Iron ore coal-based hydrogen metallurgy rotary kiln

Abstract

The utility model discloses an iron ore coal-based hydrogen metallurgy rotary kiln, which is characterized in that three retaining rings are arranged at different positions in a rotary kiln body, a pea coal spray gun arranged on a kiln head cover at the discharge end of the rotary kiln is subjected to eccentric displacement, and a rotary kiln burner is selected as a sleeve type burner, so that on the basis of reducing the fall of materials in the rotary kiln, the coal-based hydrogen metallurgy rotary kiln can be realized. The contact area of materials and the kiln wall is increased, and the rotating speed of the rotary kiln, the material filling rate and the uniformity of the temperature in the kiln are improved. According to the method, the fuel consumption of the rotary kiln is reduced, and the utilization efficiency of hydrogen in iron ore coal-based reduction and the iron ore reduction quality and yield are improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to a rotary kiln technical field, concretely relates to a kind of iron ore coal-based hydrogen metallurgical rotary kiln. BACKGROUND

[0002] In the direct reduction process of iron ore rotary kiln, the mixture of iron ore and reducing coal is added from the charging end of the rotary kiln, and under the rotation of the rotary kiln, the mixture flows from the charging end to the discharging end during the turning process, and exchanges heat with the countercurrent high-temperature flue gas, causing the temperature of the mixture to rise, while the temperature of the flue gas decreases. When the temperature of the mixture rises above 450°C, the iron ore in the material begins to react with the reducing coal, and as the temperature of the mixture rises, the reduction reaction rate of the iron ore increases, and at this time, the amount of metallurgical gas overflowing from the interior of the material increases. After the metallurgical gas overflows from the interior of the material layer, it enters the space inside the kiln, and under the action of the combustion air blown by the kiln backdraft fan, the metallurgical gas burns, and the heat released by the combustion heats the mixture. When the mixture moves to the middle of the kiln body, the temperature of the mixture rises to 900-1100°C, at which time the reduction reaction rate of the iron ore reaches a maximum, and the amount of metallurgical gas released by the reduction reaction also reaches a maximum, and the temperature of the metallurgical gas after combustion is also higher. By adding excess reducing coal to the iron ore, the heat released by the combustion of metallurgical gas can meet the needs of rotary kiln production. Thereafter, as the mixture of ore and coal flows in the kiln and the reduction reaction continues, the content of iron oxide and reducing coal in the material decreases, and the amount of metallurgical gas released by the reduction reaction in the material also gradually decreases. When the mixture reaches the discharge section of the rotary kiln, the space temperature after the combustion of metallurgical gas will decrease. At this time, in order to increase the temperature of the discharge section of the rotary kiln and ensure the reduction effect, a heating burner is arranged at the center of the discharge end of the rotary kiln. As shown in Figure 1 Figure 1 is a schematic diagram of the existing iron ore direct reduction rotary kiln.

[0003] In the heating burners used in rotary kilns, premix burners that stabilize the flame are generally used, and the combustion air pressure is only 6-7KPa. The length of the combustion flame of such a burner is only 5-7m, and the thermal load in the combustion area is high, which can easily cause the kiln body to form rings and the material to be soft-melted due to high temperature at the head of the flame during use in the rotary kiln, thereby affecting the hydrogen reduction efficiency of the rotary kiln. At the same time, the temperature in the area where the flame does not reach at the discharge end of the kiln body is lower, causing uneven temperature in the rotary kiln.

[0004] ​In the patent application "A Coal-Based Hydrogen Metallurgical Process and Apparatus for Iron Ore" (application number 201910518199X), to improve the reduction reaction rate of iron ore, a granular coal spray gun is installed above the heating burner on the kiln head hood at the discharge end, based on the aforementioned rotary kiln structure. The granular coal spray gun can spray granular high-volatile coal into the high-temperature reduction zone of the rotary kiln according to the process requirements. After the high-volatile coal mixes with the high-temperature mixture, its temperature rises rapidly, and the volatiles in the granular coal begin to be released. Under the high temperature inside the material layer, the volatiles further pyrolyze to produce a large amount of H2. H2 acts as a reducing agent to reduce the iron ore. Because the material inside the rotary kiln settles at the bottom of the kiln diagonally above the direction of rotation during rotation, such as... Figure 2 This diagram illustrates the distribution of roasted materials on the cross-section of a rotary kiln for direct reduction of iron ore. The rotary kiln rotates counterclockwise. During the descent of the granular coal ejected from the granular coal nozzle, a portion of it lands on the kiln bottom, uncovered by the mixed materials. Under the high temperature inside the kiln, the volatile matter in this portion of the coal is rapidly released and enters the kiln space, failing to reduce the iron ore and thus reducing H2 utilization. Simultaneously, to increase the kiln filling rate and extend the reduction time of the material, the rotary kiln speed is controlled below 0.4 r / min. This low rotational speed significantly reduces the tumbling speed of the material inside the kiln. The surface of the material in contact with the high-temperature flame is subjected to prolonged heating, making it prone to liquefaction. Once the liquid phase appears, it easily adheres to the surrounding powder, resulting in flaky material on the surface. This flaky material hinders heat transfer to the lower material, thus reducing the rotary kiln's production capacity and product quality.

[0005] Meanwhile, in the rotary kiln's back fan, the air pressure is typically 2-3 kPa. This low air pressure causes the air blown out by the back fan to rapidly disperse at the nozzle and flow for 2-3 meters within the kiln. Its velocity then matches the flow velocity of the flue gas, causing it to flow together with the flue gas. This air mixes with the metallurgical gas overflowing from the material bed and undergoes combustion, resulting in localized high temperatures within 2-3 meters of the back fan nozzle. In this area, the material is prone to producing a liquid phase during roasting, leading to material sticking to the kiln and affecting the normal roasting of iron ore. Furthermore, the reduction of iron ore in the rotary kiln is a strongly endothermic process; the temperature is lower in areas where fuel is not burned, further impacting the normal reduction of iron ore.

[0006] Based on the above reasons, in order to improve the hydrogen reduction efficiency of direct reduction of iron ore in rotary kilns, reduce the fuel consumption of rotary kilns, and achieve the goal of improving the quality and yield of iron ore reduction, this invention proposes a novel iron ore coal-based hydrogen metallurgical rotary kiln. Utility Model Content

[0007] This utility model discloses a rotary kiln for iron ore coal-based hydrogen metallurgy, which solves the problem that the utilization rate of volatile H2 produced by the full pyrolysis of high volatile coal injected into the kiln from the discharge end in the direct reduction process of iron ore rotary kilns is not high.

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

[0009] A rotary kiln for iron ore and coal-based hydrogen metallurgy includes a rotary kiln body. Inside the rotary kiln body, at the discharge end port, at a distance of 1 / 3 of the total length of the rotary kiln, and at a distance of 2 / 3 of the total length of the rotary kiln, a parabolic-shaped baffle ring is installed. The height of the baffle ring is 12%~15% of the inner diameter of the rotary kiln, and the bottom width is 20%~30% of the inner diameter of the rotary kiln. A granular coal spray gun on the kiln head hood at the discharge end of the rotary kiln body is eccentrically positioned, with the eccentric direction approaching the rotary kiln. The center position of the crescent-shaped material surface has an eccentric displacement of 10% to 20% of the inner diameter of the rotary kiln; a sleeve-type kiln head burner is also centrally installed on the kiln head hood at the discharge end of the rotary kiln body. The inner cylinder of the sleeve-type kiln head burner is a gas passage, and the outer cylinder is an air passage. The gas pressure is 1 to 1.5 times the air pressure; 2 to 5 kiln back fan fans are evenly arranged along the length of the kiln body. Each kiln back fan fan supplies 25% to 35% of the total air supply, and the air supply pressure is 6 to 8 kPa.

[0010] The present invention features a baffle ring installed inside a rotary kiln. The height of the baffle ring is 12-15% of the inner diameter of the rotary kiln, and the bottom width is 20-30% of the inner diameter of the rotary kiln. The outer contour of the baffle ring cross-section is similar to a parabola. The baffle ring is cast from high-temperature refractory material and is integrally constructed with the refractory material of the kiln body.

[0011] By setting a baffle ring inside the rotary kiln, this invention controls the material filling rate inside the rotary kiln to 20-25%, which can increase the material layer thickness inside the rotary kiln by 40-50%. The thicker material layer can maintain a higher reducing atmosphere inside the high-temperature material. At the same time, the reducing gas generated by the bottom material during the reduction process needs to pass through the thicker material layer as it flows from bottom to top, which increases the contact area between the reducing gas and the iron ore, thereby improving the H2 utilization efficiency in the iron ore reduction process.

[0012] With the improved rotary kiln filling rate, the amount of reducing gas overflowing from the inside of the material layer to the surface of the material increases. The increased amount of reducing gas on the surface of the material isolates the oxidizing atmosphere inside the kiln from the reducing material, reducing the secondary oxidation of the reducing material in the rotary kiln and improving the reduction quality of iron ore.

[0013] This invention involves eccentrically displacing the granular coal spray gun installed on the kiln head hood at the discharge end of a rotary kiln from its central position. The displacement direction is closer to the center of the crescent-shaped material surface, and the movement position is 10-20% of the rotary kiln diameter. By moving the granular coal spray gun towards the material surface, most of the granular coal sprayed by the spray gun can fall onto the material surface at the bottom of the rotary kiln, and through the rotation of the rotary kiln, more granular coal is turned into the material layer.

[0014] By installing a baffle ring inside the rotary kiln, this invention can increase the rotational speed of the rotary kiln to 0.6-0.8 r / min. With the increased rotational speed, the material flow rate inside the kiln accelerates, allowing the granular coal injected into the bottom material surface of the rotary kiln by the granular coal spray gun to tumble into the material layer in a shorter time. This reduces the residence time of the granular coal in the high-temperature space inside the kiln, reduces the release of volatiles from the granular coal on the surface of the material layer, and allows more volatiles from the granular coal to enter the interior of the material, thereby improving the hydrogen utilization rate in the iron ore reduction process.

[0015] This invention aims to improve the temperature uniformity of iron ore in the reduction section of a rotary kiln and increase H2 reduction efficiency. It replaces the original premixed burner in the rotary kiln with a sleeve-type kiln head burner. The sleeve-type burner injects fuel and air separately from their respective channels. The pressure of the combustion air is 16-20 kPa. The fuel and air undergo diffuse combustion while flowing and mixing / preheating within the rotary kiln space. This increases the flame length of the burner to 15-20 meters. The longer flame length reduces the heat load in the burner's combustion zone, resulting in a more uniform temperature in the high-temperature zone of the rotary kiln.

[0016] This invention aims to reduce the high-temperature heat load in the blowing area of ​​the rotary kiln back fan by increasing the air pressure blown into the kiln by 6-8 kPa. The higher air pressure allows the air jet to act within a range of 6-7 m inside the kiln, thereby greatly extending the blowing area of ​​the kiln back fan. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of an existing rotary kiln for direct reduction of iron ore.

[0018] Figure 2 This is a schematic diagram showing the distribution of roasted materials on the cross-section of an existing rotary kiln for direct reduction of iron ore.

[0019] Figure 3 This is a schematic diagram of the rotary kiln for direct reduction of iron ore described in this utility model.

[0020] Figure 4 This is a schematic diagram of the distribution of roasted materials on the cross-section of the rotary kiln for direct reduction of iron ore described in this utility model.

[0021] In the diagram, 1-rotary kiln body, 2-baffle ring, 3-coal pulverizer, 4-kiln head burner, 5-kiln back fan. Detailed Implementation

[0022] The present invention will be further explained below with reference to the accompanying drawings.

[0023] like Figures 3-4 As shown, the rotary kiln of this utility model includes a rotary kiln body 1. Inside the rotary kiln body 1, at the discharge end port, at a distance of 1 / 3 of the total length of the rotary kiln, and at a distance of 2 / 3 of the total length of the rotary kiln, a parabolic-shaped baffle ring 2 is provided. The height of the baffle ring 2 is 15% of the inner diameter of the rotary kiln, and the bottom width is 25% of the inner diameter of the rotary kiln. The granular coal spray gun 3 on the kiln head hood at the discharge end of the rotary kiln body 1 is eccentrically positioned, with the eccentric direction being closer to the rotary kiln. The center position of the crescent-shaped material surface is eccentrically displaced by 15% of the inner diameter of the rotary kiln; a sleeve-type kiln head burner 4 is also centrally installed on the kiln head cover at the discharge end of the rotary kiln body 1. The inner cylinder of the sleeve-type kiln head burner 4 is a gas passage, and the outer cylinder is an air passage, and the gas pressure is 1.5 times the air pressure; four kiln back fan 5 are evenly arranged along the length of the kiln body 1, and the air supply volume of each kiln back fan is 25~35% of the total air supply volume, and the air supply pressure is 6~8KPa.

[0024] The specific work process is as follows:

[0025] 1) Mix the iron ore and residual carbon in a weight ratio of 100:25~100:35 until they are evenly mixed, and then add them into the rotary kiln from the feed end.

[0026] 2) The material filling rate in the rotary kiln is 20~25%, and the rotation speed of the rotary kiln is 0.6~0.8 r / min. Under the rotation of the rotary kiln, the mixture continuously flows from the feed end to the discharge end during the tumbling and flow process, and exchanges heat with the high-temperature flue gas flowing in the opposite direction in the kiln, so that the temperature of the mixture continuously rises.

[0027] 3) When the temperature of the mixture rises to 600℃, the iron ore begins to undergo a reduction reaction under the action of carbon in the residual carbon. As the temperature of the mixture rises, the reduction reaction rate of the iron ore accelerates. The metallurgical gas overflowing from the mixture is burned by the air blown in by the kiln back fan and heats the rotary kiln. By controlling the reduction temperature of the iron ore to 900~1100℃ and the reduction time to 90~180min, the iron ore can be fully reduced.

[0028] 4) After the high-temperature reduced material obtained from the iron ore reduction is discharged from the rotary kiln, it is cooled in an oxygen-free environment. After being cooled to room temperature, the reduced material enters the magnetic separator to separate the reduced material into metallized material and residual carbon. The residual carbon is returned to the batching system of the iron ore rotary kiln for utilization, while the metallized material is used as a product.

[0029] 5) The 600-700℃ high-temperature flue gas discharged from the feed end of the iron ore rotary kiln enters the waste heat boiler. Through indirect heat exchange with water, the temperature of the flue gas can be reduced to 150-180℃ while producing high-temperature and high-pressure steam. After cooling, the flue gas is then removed by a cyclone dust collector and a bag dust collector, and finally discharged after being pressurized by a smoke extractor.

[0030] All other aspects not described herein are the same as those in existing iron ore and coal-based hydrogen metallurgical rotary kilns, and will not be elaborated upon here.

Claims

1. A rotary kiln for iron ore and coal-based hydrogen metallurgy, characterized in that, The rotary kiln body (1) includes a parabolic baffle ring (2) located at the discharge end port, 1 / 3 of the total length of the rotary kiln, and 2 / 3 of the total length of the rotary kiln. The height of the baffle ring (2) is 12% to 15% of the inner diameter of the rotary kiln, and the bottom width is 20% to 30% of the inner diameter of the rotary kiln. The granular coal spray gun (3) on the kiln head cover at the discharge end of the rotary kiln body (1) is eccentrically positioned, with the eccentric direction being... To be close to the center of the crescent-shaped material surface formed by the rotation inside the rotary kiln, the eccentric displacement is 10%~20% of the inner diameter of the rotary kiln; a sleeve-type kiln head burner (4) is also centrally installed on the kiln head cover at the discharge end of the rotary kiln body (1). The inner cylinder of the sleeve-type kiln head burner (4) is a gas pipe, and the outer cylinder is an air pipe. The pressure of the gas pipe is 1~1.5 times that of the air pipe; 2-5 kiln back fan (5) are also evenly installed on the rotary kiln body (1) along the length of the kiln body.

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