An integrated tunnel kiln for calcination and desilication of bauxite to produce brown fused alumina

Abstract

The present invention discloses an integrated tunnel kiln for calcining and desiliconizing bauxite to produce brown corundum. From the kiln tail to the kiln head, the kiln comprises a preheating section, a roasting section, a cooling section, and a spraying section. A spray pipe with a nozzle is located above the spraying section, one end of which extends out of the tunnel kiln and is connected to an alkali spraying device. The kiln wall of the spraying section is provided with several liquid leakage holes, and a liquid collection tank is located below the spraying section. The equipment of the present invention can simultaneously calcine and desiliconize lump (lump) bauxite, achieving continuous and intelligent production. This equipment is more conducive to using reduced-grade fine ore for brown corundum production. When used in conjunction with new processes, it offers high processing efficiency, greater energy conservation and environmental protection, and lower desiliconization costs.

Description

Technical Field

[0001] The invention relates to processing equipment for producing brown corundum from bauxite, in particular to a calcination-desiliconization integrated tunnel kiln for producing brown corundum from bauxite. Background Art

[0002] Brown corundum, also known as diamond dust, is a man-made corundum. Its primary chemical component is Al₂O₃, with a content ranging from 95.00% to 97.00%, along with small amounts of Fe, Si, and Ti. Brown corundum is a fundamental abrasive, known for its excellent grinding properties and wide range of applications.

[0003] Traditional brown corundum is produced by melting and reducing three raw materials: bauxite, carbon material, and iron filings in an electric arc furnace. Brown corundum has very high requirements for the amount of bauxite raw material, requiring an Al2O3 grade of no less than 80% and a SiO2 content of no more than 6%. However, with the growth and development of my country's alumina industry, the reserves of high-quality bauxite are becoming increasingly scarce, and companies are forced to face the reality of declining raw material grades. The existing brown corundum smelting process uses natural, high-quality lump bauxite, which is calcined and dehydrated before entering the smelting process. These dense lump ore have a large temperature difference between the inside and outside of the smelting process, requiring higher smelting temperatures and longer smelting times, which increases smelting energy consumption. Furthermore, the composition of natural lump ore varies, and this uneven composition leads to reduced product quality and a lower yield rate.

[0004] During the mining process, ore is often accompanied by a large amount of powdered bauxite. Due to its poor air permeability, powdered ore easily clogs the furnace, generates excessive dust, and pollutes the environment. Currently, powdered ore is not used as a smelting raw material. The reduction in bauxite grade is mainly due to the increase in silicon content in the ore. Therefore, how to use fine ore, especially reduced-grade fine ore, for brown corundum production is a major issue of concern to both companies and researchers.

[0005] With the continuous deepening of research, a method for preparing brown corundum using powdered bauxite has emerged. The general process is to first grind the bauxite uniformly, calcine it at high temperature, and then use alkali solution to leach and desiliconize it. After desiliconization, it needs to be agglomerated (lump), dried, calcined and dehydrated, and then smelted to produce brown corundum. The biggest drawback of this method is that the alkaline leaching desiliconization and the agglomerate (lump) calcination are two independent processes, each requiring separate heating and unable to be effectively connected. This leads to high energy consumption and low efficiency. The alkaline leaching desiliconization of the powdered ore must be carried out under stirring conditions, which increases equipment costs.

[0006] Therefore, the inventors of the present application have developed a calcination-desilication integrated tunnel kiln, which can preferably solve the above problems. After the powdered ore is agglomerated, it enters the kiln furnace, where desilication is completed in the calcination zone, and the silicon minerals are activated. After being forced to cool to a certain temperature in the cooling zone, desilication is carried out by spraying normal-temperature alkaline solution. Continuous production is conducive to the realization of intelligentization. The preheat generated in the cooling zone can be used for drying the desilicated ore (agglomerates), and the desilication alkaline solution can be recycled, saving costs and improving production efficiency. Summary of the Invention

[0007] The object of the present invention is to provide a calcination-desilication integrated tunnel kiln for producing brown corundum from bauxite. The equipment of the present invention can simultaneously achieve calcination and desilication. Especially when used in conjunction with a new process, it has the characteristics of high processing efficiency, more energy-saving and environmental protection, and lower desilication cost.

[0008] The technical solution of the present invention: A calcination-desilication integrated tunnel kiln for producing brown corundum from bauxite, which successively includes a preheating section, a roasting section, a cooling section and a spraying section from the kiln tail to the kiln head; a spraying pipe is provided above the spraying section, nozzles are provided on the spraying pipe, and one end of the spraying pipe extends out of the rotary kiln and is connected to an alkaline solution spraying device; a plurality of liquid leakage holes are provided on the kiln wall of the spraying section, and a liquid collecting tank is provided below the spraying section.

[0009] For the aforementioned calcination-desilication integrated tunnel kiln for producing brown corundum from bauxite, a liquid collecting jacket is provided outside the spraying section, and an open mouth is provided on one side of the liquid collecting jacket close to the kiln head.

[0010] For the aforementioned calcination-desilication integrated tunnel kiln for producing brown corundum from bauxite, the open mouth is a flared mouth, and the lowest end of the open mouth is located in the liquid collecting tank.

[0011] For the aforementioned calcination-desilication integrated tunnel kiln for producing brown corundum from bauxite, a drain pipe is connected to the bottom of the liquid collecting tank, and a drain valve is provided on the drain pipe.

[0012] The process of calcination using the above equipment includes the following steps:

[0013] 1) Grind the powdered bauxite evenly;

[0014] 2) Add water to the ore powder until it can be formed, and then press it into blocks to obtain Product A;

[0015] 3) First preheat Product A in the preheating section of the rotary kiln, and then transfer it to the roasting section for dehydration for 0.5 - 1.5 h to obtain Product B;

[0016] 4) Transfer Product B to the cooling section and cool it to 150 - 250 °C to obtain Product C;

[0017] 5) Then transfer it to the spraying section, and spray alkaline solution on Product C for desilication to obtain Product D;

[0018] 6) After dehydrating the D product again, it is subjected to conventional smelting to obtain brown corundum.

[0019] The lye sprayed in the spraying section can be recycled through the liquid collecting tank.

[0020] Advantages of the present invention

[0021] By sequentially arranging a preheating section, a roasting section, a cooling section and a spraying section, the block (agglomerate) bauxite can be desilicated after being preheated, roasted, cooled and sprayed in sequence. Compared with the traditional powder desilication equipment, the equipment of the present invention can simultaneously achieve the calcination and desilication of the block (agglomerate) bauxite, greatly improving the processing efficiency; in addition, since it is block (agglomerate) material, the lye and the bauxite will not be mixed together, but directly recycled from the liquid collecting tank below the spraying section, greatly shortening the processing time, improving the production efficiency, saving energy and protecting the environment. Especially, the powder ore with reduced grade is used for the production of brown corundum, broadening the range of raw material selection. Description of the drawings

[0022] Appendix Figure 1 It is a schematic structural diagram of the equipment of the present invention.

[0023] Description of the reference numerals in the drawings: 1 - preheating section, 2 - roasting section, 3 - cooling section, 4 - spraying section, 5 - spraying pipe, 6 - nozzle, 7 - liquid leakage hole, 8 - liquid collecting jacket, 9 - liquid collecting tank, 10 - open end, 11 - drain pipe, 12 - drain valve. Specific embodiments

[0024] The following further illustrates the present invention in conjunction with embodiments, but it shall not be used as a basis for limiting the present invention.

[0025] Embodiments of the present invention

[0026] A calcination-desilication integrated tunnel kiln for producing brown corundum from bauxite, as shown in the appendix Figure 1 shown, from the kiln tail to the kiln head are sequentially a preheating section 1, a roasting section 2, a cooling section 3 and a spraying section 4. The structures and working modes of the preheating section 1, the roasting section 2 and the cooling section 3 are the same as those of the traditional rotary kiln; the difference is that: a spraying pipe 5 is provided above the spraying section 4, and existing nozzles 6 are provided on the spraying pipe 5. One end of the spraying pipe 5 extends out of the rotary kiln and is connected to a lye spraying device. The lye spraying device includes a booster pump and a lye tank. The water outlet of the booster pump is connected to the spraying pipe 5, and the water inlet is connected to the lye tank; a plurality of liquid leakage holes 7 are provided on the kiln wall of the spraying section 4. The aperture of the liquid leakage holes 7 is much smaller than the size of the block bauxite, which can ensure that the desilication liquid can pass through. A liquid collecting tank 9 is provided below the spraying section 4.

[0027] Working principle: During use, first grind the powdered bauxite evenly according to the processing technology, then form it into blocks (agglomerates). Place the block (agglomerate) material in the preheating section 1 for preheating. After preheating, transfer it to the roasting section 2 for roasting. After roasting, transfer it to the cooling section 3 for cooling. Finally, transfer it to the spraying section 4. The lye is filled into the spraying pipe 5 through the lye spraying device, and then sprayed onto the block (agglomerate) material below through the nozzle 6 for desilication. After the lye spraying, it flows downward and is directly filtered out, and then leaks to the liquid collection tank 9 below through the liquid leakage hole 7 on the kiln wall. The silicon-containing liquid in the liquid collection tank can be reused after desilication.

[0028] Preferably, a liquid collection jacket 8 is provided outside the spraying section 4. An open mouth 10 is provided on one side of the liquid collection jacket 8 close to the kiln head. Since the rotary kiln itself has a certain inclination and the kiln head end is lower, the liquid collection jacket 8 can drain the leaked desilication liquid and discharge it into the liquid collection tank 9 through the open mouth 10 for recovery.

[0029] Preferably, the open mouth 10 is a trumpet-shaped mouth, and the lowest end of the open mouth 10 is located in the liquid collection tank 9, which is more conducive to the discharge of the desilication liquid and has a better collection effect.

[0030] Preferably, a drain pipe 11 is connected to the bottom of the liquid collection tank 9, and a drain valve 12 is provided on the drain pipe 11. When the desilication liquid in the liquid collection tank 9 is collected to a certain amount, it can be discharged for desilication treatment to realize the recycling of the lye.

Claims

1. A tunnel kiln for calcining and desiliconizing brown corundum from bauxite, characterized by: From the kiln tail to the kiln head, there are a preheating section (1), a roasting section (2), a cooling section (3) and a spraying section (4); a spraying pipe (5) is provided above the spraying section (4), and a nozzle (6) is provided on the spraying pipe (5); one end of the spraying pipe (5) extends out of the rotary kiln and is connected to the alkali solution spraying equipment; A plurality of liquid leakage holes (7) are provided on the kiln wall of the spray section (4), and a liquid collecting tank (9) is provided below the spray section (4); The outside of the spray section (4) is provided with a liquid collecting jacket (8), and the side of the liquid collecting jacket (8) close to the kiln head is provided with an opening (10); the rotary kiln itself has a certain inclination angle, and the kiln head end is lower; The structures and working modes of the preheating section (1), the roasting section (2), and the cooling section (3) are consistent with those of a traditional rotary kiln; The opening (10) is a bell-shaped opening, and the lowest end of the opening (10) is located in the liquid collecting tank (9); The bottom of the liquid collecting tank (9) is connected to a drain pipe (11), and a drain valve (12) is provided on the drain pipe (11); The material is cooled to 150-250°C after passing through the cooling section; The bauxite-to-brown corundum calcining-desiliconization integrated tunnel kiln is used for block or agglomerate bauxite. When in use, the powdered bauxite is first ground uniformly according to the processing technology, and then made into blocks (agglomerates). The blocks (agglomerates) are placed in a preheating section (1) for preheating. After preheating, they are transferred to a roasting section (2) for roasting. After roasting, they are transferred to a cooling section (3) for cooling. Finally, they are transferred to a spraying section (4). Alkali liquid is filled into a spray pipe (5) through an alkali liquid spraying device, and then sprayed to the block (agglomerate) below through a nozzle (6) for desiliconization. After spraying, the alkali liquid flows downward and is directly filtered out. Then, it leaks into a liquid collecting tank (9) below through a liquid leakage hole (7) on the kiln wall. The silicon-containing liquid in the liquid collecting tank can be reused after desiliconization.

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