A boiler biomass blending system

Abstract

The application discloses a boiler biomass blending combustion system, which comprises a boiler unit, a flue gas system loop, a primary air system loop, a biomass fuel system loop and a biomass blending combustion distribution valve group, wherein the flue gas system loop is communicated with the primary air system loop; the primary air system loop is communicated with the biomass fuel system loop; the biomass fuel system loop is communicated with at least two biomass blending combustion ports of the boiler unit through the biomass blending combustion distribution valve group, so as to control the biomass blending combustion quantity entering the biomass blending combustion ports; and the at least two biomass blending combustion ports comprise a first biomass blending combustion port arranged at a secondary air port of a furnace chamber of the boiler unit. The boiler biomass blending combustion system can improve the boiler dense phase zone temperature and enhance the low-load stable combustion capacity of the boiler by conveying finished biomass powder to the first biomass blending combustion port through a pneumatic conveying device in a deep regulation working condition.

Description

Technical Field

[0001] This application relates to the field of power system technology, and in particular to a boiler biomass co-firing system. Background Technology

[0002] Large-scale circulating fluidized bed (CFB) power units face a triple challenge: deep peak shaving, low-carbon emission reduction, and economical operation. Currently, when 300MW-class CFB units implement flue gas recirculation technology to extend peak shaving depth to 20% BMCR, problems arise such as insufficient low-load stable combustion capacity due to a 20-30℃ decrease in bed temperature, and increased fly ash carbon content leading to decreased combustion efficiency. Simultaneously, at 20% load, the furnace outlet flue gas temperature is below 750℃, causing the SNCR denitrification system to fail, thus failing to meet ultra-low NOx emission requirements. Regarding low-carbon retrofitting, biomass co-firing faces the dilemma of excessively high costs, and existing technologies struggle to synergistically optimize peak shaving depth, denitrification efficiency, and low-carbon economical operation.

[0003] Therefore, how to improve the stable combustion capability of boilers has become a technical problem that urgently needs to be solved by those skilled in the art. Utility Model Content

[0004] This application proposes a boiler biomass co-firing system to improve the boiler's stable combustion capability.

[0005] To achieve the above objectives, this application discloses the following technical solutions:

[0006] This application provides a boiler biomass co-firing system, including a boiler unit, a flue gas system circuit, a primary air system circuit, a biomass fuel system circuit, and a biomass co-firing distribution valve assembly.

[0007] The flue gas system loop is connected to the primary air system loop;

[0008] The primary air system loop is connected to the biomass fuel system loop;

[0009] The biomass fuel system loop is connected to at least two biomass co-firing ports of the boiler unit through the biomass co-firing distribution valve group to regulate the amount of biomass co-firing into the biomass co-firing ports.

[0010] At least two biomass co-firing ports include a first biomass co-firing port located at the secondary air inlet of the furnace of the boiler unit, a second biomass co-firing port located at the separator of the boiler unit, and a third biomass co-firing port located at the return feed inclined leg of the boiler unit.

[0011] In some embodiments, the boiler unit includes a furnace, a separator, an economizer, an air preheater, a dust collector, a desulfurization system, an induced draft fan, and a chimney connected in sequence, and a denitrification system is provided at the top of the furnace.

[0012] In some embodiments, the flue gas system loop includes a flue gas recirculation pipeline, a flue gas recirculation fan, a first flow measurement device, and a first electric valve. The flue gas recirculation fan, the first flow measurement device, and the first electric valve are connected in series in the flue gas recirculation pipeline. One end of the flue gas recirculation pipeline is connected to the induced draft fan, and the other end of the flue gas recirculation pipeline is connected to the primary air system loop. The first flow measurement device is used to measure the amount of flue gas recirculated in the flue gas recirculation pipeline, and the first electric valve is used to adjust the amount of flue gas recirculated in the flue gas recirculation pipeline.

[0013] In some embodiments, the primary air system loop includes a primary air duct, a primary air fan, and a delivery booster fan, wherein the primary air fan and the delivery booster fan are connected in series on the primary air duct, and the primary air duct is connected to the biomass fuel system loop.

[0014] In some embodiments, the biomass fuel system loop includes a biomass silo and a pneumatic conveying module. The biomass silo and the conveying booster fan are both connected to the inlet of the pneumatic conveying module, and the outlet of the pneumatic conveying module is connected to the biomass blending and distribution valve group.

[0015] In some embodiments, the biomass blending distribution valve group includes a first main valve, a second main valve, a third main valve, a first branch valve group, a second branch valve group, and a third branch valve group. The first main valve is connected to the first branch valve group, the second main valve is connected to the second branch valve group, and the third main valve is connected to the third branch valve group. The first branch valve group is connected to the first biomass blending port, the second branch valve group is connected to the second biomass blending port, and the third branch valve group is connected to the third biomass blending port.

[0016] In some embodiments, the secondary air inlets of the furnace are located on the front and rear walls of the furnace.

[0017] In some embodiments, the separator is a cyclone separator, and the second biomass co-firing port is arranged at the conical section of the separator.

[0018] In some embodiments, the number of return feed legs is three.

[0019] In some embodiments, a carbon monoxide monitoring device is also included at the economizer, and the secondary air volume of the furnace is increased when the detected carbon monoxide content reaches a preset range.

[0020] As can be seen from the above technical solution, the boiler biomass co-firing system of this application has a first biomass co-firing port located at the secondary air inlet of the boiler unit's furnace. Under deep-heating conditions, the finished biomass powder is transported to the first biomass co-firing port through a pneumatic conveying device, thereby increasing the temperature of the dense phase zone of the boiler and enhancing the boiler's low-load stable combustion capability. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some examples or embodiments of this application. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort, and this application can be applied to other similar scenarios based on the provided drawings. Unless obvious from the linguistic context or otherwise specified, the same reference numerals in the drawings represent the same structures or operations.

[0022] Figure 1 This is a schematic diagram of a boiler biomass co-firing system provided in an embodiment of this application;

[0023] Figure 2 This is a schematic diagram of a biomass co-firing distribution valve assembly provided in an embodiment of this application;

[0024] In the diagram: 11-Furnace; 12-Separator; 13-Economizer; 14-Air Preheater; 15-Dust Collector; 16-Desulfurization System; 17-Induced Draft Fan; 18-Chimney; 19-Denitrification System;

[0025] 21- Flue gas recirculation pipeline; 22- Flue gas recirculation fan; 23- First flow measurement device; 24- First electric valve

[0026] 31 - Primary air duct; 32 - Primary air fan; 33 - Booster fan;

[0027] 41-Biomass silo; 42-Pneumatic conveying module;

[0028] 5-Biomass blending distribution valve group; 51-First main valve; 52-Second main valve; 53-Third main valve; 54-First branch valve group; 55-Second branch valve group; 56-Third branch valve group;

[0029] 61-First biomass co-firing port; 62-Second biomass co-firing port; 63-Third biomass co-firing port;

[0030] 7. Carbon monoxide monitoring device. Detailed Implementation

[0031] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are merely illustrative of the application and not intended to limit it. The described embodiments are only a part of the embodiments of the present application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present application without inventive effort are within the scope of protection of the present application.

[0032] See Figures 1 to 2 To achieve the above objectives, this application discloses the following technical solutions:

[0033] A boiler biomass co-firing system includes a boiler unit, a flue gas system loop, a primary air system loop, a biomass fuel system loop, and a biomass co-firing distribution valve group. The flue gas system loop is connected to the primary air system loop; the primary air system loop is connected to the biomass fuel system loop; the biomass fuel system loop is connected to at least two biomass co-firing ports of the boiler unit through the biomass co-firing distribution valve group to regulate the amount of biomass entering the biomass co-firing ports; the at least two biomass co-firing ports include a first biomass co-firing port 61 arranged at the secondary air inlet of the furnace 11 of the boiler unit, a second biomass co-firing port 62 arranged at the separator 12 of the boiler unit, and a third biomass co-firing port 63 arranged at the return feed inclined leg of the boiler unit.

[0034] The biomass co-firing system of this application includes a first biomass co-firing port 61 located at the secondary air inlet of the furnace 11 of the boiler unit. During deep-heating operation, the finished biomass powder is conveyed to the first biomass co-firing port 61 via a pneumatic conveying device, increasing the temperature in the dense phase zone of the boiler and enhancing the boiler's stable combustion capability under low load. Furthermore, by co-firing biomass powder through the first biomass co-firing port 61, the pneumatic conveying airflow can be used to cool the first biomass co-firing port 61, avoiding the burn-out problem of the first biomass co-firing port 61 during deep-heating operation.

[0035] The second biomass co-firing port 62, located in the separator 12 of the boiler unit, reduces the carbon emission intensity of the unit through biomass co-firing, while leveraging the excellent ignition and burnout characteristics of biomass fuel. It adjusts the flue gas temperature in the separator 12 under deep-conditioning conditions to 750℃~950℃, improves the efficiency of the SNCR denitrification system under deep-conditioning conditions, and achieves ultra-low NOx emissions under deep-conditioning conditions.

[0036] The third biomass co-firing port 63 is located at the return feed inclined leg of the boiler unit. The structure of the boiler with coal feeding on the front wall and return feed on the rear wall results in a pattern where the combustion bed temperature is high near the front wall and low near the return feed port on the rear wall. Due to the reduced thickness of the feed layer under low load, the bed temperature deviation in the deep adjustment condition of the boiler is aggravated, and the bed temperature uniformity is even lower. The lowest point bed temperature is close to the protection lower limit, which limits the further reduction of boiler load.

[0037] After the biomass powder is fed into the return material inclined leg, it quickly participates in combustion with the return material ash through the third biomass co-firing port 63, increasing the return material temperature and achieving the effect of increasing the bed temperature in the area near the rear wall. This results in increasing the average bed temperature under low load conditions while reducing the temperature deviation between the front and rear walls.

[0038] The boiler unit mentioned above includes a furnace 11, a separator 12, an economizer 13, an air preheater 14, a dust collector 15, a desulfurization system 16, an induced draft fan 17, and a chimney 18 connected in sequence. A denitrification system 19 is installed at the top of the furnace 11.

[0039] The aforementioned flue gas system loop, used for heating primary air, may include a flue gas recirculation pipeline 21, a flue gas recirculation fan 22, a first flow measurement device 23, and a first electric valve 24. The flue gas recirculation fan 22, the first flow measurement device 23, and the first electric valve 24 are connected in series on the flue gas recirculation pipeline 21. One end of the flue gas recirculation pipeline 21 is connected to the induced draft fan 17, and the other end is connected to the primary air system loop. The first flow measurement device 23 measures the amount of flue gas recirculated in the flue gas recirculation pipeline 21, and the first electric valve 24 adjusts the amount of flue gas recirculated in the flue gas recirculation pipeline 21. By adjusting the flue gas recirculation rate, the oxygen content in the primary air can be reduced, thereby reducing the initial NOx formation in the boiler.

[0040] The primary air system loop is used to provide fresh air. For example, the primary air system loop includes a primary air duct 31, a primary air fan 32, and a delivery booster fan 33, wherein the primary air fan 32 and the delivery booster fan 33 are connected in series on the primary air duct 31, and the primary air duct 31 is connected to the biomass fuel system loop.

[0041] The biomass fuel system loop is used to provide biomass fuel. For example, the biomass fuel system loop includes a biomass silo 41 and a pneumatic conveying module 42. The biomass silo 41 and the conveying booster fan 33 are both connected to the inlet of the pneumatic conveying module 42, and the outlet of the pneumatic conveying module 42 is connected to the biomass blending and distribution valve group.

[0042] The pneumatic conveying module 42 mixes biomass fuel with air and conveys it in a pipeline through airflow. Its core is to use aerodynamics to overcome the gravity and friction of the material to achieve efficient and continuous transmission.

[0043] The pneumatic conveying module 42 is connected to the corresponding biomass co-firing port via a biomass co-firing distribution valve. Depending on the required adjustment of the oxygen content in the furnace, the pneumatic conveying module 42 can use either cold primary air mixed with circulating flue gas or coal-fired flue gas for conveying. A conveying booster fan 33 is installed to transport the biomass fuel from the biomass silo 41 to different co-firing positions, further reducing the oxygen content in the furnace under deep-adjustment conditions and controlling NOx generation.

[0044] The biomass blending distribution valve group 5 is used to regulate the mass of biomass entering the first biomass blending port 61, the second biomass blending port 62, and the third biomass blending port 63. The number of the first biomass blending port 61, the second biomass blending port 62, and the third biomass blending port 63 is at least one. When there are at least two of each of the first biomass co-firing port 61, the second biomass co-firing port 62, and the third biomass co-firing port 63, the biomass co-firing distribution valve group 5 includes a first main valve 51, a second main valve 52, a third main valve 53, a first branch valve group 54, a second branch valve group 55, and a third branch valve group 56. The first main valve 51 is connected to the first branch valve group 54, the second main valve 52 is connected to the second branch valve group 55, the third main valve 53 is connected to the third branch valve group 56, the first branch valve group 54 is connected to the first biomass co-firing port 61, the second branch valve group 55 is connected to the second biomass co-firing port 62, and the third branch valve group 56 is connected to the third biomass co-firing port 63. The three main groups are used to regulate the biomass mass entering the first branch valve group 54, the second branch valve group 55, and the third branch valve group 56. The first branch valve group 54 is used to regulate the biomass mass entering at least two first biomass co-firing ports 61, the second branch valve group 55 is used to regulate the biomass mass entering at least two second biomass co-firing ports 62, and the third branch valve group 56 is used to regulate the biomass mass entering at least three third biomass co-firing ports 63.

[0045] Based on the actual flue gas temperature inside the separator 12, the biomass co-firing quality entering the first biomass co-firing port 61, the second biomass co-firing port 62, and the third biomass co-firing port 63 is regulated by the biomass co-firing distribution valve group 5. The main control indicator is to increase the flue gas temperature in multiple biomass co-firing ports, and the secondary indicator is to increase the return material temperature. Ultimately, this improves the deep-tuning and stable combustion capability of the boiler unit and achieves ultra-low NOx emissions. In addition to regulating the bed temperature to improve the stable combustion capability, it can also increase the main reheat steam temperature of the boiler at low load, thereby improving the power generation efficiency and operational safety of the unit under low load conditions.

[0046] The principle behind setting the second biomass co-firing port 62 in the conical section of separator 12 has three aspects: First, the conical section of separator 12 is under negative pressure, resulting in high uniformity of flue gas mixing after biomass combustion. This allows for a rapid and uniform increase in the temperature of the coal-fired flue gas inside separator 12 to 750℃~950℃, thereby significantly improving the SNCR denitrification efficiency under low-load conditions. This, in turn, helps improve the efficiency of the in-furnace SNCR denitrification system 19, achieving ultra-low NOx emissions under deep-tuning conditions. Second, the wall ash concentration is relatively high at the conical section. The biomass jet co-firing can disturb the fine ash that has already been separated by inertia, causing it to re-enter the central upward flow of separator 12 and fly out of the central cylinder. This reduces the efficiency of cyclone separator 12, decreases the amount of material returned to separator 12 under low-load conditions (the return material temperature is usually lower than the bed temperature), and further improves the bed temperature and stable combustion capability of the boiler unit under low-load conditions. Thirdly, co-firing in the cone section of separator 12 can increase the flue gas temperature at the outlet of separator 12, and also increase the heat transfer flow of the superheater and reheater in the tail flue, thus optimizing the problem of low main steam and reheat steam temperatures in deep-conditioning large boiler units to a certain extent.

[0047] Biomass fuel is biomass powder / molded pellets (wide screening particle size range 0~8mm). Powder and small molten biomass have good ignition and burnout properties. In the case of a rapid increase in boiler load, the amount of biomass powder co-firing at the secondary air inlet can be increased to quickly improve the combustion temperature level in the furnace, thereby improving the unit's load increase response rate.

[0048] The main purpose of co-firing biomass powder in the 12 cone section of the separator is to reduce the carbon emission intensity of the unit by co-firing biomass fuel, while giving full play to the excellent ignition and burnout characteristics of biomass fuel, adjusting the flue gas temperature in the separator 12 under deep-conditioning conditions to 750℃~950℃, improving the efficiency of the SNCR denitrification system under deep-conditioning conditions, and stably achieving ultra-low NOx emissions under deep-conditioning conditions.

[0049] When the deep-tuning operation is adjusted only by combustion in the furnace, and the boiler cannot achieve ultra-low NOx emissions under load conditions below 20%, the biomass material at the second biomass co-firing port 62 is burned to raise the temperature inside the separator 12 to above 750°C, and the SNCR denitrification spray gun is put into operation. The NOx is further controlled to meet the ultra-low emission standards through the SNCR denitrification system.

[0050] The secondary air inlets of furnace 11 are distributed on the front and rear walls of furnace 11, while the third biomass co-firing inlet 63 is located on the front and rear walls of the boiler, increasing the temperature in the dense phase zone and enhancing the stable combustion capability under low load. Furthermore, the co-firing of biomass powder through the lower secondary air inlets allows for cooling of the lower secondary air nozzles using pneumatic conveying, preventing burn-out of the lower secondary air nozzles in deep-conditioning boilers. Biomass pneumatic conveying control valve groups and metering devices are installed on the front and rear walls respectively, allowing for dynamic control of the biomass powder co-firing amount at the secondary air inlets of the front and rear walls, which is beneficial for adjusting the bed temperature deviation between the front and rear walls of the boiler in deep-conditioning boilers.

[0051] A third biomass co-firing port 63 is provided on the return feed inclined leg corresponding to separator 12. After the biomass powder is fed into the return feed inclined leg, it quickly participates in combustion with the return feed ash, increasing the return feed temperature of the rear wall and effectively regulating the temperature deviation between the front and rear walls. At the same time, in view of the temperature difference in the return feed among multiple return feed inclined legs, the amount of biomass co-firing entering different return feed inclined legs can be adjusted by controlling the valve group according to the left and right deviation of the rear wall bed temperature, further controlling the bed temperature deviation along the left and right sides of the furnace 11.

[0052] The lower secondary air inlet and return material inclined leg biomass zero-carbon fuel co-firing system is used for rapid load increase of the boiler from low load conditions, improving the boiler's deep peak-shaving load change rate. During boiler load increase, the primary fluidizing air volume gradually increases, and the bed temperature shows a downward trend. At this time, using the co-firing system proposed in this utility model increases the amount of biomass co-firing in the dense phase zone of the furnace, improving the bed temperature rise rate. Compared to coal combustion, it can ignite and participate in combustion in the furnace more quickly, thereby improving the boiler's load change rate.

[0053] Considering the large amount of returned material and low bed temperature on the rear wall of the boiler, and the rapid temperature rise of the coal feeding bed on the front wall, the biomass co-firing amount at the third biomass co-firing port 63 at the returned material inclined leg is greater than that at the first biomass co-firing port 61 of the lower secondary air. It should be noted that the number of returned material inclined legs mentioned above is three.

[0054] The boiler biomass co-firing system of this application can operate simultaneously with the biomass fuel system loop and the flue gas system loop flue gas recirculation system, further reducing the oxygen content in the dense phase zone of the boiler load control.

[0055] In order to monitor the burnout of biomass zero-carbon fuel co-firing at the cone section of separator 12, a carbon monoxide monitoring device 7 is installed in the flue at the tail of the boiler to detect the CO content in the combustion flue gas. When the CO content is too high, it is proposed to increase the secondary air of the boiler by adjusting the combustion to increase the oxygen content at the outlet of furnace 11, thereby improving the degree of burnout.

[0056] Metering devices are installed on the biomass powder conveying pipelines at different locations to accurately calculate the reduction in carbon emissions from boiler co-firing.

[0057] In the above context, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature.

[0058] In the description of the embodiments of this application, unless otherwise stated, " / " means "or". For example, A / B can mean A or B. "And / or" in this article is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist simultaneously, and B exists alone.

[0059] It should be noted that, for ease of description, only the parts relevant to the application are shown in the accompanying drawings. Unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0060] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed, and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. The scope of this application is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the above-described application concept. For example, technical solutions formed by substituting the above features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. A boiler biomass co-firing system, characterized in that, This includes the boiler unit, flue gas system circuit, primary air system circuit, biomass fuel system circuit, and biomass co-firing distribution valve assembly. The flue gas system loop is connected to the primary air system loop; The primary air system loop is connected to the biomass fuel system loop; The biomass fuel system loop is connected to at least two biomass co-firing ports of the boiler unit through the biomass co-firing distribution valve group to regulate the amount of biomass co-firing into the biomass co-firing ports. At least two biomass co-firing ports include a first biomass co-firing port located at the secondary air inlet of the furnace of the boiler unit, a second biomass co-firing port located at the separator of the boiler unit, and a third biomass co-firing port located at the return feed inclined leg of the boiler unit.

2. The boiler biomass co-firing system as described in claim 1, characterized in that, The boiler unit includes a furnace, separator, economizer, air preheater, dust collector, desulfurization system, induced draft fan and chimney connected in sequence, and a denitrification system is installed at the top of the furnace.

3. The boiler biomass co-firing system as described in claim 2, characterized in that, The flue gas system loop includes a flue gas recirculation pipeline, a flue gas recirculation fan, a first flow measurement device, and a first electric valve. The flue gas recirculation fan, the first flow measurement device, and the first electric valve are connected in series in the flue gas recirculation pipeline. One end of the flue gas recirculation pipeline is connected to the induced draft fan, and the other end of the flue gas recirculation pipeline is connected to the primary air system loop. The first flow measurement device is used to measure the amount of flue gas recirculated in the flue gas recirculation pipeline, and the first electric valve is used to adjust the amount of flue gas recirculated in the flue gas recirculation pipeline.

4. The boiler biomass co-firing system as described in claim 3, characterized in that, The primary air system loop includes a primary air duct, a primary air fan, and a conveying and boosting fan, wherein the primary air fan and the conveying and boosting fan are connected in series on the primary air duct, and the primary air duct is connected to the biomass fuel system loop.

5. The boiler biomass co-firing system as described in claim 4, characterized in that, The biomass fuel system loop includes a biomass silo and a pneumatic conveying module. The biomass silo and the conveying booster fan are both connected to the inlet of the pneumatic conveying module, and the outlet of the pneumatic conveying module is connected to the biomass blending and distribution valve group.

6. The boiler biomass co-firing system as described in claim 4, characterized in that, The biomass blending distribution valve group includes a first main valve, a second main valve, a third main valve, a first branch valve group, a second branch valve group, and a third branch valve group. The first main valve is connected to the first branch valve group, the second main valve is connected to the second branch valve group, and the third main valve is connected to the third branch valve group. The first branch valve group is connected to the first biomass blending port, the second branch valve group is connected to the second biomass blending port, and the third branch valve group is connected to the third biomass blending port.

7. The boiler biomass co-firing system as described in claim 6, characterized in that, The secondary air inlets of the furnace are located on the front and rear walls of the furnace.

8. The boiler biomass co-firing system as described in claim 6, characterized in that, The separator is a cyclone separator, and the second biomass co-firing port is located at the conical section of the separator.

9. The boiler biomass co-firing system as described in claim 6, characterized in that, The number of return material inclined legs is three.

10. The boiler biomass co-firing system as described in any one of claims 2 to 9, characterized in that, It also includes a carbon monoxide monitoring device installed at the economizer, which increases the secondary air volume in the furnace when the detected carbon monoxide content reaches a preset range.

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