A biomass oxygenated upgrading system based on flue gas and control method

Abstract

The application discloses a biomass aerobic upgrading system based on flue gas and a control method. The biomass aerobic upgrading system comprises a coal-fired boiler, a biomass upgrading device, a flue gas mixer and a separator. The coal-fired boiler is provided with a flue gas combustion port, a burner and a flue. The flue is provided with a flue gas taking port. The flue gas mixer is provided with an air inlet, a flue gas inlet and a mixed gas outlet. The biomass upgrading device is provided with a mixed gas inlet, a biomass inlet and a biomass outlet. The separator is provided with a solid material inlet, a solid material outlet and a flue gas outlet. The flue gas inlet of the flue gas mixer is communicated with the flue gas taking port. The mixed gas outlet of the flue gas mixer is communicated with the mixed gas inlet of the biomass upgrading device. The biomass outlet of the biomass upgrading device is communicated with the solid material inlet of the separator. The flue gas outlet is communicated with the flue gas combustion port. The solid material outlet of the separator is communicated with the burner. In this way, high-proportion mixed combustion of biomass particles and coal materials can be realized.

Description

Technical Field

[0001] This invention belongs to the field of coal-fired power generation and thermal energy production, and particularly relates to a biomass aerobic upgrading system and control method based on flue gas. Background Technology

[0002] For coal-fired boilers, biomass blending is a crucial technology for reducing CO2 emissions. While simple blending allows for small-scale biomass blending, large-scale biomass blending presents several significant challenges. Due to its high volatile matter content, low ash content, and low ignition point, biomass is prone to deflagration. Traditional blending processes primarily utilize pneumatic conveying to blow biomass into the boiler burner through the pulverizing system. This method uses air, which has a low temperature, and at high blending ratios, it can significantly impact boiler combustion, thus reducing boiler efficiency. Furthermore, existing coal mills in the pulverizing system are poorly adapted to biomass fuels with low rigidity and grindability; directly using the existing pulverizing system to crush biomass would result in enormous power consumption and poor economic efficiency. In addition, because biomass has a significantly higher volatile matter content than coal, large-scale blending requires separate pulverizing and combustion systems for safe operation. This creates redundancy between the new and existing systems, leading to high investment and operating costs and impacting the safe and flexible operation of the boiler.

[0003] Currently, document CN215637122U, "A Biomass Blending System for Coal-fired Boilers," discloses introducing low-oxygen, high-temperature flue gas into a separate pulverizing system for drying and crushing biomass, followed by combustion in a separate biomass burner. However, high-temperature biomass crushing poses significant safety hazards, requires substantial system modifications, and has a significant impact on the boiler system. Document CN212901472U, "A Biomass Blending System Based on Flue Gas Recirculation in Coal-fired Power Plants," utilizes flue gas to transport crushed biomass particles into the boiler for combustion. This flue gas recirculation incineration method achieves clean treatment of biomass solid waste and helps prevent deflagration during transport. However, it still requires additional equipment... Standalone biomass crushing equipment uses flue gas only as a carrier gas, resulting in low heat utilization of the flue gas. Furthermore, the significant differences between biomass and coal can negatively impact boiler performance during combustion. The aforementioned literature all focuses on biomass co-firing using separate crushing and combustion equipment. High-proportion co-firing leads to high initial equipment investment costs and fails to address issues such as high biomass volatile matter and poor abrasion resistance during co-firing. While the literature utilizes flue gas for drying and transportation, it doesn't fully leverage the heat in the flue gas for biomass processing. A significant challenge lies in utilizing the heat and oxygen in flue gas to reduce biomass volatile matter, improve its calorific value and grindability, and meet the safe and stable operation requirements of coal-fired boiler pulverization and combustion systems. Summary of the Invention

[0004] In order to solve the above-mentioned technical problems, the purpose of this invention is to provide a flue gas-based aerobic biomass upgrading system that can utilize the heat provided by flue gas from a coal-fired boiler to upgrade biomass before co-firing it with coal.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows: A biomass aerobic upgrading system based on flue gas, comprising a coal-fired boiler, a biomass upgrader, a flue gas mixer, and a separator. The coal-fired boiler has a waste gas combustion port, a burner, and a flue. The flue has a flue gas intake port. The flue gas mixer has an air inlet, a flue gas inlet, and a mixed gas outlet, used to mix flue gas and air to form a mixed gas. The biomass upgrader has a mixed gas inlet, a biomass inlet, and a biomass outlet, used to upgrade biomass pellets. The separator has a solid material inlet, a solid material outlet, and a waste gas outlet. The flue gas inlet of the flue gas mixer is connected to the flue gas intake port via a first induced draft fan. A second induced draft fan is installed at the air inlet of the flue gas mixer. The mixed gas outlet of the flue gas mixer is connected to the mixed gas inlet of the biomass upgrader. The biomass outlet of the biomass upgrader is connected to the solid material inlet of the separator. The waste gas outlet is connected to the waste gas combustion port via a third induced draft fan. The solid material outlet of the separator is connected to the burner.

[0006] The beneficial effects of the above technical solution are as follows: In this way, part of the flue gas in the flue of the coal-fired boiler can be extracted and mixed with air to form a mixed gas, which is then supplied to the biomass upgrader. At this time, the biomass pellets are upgraded in the biomass upgrader under the action of the mixed gas (drying, and undergoing a slight gasification reaction, etc.). During the upgrade process, exhaust gas is generated, which is then separated into gas and solid by a separator. The separated exhaust gas is discharged into the flue through the exhaust gas combustion port, while the upgraded solid biomass pellets are supplied to the furnace of the coal-fired boiler for combustion.

[0007] The coal-fired boiler described in the above technical solution is a four-corner tangential coal-fired boiler, and the exhaust gas combustion port is arranged at the uppermost secondary air or separate burnout air; or the coal-fired boiler is a counter-firing boiler, and the exhaust gas combustion port is arranged at the same horizontal position as the uppermost burner in the furnace.

[0008] The beneficial effect of the above technical solution is that it allows the exhaust gas to be sent into the flue without being ignited, which would cause the flame to flow back into the separator.

[0009] The biomass pellets described in the above technical solution have a moisture content of no more than 20%, a volatile matter content of no more than 90%, and a calorific value of no less than 13 MJ / kg.

[0010] The beneficial effects of the above technical solution are as follows: limiting the moisture content of biomass pellets to no more than 20% avoids excessive heat absorption during the upgrading process due to high moisture content (which would lower the temperature in the biomass upgrader and thus affect the overall upgrading effect); limiting the volatile matter content of biomass pellets to no more than 70% avoids high volatile matter content in the later stages of upgrading (high volatile matter content after upgrading could lead to explosions when the biomass is subsequently ground with coal powder); and if the calorific value of the biomass pellets is lower than 13 MJ / kg, it would affect its use as fuel.

[0011] The above technical solution also includes a coal mill, which includes a solid material inlet, a powder material outlet and an air inlet. The solid material outlet of the separator is connected to the solid material inlet of the coal mill, the powder material outlet of the coal mill is connected to the burner, and the air inlet is used to introduce primary air and / or air. The coal mill is used to mix and grind coal with upgraded biomass.

[0012] The beneficial effect of the above technical solution is that it enables the upgraded solid biomass pellets to be ground and fully mixed with coal powder in the coal mill before being supplied to the furnace of the coal-fired boiler for combustion.

[0013] In the above technical solution, the biomass particles in the coal mill account for more than 15% of the total fuel mass.

[0014] The beneficial effect of the above technical solution is that it can achieve the proportion of biomass pellets added to partially replace coal powder as fuel, thereby realizing the rational utilization of resources.

[0015] The air inlet in the above technical solution is connected to a primary air duct and an air duct, and a fourth exhaust fan is installed at the air duct.

[0016] The beneficial effect of the above technical solution is that it enables the mixed fuel of pulverized coal and biomass to be purged into the coal-fired boiler by primary air and / or air for combustion.

[0017] In the above technical solution, an economizer and an air preheater are arranged sequentially along the flue gas flow direction in the flue gas duct. Three flue gas inlets are arranged sequentially along the flue gas flow direction, namely a first flue gas inlet, a second flue gas inlet, and a third flue gas inlet. The economizer is located between the first and second flue gas inlets, and the air preheater is located between the second and third flue gas inlets. The three flue gas inlets merge and are connected to the flue gas inlet of the flue gas mixer.

[0018] The beneficial effect of the above technical solution is that by setting three flue gas inlets, the temperature and oxygen content of the mixture can be adjusted in a coordinated manner by regulating the flue gas flow rate and air supply flow rate at each flue gas inlet.

[0019] The flue gas mixer described in the above technical solution is provided with a first flow valve at the air inlet, a second flow valve at the first flue gas outlet, a third flow valve at the second flue gas outlet, and a fourth flow valve at the third flue gas outlet. By adjusting the opening and closing degrees of the first, second, third, and fourth flow valves, mixed gases of different phases can be prepared.

[0020] The beneficial effect of the above technical solution is that the temperature and oxygen content of the mixed gas can be adjusted by regulating the opening and closing degree of the first flow valve, the second flow valve, the third flow valve and the fourth flow valve.

[0021] Temperature measuring elements and oxygen content analyzers are installed at the mixed gas inlet of the biomass upgrader, the air inlet of the flue gas mixer, the first flue gas outlet, the second flue gas outlet, and the third flue gas outlet in the above technical solution.

[0022] The beneficial effect of the above technical solution is that the temperature and oxygen content of the airflow at the mixed gas inlet of the biomass upgrader, the air inlet of the flue gas mixer, the first flue gas outlet, the second flue gas outlet, and the third flue gas outlet can be monitored in real time.

[0023] The second objective of this invention is to provide a method for conditioning the mixed gas in a biomass aerobic upgrading system based on flue gas.

[0024] To achieve the above objectives, another technical solution of the present invention is as follows: a control method for the biomass aerobic upgrading system based on flue gas as described above, wherein the actual flow rates of the air inlet, first flue gas inlet, second flue gas inlet, and third flue gas inlet of the flue gas mixer must meet the following conditions during the regulation of the mixed gas:

[0025]

[0026] Q std =Q std,1 +Q std,2 +Q std,3 +Q std,4 ;

[0027] αQ std =α1Q std,1 +α2Q std,2 +α3Q std,3 +α4Q std,4 ;

[0028]

[0029] Among them, P std The pressure under standard conditions, P std =101.325 kPa;

[0030] T std T represents the temperature under standard conditions. std =273.15K;

[0031] Q std Q std,1 Q std,2 Q std,3 Q std,4 These are the flow rates (in Nm³) of the mixed gas, the air inlet of the flue gas mixer, the first flue gas inlet, the second flue gas inlet, and the third flue gas inlet under standard conditions. 3 / h;

[0032] Q, Q1, Q2, Q3, and Q4 represent the actual flow rates (in m) at the air inlet, first flue gas inlet, second flue gas inlet, and third flue gas inlet of the gas-mixture and flue gas mixer, respectively. 3 / h;

[0033] P, P1, P2, P3, and P4 are the actual pressures (kPa) at the air inlet, first flue gas outlet, second flue gas outlet, and third flue gas outlet of the mixed gas and flue gas mixer, respectively.

[0034] T, T1, T2, T3, and T4 are the actual temperatures, in K, of the air inlet, first flue gas outlet, second flue gas outlet, and third flue gas outlet of the mixed gas and flue gas mixer, respectively.

[0035] α, α1, α2, α3, and α4 are the oxygen contents (%) at the air inlet, first flue gas outlet, second flue gas outlet, and third flue gas outlet of the mixed gas and flue gas mixer, respectively.

[0036] c p1 c p2 c p3 c p4 These are the isobaric specific heat capacities of the air inlet, first flue gas outlet, second flue gas outlet, and third flue gas outlet of the flue gas mixer under standard conditions, in kJ / (m³). 3 ·K).

[0037] The beneficial effect of the above technical solution is that the supply flow of air and flue gas at each point in the flue gas mixer can be optimized through the above formula to meet the air and temperature requirements of the mixed gas. Attached Figure Description

[0038] Figure 1This is a schematic diagram of the structure of the biomass aerobic upgrading system based on flue gas according to an embodiment of the present invention.

[0039] In the diagram: 1. Coal-fired boiler; 11. Exhaust gas combustion port; 12. Burner; 13. Flue; 131. Flue gas intake port; 1311. First flue gas intake port; 1312. Second flue gas intake port; 1313. Third flue gas intake port; 132. Economizer; 133. Air preheater; 2. Biomass upgrader; 3. Flue gas mixer; 4. Separator; 51. First induced draft fan; 52. Second induced draft fan; 53. Third induced draft fan; 6. Coal mill; 61. Primary air duct; 62. Air duct; 63. Fourth induced draft fan; 71. First flow valve; 72. Second flow valve; 73. Third flow valve; 74. Fourth flow valve; 75. Temperature measuring element; 76. Oxygen content analyzer; 8. Conveyor; 9. Chimney. Detailed Implementation

[0040] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are for illustrative purposes only and are not intended to limit the scope of the invention. The invention is described more specifically in the following paragraphs by way of example with reference to the accompanying drawings. The advantages and features of the invention will become clearer from the following description and claims. It should be noted that the drawings are in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the invention.

[0041] Example 1

[0042] like Figure 1As shown, this embodiment provides a biomass aerobic upgrading system based on flue gas, including a coal-fired boiler 1, a biomass upgrader 2, a flue gas mixer 3, and a separator 4. The coal-fired boiler 1 has an exhaust gas combustion port 11, a burner 12, and a flue duct 13. The flue duct 13 has a flue gas intake port 131. The flue gas mixer 3 has an air inlet, a flue gas inlet, and a mixed gas outlet, which is used to mix flue gas and air to form a mixed gas. The biomass upgrader 2 has a mixed gas inlet, a biomass inlet, and a biomass outlet, which is used to upgrade biomass pellets. The separator 4 has a solid material inlet, a solid material outlet, and an exhaust gas outlet. The flue gas inlet of the flue gas mixer 3 is connected to the flue gas intake port 131 through a first induced draft fan 51. A second induced draft fan 52 is provided at the air inlet of the flue gas mixer 3. The mixed gas outlet of the flue gas mixer 3 is connected to the mixed gas inlet of the biomass upgrader 2, the biomass outlet of the biomass upgrader 2 is connected to the solid material inlet of the separator 4, the exhaust gas outlet is connected to the exhaust gas combustion port 11 through the third induced draft fan 53, and the solid material outlet of the separator 4 is connected to the burner 12. In this way, part of the flue gas in the flue of the coal-fired boiler can be taken out and mixed with air to form a mixed gas, which is then supplied to the biomass upgrader. At this time, the biomass pellets are upgraded in the biomass upgrader under the action of the mixed gas (drying, and at the same time undergoing a slight gasification reaction, etc.). During the upgrading process, exhaust gas is generated, which is then separated into gas and solid by the separator. The separated exhaust gas is discharged into the flue through the exhaust gas combustion port, while the upgraded solid biomass pellets are supplied to the furnace of the coal-fired boiler for combustion.

[0043] In this embodiment, the end of the flue is connected to a chimney 9.

[0044] In the above technical solution, the solid material outlet of the separator 4 is connected to the burner 12 via a coal mill 6. The coal mill 6 includes a solid material inlet, a powder material outlet, and an air inlet. The solid material outlet of the separator 4 is connected to the solid material inlet of the coal mill 6, and the powder material outlet of the coal mill 6 is connected to the burner 12. The air inlet is used to introduce primary air and / or air. The coal mill 6 is used to mix and pulverize the coal with the upgraded biomass. This allows the upgraded solid biomass particles to be ground and fully mixed with the coal powder in the coal mill before being supplied to the furnace of the coal-fired boiler for combustion.

[0045] In the above technical solution, an economizer 132 and an air preheater 133 are sequentially arranged in the flue gas duct 13 along the flue gas flow direction. Three flue gas inlets 131 are sequentially arranged along the flue gas flow direction, namely a first flue gas inlet 1311, a second flue gas inlet 1312, and a third flue gas inlet 1313. The economizer 132 is located between the first flue gas inlet 1311 and the second flue gas inlet 1312, and the air preheater 133 is located between the second flue gas inlet 1312 and the third flue gas inlet 1313. The three flue gas inlets 131 merge and are connected to the flue gas inlet of the flue gas mixer 3. By setting three flue gas inlets, the temperature and oxygen content of the mixed gas can be synergistically adjusted by regulating the flue gas flow rate and the air supply flow rate at each flue gas inlet.

[0046] In the above technical solution, a first flow valve 71 is provided at the air inlet or outlet of the second induced draft fan 52, a second flow valve 72 is provided at the first flue gas outlet 1311, a third flow valve 73 is provided at the second flue gas outlet 1312, and a fourth flow valve 74 is provided at the third flue gas outlet 1313. By adjusting the opening and closing degrees of the first flow valve 71, the second flow valve 72, the third flow valve 73, and the fourth flow valve 74, mixed gases of different phases can be prepared. Thus, the temperature and oxygen content of the mixed gas can be adjusted by adjusting the opening and closing degrees of the first flow valve 71, the second flow valve 72, the third flow valve 73, and the fourth flow valve 74.

[0047] In the above technical solution, temperature measuring elements 75 and oxygen content analyzers 76 are installed at the mixed gas inlet of the biomass upgrader 2, the air inlet of the flue gas mixer 3, the first flue gas outlet 1311, the second flue gas outlet 1312, and the third flue gas outlet 1313. This allows the temperature and oxygen content of the airflow at the mixed gas inlet of the biomass upgrader 2, the air inlet of the flue gas mixer 3, the first flue gas outlet 1311, the second flue gas outlet 1312, and the third flue gas outlet 1313 to be monitored in real time.

[0048] The coal-fired boiler 1 described in the above technical solution is a tangentially rounded coal-fired boiler, and the exhaust gas combustion port 11 is arranged at the uppermost secondary air or separate burnout air; or the coal-fired boiler 1 is a counter-firing boiler, and the exhaust gas combustion port 11 is arranged at the same horizontal position as the uppermost burner 12 in the furnace, so that the exhaust gas can be sent into the flue and will not be ignited, causing the flame to flow back into the separator.

[0049] The biomass pellets described in the above technical solution have a moisture content not exceeding 90%, a volatile matter content not exceeding 90%, and a calorific value not less than 13 MJ / kg. Limiting the moisture content of the biomass pellets to no more than 20% avoids excessive heat absorption during the upgrading process due to high moisture content (which would lower the temperature in the biomass upgrader and thus affect the overall upgrading effect). Limiting the volatile matter content of the biomass pellets to no more than 90% avoids high volatile matter content in the later stages of upgrading (high volatile matter content after upgrading could lead to explosions when the biomass is subsequently ground with coal powder). If the calorific value of the biomass pellets is less than 13 MJ / kg, it would affect its use as fuel.

[0050] In the above technical solution, the biomass pellets in the coal mill 6 account for more than 15% of the total fuel mass. This allows for the proportional addition of biomass pellets to partially replace pulverized coal as fuel, thereby achieving the rational utilization of resources.

[0051] In the above technical solution, the air inlet is connected to a primary air duct 61 and an air duct 62, and a fourth induced draft fan 63 is installed at the air duct 62, so that the mixed fuel of pulverized coal and biomass can be blown into the coal-fired boiler by primary air and / or air for combustion.

[0052] In this embodiment, the solid material outlet of the separator 4 and the solid material inlet of the coal mill 6 can be connected by a conveyor (the conveyor can be a belt conveyor). In this case, the biomass pellets discharged from the separator can be cooled on the conveyor to prevent the biomass pellets from entering the coal mill and causing a safety accident due to the high temperature.

[0053] In this embodiment, coal material also needs to be introduced into the solid material inlet of the coal mill. Figure 1 Biomass pellets are introduced at point A, air is introduced at points B and E, coal is introduced at point C, and primary air is introduced at point D.

[0054] In this embodiment, "primary air" and "secondary air" are existing concepts in the field of boiler technology and will not be elaborated here.

[0055] In this embodiment, the separator can be a cyclone separator, the temperature measuring element can be a temperature sensor, and the oxygen content analyzer is an existing product, which will not be described in detail here.

[0056] Example 2

[0057] This embodiment provides a control method for a biomass aerobic upgrading system based on flue gas as described in Embodiment 1. When regulating the mixed gas, the actual flow rates of the air inlet, first flue gas inlet 1311, second flue gas inlet 1312, and third flue gas inlet 1313 of the flue gas mixer 3 must meet the following conditions:

[0058]

[0059] Q std =Q std,1 +Q std,2 +Q std,3 +Q std,4 ;

[0060] αQ std =α1Q std,1 +α2Q std,2 +α3Q std,3 +α4Q std,4 ;

[0061]

[0062] Among them, P std The pressure under standard conditions, P std =101.325 kPa; T std T represents the temperature under standard conditions. std =273.15K; Q std Q std,1 Q std,2 Q std,3 Q std,4 These are the flow rates (in Nm) of the mixed gas, the air inlet of the flue gas mixer 3, the first flue gas inlet 1311, the second flue gas inlet 1312, and the third flue gas inlet 1313 under standard conditions. 3 / h; Q, Q1, Q2, Q3, and Q4 are the actual flow rates (m³) of the mixed gas, the air inlet of the flue gas mixer 3, the first flue gas inlet 1311, the second flue gas inlet 1312, and the third flue gas inlet 1313, respectively. 3 / h; P, P1, P2, P3, and P4 are the actual pressures (kPa) at the air inlet, first flue gas outlet 1311, second flue gas outlet 1312, and third flue gas outlet 1313 of the mixed gas and flue gas mixer 3, respectively; T, T1, T2, T3, and T4 are the actual temperatures (K) at the air inlet, first flue gas outlet 1311, second flue gas outlet 1312, and third flue gas outlet 1313 of the mixed gas and flue gas mixer 3, respectively; α, α1, α2, α3, and α4 are the oxygen contents (%) at the air inlet, first flue gas outlet 1311, second flue gas outlet 1312, and third flue gas outlet 1313 of the mixed gas and flue gas mixer 3, respectively; c p1 cp2 c p3 c p4 These are the isobaric specific heat capacities of the air inlet, first flue gas inlet 1311, second flue gas inlet 1312, and third flue gas inlet 1313 of the flue gas mixer 3 under standard conditions, in kJ / (m³). 3 ·K), c p1 ≈c p2 ≈c p3 ≈c p4 Thus, the supply flow rates of air and flue gas at each point in the flue gas mixer can be optimized using the above formula to meet the air and temperature requirements of the mixture.

[0063] Specific examples:

[0064] like Figure 1 As shown, in a certain flue gas-based biomass aerobic upgrading system, the coal-fired boiler is a 660MW tangential combustion boiler. Taking pine wood as an example, the pine wood is crushed to a particle size of 1-3mm and then added to the biomass upgrading device. The mixed gas has an oxygen content of 6% and its temperature is 300℃. The temperature of the upgraded biomass particles in the coal mill needs to be reduced to 50℃.

[0065] The calculation process for controlling key parameters (oxygen content and temperature) in the biomass pellet upgrading process of this flue gas-based aerobic biomass upgrading system is as follows:

[0066] The biomass sample was pine wood, with a measured volatile matter content of approximately 84%, classifying it as high-volatile biomass. The estimated processing capacity is 120 kg / h, and the total flow rate of the mixed flue gas is 12 m³ / h. 3 / h, during the pine wood refining process, the oxygen content of the mixed gas is set at 6%, the temperature at 300℃, and the pressure approximately equal to atmospheric pressure. The oxygen content in the air is approximately 21%, the temperature at 25℃, and the pressure at approximately 101.325 kPa. Detection revealed that the oxygen content at the first flue gas intake was 5%, the temperature at 350℃, and the pressure at 100 kPa; the oxygen content at the second flue gas intake was 6%, the temperature at 250℃, and the pressure at 95 kPa; and the oxygen content at the third flue gas intake was 8%, the temperature at 120℃, and the pressure at 90 kPa. The original equation, simplified, yields:

[0067]

[0068] PQ = P1Q1 + P2Q2 + P3Q3 + P4Q4;

[0069] Substitute the coefficients,

[0070]

[0071] 101.325*12=101.325*Q1+95*Q2+100*Q3+90*Q4;

[0072] Numerical solutions yielded:

[0073] Q1 = 0.2375 - 0.0381Q4;

[0074] Q2 = 8.093 + 1.7643Q4;

[0075] Q3 = 4.23 - 2.5375Q4;

[0076] The following conditions must also be met:

[0077] 0≤Q1,Q2,Q3,Q4≤12:

[0078] Therefore, 0 ≤ Q4 ≤ 1.67, and the range is adjustable.

[0079] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Those skilled in the art can readily implement the present invention based on the accompanying drawings and the above description. However, any modifications, alterations, or variations made by those skilled in the art without departing from the scope of the present invention, utilizing the disclosed technical content, are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, or variations made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the present invention.

Claims

1. A biomass aerobic upgrading system based on flue gas, characterized in that, The system includes a coal-fired boiler (1), a biomass upgrader (2), a flue gas mixer (3), and a separator (4). The coal-fired boiler (1) has a waste gas combustion port (11), a burner (12), and a flue (13). The flue (13) has a flue gas intake port (131). The flue gas mixer (3) has an air inlet, a flue gas inlet, and a mixed gas outlet, which is used to mix flue gas and air to form a mixed gas with adjustable oxygen content and temperature. The biomass upgrader (2) has a mixed gas inlet, a biomass inlet, and a biomass outlet, which is used to perform aerobic upgrading of biomass particles under adjustable oxygen content and temperature. The separator (4) It has a solid material inlet, a solid material outlet and a waste gas outlet. The flue gas inlet of the flue gas mixer (3) is connected to the flue gas intake port (131) through a first induced draft fan (51). A second induced draft fan (52) is provided at the air inlet of the flue gas mixer (3). The mixed gas outlet of the flue gas mixer (3) is connected to the mixed gas inlet of the biomass upgrader (2). The biomass outlet of the biomass upgrader (2) is connected to the solid material inlet of the separator (4). The waste gas outlet is connected to the waste gas combustion port (11) through a third induced draft fan (53). The solid material outlet of the separator (4) is connected to the burner (12). An economizer (132) and an air preheater (133) are arranged sequentially along the flue gas flow direction in the flue gas duct (13). Three flue gas inlets (131) are arranged sequentially along the flue gas flow direction, namely a first flue gas inlet (1311), a second flue gas inlet (1312), and a third flue gas inlet (1313). The economizer (132) is located between the first flue gas inlet (1311) and the second flue gas inlet (1312). The air preheater (133) is located between the second flue gas inlet (1312) and the third flue gas inlet (1313). The three flue gas inlets (131) merge and are connected to the flue gas inlet of the flue gas mixer (3). The flue gas mixer (3) is provided with a first flow valve (71) at the air inlet, a second flow valve (72) at the first flue gas outlet (1311), a third flow valve (73) at the second flue gas outlet (1312), and a fourth flow valve (74) at the third flue gas outlet (1313). By adjusting the opening and closing degree of the first flow valve (71), the second flow valve (72), the third flow valve (73), and the fourth flow valve (74), mixed gases of different phases can be prepared. Temperature measuring elements (75) and oxygen content analyzers (76) are provided at the mixed gas inlet of the biomass improver (2), the air inlet of the flue gas mixer (3), the first flue gas outlet (1311), the second flue gas outlet (1312) and the third flue gas outlet (1313).

2. The biomass aerobic upgrading system based on flue gas according to claim 1, characterized in that, The coal-fired boiler (1) is a four-corner tangential coal-fired boiler, and the exhaust gas combustion port (11) is arranged at the uppermost secondary air or separate burnout air; or the coal-fired boiler (1) is a counter-firing boiler, and the exhaust gas combustion port (11) is arranged at the same horizontal position as the uppermost burner (12) in the furnace.

3. The biomass aerobic upgrading system based on flue gas according to claim 1, characterized in that, The biomass pellets have a moisture content of no more than 20%, a volatile matter content of no more than 90%, and a calorific value of no less than 13 MJ / kg.

4. The biomass aerobic upgrading system based on flue gas according to claim 1, characterized in that, It also includes a coal mill (6), which includes a solid material inlet, a powder material outlet and an air inlet. The solid material outlet of the separator (4) is connected to the solid material inlet of the coal mill (6), and the powder material outlet of the coal mill (6) is connected to the burner (12). The air inlet is used to introduce primary air and / or air. The coal mill (6) is used to mix coal with upgraded biomass to make pulverized coal.

5. The biomass aerobic upgrading system based on flue gas according to claim 4, characterized in that, The biomass particles in the coal mill (6) account for more than 15% of the total fuel mass.

6. The biomass aerobic upgrading system based on flue gas according to claim 4, characterized in that, The air inlet is connected to a primary air duct (61) and an air duct (62), and a fourth induced draft fan (63) is installed at the air duct (62).

7. A control method for a biomass aerobic upgrading system based on flue gas as described in any one of claims 1-6, characterized in that, When the mixture is regulated, the actual flow rates of the air inlet, the first flue gas inlet (1311), the second flue gas inlet (1312), and the third flue gas inlet (1313) of the flue gas mixer (3) must meet the following conditions: ； ； ； ； ； ； ； ； Among them, P std The pressure under standard conditions, P std =101.325 kPa; T std T represents the temperature under standard conditions. std =273.15K; Q std Q std,1 Q std,2 Q std,3 Q std,4 These are the flow rates (Nm³) of the mixed gas, the air inlet of the flue gas mixer (3), the first flue gas inlet (1311), the second flue gas inlet (1312), and the third flue gas inlet (1313) under standard conditions. 3 / h; Q, Q1, Q2, Q3, and Q4 are the actual flow rates (m) of the air inlet, first flue gas inlet (1311), second flue gas inlet (1312), and third flue gas inlet (1313) of the gas-mixed mixture and flue gas mixer (3), respectively. 3 / h; P, P1, P2, P3, and P4 are the actual pressures (kPa) of the air inlet, first flue gas inlet (1311), second flue gas inlet (1312), and third flue gas inlet (1313) of the mixed gas and flue gas mixer (3), respectively. T, T1, T2, T3, and T4 are the actual temperatures, in K, of the air inlet, the first flue gas inlet (1311), the second flue gas inlet (1312), and the third flue gas inlet (1313) of the mixed gas and flue gas mixer (3); α, α1, α2, α3, and α4 are the oxygen contents (%) of the air inlet, first flue gas inlet (1311), second flue gas inlet (1312), and third flue gas inlet (1313) of the mixed gas and flue gas mixer (3), respectively. c p1 c p2 c p3 c p4 These are the isobaric specific heat capacities of the air inlet, first flue gas inlet (1311), second flue gas inlet (1312), and third flue gas inlet (1313) of the flue gas mixer (3) under standard conditions, in kJ / (m³). 3 ·K).

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