A magnetic roasting rotary kiln and its ore phase transformation method

Abstract

The present invention discloses a magnetic roasting rotary kiln and a method for mineral phase transformation thereof. The rotary kiln comprises a rotary kiln cylinder and a kiln head box and a kiln tail box installed at both ends of the rotary kiln cylinder. A coal powder classification burner is installed on the kiln head box, and the output port of the coal powder classification burner faces the kiln tail box. A plurality of air inlet pipes for supplementing combustion-supporting air are installed along the length direction of the rotary kiln cylinder, and the output port of the air inlet pipe faces the same direction as the output port of the coal powder classification burner. The present invention adopts a segmented air supply method, and the coal powder classification burner and a plurality of air inlet pipes located on the rotary kiln body jointly provide combustion-supporting air. By adjusting the conveying wind speed and air volume, the spacing between each air inlet pipe and the air inlet volume, the combustion of coal with different particle sizes in different areas of the rotary kiln and the combustion reaction intensity are controlled.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy and ore dressing equipment, and in particular relates to a temperature and atmosphere controllable magnetized roasting rotary kiln and an ore phase transformation method thereof. Background Art

[0002] According to statistics, the amount of difficult-to-select siderite (limonite), fine-grained hematite, oolitic hematite and iron-containing waste slag in my country exceeds 20 billion tons. Such difficult-to-select iron ore resources are separated by traditional magnetic separation, gravity separation, flotation or physical separation combined processes, which not only results in low iron concentrate grade, but also low iron recovery rate. A large number of laboratory test studies have shown that the "magnetic roasting-weak magnetic separation" process is the best method for separating such difficult-to-process iron ore resources.

[0003] As the most widely used magnetic roasting technology in industry, the biggest difficulty of magnetic roasting in rotary kiln lies in the reasonable regulation of temperature field and atmosphere field. The fuel and combustion-supporting gas of conventional rotary kiln are supplied from the kiln head at one time. The combustion intensity is the highest in the area 10m to 15m in front of the burner outlet, and the peak temperature of the flame reaches above 1500℃. The peak temperature of the high-temperature zone is high, while the temperature zone required for the reaction is short, forming a temperature field similar to the "hump-shaped" distribution. This temperature field distribution is easy to cause the rotary kiln to form rings and reduce the roasting time insufficiently, causing the rotary kiln to form rings and the reduction conversion rate to be low, which makes the roasting process difficult to operate stably. At the same time, the conventional multi-channel combustion device provides fuel in the central channel and air in the peripheral channel. In this combustion mode where the air flow wraps the fuel flow, the radial reduction medium concentration distribution is a decrease in the outward single gradient direction. The O2 partial pressure at the solid-gas contact surface is high, which is easy to cause the reduction product to be partially secondary oxidized, reducing the quality of the roasted ore.

[0004] To this end, the roasting process in which the reaction temperature and atmosphere need to be reasonably regulated is controlled by zone, and a temperature and atmosphere controllable magnetized roasting rotary kiln and a method for ore phase transformation using the rotary kiln are provided to ensure that the reduction roasting reaction proceeds smoothly while the roasted ore is not secondary oxidized, which has important practical significance for the reduction roasting production of weakly magnetic iron ore and pyrolusite ore. Summary of the invention

[0005] The object of the present invention is to provide a temperature and atmosphere controllable magnetization roasting rotary kiln and a mineral phase transformation method thereof, so as to solve the above problems.

[0006] To achieve the above-mentioned purpose, the present invention first discloses a magnetized roasting rotary kiln, comprising a rotary kiln cylinder and a kiln head box and a kiln tail box installed at both ends of the rotary kiln cylinder, a coal powder grading burner is installed on the kiln head box, and the output port of the coal powder grading burner is facing the kiln tail box, and a plurality of air inlet pipes for supplementing combustion air are installed along the length direction of the rotary kiln cylinder, and the output port of the air inlet pipe is in the same direction as the output port of the coal powder grading burner.

[0007] Furthermore, the output port of the air inlet pipe and the output port of the pulverized coal classification burner are both close to or located on the axis of the rotary kiln cylinder.

[0008] Furthermore, the number of the air inlet pipes is greater than or equal to one and less than or equal to five.

[0009] Furthermore, the pulverized coal graded burner includes a coarse-grained coal powder supply channel, a coarse-grained coal powder conveying air channel, a combustion-supporting air supply channel, a fine-grained coal powder supply channel and a fine-grained coal powder conveying air channel. The combustion-supporting air supply channel gap is sleeved on the outside of the coarse-grained coal powder supply channel, the fine-grained coal powder supply channel gap is sleeved on the outside of the combustion-supporting air supply channel, the output end gap of the coarse-grained coal powder conveying air channel is inserted into the input end of the coarse-grained coal powder supply channel and is arranged in the conveying direction of the coarse-grained coal powder, and the output end of the fine-grained coal powder conveying air channel is inserted into the input end of the fine-grained coal powder supply channel and is arranged in the conveying direction of the fine-grained coal powder.

[0010] Furthermore, the fine-grained coal powder conveying air channel includes a fine-grained coal powder conveying air straight pipe and a fine-grained coal powder conveying air sleeve that are arranged at an intersection. The fine-grained coal powder conveying air sleeve is sleeved on the outside of the combustion-supporting air supply channel, and a fine-grained coal powder conveying air straight pipe flange is installed at the input end of the fine-grained coal powder conveying air straight pipe.

[0011] Furthermore, the fine-grained coal powder supply channel includes a fine-grained coal powder supply sleeve, a fine-grained coal powder supply divergent tube and a fine-grained coal powder supply straight tube. The fine-grained coal powder supply divergent tube is coaxially connected to the fine-grained coal powder supply sleeve and is gap-sleeved on the outside of the combustion-supporting air supply channel. One end of the fine-grained coal powder supply straight tube is connected to the side wall of the fine-grained coal powder supply divergent tube, and the other end is equipped with a fine-grained coal powder supply straight tube flange.

[0012] Furthermore, the output end of the fine coal powder supply straight pipe is arranged toward the output end of the fine coal powder conveying air casing.

[0013] Furthermore, the combustion-supporting air supply channel includes a combustion-supporting air supply straight pipe and a combustion-supporting air supply sleeve that are arranged to intersect each other, the combustion-supporting air supply sleeve is gap-sleeved on the outside of the coarse-grained coal powder supply channel, and a combustion-supporting air supply straight pipe flange is installed at the input end of the combustion-supporting air supply straight pipe.

[0014] Furthermore, the coarse-grained coal powder supply channel includes a coarse-grained coal powder supply elbow, a coarse-grained coal powder supply straight pipe connected at both ends of the coarse-grained coal powder supply elbow, and a coarse-grained coal powder supply center pipe, the combustion-supporting air supply sleeve is gap-sleeved on the outside of the coarse-grained coal powder supply center pipe, and a coarse-grained coal powder supply straight pipe flange is installed at the input end of the coarse-grained coal powder supply straight pipe, and the coarse-grained coal powder conveying air channel includes a coarse-grained coal powder conveying air straight pipe coaxially inserted into the coarse-grained coal powder supply elbow, and a coarse-grained coal powder conveying air flange is provided at the end of the coarse-grained coal powder conveying air straight pipe.

[0015] Then the present invention discloses a method for mineral phase transformation of a magnetized roasting rotary kiln, comprising the magnetized roasting rotary kiln described in the above scheme, comprising the following steps:

[0016] S1, crush the ore to the target size and store it;

[0017] S2, crushing the coal powder, and classifying the coal powder into coarse coal powder and fine coal powder after crushing, and storing them separately;

[0018] S3. After the pulverized coal classification burner is ignited, the coarse pulverized coal in the coarse pulverized coal supply channel is sprayed into the rotary kiln for combustion reaction through the spraying and entraining effect of the coarse pulverized coal conveying air channel; the fine pulverized coal in the fine pulverized coal supply channel is sprayed into the rotary kiln for combustion reaction through the spraying and entraining effect of the fine pulverized coal conveying air channel; the air inlet volume of the combustion-supporting air supply channel and the air inlet pipe is adjusted to enable the rotary kiln to achieve an ideal atmosphere field and temperature field;

[0019] S4, the crushed ore is weighed and input into the tail of the rotary kiln, and the inclined rotary kiln cylinder is rotated to make the ore roll toward the head of the rotary kiln, thereby completing the ore phase transformation process.

[0020] Furthermore, the particle size of the ore after crushing is 0 to 22 mm, and the classified particle size of the coal powder is 100 mesh to 325 mesh.

[0021] Furthermore, in step S3, the ratio of the air volume of the combustion-supporting air supply channel to the air volume of the air inlet pipe is 1:1 to 3:1, and the air volume of the air inlet pipe is 5% to 25% of the total amount of the combustion-supporting air of the rotary kiln.

[0022] Compared with the prior art, the advantages of the present invention are:

[0023] The present invention adopts a segmented air supply mode, wherein a pulverized coal classification burner and a plurality of air inlet pipes located on the rotary kiln body jointly provide combustion-supporting gas. By adjusting the conveying wind speed and air volume, the spacing between each air inlet pipe and the air inlet volume, the combustion of coal with different particle sizes in different areas of the rotary kiln and the intensity of the combustion reaction are controlled. While reasonably adjusting the strength of the reducing atmosphere in different areas of the rotary kiln, the problem of local excessive temperature and more thermal NOx gas generated by the superposition of heat released by the combustion of coarse coal and fine coal can be reduced, forming a temperature field and atmosphere field suitable for ore phase transformation, making the reduction roasting process more green and environmentally friendly; further, the present invention pre-divides the coal powder into two particle sizes of coarse coal powder and fine coal powder. The coarse coal powder enters the rear position of the rotary kiln under the action of the induced air flow jet, and an incomplete combustion reaction gradually occurs in the middle and rear part of the rotary kiln. Because the particle size of this part of the coal powder is coarser, it takes a longer time for complete combustion, thereby maintaining a wider reducing atmosphere field; the fine coal powder has stronger reaction activity and takes a shorter time for complete combustion, and an incomplete combustion reaction occurs in the area near the kiln head of the reactor, maintaining the temperature field and atmosphere field required for the reaction in the area near the kiln head.

[0024] The present invention will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0026] Figure 1 It is a schematic diagram of the structure of the magnetization roasting rotary kiln of the present invention;

[0027] Figure 2 It is a structural schematic diagram of a pulverized coal classification burner of a magnetized roasting rotary kiln of the present invention;

[0028] Figure 3 The figure shows the CO concentration distribution at a distance of 10 m from the kiln head after the pulverized coal classification burner of the present invention is burned in a φ4m×50m rotary kiln without adding any material.

[0029] Figure 4 The figure shows the CO concentration distribution at a distance of 10 m from the kiln head when the pulverized coal classification burner of the present invention is burned in a φ4m×50m rotary kiln and then charged.

[0030] Legend:

[0031] 10. Coal powder classification burner; 11. Coarse coal powder conveying air channel; 111. Coarse coal powder conveying air straight pipe; 112. Coarse coal powder conveying air flange; 12. Coarse coal powder supply channel; 121. Coarse coal powder supply elbow pipe; 122. Coarse coal powder supply straight pipe; 123. Coarse coal powder supply center pipe; 124. Coarse coal powder supply straight pipe flange; 13. Combustion-supporting air supply channel; 131. Combustion-supporting air supply straight pipe; 132. Combustion-supporting air supply casing; 133, combustion-supporting air supply straight pipe flange; 14, fine-grained coal powder supply channel; 141, fine-grained coal powder supply casing; 142, fine-grained coal powder supply gradually expanding pipe; 143, fine-grained coal powder supply straight pipe; 144, fine-grained coal powder supply straight pipe flange; 15, fine-grained coal powder conveying air channel; 151, fine-grained coal powder conveying air straight pipe; 152, fine-grained coal powder conveying air casing; 153, fine-grained coal powder conveying air straight pipe flange.

[0032] 20. Rotary kiln cylinder; 21. Air inlet pipe; 211. First air inlet pipe; 212. Second air inlet pipe; 213. Third air inlet pipe;

[0033] 30. Kiln head box;

[0034] 40. Kiln tail box. DETAILED DESCRIPTION

[0035] The embodiments of the present invention are described in detail below with reference to the accompanying drawings, but the present invention can be implemented in many different ways as defined and covered by the claims.

[0036] like Figure 1-2 As shown, the present invention discloses a magnetized roasting rotary kiln, comprising a rotary kiln cylinder 20 and a kiln head box 30 and a kiln tail box 40 installed at both ends of the rotary kiln cylinder 20, a pulverized coal graded burner 10 is installed on the kiln head box 30, the pulverized coal graded burner 10 is inserted into the kiln head box 30, and its output port faces the kiln tail box 40, and a plurality of air inlet pipes 21 for supplementing combustion air are installed along the length direction of the rotary kiln cylinder 20, and the output port of the air inlet pipe 21 is in the same direction as the output port of the pulverized coal graded burner 10. The number of the air inlet pipes 21 is greater than or equal to one and less than or equal to five. In the present embodiment, the number of the air inlet pipes 21 is three, namely, the first air inlet pipe 211, the second air inlet pipe 212 and the third air inlet pipe 213. The distance L1 between the first air inlet pipe 211 and the kiln head of the rotary kiln is 10m, the distance L2 between the second air inlet pipe 212 and the first air inlet pipe 211 is 5m, and the distance L3 between the third air inlet pipe 213 and the second air inlet pipe 212 is 5m. Together with the combustion-supporting gas of the pulverized coal grading burner 10, they provide the rotary kiln with the air required for pulverized coal combustion.

[0037] In this embodiment, the outlet of the air inlet pipe 21 and the outlet of the pulverized coal classification burner 10 are both close to or located on the axis of the rotary kiln cylinder 20, and are preferably arranged on the axis of the rotary kiln cylinder 20, so as to achieve a better driving effect.

[0038] In this embodiment, if Figure 2 As shown, the pulverized coal graded burner 10 includes a coarse-grained coal supply channel 12, a coarse-grained coal conveying air channel 11, a combustion-supporting air supply channel 13, a fine-grained coal supply channel 14 and a fine-grained coal conveying air channel 15, all of which are formed by circular pipe fittings and have a socket layout, and the socketed pipes are separated by high-temperature resistant steel and are coaxially arranged. The combustion-supporting air supply channel 13 is gap-jacketed on the outside of the coarse-grained coal powder supply channel 12, and the fine-grained coal powder supply channel 14 is gap-jacketed on the outside of the combustion-supporting air supply channel 13. The output end of the coarse-grained coal powder conveying air channel 11 is gap-jacketed in the input end of the coarse-grained coal powder supply channel 12 and is arranged in the conveying direction of the coarse-grained coal powder. Therefore, the coarse-grained coal powder in the coarse-grained coal powder supply channel 12 is fed into the reactor at a high speed through the jetting effect of the coarse-grained coal powder conveying air channel 11, and the output end of the fine-grained coal powder conveying air channel 15 is gap-jacketed in the input end of the fine-grained coal powder supply channel 14 and is arranged in the conveying direction of the fine-grained coal powder. Similarly, the coarse-grained coal powder in the fine-grained coal powder supply channel 14 is fed into the reactor at a high speed through the jetting effect of the fine-grained coal powder conveying air channel 15.

[0039] Specifically, the fine-particle coal powder supply channel 14 includes a fine-particle coal powder supply sleeve 141, a fine-particle coal powder supply diffuser 142 and a fine-particle coal powder supply straight pipe 143. The fine-particle coal powder supply diffuser 142 is coaxially connected to the fine-particle coal powder supply sleeve 141. One end of the fine-particle coal powder supply straight pipe 143 is connected to the side wall of the fine-particle coal powder supply diffuser 142, and the other end is equipped with a fine-particle coal powder supply straight pipe flange 144, so as to facilitate connection with an external fine-particle coal powder storage device. The injection amount of fine-particle coal powder is reasonably adjusted according to the amount of fuel required for the reaction and the amount of coarse-particle coal powder that has been injected. The fine-particle coal powder conveying air channel 15 includes a fine-particle coal powder conveying air straight pipe 151 and a fine-particle coal powder conveying air sleeve 152, which are arranged with axes perpendicular to each other. The fine coal powder conveying air sleeve 152 is sleeved on the outside of the combustion-supporting air supply channel 13, and the input end of the fine coal powder conveying air straight pipe 151 is installed with a fine coal powder conveying air straight pipe flange 153, which is connected to an external air storage device through the fine coal powder conveying air straight pipe flange 153. The fine coal powder conveying air volume is reasonably adjusted according to the fine coal powder injection amount, and the fine coal powder is fed into the reactor at a high speed through the injection effect of the fine coal powder conveying gas to maintain the reducing atmosphere field in the head area of ​​the reactor. At the same time, because the outermost periphery of the burner is the fuel injection area, the concentration of the reducing medium in the reactor can be avoided from being distributed radially outward in a single gradient direction, thereby creating good reducing atmosphere conditions for reactions such as the reduction roasting of weakly magnetic iron ore and pyrolusite.

[0040] In this embodiment, the output end of the fine-grained coal powder supply straight pipe 143 is arranged toward the output end of the fine-grained coal powder conveying air sleeve 152, so that the falling material of the fine-grained coal powder supply straight pipe 143 can be output evenly through the annular conveying air of the fine-grained coal powder conveying air sleeve 152, thereby improving the conveying efficiency and preventing accumulation in the fine-grained coal powder supply gradually expanding pipe 142.

[0041] In this embodiment, the combustion-supporting air supply channel 13 includes a combustion-supporting air supply straight pipe 131 and a combustion-supporting air supply sleeve 132 which are arranged to intersect each other. The combustion-supporting air supply sleeve 132 is sleeved on the outside of the coarse-grained coal powder supply channel 12 with a gap, and a combustion-supporting air supply straight pipe flange 133 is installed at the input end of the combustion-supporting air supply straight pipe 131. The combustion-supporting air supply straight pipe flange 133 is connected to an external gas storage device. When in use, the combustion-supporting air volume is reasonably adjusted according to the distribution of the temperature field in the kiln and the injection amount of the coarse-grained coal powder to maintain the reducing atmosphere field in the middle and rear parts of the reactor.

[0042] In this embodiment, the coarse coal powder supply channel 12 includes a coarse coal powder supply elbow 121, a coarse coal powder supply straight pipe 122 connected to both ends of the coarse coal powder supply elbow 121, and a coarse coal powder supply center pipe 123. The combustion air supply sleeve 132 is sleeved on the outside of the coarse coal powder supply center pipe 123. The input end of the coarse coal powder supply straight pipe 122 is installed with a coarse coal powder supply straight pipe flange 124. The coarse coal powder conveying air channel 11 includes a coarse coal powder supply elbow 121, a coarse coal powder supply elbow 122, and a coarse coal powder supply elbow 122. The coarse coal powder conveying air straight pipe 111 in the powder supply elbow pipe 121, the end of the coarse coal powder conveying air straight pipe 111 is provided with a coarse coal powder conveying air flange 112, and the setting of the coarse coal powder supply elbow pipe 121 provides space for the insertion of the coarse coal powder conveying air straight pipe 111. At the same time, the coarse coal powder conveying air flange 112 is connected to the external air storage device through a pipeline, and the combustion-supporting air volume is reasonably adjusted according to the coarse coal powder injection amount to maintain a uniform temperature field in the middle and rear parts of the reactor. In the specific setting, the coarse coal powder conveying air straight pipe 111 is coaxially arranged with the coarse coal powder supply center pipe 123, so that the coarse coal powder conveying air straight pipe 111 has a better injection effect. The coarse coal powder is sprayed into the reactor at a high speed through the coarse coal powder supply center pipe 123 under the injection effect of the coarse coal conveying air. This part of coarse coal is sprayed to the middle and rear area of ​​the reactor under the drive of high-speed conveying wind, and a combustion reaction occurs in this area, providing the required heat to maintain the ideal temperature field in the middle and rear parts of the reactor. At the same time, because the particle size of this part of coal powder is coarser, the time required for complete combustion is relatively longer, and the gradual combustion reaction from the middle and rear parts of the reactor is conducive to the formation of a uniform temperature field.

[0043] At the same time, the pulverized coal is pre-classified into two particle sizes, coarse-grained pulverized coal and fine-grained pulverized coal. Different conveying wind speeds and air volumes are used to spray into the reactor, and combustion reactions are carried out in different areas of the reactor. The coarse-grained pulverized coal requires a relatively high injection wind speed, which is injected into the coarse-grained pulverized coal supply center tube 123 of the burner; the fine-grained pulverized coal requires a relatively low injection wind speed, which can be supplemented by the outermost layer of the burner. On the one hand, this can reasonably regulate the spatial distribution of the temperature field in the reactor, and on the other hand, it can reduce the scouring of the inner wall of the reactor during the injection process, thereby extending the service life and life of the refractory materials in the reactor.

[0044] In this embodiment, the output ends of the coarse-grained coal powder supply channel 12, the combustion-supporting air supply channel 13 and the fine-grained coal powder supply channel 14 are coaxially arranged, and the edges of the output ends of the coarse-grained coal powder supply channel 12, the combustion-supporting air supply channel 13 and the fine-grained coal powder supply channel 14 are flush, so that the combustion at the burner output end is more uniform and stable.

[0045] Furthermore, in this embodiment, the burner is installed on a φ4m×50m rotary kiln, and the physical and chemical parameters of the coal are shown in Table 1:

[0046] Table 1 Analysis results of physical and chemical parameters of coal

[0047] Ash content (%) Volatile matter (%) Ignition temperature℃ Fixed carbon (%) Calorific value (kcal / kg) Sulfur content (%) 8 34.66 369 54.58 7687.4 / 6843 0.37

[0048] The coal is finely ground by Raymond mill + hot air drying + wind conveying and then classified into +0.15mm coarse coal powder and -0.15mm fine coal powder and stored in suitable silos. After the radial atmosphere controllable burner of the present invention is used for coal injection combustion, the CO concentration distribution at 10m away from the kiln head in the rotary kiln is as follows: Figure 2 shown.

[0049] from Figure 3 The results show that the radial CO concentration at 10m away from the kiln head after combustion by the burner of the present invention is approximately distributed in an "M" shape. Compared with the radial CO concentration after combustion by a conventional burner, the CO concentration at the center after combustion by the burner of the present invention is lower and the CO concentration near the kiln wall is higher, which is consistent with the atmosphere requirements for material reaction.

[0050] Furthermore, the burner is installed on the above-mentioned φ4m×50m rotary kiln. The physical and chemical parameters of the coal remain unchanged. The ore feeding rate in the rotary kiln is 45-50t / h, and the corresponding coal powder injection rate is 35-40kg / t. 给矿 The radial concentration distribution of CO at a distance of 10m from the rotary kiln head is as follows: Figure 3 shown.

[0051] from Figure 4The results show that compared with the radial CO concentration distribution after combustion with a conventional burner, the CO concentration in the area near the material layer after combustion with the burner described in the present invention is higher, while the CO concentration in the upper area of ​​the kiln is lower, maintaining a relatively ideal spatial distribution of the magnetic roasting reduction field of weakly magnetic iron ore.

[0052] Then, the present invention also discloses a method for mineral phase transformation of a magnetized roasting rotary kiln, which uses the magnetized roasting rotary kiln of this embodiment and comprises the following steps:

[0053] S1. The ore is crushed to a target size and stored in a powder ore bin, wherein the particle size of the crushed ore is 0 to 22 mm; wherein the multi-element analysis results of the raw ore used for mineral phase magnetic roasting are shown in Table 2:

[0054] Table 2 Results of chemical multi-element analysis of raw ore / %

[0055] project TFe FeO <![CDATA[Fe2O3]]> <![CDATA[SiO2]]> <![CDATA[Al2O3]]> CaO MgO content 30.65 1.09 42.57 28.59 1.03 0.48 2.07 project MnO <![CDATA[Na2O]]> <![CDATA[K2O]]> P S Ig TFe / FeO content 0.58 0.12 2.59 0.093 2.82 16.32 28.12

[0056] S2, crushing the coal powder to a particle size of 100 mesh, 150 mesh, 200 mesh or 325 mesh, etc. After crushing, the coal powder is classified into coarse coal powder (+0.15mm) and fine coal powder (-0.15mm), and stored in a coarse coal powder bin and a fine coal powder bin respectively;

[0057] S3. After the pulverized coal classification burner 10 is ignited, the coarse pulverized coal in the coarse pulverized coal supply channel 12 is sprayed into the rotary kiln through the spraying and entraining action of the coarse pulverized coal conveying air channel 11 to cause a combustion reaction; the fine pulverized coal in the fine pulverized coal supply channel 14 is sprayed into the rotary kiln through the spraying and entraining action of the fine pulverized coal conveying air channel 15 to cause a combustion reaction; the air intake of the combustion-supporting air supply channel 13 and the air inlet pipe 21 is adjusted to make the rotary kiln reach an ideal atmosphere field and temperature field. Specifically, the ratio of the air intake of the combustion-supporting air supply channel 13 to the air intake of the air inlet pipe 21 is 1:1 to 3:1, and the air intake of the air inlet pipe 21 is 5% to 25% of the total amount of the combustion-supporting air of the rotary kiln; in this embodiment, the coal injection amount is controlled to be about 2.5 t / h, and the air supply amount of the burner is 6000m 3 / h, the air intake volume of the first air inlet pipe 211, the second air inlet pipe 212 and the third air inlet pipe 213 is 3000m 3 / h, the firing section temperature is 730℃±30℃, and the CO concentration is 3%±0.5%.

[0058] S4. After the crushed ore is weighed, it is fed into the tail of the rotary kiln along the chute. The weighing is performed by an electronic belt scale. The ore feeding rate is controlled at 45±5t / h. The inclined rotary kiln cylinder 20 is rotated to make the ore roll toward the head of the rotary kiln to complete the ore phase transformation process.

[0059] Through the above-mentioned method, the magnetic susceptibility of the weakly magnetic iron ore in this embodiment is as high as about 95%. Compared with the combustion method of the conventional three-channel burner + conventional rotary kiln, when the amount of ore fed, the amount of coal injection and the amount of air used are the same, the temperature and atmosphere of the present invention are flexibly controlled to control the magnetization roasting rotary kiln and the corresponding ore phase transformation method. The peak flame temperature and the O2 partial pressure at the solid-gas contact surface in the rotary kiln are reduced by about 15% and 40% respectively, and the length of the temperature zone above 730°C is extended by about 30%.

[0060] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A magnetized roasting rotary kiln, characterized in that: The rotary kiln comprises a rotary kiln cylinder (20), a kiln head box (30) and a kiln tail box (40) installed at both ends of the rotary kiln cylinder (20), a pulverized coal classification burner (10) being installed on the kiln head box (30), the output port of the pulverized coal classification burner (10) being oriented toward the kiln tail box (40), a plurality of air inlet pipes (21) for supplementing combustion-supporting air being installed along the length direction of the rotary kiln cylinder (20), the output port of the air inlet pipe (21) being oriented in the same direction as the output port of the pulverized coal classification burner (10); the pulverized coal classification burner (10) comprising a coarse-grained coal supply channel (12), a coarse-grained coal conveying air channel (11), a combustion-supporting air supply channel (13), a fine-grained coal supply channel (14) and a fine-grained coal conveying air channel (15), the combustion-supporting air supply channel (21) and the combustion-supporting air supply channel (21) being oriented toward the combustion-supporting air supply channel (12), and the combustion-supporting air supply channel (13) and the combustion-supporting air supply channel (14) being oriented toward the combustion-supporting air supply channel (14). The inlet channel (13) is gap-sleeved on the outside of the coarse-grained coal powder supply channel (12), the fine-grained coal powder supply channel (14) is gap-sleeved on the outside of the combustion-supporting air supply channel (13), the output end of the coarse-grained coal powder conveying air channel (11) is gap-inserted into the input end of the coarse-grained coal powder supply channel (12) and is arranged in the conveying direction of the coarse-grained coal powder, and the output end of the fine-grained coal powder conveying air channel (15) is gap-inserted into the input end of the fine-grained coal powder supply channel (14) and is arranged in the conveying direction of the fine-grained coal powder; the output port of the air inlet pipe (21) and the output port of the coal powder grading burner (10) are both close to or located on the axis of the rotary kiln cylinder (20); the number of the air inlet pipes (21) is greater than or equal to one and less than or equal to five.

2. The magnetization roasting rotary kiln according to claim 1, characterized in that: The fine-grained coal powder conveying air channel (15) comprises a fine-grained coal powder conveying air straight pipe (151) and a fine-grained coal powder conveying air sleeve (152) arranged to intersect each other; the fine-grained coal powder conveying air sleeve (152) is sleeved on the outside of the combustion-supporting air supply channel (13); and a fine-grained coal powder conveying air straight pipe flange (153) is installed at the input end of the fine-grained coal powder conveying air straight pipe (151).

3. The magnetization roasting rotary kiln according to claim 2, characterized in that: The fine-grained coal powder supply channel (14) comprises a fine-grained coal powder supply sleeve (141), a fine-grained coal powder supply gradually expanding tube (142) and a fine-grained coal powder supply straight tube (143); the fine-grained coal powder supply gradually expanding tube (142) is coaxially connected to the fine-grained coal powder supply sleeve (141) and is gap-sleeved on the outside of the combustion-supporting air supply channel (13); one end of the fine-grained coal powder supply straight tube (143) is connected to the side wall of the fine-grained coal powder supply gradually expanding tube (142), and the other end is provided with a fine-grained coal powder supply straight tube flange (144).

4. The magnetization roasting rotary kiln according to claim 3, characterized in that: The output end of the fine coal powder supply straight pipe (143) is arranged toward the output end of the fine coal powder conveying air sleeve (152).

5. The magnetization roasting rotary kiln according to claim 1, characterized in that: The combustion-supporting air supply channel (13) comprises a combustion-supporting air supply straight pipe (131) and a combustion-supporting air supply sleeve (132) which are arranged to intersect each other; the combustion-supporting air supply sleeve (132) is sleeved on the outside of the coarse-grained coal powder supply channel (12) with a gap; and a combustion-supporting air supply straight pipe flange (133) is installed at the input end of the combustion-supporting air supply straight pipe (131).

6. The magnetized roasting rotary kiln according to claim 5, characterized in that: The coarse-grained coal powder supply channel (12) comprises a coarse-grained coal powder supply elbow (121), a coarse-grained coal powder supply straight pipe (122) connected to both ends of the coarse-grained coal powder supply elbow (121), and a coarse-grained coal powder supply center pipe (123); the combustion-supporting air supply sleeve (132) is sleeved on the outside of the coarse-grained coal powder supply center pipe (123); a coarse-grained coal powder supply straight pipe flange (124) is installed at the input end of the coarse-grained coal powder supply straight pipe (122); the coarse-grained coal powder conveying air channel (11) comprises a coarse-grained coal powder conveying air straight pipe (111) coaxially inserted into the coarse-grained coal powder supply elbow (121); and a coarse-grained coal powder conveying air flange (112) is provided at the end of the coarse-grained coal powder conveying air straight pipe (111).

7. A method for mineral phase transformation in a magnetized roasting rotary kiln, characterized in that: The magnetized roasting rotary kiln comprises the following steps: S1, crushing the ore to a target size and then storing it; S2, crushing the coal powder, and classifying the coal powder into coarse coal powder and fine coal powder after crushing, and storing them separately; S3, igniting the coal powder classification burner (10), and spraying the coarse coal powder in the coarse coal powder supply channel (12) into the rotary kiln through the ejection effect of the coarse coal powder conveying air channel (11) to cause a combustion reaction; S4, igniting the coarse coal powder grading burner (10), and spraying the coarse coal powder in the coarse coal powder supply channel (12) into the rotary kiln through the ejection effect of the coarse coal powder conveying air channel (11) to cause a combustion reaction; The fine coal powder in the fine coal powder supply channel (14) is sprayed into the rotary kiln by the ejection effect of the powder conveying air channel (15) to cause a combustion reaction; the air intake of the combustion-supporting air supply channel (13) and the air intake pipe (21) is adjusted so that the rotary kiln reaches an ideal atmosphere field and temperature field; S4, the crushed ore is metered and input into the tail of the rotary kiln, and the inclined rotary kiln cylinder (20) is rotated to make the ore roll toward the head of the rotary kiln to complete the ore phase transformation process.

8. The method for mineral phase transformation of a magnetized roasting rotary kiln according to claim 7, characterized in that: The particle size of the ore after crushing is 0-22 mm, and the classified particle size of the coal powder is 100 meshes to 325 meshes.

9. The method for mineral phase transformation of a magnetized roasting rotary kiln according to claim 7, characterized in that: In step S3, the ratio of the air volume of the combustion-supporting air supply channel (13) to the air volume of the air inlet pipe (21) is 1:1 to 3:1, and the air volume of the air inlet pipe (21) is 5% to 25% of the total amount of the combustion-supporting air of the rotary kiln.

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