Method for improving reduction efficiency of iron ore coal-based hydrogen metallurgy rotary kiln

Abstract

The invention discloses a method for improving the reduction efficiency of an iron ore coal-based hydrogen metallurgy rotary kiln, which comprises the following steps of: arranging three retaining rings at different positions in a rotary kiln body, eccentrically displacing a pea coal spray gun arranged on a kiln head cover at the discharge end of the rotary kiln, and selecting a rotary kiln burner as a sleeve type burner, so as to improve the reduction efficiency of the iron ore coal-based hydrogen metallurgy rotary kiln. On the basis of reducing the fall of the materials in the rotary kiln, the contact area of the materials and the kiln wall is increased, and the rotating speed, the material filling rate and the temperature uniformity in the rotary 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 invention belongs to the technical field of metallurgy, and in particular relates to a method for improving the reduction efficiency of a rotary kiln in iron ore coal-based hydrogen metallurgy. Background Art

[0002] In the direct reduction process of the iron ore rotary kiln, after the mixture of iron ore and reducing coal is added from the feed end of the rotary kiln, under the rotation of the rotary kiln, the mixture continuously flows from the feed end to the discharge end during the turning process, and exchanges heat with the high-temperature flue gas coming in the opposite direction, so that the temperature of the mixture increases and the flue gas temperature decreases. When the temperature of the mixture rises to above 450°C, the iron ore and reducing coal in the material begin to undergo a reduction reaction, and as the temperature of the mixture increases, the reduction reaction rate of the iron ore accelerates, and at this time, more metallurgical gas overflows from the material. After the metallurgical gas overflows from the material layer, it enters the space inside the kiln, and the metallurgical gas burns under the action of the combustion-supporting air blown in by the kiln back fan, and the heat released by the combustion heats the mixture. When the mixed material moves to the middle and rear section of the kiln body in the rotary kiln, the temperature of the mixed material rises to 900-1100℃. At this time, the reduction reaction rate of the iron ore reaches the maximum, and the amount of metallurgical gas released by the reduction reaction also reaches the maximum. The temperature of the metallurgical gas after combustion is also higher. By adding an excess of reducing coal to the iron ore, the heat released by the combustion of the metallurgical gas can meet the production needs of the rotary kiln. Thereafter, as the ore-coal mixture flows in the kiln and the reduction reaction continues, the iron oxide content and the reducing coal content in the material continue to decrease, and the amount of metallurgical gas released by the reduction reaction inside the material also gradually decreases. When the mixed material reaches the discharge section of the rotary kiln, the temperature of the space after the metallurgical gas is burned 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 set at the center of the discharge end of the rotary kiln. Specifically, Figure 1 As shown, Figure 1 Schematic diagram of the existing iron ore direct reduction rotary kiln.

[0003] The heating burners used in rotary kilns generally use premixed burners with stable flames. The combustion air pressure is only 6-7KPa. The combustion flame length of this burner is only 5-7m, and the heat load in the combustion area is relatively high. During the use of the rotary kiln, it is easy to cause the flame head to form rings in the kiln body and soften the material due to the high temperature, thereby affecting the hydrogen reduction efficiency of the rotary kiln. At the same time, the temperature of the area where the flame does not reach the discharge end of the kiln body is relatively low, resulting in uneven temperature in the rotary kiln.

[0004] In the patent document "An Iron Ore Coal-based Hydrogen Metallurgical Process and Device Thereof" application number 201910518199X, in order to increase the reduction reaction rate of iron ore, on the basis of the above-mentioned rotary kiln structure, a granular coal spray gun is arranged just above the heating burner on the kiln head cover at the discharge end. The granular coal spray gun can spray granular high-volatile coal into the high-temperature reduction area of ​​the rotary kiln according to the process requirements. After the high-volatile coal is mixed with the high-temperature mixed material, its temperature rises rapidly, the volatile matter in the granular coal begins to be released, and the volatile matter is further pyrolyzed under the high temperature inside the material layer to produce a large amount of H 2 , H 2 As a reducing agent, it can reduce iron ore. As the materials in the rotary kiln rotate, they are deposited at the top of the rotary kiln bottom. Figure 2 The diagram is a schematic diagram of the distribution of roasted materials on the cross section of the existing direct reduction rotary kiln of iron ore. The rotary kiln in the figure rotates counterclockwise. When the granular coal sprayed by the granular coal spray gun falls, some of the granular coal falls on the bottom of the kiln body that is not covered by the mixed material. Under the action of the high temperature in the kiln, the volatile matter in the granular coal is quickly released and enters the space in the kiln, which has no effect on the reduction of iron ore, thereby reducing H 2 At the same time, in order to improve the filling rate of the rotary kiln and extend the reduction time of the material in the rotary kiln, the rotary kiln speed is controlled below 0.4r / min. The low rotation speed of the rotary kiln greatly reduces the turning speed of the material in the kiln. The surface of the material in contact with the high-temperature flame in the kiln is heated for a long time, and the surface of the material is prone to liquefaction. After the liquid phase appears in the material, the liquid phase is easy to adhere to the surrounding powder, so that flaky materials appear on the surface of the material. After the flaky materials appear, they hinder the transfer of heat to the lower materials, thereby reducing the production capacity and product quality of the rotary kiln.

[0005] At the same time, in the kiln back fan set in the rotary kiln, the wind pressure of the kiln back fan is generally 2-3KPa. The low air pressure causes the air blown out by the kiln back fan to quickly disperse at the outlet and flow in the kiln for 2-3m. After its wind speed is the same as the flue gas flow speed in the kiln, it flows together with the flue gas. The air in the kiln is mixed with the metallurgical gas overflowing from the inner layer of the material and then burns, causing local high temperature within 2-3m behind the kiln back fan outlet. The material is prone to produce liquid phase during the roasting process in this area, resulting in the phenomenon of material sticking to the kiln, affecting the normal roasting of iron ore. At the same time, the reduction process of iron ore in the rotary kiln is a strong endothermic process. The temperature is low in the area where the fuel is not burned in the kiln, which affects the normal reduction of iron ore.

[0006] Based on the above reasons, the present invention has invented a method for improving the reduction efficiency of iron ore coal-based hydrogen metallurgical rotary kiln in order to improve the hydrogen reduction efficiency of iron ore direct reduction in rotary kiln, reduce the fuel consumption of rotary kiln, and achieve the purpose of improving the quality and output of iron ore reduction. Summary of the invention

[0007] The present invention aims at the volatile H produced by fully pyrolyzing the high-volatile coal sprayed into the kiln from the discharge end during the direct reduction process of the iron ore rotary kiln. 2 In view of the current situation that the utilization rate of iron ore direct reduction is not high, a method for improving the reduction efficiency of iron ore coal-based hydrogen metallurgical rotary kiln is proposed.

[0008] To achieve the above object, the present invention adopts the following technical solution: A method for improving the reduction efficiency of an iron ore coal-based hydrogen metallurgical rotary kiln comprises the following steps: 1) A rotary kiln is obtained, wherein the rotary kiln comprises a rotary kiln body, wherein a material retaining ring having a parabola-like cross-section is respectively arranged at a discharge end port inside the rotary kiln body, at a position 1 / 3 of the total length of the rotary kiln away from the discharge end port, and at a position 2 / 3 of the total length of the rotary kiln away from the discharge end port, wherein the height of the material retaining 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 granular coal spray gun on the kiln head cover at the discharge end of the rotary kiln body is eccentrically arranged, and the eccentric direction is close to the inner moon of the rotary kiln. The eccentric displacement of the center position of the tooth-shaped material surface is 10-20% of the inner diameter of the rotary kiln; a sleeve-type kiln head burner is centrally arranged on the kiln head cover at the discharge end of the rotary kiln body. The inner tube of the sleeve-type kiln head burner is a gas channel, and the outer tube is an air channel, and the gas pressure is 1-1.5 times the air pressure; 2-5 kiln back draft fans are evenly arranged on the rotary kiln body along the length direction of the kiln body, and the air supply of each kiln back draft fan is 25-35% of the total air supply, and the air supply pressure is 6-8KPa; 2) Mix the iron ore and the residual carbon in a weight ratio of 100:25-100:35 and add them into the rotary kiln from the feeding end of the rotary kiln; 3) The filling rate of the material in the rotary kiln is 20-25%, and the rotation speed of the rotary kiln is 0.6-0.8r / min; under the rotation of the rotary kiln, the mixed material continuously flows from the feeding end to the discharging end during the turning and flowing process, and exchanges heat with the high-temperature flue gas coming from the kiln in reverse, so that the temperature of the mixed material continues to rise; 4) When the temperature of the mixture rises to 600℃, the iron ore begins to undergo reduction reaction under the action of carbon in the residual carbon, and as the temperature of the mixture rises, the reduction reaction rate of the iron ore accelerates, and the metallurgical gas overflowing from the mixture burns under the action of the air blown by the kiln back fan, and supplies heat to the rotary kiln; by controlling the reduction temperature of the iron ore at 900-1100℃ and the reduction time at 90-180min, the iron ore can be fully reduced.

[0009] The height of the retaining ring arranged in the rotary kiln of the present invention 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 shape of the cross section of the retaining ring is similar to a parabola. The retaining ring is cast with high-temperature refractory material and constructed integrally with the refractory material of the kiln body.

[0010] After the material retaining ring is arranged in the rotary kiln, the filling rate of the material in the rotary kiln is controlled to be 20-25%, so that the thickness of the material layer in the rotary kiln can be increased by 40-50%. The thicker material layer thickness can keep a higher reducing atmosphere inside the high-temperature material. At the same time, the reducing gas generated by the bottom material in the reduction process needs to pass through the thicker material layer when flowing from bottom to top, thereby increasing the contact area between the reducing gas and the iron ore, and improving the H in the iron ore reduction process. 2 Utilization efficiency.

[0011] After the filling rate of the rotary kiln of the present invention is improved, the amount of reducing gas overflowing from the inside of the material layer to the surface of the material is increased, and the larger amount of reducing gas on the surface of the material isolates the contact between the oxidizing atmosphere in the kiln space and the reducing material, reduces the secondary oxidation of the reducing material in the rotary kiln, and improves the reduction quality of the iron ore.

[0012] The present invention displaces the granular coal spray gun arranged on the kiln head cover at the discharge end of the rotary kiln eccentrically from the central position, the displacement direction is close to the central position of the crescent-shaped material surface, and the displacement position is 10-20% of the kiln diameter of the rotary kiln. By moving the granular coal spray gun toward the material surface, most of the granular coal sprayed by the granular coal spray gun can fall on the material surface at the lower part of the rotary kiln, and more granular coal can be turned into the material layer through the rotation of the rotary kiln.

[0013] After the material retaining ring is arranged in the rotary kiln, the rotation speed of the rotary kiln can be increased to 0.6-0.8r / min. After the rotation speed of the rotary kiln is increased, the flow speed of the material in the kiln is accelerated, and the granular coal sprayed onto the material surface at the bottom of the rotary kiln by the granular coal spray gun can roll into the material layer in a shorter time, thereby reducing the residence time of the granular coal in the high-temperature space in the kiln, reducing the release amount of volatiles in the granular coal on the surface of the material layer, and allowing more volatiles in the granular coal to enter the material, thereby improving the hydrogen utilization rate in the iron ore reduction process.

[0014] In order to improve the temperature uniformity of iron ore in the reduction section of the rotary kiln, increase the H 2 To improve the efficiency, the original premix burner of the rotary kiln is replaced with a sleeve-type kiln head burner. The sleeve-type kiln head burner sprays fuel and air from their respective channels. The pressure of the combustion air is 16-20KPa. The fuel and air flow and mix and preheat in the rotary kiln space for diffuse combustion, which can increase the flame length of the burner to 15-20m. The longer flame length reduces the heat load of the burner combustion area and makes the temperature of the high-temperature area in the rotary kiln more uniform.

[0015] In order to reduce the high temperature heat load in the blowing area of ​​the kiln back draft fan of the rotary kiln, the present invention increases the air pressure blown into the kiln by the kiln back draft fan to 6-8KPa. The higher air pressure can make the air jet act within the range of 6-7m in the kiln, thereby greatly extending the blowing area of ​​the kiln back draft fan.

[0016] In summary, the present invention has the following beneficial effects: (1) Three material retaining rings are set at different positions inside the rotary kiln body. The blocking effect of the material retaining rings can slow down the material flow rate when the material moves from the feeding end to the discharging end, thereby improving the filling rate of the rotary kiln, increasing the contact area between the material and the kiln wall, and improving the H efficiency of the iron ore. 2 Restore effect.

[0017] (2) By increasing the rotation speed of the rotary kiln, the high-volatile coal that falls onto the material surface in the rotary kiln can be turned into the material layer as quickly as possible, thereby increasing the volatile content of the high-volatile coal released by thermal release inside the material layer and improving the hydrogen reduction rate of the iron ore.

[0018] (3) The present invention eccentrically displaces the granular coal spray gun disposed on the kiln head cover at the discharge end of the rotary kiln from the central position, so that most of the granular coal sprayed by the granular coal spray gun falls onto the material surface at the bottom of the rotary kiln, and through the rapid rotation of the rotary kiln, the granular coal is turned into the inner layer of the material in time.

[0019] (4) The present invention replaces the original premix burner of the rotary kiln with a sleeve-type kiln head burner. The fuel and air are diffusely burned in the rotary kiln space, which can increase the flame length of the burner combustion to 15-20m. The longer flame length reduces the heat load of the burner combustion area, making the temperature of the high-temperature zone in the rotary kiln more uniform, thereby improving the hydrogen reduction effect of iron ore. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the existing iron ore direct reduction rotary kiln.

[0021] Figure 2 This is a schematic diagram of the distribution of roasting materials on the cross section of an existing iron ore direct reduction rotary kiln.

[0022] Figure 3 It is a schematic diagram of the iron ore direct reduction rotary kiln according to the present invention.

[0023] Figure 4 This is a schematic diagram of the distribution of roasted materials on the cross section of the iron ore direct reduction rotary kiln of the present invention.

[0024] In the figure, 1-rotary kiln body, 2-material retaining ring, 3-granular coal spray gun, 4-kiln head burner, 5-kiln back fan. DETAILED DESCRIPTION

[0025] The reduction effect of the present invention is further explained below in conjunction with specific embodiments.

[0026] The main chemical components of the iron ore used in this embodiment and comparative example are shown in Table 1: Table 1 Main chemical components of iron ore Example

[0027] like Figure 3-4 As shown, the rotary kiln of the present invention comprises a rotary kiln body 1, wherein a parabola-shaped retaining ring 2 is arranged at a discharge end port inside the rotary kiln body 1, at a position 1 / 3 of the total length of the rotary kiln away from the discharge end port, and at a position 2 / 3 of the total length of the rotary kiln away from the discharge end port, respectively; the height of the retaining 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 cover at the discharge end of the rotary kiln body 1 is eccentrically arranged, and the eccentric direction is close to the inner moon of the rotary kiln. The eccentric displacement of the center position of the tooth-shaped material surface is 15% of the inner diameter of the rotary kiln; a sleeve-type kiln head burner 4 is centrally arranged on the kiln head cover at the discharge end of the rotary kiln body 1, the inner tube of the sleeve-type kiln head burner 4 is a gas channel, the outer tube is an air channel, and the gas pressure is 1.5 times the air pressure; 4 kiln back draft fans 5 are evenly arranged on the rotary kiln body 1 along the length direction of the kiln body, and the air supply of each kiln back draft fan is 25-35% of the total air supply, and the air supply pressure is 6-8KPa.

[0028] 1) Mix the iron ore and the residual carbon in a weight ratio of 100:32 and add them into the rotary kiln from the feeding end of the rotary kiln; 2) The rotary kiln rotates at 0.8r / min, and the filling rate of the mixed material in the kiln is 25%. Under the rotation of the rotary kiln, the mixed material continuously flows from the feeding end to the discharging end during the turning and flowing process, and exchanges heat with the high-temperature flue gas coming from the kiln in reverse, so that the temperature of the mixed material continues to rise; 3) When the temperature of the mixture rises to 600℃, the iron ore begins to undergo reduction reaction under the action of carbon in the residual carbon, and as the temperature of the mixture rises, the reduction reaction rate of the iron ore accelerates, and the metallurgical gas overflowing from the mixture burns under the action of the air blown in by the kiln back fan, and supplies heat to the rotary kiln; by controlling the reduction temperature of the iron ore to 1050℃ and the reduction time to 160min, the iron ore can be fully reduced.

[0029] The metallized material discharged from the discharging end of the rotary kiln was taken for component analysis. The total iron TFe content, metallic iron content MFe and metallization rate are shown in Table 2.

[0030] Table 2 Main components of metallized materials produced by the rotary kiln of the present invention Comparative Example like Figure 1-2 As shown, a rotary kiln disclosed in the prior art is used, no retaining ring is arranged inside the rotary kiln, the granular coal spray gun is not eccentrically arranged, a premixed kiln head burner is adopted, the air and gas pressure ratio is 1:1, the air pressure is 6-7KPa, 4 kiln back fans are arranged, and the wind pressure of each kiln back fan is generally 2-3KPa.

[0031] 1) Mix the iron ore and the residual carbon in a weight ratio of 100:32 and add them into the rotary kiln from the feeding end of the rotary kiln; 2) The rotary kiln rotates at 0.25r / min, and the filling rate of the mixed material in the kiln is 18%. Under the rotation of the rotary kiln, the mixed material continuously flows from the inlet end to the outlet end during the turning and flowing process, and exchanges heat with the high-temperature flue gas flowing in the kiln in reverse, so that the temperature of the mixed material continues to rise; 3) When the temperature of the mixture rises to 600°C, the iron ore begins to undergo reduction reaction under the action of carbon in the residual carbon, and as the temperature of the mixture rises, the reduction reaction rate of the iron ore accelerates, and the metallurgical gas overflowing from the mixture burns under the action of air blown in by the kiln back fan, and supplies heat to the rotary kiln; the reduction temperature of the iron ore is also controlled at 1050°C, and the reduction time is 160min. The metallized material discharged from the discharge end of the rotary kiln is taken for component analysis, and its total iron TFe content, metallic iron content MFe and metallization rate are shown in Table 3.

[0032] Table 3 Main components of metallized materials produced by rotary kiln in the prior art It can be seen from the data in Table 2 and Table 3 above that compared with the metallized materials produced by the rotary kiln in the prior art, the metallized materials produced by the rotary kiln in the present invention have a total iron content increased by 7.22%, a metallic iron content increased by 9.90%, and a metallization rate content increased by 7.24%.

Claims

1. A method for improving the reduction efficiency of a rotary kiln for iron ore coal-based hydrogen metallurgy, characterized in that: The following steps are involved: 1) A rotary kiln is provided, wherein the rotary kiln comprises a rotary kiln body (1), wherein a material retaining ring (2) having a parabola-like cross-section is provided at a discharge end port inside the rotary kiln body (1), at a position 1 / 3 of the total length of the rotary kiln away from the discharge end port, and at a position 2 / 3 of the total length of the rotary kiln away from the discharge end port, respectively; the height of the material retaining ring (2) 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; and a granular coal spray gun (3) on a kiln head cover at the discharge end of the rotary kiln body (1) is eccentrically arranged, and the eccentric direction is close to the inner diameter of the rotary kiln. The center position of the crescent-shaped material surface has an eccentric displacement of 10-20% of the inner diameter of the rotary kiln; a sleeve-type kiln head burner (4) is centrally arranged 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 1-1.5 times the air pressure; 2-5 kiln back draft fans (5) are evenly arranged on the rotary kiln body (1) along the length direction of the kiln body, and the air supply volume of each kiln back draft fan is 25-35% of the total air supply volume, and the air supply pressure is 6-8 KPa; 2) Mix the iron ore and the residual carbon in a weight ratio of 100:25-100:35 and add them into the rotary kiln from the feeding end of the rotary kiln; 3) Under the rotation of the rotary kiln, the mixed material continuously flows from the feeding end to the discharging end during the turning and flowing process, and exchanges heat with the high-temperature flue gas flowing in the kiln, so that the temperature of the mixed material continues to rise; 4) When the temperature of the mixture rises to 600℃, the iron ore begins to undergo reduction reaction under the action of carbon in the residual carbon, and as the temperature of the mixture rises, the reduction reaction rate of the iron ore accelerates, and the metallurgical gas overflowing from the mixture burns under the action of the air blown by the kiln back fan, and supplies heat to the rotary kiln; by controlling the reduction temperature of the iron ore at 900-1100℃ and the reduction time at 90-180min, the iron ore can be fully reduced.

2. A method for improving the reduction efficiency of a rotary kiln for iron ore coal-based hydrogen metallurgy as claimed in claim 1, characterized in that: The filling rate of the material in the rotary kiln is 20-25%, and the rotation speed of the rotary kiln is 0.6-0.8 r / min.

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