Biomass pyrolysis carbonization system coupled with coal-fired boiler

Abstract

The invention discloses a biomass pyrolysis carbonization system coupled with a coal-fired boiler, and belongs to the technical field of coal-fired systems. The feeding end of a belt conveyor of the system is connected with biomass raw material supply equipment, and the discharging end of the belt conveyor is connected with a pyrolysis carbonization furnace; the interior of the coal-fired boiler is connected with a pyrolysis gas outlet of the pyrolysis carbonization furnace through a pipeline, and a flue gas pipeline of the coal-fired boiler is further connected with a double-layer shell structure of the pyrolysis carbonization furnace; the heat exchanger is in pipeline connection with the double-layer shell structure of the pyrolysis carbonization furnace and the feeding end of the belt conveyor respectively; the heat exchanger is arranged in the double-layer machine shell structure and used for exchanging heat between the flue gas in the double-layer machine shell structure and air entering the heat exchanger, conveying the air with the temperature increased after heat exchange to the feeding end of the belt conveyor through a hot air conveying pipeline, and discharging the flue gas with the temperature reduced after heat exchange. And meanwhile, carbon emission reduction of the coal-fired boiler is achieved through effective utilization of the flue gas temperature of the combustion boiler.

Description

Technical Field

[0001] The invention relates to the technical field of coal-fired systems, and in particular to a biomass pyrolysis and carbonization system coupled to a coal-fired boiler. Background Art

[0002] Biomass resources are widely distributed, huge renewable resources, and environmentally friendly low-carbon energy. Biochar, as an alternative to coal, coupled with coal-fired power plants, is one of the important paths for the low-carbon transformation of the power industry. Large-capacity coal-fired boilers often require a large amount of biochar. Taking a 2×600MW coal-fired power unit as an example, if biochar is mixed at a ratio of 10%, 200,000 tons of biochar will be required each year.

[0003] Biomass raw materials have the characteristic of high moisture content. If biomass raw materials with high moisture content directly enter the pyrolysis carbonization furnace, it will consume a lot of energy during the biomass pyrolysis process. The higher the moisture content, the greater the energy consumption. For example, the energy consumed by biomass raw materials with a moisture content of 60% in the pyrolysis carbonization furnace is 1.6 times that of biomass raw materials with a moisture content of 10%. Excessive moisture content in biomass raw materials will reduce the current processing scale of biomass pyrolysis carbonization furnaces, limiting their development in large-capacity coal-fired power units.

[0004] At present, the drying of biomass is mainly achieved by setting up a biomass drying furnace. Although it can reduce the moisture content of the biomass entering the pyrolysis carbonization furnace, the biomass drying furnace is large in size, which will increase system investment, increase system process complexity, increase floor space and increase energy consumption. In addition, the dried gas (air or flue gas) contains VOCs and has an odor, so a VOCs gas purification device needs to be installed. Summary of the invention

[0005] The purpose of the present invention is to overcome the problems in the prior art and to provide a biomass pyrolysis carbonization system coupled to a coal-fired boiler, which can achieve feeding and drying at the same time, without the need to dry the biomass raw materials through a biomass drying furnace or add a VOCs gas purification device.

[0006] The present invention provides a biomass pyrolysis and carbonization system coupled with a coal-fired boiler, comprising: The pyrolysis carbonization furnace has a double-layer casing structure; The belt conveyor has a feed end and a discharge end, wherein the feed end is connected to the biomass raw material feeding device, and the discharge end is connected to the pyrolysis carbonization furnace; an air inlet is provided at the bottom of the belt conveyor near the feed end, and an exhaust port is provided on the housing of the belt conveyor at the discharge end; A coal-fired boiler, the interior of which is connected to the pyrolysis gas outlet of the pyrolysis carbonization furnace and the exhaust port of the belt conveyor through a pipeline, the coal-fired boiler is connected to a flue gas duct, the flue gas duct is also connected to the double-layer casing structure of the pyrolysis carbonization furnace, and the flue gas duct is used to transport the flue gas generated by the combustion of the coal-fired boiler to the double-layer casing structure of the pyrolysis carbonization furnace; The heat exchanger has a first heat exchange channel and a second heat exchange channel. The first heat exchange channel is connected to the double-layer casing structure pipeline of the pyrolysis carbonization furnace. One end of the second heat exchange channel is connected to the air supply equipment, and the other end is connected to the air inlet of the belt conveyor through the hot air delivery pipeline; the heat exchanger is used to transfer the smoke in the double-layer casing structure.

[0007] Preferably, the air inlet is connected to a curved pipe arranged along the conveying direction of the belt conveyor, so that the hot air entering the belt conveyor has the same conveying direction as the material in the belt conveyor.

[0008] Preferably, both the feeding end and the discharging end of the belt conveyor are provided with flexible baffles, and the flexible baffles are connected to the casing of the belt conveyor to form a closed space inside the belt conveyor.

[0009] Preferably, the belt conveyor has a conveyor belt, and the conveyor belt has ventilation holes penetrating the conveyor belt.

[0010] Preferably, the exhaust port of the belt conveyor is also connected to a cyclone dust collector through a pipeline, and the gas outlet of the cyclone dust collector is connected to the primary fan of the coal-fired boiler. The gas discharged from the exhaust port of the belt conveyor enters the primary fan of the coal-fired boiler after passing through the cyclone dust collector, and finally enters the coal-fired boiler for combustion.

[0011] Preferably, the conveyor belt of the belt conveyor is a metal mesh, a chain plate or a grate plate.

[0012] Preferably, a plurality of partitions are provided on the conveyor belt of the belt conveyor along the length direction of the conveyor belt.

[0013] Preferably, the angle between the conveyor belt of the belt conveyor and the horizontal ground is less than 45°.

[0014] Preferably, the discharge port of the pyrolysis carbonization furnace is connected to a spiral discharge machine, and the discharge end of the spiral discharge machine is connected to the feed port of the cooling furnace, so as to transport the pyrolytic char generated by pyrolysis in the pyrolysis carbonization furnace to the cooling furnace.

[0015] Compared with the prior art, the present invention has the following beneficial effects: Hot air is introduced into the feeding end of the belt conveyor in the biomass pyrolysis and carbonization system coupled to the coal-fired boiler of the present invention to achieve the purpose of drying while feeding. The belt conveyor of the present invention can both transport biomass and dry biomass without passing through a biomass drying furnace. The function of reducing the moisture content of the biomass raw materials can be achieved during the transportation of the biomass raw materials. The invention has the advantages of reducing system investment, simple process, and reduced system footprint.

[0016] The pyrolysis gas generated by the pyrolysis carbonization furnace of the present invention enters the boiler for combustion, and the generated high-temperature flue gas is transported to the pyrolysis carbonization furnace through the flue gas pipeline as a pyrolysis heat source for the pyrolysis carbonization furnace; at the same time, the hot air supplied by the belt conveyor of the present invention is obtained by introducing the cooled flue gas and air in the double-layer casing structure of the pyrolysis carbonization furnace into a heat exchanger for heat exchange, thereby reducing the energy consumption of drying biomass raw materials by utilizing the waste heat of the high-temperature flue gas.

[0017] The present invention utilizes high-temperature air heated by flue gas waste heat as a drying heat source for biomass raw materials in a belt conveyor; the dried exhausted air (temperature is about 80-100°C) is sent to the inlet of the primary fan of the coal-fired boiler, and enters the coal-fired boiler along with the primary fan, which not only utilizes the flue gas waste heat, but also does not require additional VOCs gas purification equipment, and also increases the primary air temperature to achieve a coal-saving effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The figure is a schematic diagram of the overall structure of a biomass pyrolysis and carbonization system coupled to a coal-fired boiler according to an embodiment of the present invention.

[0019] Figure 2 It is a schematic structural diagram of a belt conveyor according to an embodiment of the present invention.

[0020] Description of reference numerals: 1. Pyrolysis carbonization furnace, 2. Belt conveyor, 201. Frame, 202. Casing, 203, Air inlet; 204. Exhaust port, 3. Coal-fired boiler, 4. Flue gas duct, 5. Heat exchanger, 6. Flexible baffle, 7. Conveyor belt, 8. Cyclone dust collector, 9. Primary fan, 10. Screw discharger, 11. Cooling furnace. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solution and advantages of the embodiments of the present disclosure clearer, the technical solution of the embodiments of the present disclosure will be clearly and completely described below in conjunction with the drawings of the embodiments of the present disclosure. Obviously, the described embodiments are part of the embodiments of the present disclosure, not all of the embodiments. Based on the described embodiments of the present disclosure, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present disclosure.

[0022] Unless otherwise defined, the technical terms or scientific terms used herein should be understood by people with ordinary skills in the field to which the present disclosure belongs. "First", "second" and similar words used in the present disclosure do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before "include" or "comprise" cover the elements or objects listed after "include" or "comprise" and their equivalents, and do not exclude other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0023] The present embodiment provides a biomass pyrolysis carbonization system coupled with a coal-fired boiler, comprising a pyrolysis carbonization furnace 1, a belt conveyor 2, a coal-fired boiler 3 and a heat exchanger 5. The pyrolysis carbonization furnace 1 in the present embodiment is a pyrolysis carbonization furnace 1 with a double-layer casing structure; the belt conveyor 2 is used to convey biomass raw materials to the pyrolysis carbonization furnace 1, and the belt conveyor 2 has a feed end and a discharge end, the feed end is connected to a biomass raw material feeding device, and the discharge end is connected to the pyrolysis carbonization furnace 1; in general, the water content of the biomass raw materials is The rate range is 30%~60%. The biomass raw material enters the belt conveyor 2 from the feeding port at the feeding end of the belt conveyor 2, and the biomass raw material is transported, lifted and dried in the belt conveyor 2. The moisture content of the dried biomass raw material is reduced to less than 15%, and then enters the pyrolysis carbonization furnace 1. In order to facilitate the transportation of the dried biomass raw material to the pyrolysis carbonization furnace 1, the discharge port at the discharge end of the belt conveyor 2 is also connected to a screw feeder, and the dried material is transported to the pyrolysis carbonization furnace 1 through the screw feeder.

[0024] In this embodiment, the interior of the coal-fired boiler 3 is connected to the pyrolysis gas outlet of the pyrolysis carbonization furnace 1 through a pipeline. The coal-fired boiler 3 is connected to a flue gas duct 4 for discharging the combustion flue gas inside the coal-fired boiler 3. The flue gas duct 4 is also connected to the double-layer casing structure of the pyrolysis carbonization furnace 1. The flue gas duct 4 is used to transport the flue gas generated by the combustion of the coal-fired boiler 3 to the double-layer casing structure of the pyrolysis carbonization furnace 1, and the flue gas is used as a pyrolysis heat source for the pyrolysis carbonization furnace 1; in this embodiment, the pyrolysis gas of the pyrolysis carbonization furnace 1 directly enters the combustion boiler for combustion, and the high-temperature flue gas inside the coal-fired boiler 3 is used as a pyrolysis heat source for the pyrolysis carbonization furnace 1, and is transported to the inside of the double-layer casing structure through the flue gas duct 4. In this embodiment, the dried biomass enters the screw feeder from the discharge port of the belt conveyor 2, and then is sent to the pyrolysis carbonization furnace 1 through the screw feeder; the biomass is indirectly contacted with the high-temperature flue gas in the pyrolysis carbonization furnace 1 for heat exchange, and the biomass undergoes pyrolysis reaction when heated to generate pyrolysis gas and pyrolysis charcoal; the pyrolysis gas is sent to the boiler furnace for combustion through the pyrolysis gas blower; the pyrolysis charcoal flows out of the pyrolysis furnace through the screw discharger 10, and then is sent to the cooling furnace through the screw conveyor. As an optional method, the pyrolysis carbonization furnace 1 of this embodiment adopts a rotary, single-cylinder or multi-cylinder structure; the heat source of the pyrolysis carbonization furnace 1 is taken from the high-temperature flue gas before the boiler economizer, and the temperature of the high-temperature flue gas is generally 600℃~700℃; the high-temperature flue gas indirectly exchanges heat with the biomass in the pyrolysis carbonization furnace 1, and the flue gas temperature drops to 300℃~450℃ and is discharged from the pyrolysis carbonization furnace 1.

[0025] In this embodiment, in order to reduce the moisture content of the biomass raw materials in the belt conveyor 2, hot air for drying the materials is transported inside the belt conveyor 2. In this embodiment, the heat exchanger 5 is connected to the double-layer casing structure of the pyrolysis carbonization furnace 1 and the feed end of the belt conveyor 2 by pipelines; it is used to exchange heat between the flue gas in the double-layer casing structure and the air entering the heat exchanger 5, and the air with a higher temperature after heat exchange is transported to the feed end of the belt conveyor 2 through the hot air transport pipeline, and the flue gas with a lower temperature after heat exchange is discharged. Therefore, the hot air in this embodiment is obtained by exchanging heat and heating the normal temperature air with the flue gas in the double-layer casing structure of the pyrolysis carbonization furnace 1 in the heat exchanger 5, which reduces the energy consumption for air heating. In this embodiment, the flue gas discharged from the pyrolysis carbonization furnace 1 enters the heat exchanger 5, exchanges heat with the air at the outlet of the blower, and heats the air to a high temperature of 100°C to 200°C; then enters the air inlet arranged on the belt conveyor 2, and the flue gas flow direction is the same as that of the biomass raw material; after the biomass raw material is dried, the temperature of the exhausted air is reduced to 80°C to 120°C; the temperature of the flue gas at the outlet of the heat exchanger 5 is reduced to 100°C to 200°C, and under the action of the flue gas fan, enters the air preheater outlet flue of the fuel boiler.

[0026] The belt conveyor 2 in this embodiment is provided with an air inlet 203 at the bottom near the feed end, and the hot air conveying pipeline is connected to the air inlet 203. The air inlet 203 has a curved pipe arranged along the conveying direction of the belt conveyor 2, so that the hot air entering the belt conveyor 2 has the same conveying direction as the material in the belt conveyor 2. An exhaust port 204 is provided on the casing 202 at the discharge end of the belt conveyor 2. Therefore, during the material conveying process, the hot air moves in the same direction as the material, which can increase the contact time between the hot air and the material. In this embodiment, the hot air is input from the feed end, and the material humidity at the feed end is higher. Therefore, the material with higher humidity can be heated at a higher temperature, thereby realizing the effective utilization of energy. The exhausted hot air in the belt conveyor 2 is discharged through the exhaust port 204.

[0027] As another optional method, the feed end and the discharge end of the belt conveyor 2 described in this embodiment are both provided with a flexible baffle 6, and the flexible baffle 6 is connected to the casing of the belt conveyor 2 to form a closed space inside the belt conveyor 2. The casing of the discharge end of the belt conveyor 2 is provided with an exhaust port. In order to prevent the hot air in the belt conveyor 2 from dissipating and reducing the drying efficiency, the inlet and outlet of the feed end and the discharge end are both sealed by a flexible material in this embodiment. More specifically, the feed port of the belt conveyor 2 is designed to be separate from the casing of the belt conveyor 2; the casing is provided with a flexible baffle 6 to play a sealing role; the flexible baffle 6 is made of rubber or metal material, and the flexible baffle 6 can be directly connected to the casing or connected in the form of a hinge.

[0028] like Figure 2 As shown, the belt conveyor 2 of this embodiment is composed of a frame 201, a housing 202, a ventilated conveyor belt 7, a motor and a reduction device. The belt conveyor 2 is provided with four interfaces, namely, a feed port, a discharge port, an air inlet 203 and an exhaust port 204. The air inlet 203 is provided at the bottom of the housing 201, and the exhaust port 204 is provided at the top of the housing 201. High-temperature air (100-200°C) enters the belt conveyor 2 from the air inlet 203, in the same direction as the flow of the biomass raw material, and contacts and exchanges heat with the biomass raw material to dry it. The exhausted hot air after cooling flows out from the exhaust port 204, first passes through the cyclone dust collector 8 to remove particulate matter, and then is transported to the inlet of the primary fan 9 of the coal-fired boiler under the action of the induced draft fan. This design not only improves the drying efficiency of the biomass raw material, but also realizes the recycling of energy, because the exhausted hot air can be used as the combustion air of the boiler, thereby reducing the energy consumption of the entire system.

[0029] Preferably, the belt conveyor 2 has a conveyor belt 7, and the conveyor belt 7 has ventilation holes. The belt conveyor 2 adopts a ventilated conveyor belt 7, and the ventilated conveyor belt 7 can adopt a metal wire mesh, a grate plate, a chain plate or other structural types. The design of the ventilated conveyor belt 7 can allow high-temperature dry air to pass through, and can also transport and lift materials.

[0030] Preferably, the exhaust port of the belt conveyor 2 is also connected to a cyclone dust collector 8 through a pipeline, and the gas discharged from the exhaust port of the belt conveyor 2 enters the inlet of the primary fan 9 of the coal-fired boiler 3 after passing through the cyclone dust collector 8.

[0031] Preferably, the conveyor belt 7 of the belt conveyor 2 is provided with a partition, the function of the partition is to remove the material that may be accumulated on the conveyor belt 7, to prevent the material from overflowing or forming irregular accumulation on the conveyor belt 7, and to ensure the continuity and uniformity of material transportation.

[0032] Preferably, the angle between the conveyor belt 7 of the belt conveyor 2 and the horizontal ground is less than 45°, which helps to reduce the rolling and sliding of materials during transportation, and also helps to improve the efficiency of material transportation. In addition, the smaller inclination design also helps to reduce the energy consumption of the conveyor because it reduces the energy required to lift the material.

[0033] Preferably, the discharge port of the pyrolysis carbonization furnace 1 is connected to a spiral discharger 10, and the discharge end of the spiral discharger 10 is connected to the feed port of the cooling furnace, which is used to transport the pyrolytic charcoal to the cooling furnace. This design ensures that the pyrolytic charcoal can be continuously and stably transported from the pyrolysis carbonization furnace 1 to the cooling furnace, avoiding the loss of pyrolytic charcoal and environmental pollution. The cooling furnace of this embodiment adopts a rotary, single-cylinder structure, a tube-in-tube heat exchange cooling method, and is provided with a cooling water inlet and a cooling water outlet; the cooling water adopts the circulating water of the power plant; the cooling furnace reduces the temperature of the pyrolytic charcoal to below 40°C, and then sends it to the coal yard, into the raw coal hopper, or into the boiler primary air pulverized coal pipeline after grinding, etc., to be sent to the boiler for combustion.

[0034] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A biomass pyrolysis carbonization system coupled with a coal-fired boiler, characterized in that: include: The pyrolysis carbonization furnace has a double-layer casing structure; The belt conveyor has a feed end and a discharge end, wherein the feed end is connected to the biomass raw material feeding device, and the discharge end is connected to the pyrolysis carbonization furnace; an air inlet is provided at the bottom of the belt conveyor near the feed end, and an exhaust port is provided on the housing of the belt conveyor at the discharge end; A coal-fired boiler, the interior of which is connected to the pyrolysis gas outlet of the pyrolysis carbonization furnace and the exhaust port of the belt conveyor through a pipeline, the coal-fired boiler is connected to a flue gas duct, the flue gas duct is also connected to the double-layer casing structure of the pyrolysis carbonization furnace, and the flue gas duct is used to transport the flue gas generated by the combustion of the coal-fired boiler to the double-layer casing structure of the pyrolysis carbonization furnace; The heat exchanger has a first heat exchange channel and a second heat exchange channel. The first heat exchange channel is connected to the double-layer casing structure pipeline of the pyrolysis carbonization furnace. One end of the second heat exchange channel is connected to the air supply equipment, and the other end is connected to the air inlet of the belt conveyor through the hot air delivery pipeline. The heat exchanger is used to exchange heat between the flue gas in the double-layer casing structure and the air supplied by the air supply equipment, and the flue gas in the first heat exchange channel is discharged after heat exchange and cooling.

2. The biomass pyrolysis and carbonization system coupled with a coal-fired boiler according to claim 1, characterized in that: The air inlet is connected to a curved pipe arranged along the conveying direction of the belt conveyor, so that the hot air entering the belt conveyor has the same conveying direction as the material in the belt conveyor.

3. The biomass pyrolysis and carbonization system coupled with a coal-fired boiler according to claim 1, characterized in that: The feeding end and the discharging end of the belt conveyor are both provided with flexible baffles, and the flexible baffles are respectively connected to the casings of the feeding end and the discharging end of the belt conveyor.

4. The biomass pyrolysis and carbonization system coupled with a coal-fired boiler according to claim 1, characterized in that: The belt conveyor has a conveyor belt, and the conveyor belt is provided with a ventilation channel penetrating the conveyor belt.

5. The biomass pyrolysis and carbonization system coupled with a coal-fired boiler according to claim 3, characterized in that: The exhaust port of the belt conveyor is also connected to a cyclone dust collector through a pipeline, and the gas outlet of the cyclone dust collector is connected to a primary fan of a coal-fired boiler.

6. The biomass pyrolysis and carbonization system coupled with a coal-fired boiler according to claim 4, characterized in that: The conveyor belt of the belt conveyor is a metal wire mesh, a chain plate or a grate plate.

7. The biomass pyrolysis and carbonization system coupled with a coal-fired boiler according to claim 4, characterized in that: A plurality of partitions are arranged on the conveyor belt of the belt conveyor along the length direction of the conveyor belt.

8. The biomass pyrolysis and carbonization system coupled with a coal-fired boiler according to claim 1, characterized in that: The angle between the conveyor belt of the belt conveyor and the ground is less than 45°.

9. The biomass pyrolysis and carbonization system coupled with a coal-fired boiler according to claim 1, characterized in that: The discharge port of the pyrolysis carbonization furnace is connected to a spiral discharge machine, and the discharge end of the spiral discharge machine is connected to the feed port of the cooling furnace, so as to transport the pyrolysis carbon generated by pyrolysis in the pyrolysis carbonization furnace to the cooling furnace.

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