A bricklaying structure for increasing the length of the flame in a rotary kiln for iron ore pellets

Abstract

The application relates to a bricklaying structure for increasing the flame length in an iron ore pellet rotary kiln, wherein an annular boss is laid in the rotary kiln, and the cross section of the annular boss is trapezoidal. The bricklaying structure for increasing the flame length in the iron ore pellet rotary kiln can increase the flame length by reducing the cross section of the front section in the rotary kiln along the running direction of the gas, restoring the rear end, accelerating the instantaneous flow speed of the high-temperature gas and increasing the flame length based on the Venturi principle, and further improving the production quality of the iron ore pellets in the rotary kiln under the normal production conditions such as normal running and filling rate of the pellets in the rotary kiln.

Description

Technical Field

[0001] This invention belongs to the field of ironmaking technology, and specifically relates to a masonry structure for increasing the flame length in a rotary kiln for iron ore pelletizing. Background Technology

[0002] In the rotary kiln pellet production process of ironmaking, the main heat source is the combustion of combustible materials injected into the burner with air, providing heat energy. This heat is then continuously supplied to the pellets during roasting within the rotary kiln through radiation and convection heat exchange. The combustible materials used are categorized as solid (e.g., pulverized coal, biomass powder), gaseous (e.g., coke oven gas, natural gas), and liquid (e.g., heavy oil). Solid particles are transported via a two-way gas-solid flow, with both gaseous and liquid states transported under pressure. Due to the inherent properties of the materials, the combustion process of gaseous combustible materials such as coal gas in the rotary kiln presents disadvantages such as a shorter flame length and greater heat dissipation after combustion.

[0003] Application publication number CN114622051A discloses a method and apparatus for the direct reduction of iron-containing pellets based on the internal circulation of hot air in each section of a rotary kiln. This invention aims to achieve low-temperature rapid reduction in a coal-based rotary kiln by dividing the kiln into a drying section, a preheating section, a reduction roasting section, and a slow cooling stage. Based on the analysis of the state changes of materials and hot air in each section of the rotary kiln, the hot air containing water vapor, CO, CO2, and waste heat generated in each section is rationally redistributed within each section. This fully utilizes the potential for preheating and waste energy utilization, reducing the reaction temperature required for the reduction reaction. In other words, through a specially designed internal air circulation mechanism in each section of the rotary kiln, the invention achieves energy saving, emission reduction, and improved low-temperature rapid reduction of iron-containing pellets.

[0004] Application publication number CN115597366A proposes a method for maintaining uniform heat distribution in a rotary kiln. The air inlet pipe is spirally inserted into the interior of the rotary kiln, and outward nozzles are set at different intervals on the outer wall of the feed pipe. The nozzles are at different angles to the pipe. Multiple nozzles and supports with bearings are set along the length of the rotary kiln. The spiral pipe can also adjust the position of the burner by telescoping, so that there are no dead zones in heat transfer inside the kiln. This ensures that the heat obtained per unit length of the kiln is the same, and high-pressure gas injection is not required. Ultimately, uniform heat distribution inside the rotary kiln is achieved, while keeping the burner at the center of the rotary kiln axis.

[0005] Application publication number CN115540615A discloses an energy-saving, emission-reducing, production-increasing, and efficiency-enhancing precision oxygen-enriching combustion system for rotary kilns. The system features an installation hole on the rotary kiln head hood, through which an oxygen-enriching nozzle passes. Four lifting rings are evenly distributed around the nozzle body outside the hole. Two symmetrical lifting rings are adjustment rings used to adjust the angle of the oxygen-enriching nozzle, while the other two are fixing rings used to secure the nozzle. The nozzle body can rotate along its central axis via a flexible hose connector, adjustment rings, and a hook connector. When the oxygen-enriching nozzle bends due to high temperature or its own weight, adjustments can be made without stopping the oxygen-enriching equipment, ensuring precise oxygen delivery to the required parts of the product. This eliminates the need for frequent equipment shutdowns to replace the nozzle, significantly extending its service life and making the invention more practical. The overall effects of energy saving, emission reduction, production increase, and efficiency improvement are also enhanced.

[0006] In existing technologies, the flame length adjustment methods in rotary kilns for iron ore pelletizing mostly involve adjusting the burner fuel flow rate and the multiple air distribution volume. However, these methods have design limitations, and there is currently no effective way to significantly increase the flame length. Therefore, this invention proposes a refractory material lining structure to improve the flame length in rotary kilns for iron ore pelletizing. By optimizing the refractory material lining method in the rotary kiln, the cross-sectional area of ​​the front section of the kiln is reduced while the rear section is restored. The flame length is increased by utilizing the Venturi principle to accelerate the instantaneous flow rate of high-temperature combustion gas, thereby improving the quality of iron ore pellets produced by the rotary kiln. Summary of the Invention

[0007] The purpose of this invention is to provide a masonry structure for increasing the flame length in a rotary kiln for iron ore pelletizing. This structure satisfies normal production conditions, such as normal pellet movement and filling rate within the rotary kiln. By altering the physical structure through a reduction in the cross-sectional area of ​​the front and rear sections of the kiln along the gas flow direction and restoring it at the rear, the Venturi principle is used to accelerate the instantaneous flow velocity of the high-temperature gas, thereby increasing the flame length and ultimately improving the quality of iron ore pellets produced in the rotary kiln.

[0008] To achieve the above objectives, the present invention employs the following technical solution:

[0009] A masonry structure for increasing the flame length inside a rotary kiln for iron ore pelletizing includes an annular boss inside the kiln, the annular boss having a trapezoidal cross-section.

[0010] A trapezoidal boss satisfies the following formula:

[0011] s1 / s2 = 0.43~1.5;

[0012]

[0013] β = 30°~45°;

[0014] h = 0.01R ~ 0.035R;

[0015] a = 0.38 h·L / R ~ 0.5 h·L / R;

[0016] Where: s1—distance from the center of the bottom edge of the trapezoidal boss to the kiln head / mm; s2—distance from the center of the bottom edge of the trapezoidal boss to the kiln tail / mm; α—angle formed by the slope of the trapezoidal boss near the kiln tail and the rotary kiln / °; R—radial diameter of the rotary kiln / mm; L—length of the rotary kiln / mm; β—angle formed by the slope of the trapezoidal boss near the kiln head and the rotary kiln / °; h—height of the trapezoidal boss; a—length of the bottom edge of the trapezoidal boss.

[0017] The angle between the rotary kiln and the horizontal along the gas flow direction is θ > α.

[0018] The interior of the rotary kiln is constructed of refractory material. Except for the trapezoidal protrusions, the rest of the interior is flat and has a uniform thickness.

[0019] h' / h 耐 ≮0.2; where: h'—real-time height of the trapezoidal boss during production / mm; h 耐 —Refractory thickness in flat areas within the rotary kiln during production / mm. When h' / h 耐 When the value is less than 0.2, production should be stopped.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] This invention optimizes the refractory lining method of rotary kilns and, based on the Venturi principle, accelerates the instantaneous flow rate of high-temperature gas, increasing the flame length by more than 8%, thereby increasing the compressive strength of the finished pellets by more than 5%. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the axial cross-section of the rotary kiln of the present invention.

[0023] Figure 2 This is a schematic diagram of the radial section of the present invention.

[0024] In the diagram: 1-protrusion, 2-flat area, 3-kiln head, 4-kiln tail, 5-pellet. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the specific implementation methods of this invention will be further described below in conjunction with the embodiments. The following embodiments are used to specifically illustrate the content of this invention. These embodiments are only general descriptions of the content of this invention and do not limit the content of this invention.

[0026] like Figure 1 , Figure 2As shown, the present invention provides a masonry structure for increasing the flame length inside a rotary kiln for iron ore pelletizing. The axial cross-section of the rotary kiln has a generally flat interior, and an annular boss 1 is built in the middle area of ​​the rotary kiln. The cross-section of the annular boss 1 is trapezoidal.

[0027] Trapezoidal boss 1 satisfies the following formula:

[0028] s1 / s2 = 0.43~1.5;

[0029]

[0030] β = 30°~45°;

[0031] h = 0.01R ~ 0.035R;

[0032] a = 0.38 h·L / R ~ 0.5 h·L / R;

[0033] Where: s1—distance from the center of the bottom edge of the trapezoidal boss to the kiln head / mm; s2—distance from the center of the bottom edge of the trapezoidal boss to the kiln tail / mm; α—angle formed by the slope of the trapezoidal boss near the kiln tail and the rotary kiln / °; R—radial diameter of the rotary kiln / mm; L—length of the rotary kiln / mm; β—angle formed by the slope of the trapezoidal boss near the kiln head and the rotary kiln / °; h—height of the trapezoidal boss; a—length of the bottom edge of the trapezoidal boss.

[0034] The angle between the rotary kiln and the horizontal along the gas flow direction is θ > α.

[0035] h' / h 耐 ≮0.2; where: h'—real-time height of the trapezoidal boss during production / mm; h 耐 —Refractory thickness in the flat area of ​​the rotary kiln during production (2 mm). When h' / h 耐 When the value is less than 0.2, production should be stopped.

[0036] Table 1 shows the relevant parameters of the trapezoidal masonry section in this embodiment of the invention. The angle θ between the rotary kiln and the horizontal along the gas flow direction and the h' / h in this embodiment are also shown. 耐 The values ​​are shown in Table 2, and the flame length of the embodiment is shown in Table 3.

[0037] Table 1. Parameters related to the trapezoidal boss in the embodiment.

[0038]

[0039] Table 2. Relevant parameters of the rotary kiln in the embodiment.

[0040] α / ° θ / ° h' / mm <![CDATA[h 耐 / mm]]> h' / h endurance Example 1 7 8 80 280 0.285714286 Example 2 6 7 150 280 0.535714286 Example 3 6 7 190 280 0.678571429 Example 4 5 7 190 280 0.678571429 Example 5 5 6 210 280 0.75

[0041] Table 3. Relevant parameters after implementation of the embodiments.

[0042]

[0043] Note: The method of adjusting burner parameters in the table refers to traditional methods of adjusting flame length, such as increasing the intensity of secondary air.

[0044] As shown in Table 3, the flame length increase ratio after adjustment in the embodiments of the present invention (8.17-25.96%) is much higher than that of the traditional burner parameter adjustment method (6.25%), and the pressure resistance increase ratio of the finished ball (5.64-9.98%) is better than that of the traditional burner parameter adjustment method (4.77%).

Claims

1. A masonry structure for increasing the flame length inside a rotary kiln for iron ore pelletizing, characterized in that, An annular protrusion is constructed inside the rotary kiln, and the cross-section of the annular protrusion along the direction of flame travel is trapezoidal. The trapezoidal boss satisfies the following formula: s1 / s2 = 0.43~1.5; ； β=30°～45°； h = 0.01R ~ 0.035R; a = 0.38 h·L / R ~ 0.5 h·L / R; Where: s1—distance from the center of the lower bottom edge of the trapezoidal boss to the kiln head / mm; s2—distance from the center of the lower bottom edge of the trapezoidal boss to the kiln tail / mm; α—angle formed by the slope of the trapezoidal boss near the kiln tail and the rotary kiln / °; R—radial diameter of the rotary kiln / mm; L—length of the rotary kiln / mm; β—angle formed by the slope of the trapezoidal boss near the kiln head and the rotary kiln / °; h—height of the trapezoidal boss / mm; a—length of the upper bottom edge of the trapezoidal boss / mm. The angle θ between the rotary kiln and the horizontal along the gas flow direction is greater than α. h' / h 耐 ≮0.2; where: h'—real-time height of the trapezoidal boss during production / mm; h 耐 —Thickness of refractory material in flat areas inside the rotary kiln during production / mm.

2. The masonry structure for increasing the flame length inside a rotary kiln for iron ore pelletizing according to claim 1, characterized in that, The interior of the rotary kiln is constructed with refractory lining, and except for the trapezoidal protrusions, the overall thickness of the remaining parts is uniform.

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