An apparatus for producing dry aluminum hydroxide

Abstract

The application provides a dry aluminum hydroxide production device and relates to the technical field of flue gas waste heat. The device comprises a control system and a distribution system, a screening system, a cooling system and a packaging system which are all connected with the control system. The distribution 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 screen-up materials and unqualified screen-down materials. The cooling system is used for cooling the qualified screen-up materials to obtain cooled screen-up materials. The packaging system is used for packaging the qualified screen-up materials. The control system is used for regulating and controlling the operating parameters of the distribution system, the screening system, the cooling system and the packaging system. The application solves the problems of high energy consumption loss and low energy utilization rate caused by flue gas waste heat utilization rate in the prior art aluminum oxide production process.

Description

Technical Field

[0001] This invention relates to the field of flue gas waste heat technology, and in particular to a production apparatus for dry aluminum hydroxide. Background Technology

[0002] Currently, the metallurgical grade aluminum hydroxide sold on the market is mainly primary wet aluminum hydroxide produced by the Bayer process disc filter. The moisture content (adhered water) is about 3-5%, and the particle size fluctuates greatly, resulting in poor product quality stability.

[0003] Aluminum fluoride [AlF3] manufacturers are among the main customers of aluminum hydroxide. In the dry process of aluminum fluoride production, the required moisture content (adhered water) is ≤3%, and the particle size (-45μm) is ≤5%. For dry aluminum hydroxide, the requirements are ≤0.1% adhered water, specific gravity >1.22, and an appearance of white powder or granular crystals. If the aluminum hydroxide particle size is too fine, it can easily clog the aluminum fluoride production system. Furthermore, its physical properties not only affect the appearance of the finished product but also the unit consumption. Therefore, quality control of aluminum hydroxide is a crucial aspect of the dry process of aluminum fluoride production.

[0004] Therefore, the shortcomings of the existing technology are: the waste heat of the flue gas in the roasting furnace mainly uses water as a heat exchange medium, but it cannot achieve the ultimate utilization of the waste heat of the flue. In contrast, this technology directly uses the waste heat of the flue gas to heat the materials, reducing intermediate energy consumption losses and achieving higher energy utilization. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the purpose of this invention is to provide a production apparatus for dry aluminum hydroxide.

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

[0007] An apparatus for producing dry aluminum hydroxide, comprising:

[0008] The control system and the material distribution system, screening system, cooling system, and packaging system, all connected to the control system, are connected sequentially in sections via pipelines.

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

[0010] Preferably, the material distribution system includes:

[0011] Material feeding tee, material seal, pneumatic slide gate valve, tubular screw conveyor, small silo;

[0012] The feeding tee is used to flow the dried aluminum hydroxide after the waste heat of the flue gas is dried to the material seal. The material seal is used to seal the roasting furnace under constant pressure. The pneumatic slide valve is used to isolate the dried aluminum hydroxide during equipment maintenance. The tubular screw conveyor is used to transport the dried aluminum hydroxide in the material seal to the small material bin for storage, thus obtaining graded raw materials.

[0013] Preferably, the screening system includes:

[0014] Rotary star-shaped feed valve, multi-layer gyratory screen, material sealing pump, chute;

[0015] The star-shaped feed valve is used to control the feed rate of the graded raw materials. The multi-layer gyratory screen is used to obtain qualified screen feed and unqualified screen underfeed by combining planar circular motion and parabolic motion. The material sealing pump is used to use high-pressure gas to return the unqualified screen underfeed to the roasting furnace. The chute is used to transport the qualified screen feed to the cooling system.

[0016] Preferably, the cooling system includes:

[0017] Fluidized bed and large silo;

[0018] The fluidized bed is used to cool the qualified screen feed material using circulating water to obtain cooled screen feed material, and the large silo is used to store the cooled screen feed material.

[0019] Preferably, the packaging system includes:

[0020] Packaging machines, chain conveyors, dust collectors;

[0021] The chain conveyor is used to orderly transport materials or finished 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 package qualified and cooled dry aluminum hydroxide in the large silo.

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

[0023] This invention provides a production apparatus for dry aluminum hydroxide, comprising: a control system and a material distribution system, a screening system, a cooling system, and a packaging system, all connected to the control system. The material distribution system is used to extract dry aluminum hydroxide after waste heat drying of flue gas, obtaining graded raw materials. The screening system grades the graded raw materials, obtaining qualified oversize material and unqualified undersize material. The cooling system is used to cool the qualified oversize material, obtaining cooled oversize material. The packaging system is used to package the qualified oversize material. The control system is used to regulate the operating parameters of the material distribution system, screening system, cooling system, and packaging system. This invention reduces energy consumption by combining waste heat drying from a preheated cyclone separator with the material distribution system. Furthermore, it significantly improves production capacity and accuracy by utilizing a multi-layer oscillating screen combined with ultrasonic cleaning. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of a dry aluminum hydroxide production apparatus provided in an embodiment of the present invention;

[0026] Figure 2 A detailed schematic diagram of a dry aluminum hydroxide production apparatus provided in an embodiment of the present invention;

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

[0028] Explanation of reference numerals in the attached figures:

[0029] 1-Control system, 2-Distribution system, 3-Screening system, 4-Cooling system, 5-Packaging system. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] like Figure 1 As shown, the present invention provides an apparatus for producing dry aluminum hydroxide, comprising:

[0033] The system consists of a control system 1 and a material distribution system 2, a screening system 3, a cooling system 4, and a packaging system 5, all of which are 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 extract dry aluminum hydroxide after the waste heat of flue gas is dried to obtain graded raw materials. The screening system 3 classifies the graded raw materials to obtain qualified oversize material and unqualified undersize material. The cooling system 4 is used to cool down the qualified oversize material to obtain cooled oversize material. The packaging system 5 is used to package the qualified oversize material. The control system 1 is used to regulate the operating parameters of the material distribution system 2, screening system 3, cooling system 4, and packaging system 5.

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

[0036] Material feeding tee, material seal, pneumatic slide gate valve, tubular screw conveyor, small silo;

[0037] The feeding tee is used to flow the dried aluminum hydroxide after the waste heat of the flue gas is dried to the material seal. The material seal is used to seal the roasting furnace under constant pressure. The pneumatic slide valve is used to isolate the dried aluminum hydroxide during equipment maintenance. The tubular screw conveyor is used to transport the dried aluminum hydroxide in the material seal to the small material bin for storage, thus obtaining graded raw materials.

[0038] Specifically, the material distribution system 2 includes, from top to bottom, a material discharge tee, a material seal, a pneumatic gate valve, a tubular screw conveyor, and a small hopper, all connected to the preheated cyclone discharge pipe. Its function is to use the dried aluminum hydroxide, obtained by extracting waste heat from the flue gas, as the screening raw material. Under gravity, the dried aluminum hydroxide flows from the material discharge tee to the material seal. The material seal maintains a constant pressure and seals the calcining furnace. The pneumatic gate valve isolates the material. The tubular screw conveyor temporarily stores the material in the small hopper. The conveying volume is controlled by frequency conversion speed regulation.

[0039] Furthermore, the screening system 3 includes:

[0040] Rotary star-shaped feed valve, multi-layer gyratory screen, material sealing pump, chute;

[0041] The star-shaped feed valve is used to control the feed amount of the graded raw materials. The multi-layer gyratory screen is used to obtain qualified screen feed and unqualified screen underfeed by combining planar circular motion and parabolic motion. The material sealing pump is used to use high-pressure gas to return the unqualified screen underfeed to the roasting furnace. The chute is used to transport the qualified screen feed to the cooling system 4.

[0042] Specifically, the function of screening system 3 is to receive materials from distribution system 2. Qualified oversize material is sent to the fluidized bed for cooling via a chute, while unqualified undersize material is returned to the roasting furnace using a material sealing pump. The star-shaped feed valve uses frequency conversion speed regulation to obtain the required feed rate. The star-shaped feed valve adjusts the feed rate of the gyratory screen according to the rotation speed of the valve core.

[0043] The multi-layer gyratory screen is currently the most effective screening machine to mimic human manual movements and processes. Its unique design cleverly combines screening (planar circular motion) and winnowing (upward parabolic motion). By adjusting the meridional and tangential angles, the screening effect can be optimized to achieve the desired result. The adjustment of the meridional and tangential angles of the multi-layer gyratory screen causes the material to move involutely on the screen mesh. This trajectory allows the material to travel a relatively long distance in a smaller area, improving screening accuracy. The unique design also results in a longer contact time with the screen compared to other screening machines. Combined with an ultrasonic cleaning system, this increases screening output. The material conveying pump uses high-pressure gas for pneumatic conveying of the material. The chute is mainly responsible for conveying the 48m plane-screened material down to the fluidized bed.

[0044] Furthermore, the cooling system 4 includes:

[0045] Fluidized bed and large silo;

[0046] The fluidized bed is used to cool the qualified screen feed material using circulating water to obtain cooled screen feed material, and the large silo is used to store the cooled screen feed material.

[0047] Specifically, cooling system 4 includes a fluidized bed and a large silo. After being cooled by the fluidized bed, qualified dry aluminum hydroxide is temporarily stored in the large silo. Its function is to use circulating water as a coolant to reduce the temperature of dry aluminum hydroxide from 150°C to 70°C.

[0048] Furthermore, the packaging system 5 includes:

[0049] Packaging machines, chain conveyors, dust collectors;

[0050] The chain conveyor is used to orderly transport materials or finished 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 the large silo.

[0051] Specifically, the control system includes: a large silo tuning fork level gauge, a small silo weighing system, a fluidized bed discharge thermometer, a circulating water thermometer, a distribution gate valve, a tubular screw variable frequency speed controller, a gyratory screen star valve, and a circulating water regulating valve. The large silo tuning fork level gauge is used to monitor the liquid level in the large silo in real time. When the liquid level reaches the set high or low point, the sensor will send a feedback signal to the control system to achieve automatic control.

[0052] Small silo weighing system: Monitors the weight of materials in the small silo in real time using a precise weighing system to determine material distribution and production progress, and performs corresponding operations when set values ​​are reached. Fluidized bed discharge thermometer: Ensures the discharge temperature is within a reasonable range to prevent excessive temperature from affecting subsequent processing stages. Circulating water thermometer: Monitors circulating water temperature changes to ensure effective operation of the cooling system. Distributor gate valve: Controls the flow rate of dry aluminum hydroxide based on operational feedback to meet system load requirements and ensure production continuity. Tubular screw conveyor frequency converter: Utilizes frequency conversion speed control technology to adjust the screw conveyor speed, balance the weight of the small silo, and ensure continuous and uniform material flow. Gyratory screen star valve: Regulates the amount of material flowing into the gyratory screen to optimize capacity and optimal screening rate, improving screening efficiency. Circulating water regulating valve: Automatically adjusts the circulating water flow rate based on changes in the fluidized bed discharge temperature to maintain the system's cooling effect and ensure stable production.

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

[0054] Large silo level monitoring: The level of the large silo is monitored by a level gauge. If the level reaches the set full state, the control system will automatically close the dispensing gate valve and suspend the operation of the entire system to prevent overflow or production chaos.

[0055] Small hopper weight balancing: The weight change of the small hopper will be fed back to the frequency converter, which will adjust the speed of the tubular screw to achieve material balance and timely replenishment, thereby maintaining the stable flow of the production line.

[0056] Screening adjustment: The star-shaped feed valve adjusts the amount of material entering the gyratory screen according to real-time data to ensure that the gyratory screen's capacity is within the optimal working range to achieve the highest screening efficiency.

[0057] Circulating water flow control: The circulating water regulating valve will automatically adjust the water flow according to the discharge temperature of the fluidized bed to ensure cooling efficiency, prevent overheating of the discharge, and protect the equipment and product quality.

[0058] System balance assessment: The liquid level in the large silo and the weight feedback in the small silo are the main criteria for judging the system's operational balance. Through real-time monitoring and feedback adjustments, material balance and stable operation during the production process are ensured.

[0059] Furthermore, such as Figure 2-3 As shown, this embodiment discloses a specific workflow:

[0060] A bypass pipe is drawn from the feed pipe of a preheated cyclone separator to distribute the material as raw material for the production of dry aluminum hydroxide. The distributing device is equipped with an electric rotary valve, and the distributed dry powder is sent to a small silo by a tubular screw conveyor. The small silo provides centralized feeding to a multi-layer gyratory screen. The dry powder material in the small silo is pressurized into the multi-layer gyratory screen. The material oversizes from each layer of the gyratory screen is the qualified dry aluminum hydroxide product, and the material undersizes from the last layer is the unqualified tail material (return material) and is returned to the calcining furnace system.

[0061] Qualified dry aluminum hydroxide is centrally pressurized into a vertical fluidized bed for cooling. The cooled dry aluminum hydroxide is then conveyed by pressurized pipelines to a large storage silo. Unqualified waste material is centrally collected and pumped back to the calcining furnace by a material sealing pump. The equipment is controlled by a PLC or directly connected to an alumina DCS system, producing according to orders and achieving continuous and stable operation. A single swing screen has a capacity of 5-6 t / h, and the number of units operating can be determined based on current orders.

[0062] Specifically, this embodiment also discloses the inherent process of the calcining furnace: aluminum hydroxide entering the system is first fed into the feeding hopper, then weighed by an electronic quantitative feeder and fed into the feeding screw, which then feeds it into the Venturi dryer. In the Venturi dryer, the aluminum hydroxide is dried by high-temperature flue gas from the calcining furnace, with the gas inlet temperature reaching 310-350°C. The aluminum hydroxide basically loses its surface water in the Venturi dryer and is then lifted by the high-temperature flue gas to the separation cyclone. The gas outlet temperature in the Venturi dryer reaches 145-160°C.

[0063] Based on the existing roasting flue gas conditions of the P04 (roasting main furnace) of the system, the mass balance and heat balance calculations of aluminum hydroxide drying process in Venturi dryer under typical and experimental conditions are performed, and the A02 flue gas outlet temperature under experimental conditions is checked to see if it meets the production requirements.

[0064] The heat balance calculation of the Venturi dryer under experimental conditions was carried out. The typical operating condition is 230t / h. Under the experimental conditions, the feed rate was changed to 260t / h and 270t / h respectively. The heat balance of the Venturi dryer was re-performed, and the flue gas outlet temperature was checked to see if it met the production requirements.

[0065] The imbalance term is treated as a fixed value, consistent with typical operating conditions. Using Excel's single-variable solver, the target value of the difference between total heat income and total heat expenditure is set to be consistent with the value of the imbalance term. The variable values ​​are the flue gas outlet temperature t2” and t3”. The results show that the outlet flue gas temperature is 146℃ for a feed rate of 260t / h and 144℃ for a feed rate of 270t / h. In factory production, the required flue gas outlet temperature is generally above 145℃ (to prevent water precipitation and sulfur oxides from combining and corroding production equipment due to excessively low outlet temperatures). Therefore, without changing the fuel consumption, the outlet flue gas temperature at a feed rate of 270t / h does not meet the production requirements.

[0066] Given that the outlet temperature changes little, the physical properties (specific heat capacity, density) during the drying process are consistent with those under typical operating conditions.

[0067] Thermal balance calculations were performed for two experimental conditions. The formulas are similar to those for typical conditions and will not be explained in detail. Only the results are listed in Tables 1 and 2.

[0068] Table 1. Heat balance calculation results under experimental condition 260t / h

[0069]

[0070]

[0071] Table 2. Heat balance calculation results under experimental condition 270t / h

[0072]

[0073]

[0074] This paper presents combustion calculations for the gas combustion process in the main furnace P04 (calcining furnace). Simultaneously, it conducts heat balance analysis on the aluminum hydroxide calcination process in the Venturi dryer under three operating conditions (typical and two experimental conditions). The results show that the flue gas outlet temperatures of the Venturi dryer under the two experimental conditions—feed rates of 260 t / h and 270 t / h—are 146℃ and 144℃, respectively. Without changing the fuel consumption, the flue gas outlet temperature at a feed rate of 260 t / h meets the plant's production parameter requirements, while the flue gas outlet temperature at a feed rate of 270 t / h does not.

[0075] Based on the ANSYS FLUENT software platform, the gas-particle flow process in the separation cyclone and Venturi dryer under experimental conditions was numerically simulated. The analysis was conducted to determine whether the flue gas conditions in the Venturi dryer under experimental conditions could meet the material flow transport requirements, and whether the separation cyclone could achieve effective gas-particle separation.

[0076] Considering that the flow field of the cyclone separator changes periodically with time in actual engineering, the results from 12.5 to 15 seconds were selected based on the simulation results. Six sets of particle flow data at the upper and lower outlets of the cyclone separator were obtained at 0.5-second intervals as the basis for calculation.

[0077] Formula for calculating the separation efficiency η of a cyclone separator:

[0078]

[0079] Where n1 is the number of particles exiting from the lower outlet, and n2 is the number of particles exiting from the upper outlet.

[0080] The number of particles effluent is shown in Table 3.

[0081] Table 3. Statistics on the number of particles effluent

[0082]

[0083]

[0084] Analysis of the table above reveals that the separation efficiency of AO particles is 100%, with no AO particles flowing out from the upper outlet of the separation cyclone. This is because AO particles have a relatively large density and size, causing them to be separated by centrifugal force and located near the cylinder wall. Under the influence of gravity, they fall into the lower conical space and eventually flow out of the separation cyclone through the lower outlet. The separation efficiency of aluminum hydroxide particles is 98.88%, with a small portion of aluminum hydroxide particles flowing out from the upper outlet. This is because aluminum hydroxide particles have a relatively small density and size, resulting in a centrifugal force that is less than the inward pressure of the cylinder. Some aluminum hydroxide particles are pressed towards the center and subjected to the upward force of the gas in the center of the cylinder relative to the particles, ultimately being carried out of the separation cyclone through the upper outlet along with the flue gas.

[0085] The total separation efficiency of the separation cyclone under experimental conditions was 99.49%, which met the production process standards for separation cyclones.

[0086] Numerical simulations were performed on the airflow field of a Venturi dryer operating at 260 t / h. The results showed that under the existing flue gas conditions, the particles in the Venturi dryer exhibited a periodic downward-upward change, but no aluminum hydroxide flowed out from the lower flue gas outlet. Therefore, the existing flue gas conditions can meet the pneumatic conveying requirements of the material within the Venturi dryer when the aluminum hydroxide feed rate is 260 t / h.

[0087] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0088] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A production apparatus for dry aluminum hydroxide, characterized in that, include: The control system and the material distribution system, screening system, cooling system, and packaging system, all connected to the control system, are connected sequentially in sections via pipelines. The material distribution system is used to extract dry aluminum hydroxide after the waste heat of flue gas is dried to obtain graded raw materials. The screening system classifies the graded raw materials to obtain qualified oversize material and unqualified undersize material. The cooling system is used to cool down the qualified oversize material to obtain cooled oversize material. The packaging system is used to package the qualified oversize material. The control system is used to regulate the operating parameters of the material distribution system, screening system, cooling system and packaging system. The material distribution system includes: Material feeding tee, material seal, material distribution gate valve, tubular screw conveyor, small silo; The feeding tee is used to flow the dry aluminum hydroxide after the waste heat of the flue gas is dried to the material seal. The material seal seals the roasting furnace to maintain constant pressure. The material distribution 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 the small material bin for storage, thus obtaining graded raw materials. The screening system includes: a star-shaped feed valve, a multi-layer gyratory screen, a material sealing pump, and a chute; The star-shaped feed valve is used to control the feed amount of the graded raw materials. The multi-layer gyratory screen is used to obtain qualified screen feed and unqualified screen underfeed by combining planar circular motion and parabolic motion. The material sealing pump is used to use high-pressure gas to return the unqualified screen underfeed to the roasting furnace. The chute is used to transport the qualified screen feed to the cooling system. The cooling system includes: Fluidized bed and large silo; The fluidized bed is used to cool the qualified screen feed material using circulating water to obtain cooled screen feed material, and the large silo is used to store the cooled screen feed material; The large silo tuning fork level gauge is used to monitor the liquid level in the large silo in real time. If the liquid level reaches the set full state, the control system automatically closes the distribution gate valve and suspends the operation of the entire system. The small silo weighing system monitors the weight of the material in the small silo in real time. The weight change of the small silo is fed back to the tubular screw variable frequency speed controller. The tubular screw variable frequency speed controller adjusts the speed of the tubular screw conveyor to achieve material balance and timely replenishment. The fluidized bed discharge temperature gauge ensures that the discharge temperature is within a reasonable range. The circulating water temperature gauge monitors the temperature change of the circulating water. The distribution gate valve controls the flow rate of dry aluminum hydroxide based on the feedback of the operation. The star-shaped discharge valve is responsible for regulating the amount of material flowing into the multi-layer gyratory screen. The circulating water regulating valve automatically adjusts the flow rate of the circulating water according to the change of the fluidized bed discharge temperature.

2. The apparatus for producing dry aluminum hydroxide according to claim 1, characterized in that, The packaging system includes: Packaging machines, chain conveyors, dust collectors; The chain conveyor is used to orderly transport materials or finished 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 package qualified and cooled dry aluminum hydroxide in the large silo.

Images