 6 for reburning.

[0065] In summary, the embodiment of the present invention provides a processing system for large-scale consumption of biomass in power plants, which includes a biomass baking device, a pulverizing device and a coal-fired boiler; the biomass baking device is connected to the inlet of the pulverizing device through a belt transmission, the outlet of the pulverizing device is connected to the coal-fired boiler, and the inlet of the baking device is connected to the boiler through a flue gas pipe.

[0066] Without changing the existing pulverizing device, this system adds a biomass baking device, which bakes the biomass first and then crushes it before entering the furnace for combustion, thereby improving the calorific value of the biomass and the boiler efficiency. At the same time, it solves the problem of pipeline blockage caused by uneven particle size of biomass co-combustion. In addition, the system couples the boiler with the baking device and uses the boiler's medium-temperature flue gas as the system heat source, realizing the cascade utilization of energy.

[0067] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A biomass treatment system for large-scale consumption in power plants, characterized in that: Includes biomass baking unit, pulverizing unit and coal-fired boiler; The biomass baking device has a material inlet and a material outlet, and an extrusion crushing device is provided below the material inlet. The biomass to be processed passes through the material inlet and the extrusion crushing device into the screw feeder and is then discharged from the material outlet. A flue gas inlet is provided at one end of the screw feeder, and a pyrolysis gas outlet is provided at the other end of the screw feeder. The flue gas inlet is connected to the flue of the coal-fired boiler, and a fan is provided on the pyrolysis gas outlet. The flue gas is passed into the screw feeder to bake the crushed biomass, and the pyrolysis gas generated by baking and the flue gas after heat exchange are extracted from the pyrolysis gas outlet by the fan. The input end of the pulverizing device is connected to the material outlet of the biomass roasting device and the raw coal feed port, and the output end of the pulverizing device is connected to the coal-fired boiler. The pulverizing device dries and grinds the coal and roasted biomass to obtain pulverized material for boiler combustion and outputs it. The primary air and secondary air inlets of the coal-fired boiler are used to introduce the boiler combustion powder output by the pulverizing device; The pyrolysis gas generated by the biomass torrefaction device and the flue gas after heat exchange are input into the main combustion zone of the coal-fired boiler to assist combustion; The pyrolysis gas generated by the biomass torrefaction device and the flue gas after heat exchange are input between the main combustion zone and the sofa air of the coal-fired boiler for reburning.

2. A biomass treatment system for large-scale consumption in power plants according to claim 1, characterized in that: A first exhaust pipe is provided at the economizer outlet of the coal-fired boiler. The first exhaust pipe is used to input flue gas to the flue gas inlet of the biomass roasting device. A first flow control valve is provided on the first exhaust pipe.

3. The biomass treatment system for large-scale consumption in power plants according to claim 1, characterized in that: The turning chamber of the coal-fired boiler is provided with a second exhaust pipe, which is used to input flue gas into the flue gas inlet of the biomass roasting device. The second exhaust pipe is provided with a second flow control valve.

4. The biomass treatment system for large-scale consumption in power plants according to claim 1, characterized in that: The extrusion and crushing device arranged inside the biomass roasting device is a spiral compression rod.

5. The biomass treatment system for large-scale consumption in power plants according to claim 1, characterized in that: It also includes a belt conveyor for transporting the roasted biomass from the material outlet of the biomass roasting device into the milling device.

6. The biomass treatment system for large-scale consumption in power plants according to claim 1, characterized in that: The flue gas and materials in the biomass roasting device adopt a countercurrent indirect contact heat exchange method.

7. A method for operating a biomass treatment system for large-scale consumption in a power plant, characterized in that: The following steps are involved: S1: The material inlet of the biomass torrefaction device is fed with biomass for power plant to be crushed and torrefied; S2: The extrusion and crushing device provided inside the biomass roasting device extrudes and crushes the input biomass; S3: Flue gas from a coal-fired boiler is introduced into the flue gas inlet of the biomass torrefaction device, and the flue gas creates an oxygen-deficient environment inside the biomass torrefaction device, and the torrefaction temperature reaches 200°C to 300°C; S4: The pyrolysis gas outlet of the biomass torrefaction device discharges the pyrolysis gas generated by torrefaction and the flue gas after heat exchange, and the material outlet of the biomass torrefaction device discharges the torrefied biomass; S5: The pulverizing device inputs coal and roasted biomass, dries and grinds the roasted biomass and coal into pulverized coal for boiler combustion, and outputs the pulverized coal; S6: The primary air and secondary air inlets of the coal-fired boiler are fed with the boiler combustion powder output by the pulverizing device for combustion.

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