Aluminum oxide production and wastewater treatment device and aluminum oxide preparation process

Abstract

The invention relates to the technical field of chemical engineering and environmental protection. The aluminum oxide production and wastewater treatment device comprises a reaction tank group and a wastewater treatment tank group arranged on one side of the reaction tank group, the reaction tank group comprises a reaction tank and a hydrochloric acid evaporation tank which are arranged up and down, and an inert gas storage tank arranged on one side of the hydrochloric acid evaporation tank; a hydrochloric acid heater and an ejector are arranged in the hydrochloric acid evaporation tank, a main gas inlet of the ejector is connected with an outlet of the jet pump through a connecting pipe, and an inlet of the jet pump is connected with an outlet of the inert gas storage tank; a gas distribution pipe is arranged at the center in the reaction tank, and a gas outlet of the ejector is communicated with the gas distribution pipe; a liquid inlet pipe for injecting a sodium metaaluminate solution is arranged at the upper part of the reaction tank, and a discharge pipe for discharging precipitates is arranged at the lower part of the reaction tank; a liquid discharge pipe is also arranged on the side wall of the middle section of the reaction tank, and the reaction tank is communicated with the wastewater treatment tank group through the liquid discharge pipe. On the basis of accurately mastering the dosage of hydrochloric acid, the reaction speed and efficiency are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical industry and environmental protection, and in particular to an alumina production and wastewater treatment device and an alumina preparation process. Background Art

[0002] The preparation and purification process for high-purity alumina involves mixing sodium hydroxide and aluminum hydroxide to produce a sodium aluminate solution, as shown in the reaction equation: Al(OH)3 + NaOH = NaAlO2 + 2H2O. Hydrochloric acid is then added to the sodium aluminate solution to produce an aluminum hydroxide precipitate and sodium chloride, as shown in the reaction equation: NaAlO2 + HCl + H2O = Al(OH)3↓ + NaCl. The precipitate is then filtered, separated, and washed with distilled water to obtain pure aluminum hydroxide. Finally, high-temperature pyrolysis yields high-purity alumina. However, the amount of hydrochloric acid used must be carefully monitored during this process. If an excess of hydrochloric acid is added, the aluminum hydroxide precipitate will react with the excess hydrochloric acid to form AlCl3.

[0003] Currently, existing production equipment suffers from the following major issues: It's difficult to precisely control the amount of hydrochloric acid added to the sodium aluminate solution. To ensure the reaction proceeds according to the intended route, production speed often needs to be strictly controlled, resulting in low overall production efficiency. Furthermore, since residual hydrochloric acid inevitably remains in the entire reaction system, improperly handling this hydrochloric acid wastewater can also pose significant environmental risks. Summary of the Invention

[0004] The object of the present invention is to provide an alumina production and wastewater treatment device that can accurately control the amount of hydrochloric acid used and improve production efficiency.

[0005] To achieve the above-mentioned object, the technical solution adopted by the present invention is: an alumina production and wastewater treatment device, comprising a reaction tank group and a wastewater treatment tank group arranged on one side of the reaction tank group;

[0006] The reaction tank group includes a reaction tank and a hydrochloric acid evaporation tank arranged up and down, and an inert gas storage tank arranged on one side of the hydrochloric acid evaporation tank;

[0007] The hydrochloric acid evaporator is provided with a hydrochloric acid heater and an ejector, the main air inlet of the ejector is connected to the outlet of the ejector pump through a connecting pipe, and the inlet of the ejector pump is connected to the outlet of the inert gas storage tank; a gas distribution pipe is provided in the center of the reaction tank, and the air outlet of the ejector is connected to the gas distribution pipe; the upper part of the reaction tank is provided with a liquid inlet pipe for injecting sodium aluminate solution, and the lower part is provided with a discharge pipe for discharging sediment; a discharge pipe is also provided on the side wall of the middle section of the reaction tank, and is connected to the wastewater treatment tank group through the discharge pipe.

[0008] Preferably, the gas distribution pipe includes a central pipe vertically arranged in the center of the reaction tank, and a plurality of groups of gas distribution branches are evenly arranged on the side wall of the central pipe from top to bottom.

[0009] Preferably, the lumen of the central tube is in a spiral shape that rises vertically; a check valve that is connected in one direction from bottom to top is provided at the lower end of the central tube.

[0010] Preferably, a stirring drum is further provided in the reaction tank, the upper end of the stirring drum is connected to a stirring motor fixedly provided on the top of the reaction tank, the stirring drum is sleeved outside the gas distribution pipe, and the lower end forms a rotational fit with the bottom of the reaction tank.

[0011] Preferably, the mixing drum includes two end plates arranged upper and lower, and a drum body arranged between the end plates; the drum body is composed of a number of alternately arranged fixed drum plates and movable drum plates; the upper and lower ends of the fixed drum plates are fixedly connected to the end plates, and the upper and lower ends of the movable drum plates are provided with rotating pins, and are rotated together with the end plates through the rotating pins; when the mixing drum rotates in the forward direction, the movable drum plate can swing to abut against the fixed drum plate to form a closed drum body; when the mixing drum rotates in the reverse direction, the movable drum plate can rotate around the center of the rotating pin to open the gap between adjacent fixed drum plates.

[0012] Preferably, a first step is provided on one side of the fixed cylinder plate, and a second step is provided on the other end; a third step cooperating with the first step, and a fourth step cooperating with the second step are provided on the movable cylinder plate; the third step is bent inward to form an inner folding edge; a limit block is provided on the end plate on the outer side of the movable cylinder plate to prevent the movable cylinder plate from excessive rotation.

[0013] Preferably, a plurality of drain pipes are provided on the side of the reaction tank from top to bottom.

[0014] Preferably, the wastewater treatment tank group includes a wastewater evaporation tank, a condensation tank and an alkali solution treatment tank arranged in sequence from bottom to top and interconnected, the drain pipe of the reaction tank is connected to the wastewater evaporation tank; a wastewater heater is provided in the wastewater evaporation tank; the drain end of the lower part of the condensation tank is connected to the hydrochloric acid recovery tank.

[0015] Preferably, the top of the reaction tank is connected to the condensation tank through an exhaust pipe.

[0016] Preferably, the alumina preparation process comprises the following steps:

[0017] A. Preparation of sodium metaaluminate solution;

[0018] B. Preparation of aluminum hydroxide: heating hydrochloric acid to generate hydrochloric acid vapor, fully dispersing the hydrochloric acid vapor in inert gas nitrogen to form a mixed gas, and passing the mixed gas into sodium metaaluminate solution for reaction;

[0019] C. Filtration and washing of the precipitate: After the reaction is completed, the reaction solution is filtered to separate the aluminum hydroxide precipitate and the wastewater solution, the aluminum hydroxide precipitate is washed several times, and the wastewater solution and the washing water are combined and distilled; after separating the hydrochloric acid, the tail gas is passed through an alkaline solution for neutralization treatment before discharge;

[0020] D. Thermal decomposition of aluminum hydroxide to produce aluminum oxide: Aluminum hydroxide precipitate is heated and decomposed to produce aluminum oxide.

[0021] The beneficial effects of the present invention are concentrated in: on the basis of accurately grasping the amount of hydrochloric acid used, the reaction speed and efficiency are improved. Specifically, during use, the present invention first uses the hydrochloric acid heater in the hydrochloric acid evaporator to heat the hydrochloric acid to prepare hydrochloric acid vapor; the nitrogen in the inert gas storage tank is ejected to the hydrochloric acid vapor through the ejector, and a mixed gas of nitrogen and hydrochloric acid vapor is formed to mix and dilute the hydrochloric acid vapor; by changing the amount of the mixed gas introduced, the amount of hydrochloric acid used can be effectively controlled; and because the hydrochloric acid gas is carried out by using the inert gas nitrogen as a gas carrier, the mixed gas and the sodium aluminate solution can be quickly mixed, which can greatly improve the overall reaction speed and ensure the normal progress of the reaction. On the basis of ensuring the accuracy of the reaction control, the overall reaction efficiency is greatly improved, and there is basically no side reaction of excessive local hydrochloric acid. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a structural schematic diagram of the present invention;

[0023] Figure 2 is a schematic cross-sectional view of the mixing drum;

[0024] Figure 3 for Figure 2 The structure shown in FIG is a schematic diagram of a usage state. DETAILED DESCRIPTION

[0025] like Figure 1-3 As shown in , the present invention discloses an alumina preparation process involving alumina production and wastewater treatment, which is used to prepare high-purity alumina. The overall steps are as follows:

[0026] First, the sodium aluminate solution is prepared. It is feasible to prepare the sodium aluminate solution using traditional low-purity aluminum oxide + sodium hydroxide solution; or to prepare the sodium aluminate solution using low-purity aluminum hydroxide + sodium hydroxide solution. Since the method involved in this step is a conventional operation method in this industry, it will not be described separately in the present invention.

[0027] The second is the preparation of aluminum hydroxide: This method changes the traditional method of adding hydrochloric acid to the sodium aluminate solution. Instead, the hydrochloric acid is first heated to generate hydrochloric acid vapor, which is fully dispersed in the inert gas nitrogen to form a mixed gas. The mixed gas is then passed into the sodium aluminate solution for reaction. Using inert gas nitrogen as a carrier gas improves the dispersion of hydrochloric acid. Nitrogen has extremely stable chemical properties and can play a nitrogen protection role throughout the reaction process. It can also act as a carrier for hydrochloric acid vapor, facilitating precise control of the amount of hydrochloric acid.

[0028] Next, the precipitate is filtered and washed. After the reaction is complete, the reaction solution is filtered to separate the aluminum hydroxide precipitate and the wastewater solution. The aluminum hydroxide precipitate needs to be washed multiple times to isolate the pure aluminum hydroxide precipitate. Regarding the treatment of the wastewater solution, the wastewater solution and washing water are combined and distilled (the solution is first heated and then condensed). This separates the hydrochloric acid, which is recovered and purified for subsequent use. This removes the hydrochloric acid from the wastewater solution, which is energy-saving and environmentally friendly. The remaining exhaust gas is neutralized with alkaline solution before being discharged, completely removing the HCl gas contained in the exhaust gas.

[0029] Finally, aluminum hydroxide is thermally decomposed to produce aluminum oxide: This step uses traditional technology to heat and decompose the aluminum hydroxide precipitate to produce high-purity aluminum oxide.

[0030] To achieve the above process steps, the present invention simultaneously discloses an alumina production and wastewater treatment device, which generally includes a reaction tank group and a wastewater treatment tank group arranged on one side of the reaction tank group. The wastewater treatment tank group is used to perform subsequent treatment on the wastewater solution after the reaction is completed.

[0031] like Figure 1 As shown in the figure, the reaction tank group is mainly used as the reaction site for the sodium metaaluminate solution and hydrochloric acid. The reaction tank group includes a reaction tank 1 and a hydrochloric acid evaporator 2 arranged vertically, and an inert gas storage tank 3 provided on one side of the hydrochloric acid evaporator 2. The reaction takes place in the reaction tank 1, the hydrochloric acid evaporator 2 is used to heat the hydrochloric acid inside to produce HCl gas, and the inert gas storage tank 3 is used to store nitrogen.

[0032] The hydrochloric acid evaporator 2 of the present invention is equipped with a hydrochloric acid heater 4 and an ejector 5. The hydrochloric acid heater 4 is used to heat and generate HCl gas. The ejector 5's main air inlet is connected to the outlet of an ejector pump 7 via a connecting pipe 6. Since the ejector 5 is integrally disposed within the hydrochloric acid evaporator 2, its secondary air inlet (inlet) directly communicates with the interior of the hydrochloric acid evaporator 2, allowing HCl gas to enter the ejector 5. (The structure of the ejector 5 is conventional in the prior art and will not be described in detail here.) The inlet of the ejector pump 7 is connected to the outlet of the inert gas storage tank 3. When activated, the ejector pump 7 draws nitrogen from the inert gas storage tank 3, accelerates it, and feeds it into the ejector 5, where the nitrogen and HCl gases are mixed and ejected.

[0033] A gas distribution pipe is provided in the center of the reaction tank 1, and the gas outlet of the ejector 5 is connected to the gas distribution pipe. The function of the gas distribution pipe is to evenly distribute the mixed gas to various locations inside the reaction tank 1 (reaction zone). Figure 1 and 2 As shown in , the gas distribution pipe includes a central tube 11 vertically arranged in the center of the reaction tank 1, and a plurality of groups of gas distribution branches 12 are evenly arranged on the side walls of the central tube 11 from top to bottom. The mixed gas ejected by the ejector 5 passes through the central tube 11 and enters the gas distribution branch 12, and is then distributed to various areas in the reaction tank 1 through the gas distribution branch 12. In order to further enhance the mixing effect of HCl gas and nitrogen, the lumen of the central tube 11 is in a spiral shape that rises vertically, and the gas spirally rises in the central tube 11 and forms a secondary mixing. The lower end of the central tube 11 is provided with a one-way check valve connected from bottom to top to prevent the internal liquid from being re-injected when the gas pressure is insufficient.

[0034] The upper part of the reactor 1 of the present invention is provided with an inlet pipe 8 for injecting sodium aluminate solution, and the lower part is provided with a discharge pipe 9 for discharging precipitates. A drain pipe 10 is also provided on the side wall of the middle section of the reactor 1, and is connected to the wastewater treatment tank group through the drain pipe 10. Before the reaction, the sodium aluminate solution is first injected through the inlet pipe 8 and reacts with the mixed gas containing HCl gas from the gas distribution pipe. After the reaction is completed, the generated aluminum hydroxide precipitate can be discharged from the discharge pipe 9 and enter the subsequent filtering and washing device, while the wastewater solution is discharged from the drain pipe 10 to the wastewater treatment tank group. When discharging the wastewater solution, it is best to choose a form of gradual discharge from top to bottom. For this purpose, a better approach can also be to have multiple drain pipes 10 on the side of the reactor 1 from top to bottom. When discharging, discharge is achieved by opening each drain pipe 10 one by one from top to bottom.

[0035] During the reaction process of the present invention, on the one hand, the reaction speed can be further increased by stirring. On the other hand, in order to prevent the generated aluminum hydroxide precipitate from reacting again with the HCl gas (equivalent to excessive hydrochloric acid), the aluminum hydroxide precipitate should be kept as far away from the source of the HCl gas (gas distribution pipe) as possible, that is, it has a certain isolation function.

[0036] Therefore, a better solution of the device is to combine Figure 1-3 As shown in FIG, the reactor 1 is further provided with a stirring drum 13. The upper end of the stirring drum 13 is connected to a stirring motor 14 fixedly provided on the top of the reactor 1. The stirring drum 13 is sleeved outside the gas distribution pipe, and the lower end is in rotational engagement with the bottom of the reactor 1. The rapid rotation of the stirring drum 13 can increase the reaction speed in the reactor 1. At the same time, the present invention also realizes the aforementioned isolation function through the special design of the stirring drum 13, which is specifically as follows:

[0037] Combine Figure 2 and 3 As shown, the mixing drum 13 includes two end plates 15 arranged in an upper and lower position, and a drum body arranged between the end plates 15. The drum body is composed of a plurality of fixed drum plates 16 and movable drum plates 17 arranged alternately. The upper and lower ends of the fixed drum plates 16 are fixedly connected to the end plates 15, and the upper and lower ends of the movable drum plates 17 are provided with rotating pins 18, and the movable drum plates 17 are rotated together with the end plates 15 through the rotating pins 18. When the mixing drum 13 rotates in the forward direction, as shown in FIG. Figure 2 As shown, the movable cylinder plate 17 can swing to abut against the fixed cylinder plate 16 to form a closed cylinder. Figure 3 As shown, the movable cylinder plate 17 can rotate around the center of the rotating pin 18 to open the gap between the adjacent fixed cylinder plates 16. Under this structure, in the initial stage of the reaction, the mixing drum 13 adopts Figure 2 In the form of forward rotation, the sodium aluminate solution inside the mixing drum 13 can fully react with the mixed gas; and in the later stage of stirring, as the aluminum hydroxide precipitate is precipitated, the mixing drum 13 can be rotated in the reverse direction to form a simple centrifugal drum. The aluminum hydroxide precipitate can be quickly discharged from the gap between the fixed drum plates 16 to the outside of the mixing drum 13 under rotation to complete sedimentation.

[0038] In order to further ensure the functionality of the movable barrel plate 17 and the fixed barrel plate 16, a first step 19 is provided on one side of the fixed barrel plate 16, and a second step 20 is provided on the other end. The movable barrel plate 17 is provided with a third step 21 that cooperates with the first step 19, and a fourth step 22 that cooperates with the second step 20. The third step 21 is bent inward to form an inner folding edge 23. A limit block 24 is provided on the end plate 15 outside the movable barrel plate 17 to prevent the movable barrel plate 17 from excessively rotating. The existence of the inner folding edge 23 can, on the one hand, prevent the mixing drum 13 from rotating forward (such as Figure 2 As shown), it acts as a stirring paddle to promote material mixing. On the other hand, when it rotates in the opposite direction (as shown Figure 3 As shown in FIG, the inner folding edge 23 can also serve as a driving force for the movable cylindrical plate 17 to improve its smoothness of opening, while the limit block 24 is to prevent the movable cylindrical plate 17 from turning over too large an angle.

[0039] In wastewater treatment, such as Figure 1 As shown, the wastewater treatment tank assembly of the apparatus of the present invention includes, arranged sequentially from bottom to top and interconnected, a wastewater evaporation tank 25, a condensation tank 26, and an alkali solution treatment tank 27. The drain pipe 10 of the reactor 1 is connected to the wastewater evaporation tank 25. A wastewater heater 28 is provided within the wastewater evaporation tank 25. The lower drain port of the condensation tank 26 is connected to a hydrochloric acid recovery tank. During the entire reaction, as the mixed gas is continuously introduced, the pressure within the reactor 1 gradually rises. During this period, nitrogen, which does not react, gradually accumulates at the top of the reactor 1 after cutting through the liquid and delivering the HCl gas, causing the pressure to rise. This nitrogen gas needs to be discharged regularly, but inevitably carries over a certain amount of HCl gas, which is not suitable for direct discharge. Therefore, the top of the reactor 1 is connected to the condensation tank 26 via an exhaust pipe.

Claims

1. An alumina production and wastewater treatment plant, characterized in that: It includes a reaction tank group and a wastewater treatment tank group arranged on one side of the reaction tank group; The reaction tank group comprises a reaction tank (1) and a hydrochloric acid evaporation tank (2) arranged vertically, and an inert gas storage tank (3) arranged on one side of the hydrochloric acid evaporation tank (2); The hydrochloric acid evaporation tank (2) is provided with a hydrochloric acid heater (4) and an ejector (5), the main air inlet of the ejector (5) is connected to the outlet of the ejector pump (7) through a connecting pipe (6), and the inlet of the ejector pump (7) is connected to the outlet of the inert gas storage tank (3); a gas distribution pipe is provided in the center of the reaction tank (1), and the air outlet of the ejector (5) is connected to the gas distribution pipe; the upper part of the reaction tank (1) is provided with a liquid inlet pipe (8) for injecting sodium aluminate solution, and the lower part is provided with a discharge pipe (9) for discharging sediment; a discharge pipe (10) is also provided on the side wall of the middle section of the reaction tank (1), and is connected to the wastewater treatment tank group through the discharge pipe (10).

2. The alumina production and wastewater treatment device according to claim 1, characterized in that: The gas distribution pipe comprises a central pipe (11) vertically arranged in the center of the reaction tank (1), and a plurality of groups of gas distribution branch pipes (12) are evenly arranged on the side wall of the central pipe (11) from top to bottom.

3. The alumina production and wastewater treatment plant according to claim 2, characterized in that: The lumen of the central tube (11) is in a spiral shape that rises vertically; a check valve that is connected in one direction from bottom to top is provided at the lower end of the central tube (11).

4. The alumina production and wastewater treatment plant according to claim 3, characterized in that: A stirring drum (13) is further provided in the reaction tank (1). The upper end of the stirring drum (13) is connected to a stirring motor (14) fixedly provided on the top of the reaction tank (1). The stirring drum (13) is sleeved outside the gas distribution pipe, and the lower end thereof is in rotational engagement with the bottom of the reaction tank (1).

5. The alumina production and wastewater treatment plant according to claim 4, characterized in that: The mixing drum (13) includes two end plates (15) arranged in an upper and lower direction, and a drum body arranged between the end plates (15); the drum body is composed of a plurality of fixed drum plates (16) and movable drum plates (17) arranged alternately; the upper and lower ends of the fixed drum plates (16) are fixedly connected to the end plates (15), and the upper and lower ends of the movable drum plates (17) are provided with rotating pins (18), and the movable drum plates (17) are rotated with the end plates (15) through the rotating pins (18); when the mixing drum (13) rotates in the forward direction, the movable drum plates (17) can swing to abut against the fixed drum plates (16) to form a closed drum body; when the mixing drum (13) rotates in the reverse direction, the movable drum plates (17) can rotate around the center of the rotating pins (18) to open the gap between adjacent fixed drum plates (16).

6. The alumina production and wastewater treatment plant according to claim 5, characterized in that: A first step (19) is provided on one side of the fixed cylinder plate (16), and a second step (20) is provided on the other end; a third step (21) is provided on the movable cylinder plate (17) to match the first step (19), and a fourth step (22) is provided on the movable cylinder plate (17); the third step (21) is bent inward to form an inner folding edge (23); and a limit block (24) is provided on the end plate (15) outside the movable cylinder plate (17) to prevent the movable cylinder plate (17) from excessive rotation.

7. The alumina production and wastewater treatment plant according to claim 6, characterized in that: A plurality of drainage pipes (10) are provided on the side of the reaction tank (1) from top to bottom.

8. The alumina production and wastewater treatment plant according to claim 7, characterized in that: The wastewater treatment tank group comprises a wastewater evaporation tank (25), a condensation tank (26) and an alkali solution treatment tank (27) arranged in sequence from bottom to top and interconnected. The discharge pipe (10) of the reaction tank (1) is connected to the wastewater evaporation tank (25); a wastewater heater (28) is provided in the wastewater evaporation tank (25); and the discharge end of the lower portion of the condensation tank (26) is connected to a hydrochloric acid recovery tank.

9. The alumina production and wastewater treatment plant according to claim 8, characterized in that: The top of the reaction tank (1) is connected to the condensation tank (26) through an exhaust pipe.

10. A process for preparing alumina using the alumina production and wastewater treatment device according to any one of claims 1 to 9, characterized in that: The following steps are involved: A. Preparation of sodium metaaluminate solution; B. Preparation of aluminum hydroxide: heating hydrochloric acid to generate hydrochloric acid vapor, fully dispersing the hydrochloric acid vapor in inert gas nitrogen to form a mixed gas, and passing the mixed gas into sodium metaaluminate solution for reaction; C. Filtration and washing of the precipitate: After the reaction is completed, the reaction solution is filtered to separate the aluminum hydroxide precipitate and the wastewater solution, the aluminum hydroxide precipitate is washed several times, and the wastewater solution and the washing water are combined and distilled; After the hydrochloric acid is separated, the tail gas is passed through alkaline solution for neutralization and then discharged; D. Thermal decomposition of aluminum hydroxide to produce aluminum oxide: Aluminum hydroxide precipitate is heated and decomposed to produce aluminum oxide.

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