Rotary kiln staged zone calcination process

Abstract

The application discloses a rotary kiln grading and partition calcining process and relates to the technical field of lime, cement and other material calcining production treatment equipment. The preheater is internally provided with a pretreatment mechanism; the pretreatment mechanism comprises a feeding table arranged on the top of the preheater, a metal sieve plate fixedly installed at the bottom of the feeding table, a distribution pipe through-connected to the bottom outer edge of the metal sieve plate, and a closed plate conveyor through-installed on the lower sidewall of the preheater. Before entering the inside of the preheater, 10-20mm particle size material enters an external storage bin and is conveyed to the bottom of the preheater through the closed plate conveyor; 20-65mm particle size material is conveyed to the inside of the feeding table and is screened through the metal sieve plate. The application discloses a rotary kiln grading and partition calcining process which has the effect of greatly improving the overall preheating uniformity in view of the material size.

Description

Technical Field

[0001] This invention relates to the technical field of calcination production and processing equipment for materials such as lime and cement, and particularly to a rotary kiln graded and zoned calcination process. Background Technology

[0002] In the production of materials such as lime and cement, rotary kiln calcination systems are typically equipped with preheaters. These preheaters utilize the high-temperature flue gas from the kiln tail to preheat the materials before they enter the kiln, thereby improving calcination efficiency and reducing heat consumption. However, the materials entering the preheater often exhibit particle size differences—large and small particles enter the preheater simultaneously, resulting in significant differences in their flow behavior, heating area, and heat transfer efficiency. Small particles have a larger specific surface area and a faster heating rate, while large particles have a smaller specific surface area and lower heat transfer efficiency. This leads to uneven temperatures when the two particles enter the calcination equipment at the preheater outlet. This uneven preheating directly affects the stability of subsequent calcination processes, causing small particles to be over-burned while those encased in larger particles are under-burned, ultimately impacting product quality and yield.

[0003] To address the aforementioned issues, existing technologies include setting up material distribution or spreading devices inside the preheater. However, most of these solutions focus on the uniform distribution of materials after they enter the preheater, failing to fundamentally solve the problem of uneven preheating caused by different particle sizes due to variations in preheating paths and heating processes. Summary of the Invention

[0004] This invention discloses a rotary kiln graded and zoned calcination process, which aims to solve the technical problem of uneven preheating caused by material particle size differences in existing rotary kiln preheating systems.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A rotary kiln graded and zoned calcination process includes a preheater, the preheater having a pretreatment mechanism inside for graded preheating of materials.

[0007] The pretreatment mechanism includes a feeding platform mounted on the top of the preheater. A metal screen plate is fixedly installed at the bottom of the feeding platform. Several evenly distributed distribution pipes are connected through the bottom outer edge of the metal screen plate. The distribution pipes are connected through the interior of the preheater. A closed plate conveyor is installed through the lower side wall of the preheater.

[0008] Before entering the preheater, the raw materials are first screened by a double-layer drum screen, with two particle sizes: 10-20mm and 20-65mm. The 10-20mm particles enter the external storage silo and are conveyed to the bottom of the preheater by the enclosed conveyor. The 20-65mm particles are conveyed to the inside of the feeding platform and screened by the metal screen plate. The 40-65mm particles accumulate inside the distribution pipe, while the 20-40mm particles fall off from the metal screen plate and cover the top of the 10-20mm particles. Then, the 40-65mm particles inside the distribution pipe are discharged and cover the top of the 20-40mm particles. The 40-65mm, 20-40mm, and 10-20mm particles are distributed sequentially from top to bottom and, after preheating, enter the rotary kiln for calcination.

[0009] Based on rotary kiln preheating equipment and technology, this equipment incorporates a pretreatment mechanism inside the preheater for grading the materials to be processed. Unlike traditional equipment that considers the uniformity of material mixing, this equipment utilizes an external double-layer rotary screen to initially screen materials of 10-20mm and 20-65mm sizes. A closed conveyor belt first introduces 10-20mm particles into the preheater, and then the 20-65mm particles are further screened through batch operation of metal screen plates and distribution pipes. This allows 40-65mm, 20-40mm, and 10-20mm particles to be distributed sequentially from top to bottom. This overcomes the problem of large differences in the preheating process of different particle sizes in traditional mixed feeding methods. Larger particles receive sufficient preheating time during the longer feeding path and grading process, resulting in more uniform temperatures and preheating uniformity for different particles. This provides a more uniform feed material for subsequent calcination.

[0010] In a preferred embodiment, the preheater is provided with a feeding chamber, a middle feeding chamber, and a feeding chamber in sequence. 20-40mm particle size material that has been screened by the metal sieve plate is piled up in the middle feeding chamber and below, and 40-65mm particle size material is piled up in the feeding chamber area.

[0011] By setting the bottom of the preheater into three parts—the feeding chamber, the middle chamber, and the feeding chamber—and coordinating with the operation of the pretreatment mechanism and utilizing different material stacking positions, the heating time of the materials can be controlled. Materials with a particle size of 40-65mm are heated for a longer time, while materials with a particle size of 10-20mm are heated for a shorter time. This ensures that different materials are heated to the same degree before entering the rotary kiln, maintaining the functionality of this process.

[0012] In a preferred embodiment, a vent is fixedly installed inside the preheater. The vent is distributed inside the intermediate material chamber and the feeding chamber. The vent is fixedly installed inside the preheater by several connecting brackets. The surface of the vent has several densely distributed vents, and the diameter of the vents increases from bottom to top.

[0013] By installing a vent hood structure inside the preheater, directly facing the preheater's feed pipe inlet, the elevated vent hood provides circulation space for the high-temperature gas flowing back from the rotary kiln. At the same time, the vents on the surface of the vent hood utilize the characteristic of gradually increasing aperture from bottom to top to accommodate stratified materials with particle sizes of 40-65mm, 20-40mm, and 10-20mm, providing different degrees of preheating effect for each type, thereby improving the uniformity and perfection of the processed materials in this process.

[0014] In a preferred embodiment, each of the distributing tubes has an electric pusher plate slidably inserted inside. The electric pusher plate shields the 40-65mm particle size material located inside the distributing tube. The side wall of the distributing tube has a through-hole, through which the electric pusher plate is slidably inserted into the inside of the distributing tube.

[0015] By further installing an electric push plate structure along the inside of the distribution pipe, the closing of the distribution pipe is controlled by the electric push plate, and the falling time of the 40-65mm particle size material inside the distribution pipe is controlled, so as to complete the superposition and preheating of the 40-65mm particle size material and the 20-40mm particle size material, thereby improving the efficiency of the equipment operation.

[0016] As can be seen from the above, the rotary kiln graded and zoned calcination process provided by the present invention has the following technical effects.

[0017] This process and equipment differ from traditional preheating equipment that only considers the uniformity of material mixing. It utilizes an external double-layer rotary screen to initially screen materials of 10-20mm and 20-65mm sizes. A closed-loop conveyor first guides the 10-20mm particles to the bottom of the preheater, where they are further screened in batches by metal screen plates and distribution pipes. This results in a sequential distribution of 40-65mm, 20-40mm, and 10-20mm particles from top to bottom, thus changing the traditional mixed feeding method. To address the issue of significant differences in preheating processes for materials of different particle sizes, this application provides a longer feeding path for large particles, allowing them sufficient preheating time, while the preheating path for small particles is shorter, preventing overheating and avoiding uneven preheating caused by small particles being encapsulated by large particles. This improves the overall uniformity of material preheating, thereby increasing the production capacity for subsequent calcination in the kiln. Furthermore, by utilizing countercurrent heat exchange with high-temperature flue gas, large particles can fully contact and exchange heat with high-temperature flue gas during their longer feeding path and staged residence time inside the preheater, thus improving the pre-decomposition rate. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall structure proposed in this invention.

[0019] Figure 2 This is a schematic diagram of the internal structure of the preheater proposed in this invention.

[0020] Figure 3 This is a cross-sectional view of the overall structure proposed in this invention.

[0021] Figure 4 This is an exploded view of the pretreatment mechanism structure proposed in this invention.

[0022] Figure 5 This is a front view of the internal structure of the device proposed in this invention.

[0023] Figure 6 This describes the particle size distribution of materials with a particle size of 10-20mm according to the present invention.

[0024] Figure 7 This describes the particle size distribution of materials with a particle size of 20-40mm according to the present invention.

[0025] Figure 8 This describes the particle size distribution of materials with a particle size of 40-65mm according to the present invention.

[0026] In the diagram: 1. Preheater; 101. Feeding chamber; 102. Intermediate material chamber; 103. Feeding chamber; 2. Pre-treatment mechanism; 201. Feeding platform; 202. Metal sieve plate; 203. Distributor pipe; 2031. Inlet; 204. Vent hood; 2041. Connecting frame; 2042. Vent; 205. Enclosed plate conveyor; 206. Electric push plate; 207. Sealing plate; 3. Feeding pipe; 4. Hydraulic push rod. Detailed Implementation

[0027] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0028] The rotary kiln grading and partitioning calcination process disclosed in this invention is mainly applied to scenarios where materials of different sizes are preheated simultaneously.

[0029] Reference Figures 1 to 8 A rotary kiln graded and zoned calcination process includes a preheater 1, and the preheater 1 is equipped with a pretreatment mechanism 2 for graded preheating of materials.

[0030] The pretreatment mechanism 2 includes a feeding platform 201 mounted on top of the preheater 1. A metal screen plate 202 is fixedly installed at the bottom of the feeding platform 201. Several evenly distributed distribution pipes 203 are connected through the bottom outer edge of the metal screen plate 202. The distribution pipes 203 are connected through the interior of the preheater 1. A closed plate conveyor 205 is installed through the lower side wall of the preheater 1.

[0031] Before entering the preheater 1, the raw materials are first screened by a double-layer drum screen, with two particle sizes in the screening interval: 10-20mm and 20-65mm. The 10-20mm particles enter the external storage silo and are then conveyed to the discharge pipe 3 at the bottom of the preheater 1 by a closed conveyor 205. The 20-65mm particles are conveyed to the inside of the feeding platform 201, screened by the metal screen plate 202, and the 40-65mm particles accumulate in the distribution pipe. Inside 203, 20-40mm particle size material falls off from inside the metal sieve plate 202 and covers the top of 10-20mm particle size material; then, 40-65mm particle size material located inside the distribution pipe 203 is fed out and covers the top of 20-40mm particle size material. The 40-65mm particle size material, 20-40mm particle size material and 10-20mm particle size material are distributed from top to bottom in sequence, and after preheating, they enter the rotary kiln for calcination.

[0032] In this embodiment: Before entering the preheater 1, the raw materials to be processed are first screened by an external double-layer drum screen. The screening interval has two particle sizes: 10-20mm and 20-65mm. After screening, the 10-20mm particle size material enters the external storage silo and is conveyed to the bottom of the preheater 1 by a closed plate conveyor 205. After discharge, the material falls directly into the discharge pipe 3 for brief preheating. At this time, the 20-65mm particle size material is conveyed to the inside of the feeding platform 201 by an external conveyor belt. After entering the feeding platform 201, the material first passes through the metal screen plate 202. During screening, 40-65mm particles slide along the top of the metal screen plate 202 and accumulate inside the distribution pipe 203, while 20-40mm particles fall directly from inside the metal screen plate 202 and cover the bottom edge of the preheater 1. Subsequently, the 40-65mm particles inside the distribution pipe 203 are discharged and cover the top of the 20-40mm particles. The 40-65mm, 20-40mm, and 10-20mm particles are distributed from top to bottom in sequence, and after preheating, they enter the rotary kiln for calcination.

[0033] The preheater 1 contains a feeding chamber 101, a middle feeding chamber 102, and a feeding chamber 103. 10-20mm particle size materials, conveyed by a closed conveyor 205, are fed directly from the feeding chamber 101 into the feeding pipe 3. 20-40mm particle size materials, screened by the metal sieve 202, accumulate in the middle feeding chamber 102 and below (i.e., the area accumulated in the middle feeding chamber 102 and the feeding chamber 101, not inside the feeding pipe 3), while 40-65mm particle size materials accumulate inside the feeding chamber 103. (See attached diagram for details.) Figure 8 .

[0034] Specifically, sealing plates 207 are fixedly installed between several feed pipes 203 in sequence, and the interior of the preheater 1 is sealed by the sealing plates 207.

[0035] Reference Figure 3 , Figures 5 to 8 In a preferred embodiment, a vent 204 is fixedly installed inside the preheater 1. The vent 204 is distributed inside the intermediate material chamber 102 and the upper material chamber 103. The vent 204 is fixedly installed inside the preheater 1 by several connecting brackets 2041. Several densely distributed vents 2042 are opened through the surface of the vent 204, and the diameter of the vents 2042 increases from bottom to top. The bottom of the preheater 1 is connected through a feed pipe 3, and the vent 204 is distributed at the top of the feed pipe 3.

[0036] The feed pipe 3 is connected to the rotary kiln. The high-temperature gas generated during the operation of the rotary kiln will enter the interior of the preheater 1 through the feed pipe 3 and move vertically upward along the bottom of the vent 204. During this process, the high-temperature gas will escape through the vent 2042, thereby preheating the material piled up inside the feed chamber 101, the middle material chamber 102 and the upper material chamber 103. It can also preheat the 10-20mm particle size material fed from the feed pipe 3. The 20-40mm particle size material falling from the top of the metal screen plate 202 will slide along the surface of the vent 204 and fall into the interior of the feed chamber 101 and the middle material chamber 102.

[0037] Reference Figure 2 , Figures 4 to 8 In a preferred embodiment, an electric pusher plate 206 is slidably inserted into the interior of each distribution tube 203. The electric pusher plate 206 forms a shield for 40-65mm particle size materials located inside the distribution tube 203. An insertion port 2031 is provided through the side wall of the distribution tube 203, and the electric pusher plate 206 is slidably inserted into the interior of the distribution tube 203 through the insertion port 2031.

[0038] Material with a particle size of 20-65mm is conveyed to the inside of the feeding platform 201 via an external conveyor belt. After entering the feeding platform 201, the material will first pass through the metal screen plate 202 for screening. At this time, the material with a particle size of 40-65mm will slide along the top of the metal screen plate 202, be blocked by the electric push plate 206 and accumulate inside the distribution pipe 203. The screened material with a particle size of 20-40mm will fall directly from the inside of the metal screen plate 202 and be located at the bottom edge of the preheater 1. Then, the electric push plate 206 located inside the distribution pipe 203 will start and retract from the inside of the distribution pipe 203 along the inlet 2031. At this time, the material with a particle size of 40-65mm that is no longer blocked will be discharged and cover the top of the material with a particle size of 20-40mm.

[0039] Reference Figure 1 , Figures 5 to 8 In a preferred embodiment, a plurality of evenly distributed hydraulic push rods 4 are installed through the side wall of the preheater 1, and the hydraulic push rods 4 are distributed inside the discharge chamber 101.

[0040] Materials with particle sizes of 40-65mm, 20-40mm, and 10-20mm are distributed sequentially from top to bottom. After a period of preheating, the hydraulic pusher 4 is activated simultaneously. The hydraulic pusher 4 continuously pushes the material at the bottom layer inside the preheater 1, causing the material to be discharged from the inside of the feed pipe 3 and enter the rotary kiln for calcination. Therefore, the large particles at the top layer stay in the preheater 1 for the longest time and are preheated most thoroughly. Conversely, the small particles at the bottom layer will not be overheated, thus increasing production capacity. Furthermore, the advantage of screening the material in advance can also prevent large particles from wrapping around small particles, thereby preventing insufficient preheating of the wrapped small particles.

[0041] In the above technical solution, it is worth noting that the electric push plate 206 operates first, while the hydraulic push rod 4 operates later. This ensures that all materials with a particle size of 40-65mm are released and preheated before the hydraulic push rod 4 performs the next feeding operation. This ensures that the same batch of materials is preheated in different grades and zones before the next batch of materials is preheated according to the process.

[0042] Working principle: During use, the raw materials to be processed are first screened by an external double-layer drum screen. The screening interval is for two particle sizes: 10-20mm and 20-65mm (raw materials of other particle sizes are excluded and do not participate in the processing flow of this application). After screening, the 10-20mm particle size material enters the external storage silo and is conveyed to the bottom of the preheater 1 by the enclosed plate conveyor 205. The 10-20mm particle size material is directly discharged into the feed pipe 3. The specific status is shown in the attached figure. Figure 6 As shown; at this time, the 20-65mm particle size material is conveyed to the inside of the feeding platform 201 by the external conveyor belt. After the material enters the feeding platform 201, it will first pass through the metal screen plate 202 for screening. At this time, the 40-65mm particle size material will slide along the top of the metal screen plate 202, be blocked by the electric push plate 206 and accumulate inside the distribution pipe 203. The screened 20-40mm particle size material will fall directly from the inside of the metal screen plate 202 and be located at the bottom edge of the preheater 1, distributed in the feeding chamber 101 and the middle material chamber 102. The specific state is shown in the attached figure. Figure 7 As shown; then the electric push plate 206 located inside the distribution pipe 203 is activated, retracting from the inside of the distribution pipe 203 along the inlet 2031. At this time, the 40-65mm particle size material, which is no longer obstructed, is discharged and covers the top of the 20-40mm particle size material, distributed in the feeding chamber 103. The specific state is shown in the attached figure. Figure 8As shown; at this time, 40-65mm, 20-40mm, and 10-20mm particle size materials are distributed from top to bottom in sequence. After a period of preheating, the hydraulic pusher rod 4 is started synchronously. The hydraulic pusher rod 4 continuously pushes the bottom layer of material piled inside the preheater 1, causing the smaller particle size material at the bottom to be fed into the feed pipe 3 first and enter the rotary kiln for calcination. During this process, the running speed and frequency of the hydraulic pusher rod 4 can be controlled to control the preheating efficiency of the material. Since the small particle size material is in the lower layer and the large particle size material is in the upper layer, it is more convenient to control the feeding rate of the hydraulic pusher rod 4 to achieve sufficient preheating of the large particle size material in the upper layer, and to avoid overheating of the small particle size material in the lower layer.

[0043] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Furthermore, the particle size values ​​defined in the present invention are not related to the scope of protection of this application. The three particle size values ​​defined in this application can be understood as three different ranges of values: large, medium, and small. Any technical solution that can screen the material particles and arrange them in the preheater 1 in a graded manner from bottom to top for zoned preheating is within the scope of protection of this application. Moreover, any equivalent substitutions or modifications made by those skilled in the art within the technical scope disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A rotary kiln graded and zoned calcination process, comprising a preheater (1), characterized in that, The preheater (1) is equipped with a pretreatment mechanism (2) for graded preheating of materials. The pretreatment mechanism (2) includes a feeding platform (201) mounted on the top of the preheater (1). A metal screen plate (202) is fixedly installed at the bottom of the feeding platform (201). Several evenly distributed distribution pipes (203) are connected through the bottom outer edge of the metal screen plate (202). The distribution pipes (203) are connected through the interior of the preheater (1). A closed plate conveyor (205) is installed through the lower side wall of the preheater (1). Before entering the preheater (1), the raw materials are first screened by a double-layer drum screen, with two particle sizes in the screening interval: 10-20mm and 20-65mm. The 10-20mm particle size material enters the external storage silo and is conveyed to the bottom of the preheater (1) by the closed plate conveyor (205). The 20-65mm particle size material is conveyed to the inside of the feeding platform (201), and after being screened by the metal screen plate (202), the 40-65mm particle size material accumulates inside the distribution pipe (203), and the 20-40mm particle size material falls off from inside the metal screen plate (202) and covers the top of the 10-20mm particle size material. Then, the 40-65mm particle size material located inside the distribution pipe (203) is discharged and covers the top of the 20-40mm particle size material. After preheating, it enters the rotary kiln for calcination.

2. The rotary kiln graded and zoned calcination process according to claim 1, characterized in that, The preheater (1) is provided with a feeding chamber (101), a middle feeding chamber (102) and a feeding chamber (103) in sequence. 10-20 mm particle size material is conveyed by the closed plate conveyor (205) and fed from the feeding chamber (101). 20-40 mm particle size material is screened by the metal sieve plate (202) and accumulates in the middle feeding chamber (102) and below, while 40-65 mm particle size material is accumulated in the feeding chamber (103).

3. The rotary kiln graded and zoned calcination process according to claim 2, characterized in that, The preheater (1) is fixedly installed with a vent hood (204), which is distributed inside the intermediate material chamber (102) and the loading chamber (103).

4. The rotary kiln graded and zoned calcination process according to claim 3, characterized in that, The vent (204) is fixedly installed inside the preheater (1) by a number of connecting brackets (2041).

5. The rotary kiln graded and zoned calcination process according to claim 3, characterized in that, The surface of the vent (204) is provided with a number of densely distributed vents (2042), and the diameter of the vents (2042) increases sequentially from bottom to top.

6. The rotary kiln graded and zoned calcination process according to claim 1, characterized in that, Each of the distributing tubes (203) has an electric push plate (206) slidably inserted inside, which shields the 40-65mm particle size material located inside the distributing tube (203).

7. The rotary kiln graded and zoned calcination process according to claim 6, characterized in that, The side wall of the material distribution tube (203) is provided with a through-hole (2031), and the electric push plate (206) is slidably inserted into the inside of the material distribution tube (203) through the through-hole (2031).

8. The rotary kiln graded and zoned calcination process according to claim 1, characterized in that, A sealing plate (207) is fixedly installed between several of the feed pipes (203), and the interior of the preheater (1) is sealed by the sealing plate (207).

9. The rotary kiln graded and zoned calcination process according to claim 3, characterized in that, The bottom of the preheater (1) is connected to the feed pipe (3), and the vent hood (204) is distributed on the top of the feed pipe (3).

10. The rotary kiln graded and zoned calcination process according to claim 2, characterized in that, The side wall of the preheater (1) is equipped with several evenly distributed hydraulic push rods (4), which are distributed inside the discharge chamber (101).

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