Production device of dry aluminum hydroxide

Abstract

The invention provides a production device of dry aluminum hydroxide, and relates to the technical field of flue gas waste heat. Comprising a control system, a material distributing system, a screening system, a cooling system and a packaging system, the material distributing system is used for intercepting dry aluminum hydroxide dried by flue gas waste heat to obtain graded raw materials, the screening system is used for grading the graded raw materials to obtain qualified oversize materials and unqualified oversize materials, the cooling system is used for cooling the qualified oversize materials to obtain cooled oversize materials, and the discharging system is used for discharging the cooled oversize materials. The packaging system is used for packaging the qualified screen loading materials, and the control system is used for regulating and controlling operation parameters of the material distributing system, the screening system, the cooling system and the packaging system. The problems of high energy consumption loss and low energy utilization rate caused by the flue gas waste heat utilization rate in the aluminum oxide production process in the prior art are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of flue gas waste heat, and particularly to a production device for dry aluminum hydroxide. Background Art

[0002] At present, the metallurgical-grade aluminum hydroxide sold on the market is mainly the primary wet aluminum hydroxide produced by the flat plate filter of the Bayer process, with a water content (adherent water) of about 3-5%, and the particle size fluctuates greatly, and the product quality stability is poor.

[0003] Aluminum fluoride [AlF 3 enterprises are one of the main customers of aluminum hydroxide. In the dry process of producing aluminum fluoride, the requirements for water content (adherent water) are ≤ 3%, the particle size -45μm ≤ 5%, and for dry aluminum hydroxide, the adherent water is required to be ≤ 0.1%, the specific gravity > 1.22, and the appearance is white powder or sand-like crystals. If the particle size of aluminum hydroxide is too fine, it is easy to block the aluminum fluoride production system. Moreover, its physical properties not only affect the appearance of the finished product, but also affect the unit consumption of the product. Therefore, the control of the quality index of aluminum hydroxide is a key link in the production process of dry aluminum fluoride.

[0004] Therefore, the deficiencies of the existing technology are as follows: In the existing technology, water is mostly used as the heat exchange medium for the waste heat of the roasting furnace flue gas, but the effect of maximizing the utilization of the flue gas waste heat cannot be achieved. In this technology, the flue gas waste heat is directly used to heat the material, reducing the intermediate energy consumption loss and having a higher energy utilization rate. Summary of the Invention

[0005] In order to overcome the deficiencies of the existing technology, the purpose of the present invention is to provide a production device for dry aluminum hydroxide.

[0006] To achieve the above purpose, the present invention provides the following solution:

[0007] A production device for dry aluminum hydroxide, comprising:

[0008] A control system and a feeding system, a screening system, a cooling system, and a packaging system all connected to the control system. The feeding system, the screening system, the cooling system, and the packaging system are sequentially connected section by section using pipelines;

[0009] The feeding system is used to intercept the dry aluminum hydroxide after being dried by the flue gas waste heat to obtain classified raw materials. The screening system classifies the classified raw materials to obtain qualified oversize materials and unqualified undersize materials. The cooling system is used to cool the qualified oversize materials to obtain the cooled oversize materials. The packaging system is used to package the qualified oversize materials. The control system is used to regulate the operating parameters of the feeding system, the screening system, the cooling system, and the packaging system.

[0010] Preferably, the feeding system includes:

[0011] Blank-off tee, material seal, pneumatic slide valve, tubular screw conveyor, small bunker;

[0012] The blank-off tee is used to flow the dry aluminum hydroxide after being dried by the waste heat of the flue gas to the material seal. The material seal seals and maintains a constant pressure for the roasting furnace. The pneumatic slide valve is used to isolate the dry aluminum hydroxide during equipment maintenance. The tubular screw conveyor is used to convey the dry aluminum hydroxide in the material seal to the small bunker for storage to obtain classified raw materials.

[0013] Preferably, the screening system includes:

[0014] Rotary valve, multi-layer vibrating screen, material seal pump, chute;

[0015] The rotary valve is used to control the feeding amount of the classified raw materials. The multi-layer vibrating screen is used to adopt a combination of planar circular motion and parabolic motion to obtain qualified oversize materials and unqualified undersize materials. The material seal pump is used to use high-pressure gas to return the unqualified undersize materials to the roasting furnace. The chute is used to convey the qualified oversize materials to the cooling system.

[0016] Preferably, the cooling system includes:

[0017] Fluidized bed and large bunker;

[0018] The fluidized bed is used to cool the qualified oversize materials with circulating water to obtain cooled oversize materials. The large bunker is used to store the cooled oversize materials.

[0019] Preferably, the packaging system includes:

[0020] Packaging machine, chain conveyor, dust collector;

[0021] The chain conveyor is used to orderly convey the materials or packaging products that need to be moved or conveyed before and after packaging. The dust collector is used to collect and purify the dust generated during the packaging process. The packaging machine is used to automatically or semi-automatically pack the qualified and cooled dry aluminum hydroxide in the large bunker.

[0022] The present invention discloses the following technical effects:

[0023] The present invention provides a production device for dry aluminum hydroxide, comprising: a control system, a material distribution system, a screening system, a cooling system, and a packaging system, all of which are connected to the control system; the material distribution system is used to intercept the dry aluminum hydroxide after drying with the waste heat of the flue gas to obtain classified raw materials, the screening system classifies the classified raw materials to obtain qualified oversize materials and unqualified undersize materials, the cooling system is used to cool the qualified oversize materials to obtain the cooled oversize materials, the packaging system is used to package the qualified oversize materials, and the control system is used to regulate the operating parameters of the material distribution system, the screening system, the cooling system, and the packaging system. The present invention combines the waste heat drying of the preheating cyclone with the material distribution system to reduce energy consumption. And by using a multi-layer vibrating screen combined with an ultrasonic screen cleaning method, the production capacity and accuracy are greatly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0025] Figure 1 FIG. is a schematic structural diagram of a production device for dry aluminum hydroxide provided by an embodiment of the present invention;

[0026] Figure 2 FIG. is a schematic detail diagram of a production device for dry aluminum hydroxide provided by an embodiment of the present invention;

[0027] Figure 3 FIG. is a schematic process diagram of a production process for dry aluminum hydroxide provided by an embodiment of the present invention.

[0028] Description of the reference numerals:

[0029] 1 - control system, 2 - material distribution system, 3 - screening system, 4 - cooling system, 5 - packaging system. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0031] In order to make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the drawings and specific embodiments.

[0032] As Figure 1 shown, the present invention provides a production device for dry aluminum hydroxide, comprising:

[0033] A control system 1 and a material distribution system 2, a screening system 3, a cooling system 4, and a packaging system 5 all connected to the control system 1. The entire system utilizes the gravity flow of dry aluminum hydroxide and is connected section by section using pipelines;

[0034] The material distribution system 2 is used to intercept dry aluminum hydroxide after drying with flue gas waste heat to obtain classified raw materials. The screening system 3 classifies the classified raw materials to obtain qualified oversize materials and unqualified undersize materials. The cooling system 4 is used to cool the qualified oversize materials to obtain cooled oversize materials. The packaging system 5 is used to package the qualified oversize materials. The control system 1 is used to regulate the operating parameters of the material distribution system 2, the screening system 3, the cooling system 4, and the packaging system 5.

[0035] Furthermore, the material distribution system 2 includes:

[0036] A blanking tee, a stuffing box, a pneumatic slide valve, a tubular screw conveyor, and a small storage bin;

[0037] The blanking tee is used to flow dry aluminum hydroxide after drying with flue gas waste heat to the stuffing box. The stuffing box seals and maintains a constant pressure for the roasting furnace. The pneumatic slide valve is used to isolate dry aluminum hydroxide during equipment maintenance. The tubular screw conveyor is used to convey the dry aluminum hydroxide in the stuffing box to the small storage bin for storage to obtain classified raw materials.

[0038] Specifically, the material distribution system 2 includes a blanking tee, a stuffing box, a pneumatic slide valve, a tubular screw conveyor, and a small storage bin from top to bottom in the preheating cyclone discharge pipe. Its function is to be responsible for intercepting dry aluminum hydroxide after drying with flue gas waste heat as screening raw materials. Under the action of gravity, the dried dry aluminum hydroxide flows from the blanking tee to the stuffing box. The stuffing box seals and maintains a constant pressure for the roasting furnace. The pneumatic slide valve isolates the material. The tubular screw conveys the material to the small storage bin for temporary storage, and the conveying volume is controlled by variable frequency speed regulation

[0039] Furthermore, the screening system 3 includes:

[0040] A star-shaped blanking valve, a multi-layer vibrating screen, a stuffing box pump, and a chute;

[0041] The star-shaped blanking valve is used to control the feeding volume of the classified raw materials. The multi-layer vibrating screen is used to combine planar circular motion and parabolic motion to obtain qualified oversize materials and unqualified undersize materials. The stuffing box pump is used to use high-pressure gas to return the unqualified undersize materials to the roasting furnace. The chute is used to convey the qualified oversize materials to the cooling system 4.

[0042] Specifically, the function of the screening system 3 is to receive the materials from the material distribution system 2. The qualified oversize materials are sent to the fluidized bed for cooling through a chute, and the unqualified undersize materials are returned to the roasting furnace using a pneumatic conveying pump. The star feeder obtains the required feeding volume through variable frequency speed regulation, and adjusts the feeding volume of the vibrating screen according to the rotation speed of the valve core.

[0043] The multi-layer vibrating screen is by far the most effective screening machine that mimics human manual actions and processes. Its unique design structure combines screening (planar circular motion) and winnowing (upward parabolic motion) skillfully. By adjusting the radial angle and tangential angle, the screening effect can reach the best state you require. The adjustment of the radial angle and tangential angle of the multi-layer vibrating screen causes the materials to move in an involute shape on the screen mesh. This movement trajectory enables the materials to travel a relatively long distance on a relatively small area to improve the screening accuracy. The unique design makes the dwelling time of the materials on the screen longer compared to other screening machines. At the same time, the ultrasonic system is superimposed for screen cleaning to increase the screening output. The pneumatic conveying pump uses high-pressure gas for pneumatic conveying of the materials. The chute is mainly responsible for guiding the materials screened on the 48m plane down to the fluidized bed.

[0044] Furthermore, the cooling system 4 includes:

[0045] A fluidized bed and a large bin;

[0046] The fluidized bed is used to cool the qualified oversize materials with circulating water to obtain the cooled oversize materials, and the large bin is used to store the cooled oversize materials.

[0047] Specifically, the cooling system 4 includes a fluidized bed and a large bin. The qualified dry aluminum hydroxide is cooled in the fluidized bed and temporarily stored in the large bin. Its function is to use circulating water as a refrigerant to cool the dry aluminum hydroxide from 150°C to 70°C.

[0048] Furthermore, the packaging system 5 includes:

[0049] A packaging machine, a chain conveyor, and a dust collector;

[0050] The chain conveyor is used to orderly convey the materials or packaged products that need to be moved or transported before and after packaging. The dust collector is used to collect and purify the dust generated during the packaging process. The packaging machine is used to automatically or semi-automatically pack the qualified and cooled dry aluminum hydroxide in the large bin.

[0051] Specifically, the control system includes: a tuning fork level gauge for the large bin, a weighing system for the small bin, a thermometer for the fluidized bed discharge, a thermometer for the circulating water, a diverter slide valve, a tubular screw variable frequency speed controller, a star valve for the vibrating screen, and a regulating valve for the circulating water. Among them, the tuning fork level gauge for the large bin: is used to monitor the liquid level of the large bin in real time. When the liquid level reaches the set high or low points, the sensor will send a feedback signal to the control system to achieve automatic control.

[0052] The weighing system for the small bin: monitors the weight of the materials in the small bin in real time through an accurate weighing system to judge the material distribution and production progress, and performs corresponding operations when the set value is reached. The thermometer for the fluidized bed discharge: ensures that the discharge temperature is within a reasonable range to prevent impacts on subsequent processing due to excessive temperature. The thermometer for the circulating water: monitors the temperature change of the circulating water to ensure the effective operation of the cooling system. The diverter slide valve: controls the material distribution flow of dry aluminum hydroxide according to the feedback of the operating conditions to meet the system load requirements and ensure the continuity of production. The tubular screw variable frequency speed controller: uses variable frequency speed control technology to adjust the rotation speed of the screw conveyor, balance the weight of the small bin, and ensure continuous and uniform material flow. The star valve for the vibrating screen: is responsible for adjusting the amount of materials flowing into the vibrating screen to optimize production capacity and the best screening rate and improve screening efficiency. The regulating valve for the circulating water: automatically adjusts the flow rate of the circulating water according to the change in the fluidized bed discharge temperature to maintain the cooling effect of the system and ensure the stability of the production process.

[0053] More specifically, the control system achieves the following control objectives:

[0054] Monitoring the liquid level of the large bin: The liquid level of the large bin is monitored by the level gauge. If the liquid level reaches the set full bin state, the control system will automatically close the diverter slide valve and pause the operation of the entire system to prevent overflow or production chaos.

[0055] Balancing the weight of the small bin: The weight change of the small bin will be fed back to the variable frequency speed controller, and the balance and timely replenishment of materials are achieved by regulating the rotation speed of the tubular screw, thus maintaining the stable flow of the production line.

[0056] Screening adjustment: The star valve adjusts the amount of materials entering the vibrating screen according to real-time data to ensure that the production capacity of the vibrating screen is within the best working range to achieve the highest screening efficiency.

[0057] Controlling the flow rate of the circulating water: According to the discharge temperature of the fluidized bed, the regulating valve for the circulating water will automatically adjust the water flow rate to ensure the cooling efficiency, prevent overheating of the discharge, and protect the equipment and product quality.

[0058] Judging the balance of system operation: The liquid level of the large bin and the weight feedback of the small bin are the main judgment bases for the balance of system operation. Through real-time monitoring and feedback adjustment, the material balance and stable operation during the production process are ensured.

[0059] Furthermore, as Figures 2 - 3 shown, this embodiment discloses a specific working process:

[0060] A bypass pipe is led from the position of the discharge pipe of a preheating cyclone to divide the material as the raw material for producing dry aluminum hydroxide. An electric star valve is set in the material dividing device, and the divided dry powder is sent into a small bin by a tubular screw conveyor. The small bin supplies materials to a multi-layer vibrating screen centrally. The dry powder material in the small bin enters the multi-layer vibrating screen by self-pressure. The oversize materials on each layer of the vibrating screen are used as qualified dry aluminum hydroxide products, and the undersize materials on the last layer are used as unqualified tailings (return materials) and returned to the roasting furnace system.

[0061] The qualified dry aluminum hydroxide products are centrally fed into a vertical fluidized bed for cooling by self-pressure, and the cooled dry aluminum hydroxide is then transported into a large bin for storage by self-pressure through a pipeline. The unqualified tailings are centrally collected into a material-sealing pump, and the return materials are transported to the roasting furnace by the material-sealing pump. The equipment is controlled by a PLC or directly connected to the alumina DCS system, and production is carried out according to the order quantity to achieve continuous and stable operation. The single-unit production capacity of the vibrating screen is 5-6t / h, and the number of equipment starts and stops can be determined according to the current order.

[0062] Specifically, this embodiment also discloses the inherent process of the roasting furnace: The aluminum hydroxide entering the system is first sent into a feed bin, then weighed by an electronic quantitative feeder scale and enters a feed screw, and is sent into a Venturi dryer by the feed screw. The aluminum hydroxide is dried by the high-temperature flue gas from the roasting furnace in the Venturi dryer. The gas inlet temperature reaches 310-350°C. The aluminum hydroxide basically removes the surface water in the Venturi dryer and is lifted to a separation cyclone by the high-temperature flue gas. The gas outlet temperature in the Venturi dryer reaches 145-160°C.

[0063] Based on the roasting flue gas conditions of the existing P04 (main roasting furnace) in the system, mass balance and heat balance calculations are carried out for the drying process of aluminum hydroxide in the Venturi dryer under typical working conditions and test working conditions, and it is checked whether the A02 flue gas outlet temperature under the test working conditions meets the production requirements;

[0064] For the heat balance calculation of the Venturi dryer under the test working conditions, the typical working condition is 230t / h. Under the test working conditions, since the feeding amounts are changed to 260t / h and 270t / h respectively, the heat balance of the Venturi dryer is re-carried out, and it is checked whether the flue gas outlet temperature meets the production requirements.

[0065] Regard the unbalanced item as a fixed value and keep it the same as that under the typical working condition. Using the single-variable solution function of excel, set the target value of the difference between the total heat income and the total heat expenditure to be the same as the value of the unbalanced item, and the variable is the flue gas outlet temperature t 2 ” and t 3”, the outlet flue gas temperature is 146°C at a blanking rate of 260 t / h and 144°C at a blanking rate of 270 t / h. In factory production, the requirement for the outlet flue gas temperature is generally above 145°C (to prevent water from condensing at too low an outlet temperature and combining with sulfur oxides to cause corrosion of production equipment). Therefore, without changing the fuel consumption, the outlet flue gas temperature at a blanking rate of 270 t / h does not meet the production requirements.

[0066] Given that the change in the outlet temperature is small, the physical property parameters (specific heat capacity, density) during the drying process are the same as those under typical working conditions.

[0067] Thermal balance calculations are carried out for two experimental working conditions. The formula is similar to that of the typical working condition and will not be elaborated in detail. Only the results are listed in Tables 1 and 2.

[0068] Table 1 Thermal balance calculation results under experimental working condition of 260 t / h

[0069]

[0070]

[0071] Table 2 Thermal balance calculation results under experimental working condition of 270 t / h

[0072]

[0073]

[0074] In this paper, combustion calculations are carried out for the gas combustion process in the main furnace P04 (roasting main furnace), and thermal balance analysis is carried out for the alumina roasting process in the Venturi dryer under three working conditions (typical working condition and two experimental working conditions). Finally, under the two experimental working conditions, that is, when the blanking rates are 260 t / h and 270 t / h, the outlet flue gas temperatures of the Venturi dryer are 146°C and 144°C respectively. Without changing the fuel consumption, the outlet flue gas temperature at a blanking rate of 260 t / h meets the factory production parameter requirements, while the outlet flue gas temperature at a blanking rate of 270 t / h does not meet the factory production parameter requirements.

[0075] Based on the ANSYS FLUENT software platform, numerical simulations are carried out on the gas-solid flow process in the separation cyclone and the Venturi dryer under experimental working conditions to analyze whether the flue gas conditions in the Venturi dryer under experimental working conditions can meet the requirements of material gas flow transportation and whether the separation cyclone can achieve effective gas-solid separation.

[0076] Considering that the flow field of the separation cyclone in actual engineering has periodic changes over time, according to the simulation results, the results during the period of 12.5 - 15 s are selected, and six groups of particle flow data at the upper and lower outlets of the cyclone separator are obtained at intervals of 0.5 s as the calculation basis.

[0077] The calculation formula for the separation efficiency η of the separation cyclone is as follows:

[0078]

[0079] Where n 1 is the number of particles flowing out of the lower outlet, and n 2 is the number of particles flowing out of the upper outlet.

[0080] The statistics of the number of particle outflows are shown in Table 3.

[0081] Table 3 Statistics of the number of particle outflows

[0082]

[0083]

[0084] Analysis of the above table shows that the separation efficiency of AO particles is 100%, and no AO particles flow out of the upper outlet of the separation cyclone. This is because the density and particle size of AO particles are relatively large, and they are separated to the vicinity of the cylinder wall by centrifugal force and fall into the lower conical space under the influence of gravity, and finally flow out of the separation cyclone through the lower outlet; the separation efficiency of aluminum hydroxide particles is 98.88%, and a small number of aluminum hydroxide particles flow out of the upper outlet. This is because the density and particle size of aluminum hydroxide particles are relatively small, the centrifugal force they receive is less than the pressure of the cylinder wall inward, and a part of the aluminum hydroxide particles are pressed towards the center and are affected by the upward force of the gas phase in the central cylinder on the particle phase, and finally are carried out of the separation cyclone through the upper outlet with the flue gas.

[0085] The total separation efficiency of the separation cyclone under the experimental conditions is 99.49%, meeting the production process standard of the separation cyclone.

[0086] The gas flow field of the Venturi dryer under the 260t / h working condition was numerically simulated. It was found that under the existing flue gas conditions, the particles in the Venturi dryer showed periodic changes of falling and lifting, but there was no phenomenon of aluminum hydroxide flowing out of the lower flue gas outlet. Therefore, the existing flue gas conditions can meet the pneumatic conveying of materials in the Venturi dryer when the feeding amount of aluminum hydroxide is 260t / h.

[0087] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. For the same or similar parts between the various embodiments, reference can be made to each other.

[0088] In this article, specific examples are used to illustrate the principles and implementation manners of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A production device for dry aluminum hydroxide, characterized in that: include: A control system and a material distribution system, a screening system, a cooling system, and a packaging system all connected to the control system, wherein the material distribution system, the screening system, the cooling system, and the packaging system are connected in sequence section by section using pipelines; The material dividing system is used to intercept dry aluminum hydroxide dried by flue gas waste heat to obtain graded raw materials. The screening system grades the graded raw materials to obtain qualified oversize materials and unqualified undersize materials. The cooling system is used to cool the qualified oversize materials to obtain cooled oversize materials. The packaging system is used to package the qualified oversize materials. The control system is used to regulate the operating parameters of the material dividing system, the screening system, the cooling system, and the packaging system.

2. A production device for dry aluminum hydroxide according to claim 1, characterized in that, The material distribution system comprises: Feeding tee, material seal, pneumatic gate valve, tubular screw conveyor, small material silo; The material discharge tee is used to flow the dry aluminum hydroxide dried by the flue gas waste heat to the material seal, and the material seal seals the roasting furnace to maintain a constant pressure. The pneumatic gate valve is used to isolate the dry aluminum hydroxide during equipment maintenance. The tubular screw conveyor is used to transport the dry aluminum hydroxide in the material seal to a small silo for storage to obtain graded raw materials.

3. A production device for dry aluminum hydroxide according to claim 1, characterized in that, The screening system comprises: Star-shaped discharge valve, multi-layer swing screen, material sealing pump, slide pipe; The star-shaped discharge valve is used to control the feed amount of the graded raw materials, the multi-layer swing screen is used to obtain qualified upper-screen materials and unqualified lower-screen materials by combining planar circular motion with parabolic motion, the material sealing pump is used to use high-pressure gas to return the unqualified lower-screen materials to the roasting furnace, and the chute is used to transport the qualified upper-screen materials to the cooling system.

4. A production device for dry aluminum hydroxide according to claim 1, characterized in that, The cooling system comprises: Fluidized beds and large silos; The fluidized bed is used to cool the qualified oversize material by using circulating water to obtain the cooled oversize material, and the large silo is used to store the cooled oversize material.

5. A production device for dry aluminum hydroxide according to claim 1, characterized in that, The packaging system comprises: Packaging machine, chain conveyor, dust collector; The chain conveyor is used to orderly transport materials or packaged products that need to be moved or transported before and after packaging. The dust collector is used to collect and purify the dust generated during the packaging process. The packaging machine is used to automatically or semi-automatically package qualified and cooled dry aluminum hydroxide in a large silo.

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