Kinetic and potential energy conversion-driven spatial free-fluidized combustion method

Abstract

A kinetic and potential energy conversion-driven spatial free-fluidized combustion method, relating to the technical field of boiler combustion. The method comprises: calculating a total feeding amount on the basis of a total demand of boiler fuel, using a layered feeding device (6) to supply fuel to a bottom bed (1) and a spatial pneumatic screening bed (3), and performing ignition at the same time; on the basis of a total air volume required for boiler combustion, supplying primary air (4) and secondary air (5) to the bottom bed (1) and the spatial pneumatic screening bed (3); on the basis of the particle size of the fuel, adjusting the descending or ascending speed of the fuel by adjusting the ratio of the primary air (4) to the secondary air (5); monitoring the flue gas temperature in real time, and when the flue gas temperature reaches the ignition point of the fuel, enabling the layered feeding device (6) to supply fuel; and under the action of buoyancy, gravity and a suction force, coal particles on the spatial pneumatic screening bed (3) forming microcirculation in a boiler by means of changes in their own kinetic and potential energy, thereby increasing the burnout rate of the coal particles, reducing the carbon content of ash, reducing the abrasion to the boiler structure, and prolonging the period of stable operation.

Description

A spatial free fluidization combustion method driven by kinetic potential energy conversion Technical Field

[0001] The present invention relates to the technical field of boiler combustion, and in particular to a spatial free-fluidization combustion method driven by kinetic potential energy conversion. Background Art

[0002] Currently, my country's medium-sized (75-300 tons of steam) high-efficiency coal-fired boilers generally use circulating fluidized bed boiler technology, which has advantages in high thermal efficiency (90% on average), strong adaptability to coal types, low original pollutant emissions, and high desulfurization and denitrification efficiency in the furnace.

[0003] In the related art, since the fuel and the bed material participate in the circulation process together during the reaction process, a large amount of material will be circulated at a high rate, which will directly lead to high energy consumption and strong wear of the material. Summary of the Invention

[0004] The present invention provides a spatial free fluidization combustion method driven by kinetic potential energy conversion, which can effectively solve the problems of high energy consumption and strong wear of materials.

[0005] In order to solve the above technical problems, the technical solutions of the present invention are as follows:

[0006] An embodiment of the present invention provides a spatial free-fluidization combustion method driven by kinetic potential energy conversion, comprising:

[0007] The total feed amount is calculated based on the total boiler fuel demand, and fuel is supplied to the bottom bed and the space pneumatic screening bed separately through the layered feeding device, and ignition is carried out at the same time;

[0008] According to the total air volume required for boiler combustion, air is supplied to the bottom bed and the space pneumatic screening bed through primary air and secondary air;

[0009] According to the particle size of the fuel, the fuel's descending or ascending speed is adjusted by adjusting the ratio of primary air to secondary air;

[0010] Monitor the smoke temperature in real time, and when the smoke temperature reaches the ignition point of the fuel, start feeding the stratified feeding device;

[0011] Under the action of buoyancy, gravity and suction, the coal particles on the space pneumatic screening bed rely on the change of their own kinetic potential energy to produce a free fluidized state in the space, thus forming a microcirculation in the furnace.

[0012] Furthermore, the bottom bed is arranged in a furnace, and the furnace includes a furnace front wall and a furnace rear wall, and the furnace front wall is connected to the spatial pneumatic screening bed.

[0013] Furthermore, the space pneumatic screening bed is located on the upper layer of the bottom bed, and the space pneumatic screening bed has an n-layer bed structure, and the n-layer bed bodies are respectively connected to the front wall of the furnace;

[0014] The space pneumatic screening bed includes a first bed layer, a second bed layer and an nth bed layer;

[0015] The first bed is provided with a first bed surface;

[0016] The second bed is provided with a second bed surface;

[0017] The n-th bed is provided with an n-th bed surface.

[0018] Furthermore, the layered feeding device is arranged on the front wall of the furnace and is connected to the interior of the furnace;

[0019] The layered feeding device includes a bottom bed feeding device, a first layer bed feeding device, a second layer bed feeding device and an nth layer feeding device;

[0020] The bottom bed feeding device is located on the upper layer of the bottom bed;

[0021] The first bed feeding device is located on the upper layer of the first bed;

[0022] The second bed feeding device is located on the upper layer of the second bed;

[0023] The n-th layer feeding device is located on the upper layer of the n-th layer bed.

[0024] Furthermore, the primary air includes the primary air of the bottom bed, the primary air of the first bed, the primary air of the second bed and the primary air of the nth bed;

[0025] The primary air of the bottom bed is located under the bottom bed and is communicated with the interior of the furnace;

[0026] The primary air of the first bed is arranged on the front wall of the furnace, below the bed surface of the first bed, and communicated with the interior of the first bed;

[0027] The primary air of the second bed is arranged on the front wall of the furnace, below the bed surface of the second bed and communicated with the interior of the second bed;

[0028] The primary air of the nth bed layer is arranged on the front wall of the furnace, is located below the bed surface of the nth bed layer, and is communicated with the interior of the nth bed layer.

[0029] Furthermore, the secondary air is arranged on the front wall of the furnace and is in communication with the interior of the furnace; the secondary air includes the first bed secondary air, the second bed secondary air and the nth bed secondary air;

[0030] The secondary air of the first bed is located on the upper layer of the first bed feeding device;

[0031] The secondary air of the second bed is located on the upper layer of the second bed feeding device;

[0032] The secondary air of the n-th layer bed is located on the upper layer of the n-th layer feeding device.

[0033] Furthermore, the feed amount of the bottom bed is 30-40% of the total boiler fuel demand.

[0034] Furthermore, the air supply volume of the bottom bed primary air to the bottom bed is 30-40% of the total air volume required for boiler combustion; the air supply direction of the primary air to the bottom bed is perpendicular to the bottom bed surface, and air is supplied from the bottom of the bottom bed to the bottom bed surface.

[0035] Furthermore, the inclination angles of the bed surfaces of the first to nth layers of the spatial pneumatic screening bed decrease layer by layer;

[0036] The distance between the first to nth layers of the spatial pneumatic screening bed and the rear wall of the furnace increases layer by layer;

[0037] The gaps in the first to nth bed layers of the spatial pneumatic screening bed increase layer by layer.

[0038] Furthermore, the spatial free fluidization combustion method driven by kinetic potential energy conversion also includes:

[0039] The supply module is used to calculate the feeding amount of the bottom bed according to the total fuel demand of the boiler, and supply fuel to the bottom bed and the space pneumatic screening bed through the layered feeding device;

[0040] The air supply module is used to supply air to the bottom bed and the space pneumatic screening bed through primary air and secondary air according to the total air volume required for boiler combustion;

[0041] The regulating module adjusts the fuel's descending and ascending speed by adjusting the ratio of primary air to secondary air according to the particle size of the fuel;

[0042] The detection module is used to monitor the smoke temperature in real time. When the smoke temperature reaches the ignition point of the fuel, the stratified feeding device is fed.

[0043] The above solution of the present invention includes at least the following beneficial effects:

[0044] The spatial free-fluidization combustion method driven by kinetic potential energy conversion described in the present invention can enable each bed layer to share fuel and air, reduce the primary fan power of the bottom bed, and at the same time realize the staged combustion of fuel and air, reduce the combustion temperature and the possibility of fuel coking, and reduce the generation of nitrogen oxides; the coal particles can form a microcirculation in the furnace, realize fuel circulation and bed material non-circulation without relying on external circulation equipment, reduce the wear on the boiler structure, and extend the stable operation period; it can reduce the power of large fans, reduce the boiler floor space, and do not require external circulation equipment, thereby reducing investment costs and system energy consumption; the free fluidization of coal particles extends its combustion process in the boiler, is more conducive to burning, and through the multi-stage bed arrangement, the boiler's overload stable combustion capability can be made excellent. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] FIG1 is a schematic diagram of the arrangement of a free fluidized bed involved in an embodiment of the present invention;

[0046] FIG2 is a schematic diagram of the energy of coal particles involved in an embodiment of the present invention;

[0047] FIG3 is a first example of coal particle motion trajectory involved in an embodiment of the present invention;

[0048] FIG4 is a second example of the coal particle motion trajectory involved in an embodiment of the present invention;

[0049] FIG5 shows the third situation of the coal particle movement trajectory involved in the embodiment of the present invention.

[0050] Description of reference numerals:

[0051] 1. Bottom bed; 2. Furnace; 3. Space pneumatic screening bed; 4. Primary air; 5. Secondary air; 6. Layered feeding device; 21. Furnace front wall; 22. Furnace rear wall; 31. First bed layer; 32. Second bed layer; 33. Nth bed layer; 41. Bottom bed primary air; 42. First bed primary air; 43. Second bed primary air; 44. Nth bed primary air; 51. First bed secondary air; 52. Second bed secondary air; 53. Nth bed secondary air; 61. Bottom bed feeding device; 62. First bed feeding device; 63. Second-layer bed feeding device; 64. n-layer bed feeding device; 311. First-layer bed surface; 321. Second-layer bed surface; 331. n-layer bed surface; a. Inclination angle of first-layer bed surface; b. Inclination angle of second-layer bed surface; c. Inclination angle of n-layer bed surface; d. Distance between first-layer bed and rear wall of furnace; e. Distance between second-layer bed and rear wall of furnace; f. Distance between n-layer bed and rear wall of furnace; d1. Particle size of coal; m. Gap within bed layer; m1. Gap within lower bed layer; m2. Gap within upper bed layer. DETAILED DESCRIPTION

[0052] Exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0053] As shown in FIG1 to FIG5 , an embodiment of the present invention provides a spatial free fluidization combustion method driven by kinetic potential energy conversion, characterized by comprising the following steps:

[0054] The total feed amount is calculated based on the total boiler fuel demand, and fuel is supplied to the bottom bed 1 and the space pneumatic screening bed 3 respectively through the layered feeding device 6, and ignition is carried out at the same time;

[0055] According to the total air volume required for boiler combustion, air is supplied to the bottom bed 1 and the space pneumatic screening bed 3 through the primary air 4 and the secondary air 5;

[0056] According to the particle size of the fuel, the fuel's descending or ascending speed is adjusted by adjusting the ratio of the primary air 4 and the secondary air 5;

[0057] Monitor the smoke temperature in real time. When the smoke temperature reaches the ignition point of the fuel, the stratified feeding device 6 feeds the fuel.

[0058] Under the action of buoyancy, gravity and suction, the coal particles on the space pneumatic screening bed 3 generate a free fluidization state in the space by relying on the change of their own kinetic potential energy, thereby forming a microcirculation in the furnace.

[0059] In the embodiment of the present invention, the bottom bed is ignited for stable combustion and turbulent combustion, providing an upward flow of high-temperature flue gas; the feeding on the space pneumatic screening bed and the exclusive ratio of primary air and secondary air are used to achieve the effect of free fluidization combustion of coal particles on the space pneumatic screening bed; first, the fuel enters the furnace 2 from the layered feeding device 6, falls on the bottom bed 1 and the space pneumatic screening bed 5, and is ignited on the bottom bed 1; then the primary air 4 and the secondary air 5 are supplied to the bed bottom 1 and the space pneumatic screening bed 3; when the generated high-temperature flue gas moves upward to the space pneumatic screening bed 3 When the smoke temperature measuring point detects that the smoke temperature has reached the ignition point of the coal, a signal is given to the stratified feeding device 6 to allow feeding; when passing through the gap on the surface of the space pneumatic screening bed 3, due to the small gap, the pressure head here will increase, small particles of coal will be suspended, and large particles will remain on the surface of the space pneumatic screening bed 3, forming a screening effect; in addition, due to the influence of the gravity of the large particles themselves, when the inclination angle of the bed surface is between 20° and 40°, the large particles will roll down due to their own weight and enter the bottom bed 1 or the next layer of space pneumatic screening bed 3 for combustion; the secondary air 5 is arranged in the air Above the surface of the space pneumatic screening bed 3, the required oxygen is provided for the CO produced by incomplete combustion and the unburned coal particles, and convection is generated with the primary air and high-temperature flue gas, disturbing the movement of the coal particles and the flow of the flue gas, extending the combustion process and ensuring the combustion of the coal particles; by arranging the primary air 4 and the secondary air 5, the fuel and the air are shared, the staged combustion of the fuel and the air is achieved, the combustion temperature and the possibility of coking are reduced, and the generation of nitrogen oxides is reduced. In the space pneumatic screening bed 3, the fuel can be fully suspended and dispersed, thereby achieving effective screening and grading; by controlling the primary air 4, The ratio of secondary air 5 can achieve the effect of free fluidization of coal particles; fuel circulation and non-circulation of bed material are realized without relying on external circulation equipment, which reduces the wear on the boiler structure and extends the stable operation period. The free fluidization state of coal particles forms a microcirculation in the furnace. The free fluidization of coal particles extends the combustion process in the boiler and is more conducive to burning out; this combustion method is not only suitable for the combustion of coal, but also for the combustion of other solid particles, such as solid mixed pressed fuel, coal gangue, coal slime, biomass particles, etc.; the following takes coal as an example to illustrate this combustion method in detail.

[0060] As shown in FIG. 1 to FIG. 5 , the bottom bed 1 is arranged in a furnace 2 . The furnace 2 includes a furnace front wall 21 and a furnace rear wall 22 . The furnace front wall 21 is connected to the spatial pneumatic screening bed 3 .

[0061] In the embodiment of the present invention, when starting the furnace, the bottom bed 1 is ignited first. After the fuel in the bottom bed 1 burns stably, high-temperature flue gas is generated, which moves upward under the action of the fan and the density difference, thereby ensuring that the temperature of the coal particles on the spatial pneumatic screening bed 3 reaches the ignition point; the feed amount of the bottom bed 1 accounts for 30%-40% of the total fuel consumption. Since the amount of fuel allocated to the bottom bed 1 is reduced, the bed area and bed resistance are reduced accordingly, avoiding a large amount of fuel from gathering in the bottom fixed bed, thereby achieving the effect of reducing the peak combustion temperature; the front wall 21 and the rear wall 22 of the furnace are formed in one piece, which enhances the overall rigidity and stability of the furnace 2 and improves the durability and service life of the furnace 2.

[0062] As shown in Figures 1 to 5, the spatial pneumatic screening bed 3 is located on the upper layer of the bottom bed 1. The spatial pneumatic screening bed 3 is an n-layer bed structure, and the n-layer bed bodies are respectively connected to the front wall 21 of the furnace; the spatial pneumatic screening bed 3 includes a first layer bed 31, a second layer bed 32 and an n-th layer bed 33; a first layer bed surface 311 is provided on the first layer bed 31; a second layer bed surface 321 is provided on the second layer bed 32; and an n-th layer bed surface 331 is provided on the n-th layer bed 33.

[0063] In an embodiment of the present invention, a space pneumatic screening bed 3 is arranged in a spatial position of the furnace 2, and the feeding amount of the space pneumatic screening bed 3 accounts for 60%-70% of the total fuel consumption, thereby reducing the amount of fuel allocated to the bottom bed 1; a flue gas temperature measuring point is arranged above the bed surface of each layer of the space pneumatic screening bed 3. When the flue gas temperature of the high-temperature flue gas reaches the ignition point of the coal particles, a signal is given to the layered feeding device 6 to allow the fuel to enter the bed surface of the space pneumatic screening bed 3. The high-temperature flue gas provides heat to dry the coal particles, volatilize and analyze them, and make the coal particles reach the ignition point; at the same time, the high-temperature flue gas disturbs the coal particles on the bed surface of the space pneumatic screening bed 3, so that the coal particles and the flue gas are mixed and burned, and provide upward buoyancy for the coal particles; the upper space pneumatic screening bed 3 can distribute excessive fuel, appropriately increase the fluidization velocity and primary air velocity, and allow small-particle coal particles to burn in a suspended state in the space; through this free fluidization combustion, the combustion process of the coal particles in the furnace is extended, which is more conducive to burning.

[0064] As shown in Figures 1 to 5, the stratified feeding device 6 is arranged on the front wall 21 of the furnace and is connected to the interior of the furnace 1; the stratified feeding device 6 includes a bottom bed feeding device 61, a first layer bed feeding device 62, a second layer bed feeding device 63 and an n-th layer feeding device 64; the bottom bed feeding device 61 is located on the upper layer of the bottom bed 1; the first layer bed feeding device 62 is located on the upper layer of the first layer bed 31; the second layer bed feeding device 63 is located on the upper layer of the second layer bed 32; the n-th layer feeding device 64 is located on the upper layer of the n-th layer bed 33.

[0065] In an embodiment of the present invention, the interior of the furnace 2 is connected to the layered feeding device 6, realizing spatial graded feeding; the feeding of the bottom bed 1 is supplied by the bottom bed feeding device 61, and the feeding amount accounts for 30%-40% of the total fuel consumption; the feeding of the first layer bed 31 is supplied by the first layer bed feeding device 62; the feeding of the second layer bed 32 is supplied by the first layer bed feeding device 63; the feeding of the nth layer bed 33 is supplied by the nth layer bed feeding device 64; after successful ignition, the first layer feeding device 62 initially feeds about 10% of the first layer bed 31; when the flue gas temperature at the flue gas temperature measuring point above the first layer bed 31 increases significantly in a short period of time, it is judged that the first layer bed 31 has been ignited; after the ignition is stable, the load is increased, and the feeding of the first layer bed 31 and the bottom bed 1 must be increased at the same time. After the combustion is stable, the feeding of the bottom bed 1 is gradually reduced and the feeding of the pneumatic screening bed 3 in other spaces is increased.

[0066] As shown in Figures 1 to 5, the primary air 4 includes bottom bed primary air 41, first bed primary air 42, second bed primary air 43 and nth bed primary air 44; the bottom bed primary air 41 is located under the bottom bed 1 and is connected to the interior of the furnace 2; the first bed primary air 42 is arranged on the furnace front wall 21, is located under the first bed surface 311, and is connected to the interior of the first bed 31; the second bed primary air 43 is arranged on the furnace front wall 21, is located under the second bed surface 321, and is connected to the interior of the second bed 32; the nth bed primary air 44 is arranged on the furnace front wall 21, is located under the nth bed surface 331, and is connected to the interior of the nth bed 33.

[0067] In an embodiment of the present invention, the primary air 4 provides the air volume required for the combustion of coal particles in this layer; the air supply to the bottom bed 1 is supplied by the bottom bed primary air 41, which accounts for 30%-40% of the total air volume required for boiler combustion; the air supply direction of the primary air 4 to the bottom bed 1 is perpendicular to the bed surface of the bottom bed 1, and air is supplied from the bottom of the bottom bed 1 to the bed surface of the bottom bed 1; due to the reduction in the amount of fuel allocated to the bottom bed 1, the bed area and bed resistance are reduced accordingly, which reduces the pressure head of the bottom bed primary air 41 fan, thereby reducing its power; when starting the furnace, the bottom bed 1 is started first, and after the fuel in the bottom bed 1 burns stably, high-temperature flue gas is generated, which moves upward under the action of the fan and density difference; depending on the type of fuel, the temperature range of the high-temperature flue gas is also different, ensuring that the temperature of the coal particles on the first layer 31 of the spatial pneumatic screening bed reaches the ignition point.

[0068] As shown in Figures 1 to 5, the secondary air 5 is arranged on the front wall 21 of the furnace and is connected to the interior of the furnace 2; the secondary air 5 includes a first-layer bed secondary air 51, a second-layer bed secondary air 52 and an n-th-layer bed secondary air 53; the first-layer bed secondary air 51 is located on the upper layer of the first-layer bed feeding device 62; the second-layer bed secondary air 52 is located on the upper layer of the second-layer bed feeding device 63; the n-th-layer bed secondary air 53 is located on the upper layer of the n-layer feeding device 64.

[0069] In the embodiment of the present invention, the secondary air 5 is arranged above the bed surface of the spatial pneumatic screening bed 3 to provide the required oxygen for the CO produced by incomplete combustion and the unburned coal particles, and to generate convection with the primary air and high-temperature flue gas, thereby disturbing the movement of the coal particles and the flow of the flue gas, extending the combustion process, and ensuring the combustion of the coal particles.

[0070] As shown in Figures 1 to 5, the inclination angle of the bed surface of the first to n-th layers of the spatial pneumatic screening bed 3 decreases layer by layer; the distance between the first to n-th layers of the spatial pneumatic screening bed 3 and the rear wall 22 of the furnace increases layer by layer; the gap within the first to n-th layers of the spatial pneumatic screening bed 3 increases layer by layer.

[0071] In an embodiment of the present invention, the inclination angle a of the bed surface 311 of the first layer of spatial pneumatic screening, the inclination angle b of the bed surface 321 of the second layer of spatial pneumatic screening, to the inclination angle c of the bed surface 331 of the nth layer of spatial pneumatic screening are gradually decreasing; the distance d between the first layer of spatial pneumatic screening bed 31 and the rear wall 22 of the furnace, the distance e between the second layer of spatial pneumatic screening bed 32 and the rear wall 22 of the furnace, to the distance f between the nth layer of spatial pneumatic screening bed 33 and the rear wall 22 of the furnace are gradually increasing; the gap m1 in the lower bed layer is smaller than the gap m2 in the upper bed layer.

[0072] As shown in Figures 1 to 5, the supply module is used to calculate the feeding amount of the bottom bed 1 according to the total fuel demand of the boiler, and supply fuel to the bottom bed 1 and the spatial pneumatic screening bed 3 through the stratified feeding device 6; the air supply module is used to supply air to the bottom bed 1 and the spatial pneumatic screening bed 3 through the primary air 4 and the secondary air 5 according to the total air volume required for boiler combustion; the adjustment module adjusts the descending and ascending speed of the fuel by adjusting the ratio of the primary air 4 and the secondary air 5 according to the particle size of the fuel; the detection module is used to monitor the smoke temperature in real time, and when the smoke temperature reaches the ignition point of the fuel, the stratified feeding device 6 is used to feed.

[0073] In the embodiment of the present invention, ignition first requires feeding fuel to the bottom bed 1 through the bottom bed feeding device 61, and equipped with a bottom bed primary air 41, and then igniting the bed; at this time, the fuel in the bottom bed 1 accounts for about 50%-60% of the fuel required at full load, and the amount of bottom bed primary air 41 is relatively small, which belongs to oxygen-deficient combustion; the high-temperature flue gas generated moves upward to the top of the first bed 31, where there is a flue gas temperature measuring point. When the flue gas temperature reaches the ignition point of the coal type being burned, generally lignite is set at 400°C, and Class II bituminous coal is set at 550°C, a signal is given to the first bed feeding device 62, allowing the first bed 31 to be fed; the setting value of the ignition point temperature should be fed back according to the test results of the coal type being burned, and the temperature range should be within the range of 100°C. The higher point; the ignition is considered successful after the smoke temperature measuring point here reaches the ignition point temperature and lasts for a period of time; after the ignition is successful, the bottom bed feeding device 61 initially feeds about 10% to the first bed 31, and when the smoke temperature at the upper smoke temperature measuring point increases significantly in a short period of time, it is determined that the first bed 31 has been ignited; at this time, the first bed primary air 42 is gradually increased to the air volume required for the combustion of the fuel in this layer to ensure the continuous combustion of the first bed 31; after the ignition is stable, the load is increased, and the feeding of the first bed 31 and the bottom bed 1 must be increased at the same time. After the combustion is stable, the feeding of the bottom bed is reduced, and the feeding of the pneumatic screening bed 3 in other spaces is increased. Finally, the fuel amount of the bottom bed accounts for about 30% of the fuel amount required at full load. -40%; There is a smoke temperature measuring point above each bed, and the detection method is the same as that of the first bed 31; The above is to complete ignition and increase the load; After the primary air 41 of the bottom bed forms high-temperature flue gas, the buoyancy of the coal particles on the upper bed is not enough to support their suspended combustion. In forming a free fluidized state, it is mainly the primary air under each bed and the high-temperature flue gas generated by the lower bed that provide the upward power for the coal particles. The high-temperature flue gas generated by the bottom bed can only provide a small part of the buoyancy, which can directly suspend or fluidize the extremely fine coal particles for combustion; The arrangement height of each bed is different, and the initial potential energy of the coal particles is also different; The coal particles thrown from the stratified feeding device 6 themselves have a certain initial velocity, and the direction is horizontally downward; Stable combustion During combustion, the amount of fuel in the bottom bed 1 remains basically unchanged at 30%-40%. The proportion of coal particles in a free fluidized state in space is adjusted mainly by adjusting the amount of bed material and the ratio of primary air and secondary air in each layer of bed. For coal particles on the same layer of bed, there are particles that are directly turbulently burned on the bed, particles that are directly fluidized upward, and particles that fall from other upper beds. Under the same primary air and environmental conditions, the main factors that determine the degree of free fluidization are the amount of fuel, the particle size of the coal particles, and the gap between the bed surfaces. After the equipment is built, the two items are fixed values. Too much fuel will cause the primary air to be unable to penetrate the overly thick coal seam, resulting in the failure to provide power, and it is difficult for the coal particles to come into contact with oxygen, resulting in combustion stagnation.

[0074] In the embodiment of the present application, the space pneumatic screening bed 3 is not used as the ignition bed layer. When the furnace is started, the bottom bed 1 is ignited first. After the fuel in the bottom bed 1 burns stably, high-temperature flue gas is generated, which moves upward under the action of the fan and the density difference. The temperature range of the high-temperature flue gas varies depending on the type of fuel, ensuring that the temperature of the coal particles on the space pneumatic screening bed 3 reaches the ignition point; a flue gas temperature measuring point is arranged above the bed surface of the space pneumatic screening bed 3. When the temperature of the high-temperature flue gas reaches the ignition point of the coal particles, a signal is given to the feeding device 6 to allow feeding. The high-temperature flue gas provides heat to dry the coal particles, volatilize and analyze them, and reach their ignition point; the first inlet 3 provides the first inlet 3 for the combustion of the coal particles. The air volume of the first layer is 60% of the required air volume, which disturbs the coal particles on the bed surface of the space pneumatic screening bed 3, so that the coal particles and the flue gas are mixed and burned, and together with the high-temperature flue gas, they provide upward buoyancy to them; the coal particles are incompletely burned due to lack of oxygen on the bed surface of the space pneumatic screening bed, that is, CO is produced, so that the space above the bed surface of the first layer of the space pneumatic screening bed has a reducing atmosphere. The N and NOx in the coal particles are continuously reduced to N2 in this environment, thereby suppressing the generation of fuel nitrogen. At the same time, due to the lack of oxygen combustion and space combustion, the combustion peak temperature on the bed surface is reduced, the generation of thermal nitrogen is reduced, and the possibility of coking on the bed surface is also reduced. The main chemical reaction equations are as follows:

[0075] 2C+O2=2CO

[0076] 2NO+2CO=N2+2CO2

[0077] The secondary air 51 of the first bed is arranged above the first bed surface 311 of the space pneumatic screening bed, providing the required oxygen for the CO produced by incomplete combustion and the unburned coal particles, and generating convection with the primary air 4 and the high-temperature flue gas, disturbing the movement of the coal particles and the flow of the flue gas, extending the combustion process, and ensuring the combustion of the coal particles; by controlling the ratio of the primary air 4 and the secondary air 5 on the bed layer, the effect of free fluidization of the coal particles is achieved; without relying on external circulation equipment, fuel circulation and non-circulation of bed material are realized, which reduces the wear on the boiler structure and extends the stable operation. The cycle of operation is shortened; the investment cost and system energy consumption are low due to the reduction of large-scale fan power, the reduction of boiler floor space and the absence of external circulation equipment; the implementation of fuel and air classification reduces system energy consumption, achieves low-nitrogen combustion, and reduces the possibility of coal particles coking on the bed; the multi-stage bed arrangement has excellent overload stable combustion capability; the upper bed can distribute excessive fuel, appropriately increase the fluidization velocity and primary air velocity, and allow small-sized coal particles to burn in a suspended state in space; the free fluidization of coal particles extends the combustion process in the boiler, which is more conducive to burnout.

[0078] Based on the above embodiment, refer to Figure 2, which is an energy diagram of coal particles; the mechanical energy of the coal particles themselves is composed of kinetic energy and potential energy, wherein the potential energy is gravitational potential energy, and the force is reflected in the downward direction; the kinetic energy is provided by the bed primary air and high-temperature flue gas, and the force is reflected in the upward direction.

[0079] On the basis of the above embodiment, referring to FIG3 , the first situation of the movement state of coal particles is shown; the condition is that the coal particles are not burned, and the coal particles are generally forced upward. At this time, no matter what the relationship between the coal particle size dl and the gap m in the bed is, the coal particles will move upward with the flue gas; in the process of upward movement, the gravitational potential energy increases, and the mass and speed of the coal particles decrease until they are completely burned.

[0080] Based on the above embodiment, referring to Figure 4, the second situation of coal particle movement is as follows: the coal particles are unburned, the coal particles are generally forced downward, and the coal particle size d1 is smaller than the gap m2 within the upper bed layer. At this time, the coal particles will fall from the bed surface of the upper bed, which will produce two kinds of movement trajectories: one is that as the combustion progresses and the coal particles fall, the gravitational potential energy of the coal particles decreases, and the coal particles still have speed when they reach the lower bed, and the coal particles continue to burn in the lower bed. The other is that as the combustion progresses, the coal particles' movement speed drops to zero before reaching the lower bed, and they begin to move upward under the action of the upward force.

[0081] Based on the above examples, referring to Figure 5, the third scenario of coal particle motion is presented. The conditions are that the coal particles are unburned, the overall force on the coal particles is downward, and the coal particle size d1 is larger than the inter-bed gap m2 in the upper bed layer. In this scenario, the coal particles turbulently burn on the bed surface, presenting a disordered state. In this case, the spatially activated screening bed acts like a fixed bed, with the coal particles undergoing reactions such as dry distillation, pyrolysis, and combustion on the bed surface.

[0082] Due to the different stress conditions of the coal particles and the different particle sizes dl of the coal, the coal particles have the characteristic of "freely" choosing the fluidization state based on the conversion of kinetic potential energy, forming free fluidization combustion inside the furnace 2.

[0083] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for spatially free fluidized combustion driven by the conversion of kinetic and potential energy, characterized in that It includes the following steps: Calculate the total feeding amount according to the total demand of boiler fuel, and supply fuel to the bottom bed (1) and the spatial pneumatic screening bed (3) respectively through the layered feeding device (6), and ignite at the same time; Supply air to the bottom bed (1) and the spatial pneumatic screening bed (3) through the primary air (4) and the secondary air (5) according to the total air volume required for boiler combustion; Adjust the falling or rising speed of the fuel by adjusting the ratio of the primary air (4) to the secondary air (5) according to the particle size of the fuel; Monitor the flue gas temperature in real time, and when the flue gas temperature reaches the ignition point of the fuel, make the layered feeding device (6) feed; The coal particles on the spatial pneumatic screening bed (3) are under the action of buoyancy, gravity and suction force, and rely on the change of their own kinetic and potential energy to produce a state of free fluidization in space, thus forming a microcirculation in the furnace.

2. The method for space free fluidized combustion driven by kinetic and potential energy conversion according to claim 1, characterized in that The bottom bed (1) is arranged in the furnace (2), the furnace (2) includes a furnace front wall (21) and a furnace rear wall (22), and the furnace front wall (21) is connected to the spatial pneumatic screening bed (3).

3. The method for spatially free fluidized combustion driven by kinetic and potential energy conversion according to claim 2, characterized in that, The spatial pneumatic screening bed (3) is located above the bottom bed (1), the spatial pneumatic screening bed (3) is an n-layer bed structure, and the n-layer beds are respectively connected to the furnace front wall (21); The spatial pneumatic screening bed (3) includes a first-layer bed (31), a second-layer bed (32) and an nth-layer bed (33); A first-layer bed surface (311) is arranged on the first-layer bed (31); A second-layer bed surface (321) is arranged on the second-layer bed (32); An nth-layer bed surface (331) is arranged on the nth-layer bed (33).

4. The method for spatially free fluidized combustion driven by kinetic and potential energy conversion according to claim 3, characterized in that The layered feeding device (6) is arranged on the furnace front wall (21) and is connected to the inside of the furnace (1); The layered feeding device (6) includes a bottom bed feeding device (61), a first-layer bed feeding device (62), a second-layer bed feeding device (63) and an nth-layer feeding device (64); The bottom bed feeding device (61) is located above the bottom bed (1); The first-layer bed feeding device (62) is located above the first-layer bed (31); The second-layer bed feeding device (63) is located above the second-layer bed (32); The nth-layer feeding device (64) is located above the nth-layer bed (33).

5. The method for spatially free fluidized combustion driven by conversion of kinetic and potential energy according to claim 4, characterized in that, The primary air (4) includes a bottom bed primary air (41), a first-layer bed primary air (42), a second-layer bed primary air (43) and an nth-layer bed primary air (44); The bottom bed primary air (41) is located under the bottom bed (1) and is communicated with the inside of the furnace (2); The first-layer bed primary air (42) is arranged on the furnace front wall (21), under the first-layer bed surface (311), and is communicated with the inside of the first-layer bed (31); The second-layer bed primary air (43) is arranged on the furnace front wall (21), under the second-layer bed surface (321), and is communicated with the inside of the second-layer bed (32); The primary air (44) of the nth layer of bed is arranged on the front wall (21) of the furnace, below the bed surface (331) of the nth layer of bed, and is in internal communication with the nth layer of bed (33).

6. The method for space free fluidized combustion driven by kinetic and potential energy conversion according to claim 5, characterized in that The secondary air (5) is arranged on the front wall (21) of the furnace and is in internal communication with the interior of the furnace (2); the secondary air (5) includes the secondary air (51) of the first layer of bed, the secondary air (52) of the second layer of bed, and the secondary air (53) of the nth layer of bed; The secondary air (51) of the first layer of bed is located above the feeding device (62) of the first layer of bed; The secondary air (52) of the second layer of bed is located above the feeding device (63) of the second layer of bed; The secondary air (53) of the nth layer of bed is located above the feeding device (64) of the nth layer.

7. The method for spatially free fluidized combustion driven by kinetic and potential energy conversion according to claim 6, characterized in that The feeding amount of the bottom bed (1) is 30 - 40% of the total demand of boiler fuel.

8. The method for spatially free fluidized combustion driven by conversion of kinetic and potential energy according to claim 7, characterized in that, The air supply amount of the primary air (41) of the bottom bed to the bottom bed (1) is 30 - 40% of the total air volume required for boiler combustion; the air supply direction of the primary air (4) to the bottom bed (1) is perpendicular to the bed surface of the bottom bed (1), and the air is supplied from the bottom of the bottom bed (1) to the bed surface of the bottom bed (1).

9. The method for spatially free fluidized combustion driven by conversion of kinetic and potential energy according to claim 8, characterized in that The inclination angles of the bed surfaces of the first to nth layer bodies of the spatial pneumatic screening bed (3) decrease layer by layer; The distances between the first to nth layer bodies of the spatial pneumatic screening bed (3) and the rear wall (22) of the furnace increase layer by layer; The internal clearances of the first to nth layer beds of the spatial pneumatic screening bed (3) increase layer by layer.

10. The method for space free fluidized combustion driven by conversion of kinetic and potential energy according to claim 9, characterized in that, It further includes: A supply module, which is used to calculate the feeding amount of the bottom bed (1) according to the total demand of boiler fuel, and supply fuel to the bottom bed (1) and the spatial pneumatic screening bed (3) through the hierarchical feeding device (6); An air supply module, which is used to supply air to the bottom bed (1) and the spatial pneumatic screening bed (3) through the primary air (4) and the secondary air (5) according to the total air volume required for boiler combustion; An adjustment module, which adjusts the falling and rising speeds of the fuel by adjusting the ratio of the primary air (4) to the secondary air (5) according to the particle size of the fuel; A detection module, which is used to monitor the flue gas temperature in real time, and when the flue gas temperature reaches the ignition point of the fuel, makes the hierarchical feeding device (6) feed materials.

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