Small-sized gasification grate boiler for combusting bulk biomass and operation method of small-sized gasification grate boiler

Abstract

The invention discloses a small gasification grate boiler for burning biomass bulk materials and an operation method thereof.The small gasification grate boiler comprises a grate set and a gasification hearth, and the grate set comprises a gasification grate and a burnout grate which are separated by a partition wall area; a first air chamber used for supplying quantitative air to the position above the gasification fire grate is arranged below the gasification fire grate, a second air chamber used for supplying quantitative air to the position above the burnout fire grate is arranged below the burnout fire grate, and a gasification combustion space located above the gasification fire grate is defined by the gasification hearth. A secondary air inlet used for supplying quantitative air into the gasification combustion space is formed in the hearth wall of the gasification hearth, according to the small gasification grate boiler, the grate is segmented, and the air amount supplied for combustion is controlled in all stages, so that gasification combustion of fuel is achieved; and the property difference between different substances of the biomass bulk material is flattened in the gasification combustion process, so that the biomass bulk material fuel with large heat value difference can be combusted, and the operation efficiency and the cost of the boiler are not influenced.

Description

Technical Field

[0001] The present invention relates to the technical field of combustion boilers, and in particular, to a small-scale gasification grate boiler for burning biomass bulk materials and an operation method thereof. Background Art

[0002] Existing small-scale boilers have poor emission performance. When existing small-scale boilers are used to burn biomass fuels, they cannot burn them fully, and a large amount of nitrogen oxides and sulfides are generated during the combustion process, causing environmental pollution, resulting in the gradual elimination of small-scale boilers. Moreover, existing small-scale boilers can only burn biomass pellet fuels with relatively high costs and cannot burn biomass bulk materials, leading to an increase in operating costs and there is room for improvement. Summary of the Invention

[0003] The present invention aims to solve at least one of the above technical problems in the prior art to some extent. For this purpose, the present invention provides a small-scale gasification grate boiler for burning biomass bulk materials, which has good emission performance, can burn biomass bulk materials, and has low operating costs.

[0004] The present invention also provides an operation method of a small-scale gasification grate boiler for burning biomass bulk materials.

[0005] A small-scale gasification grate boiler for burning biomass bulk materials according to an embodiment of the present invention includes: a grate group, the grate group includes a gasification grate and a burnout grate separated by a partition wall, a first air chamber is arranged below the gasification grate, and the first air chamber is used to supply a certain amount of air above the gasification grate; the burnout grate is arranged at the tail end of the gasification grate, and a second air chamber is arranged below the burnout grate, and the second air chamber is used to supply a certain amount of air above the burnout grate;

[0006] A gasification furnace chamber is arranged above the gasification grate, defining a gasification combustion space, and a secondary air inlet is opened on the furnace wall of the gasification furnace chamber, and the secondary air inlet is used to supply a certain amount of air into the gasification combustion space.

[0007] The small-scale gasification grate boiler for burning biomass bulk materials according to the embodiment of the present invention realizes the gasification combustion of fuel by segmenting the grate and controlling the air supply amount during each stage of combustion. By the gasification combustion process, the property differences between different substances of the biomass bulk materials are smoothed out, so that biomass bulk materials with large calorific value differences can be burned without affecting the operation efficiency and cost of the boiler, and the emission performance is good, and the energy of the fuel can be fully released.

[0008] According to some embodiments of the present invention, the grate group includes movable grate plates and stationary grate plates arranged alternately. The movable grate plates reciprocally move along a first direction under the drive of a drive assembly. The stationary grate plates are fixedly arranged, and the reciprocating movement stroke of the movable grate plates is within a first stroke range.

[0009] According to some embodiments of the present invention, a partition board with its top sealingly cooperating with the stationary grate plates is provided in the first air chamber. The partition board divides the first air chamber into an independent and enclosed first air duct, second air duct, and third air duct. The first air duct corresponds to the drying section of the gasification grate, the second air duct corresponds to the gasification section of the gasification grate, and the third air duct corresponds to the combustion section of the gasification grate.

[0010] According to some embodiments of the present invention, no ventilation holes are provided in the drying section of the gasification grate, and air is supplied only through the gaps between the grate plates.

[0011] According to some embodiments of the present invention, the inclination angle of the gasification grate in the horizontal direction is α, and α is between 8° and 15°;

[0012] And / or, the inclination angle of the burnout grate in the horizontal direction is β, and β is between 3° and 8°.

[0013] According to some embodiments of the present invention, the gasification furnace chamber is provided with a through - opening for passing solid fuel, and a baffle is provided at the through - opening. The baffle is hinged to the side wall of the through - opening through a rotating shaft, and a counterweight is provided at its lower end.

[0014] According to some embodiments of the present invention, a heat - exchange flue is provided above the burnout grate and defines a flue gas flow path. The flue gas flow path is communicated with the smoke outlet of the gasification furnace chamber. The gasification furnace chamber, the heat - exchange flue, and the screens provided in the heat - exchange flue all adopt a full - membrane wall structure.

[0015] The present invention also proposes an operation method of a small - scale gasification grate boiler. Using the above - mentioned small - scale gasification grate boiler for burning biomass bulk materials, the operation method includes:

[0016] In the fuel gasification stage, fuel is supplied to the gasification grate, and primary air is supplied above the gasification grate through the first air chamber. The amount of the primary air is within the range of 50% to 70% of the theoretical combustion air amount required for fuel combustion. The combustible gas generated by the gasification of the fuel on the gasification grate enters the gasification combustion space;

[0017] In the gasification combustion stage, secondary air is supplied into the gasification combustion space through the secondary air inlet. The amount of the secondary air is within the range of 30% to 40% of the theoretical combustion air amount required for fuel combustion. The flue gas generated by combustion enters the heat - exchange flue.

[0018] According to some embodiments of the present invention, at least part of the structure of the gasification grate is provided with first ventilation holes, and the first ventilation holes convey air at a first wind speed, and the first wind speed is within a first wind speed range.

[0019] According to some embodiments of the present invention, the solid fuel and ash remaining after gasification of the fuel on the gasification grate are conveyed by the gasification grate to the burnout grate. In the burnout stage, tertiary air is provided above the burnout grate through the second air chamber, and the amount of the tertiary air is within the range of 15% to 20% of the theoretical combustion air amount required for fuel combustion.

[0020] According to some embodiments of the present invention, second ventilation holes are provided on the burnout grate, and the second ventilation holes convey air at a second wind speed, and the second wind speed is within a second wind speed range. Description of the Drawings

[0021] Figure 1 is a schematic structural diagram of a small gasification grate boiler according to an embodiment of the present invention;

[0022] Figure 2 is a flowchart of an operation method of a small gasification grate boiler according to an embodiment of the present invention.

[0023] Reference Numerals:

[0024] Small gasification grate boiler 100, gasification grate 1, drying section 11, gasification section 12, combustion section 13, burnout grate 2, gasification furnace chamber 3, gasification combustion space 31, secondary air inlet 32, through port 33, baffle 331, first air chamber 4, first air duct 41, second air duct 42, third air duct 43, second air chamber 5, moving grate plates 102, static grate plates 101, partition plate 6, heat exchange flue 7, screen 71, flue gas flow path 72, partition wall 9. Detailed Description of the Embodiments

[0025] The embodiments of the present invention will be described in detail below. The examples of the embodiments are shown in the drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the drawings are exemplary and are intended to explain the present invention and should not be construed as limiting the present invention.

[0026] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying 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 construed as a limitation to the present invention.

[0027] In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise specifically defined.

[0028] In the present invention, unless otherwise clearly defined and limited, the terms such as "mounted", "connected", "connected to", "fixed" and the like should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection, an electrical connection or a communication with each other; it may be directly connected, or indirectly connected through an intermediate medium, and may be the internal communication of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0029] In the present invention, unless otherwise clearly defined and limited, the first feature being "above" or "below" the second feature may include the direct contact between the first and second features, or may include the situation where the first and second features are not in direct contact but in contact through other features therebetween. Moreover, the first feature being "above", "over" and "on" the second feature includes that the first feature is directly above and obliquely above the second feature, or merely indicates that the horizontal height of the first feature is higher than that of the second feature. The first feature being "under", "beneath" and "under" the second feature includes that the first feature is directly below and obliquely below the second feature, or merely indicates that the horizontal height of the first feature is lower than that of the second feature.

[0030] The existing small boilers have poor emission performance. Moreover, when the existing small boilers are used to burn biomass fuels, they cannot burn them sufficiently, and a large amount of nitrogen oxides and sulfides are generated during the combustion process, causing environmental pollution, resulting in the gradual elimination of small boilers. In addition, the existing small boilers can only burn biomass pellet fuels with relatively high costs and cannot burn biomass bulk materials, resulting in increased operating costs.

[0031] Therefore, an embodiment of the present invention designs a small-scale gasification grate boiler 100 that can strictly control oxygen during each combustion step. Thus, the small-scale gasification grate boiler 100 can first convert the biomass bulk materials on the gasification grate into combustible gas through low-oxygen combustion with strict oxygen control. The combustible gas then enters the gasification combustion space above the gasification grate for low-nitrogen oxide combustion under gas-phase oxygen control. Since it smooths out the property differences between different substances of the biomass bulk materials during the gasification combustion stage, it promotes the formation of combustible gas with similar components for secondary combustion in the gasification combustion space. As a result, the small-scale gasification grate boiler 100 can burn biomass bulk fuel with a large calorific value difference, reducing the operating efficiency and cost of the boiler. Moreover, by controlling during the gasification combustion stage, the generation of polluting gases can be reduced, and the emission performance is better.

[0032] The following describes a small-scale gasification grate boiler 100 for burning biomass bulk materials according to an embodiment of the present invention with reference to the accompanying drawings.

[0033] The small-scale gasification grate boiler 100 for burning biomass bulk materials according to an embodiment of the present invention may include: a grate group and a gasification furnace chamber 3. The grate group includes a gasification grate 1 and a burnout grate 2 separated by a partition wall 9.

[0034] Among them, a first air chamber 4 is arranged below the gasification grate 1. The first air chamber 4 is used to supply a fixed amount of air above the gasification grate 1. The gasification furnace chamber 3 is arranged above the gasification grate 1, defining a gasification combustion space 31. A secondary air inlet 32 is also provided on the furnace wall of the gasification furnace chamber 3. The secondary air inlet 32 is used to supply a fixed amount of air into the gasification combustion space 31. The burnout grate 2 is arranged at the tail end of the gasification grate 1. A second air chamber 5 is arranged below the burnout grate 2. The second air chamber 5 is used to supply a fixed amount of air above the burnout grate 2.

[0035] Specifically, the small-scale gasification grate boiler 100 will fill fuel into the boiler regularly and quantitatively. The fuel entering the boiler first falls on the front end of the gasification grate 1 and is conveyed to the tail end of the gasification grate 1 under the conveyance of the gasification grate 1. During the process of the fuel being conveyed to the tail end, a gasification combustion reaction will occur above the gasification grate 1.

[0036] Among them, the combustible gas generated in the reaction flows upward and enters the gasification furnace chamber 3. The combustible gas will undergo low-nitrogen oxide combustion under gas-phase oxygen control in the gasification combustion space 31 defined by the gas flow furnace chamber. Thus, not only is it ensured that the combustible gas generated by the fuel is fully burned, but also the emission of harmful substances is reduced, improving the emission performance of the small-scale gasification grate boiler 100.

[0037] Furthermore, the solid fuel and ash remaining after the gasification combustion reaction are moved to the end of the gasification grate 1 driven by the gasification grate 1, and are received by the burnout grate 2 provided at the end of the gasification grate 1. The burnout grate 2 further drives the mixture of this part of solid fuel and ash to move towards the end of the burnout grate 2. During this process, the remaining part of the solid fuel is fully burned above the burnout grate 2, and the remaining ash moves to the end of the burnout grate 2, and finally they are processed together.

[0038] Since the fuel will pass through the gasification grate 1 and the burnout grate 2 in sequence during the combustion process, the staged combustion of the fuel is realized. The combustion stages are physically separated by the two grates. The gasification reaction mainly occurs on the gasification grate 1, and the burnout grate 2 mainly conducts the treatment of the residue after gasification combustion. The air volume, temperature and fuel residence time can be adjusted targeted for the two different combustion stages, reducing the energy loss caused by incomplete combustion in the small gasification grate boiler 100. For example, a lower air volume is required at the burnout grate 2 to avoid ash scattering, and a sufficient wind speed is also needed at the burnout grate 2 to enhance the disturbance and avoid ash accumulation.

[0039] In some embodiments, the temperature range at the gasification grate 1 is between 750°C and 900°C, and the temperature at the burnout grate 2 is stably controlled between 850°C and 950°C. At the gasification grate 1, the combustion temperature range between 750°C and 900°C can promote the volatilization of the volatile components in the fuel and promote the oxidation reaction of coke. At the burnout section, the combustion temperature is controlled between 850°C and 950°C, which can avoid ash coking and ensure the full combustion of residual carbon at the same time. By blowing air in stages for the gasification grate 1 and the burnout grate 2, the small gasification grate boiler 100 can adapt to the characteristics of different biomass bulk materials.

[0040] The staging of the gasification grate 1 and the burnout grate 2 also facilitates the control of the residence time of the fuel gasification combustion stage and the burnout stage above the grate. The residence time in the burnout stage needs to be extended to treat the difficult-to-combust components.

[0041] The small gasification grate boiler 100 of the present application can be used to burn biomass bulk materials. The volatile content of biomass fuel is as high as six to seven tenths of the total mass, and its combustion requires a rapid and sufficient oxygen supply. When the supplied air volume only reaches 50% to 70% of the theoretical value, the volatile components cannot be fully burned after volatilization, generating a large amount of carbon monoxide and hydrocarbons, thus enabling the gasification combustion of the fuel.

[0042] Specifically, a first air chamber 4 is arranged below the gasification grate 1. The first air chamber 4 is used to supply a fixed amount of air above the gasification grate 1. The amount of air supplied by the first air chamber 4 above the gasification grate 1 is fixed and controllable per unit time. By controlling the amount of air supplied by the first air chamber 4, it can be controlled to be the amount of air that satisfies the gasification combustion reaction of the fuel above the gasification grate 1, ensuring the normal progress of gasification combustion.

[0043] Therefore, the combustion process of the fuel above the gasification grate 1 can be maintained under an oxygen-controlled state. When the fixed amount of air supplied by the first air chamber 4 to the gasification combustion space 31 is controlled to be between 50% and 70% of the theoretical value, the biomass bulk material can first undergo gasification combustion on the gasification grate 1 to generate combustible gas.

[0044] By controlling the amount of air supplied in this stage, the gasification combustion of the biomass bulk material is realized. Through the gasification combustion process, the property differences between different substances of the biomass bulk material are smoothed, promoting it to form combustible gas with a similar composition for secondary combustion in the gasification combustion space, so that the small gasification grate boiler 100 can burn biomass bulk material fuels with a large calorific value difference without affecting the operation efficiency and cost of the boiler.

[0045] Driven by the gasification grate 1, the fuel gradually transports towards the tail end of the gasification grate 1. During the transportation process, the fuel burns under strict oxygen control in the first air zone, and the fuel will gradually gasify. The combustible gas generated during the gasification process flows upward into the gasification furnace chamber 3 arranged above the gasification grate 1.

[0046] The gasification furnace chamber 3 is arranged above the gasification grate 1, defining a gasification combustion space 31. A secondary air inlet 32 is also provided on the furnace wall of the gasification furnace chamber 3. The secondary air inlet 32 is used to supply a fixed amount of air into the gasification combustion space 31. The amount of air supplied by the secondary air inlet 32 into the gasification combustion space 31 is fixed and controllable per unit time. By controlling the amount of air supplied by the secondary air inlet 32, it can be controlled to be the amount of air that satisfies the low nitrogen oxide combustion of the combustible gas, ensuring the full combustion of the combustible gas while reducing the content of nitrogen oxides in the exhaust gas.

[0047] Therefore, the combustible gas can burn controllably in the gasification combustion space 31, limiting the combustion temperature of the combustible air while releasing the internal energy of the combustible gas, realizing low nitrogen oxide combustion with gas-phase oxygen control, and improving the emission performance.

[0048] When the fuel on the gasification grate 1 is transported to the tail end of the gasification grate 1, only part of the solid fuel and ash remain. The burnout grate 2 is arranged at the tail end of the gasification grate 1. Therefore, the remaining unburned solid fuel and ash will be pushed above the burnout grate 2 and undergo final combustion above the burnout grate 2 until the combustible substances are burned out, and the embers are collected and processed by the structure at the tail end of the burnout grate 2.

[0049] Furthermore, a second air chamber 5 is arranged below the burnout grate 2. The second air chamber 5 is used to supply a certain amount of air above the burnout grate 2. The second air chamber 5 needs to supply enough air for the sufficient combustion of the residual carbon above the burnout grate 2 to reduce the emission of carbon monoxide. At the same time, it should also avoid supplying a large amount of air resulting in ash scattering or coking.

[0050] According to the small gasification grate boiler 100 of the embodiment of the present invention, by segmenting the grate and controlling the air supply amount at each stage of combustion, the gasification combustion of the fuel is achieved. Through the gasification combustion process, the property differences between different substances of the biomass bulk materials are smoothed out, so that biomass bulk materials with large calorific value differences can be burned without affecting the operation efficiency and cost of the boiler, and the emission performance is good, and the energy of the fuel can be fully released.

[0051] Refer to Figure 1 , the grate group includes alternately arranged moving grate plates 102 and static grate plates 101. The moving grate plates 102 reciprocate along the first direction (such as Figure 1 the A - B direction shown) under the drive of the drive assembly. The static grate plates 101 are fixedly arranged. The reciprocating movement stroke of the moving grate plates 102 is within the first stroke range, and the first stroke range is greater than or equal to 150 mm and less than or equal to 200 mm.

[0052] Compared with the existing grate boilers, the reciprocating movement stroke of the moving grate plates 102 of the small gasification grate boiler 100 of the present application is relatively longer, so that it can push softer and more easily pulled biomass bulk materials, and avoid problems such as blockage or entanglement during the process of the grate group driving the biomass bulk materials to move towards the tail end.

[0053] As Figure 1 shown, a partition plate 6 with its top hermetically fitted with the static grate plate 101 is arranged in the first air chamber 4. The partition plate 6 divides the first air chamber 4 into mutually independent and closed first air duct 41, second air duct 42, and third air duct 43. The first air duct 41 corresponds to the drying section 11 of the gasification grate 1, the second air duct 42 corresponds to the gasification section 12 of the gasification grate 1, and the third air duct 43 corresponds to the combustion section 13 of the gasification grate 1.

[0054] Air is supplied above the gasification grate 1 through a first air duct 41, a second air duct 42, and a third air duct 43 respectively, so that the air volume in each section above the gasification grate 1 is controllable and the air volume in each stage is uniform. The cross-sectional dimensions of each air duct can be inversely deduced based on the reasonable flow velocity determined according to the design specifications.

[0055] The interior of the second air chamber 5 below the burnout grate 2 is also tightly partitioned by a partition plate 6 to ensure that the air volume in each stage is controllable and the air volume in each area on the burnout grate 2 is uniform.

[0056] According to some embodiments of the present invention, the drying section 11 of the gasification grate 1 is not provided with ventilation holes, and air is supplied only through the gaps between the grate plates to allow slight ventilation in the drying section 11. While ensuring that combustion does not occur in the drying section 11, the biomass bulk material can gradually release the moisture inside it during the process of passing through the drying section 11, and an appropriate air volume is used to assist the drying process to carry away the water vapor. The heat generated by gasification or combustion in adjacent areas will radiate to the drying section 11 to supply heat to the drying section 11, ensuring that the biomass bulk material quickly releases water vapor and obtains drying treatment.

[0057] Refer to Figure 1 As shown in, the inclination angle of the gasification grate 1 in the horizontal direction is α, and α is between 8° and 15°. Optionally, the inclination angle of the gasification grate 1 in the horizontal direction can be 8°, 9°, 10°, 11°, 12°, 13°, 14°, or 15°, etc.

[0058] Compared with the grate inclination angle of a traditional grate boiler, the inclination angle of the gasification grate 1 in the horizontal direction in this application is smaller, so as to reduce the auxiliary effect of gravity on the movement of the biomass bulk material towards the tail of the gasification grate 1, slow down the movement speed of the fuel on the gasification grate 1, and the fuel stays on the gasification grate 1 for a longer time, which is beneficial to the full gasification combustion of the biomass bulk material on the gasification grate 1.

[0059] Compared with traditional fuels, biomass bulk fuel has the characteristics of a larger water content and more fiber substances that are not easy to burn. Compared with traditional boilers, the small gasification grate boiler 100 in this application designs a smaller inclination angle of the grate, extends the gasification combustion time of the biomass bulk material on the grate, meets the combustion requirements of the biomass bulk material, and the biomass bulk material can be directly used as fuel and put into the small gasification grate boiler 100 in this application for combustion, reducing the fuel cost and having higher economic benefits.

[0060] As Figure 1 shown, the inclination angle of the burnout grate 2 in the horizontal direction is β, and β is between 3° and 8°. Optionally, the inclination angle of the burnout grate in the horizontal direction can be 3°, 4°, 5°, 6°, 7°, or 8°, etc.

[0061] Compared with the grate inclination angle of traditional grate boilers, the burnout grate 2 of the present application has a smaller inclination angle in the horizontal direction, so as to reduce the auxiliary effect of gravity on the movement of biomass bulk materials towards the tail of the burnout grate 2, and slow down the movement speed of the mixture of solid fuels and ashes remaining after the gasification combustion of the biomass bulk materials on the burnout grate 2, so that the mixture of solid fuels and ashes remaining after the gasification combustion of the biomass bulk materials can stay on the burnout grate 2 for a longer time for sufficient burnout.

[0062] Since the solid fuels remaining in the burnout section are more difficult-to-burn components and require a longer combustion time for treatment compared to the gasification combustion stage, therefore, the inclination angle of the burnout grate 2 of the present application in the horizontal direction is smaller than the inclination angle of the gasification grate 1 in the horizontal direction.

[0063] As Figure 1 shown, the gasification furnace chamber 3 is provided with an opening 33 for passing solid fuels, and a baffle 331 is provided at the opening 33. The baffle 331 is hinged to the side wall of the opening 33 through a rotating shaft, and a counterweight is provided at its lower end. Thus, the baffle 331 can extend vertically in the natural state and close the opening 33 to maintain the stability of the negative pressure state inside the gasification combustion space 31. When the fuels are stacked at the tail end of the gasification grate 1, the baffle 331 will rotate from the first position extending in the vertical direction to the second position opening the opening 33 under the push of the stacked fuels.

[0064] Since the baffle 331 uses mechanical feedback to control the opening and closing of the opening 33, avoiding the design of a complex sensing system, it reduces the cost and avoids abnormal system feedback in the high-temperature state, improving the reliability of the operation of the small gasification grate 1.

[0065] The small gasification grate boiler 100 further includes a heat exchange flue 7. The heat exchange flue 7 is provided above the burnout grate 2 and defines a smoke flow channel 72. The flue gas generated during the sufficient burnout of the solid fuels remaining above the burnout grate 2 will flow upward into the smoke flow channel 72 defined by the heat exchange flue 7.

[0066] The smoke flow channel 72 is communicated with the smoke outlet of the gasification furnace chamber 3, that is, the flue gas formed after the combustion of the combustible gas generated after the fuel gasification in the gasification combustion space 31 will also enter the smoke flow channel 72 defined by the heat exchange flue 7.

[0067] The inner wall of the existing small boiler adopts a conventional structure, with low heat recovery efficiency, resulting in waste of energy. The gasification furnace chamber 3, the heat exchange flue 7 and the screen 71 provided in the heat exchange flue 7 of the present application all adopt a full membrane wall structure, so as to utilize the unique structural design of the full membrane wall structure to make the flow path of the flue gas more complex, thereby improving the flow efficiency and heat exchange efficiency of the flue gas and increasing the heat recovery efficiency.

[0068] The present invention also provides an operation method for a small-scale gasification grate boiler 100, which uses the above-mentioned small-scale gasification grate boiler 100 for burning biomass bulk materials, as Figure 2 shown. The operation method includes:

[0069] S1: In the fuel gasification stage, fuel is supplied to the gasification grate 1, and primary air is supplied above the gasification grate 1 through the first air chamber 4. The amount of primary air is within the range of 50% to 70% of the theoretical combustion air amount required for fuel combustion.

[0070] In the fuel gasification stage, that is, the stage where the biomass bulk material fuel undergoes gasification combustion on the gasification grate 1, it is first necessary to supply fuel to the gasification grate 1 regularly and quantitatively. Since the fuel amount is determined, the theoretical combustion air amount required for fuel combustion can be obtained through calculation, and the air supply amounts in subsequent stages can be controlled based on the calculated theoretical combustion air amount.

[0071] Since the first air chamber 4 can supply a fixed amount of primary air above the gasification grate 1, the amount of primary air supplied by the first air chamber 4 above the gasification grate 1 can be controlled according to the value of the obtained theoretical combustion air amount, so that the amount of primary air is within the range of 50% to 70% of the theoretical combustion air amount required for fuel combustion.

[0072] Since the primary air only provides an air amount within the range of 50% to 70% of the theoretical combustion air amount, the fuel combustion on the gasification grate 1 always remains in a situation of insufficient air. The volatile content of the biomass fuel is between 60% and 70%. The high volatile content requires a rapid and sufficient oxygen supply for its combustion. When the air amount only reaches 50% to 70% of the theoretical value, the volatiles cannot be completely burned after being released, resulting in the generation of a large amount of carbon monoxide and hydrocarbons, thus realizing the gasification of the fuel. The combustible gas generated by gasification flows upward into the gasification furnace chamber 3 and enters the gasification combustion space 31.

[0073] Specifically, the small-scale gasification grate boiler 100 will fill fuel into the boiler regularly and quantitatively. The fuel entering the boiler first falls at the head end of the gasification grate 1 and is conveyed to the tail end of the gasification grate 1 under the conveyance of the gasification grate 1. During the conveyance of the fuel to the tail end, a gasification combustion reaction will occur above the gasification grate 1.

[0074] A first air chamber 4 is arranged below the gasification grate 1. The first air chamber 4 is used to supply a fixed amount of air above the gasification grate 1. The air amount supplied by the first air chamber 4 above the gasification grate 1 is fixed and controllable per unit time. By controlling the air amount supplied by the first air chamber 4, it can be controlled within the air amount required for the fuel above the gasification grate 1 to undergo a gasification combustion reaction, ensuring the normal progress of the gasification combustion.

[0075] Therefore, the combustion process of the fuel above the gasification grate 1 can be maintained under oxygen-controlled conditions. By controlling the amount of quantitative air supplied by the first air chamber 4 to the gasification combustion space 31 to be between 50% and 70% of the theoretical value, the biomass bulk material can first undergo gasification combustion on the gasification grate 1 to generate combustible gas.

[0076] By controlling the amount of air supplied in this stage, the gasification combustion of the biomass bulk material is achieved. Through the gasification combustion process, the property differences between different substances in the biomass bulk material are smoothed out, promoting the formation of combustible gas with a relatively close composition for secondary combustion in the gasification combustion space, so that the small gasification grate boiler 100 can burn biomass bulk fuel with a large calorific value difference without affecting the operation efficiency and cost of the boiler.

[0077] S21: The combustible gas generated by the gasification of the fuel on the gasification grate 1 enters the gasification combustion space 31. In the gasification combustion stage, secondary air is supplied into the gasification combustion space 31 through the secondary air inlet 32. The amount of secondary air is within the range of 30% to 40% of the theoretical combustion air amount required for fuel combustion. The flue gas generated by combustion enters the heat exchange flue 7.

[0078] Driven by the gasification grate 1, the fuel gradually transports towards the tail end of the gasification grate 1. During the transportation process, the fuel burns under strict oxygen control in the first air zone, and the fuel will gradually gasify. The combustible gas generated during the gasification process flows upward into the gasification furnace chamber 3 above the gasification grate 1.

[0079] The combustible gas generated after the fuel gasifies burns in the gasification combustion space 31. Since the secondary air inlet 32 can supply a certain amount of secondary air into the gasification combustion space 31, the amount of secondary air supplied by the secondary air inlet 32 into the gasification combustion space 31 can be controlled according to the obtained value of the theoretical combustion air amount, so that the amount of secondary air is within the range of 30% to 40% of the theoretical combustion air amount required for fuel combustion.

[0080] The secondary air can provide enough air for the complete combustion of the combustible gas, ensuring that the combustible gas can burn controllably in the gasification combustion space 31. While releasing the internal energy of the combustible gas, the combustion temperature of the combustible gas is limited, the oxygen content in the gasification combustion space 31 is controlled, and low-NOx combustion with gas-phase oxygen control is achieved. By precisely controlling the amount of oxygen entering the combustion area, the combustion process can be made more efficient, reducing the generation of nitrogen oxides caused by excessive oxygen and reducing emissions.

[0081] Specifically, the gasification furnace chamber 3 is disposed above the gasification grate 1, defining a gasification combustion space 31. A secondary air inlet 32 is further provided on the furnace wall of the gasification furnace chamber 3. The secondary air inlet 32 is used to supply a certain amount of air into the gasification combustion space 31. The amount of air supplied by the secondary air inlet 32 into the gasification combustion space 31 is quantitative and controllable per unit time. By controlling the amount of air supplied by the secondary air inlet 32 within the range of 30% to 40% of the theoretical combustion air volume, it can be controlled within the air volume that satisfies the low nitrogen oxide combustion of combustible gas, ensuring the full combustion of combustible gas while reducing the content of nitrogen oxides in the discharged gas.

[0082] Therefore, the combustible gas can burn controllably within the gasification combustion space 31, restricting the combustion temperature of the combustible air while releasing the internal energy of the combustible gas, achieving low nitrogen oxide combustion with gas-phase oxygen control, and improving the emission performance.

[0083] In some embodiments, at least part of the structure of the gasification grate 1 is provided with first ventilation holes. The air flow in the first air chamber 4 enters the gasification combustion space 31 above the gasification grate 1 through the first ventilation holes. The first ventilation holes are defined to convey air at a first wind speed, and the first wind speed is within the first wind speed range, and the first wind speed range is between 10 m / s and 15 m / s.

[0084] During the design process, the range of the primary air volume conveyed by the first air chamber 4 above the gasification grate 1 per unit time is determined, and the wind speed range at the first ventilation holes is determined. After the air volume and wind speed ranges are determined, the opening area and the number of openings of the first ventilation holes can be designed based on the wind speed data at the first ventilation holes and the total air volume data.

[0085] The wind speed at the first ventilation holes is limited within the first wind speed range, that is, between 10 m / s and 15 m / s, to ensure an appropriate ventilation hole wind speed at the first ventilation holes, ensure the uniform distribution of air above the gasification grate 1, promote the full combustion of fuel, avoid the lack of oxygen in the fuel in a local area, resulting in the inability of the fuel to achieve gasification combustion, and at the same time avoid a large amount of air circulation from taking away the heat on the gasification grate 1, ensuring the stability of fuel combustion on the gasification grate 1.

[0086] Moreover, for biomass bulk materials with a relatively high water content, a reasonable wind speed can help remove the moisture in the fuel, improve the effective calorific value of the fuel. Keeping the wind speed at the first ventilation holes within the first wind speed range can also help regulate the fuel combustion process, promote the penetration of oxygen inside the biomass bulk materials, improve the combustion reaction rate, keep the fuel in a stable combustion state, improve the thermal efficiency of the boiler, and reduce energy consumption. It helps to reduce the loss of unburned fuel and reduce the content of harmful substances in the flue gas emissions, thus meeting the environmental protection requirements and achieving the goal of energy conservation and emission reduction.

[0087] According to an embodiment of the present invention, with reference to Figure 2 , the operation method further includes:

[0088] S22: The solid fuel and ash remaining after the gasification of the fuel on the gasification grate 1 are conveyed by the gasification grate 1 to the burnout grate 2. In the burnout stage, tertiary air is provided above the burnout grate 2 through the second air chamber 5, and the amount of the tertiary air is in the range of 15% to 20% of the theoretical combustion air amount required for fuel combustion. The flue gas generated by combustion enters the heat exchange flue 7.

[0089] The amount of the tertiary air supplied by the second air chamber 5 above the burnout grate 2 is in the range of 15% to 20% of the theoretical combustion air amount required for fuel combustion, so as to supply sufficient air for the sufficient burnout of the residual carbon above the burnout grate 2, reduce the emission of carbon monoxide, and use the air flow generated during the air supply process to make the ash tumble, avoid fuel agglomeration, and at the same time avoid the ash slag scattering or coking caused by the supply of a large amount of air.

[0090] According to some embodiments of the present invention, second ventilation holes are formed in the burnout grate 2, and the air flow in the second air chamber 5 enters above the burnout grate 2 through the second ventilation holes. The second ventilation holes are defined to convey air at a second air speed, and the second air speed is within the second air speed range, and the second air speed range is between 15 m / s and 20 m / s.

[0091] During the design process, the range of the amount of the tertiary air conveyed by the second air chamber above the burnout grate 2 per unit time is determined, and the air speed range at the second ventilation holes is determined. After the air volume and air speed ranges are determined, the opening area and the number of the second ventilation holes can be designed according to the air speed data and the total air volume data at the second ventilation holes.

[0092] The air speed at the second ventilation holes is limited within the second air speed range, that is, between 15 m / s and 20 m / s, so as to ensure that the air speed of the ventilation holes at the second ventilation holes is higher than that at the gasification grate 1, not only ensure the uniform distribution of air above the burnout grate, promote the full combustion of fuel, avoid the fuel in a local area lacking oxygen and resulting in incomplete fuel combustion, but also avoid a large amount of air flow taking away the heat on the burnout grate 2 and ensure the stability of fuel combustion on the burnout grate 2.

[0093] Moreover, since a large amount of ash accumulates above the burnout grate 2, keeping the air speed at the second ventilation holes within the second air speed range can also help regulate the fuel combustion process, promote the penetration of oxygen into the interior of the ash, use the air flow to make the ash tumble, avoid fuel agglomeration, ensure the burnout effect, improve the thermal efficiency of the boiler, and reduce energy consumption. It helps to reduce the loss of unburned fuel, reduce the content of harmful substances in the flue gas emissions, thus meeting the environmental protection requirements and achieving the goal of energy conservation and emission reduction.

[0094] In the description of this specification, the descriptions referring to terms such as "one embodiment", "some embodiments", "examples", "specific examples", or "some examples", etc., mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations 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 the different embodiments or examples described in this specification.

[0095] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A small gasification grate boiler for burning biomass bulk materials, characterized in that, Comprising: A grate group, the grate group includes a gasification grate and a burnout grate separated by a partition wall. A first air chamber is arranged below the gasification grate, and the first air chamber is used to supply a fixed amount of air above the gasification grate. The burnout grate is arranged at the tail end of the gasification grate, and a second air chamber is arranged below the burnout grate, and the second air chamber is used to supply a fixed amount of air above the burnout grate; A gasification furnace chamber, the gasification furnace chamber is arranged above the gasification grate, defining a gasification combustion space. A secondary air inlet is opened on the furnace wall of the gasification furnace chamber, and the secondary air inlet is used to supply a fixed amount of air into the gasification combustion space.

2. The small-scale gasification grate boiler according to claim 1, characterized in that, The grate group includes alternately arranged moving grate plates and static grate plates. The moving grate plates reciprocate along a first direction under the drive of a drive assembly, the static grate plates are fixedly arranged, and the reciprocating movement stroke of the moving grate plates is within a first stroke range.

3. The small-scale gasification grate boiler according to claim 2, characterized in that, A partition plate with its top sealingly fitted with the static grate plate is arranged in the first air chamber. The partition plate divides the first air chamber into independent and enclosed first air duct, second air duct and third air duct. The first air duct corresponds to the drying section of the gasification grate, the second air duct corresponds to the gasification section of the gasification grate, and the third air duct corresponds to the combustion section of the gasification grate.

4. The small-scale gasification grate boiler according to claim 3, characterized in that, No ventilation holes are provided in the drying section of the gasification grate, and air is supplied only through the gaps between the grate plates.

5. The small-scale gasification grate boiler according to claim 1, characterized in that, The inclination angle of the gasification grate in the horizontal direction is α, and α is between 8° and 15°; And / or, the inclination angle of the burnout grate in the horizontal direction is β, and β is between 3° and 8°.

6. The small-scale gasification grate boiler according to claim 1, characterized in that, The gasification furnace chamber is provided with an opening for passing solid fuel, and a baffle is arranged at the opening. The baffle is hinged to the side wall of the opening through a rotating shaft, and a counterweight is arranged at its lower end.

7. The small-scale gasification grate boiler according to claim 1, characterized in that, A heat exchange flue, the heat exchange flue is arranged above the burnout grate and defines a flue gas flow path. The flue gas flow path is communicated with the smoke outlet of the gasification furnace chamber. The gasification furnace chamber, the heat exchange flue and the screens arranged in the heat exchange flue all adopt a full membrane wall structure.

8. A method for operating a small gasification grate boiler, which uses the small gasification grate boiler for burning biomass bulk materials as described in any one of claims 1 to 7, characterized in that: The operation method includes: In the fuel gasification stage, fuel is supplied to the gasification grate, and primary air is supplied above the gasification grate through the first air chamber. The amount of the primary air is within the range of 50% to 70% of the theoretical combustion air amount required for fuel combustion. The combustible gas generated by the gasification of the fuel on the gasification grate enters the gasification combustion space; In the gasification combustion stage, secondary air is supplied into the gasification combustion space through the secondary air inlet. The amount of the secondary air is within the range of 30% to 40% of the theoretical combustion air amount required for fuel combustion. The flue gas generated by combustion enters the heat exchange flue.

9. The operating method of the small-scale gasification grate boiler according to claim 8, characterized in that, The solid fuel and ashes remaining after the gasification of the fuel on the gasification grate are conveyed by the gasification grate to the burnout grate. In the burnout stage, tertiary air is provided above the burnout grate through the second air chamber. The amount of the tertiary air is within the range of 15% to 20% of the theoretical combustion air amount required for fuel combustion.

10. The operation method of the small-scale gasification grate boiler according to claim 8, characterized in that at least part of the structure of the gasification grate is provided with first ventilation holes, and air is conveyed through the first ventilation holes at a first air velocity within a first air velocity range; and / or, the burnout grate is provided with second ventilation holes, and air is conveyed through the second ventilation holes at a second air velocity within a second air velocity range.

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