Biomass pyrolysis system and coal-fired power plant

Abstract

The invention relates to the technical field of biomass pyrolysis, in particular to a biomass pyrolysis system and a coal-fired power plant. The biomass pyrolysis system comprises a pyrolysis device, a heat exchanger and an induced draft fan; the air inlet end of the induced draft fan is used for being connected with a smoke outlet of a flue of a boiler. The temperature of the flue gas at the position where the heat exchanger is located is larger than or equal to 300 DEG C and smaller than or equal to 400 DEG C; the air outlet end of the induced draft fan is communicated with the air inlet end of the heat exchanger, and the air outlet end of the heat exchanger is communicated with a pyrolysis gas inlet of the pyrolysis device; the heat exchanger is used for heating the flue gas discharged from the flue gas outlet, so that the pyrolysis gas can be heated to meet the pyrolysis gas temperature requirement for pyrolyzing biomass; high-temperature flue gas in the flue does not need to be extracted, the flue gas discharged from the flue outlet of the boiler flue still has certain waste heat, the waste heat can reduce the heat of the high-temperature flue gas absorbed by the heat exchanger, and the influence on an economizer and an air preheater due to the fact that the heat exchanger absorbs too much heat of the high-temperature flue gas is reduced.

Description

Technical Field

[0001] This invention relates to the field of biomass pyrolysis technology, and in particular to a biomass pyrolysis system and a coal-fired power plant. Background Technology

[0002] Biomass pyrolysis is a biomass pretreatment and fuel upgrading technology performed under normal pressure and anaerobic conditions. The pyrolysis process decomposes biomass into combustible gases and liquids, forming carbonized solid fuel. Compared to direct combustion of raw biomass, biomass pyrolysis technology can improve fuel stability and calorific value, reduce its moisture content, thereby reducing energy loss and flue gas emissions during combustion and improving boiler thermal efficiency.

[0003] In existing technologies, biomass pyrolysis utilizes high-temperature flue gas from a boiler as a heat source to pyrolyze the biomass. However, the boiler flue contains an economizer and an air preheater. The economizer uses the heat from the flue gas to heat the feedwater entering the boiler, while the air preheater uses the heat from the flue gas to preheat the air participating in combustion. When a large amount of high-temperature flue gas is extracted for the biomass pyrolysis system, the heat supply to the economizer and air preheater in the boiler flue becomes insufficient. The feedwater temperature entering the boiler fails to reach the ideal level, and the temperature of the air participating in combustion is also difficult to effectively increase. This deteriorates the combustion conditions within the boiler, reduces combustion efficiency, increases overall boiler heat loss, and significantly impacts the boiler's thermal efficiency. Summary of the Invention

[0004] The technical problem to be solved by this invention is that existing biomass pyrolysis systems use high-temperature flue gas from boilers as a heat source, which has a significant impact on the boiler's thermal efficiency.

[0005] In order to solve the above-mentioned technical problems, the purpose of this invention is to provide a biomass pyrolysis system, including: a pyrolysis device, a heat exchanger and an induced draft fan; The air inlet of the induced draft fan is used to connect to the flue outlet of the boiler. The heat exchanger is installed inside the flue, and the flue gas temperature at the location of the heat exchanger is greater than or equal to 300°C and less than or equal to 400°C. The air outlet of the induced draft fan is connected to the air inlet of the heat exchanger; The air outlet of the heat exchanger is connected to the pyrolysis gas inlet of the pyrolysis device.

[0006] As a preferred embodiment, the biomass pyrolysis system further includes a first control valve, a second control valve, a gas heating device, and a control system; The first end of the first control valve is connected to the air outlet of the heat exchanger, the first end of the second control valve is connected to the air outlet of the induced draft fan, the second ends of the first control valve and the second end of the second control valve are both connected to the air inlet of the gas heating device, and the air outlet of the gas heating device is connected to the pyrolysis gas inlet of the pyrolysis device. The first control valve, the second control valve, and the gas heating device are all electrically connected to the control system. When the load of the boiler is greater than a set threshold, the control system controls the opening of the first control valve to increase, the opening of the second control valve to decrease, and the power of the gas heating device to decrease. When the load of the boiler is less than or equal to the set threshold, the control system controls the opening of the first control valve to decrease, the opening of the second control valve to increase, and the power of the heating device to increase.

[0007] As a preferred embodiment, the biomass pyrolysis system further includes a temperature sensor for detecting the temperature of the pyrolysis gas entering the pyrolysis device, and the temperature sensor is electrically connected to the control system.

[0008] As a preferred embodiment, when the temperature sensor detects a value below 200°C, the control system controls the opening of the first control valve to increase and / or the power of the heating device to increase; when the temperature sensor detects a value above 200°C, the control system controls the opening of the first control valve to decrease and / or the power of the heating device to decrease.

[0009] As a preferred embodiment, the biomass pyrolysis system further includes a dust collector, the inlet of which is connected to the flue outlet, and the outlet of which is connected to the inlet of the induced draft fan.

[0010] As a preferred embodiment, the boiler further includes an economizer and an air preheater arranged in the flue, with the heat exchanger arranged between the economizer and the air preheater.

[0011] As a preferred embodiment, the biomass pyrolysis system further includes a gas-liquid separator, the gas inlet of which is connected to the pyrolysis gas outlet of the pyrolysis device.

[0012] As a preferred embodiment, the outlet of the gas-liquid separator is connected to the air inlet of the boiler.

[0013] As a preferred embodiment, the biomass pyrolysis system further includes a booster fan, the air inlet of which is connected to the air outlet of the induced draft fan, and the air outlet of which is connected to the air inlet of the heat exchanger.

[0014] A coal-fired power plant, comprising the aforementioned biomass pyrolysis system.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: The biomass pyrolysis system of the present invention includes a pyrolysis device, a heat exchanger, and an induced draft fan; the air inlet of the induced draft fan is used to connect to the flue gas outlet of the boiler flue; the heat exchanger is disposed in the flue gas, and the flue gas temperature at the location of the heat exchanger is greater than or equal to 300°C and less than or equal to 400°C; the air outlet of the induced draft fan is connected to the air inlet of the heat exchanger, and the air outlet of the heat exchanger is connected to the pyrolysis gas inlet of the pyrolysis device; the heat exchanger heats the flue gas discharged from the flue gas outlet, thereby heating the pyrolysis gas. The biomass pyrolysis system of this application does not require the extraction of high-temperature flue gas from the flue. Moreover, although most of the heat in the flue gas discharged from the boiler flue outlet has been absorbed by heat exchange devices such as economizers and air preheaters in the flue, there is still some residual heat in the flue gas discharged from the outlet. The presence of this residual heat can reduce the heat absorbed by the heat exchangers from the high-temperature flue gas, thereby reducing the impact of excessive heat absorption by the heat exchangers on the economizers and air preheaters. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the biomass pyrolysis system of the present invention; In the diagram, 100 is the flue, 1 is the pyrolysis device, 2 is the heat exchanger, 31 is the induced draft fan, 32 is the booster fan, 41 is the first control valve, 42 is the second control valve, 43 is the temperature sensor, 5 is the gas heating device, 6 is the dust collector, 71 is the gas-liquid separator, 72 is the storage tank, 73 is the feeder, 74 is the unloader, and 75 is the carbonization tank. Detailed Implementation

[0017] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0018] In the description of this invention, it should be understood that the terms "upper," "lower," "left," "right," "top," and "bottom," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. It should be understood that the terms "first," "second," etc., are used in this invention to describe various information, but this information should not be limited to these terms. These terms are only used to distinguish information of the same type from each other. For example, without departing from the scope of this invention, "first" information can also be referred to as "second" information, and similarly, "second" information can also be referred to as "first" information.

[0019] like Figure 1 As shown, a preferred embodiment of the biomass pyrolysis system of the present invention includes: a pyrolysis device 1, a heat exchanger 2, and an induced draft fan 31; the air inlet of the induced draft fan 31 is used to connect to the flue gas outlet of the boiler flue 100; the heat exchanger 2 is disposed in the flue 100, and the flue gas temperature at the location of the heat exchanger 2 is greater than or equal to 300°C and less than or equal to 400°C; the air outlet of the induced draft fan 31 is connected to the air inlet of the heat exchanger 2; the air outlet of the heat exchanger 2 is connected to the pyrolysis gas inlet of the pyrolysis device 1. In this embodiment of the biomass pyrolysis system, the induced draft fan 31 draws flue gas from the flue gas outlet of the boiler flue 100. The flue gas here has already undergone heat exchange by heat exchange devices such as economizers and air preheaters, rather than directly drawing high-temperature flue gas from the flue 100. Although the temperature of the flue gas has been reduced by the previous heat exchange, it still retains a certain amount of residual heat. The temperature of the flue gas here is between 80°C and 150°C. Heat exchanger 2 uses the flue gas inside flue 100 to heat the low-temperature flue gas from the flue outlet, bringing it to the temperature required for biomass pyrolysis. Through this indirect heating method, instead of directly extracting the high-temperature flue gas from the economizer and air preheater areas, it utilizes the flue gas downstream that has already released most of its heat and supplements it with appropriate heat through heat exchanger 2. This reduces interference with the heat supply to the economizer and air preheater, and enables the coordinated operation of the boiler system and the biomass pyrolysis system.

[0020] In some embodiments of the present invention, the biomass pyrolysis system further includes a first control valve 41, a second control valve 42, a gas heating device 5, and a control system; the first end of the first control valve 41 is connected to the air outlet of the heat exchanger 2, the first end of the second control valve 42 is connected to the air outlet of the induced draft fan 31, the second ends of both the first control valve 41 and the second end of the second control valve 42 are connected to the air inlet of the gas heating device 5, and the air outlet of the gas heating device 5 is connected to the pyrolysis gas inlet of the pyrolysis device 1; the first control valve 41 can regulate the amount of flue gas entering the heating device through the heat exchanger 2, the second control valve 42 can control the amount of flue gas entering the heating device without passing through the heat exchanger 2, and the gas heating device 5 can receive the flue gas from the first control valve 41 and the second control valve 42, and through additional Heating increases the gas temperature to ensure that the gas entering the pyrolysis unit 1 meets the pyrolysis requirements. The first control valve 41, the second control valve 42, and the gas heating device 5 are all electrically connected to the control system. When the boiler load exceeds the set threshold, the boiler is in a high-load state. At this time, the flue gas in the flue 100 has sufficient heat and does not need to rely too much on auxiliary heating. The control system controls the opening of the first control valve 41 to increase, the opening of the second control valve 42 to decrease, and the power of the gas heating device 5 to decrease. The heat of the boiler flue 100 is used first to heat the flue gas, and the heating device consumes less energy. When the boiler load is less than or equal to the set threshold, the control system controls the opening of the first control valve 41 to decrease, the opening of the second control valve 42 to increase, and the power of the heating device to increase. When the boiler load is low, the heat supply in the high-temperature zone of the boiler flue 100 is limited. At this time, the opening of the first control valve 41 is reduced to avoid excessive extraction of effective heat from the boiler under low load. The opening of the second control valve 42 is increased to utilize the active heating of the heating device to heat the flue gas, ensuring that the pyrolysis device 1 obtains stable high-temperature gas and guaranteeing the continuity of biomass pyrolysis. In this embodiment, the aforementioned threshold value is 80% of the boiler's standard power.

[0021] In some embodiments of the present invention, the biomass pyrolysis system further includes a temperature sensor 43, which is used to detect the temperature of the pyrolysis gas entering the pyrolysis device 1. The temperature sensor 43 is electrically connected to the control system. Specifically, the control system compares the measured temperature of the temperature sensor 43 with the target temperature required for biomass pyrolysis to determine whether there is a deviation. If the measured temperature is lower than the target temperature, the control system can further increase the opening of the first control valve 41 and increase the power of the gas heating device 5 to bring the measured temperature closer to the target temperature. If the measured temperature is higher than the target value, the control system can adjust in the opposite direction, such as reducing the opening of the first control valve 41 and decreasing the heating power, to avoid excessively high pyrolysis temperatures leading to excessive biomass pyrolysis or a decline in the quality of pyrolysis products.

[0022] Specifically, when the temperature sensor 43 detects a value below 200°C, the control system increases the opening of the first control valve 41 and / or increases the power of the heating device. Since the initial temperature of most biomass pyrolysis is above 200°C, this threshold setting prevents incomplete pyrolysis due to excessively low temperatures, ensuring the basic conditions for the pyrolysis reaction. Specifically, when the temperature sensor 43 detects a value below 200°C and the boiler is under high load, the control system increases the opening of the first control valve 41. When the temperature sensor 43 detects a value below 200°C and the boiler is under low load, the control system increases the power of the heating device. When the temperature sensor 43 detects a value above 350°C, the control system decreases the opening of the first control valve 41 and / or decreases the power of the heating device. This setting prevents excessive temperature from causing excessive pyrolysis of biomass, while avoiding energy waste and maintaining the stability of pyrolysis products. Specifically, when the temperature sensor 43 detects a value higher than 350°C and the boiler is under high load, the control system controls the opening of the first control valve 41 to be reduced; when the temperature sensor 43 detects a value higher than 350°C and the boiler is under low load, the control system controls the power of the heating device to be reduced.

[0023] In some embodiments of the present invention, the biomass pyrolysis system further includes a dust collector 6. The inlet of the dust collector 6 is connected to the flue gas outlet of the flue 100, and the outlet of the dust collector 6 is connected to the inlet of the induced draft fan 31. The flue gas discharged from the boiler flue 100 usually contains a certain amount of solid impurities such as fly ash and carbon particles. If it directly enters the induced draft fan 31, heat exchanger 2, or gas heating device 5, it may cause ash accumulation, wear, or blockage inside the equipment. The dust collector 6 can effectively intercept these impurities, reduce equipment wear and failure risk, and extend the overall service life of the system. The dust collector 6 can purify the flue gas to be introduced into the pyrolysis device 1, removing dust, particulate matter, and other impurities contained in the flue gas. Moreover, if the dust-laden flue gas directly participates in the pyrolysis process, the dust may mix into the pyrolysis products, affecting the purity of the products. The flue gas purified by the dust collector 6 is cleaner, which can reduce the interference of impurities on the pyrolysis reaction and ensure the quality stability of the pyrolysis products.

[0024] In some embodiments of the present invention, the boiler further includes an economizer and an air preheater arranged in the flue 100, with a heat exchanger 2 arranged between the economizer and the air preheater. The economizer needs to use higher temperature flue gas to heat the feedwater, while the air preheater needs to use lower temperature flue gas to preheat the air. The heat exchanger 2, located between the two, extracts heat from the middle section of the flue gas outside the operating temperature range of both, thus not affecting the heat absorption efficiency of the economizer. Moreover, it meets the heat requirements of biomass pyrolysis and can minimize the impact of the biomass pyrolysis system on the original heat exchange system of the boiler.

[0025] In some embodiments of the present invention, the biomass pyrolysis system further includes a gas-liquid separator 71, the inlet of which is connected to the pyrolysis gas outlet of the pyrolysis device 1. Of the mixed products generated by biomass pyrolysis, the gaseous products can be directly burned as fuel or further purified for utilization, while the liquid products can be used as fuel or chemical raw materials after processing. The gas-liquid separator 71 separates the two products through physical separation, such as gravity sedimentation or centrifugal separation, creating conditions for subsequent classification, collection, storage, and utilization.

[0026] Furthermore, the outlet of the gas-liquid separator 71 is connected to the air inlet of the boiler. The combustible gas produced by biomass pyrolysis itself has a high calorific value. Introducing it into the boiler for combustion can replace part of the coal or other fuels, reducing the input of external energy.

[0027] In some embodiments of the present invention, the biomass pyrolysis system further includes a booster fan 32, the air inlet of which is connected to the air outlet of the induced draft fan 31, and the air outlet of the booster fan 32 is connected to the air inlet of the heat exchanger 2. When the flue gas pressure fluctuates within the boiler flue 100 or the system pipeline resistance is high, the induced draft fan 31 alone may not be able to ensure a stable flow of flue gas into the heat exchanger 2. The booster fan 32, through secondary pressurization, can overcome the pipeline resistance, ensuring that the flue gas enters the heat exchanger 2 at the designed flow rate, thus guaranteeing heat exchange efficiency.

[0028] In some embodiments of the present invention, the pyrolysis system further includes a storage bin 72, a feeder 73, a discharger 74, and a carbonization silo. The storage bin stores biomass raw materials. The discharge port of the storage bin is connected to the inlet of the feeder 73, and the outlet of the feeder 73 is connected to the inlet of the pyrolysis device 1. The feeder 73 quantitatively and stably transports the biomass raw materials in the storage bin 72 to the inlet of the pyrolysis device 1. The feeding rate can be adjusted to match the processing capacity of the pyrolysis device 1. The solid discharge port of the pyrolysis device 1 is connected to the inlet of the discharger 74, and the outlet of the discharger 74 is connected to the inlet of the carbonization silo. The discharger 74 discharges the solid products generated by the pyrolysis device 1 from the pyrolysis device 1 and transports them to the carbonization silo. The pyrolysis device 1 can be a fixed-bed hot blast stove, a fluidized-bed hot blast stove, or a rotary hot blast stove.

[0029] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0030] In summary, the biomass pyrolysis system of the present invention includes a pyrolysis device 1, a heat exchanger 2, and an induced draft fan 31; the air inlet of the induced draft fan 31 is connected to the flue gas outlet of the boiler flue 100; the heat exchanger 2 is disposed within the flue 100, and the flue gas temperature at the location of the heat exchanger 2 is greater than or equal to 300°C and less than or equal to 400°C; the air outlet of the induced draft fan 31 is connected to the air inlet of the heat exchanger 2, and the air outlet of the heat exchanger 2 is connected to the pyrolysis gas inlet of the pyrolysis device 1; the heat exchanger 2 heats the flue gas discharged from the flue gas outlet, thereby increasing the pyrolysis gas temperature. The pyrolysis gas temperature required for biomass pyrolysis is such that the biomass pyrolysis system of this application does not require extraction of high-temperature flue gas from the flue 100. Moreover, although most of the heat of the flue gas discharged from the flue outlet of the boiler flue 100 has been absorbed by the economizer and air preheater and other heat exchange devices in the flue 100, the flue gas discharged from the flue outlet still has a certain amount of residual heat. The presence of this residual heat can reduce the heat of the high-temperature flue gas absorbed by the heat exchanger 2, and reduce the impact of excessive heat absorption of high-temperature flue gas by the heat exchanger 2 on the economizer and air preheater.

[0031] This application also provides a coal-fired power plant, including the above-described biomass pyrolysis system.

[0032] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of the present invention, and these improvements and substitutions should also be considered within the scope of protection of the present invention.

Claims

1. A biomass pyrolysis system, characterized in that, include: The pyrolysis unit (1), heat exchanger (2) and induced draft fan (31); The air inlet of the induced draft fan (31) is used to connect to the flue outlet of the boiler flue (100); The heat exchanger (2) is installed in the flue (100), and the flue gas temperature at the location of the heat exchanger (2) is greater than or equal to 300°C and less than or equal to 400°C. The air outlet of the induced draft fan (31) is connected to the air inlet of the heat exchanger (2); The air outlet of the heat exchanger (2) is connected to the pyrolysis gas inlet of the pyrolysis device (1).

2. The biomass pyrolysis system according to claim 1, characterized in that, The biomass pyrolysis system also includes a first control valve (41), a second control valve (42), a gas heating device (5), and a control system; The first end of the first control valve (41) is connected to the air outlet of the heat exchanger (2), the first end of the second control valve (42) is connected to the air outlet of the induced draft fan (31), the second end of the first control valve (41) and the second end of the second control valve (42) are both connected to the air inlet of the gas heating device (5), and the air outlet of the gas heating device (5) is connected to the pyrolysis gas inlet of the pyrolysis device (1). The first control valve (41), the second control valve (42), and the gas heating device (5) are all electrically connected to the control system. When the load of the boiler is greater than the set threshold, the control system controls the opening of the first control valve (41) to increase, controls the opening of the second control valve (42) to decrease, and controls the power of the gas heating device (5) to decrease. When the load of the boiler is less than or equal to the set threshold, the control system controls the opening of the first control valve (41) to decrease, controls the opening of the second control valve (42) to increase, and controls the power of the heating device to increase.

3. The biomass pyrolysis system according to claim 2, characterized in that, The biomass pyrolysis system also includes a temperature sensor (43), which is used to detect the temperature of the pyrolysis gas entering the pyrolysis device (1), and the temperature sensor (43) is electrically connected to the control system.

4. The biomass pyrolysis system according to claim 3, characterized in that, When the temperature sensor (43) detects a value below 200°C, the control system controls the opening of the first control valve (41) to increase and / or the power of the heating device to increase; when the temperature sensor (43) detects a value above 200°C, the control system controls the opening of the first control valve (41) to decrease and / or the power of the heating device to decrease.

5. The biomass pyrolysis system according to claim 1, characterized in that, The biomass pyrolysis system also includes a dust collector (6), the inlet of which is connected to the outlet of the flue (100), and the outlet of which is connected to the inlet of the induced draft fan (31).

6. The biomass pyrolysis system according to claim 1, characterized in that, The boiler also includes an economizer and an air preheater arranged in the flue (100), and the heat exchanger (2) is arranged between the economizer and the air preheater.

7. The biomass pyrolysis system according to claim 1, characterized in that, The biomass pyrolysis system also includes a gas-liquid separator (71), the inlet of which is connected to the pyrolysis gas outlet of the pyrolysis device (1).

8. The biomass pyrolysis system according to claim 7, characterized in that, The outlet of the gas-liquid separator (71) is connected to the air inlet of the boiler.

9. The biomass pyrolysis system according to claim 1, characterized in that, The biomass pyrolysis system further includes a booster fan (32), the air inlet of which is connected to the air outlet of the induced draft fan (31), and the air outlet of which is connected to the air inlet of the heat exchanger (2).

10. A coal-fired power plant, characterized in that, Includes the biomass pyrolysis system according to any one of claims 1 to 9.

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