Method for producing aluminum oxide by extracting iron from high-iron gibbsite

Abstract

The invention discloses a method for producing aluminum oxide by extracting iron from high-iron gibbsite, which comprises the following steps: S10, carrying out crushing treatment on pre-homogenized high-iron gibbsite to obtain high-iron gibbsite crushed ore; s20, the high-iron bauxite trihydrate crushed ore is subjected to high-pressure roller milling, and high-iron raw ore powder is obtained; s30, the high-iron raw ore powder is converted into magnetic high-iron clinker ore powder through suspension magnetization roasting; s40, the magnetic high-iron clinker ore powder is subjected to aluminum-iron separation through a dry magnetic separator, and high-aluminum low-iron clinker ore powder and high-iron low-aluminum clinker ore powder are obtained through separation; s50, the high-aluminum low-iron clinker mineral powder is fed into a Bayer process system for aluminum oxide production; and S60, the high-iron low-aluminum clinker ore powder is prepared into refined iron ore powder. According to the method, after the high-iron gibbsite is subjected to dry-method pulverizing, magnetizing roasting and aluminum-iron separation, comprehensive utilization of powdery weak-magnetism iron ore materials is achieved; the process is high in operation rate and stable in product quality, and can be perfectly linked with upstream and downstream selection and ironmaking sections.

Description

Technical Field

[0001] The invention belongs to the technical field of alumina production, and specifically relates to a method for producing alumina by extracting iron from high-iron bauxite. Background Art

[0002] High-iron bauxite refers to bauxite with Fe2O3≥15%, which is divided into diaspore type and gibbsite type, and is associated with minerals such as goethite, hematite, limonite, and kaolinite. Among the bauxite imported by my country, Guinea, Indonesia, Austria, Jamaica, and Solomon are high-iron gibbsite. Taking Solomon Mine as an example, the mine has Al2O3≥45%, Fe2O3≤26%, A / S≥15, total sulfur≤0.1, and total carbon≤1.2. Among them, Al2O3 and Fe2O3 are valuable mineral resources, but the content does not meet the industrial grade requirements. Therefore, it is very difficult to produce Al2O3 or metallic iron using traditional methods from this type of ore.

[0003] Research on the comprehensive utilization of high-iron trihydrate bauxite has been carried out for many years at home and abroad, and the iron-aluminum separation method, the aluminum-first-then-iron method, and the iron-first-then-aluminum method have appeared successively. However, due to the intercalation and bonding of iron and aluminum in high-iron trihydrate bauxite and their close symbiosis, it is extremely difficult to separate iron and aluminum. So far, high-iron trihydrate bauxite has not been truly effectively developed and utilized. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides a method for dry powdering of bauxite based on a high pressure roller mill, so as to simplify the grinding process of bauxite, reduce equipment investment, reduce the floor space occupied by equipment, improve the operating efficiency of equipment and reduce energy consumption.

[0005] In order to achieve the above object, the present invention adopts the following technical solution:

[0006] A method for producing alumina from high-iron bauxite trihydrate, the method comprising the steps of:

[0007] S10, crushing the pre-homogenized high-iron trihydrate bauxite to obtain high-iron trihydrate bauxite crushed ore;

[0008] S20, sending the high-iron bauxite ore into a high-pressure roller mill final grinding system for high-pressure roller grinding to obtain high-iron raw material ore powder;

[0009] S30, feeding the high-speed iron raw material powder into a suspended magnetic roasting furnace, using a pulverized coal hot blast furnace to provide high-temperature flue gas for magnetic roasting and CO produced by a gasifier as a magnetic roasting reducing agent, and converting the high-speed iron raw material powder into magnetic high-speed iron clinker powder through suspended magnetic roasting;

[0010] S40, separating the magnetic high-iron clinker powder into aluminum and iron by a dry magnetic separator to obtain high-aluminum and low-iron clinker powder and high-iron and low-aluminum clinker powder;

[0011] S50, sending the high-aluminum and low-iron clinker powder into a Bayer process system to produce alumina;

[0012] S60, mixing the high-iron and low-aluminum clinker powder with mother liquor and lime milk to prepare high-iron slurry, sending it into the high-iron dissolution casing for dissolution at 140-150°C, the high-iron slurry after dissolution enters the high-iron slurry sedimentation washing tank, the overflow enters the high-aluminum slurry red mud sedimentation system, the underflow is the refined iron ore mud, which is sent to the refined iron ore powder filter press by the underflow slurry pump to be prepared into refined iron ore powder.

[0013] Preferably, in step S10, the particle size of the high-iron bauxite ore is not greater than 50 mm.

[0014] Preferably, in step S20, the particle size index of the high iron raw material powder is: 100%≤0.3mm, 80%-95%≤0.15mm, 50%-75%≤0.074mm; the moisture content of the high iron raw material powder is not more than 2%.

[0015] Preferably, the drying heat source of the high-pressure roller grinding process in step S20 comes from the high-temperature waste heat recovery flue gas of the suspended magnetization roasting system in step S30.

[0016] Preferably, in step S30, the temperature of the suspended magnetization calcination is 600°C to 700°C.

[0017] The embodiment of the present invention provides a method for extracting iron from high-iron bauxite to produce alumina. After the high-iron bauxite is subjected to dry pulverization-magnetic roasting-aluminum-iron separation, the comprehensive utilization of powdered weakly magnetic iron ore materials is realized; the process has a high operation rate and stable product quality, and can be perfectly connected with upstream and downstream mining and ironmaking sections; the traditional stacked gas-solid heat exchange is changed to an efficient suspended gas-solid heat exchange, so that the heat of the exhaust gas can be fully utilized, the thermal efficiency of the system is greatly improved, and after effectively reducing organic matter and increasing the activity of bauxite, atmospheric pressure dissolution is performed, which can make alumina dissolve quickly in a shorter time, so that the reaction rate of silicon dioxide is significantly different from that of alumina, thereby inhibiting the dissolution of silicon dioxide in the mineral to a certain extent, so that the loss of alumina caused by the dissolution of silicon dioxide can be reduced, not only the separation of iron and aluminum in the mineral is achieved, but also the alumina in the mineral can be effectively utilized. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a process diagram of a method for extracting iron from high-iron bauxite to produce alumina in an embodiment of the present invention. DETAILED DESCRIPTION

[0019] To make the purpose, technical solutions and advantages of the present invention clearer, the present invention is described in detail below in conjunction with specific embodiments. However, the present invention can be implemented in many different forms, and the present invention should not be construed as being limited to the specific embodiments set forth herein. On the contrary, these embodiments are provided to explain the principles of the present invention and their practical applications, so that other persons skilled in the art can understand the various embodiments of the present invention and the various modifications suitable for specific intended applications.

[0020] The embodiment of the present invention provides a method for producing alumina from high-iron bauxite. The main equipment involved includes: an ore crushing system, a homogenizing storage stacker and reclaimer, a high-pressure roller mill final grinding system, a high-temperature / low-temperature dust collector, an air conveying chute, a bucket elevator, a suspended magnetic roasting furnace, a gas generator, a dry magnetic separator, a dissolution casing, a slurry pump, an iron ore concentrate powder washing and settling tank, an iron ore concentrate powder filter press and other commonly used equipment.

[0021] See also Figure 1 The present invention provides a method for producing alumina from high-iron bauxite ore, which mainly comprises the following steps:

[0022] Step S10, crushing the pre-homogenized high-iron bauxite to obtain high-iron bauxite crushed ore.

[0023] Step S20, sending the high-iron bauxite ore into the high-pressure roller mill final grinding system for high-pressure roller grinding to obtain high-iron raw material ore powder.

[0024] Step S30, the high-speed iron raw material powder is fed into a suspended magnetic roasting furnace, and a pulverized coal hot blast furnace is used to provide high-temperature flue gas for magnetic roasting and CO produced by a gasifier is used as a magnetic roasting reducing agent to transform the high-speed iron raw material powder into magnetic high-speed iron clinker powder through suspended magnetic roasting.

[0025] Step S40, subjecting the magnetic high-iron clinker ore powder to aluminum-iron separation through a dry magnetic separator to obtain high-aluminum and low-iron clinker ore powder and high-iron and low-aluminum clinker ore powder.

[0026] Step S50: sending the high-aluminum and low-iron clinker powder into the Bayer process system to produce alumina.

[0027] Step S60, the high-iron and low-aluminum clinker ore powder is mixed with the mother liquor and lime milk to prepare a high-iron slurry, which is sent into the high-iron dissolution casing for dissolution at 140-150°C. The high-iron slurry after dissolution enters the high-iron slurry sedimentation washing tank, and the overflow enters the high-aluminum slurry red mud sedimentation system. The underflow is the refined iron ore mud, which is sent into the refined iron ore powder filter press through the underflow slurry pump to be prepared into refined iron ore powder.

[0028] Specifically, in step S10, the high-iron bauxite is pre-homogenized and stockpiled after arriving at the site, and the raw ore is crushed into high-iron bauxite with a particle size of ≤50 mm by the ore crushing system, and then sent to the homogenization bin for homogenization and stockpiling through the ore belt, and finally the high-iron bauxite with a particle size of ≤50 mm is sent to the high-pressure roller mill final grinding system through the homogenization bin feeder and the ore belt.

[0029] Specifically, in step S20, the high pressure roller mill final grinding system grinds the high iron trihydrate bauxite with a particle size of ≤50mm into high iron raw material powder, and the particle size index of the high iron raw material powder is: 100%≤0.3mm, 80%-95%≤0.15mm, 50%-75%≤0.074mm; 100%≤0.3mm, 80%-95%≤0.15mm, 50%-75%≤0.074mm, that is, the particle size of all mineral powders is not greater than 0.3mm, the particle size of more than 80%-95% of the mineral powders is not greater than 0.15mm, and the particle size of 50%-75% of the mineral powders is not greater than 0.074mm. The moisture content of the bauxite powder is not greater than 2%. Among them, the drying heat source of the final grinding pair comes from the waste heat recovery flue gas at about 300℃ of the suspended magnetic roasting system, and the high-speed iron raw material ore powder is sent into the raw material silo through air chutes, bucket elevators, etc.

[0030] Specifically, in step S30, the high-iron raw material powder in the raw material bin is sent into the suspended magnetic roasting furnace through the air chute and the bucket elevator, the pulverized coal hot blast furnace is used to provide the high-temperature flue gas for magnetic roasting, and the CO produced by the gas generator provided by the alumina plant is used as the magnetic roasting reducing agent. The high-iron bauxite raw material powder is subjected to flash suspended magnetic roasting at 600°C to 700°C for about 15 seconds, and the powdery non-(weakly) magnetic high-iron ore powder is transformed into magnetic high-iron clinker ore powder.

[0031] In the embodiment of the present invention, the magnetization roasting test results of a certain imported high-iron bauxite (Al2O3≥45%, Fe2O3≤26%, moisture≤12%) are as shown in Tables 1 to 3 below:

[0032] Table 1: Multi-element analysis results of ore after roasting

[0033] element <![CDATA[Al2O3]]> <![CDATA[SiO2]]> <![CDATA[Fe2O3]]> <![CDATA[TiO2]]> <![CDATA[K2O]]> <![CDATA[Na2O]]> CaO MgO Burn reduction content / % 59.44 1.74 21.17 2.09 0.06 0.27 2.38 0.41 8.27

[0034] Table 2: Phase analysis results of ore after roasting

[0035] phase of matter <![CDATA[γ-Al2O3]]> Hematite quartz Anatase Metakaolinite Calcium Oxide content / % 58.00 21.00 1.00 2.00 1.70 2.40

[0036] Table 3: Calcination experiment

[0037] condition Mass before calcination / g Mass after calcination / g Weight loss / g Weight loss rate / % 650-700 degrees, 2h 320 219.23 100.77 31.49

[0038] Specifically, in step S50, the high-aluminum and low-iron clinker powder is fed into a Bayer process system, and alumina is produced by referring to the existing technology.

[0039] Specifically, in step S60, the high-iron and low-aluminum clinker powder is mixed with the mother liquor and lime milk to prepare a high-iron slurry, which enters the high-iron slurry tank and is pumped into the high-iron dissolution casing for dissolution at 140°C to 150°C. The high-iron slurry after dissolution enters the high-iron slurry sedimentation washing tank, and the overflow enters the high-aluminum slurry red mud sedimentation system (i.e., enters the Bayer process alumina production process). The underflow is the refined iron ore mud, which is pumped into the refined iron ore powder filter press by the underflow slurry pump to be prepared into refined iron ore powder.

[0040] Based on the above process flow, the scheme proposed by the present invention realizes the comprehensive utilization of powdered weakly magnetic iron ore materials after high-iron bauxite is dry-pulverized-magnetized roasting-aluminum-iron separation; the process has a high operating rate and stable product quality, and can be perfectly connected with upstream and downstream mining and ironmaking sections; the traditional stacked gas-solid heat exchange is changed to an efficient suspended gas-solid heat exchange, so that the heat of the exhaust gas can be fully utilized, the thermal efficiency of the system is greatly improved, and after effectively reducing organic matter and increasing the activity of bauxite, normal pressure dissolution is carried out, which can make alumina dissolve quickly in a shorter time, so that the reaction rate of silica is significantly different from that of alumina, thereby inhibiting the dissolution of silica in the mineral to a certain extent, so that the loss of alumina caused by the dissolution of silica can be reduced, not only the separation of iron and aluminum in the mineral is achieved, but also the alumina in the mineral can be effectively utilized.

[0041] While the invention has been shown and described with reference to the particular embodiments, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the claims and their equivalents.

Claims

1. A method for producing alumina from high-iron bauxite, characterized in that: The method comprises the steps of: S10, crushing the pre-homogenized high-iron trihydrate bauxite to obtain high-iron trihydrate bauxite crushed ore; S20, sending the high-iron bauxite ore into a high-pressure roller mill final grinding system for high-pressure roller grinding to obtain high-iron raw material ore powder; S30, feeding the high-speed iron raw material powder into a suspended magnetic roasting furnace, using a pulverized coal hot blast furnace to provide high-temperature flue gas for magnetic roasting and CO produced by a gasifier as a magnetic roasting reducing agent, and converting the high-speed iron raw material powder into magnetic high-speed iron clinker powder through suspended magnetic roasting; S40, separating the magnetic high-iron clinker powder into aluminum and iron by a dry magnetic separator to obtain high-aluminum and low-iron clinker powder and high-iron and low-aluminum clinker powder; S50, sending the high-aluminum and low-iron clinker powder into a Bayer process system to produce alumina; S60, mixing the high-iron and low-aluminum clinker powder with mother liquor and lime milk to prepare high-iron slurry, sending it into the high-iron dissolution casing for dissolution at 140-150°C, the high-iron slurry after dissolution enters the high-iron slurry sedimentation washing tank, the overflow enters the high-aluminum slurry red mud sedimentation system, the underflow is the refined iron ore mud, which is sent to the refined iron ore powder filter press by the underflow slurry pump to be prepared into refined iron ore powder.

2. The method according to claim 1, characterized in that In step S10, the particle size of the high-iron bauxite ore is not greater than 50 mm.

3. The method according to claim 1, characterized in that In step S20, the particle size index of the high iron raw material powder is: 100%≤0.3mm, 80%-95%≤0.15mm, 50%-75%≤0.074mm; the moisture content of the high iron raw material powder is not more than 2%.

4. The method according to claim 1, characterized in that: The drying heat source of the high-pressure roller mill process in step S20 comes from the high-temperature waste heat recovery flue gas of the suspended magnetization roasting system in step S30.

5. The method according to claim 1, characterized in that In step S30, the temperature of the suspended magnetization calcination is 600°C to 700°C.

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