A staged combustion denitration device and method for preventing material collapse in a cement kiln

Abstract

The invention discloses a staged combustion denitration device and method for preventing material collapse in a cement kiln, relating to the technical field of cement kiln denitration. In order to solve the problems that the tail gas is not treated, and when burning in the decomposition furnace, the distribution of the coal gas flow and the furnace charge is not adjusted, which will cause the phenomenon of material collapse, affecting the calcination of the furnace charge and reducing the service life of the decomposition furnace at the same time. A staged combustion denitration device and method for preventing material collapse in a cement kiln realizes staged combustion by blowing air into three combustion zones through an air supply cylinder. After being screened by a pulverized coal separator, the pulverized coal is put into a combustion cylinder, and the pulverized coal is calcined with oxygen and raw materials. The distributor is used to realize the uniform distribution of the furnace charge and the coal gas flow to avoid material collapse. The delay mechanism is used to delay the reaction time of the furnace charge in the reduction zone, so that a large amount of nitrogen oxides are reduced. The burned slaked lime falls into the material receiving pipe, and the tail gas is discharged after absorbing nitrogen ions through a nitrogen oxide cylinder, reducing the discharge rate of nitrogen oxides.

Description

Technical Field

[0001] The present invention relates to the technical field of cement kiln denitrification, and particularly relates to a staged combustion denitrification device and method for preventing material collapse in a cement kiln. Background Art

[0002] Staged combustion, also known as reburning or three-stage combustion, is characterized by dividing combustion into three zones: the main combustion zone, the reburning zone (reduction zone), and the burnout zone. The main denitrification process is mainly reflected in the reburning zone, where the reducing agent and fuel generate hydrocarbon atomic groups under high temperature and reducing atmosphere. The hydrocarbon atomic groups react with NO X generated in the main combustion zone and are reduced to N2. However, during the combustion process, the sudden drop of the burden will cause material collapse. The material collapse will cause the combustion chamber to cool rapidly, and even cause the hearth to cool severely and freeze. The reason for the material collapse is caused by the uneven distribution of the burden and the coal gas flow. When the coal gas flow is uneven and the supporting force weakens, the falling speed of the burden will change, resulting in material collapse.

[0003] Application No.: 202021833562.1 proposes a staged combustion device for external domain decomposition of a new dry process cement kiln, which improves the space utilization rate and denitrification efficiency through a decomposition furnace, a kiln tail smoke chamber, a rotary kiln, and a kiln head connected in sequence. However, this device does not treat the tail gas. There will still be a small amount of smoke remaining in the tail gas of the final combustion in the staged combustion technology. Direct emission without treatment will cause environmental hazards. At the same time, when burning in the decomposition furnace, the distribution of the coal gas flow and the burden is not adjusted, which will cause material collapse, affect the calcination of the burden, and also reduce the service life of the decomposition furnace. Summary of the Invention

[0004] The purpose of the present invention is to provide a staged combustion denitrification device and method for preventing material collapse in a cement kiln. Staged combustion is achieved by blowing air into the three combustion zones through an air supply cylinder. After being screened by a pulverized coal separator, the pulverized coal is put into a combustion cylinder, and the pulverized coal is calcined with oxygen and raw materials. The distributor is used to evenly distribute the burden and the coal gas flow to avoid material collapse. The delay mechanism is used to delay the reaction time of the burden in the reduction zone, so that a large amount of smoke is reduced. The burned slaked lime falls into the material receiving pipe, and the tail gas is discharged after absorbing nitrogen ions through a smoke cylinder, reducing the discharge of smoke, so as to solve the problems raised in the above background art.

[0005] To achieve the above purpose, the present invention provides the following technical solutions:

[0006] A staged combustion denitration device for preventing material collapse in a cement kiln, comprising a combustion cylinder, a blast pipe and a denitration mechanism. The top end of the combustion cylinder forms a feed pipe. The lower end of the feed pipe is welded with a screening pipe. The lower end of the screening pipe is welded with a blanking pipe. The lower end of the blanking pipe is welded with a staged combustion chamber. Blast pipes are symmetrically arranged on the left and right sides of the staged combustion chamber. The lower end of the staged combustion chamber is welded with a rotary kiln. The lower end of the rotary kiln is detachably connected with a material receiving pipe. A denitration mechanism is arranged on the side end of the material receiving pipe.

[0007] Further, the staged combustion chamber is sequentially provided with a main combustion zone, a reburning zone and a burnout zone from top to bottom. The main combustion zone, the reburning zone and the burnout zone are separated by a distributor. A delay mechanism is arranged in the reburning zone. A reducing agent inlet is penetrated through the outer end of the reburning zone.

[0008] Further, the distributor includes a partition plate. The partition plate is circular. The diameter length of the partition plate is greater than the diameter length of the cross-section of the staged combustion chamber. The edge of the partition plate is in an embedded connection with the inner wall of the staged combustion chamber. A plurality of guide pipes are convexly arranged in a circular array on the lower end surface of the partition plate. Through holes are penetrated in the guide pipes. The through holes vertically extend upward and penetrate through the partition plate.

[0009] Further, the delay mechanism includes a semi-circular baffle. The diameter length of the semi-circular baffle is less than the diameter length of the cross-section of the staged combustion chamber. A rotating shaft is fixedly penetrated through the middle of the semi-circular baffle. The front and rear ends of the rotating shaft are movably connected with the staged combustion chamber through bearings. The front end of the rotating shaft penetrates through the staged combustion chamber and extends to the outside of the staged combustion chamber. A gear is concentrically arranged at the end of the rotating shaft located outside the staged combustion chamber.

[0010] Further, the number of the semi-circular baffle, the rotating shaft and the gear is two and they are arranged symmetrically left and right. The two semi-circular baffles are closely connected without a gap and the through hole is located directly below the semi-circular baffle. The two gears are in meshing connection. A motor is arranged on the end surface of the left gear through a transmission rod. The motor is fixedly connected with the combustion cylinder.

[0011] Further, the feed pipe and the blanking pipe are both frustum-shaped and of equal size. The feed pipe and the blanking pipe are arranged symmetrically up and down. The upper and lower ends of the screening pipe are in a sealed connection with the feed pipe and the blanking pipe. A pulverized coal separator is arranged in the screening pipe.

[0012] Further, the air supply cylinder includes an upper cylinder, a middle cylinder, and a lower cylinder. The inner sides of the upper cylinder and the middle cylinder are respectively connected to the main combustion zone and the reburning zone through a first-stage air duct and kept in gas communication. The outer side of the upper cylinder is connected to the rotary kiln through a second-stage air duct and kept in gas communication. The lower cylinder penetrates through the grading combustion chamber and extends into the burnout zone. The cross-sections of the middle cylinder and the lower cylinder gradually shrink from the middle to the bottom. At the top of the upper cylinder, a fixed rod is connected through a connecting rod. A rotating blade is movably arranged on the rod wall of the fixed rod. The number of rotating blades is six and they are distributed in a circular array. A heating pipe is arranged at the lower end of the rotating blade in the upper cylinder. The heating pipe is spiral and the pipe wall of the heating pipe is embeddedly connected with the cylinder wall of the upper cylinder.

[0013] Further, the denitration mechanism includes a denitration cylinder. An oxidation absorption liquid containing chloric acid is filled in the denitration cylinder. A gas guide pipe penetrates through the upper end of the denitration cylinder. One end of the gas guide pipe penetrates through the rotary kiln and is kept in gas communication with the rotary kiln. The other end of the gas guide pipe penetrates through the denitration cylinder and extends into the oxidation absorption liquid. An air outlet pipe penetrates through the side end of the denitration cylinder. The end of the air outlet pipe is threadedly connected with a pipe sleeve.

[0014] Further, sealing covers are provided at the barrel openings of the combustion cylinder and the air supply cylinder. The sealing covers are movably connected to the combustion cylinder and the air supply cylinder through hinges. The hinge of the combustion cylinder is arranged at the back end, and the hinge of the air supply cylinder is arranged at the side end. A handle is provided on the sealing cover, and the handle is located at the front ends of the combustion cylinder and the air supply cylinder.

[0015] The present invention provides another technical solution, a method for staged combustion denitration of a cement kiln to prevent material collapse, including the following steps:

[0016] Step 1: Open the sealing cover, introduce the oxygen required for combustion into the air supply cylinder, and then introduce the pulverized coal required for combustion into the combustion cylinder. The pulverized coal, oxygen, and limestone raw material in the combustion cylinder are calcined in the main combustion zone to rapidly oxidize and generate a large amount of fumes. Add reducing agents such as liquid ammonia into the reducing agent addition port. The fumes are reduced to nitrogen in the reburning zone. The remaining limestone, pulverized coal, and oxygen in the burnout zone are fully combusted to regenerate a small amount of fumes.

[0017] Step 2: During the limestone calcination process, control the descending speed of the furnace charge and the ascending speed of the gas through a distributor to avoid abnormal distribution of the gas flow and the furnace charge. Uniformly feed the material through a feed pipe. The generated gas rises uniformly through the feed pipe to prevent sudden drop of the furnace charge from causing material collapse. Use a delay mechanism to control the combustion time of oxygen in the reburning zone, so that a large amount of fumes are reduced and the emission of fumes is reduced.

[0018] Step 3: Limestone is calcined and decomposed into quicklime, carbon dioxide and slaked lime. Part of the slaked lime is reduced to limestone. The reduced and unburned limestone falls into the rotary kiln for re-combustion and decomposition into slaked lime. The slaked lime is collected by the material receiving pipe. The fumes generated in the combustion cylinder and the rotary kiln pass through the denitration mechanism. The fumes are directly introduced into the hypochlorous acid oxidation absorption liquid through the air duct for absorption. NO and NO2 react with hypochlorous acid to form nitric acid and nitrous acid. The denitrated gas is then discharged from the air outlet pipe to reduce the fume discharge volume.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] 1. For a staged combustion denitration device and method for preventing material collapse in a cement kiln proposed by the present invention, the distributor adjusts the descent of the furnace charge and the ascent of the coal gas flow, enabling the furnace charge to descend evenly and the coal gas flow to ascend evenly, avoiding sudden descent of the furnace charge that may cause material collapse, resulting in a sharp cooling and freezing of the hearth, affecting the calcination quality, and reducing the service life of the combustion cylinder.

[0021] 2. For a staged combustion denitration device and method for preventing material collapse in a cement kiln proposed by the present invention, the delay mechanism prolongs the combustion time of the furnace charge and oxygen in the reburning zone, enabling NO and NO2 generated in the main combustion zone to fully react with the reducing agent, being reduced to N2 to improve the denitration rate, reduce the emission of nitrogen oxides, enhance environmental protection, and lower the production cost of enterprises.

[0022] 3. For a staged combustion denitration device and method for preventing material collapse in a cement kiln proposed by the present invention, the inlet of the combustion cylinder and the air supply cylinder is blocked by the sealing cover, allowing the tail gas to enter the denitration mechanism for tail gas treatment only through the air outlet pipe. The remaining NO and NO2 in the tail gas react with hypochlorous acid to form nitric acid and nitrous acid, reducing the content of N ions in the tail gas, and improving the denitration rate and environmental protection.

[0023] 4. For a staged combustion denitration device and method for preventing material collapse in a cement kiln proposed by the present invention, the introduced air is dispersed by the rotating blades and preheated by the heating pipes at the same time, enabling the preheated and dispersed air and the gas to burn better, while avoiding a large amount of air being sent into the combustion cylinder, which may affect the descent speed of the furnace charge and prevent the formation of material collapse. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is an axonometric view of the overall structure of the present invention;

[0025] Figure 2 is a schematic view of the sealing cover of the present invention being opened;

[0026] Figure 3 is an axonometric view of the air supply cylinder of the present invention;

[0027] Figure 4Cross-sectional view of the air supply cylinder of the present invention;

[0028] Figure 5 Axonometric view of the combustion cylinder of the present invention;

[0029] Figure 6 Cross-sectional view of the combustion cylinder of the present invention;

[0030] Figure 7 Axonometric view of the delay mechanism of the present invention;

[0031] Figure 8 Axonometric view of the distributor of the present invention;

[0032] Figure 9 Axonometric view of the denitration mechanism of the present invention.

[0033] In the figure: 1. Combustion cylinder; 11. Feeding pipe; 12. Screening pipe; 13. Discharging pipe; 14. Staged combustion chamber; 15. Reducing agent addition port; 16. Rotary kiln; 17. Material collecting pipe; 18. Pulverized coal separator; 19. Main combustion zone; 110. Reburning zone; 111. Burnout zone; 2. Air supply cylinder; 21. Upper cylinder; 22. Middle cylinder; 23. Lower cylinder; 24. Primary air duct; 25. Secondary air duct; 26. Fixed rod; 27. Connecting rod; 28. Rotating blade; 29. Heating pipe; 3. Denitration mechanism; 31. Pipe sleeve; 32. Outlet pipe; 33. Guide pipe; 34. Denitration cylinder; 4. Sealing cover; 41. Handle; 42. Hinge; 5. Delay mechanism; 51. Semi-circular baffle; 52. Rotating shaft; 53. Gear; 54. Motor; 6. Distributor; 61. Guide pipe; 62. Through hole; 63. Partition board. Detailed implementation manners

[0034] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0035] To solve the technical problems of how to achieve staged combustion in the combustion cylinder, improve the combustion rate and denitration rate, and reduce nitrogen oxide emissions, please refer to Figure 1 and Figures 5 - 6 , the following technical solutions are provided in this embodiment:

[0036] A staged combustion denitration device for preventing material collapse in a cement kiln, comprising a combustion cylinder 1, a blast pipe 2 and a denitration mechanism 3. The top end of the combustion cylinder 1 forms a feed pipe 11. The lower end of the feed pipe 11 is welded with a screening pipe 12. The lower end of the screening pipe 12 is welded with a blanking pipe 13. Both the feed pipe 11 and the blanking pipe 13 are frustum-shaped and of equal size. The feed pipe 11 and the blanking pipe 13 are arranged symmetrically up and down. The upper and lower ends of the screening pipe 12 are hermetically connected to the feed pipe 11 and the blanking pipe 13. A pulverized coal separator 18 is arranged in the screening pipe 12. The lower end of the blanking pipe 13 is welded with a staged combustion chamber 14. The staged combustion chamber 14 is successively provided with a main combustion zone 19, a reburning zone 110 and a burnout zone 111 from top to bottom. A reducing agent inlet 15 is penetrated through the outer end of the reburning zone 110. Blast pipes 2 are symmetrically arranged on the left and right sides of the staged combustion chamber 14. The lower end of the staged combustion chamber 14 is welded with a rotary kiln 16. The lower end of the rotary kiln 16 is detachably connected with a material receiving pipe 17. The denitration mechanism 3 is arranged at the side end of the material receiving pipe 17.

[0037] Specifically, oxygen required for combustion is conveyed into the combustion cylinder 1 through the blast pipe 2. Pulverized coal required for combustion is put into the combustion cylinder 1 through the feed pipe 11. The pulverized coal is finely screened through the pulverized coal separator 18. The pulverized coal with fine particles and good quality is put into the main combustion zone 19 for calcination with furnace charges such as limestone. Limestone is initially decomposed into quicklime, slaked lime and carbon dioxide. The chemical reaction formulas involved in the generation of NO and NO2 from nitrogen in the air are: N2 + O2 = 2NO, N2 + 2O2 = 2NO2, 2NO + O2 = 2NO2. Quicklime, slaked lime, carbon dioxide, NO and NO2 are then introduced into the reburning zone 110 together. A reducing agent (taking ammonia NH3 as an example) is added through the reducing agent inlet 15. The chemical reaction formulas involved in the reduction of NO and NO2 by the added reducing agent are: 4NO + 4NH3 = 4N2 + 6H2O, 2NO2 + 4NH3 + O2 = 3N2 + 6H2O, 6NO2 + 8NH3 = 7N2 + 12H2O, so that the fumes are reduced to nitrogen, reducing the emission of nitrogen oxides. At the same time, quicklime, slaked lime, carbon dioxide and N2 are introduced into the burnout zone 111 to burn the unburned limestone. A small amount of NO and NO2 are generated during the process. The chemical reaction formulas involved in the reduction of slaked lime decomposed into limestone by CO2 are: CaCO3 (limestone) = CaO (quicklime) + CO2, CaO + H2O = Ca(OH)2 (slaked lime), Ca(OH)2 + CO2 = CaCO3 + H2O. The reduced and unburned limestone are introduced into the rotary kiln 16 for final combustion. A small amount of NO and NO2 are also generated during the process. The decomposed slaked lime is collected by the material receiving pipe 17, and the remaining gas enters the denitration mechanism 3, improving the denitration rate and the emission of nitrogen oxides.

[0038] In order to solve the technical problem that the sudden drop of charge during the combustion process will cause the charge to collapse, which will cause the combustion chamber to cool down sharply and even cause the furnace to cool down and freeze, please refer to Figures 6 - 7 and Figure 8 , this embodiment provides the following technical solutions:

[0039] The main combustion zone 19, the reburning zone 110 and the burnout zone 111 are separated by a distributor 6, and the distributor 6 includes a partition 63. The partition 63 is circular in shape, and the diameter of the partition 63 is greater than the diameter of the cross section of the staged combustion chamber 14. The edge of the partition 63 is embedded in the inner wall of the staged combustion chamber 14, and a plurality of material guide pipes 61 are protruding in a ring array on the lower end surface of the partition 63. A through hole 62 is penetrated in the material guide pipe 61, and the through hole 62 extends vertically upward and penetrates the partition 63.

[0040] Specifically, different combustion zones are separated by partitions 63, and the charge will fall directly onto the partitions 63 after calcination, and then enter the guide pipe 61 through the through hole 62 for discharge, thereby avoiding collapse of the charge caused by a sudden drop of the charge. At the same time, the rising coal gas will pass through the guide pipe 61, so that the coal gas will not rise along the edge or center of the pipe wall for a long time, thereby improving the uniformity of the coal gas flow distribution, ensuring that the supporting force of the coal gas does not change suddenly, and the charge can drop steadily and evenly, reducing the probability of collapse.

[0041] In order to solve the technical problem of insufficient smoke reduction time leading to reduced denitrification rate, please refer to Figures 5 - 7 , this embodiment provides the following technical solutions:

[0042] A delay mechanism 5 is provided in the reburning zone 110, and the delay mechanism 5 includes a semicircular baffle 51. The diameter of the semicircular baffle 51 is smaller than the diameter of the cross section of the staged combustion chamber 14. A rotating shaft 52 is fixedly provided through the middle of the semicircular baffle 51. The front and rear ends of the rotating shaft 52 are movably connected to the staged combustion chamber 14 through bearings. The front end of the rotating shaft 52 passes through the staged combustion chamber 14 and extends to the outside of the staged combustion chamber 14. A gear 53 is concentrically provided at one end of the rotating shaft 52 located outside the staged combustion chamber 14.

[0043] There are two semicircular baffles 51, rotating shafts 52 and gears 53, which are symmetrically arranged on the left and right. The two semicircular baffles 51 are seamlessly and tightly connected, and the through hole 62 is located directly below the semicircular baffles 51. The two gears 53 are meshedly connected, and a motor 54 is provided on the end face of the left gear 53 through a transmission rod, and the motor 54 is fixedly connected to the combustion tube 1.

[0044] Specifically, the charging stock and the gas are blocked by the delay mechanism 5, so that the gas and the charging stock cannot enter the burnout zone 111, and the residence time of the gas and the charging stock in the reburning zone 110 is prolonged. The semi-circular baffle 51 is located directly above the through hole 62 to block the downward movement of the gas and the charging stock. When the reduction reaction ends, the motor 54 is started. The motor 54 drives the gear 53 to rotate, and the gear 53 drives another meshing gear 53 to rotate, causing both of the closed semi-circular baffles 51 to rotate downward. A gap is generated between the semi-circular baffles 51, and the gas and the charging stock can enter the through hole 62 through the gap for discharging materials.

[0045] To solve the technical problem that the density of the fed air is uneven and the temperature is relatively low, which is likely to change the temperature and the feeding speed in the combustion furnace, please refer to Figures 3 - 4 and Figure 6 This embodiment provides the following technical solutions:

[0046] The air supply cylinder 2 includes an upper cylinder 21, a middle cylinder 22, and a lower cylinder 23. The inner sides of the upper cylinder 21 and the middle cylinder 22 are respectively connected to the main combustion zone 19 and the reburning zone 110 through a first-stage air duct 24 and kept in gas communication. The outer side of the upper cylinder 21 is connected to the rotary kiln 16 through a second-stage air duct 25 and kept in gas communication. The lower cylinder 23 penetrates through the grading combustion chamber 14 and extends into the burnout zone 111. The cross-sections of the middle cylinder 22 and the lower cylinder 23 gradually shrink from the middle to the bottom. The top end of the upper cylinder 21 is provided with a fixed rod 26 connected through a connecting rod 27. A rotating blade 28 is movably arranged on the rod wall of the fixed rod 26. The number of the rotating blades 28 is six and they are distributed in a circular array. A heating pipe 29 is arranged below the rotating blade 28 in the upper cylinder 21. The heating pipe 29 is spiral and the pipe wall of the heating pipe 29 is embeddedly connected to the cylinder wall of the upper cylinder 21.

[0047] Specifically, after the air flow is introduced into the air supply cylinder 2, it passes through the rotating blade 28 and drives the rotating blade 28 to rotate. The rotating blade 28 rotates to disperse the air in the air flow, reducing the density of the air inside and preventing the uneven density of the air from being fed into the combustion cylinder 1, breaking the balance of the falling of the charging stock and the rising of the gas and causing material collapse. At the same time, before the air enters the combustion cylinder 1, it will be preheated by the heating pipe 29 to increase the internal temperature of the air, which is convenient for better combustion with the charging stock and the fuel.

[0048] To solve the technical problem that direct emission of untreated tail gas will cause environmental hazards, please refer to Figures 1 - 2 and Figure 9 This embodiment provides the following technical solutions:

[0049] Sealing covers 4 are provided at the barrel openings of both the combustion cylinder 1 and the air supply cylinder 2. The sealing covers 4 are movably connected to the combustion cylinder 1 and the air supply cylinder 2 through hinges 42. The hinge 42 of the combustion cylinder 1 is arranged at the back end, and the hinge 42 of the air supply cylinder 2 is arranged at the side end. A handle 41 is provided on the sealing cover 4, and the handle 41 is located at the front end of the combustion cylinder 1 and the air supply cylinder 2.

[0050] The denitration mechanism 3 includes a denitration cylinder 34 filled with an oxidation absorption liquid containing chloric acid. The upper end of the denitration cylinder 34 is provided with a gas guide pipe 33 penetrating through it. One end of the gas guide pipe 33 penetrates through the rotary kiln 16 and is in gas communication with the rotary kiln 16. The other end of the gas guide pipe 33 penetrates through the denitration cylinder 34 and extends into the oxidation absorption liquid. The side end of the denitration cylinder 34 is provided with an air outlet pipe 32, and the end of the air outlet pipe 32 is threadedly connected with a pipe sleeve 31.

[0051] Specifically, the sealing cover 4 seals the guiding ports of the combustion cylinder 1 and the air supply cylinder 2 to prevent the tail gas from overflowing from the tops of the combustion cylinder 1 and the air supply cylinder 2, so that the tail gas can only enter the denitration cylinder 34 through the gas guide pipe 33 and be introduced into hypochlorous acid for reaction absorption to form nitric acid and nitrous acid. The involved chemical reaction formulas are: 4NO + ClO2 - + 4OH - =4NO2 - + Cl - + 2H2O, 2NO + ClO2 - + 2OH - =2NO2 - + ClO - + H2O, 2NO2 - + ClO2 - =2NO3 - + Cl - , and the absorbed tail gas then passes through the air outlet pipe 32 to improve the denitration rate.

[0052] A method for staged combustion denitration of a cement kiln to prevent material collapse includes the following steps:

[0053] Step 1: Open the sealing cover 4, introduce the oxygen required for combustion into the air supply cylinder 2, and then introduce the pulverized coal required for combustion into the combustion cylinder 1. The pulverized coal, oxygen, and limestone raw material in the combustion cylinder 1 are calcined in the main combustion zone 19 to rapidly oxidize and generate a large amount of fumes. Add reducing agents such as liquid ammonia into the reducing agent addition port 15. The fumes are reduced to nitrogen in the reburning zone 110, and the remaining limestone, pulverized coal, and oxygen in the burnout zone 111 are fully combusted to regenerate a small amount of fumes.

[0054] Step 2: During the limestone calcination process, control the descending speed of the furnace charge and the ascending speed of the gas through the distributor 6 to avoid abnormal distribution of the gas flow and the furnace charge. Uniform feeding is carried out through the material guiding pipe 61, and the generated gas rises at a constant speed through the material guiding pipe 61 to prevent sudden drop of the furnace charge from causing material collapse. Use the delay mechanism 5 to control the combustion time of oxygen in the reburning zone 110, so that a large amount of fumes are reduced and the emission of fumes is reduced.

[0055] Step 3: The limestone is calcined and decomposed into quicklime, carbon dioxide and slaked lime. Part of the slaked lime is reduced to limestone, and the reduced and unburned limestone falls into the rotary kiln 16 for re-combustion and decomposition into slaked lime again. The slaked lime is collected by the material collecting pipe 17. The fumes generated in the combustion cylinder 1 and the rotary kiln 16 pass through the denitration mechanism 3. The fumes are directly introduced into the hypochlorous acid oxidation absorption liquid through the air duct 33 for absorption. NO and NO2 react with hypochlorous acid to form nitric acid and nitrous acid. The denitrified gas is then discharged from the air outlet pipe 32 to reduce the discharge of fumes.

[0056] In summary, a staged combustion denitration device and method for preventing material collapse in a cement kiln proposed by the present invention adjusts the descent of the furnace charge and the rise of the coal gas flow through the distributor 6, so that the furnace charge descends evenly and the coal gas flow rises evenly, avoiding the sudden descent of the furnace charge leading to material collapse, causing a sharp cooling and freezing of the hearth, affecting the calcination quality, and reducing the service life of the combustion cylinder 1; the delay mechanism 5 prolongs the combustion time of the furnace charge and oxygen in the reburning zone 110, enabling the NO and NO2 generated in the main combustion zone 19 to fully react with the reducing agent, reducing them to N2 to increase the denitrification rate, reduce the emission of nitrogen oxides, improve environmental protection, and reduce the production cost of enterprises; the sealing cover 4 blocks the inlets of the combustion cylinder 1 and the air supply cylinder 2, so that the tail gas can only enter the denitration mechanism 3 through the air outlet pipe 32 for tail gas treatment. The remaining NO and NO2 in the tail gas react with hypochlorous acid to form nitric acid and nitrous acid, reducing the content of N ions in the tail gas, and increasing the denitrification rate and environmental protection; the rotating blade 28 disperses the introduced air and preheats it using the heating pipe 29 at the same time, enabling the preheated and dispersed air to burn better with the coal gas. At the same time, it avoids a large amount of air being sent into the combustion cylinder 1, which affects the descent speed of the furnace charge and prevents the formation of material collapse.

[0057] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and should be covered by the protection scope of the present invention.

Claims

1. A staged combustion denitration device for preventing material collapse in a cement kiln, comprising a combustion cylinder (1), a blast cylinder (2) and a denitration mechanism (3), characterized in that: The top end of the combustion cylinder (1) forms a feed pipe (11). A screening pipe (12) is welded to the lower end of the feed pipe (11). A blanking pipe (13) is welded to the lower end of the screening pipe (12). A grading combustion chamber (14) is welded to the lower end of the blanking pipe (13). Air supply cylinders (2) are symmetrically arranged on the left and right sides of the grading combustion chamber (14). A rotary kiln (16) is welded to the lower end of the grading combustion chamber (14). A material receiving pipe (17) is detachably connected to the lower end of the rotary kiln (16). A denitrification mechanism (3) is arranged on the side end of the material receiving pipe (17). The grading combustion chamber (14) is successively provided with a main combustion zone (19), a reburning zone (110), and a burnout zone (111) from top to bottom. The main combustion zone (19), the reburning zone (110), and the burnout zone (111) are separated by a distributor (6). A delay mechanism (5) is arranged in the reburning zone (110). A reducing agent inlet (15) penetrates through the outer end of the reburning zone (110). The distributor (6) includes a partition plate (63). The partition plate (63) is circular. The diameter length of the partition plate (63) is greater than the diameter length of the cross-section of the grading combustion chamber (14). The edge of the partition plate (63) is in an embedded connection with the inner wall of the grading combustion chamber (14). A plurality of guide pipes (61) are convexly arranged in a circular array on the lower end surface of the partition plate (63). A through hole (62) penetrates through the guide pipe (61). The through hole (62) extends vertically upward and penetrates through the partition plate (63). Oxygen is added to the combustion cylinder (1) through the feeding port corresponding to the top sealing cover (4) of the air supply cylinder (2). Pulverized coal is input into the combustion cylinder (1) through the feed pipe (11).

2. The staged combustion denitration device for preventing material collapse in a cement kiln according to claim 1, characterized in that: The delay mechanism (5) includes a semi-circular baffle (51). The diameter length of the semi-circular baffle (51) is less than the diameter length of the cross-section of the grading combustion chamber (14). A rotating shaft (52) is fixedly penetrated through the middle of the semi-circular baffle (51). The front and rear ends of the rotating shaft (52) are movably connected to the grading combustion chamber (14) through bearings. The front end of the rotating shaft (52) penetrates through the grading combustion chamber (14) and extends outside the grading combustion chamber (14). A gear (53) is concentrically arranged at one end of the rotating shaft (52) located outside the grading combustion chamber (14).

3. The staged combustion denitration device for preventing material collapse in a cement kiln according to claim 2, characterized in that: The number of the semi-circular baffle (51), the rotating shaft (52), and the gear (53) is two and they are symmetrically arranged left and right. The two semi-circular baffles (51) are tightly connected without gaps and the through hole (62) is located directly below the semi-circular baffle (51). The two gears (53) are in meshing connection. A motor (54) is arranged on the end surface of the left gear (53) through a transmission rod. The motor (54) is fixedly connected to the combustion cylinder (1).

4. The staged combustion denitration device for preventing material collapse in a cement kiln according to claim 1, characterized in that: Both the feed pipe (11) and the blanking pipe (13) are frustum-shaped and of equal size. The feed pipe (11) and the blanking pipe (13) are symmetrically arranged up and down. The upper and lower ends of the screening pipe (12) are in a sealed connection with the feed pipe (11) and the blanking pipe (13). A pulverized coal separator (18) is arranged in the screening pipe (12).

5. The staged combustion denitration device for preventing material collapse in a cement kiln according to claim 1, characterized in that: The air supply cylinder (2) includes an upper cylinder (21), a middle cylinder (22) and a lower cylinder (23). The inner sides of the upper cylinder (21) and the middle cylinder (22) are respectively connected to the main combustion zone (19) and the reburning zone (110) through a primary air duct (24) and kept in gas communication. The outer side of the upper cylinder (21) is connected to the rotary kiln (16) through a secondary air duct (25) and kept in gas communication. The lower cylinder (23) penetrates through the classification combustion chamber (14) and extends into the burnout zone (111). The cross-sections of the middle cylinder (22) and the lower cylinder (23) gradually shrink from the middle to the bottom. At the top of the upper cylinder (21), a fixed rod (26) is connected through a connecting rod (27). A rotating blade (28) is movably arranged on the rod wall of the fixed rod (26). The number of the rotating blades (28) is six and they are distributed in an annular array. A heating pipe (29) is arranged at the lower end of the upper cylinder (21) inside the rotating blades (28). The heating pipe (29) is spiral and the pipe wall of the heating pipe (29) is embeddedly connected with the cylinder wall of the upper cylinder (21).

6. The staged combustion denitration device for preventing material collapse in a cement kiln according to claim 1, characterized in that: The denitration mechanism (3) includes a denitration cylinder (34). An oxidation absorption liquid containing chloric acid is contained in the denitration cylinder (34). A gas guide pipe (33) penetrates through the upper end of the denitration cylinder (34). One end of the gas guide pipe (33) penetrates through the rotary kiln (16) and is kept in gas communication with the rotary kiln (16). The other end of the gas guide pipe (33) penetrates through the denitration cylinder (34) and extends into the oxidation absorption liquid. An air outlet pipe (32) penetrates through the side end of the denitration cylinder (34). The end of the air outlet pipe (32) is threadedly connected with a pipe sleeve (31).

7. The staged combustion denitration device for preventing material collapse in a cement kiln according to claim 1, characterized in that: Sealing covers (4) are arranged at the barrel openings of the combustion cylinder (1) and the air supply cylinder (2). The sealing covers (4) are movably connected to the combustion cylinder (1) and the air supply cylinder (2) through hinges (42). The hinge (42) of the combustion cylinder (1) is arranged at the back end, and the hinge (42) of the air supply cylinder (2) is arranged at the side end. A handle (41) is arranged on the sealing cover (4), and the handle (41) is located at the front end of the combustion cylinder (1) and the air supply cylinder (2).

8. A method for using the staged combustion denitration device for preventing material collapse in a cement kiln according to any one of claims 1-7, characterized in that: It includes the following steps: Step 1: Open the sealing cover (4), introduce the oxygen required for combustion into the air supply cylinder (2), and then introduce the pulverized coal required for combustion into the combustion cylinder (1). The pulverized coal, oxygen and the limestone raw material in the combustion cylinder (1) are calcined in the main combustion zone (19) to rapidly oxidize and generate fumes. Liquid ammonia is added into the reducing agent addition port (15). The fumes are reduced to nitrogen in the reburning zone (110). The remaining limestone, pulverized coal and oxygen in the burnout zone (111) are fully combusted to regenerate a small amount of fumes again; Step 2: During the limestone calcination process, control the descending speed of the furnace charge and the ascending speed of the gas through the distributor (6), and uniformly feed the materials through the feed pipe (61). The generated gas rises at a constant speed through the feed pipe (61). Use the delay mechanism (5) to control the combustion time of oxygen in the reburning zone (110) so that a large amount of fumes are reduced; Step 3: Limestone is calcined and decomposed into quicklime, carbon dioxide and slaked lime. Part of the slaked lime is reduced to limestone, and the reduced and unburned limestone falls into the rotary kiln (16) for re-combustion and decomposition into slaked lime. The slaked lime is collected by the material receiving pipe (17). The fumes generated in the combustion cylinder (1) and the rotary kiln (16) pass through the denitration mechanism (3). The fumes are introduced into the hypochlorous acid oxidation absorption liquid through the gas guide pipe (33) for absorption. NO and NO2 react with hypochlorous acid to form nitric acid and nitrous acid. The denitrified gas is then discharged from the gas outlet pipe (32).

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