Biomass semi-gasification combustion device and method

Abstract

A biomass semi-gasification combustion device and method. The biomass semi-gasification combustion device comprises a feeding system, a reciprocating grate (5), an air supply system, a combustion chamber, and a smoke exhaust fan. The combustion chamber comprises a primary combustion chamber (7) and a secondary combustion chamber (8). The air supply system comprises a primary air supply system, a secondary air supply system, and a tertiary air supply system. The biomass semi-gasification combustion method comprises the steps of: feeding, primary air supply and primary combustion, secondary air supply and secondary combustion, tertiary air supply, and slag removal.

Description

Biomass semi-gasification combustion device and method

[0001] This application claims priority to the Chinese patent application filed on January 17, 2024, with application number 202410069763.5 and invention name “A biomass semi-gasification combustion device and method”, the content of which should be understood as incorporated into this application by reference. Technical Field

[0002] The embodiments of the present application relate to, but are not limited to, the drying field, and in particular to a semi-gasification combustion device and method using biomass as fuel, wherein the semi-gasification combustion device is integrated with a flue gas purification and denitrification device. Background Art

[0003] Biomass energy is the fourth largest energy source, after the three major fossil fuels of coal, oil, and natural gas. Biomass energy is a key alternative to fossil fuels due to its large quantity, widespread distribution, strong renewability, low pollution, and zero net carbon dioxide emissions.

[0004] In 2022, coal accounted for 56.2% of total primary energy consumption, down 12.3 percentage points from 2012; oil accounted for about 17.9%, slightly higher by 0.9 percentage points from 2012; natural gas accounted for about 8.4%, up 3.6 percentage points from 2012; and non-fossil energy accounted for 17.5%, up 7.8 percentage points from 2012.

[0005] At present, the main directions in the field of high-end utilization of biomass are pyrolysis and gasification to synthesize liquid fuels (methanol, diesel), pyrolysis and gasification to synthesize hydrogen, or to obtain gaseous fuels by dry distillation. While obtaining fuel gas by the above methods, there are many by-products and a low thermal energy conversion rate (about 70%). In addition, some processes will produce secondary pollutants such as wastewater during the gas purification process. In addition, there are a series of problems such as high investment costs, complex systems, and high difficulty in operation, which form certain barriers to the general combustion and drying field. However, the thermal efficiency of direct combustion of biomass is low. For example, a general wood stove has only 10-20%, and the high escape rate of carbon monoxide combustible gas causes environmental damage.

[0006] Summary of the Invention

[0007] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0008] The first aspect of the present application provides a biomass semi-gasification combustion device, which includes: a feeding system, a reciprocating grate, an air supply system, a combustion chamber and a smoke exhaust fan; wherein:

[0009] A flue gas outlet pipe is provided on the top of the combustion chamber, and the reciprocating grate portion is located in the combustion chamber; the combustion chamber includes a primary combustion chamber and a secondary combustion chamber, the space immediately above the reciprocating grate is the primary combustion chamber, and the space between the primary combustion chamber and the flue gas outlet pipe is the secondary combustion chamber;

[0010] The feeding system is in communication with the primary combustion chamber;

[0011] The air supply system is communicated with the primary combustion chamber and the secondary combustion chamber respectively;

[0012] The air supply system includes a primary air supply system, a secondary air supply system and a tertiary air supply system: the primary air supply system includes a primary fan and a primary air supply duct, the primary fan passes through the primary air supply duct and the air supply port located below the reciprocating grate to supply air to the primary combustion chamber; the secondary air supply system includes a secondary fan and a secondary air supply duct, the secondary fan passes through the secondary air supply duct and the secondary air nozzle at the bottom of the secondary combustion chamber to supply air to the secondary combustion chamber; the tertiary air supply system includes the smoke exhaust fan and a tertiary air supply duct, the smoke exhaust fan passes through the tertiary air supply duct and the tertiary air nozzle in the middle and lower part of the secondary combustion chamber to supply air to the secondary combustion chamber, and delivers the low-temperature flue gas from the external exhaust chimney to the secondary combustion chamber.

[0013] The second aspect of the present application provides a biomass semi-gasification combustion method using the above-mentioned device, comprising the following steps:

[0014] S100: charging, feeding the biomass fuel from the charging system to the surface of the reciprocating grate at the bottom of the primary combustion chamber and burning;

[0015] S200: Primary air supply and primary combustion: The primary air is supplied to the primary combustion chamber by the primary air supply system, and the biomass fuel is partially burned in an organized manner under given conditions of the primary air, generating chemical heat so that the other part of the biomass fuel releases combustible gas through thermal radiation;

[0016] S300: Secondary air supply and secondary combustion. The secondary air is supplied to the secondary combustion chamber by the secondary air supply system. At the same time, the combustible gas generated in step S200 and the mixed flue gas generated by the primary combustion rise and mix with the secondary air to cause secondary combustion and release all heat.

[0017] S400: tertiary air supply, the tertiary low-temperature flue gas from the external exhaust chimney is sent to the secondary combustion chamber through the exhaust fan;

[0018] S500: The burned biomass ash is continuously pushed by the reciprocating grate in the form of slag and falls into the ash collecting hopper, and is discharged by the slag discharger.

[0019] Still other aspects will become apparent upon reading and understanding the accompanying drawings and detailed description.

[0020] Summary of the Figures

[0021] The accompanying drawings are used to provide an understanding of the technical solution of the present application and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the technical solution of the present application and do not constitute a limitation on the technical solution of the present application.

[0022] FIG1 is a schematic structural diagram of a biomass semi-gasification combustion device according to an embodiment of the present application;

[0023] FIG2 is a schematic diagram of the planar distribution of secondary air nozzles in the biomass semi-gasification combustion device in an embodiment of the present application.

[0024] Among them, the figure marks are: 1-double screw feeding system, 2-belt conveyor, 3-intermediate buffer bin, 4-hydraulic feeder, 5-reciprocating grate, 6-reciprocating grate four-stage drive mechanism, 7-primary combustion chamber, 8-secondary combustion chamber, 9-secondary air nozzle, 10-SNCR denitrification system reducing agent spray gun, 11-tertiary air nozzle, 12-primary fan, 13-secondary fan, 14-ash hopper, 15-water seal slag discharger, 16-first electric butterfly valve, 17-flue gas outlet pipe, 18-tertiary air supply pipe, 19-second electric butterfly valve.

[0025] Details

[0026] The present application provides a high-power semi-gasification combustion device and method for biomass fuel. The biomass fuel is burned in the combustion chamber. Through reasonable air distribution, the volatile components are fully burned, and a heat energy conversion rate of more than 95% can be achieved. The ash is discharged in the form of slag. The device of the present application does not produce any other secondary pollutants during the combustion process and is suitable for the field of large-scale hot air furnace drying.

[0027] The first aspect of the present application provides a biomass semi-gasification combustion device, comprising: a feeding system, a reciprocating grate, an air supply system, a combustion chamber and a smoke exhaust fan; wherein:

[0028] A flue gas outlet pipe is provided on the top of the combustion chamber, and the reciprocating grate portion is located in the combustion chamber; the combustion chamber includes a primary combustion chamber and a secondary combustion chamber, the space immediately above the reciprocating grate is the primary combustion chamber, and the space between the primary combustion chamber and the flue gas outlet pipe is the secondary combustion chamber;

[0029] The feeding system is in communication with the primary combustion chamber;

[0030] The smoke exhaust fan is in communication with the secondary combustion chamber;

[0031] The air supply system is communicated with the primary combustion chamber and the secondary combustion chamber respectively.

[0032] In an exemplary embodiment, the feeding system includes a double-screw conveyor, a high-angle belt conveyor, an intermediate buffer bin and a hydraulic feeder connected in sequence, wherein the discharge port of the hydraulic feeder is connected to the feed port of the primary combustion chamber.

[0033] In an exemplary embodiment, the reciprocating grate is provided with an inclined grate surface. Preferably, the inclination angle of the grate surface is 15°.

[0034] In an exemplary embodiment, the reciprocating grate is arranged into four zones along the inclined length direction of the grate surface, wherein zones one and four each occupy 15-20% of the area of ​​the reciprocating grate, and zones two and three each occupy 35-40% of the area of ​​the reciprocating grate; zone one of the reciprocating grate is adjacent to the feed port of the primary combustion chamber.

[0035] In an exemplary embodiment, each area of ​​the reciprocating grate is independent of each other, and the grate in each area can be driven separately, the operating speed can be adjusted separately, and the combustion state can be adjusted according to different fuel types and moisture content.

[0036] In an exemplary embodiment, the primary combustion chamber is composed of side walls and front and rear arches. During the continuous combustion process, the side walls and the front and rear arches form a heat storage body, which exerts a strong heat radiation effect on the fuel entering the furnace to increase the drying and gasification process; preferably, in order to enhance the secondary combustion efficiency, the angles of the front and rear arches can be reduced, specifically, to 17° and 33° respectively, to reduce the space of the primary combustion chamber and increase the space of the secondary combustion chamber.

[0037] In an exemplary embodiment, the air supply system includes a primary air supply system, a secondary air supply system and a tertiary air supply system.

[0038] In an exemplary embodiment, the primary air supply system includes a primary air fan and a primary air supply duct. The primary air fan supplies air to the primary combustion chamber through the primary air supply duct and the air supply port located below the reciprocating grate; preferably, the air volume of the primary air fan is adjustable.

[0039] In an exemplary embodiment, the secondary air supply system includes a secondary air fan and a secondary air supply duct. The secondary air fan supplies air to the secondary combustion chamber through the secondary air supply duct and a secondary air nozzle at the bottom of the secondary combustion chamber.

[0040] In an exemplary embodiment, the secondary air nozzles are multiple and arranged circumferentially at the bottom of the secondary combustion chamber. Preferably, the secondary air nozzles are arranged at a downward inclination of 15°. More preferably, the secondary air nozzles are arranged as high-speed reverse-mixing, horizontally cross-shaped nozzles at a downward inclination of 15° to improve gasification and combustion efficiency. The phrase "high-speed reverse-mixing, horizontally cross-shaped" means that, because the secondary air nozzles are tilted 15° downward, the secondary air is injected in a direction counter to the rising high-temperature flue gas, and the secondary air nozzles are arranged in a cross-shaped arrangement on opposite sides.

[0041] In an exemplary embodiment, the tertiary air supply system includes the smoke exhaust fan and the tertiary air supply duct. The smoke exhaust fan supplies air to the secondary combustion chamber through the tertiary air supply duct and the tertiary air nozzle in the middle and lower part of the secondary combustion chamber, and sends the low-temperature flue gas from the external exhaust chimney to the secondary combustion chamber for air distribution and temperature regulation. Preferably, the tertiary air nozzle is a spiral nozzle, which can use the centrifugal force generated by the tangential spiral to make the unburned particulate matter carried in the flue gas in the secondary combustion chamber settle and fall.

[0042] In an exemplary embodiment, a first electric butterfly valve is provided in the tertiary air supply duct, which is used to distribute air and adjust temperature through the first electric butterfly valve according to the window temperature monitored in real time in the tertiary air supply duct.

[0043] In an exemplary embodiment, the tertiary air supply duct can also be connected to the flue gas outlet duct, and is used to mix another part of the tertiary air with the flue gas at the outlet again at the flue gas outlet duct to the required process temperature, and then send it to the heat section for drying and other work links, while reducing the oxygen content in the flue gas at the outlet; preferably, the oxygen content in the flue gas at the outlet is reduced to below 8%.

[0044] In an exemplary embodiment, a second electric butterfly valve is provided between the tertiary air supply duct and the smoke outlet duct.

[0045] In an exemplary embodiment, the ash hopper may be provided below the reciprocating grate, and a slag discharger may be provided below the ash hopper. The slag discharger is connected to the ash hopper, and the burned biomass ash is continuously pushed by the reciprocating grate in the form of slag and falls into the ash hopper and is discharged by the slag discharger. Preferably, each area of ​​the reciprocating grate may be provided with a corresponding ash hopper.

[0046] In an exemplary embodiment, the biomass semi-gasification combustion device further includes a denitrification system. Preferably, the denitrification system is a selective non-catalytic reduction (SNCR) denitrification system.

[0047] In an exemplary embodiment, the denitrification system includes a plurality of reducing agent injection holes and a plurality of corresponding reducing agent spray guns, and the reducing agent injection holes and the reducing agent spray guns are located around the bottom of the secondary combustion chamber; preferably, the number of the reducing agent injection holes and the reducing agent spray guns are both 8.

[0048] The second aspect of the present application provides a biomass semi-gasification combustion method using the above-mentioned device, comprising the following steps:

[0049] S100: feeding, feeding the biomass fuel from the feeding system to the surface of the reciprocating grate at the bottom of the primary combustion chamber and burning it; preferably, the biomass fuel is fed to the surface of the reciprocating grate at the bottom of the primary combustion chamber by a double screw conveyor, a high-angle belt conveyor, an intermediate buffer bin and a hydraulic feeder and burned;

[0050] S200: Primary air supply and primary combustion, the primary air is supplied to the primary combustion chamber by the primary air supply system, the biomass fuel is partially burned in an organized manner under given conditions of the primary air, chemical heat is generated, and another portion of the biomass fuel releases combustible gas through thermal radiation; preferably, the primary air is blown into the air supply port below the reciprocating grate by the primary air fan through the primary air supply duct, the biomass fuel is partially burned in an organized manner under given conditions of the primary air, chemical heat is generated, and another portion of the biomass fuel releases combustible gas through thermal radiation;

[0051] S300: Secondary air supply and secondary combustion. The secondary air is supplied to the secondary combustion chamber by the secondary air supply system. Simultaneously, the combustible gas generated in step S200 and the mixed flue gas generated by the primary combustion rise, mix with the secondary air, and undergo secondary combustion, releasing all heat. Preferably, the secondary air is supplied to the secondary combustion chamber by the secondary air fan through the secondary air supply duct.

[0052] S400: Tertiary air supply: The low-temperature tertiary flue gas from the external chimney is sent to the secondary combustion chamber through the exhaust fan, and the air is distributed and the temperature is adjusted. At the same time, the centrifugal force generated by the tangential spiral of the tertiary air nozzle can cause the unburned particles carried in the flue gas to settle and fall;

[0053] S500: The burned biomass ash is continuously pushed by the reciprocating grate in the form of slag and falls into the ash collecting hopper, and is discharged by the slag discharger.

[0054] In an exemplary embodiment, in step S100, the hydraulic feeder can adjust the feeding time interval according to the heat load condition.

[0055] In an exemplary embodiment, the primary air provides 40% of the air volume required for complete combustion of the biomass fuel, and the secondary air provides 60% of the air volume required for complete combustion of the biomass fuel.

[0056] In an exemplary embodiment, step S400 further includes: another portion of the tertiary low-temperature flue gas from the external exhaust chimney is mixed again with the flue gas after secondary combustion at the flue gas outlet pipe, and after being cooled to the required temperature, is sent to the heat section for drying and other work-performing links.

[0057] In an exemplary embodiment, the method further includes a denitration step, which occurs during step S300 and includes:

[0058] A reducing agent spray gun and a reducing agent injection hole are provided around the bottom of the secondary combustion chamber. Preferably, the reducing agent spray gun and the reducing agent injection hole are provided at a temperature window of 950-1000°C around the bottom of the secondary combustion chamber.

[0059] The diluted reducing agent is mixed with the flue gas rising in the secondary combustion chamber to generate a reduction reaction, thereby reducing the nitrogen oxide harmful gas in the flue gas into nitrogen.

[0060] In an exemplary embodiment, in the secondary combustion chamber, the reducing agent is sprayed into the secondary combustion chamber in an atomized form from the bottom thereof, and rises at a low speed of 2.3 m / s into the secondary combustion chamber, and the rising residence time of the flue gas in the furnace is maintained at more than 3.5 seconds.

[0061] Compared with the existing technology, this application has the following technical effects:

[0062] 1) The biomass semi-gasification combustion device is provided with a four-stage driven reciprocating grate, and the operating speed of the grate in each zone can be adjusted separately, thereby increasing the adjustable range of the output thermal power and thus improving the regulation ratio;

[0063] 2) The gasification combustion ratio of biomass fuel is increased (over 60%), wherein the air content ratio of primary air to secondary air is 2:3. At the same time, the space for secondary combustion is expanded, providing a large furnace for secondary combustion;

[0064] 3) Reduce the excess air coefficient in the flue gas after combustion (the oxygen content of the tail gas is less than 8%) to achieve energy-saving combustion;

[0065] 4) The secondary combustion chamber adopts reverse mixing and horizontal cross-type secondary air nozzles to improve gasification and combustion efficiency;

[0066] 5) The tertiary air in the biomass semi-gasification combustion device can also be returned to the primary combustion chamber to adjust the temperature of the primary combustion;

[0067] 6) The biomass semi-gasification combustion device includes an integrated SNCR denitrification system;

[0068] 7) The biomass semi-gasification combustion device is conducive to forming a high-power biomass thermal energy center integrating drying and calcining.

[0069] The present application is further described in detail below in conjunction with the embodiments, but this does not limit the present application. Any equivalent replacements in the field of interest made in accordance with the disclosure of this application shall fall within the scope of protection of this application.

[0070] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0071] Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be understood to indicate or imply relative importance or to implicitly indicate the quantity of the technical features being referred to. Thus, a feature defined as "first," "second," etc. may explicitly or implicitly include at least one of the features.

[0072] In the description of the present application, “a plurality of” means at least two, for example, two, three, etc., unless otherwise clearly and specifically defined.

[0073] In this application, unless otherwise specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, "connected" can mean fixed connection, detachable connection, or integration; it can mean mechanical connection or electrical connection; it can mean direct connection or indirect connection through an intermediate medium; it can mean internal communication between two elements or interaction between two elements, unless otherwise specified. For those skilled in the art, the specific meanings of the above terms in this application can be understood according to the specific circumstances.

[0074] In this application, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it can mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Furthermore, when a first feature is "above," "above," or "above" a second feature, it can mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it can mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0075] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example" or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0076] Example 1.

[0077] As shown in FIG1 , a biomass semi-gasification combustion device includes: a feeding system, a reciprocating grate 5, an air supply system, a combustion chamber and a smoke exhaust fan; wherein:

[0078] A flue gas outlet pipe 17 is provided on the top of the combustion chamber, and the reciprocating grate 5 is partially located in the combustion chamber; the combustion chamber includes a primary combustion chamber 7 and a secondary combustion chamber 8, the space immediately above the reciprocating grate 5 is the primary combustion chamber 7, and the space between the primary combustion chamber 7 and the flue gas outlet pipe 17 is the secondary combustion chamber 8;

[0079] The feeding system is in communication with the primary combustion chamber 7;

[0080] The exhaust fan is connected to the secondary combustion chamber 8;

[0081] The air supply system is communicated with the primary combustion chamber 7 and the secondary combustion chamber 8 respectively.

[0082] The feeding system includes a double-screw conveyor 1, a high-angle belt conveyor 2, an intermediate buffer bin 3 and a hydraulic feeder 4 connected in sequence, wherein the discharge port of the hydraulic feeder 4 is connected to the feed port of the primary combustion chamber 7.

[0083] The reciprocating grate 5 is provided with an inclined grate surface, wherein the inclination angle of the grate surface is 15°; the reciprocating grate 5 is arranged into four areas along the length direction of the inclined grate surface, wherein areas one and four each occupy 15-20% of the area of ​​the reciprocating grate 5, and areas two and three each occupy 35-40% of the area of ​​the reciprocating grate; area one of the reciprocating grate 5 is adjacent to the feed port of the primary combustion chamber 7; each area of ​​the reciprocating grate 5 is independent of each other, and the grate in each area can be driven separately, the operating speed can be adjusted separately, and the combustion state can be adjusted according to different fuel types and moisture content.

[0084] The primary combustion chamber 7 is composed of side walls and front and rear arches. During the continuous combustion process, the side walls and the front and rear arches form a heat storage body, which exerts a strong heat radiation effect on the fuel entering the furnace to increase the drying and gasification process; in order to enhance the secondary combustion efficiency, the angles of the front and rear arches can be lowered to reduce the space of the primary combustion chamber 7 and increase the space of the secondary combustion chamber 8.

[0085] The air supply system includes a primary air supply system, a secondary air supply system and a tertiary air supply system:

[0086] The primary air supply system includes a primary air fan 12 and a primary air supply duct. The primary air fan 12 supplies air to the primary combustion chamber 7 through the primary air supply duct and the air supply port located below the reciprocating grate 5. The air volume of the primary air fan 12 is adjustable.

[0087] The secondary air supply system includes a secondary air fan 13 and a secondary air supply duct. The secondary air fan 13 supplies air to the secondary combustion chamber 8 through the secondary air supply duct and the secondary air nozzle 9 at the bottom of the secondary combustion chamber 8. The secondary air nozzles 9 are multiple and located at the bottom of the secondary combustion chamber 8 and arranged circumferentially. The secondary air nozzles 9 are arranged to be tilted downward by 15 degrees and are configured as high-speed reverse mixing transverse cross nozzles to improve gasification combustion efficiency.

[0088] The tertiary air supply system includes the exhaust fan and the tertiary air supply duct. The exhaust fan passes through the tertiary air supply duct and the tertiary air nozzle 11 in the lower part of the secondary combustion chamber 8 to supply air to the secondary combustion chamber 8, and sends the low-temperature flue gas from the external exhaust chimney to the secondary combustion chamber 8 for air distribution and temperature regulation. The tertiary air nozzle 11 is a spiral nozzle, which can use the centrifugal force generated by the tangential spiral to make the secondary combustion chamber 8 The unburned particulate matter carried in the flue gas settles and falls; a first electric butterfly valve 16 is provided in the tertiary air supply duct, which is used to distribute air and adjust the temperature according to the window temperature monitored in real time in the tertiary air supply duct through the first electric butterfly valve 16; the tertiary air supply duct can also be connected to the flue gas outlet duct 17, which is used to mix another part of the tertiary air with the flue gas again at the furnace body outlet duct 17 to the required process temperature, and then send it to the heat section for drying and other work links, while reducing the oxygen content in the flue gas to below 8%; a second electric butterfly valve 19 is provided between the tertiary air supply duct and the flue gas outlet duct 17.

[0089] The ash collecting hopper 14 is provided below the reciprocating grate 5, and the slag discharger 15 is provided below the ash collecting hopper 14. The slag discharger 15 is connected to the ash collecting hopper 14. The burned biomass ash is continuously pushed by the reciprocating grate 5 in the form of slag and falls into the ash collecting hopper 14 and is discharged by the slag discharger 15. As shown in Figure 1, each area of ​​the reciprocating grate 5 is respectively provided with a corresponding ash collecting hopper.

[0090] Example 2.

[0091] As shown in Figure 1, the biomass semi-gasification combustion apparatus also includes a denitration system, which is a selective non-catalytic reduction (SNCR) denitration system. The denitration system includes multiple reductant spray guns 10 and multiple reductant injection holes, which are located around the bottom of the secondary combustion chamber 8. There are eight reductant injection holes and eight reductant spray guns.

[0092] Example 3.

[0093] As shown in FIG1 , a biomass semi-gasification combustion method using the above-mentioned device includes the following steps:

[0094] S100: Feeding, the biomass fuel is delivered to the surface of the reciprocating grate 5 at the bottom of the primary combustion chamber 7 by the double screw conveyor 1, the high-angle belt conveyor 2, the intermediate buffer bin 3 and the hydraulic feeder 4, and burned. The hydraulic feeder 4 can adjust the feeding time interval according to the heat load;

[0095] S200: Primary air supply and primary combustion. Primary air is blown into the air outlet below the reciprocating grate 5 by the primary fan 12 through the primary air supply duct, corresponding to the four zones of the reciprocating grate 5. Each zone is independent of each other, and the air volume is adjustable. The biomass fuel is partially burned in an organized manner under the given conditions of the primary air to generate chemical heat, and the other part of the biomass fuel releases combustible gas through thermal radiation.

[0096] S300: Secondary air supply and secondary combustion. The secondary air is supplied by the secondary air fan 13 through the secondary air supply duct to the secondary combustion chamber 8. At the same time, the combustible gas generated in step S200 and the mixed flue gas generated by the primary combustion rise and mix with the secondary air to cause secondary combustion and release all heat.

[0097] S400: Tertiary air supply, powered by the exhaust fan. When the actual temperature is higher than the temperature of the temperature window of the secondary combustion chamber 8, a portion of the low-temperature flue gas from the external exhaust chimney is sent to the middle and lower part of the secondary combustion chamber 8 through a pipe. The air is supplied by the nozzle 11 in the form of a spiral. The air temperature is adjusted through the first electric butterfly valve 16 according to the real-time monitored window temperature. At this time, the centrifugal force generated by the tangential spiral of the tertiary air can cause the unburned particulate matter carried in the secondary combustion flue gas to settle and fall;

[0098] S500 : The burned biomass ash is continuously pushed by the reciprocating grate 5 in the form of slag and falls into the ash collecting hopper 14 , and is discharged by the slag discharger 15 .

[0099] Example 4.

[0100] As shown in FIG1 , the biomass semi-gasification combustion method further comprises, in step S400, the following steps: after the biomass fuel is completely burned through the secondary combustion, heat energy is carried by the flue gas medium, and is mixed again with another portion of tertiary air at the flue gas outlet pipe 17 through the second electric butterfly valve 19 to the required process temperature, and then sent to the heat-using section for drying and other work-performing links. At this time, the main function of the tertiary air is to adjust the temperature and reduce the oxygen content of the flue gas to below 8%.

[0101] Example 5.

[0102] As shown in FIG1 , the biomass semi-gasification combustion method further includes a denitration step for removing nitrogen oxides generated during the combustion process. The denitration step occurs during the secondary combustion process of step S300 and includes:

[0103] Eight reducing agent injection holes and corresponding reducing spray guns 10 are set at the 950-1000°C temperature window around the bottom of the secondary combustion chamber 8. The diluted reducing agent is mixed with the rising flue gas in the secondary combustion chamber to produce a reduction reaction, reducing the nitrogen oxide harmful gas in the flue gas to nitrogen. Among them, in order to improve the sufficiency of the reduction reaction, first, the reducing agent needs to be evenly mixed and distributed in the flue gas, second, the reaction time needs to be extended, that is, the residence time of the flue gas reduction reaction stage needs to be extended, and third, the stability of the temperature window needs to be monitored online to avoid direct oxidation of the reducing agent to nitric oxide due to excessively high temperature, and at the same time, the reducing agent does not have time to react and ammonia escape occurs due to excessively low temperature.

[0104] Therefore, an integrated secondary combustion chamber 8 is provided in this embodiment, in which secondary combustion and denitrification reduction reactions are carried out simultaneously, and the reducing agent is sprayed into the bottom of the secondary combustion chamber in an atomized form, and rises at a low speed of 2.3 m / s into the secondary combustion chamber, and the rising residence time of the flue gas in the furnace is maintained at more than 3.5 seconds.

[0105] At the same time, in order to ensure the stability of the temperature window of the SNCR denitration system and the uniform distribution of the reducing agent, this embodiment designs a tertiary air system with spiral air distribution and temperature adjustment, and the tertiary air is powered by the smoke exhaust fan.

[0106] When the actual temperature is higher than the temperature window, a portion of the low-temperature flue gas from the external exhaust chimney is sent to the bottom of the secondary combustion chamber 8 through a pipeline, and air is supplied through a spiral nozzle 11. The air temperature is adjusted through the first electric butterfly valve 16 according to the real-time monitoring window temperature. The centrifugal force generated by the tangential spiral of the tertiary air can make the unburned particulate matter carried in the flue gas settle and fall, and the reducing agent in the flue gas is fully mixed and uniform in the spiral rising turbulence; after the biomass fuel is burned out through the secondary combustion, the heat energy is carried by the flue gas medium and the harmful components are removed through the denitrification reaction in the form of hot air. At the flue gas outlet pipe 17, another part of the tertiary air is mixed again to the required process temperature through the second electric butterfly valve 19 and sent to the heat-using section for drying and other work links. At this time, the main function of the tertiary air is to adjust the temperature and reduce the oxygen content of the flue gas to below 8%.

[0107] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A biomass semi-gasification combustion device, the biomass semi-gasification combustion device comprising: A feeding system, a reciprocating grate, a air supply system, a combustion chamber and a smoke exhaust fan; wherein: A flue gas outlet pipe is provided at the top of the combustion chamber, and part of the reciprocating grate is located inside the combustion chamber; the combustion chamber includes a primary combustion chamber and a secondary combustion chamber. The space adjacent to the upper part of the reciprocating grate is the primary combustion chamber, and the space between the primary combustion chamber and the flue gas outlet pipe is the secondary combustion chamber; The feeding system is communicated with the primary combustion chamber; The air supply system is communicated with the primary combustion chamber and the secondary combustion chamber respectively; The air supply system includes a primary air supply system, a secondary air supply system and a tertiary air supply system: the primary air supply system includes a primary air fan and a primary air supply pipe. The primary air fan supplies air to the primary combustion chamber through the primary air supply pipe and the air supply opening located below the reciprocating grate; the secondary air supply system includes a secondary air fan and a secondary air supply pipe. The secondary air fan supplies air to the secondary combustion chamber through the secondary air supply pipe and the secondary air nozzle at the bottom of the secondary combustion chamber; the tertiary air supply system includes the smoke exhaust fan and a tertiary air supply pipe. The smoke exhaust fan supplies air to the secondary combustion chamber through the tertiary air supply pipe and the tertiary air nozzle in the middle and lower part of the secondary combustion chamber, and sends the low-temperature flue gas from the external exhaust chimney to the secondary combustion chamber.

2. The biomass semi-gasification combustion device according to claim 1, wherein, The feeding system includes a double-screw conveyor, a high-inclination belt conveyor, an intermediate buffer bin and a hydraulic feeder connected in sequence. Wherein, the discharge port of the hydraulic feeder is connected to the feed port of the primary combustion chamber.

3. The biomass semi-gasification combustion device according to claim 1 or 2, wherein, The reciprocating grate is provided with an inclined grate surface. Preferably, the inclination angle of the grate surface is 15°; and / or The reciprocating grate is arranged in four regions along the length direction of the inclined grate surface. Among them, the first region and the fourth region each account for 15-20% of the area of the reciprocating grate, and the second region and the third region each account for 35-40% of the area of the reciprocating grate. Each region of the reciprocating grate is independent of each other, and the grate of each region can be driven separately, and the operating rate can be adjusted separately.

4. The biomass semi-gasification combustion device according to any one of claims 1 to 3, wherein, The primary combustion chamber is composed of side walls and front and rear arches; preferably, the angles of the front and rear arches are 17° and 33° respectively.

5. The biomass semi-gasification combustion device according to any one of claims 1 to 4, wherein, The number of the secondary air nozzles is multiple, and they are arranged circumferentially at the bottom of the secondary combustion chamber. Preferably, the secondary air nozzles are arranged to incline downward by 15°. More preferably, the secondary air nozzles are arranged as high-speed reverse mixing and transverse cross nozzles; and / or The tertiary air nozzle is in the form of a spiral nozzle; and / or A first electric butterfly valve is provided in the tertiary air supply pipe.

6. The biomass semi-gasification combustion device according to claim 5, wherein, The tertiary air supply pipe can also be communicated with the flue gas outlet pipe; preferably, a second electric butterfly valve is provided between the tertiary air supply pipe and the flue gas outlet pipe.

7. The biomass semi-gasification combustion device according to any one of claims 1 to 6, wherein, A ash hopper is also provided below the reciprocating grate, and a slag discharger is provided below the ash hopper. The slag discharger is communicated with the ash hopper.

8. The biomass semi-gasification combustion device according to claim 7, wherein, The biomass semi-gasification combustion device also includes a denitration system; The denitration system includes a plurality of reductant injection holes and reductant spray guns corresponding to the reductant injection holes, and the reductant injection holes and the reductant spray guns are located around the bottom of the secondary combustion chamber; preferably, the number of both the reductant injection holes and the reductant spray guns is 8.

9. A method of combustion using the biomass semi-gasification combustion device according to any one of claims 1 to 8, comprising the following steps: S100: Feeding. The biomass fuel is sent to the surface of the reciprocating grate at the bottom of the primary combustion chamber by the feeding system and burned. S200: Primary air supply and primary combustion. The primary air is sent to the primary combustion chamber by the primary air supply system. The biomass fuel is partially burned under the given conditions of the primary air in an organized manner, generating chemical heat to cause another part of the biomass fuel to release combustible gas through thermal radiation. S300: Secondary air supply and secondary combustion. The secondary air is sent to the secondary combustion chamber by the secondary air supply system. At the same time, the combustible gas generated in step S200 and the mixed flue gas generated by the primary combustion rise, mix with the secondary air and undergo secondary combustion to release all the heat. S400: Tertiary air supply. The low-temperature flue gas of the tertiary air from the external exhaust chimney is sent to the secondary combustion chamber by the induced draft fan. S500: The biomass ash after burnout continuously falls into the ash hopper in the form of slag by the reciprocating grate and is discharged by the slag discharger.

10. The method according to claim 9, wherein, The primary air provides 40% of the air volume required for the complete combustion of the biomass fuel, and the secondary air provides 60% of the air volume required for the complete combustion of the biomass fuel.

11. The method according to claim 9 or 10, wherein, Step S400 further includes: Another part of the low-temperature flue gas of the tertiary air from the external exhaust chimney is mixed with the flue gas after the secondary combustion at the flue gas outlet pipe.

12. The method according to any one of claims 9 to 11, wherein, The method further includes a denitration step, and the denitration step occurs during step S300 and includes: Reductant spray guns and reductant injection holes are provided around the bottom of the secondary combustion chamber. Preferably, the reductant spray guns and the reductant injection holes are provided at the temperature window of 950 - 1000 °C around the bottom of the secondary combustion chamber. The diluted reductant is mixed with the rising flue gas in the secondary combustion chamber, and a reduction reaction occurs to reduce the harmful nitrogen oxide gas in the flue gas to nitrogen.

13. The method according to claim 12, wherein, In the secondary combustion chamber, the reductant is atomized and sprayed into the secondary combustion chamber from the bottom, rises at a low speed with a wind speed of 2.3 m / s in the secondary combustion chamber, and the rising residence time of the flue gas in the furnace is maintained above 3.5 seconds.

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