CN108751244A - A kind of crystallization aluminium salt roasting prepares the integrating device of technical grade aluminium oxide - Google Patents

Abstract

The present invention relates to the integrating devices that a kind of crystallization aluminium salt roasting prepares technical grade aluminium oxide.Material crystal aluminium salt enters material and is crushed and lays in feed conveying system, and broken material enters the low-temperature zone that fluidization integrates roaster by multiple feed pipeline；The flue gas of corrosion containing sour of roaster is integrated from fluidization and entrained solid particle enters nonaqueous dust cleaner by the second flue, and the solid particle after gas solid separation is again introduced into the high temperature section that fluidization integrates roaster through the 4th pipeline；The flue gas of corrosion containing sour after gas solid separation enters waste heat boiler Mist heat recovering by third flue, enters acid recovery system using the 4th flue, and by-product finished acid, the discharge of tail gas environment protection standard are recycled by cooling, washing, absorption technique process.The present invention can solve the problems, such as that existing crystallization aluminium salt roasting technique may cause environmental pollution to material bad adaptability, roasting high energy consumption, sour gas, and level of integrated system is high, reliable for operation, good product quality, good environmental protection.

Description

An integrated device for preparing industrial grade alumina by roasting crystalline aluminum salt

technical field

The invention relates to an integrated device for preparing industrial-grade alumina by calcination of crystalline aluminum salts. It adopts an integral fully enclosed fluidized integrated calcination furnace, and uses high-temperature flue gas as a heat source to continuously complete the calcination process of crystalline aluminum salts. The function of slagging-free roasting to prepare industrial grade alumina and recover acid-containing corrosive flue gas by-product product acid.

Background technique

Conventional alumina production uses bauxite resources and adopts the Bayer process to produce industrial metallurgical grade alumina. In the Bayer method, aluminum ore is treated with NaOH circulating mother liquor to dissolve alumina, and the seed crystal decomposition method is used to make the alumina in the solution into aluminum hydroxide crystals, which are then roasted to prepare industrial metallurgical grade alumina. About 40% of the world's alumina production capacity is located in China, and China's bauxite resources only account for about 3% of the global bauxite resources. my country's bauxite resources are relatively scarce, and the supply of bauxite market is in short supply. China needs to import a large amount of aluminum every year. Soil ore, my country's bauxite resources are more than 70% dependent on foreign countries.

In view of the serious shortage of bauxite resources in my country, substitutes for bauxite are used, such as fly ash, coal gangue, industrial metallurgical slag, and crystalline aluminum salts are used as intermediate products, such as crystalline aluminum chloride hexahydrate and crystalline aluminum sulfate , ammonium aluminum sulfate, ammonium aluminum carbonate, aluminum hydroxide, etc. The technology of preparing alumina by roasting crystalline aluminum salts has become the research focus of many scientific research institutions at home and abroad.

Fly ash is a solid particle that is discharged from the tail of the boiler with the flue gas after the coal is burned in the boiler and collected by the dust collector. It belongs to industrial solid waste. In the coal combustion fly ash in some areas of the country, the alumina content is as high as 40% to 55%, which has reached the cut-off grade of bauxite resources. The extraction of aluminum resources not only solves the environmental hazards of fly ash, but also alleviates the extreme shortage of bauxite resources in my country to a certain extent. Fly ash can become a valuable resource for extracting alumina. The domestic potential high-alumina fly ash resources are 15 billion tons, exceeding the total proven bauxite resources in China. It is an important bauxite reserve resource in China.

From the 1940s to the present, the comprehensive utilization research technology of fly ash has always been a research hotspot in domestic and foreign scientific research structures. The techniques for extracting alumina from fly ash mainly include acid method, alkali method and combined acid-base method. The acid process is to dissolve fly ash in hydrochloric acid or sulfuric acid solution to realize the separation of silicon and aluminum, evaporate, concentrate and crystallize to obtain various crystalline aluminum salt intermediate products, and then roast them to produce industrial grade alumina. The acid gas produced by roasting passes through the absorption system to regenerate hydrochloric acid and sulfuric acid, which are reused for the acid dissolution of fly ash to realize the closed cycle of acid. The crystalline aluminum salts of the acid process include crystalline aluminum chloride hexahydrate, crystalline aluminum sulfate, etc., and the crystalline aluminum salts of the alkali process and other processes include aluminum ammonium sulfate, aluminum ammonium carbonate, aluminum hydroxide, etc.

The reaction mechanism of preparing industrial grade alumina by roasting crystalline aluminum salt is as follows: Take aluminum chloride hexahydrate and aluminum hydroxide as examples, and others are similar:

(1) Remove the attached water, and the thermal reduction of aluminum chloride hexahydrate is 5%.

AlCl ₃ ﹡6H ₂ O+attached water→AlCl ₃ ﹡6H ₂ O+water vapor↑

Al(OH) ₃ ﹡2H ₂ O+attached water→Al(OH) ₃ ﹡2H ₂ O+water vapor↑

(2) Slough crystal water, thermal decomposition, and the thermal reduction of aluminum chloride hexahydrate is 71%.

2AlCl ₃ ﹡6H ₂ O→Al ₂ O ₃ +6HCl↑+9H ₂ O↑

Al(OH) ₃ ﹡2H ₂ O→Al ₂ O ₃ +3H ₂ O↑

(3) Crystal transformation

γ-Al ₂ O ₃ →α-Al ₂ O ₃

At 1000°C, the calcined product of AlCl ₃ *6H ₂ O is mainly γ-Al ₂ O ₃ , and at 1150°C, it gradually changes from γ-Al ₂ O ₃ to α-Al ₂ O ₃

(4) Grading adjustment

The content of α-Al ₂ O ₃ reflects the roasting degree of alumina. The higher the degree of calcination, the more α-Al ₂ O ₃ content, the specifications of industrial grade alumina products are shown in Table 1.

Table 1 Industrial grade alumina products

Roasting of crystalline aluminum salts is the key technology for preparing industrial grade alumina. Under industrial production conditions, the crystalline aluminum salt has a high water content, is very easy to absorb water and deliquescence, and the material is easy to deliquescence and harden. For example, the aluminum chloride hexahydrate crystal contains about 10% of attached water, and the production of one ton of alumina by roasting the aluminum chloride hexahydrate crystal requires 5.261 tons of raw materials and produces 4.261 tons of water vapor and hydrogen chloride.

Rotary kiln is a commonly used aluminum hydroxide roasting furnace equipment in the conventional alumina production process. In the rotary kiln, the flue gas convects heat with the material in the opposite direction, and the crystalline aluminum salt material has the defects of low heat transfer efficiency, high energy consumption, poor operation reliability, and serious pollution. The actual thermal efficiency of the rotary kiln is only 50-60%; After decades of development of traditional alumina roasting technology, major alumina production enterprises have gradually adopted fluidized roasting technology to replace the original rotary kiln, such as (fluid flash roaster (F.F.C), gas suspension roaster (G.S.C) and circulating fluidized calcination furnace (C.F.C) are the current advanced aluminum hydroxide calcination technologies, and the thermal efficiency of the fluidized calcination furnace can reach 78-83%.

Due to the large difference between the roasting mechanism of crystalline aluminum salt and the conventional alumina process, the existing fluidized roasting furnace has the following problems: (1) The feeding system cannot realize the transportation, crushing and storage of crystalline aluminum salt containing corrosion and deliquescent , the acid-containing gas is seriously corrosive to the system; (2) The thermal load of the Venturi dryer is too low to meet the energy requirements for dehydration and thermal decomposition of crystalline aluminum salts. The Venturi dryer is limited by the structure and air flow, and insufficient heat supply leads to incomplete reaction of crystalline aluminum salts, stickiness, agglomeration, and blockage of flue gas pipes, resulting in shutdown and production accidents; (3) Adaptation of calcination furnaces to crystalline aluminum salts Poor performance, volumetric heat load and heat transfer conditions of the calciner cannot meet the reaction heat demand of crystalline aluminum salt, and the energy distribution is unreasonable; if the temperature of the main furnace is increased, the alumina will be over-roasted, the α-Al ₂ O ₃ component will increase, and the product quality will be reduced. (4) The air velocity in the furnace is high, and the damage rate of alumina is high; the air velocity is too fast, the circulation volume increases, and the energy consumption increases; (5) The amount of material after roasting is 1/3 of the original, and the post-cyclone The efficiency of the heat exchange system is reduced, and the cyclone and pipeline airflow velocity is as high as 15 m/s, which may cause a large amount of alumina to be carried; (6) The multi-stage cyclone preheater system of the gas suspension furnace has air leakage, large system resistance, and difficult adjustment of the control system.

Patent CN101054192 discloses a method for preparing crystalline aluminum chloride from fly ash in a circulating fluidized bed, but does not propose a subsequent process and device for preparing alumina. Patents CN101811711A and CN101811712A disclose a process for extracting alumina from fly ash. The process adopts acid treatment, and after the fly ash is dissolved in hydrochloric acid, it undergoes sedimentation, evaporation and crystallization to form aluminum chloride hexahydrate, hexahydrate Aluminum chloride particles are decomposed into alumina and hydrogen chloride gas by roasting in a rotary kiln or a fluidized bed, and no subsequent preparation process and equipment for alumina are proposed. Patent CN101486478A discloses a method for preparing superfine aluminum hydroxide and aluminum oxide with circulating fluidized bed fly ash. The process adopts firstly obtaining aluminum hydroxide crystals from fly ash, and then obtaining aluminum oxide by calcining. Patent CN101117228 discloses a method for extracting alumina from fly ash. In this process, ammonium sulfate is mixed with fly ash for sintering, and the generated aluminum ammonium sulfate reacts with ammonia to obtain aluminum hydroxide crystals. Aluminum hydroxide crystals Calcined to get alumina. Patents CN103466672A and CN203529952U disclose a crystalline aluminum chloride roasting system and method, including a first fluidized bed roaster for roasting the fed crystalline aluminum chloride to obtain primary alumina; the second fluidized bed The roasting furnace is used for further calcining the primary alumina from the first fluidized bed roasting furnace to obtain alumina products. This patent is aimed at the roasting of crystalline aluminum chloride but does not propose a specific process. The roasting adopts a two-step method, which has poor industrial integration and high energy consumption. CN203440103 discloses a calcination system for crystalline aluminum chloride, which includes a rotary kiln, a fluidized bed dryer and a cyclone dust collector. The high-temperature flue gas is used to dry and dehydrate aluminum chloride hexahydrate, which can effectively reduce the energy consumption of calcination. This patent is aimed at the roasting of crystalline aluminum chloride but does not propose a specific process. The roasting adopts a two-step method of combining a rotary kiln and a fluidized bed, which has poor industrial integration and high energy consumption. CN104649306A discloses a method for extracting alumina from fly ash, which adopts two-stage fluidized roasting of fly ash and ammonium sulfate to solve the problems of high corrosion of equipment, wall sticking, agglomeration and coking during roasting. How to prepare the alumina process and equipment in the future is not proposed, and the roasting adopts a two-step method. CN104058436A discloses a device and method for preparing alumina by roasting crystalline aluminum chloride hexahydrate in a rotary kiln. The roasting uses a rotary kiln, and does not propose a subsequent process for preparing alumina. CN102502744A discloses a slagging-free, multi-stage differential temperature fluidized roasting system and method for crystalline aluminum salts. The roasting adopts a two-step process.

Patent analysis shows that the fluidized roasting furnace has good gas-solid contact, fast heat and mass transfer, high production efficiency, and good product quality. The use of fluidized roasting technology to process crystalline aluminum salts to prepare industrial-grade alumina is in line with the development trend of the industry. At present, there are not many patents involved, and most of them are derived from conventional alumina technology. The combined roasting of rotary kiln and single-stage fluidized bed and the combined roasting of two-stage fluidized bed are the main schemes. However, when using the above technologies for crystalline aluminum salt roasting , there are the following technical problems: (1) the integration of roasting equipment is poor, the stability of continuous operation is poor, and the energy consumption is high; (2) the moisture content of crystalline aluminum salt is high, and dehydration decomposition needs to absorb a lot of heat, so if conventional Grade roasting system, series cyclone recovery of waste heat as preheating unit, due to the concentrated release of a large amount of crystal water, insufficient heat supply, not timely, the material continues to be in a low temperature state, prone to agglomeration and slagging; (3) due to the crystalline aluminum salt The corrosive gases (such as HCl, SO ₃ ) released by roasting and decomposition are easy to condense and cause dew point corrosion, which brings serious corrosion problems to existing equipment, and the material requirements are relatively high. (4) Roasting of crystalline aluminum salt has a large heat absorption and decomposes to produce a large amount of corrosive gas and water vapor. If a conventional single fluidized bed roaster is used to process crystalline aluminum salt, the roaster is bulky and the amount of combustion material required for roasting is large. , economically unfeasible.

So far, the patented technology of the integrated device and method for preparing industrial-grade alumina by roasting crystalline aluminum salts is still a blank in the world. The difficulty is far greater than that of conventional aluminum hydroxide roasting technology, and new research is required.

Contents of the invention

The purpose of the present invention is to address the deficiencies in the prior art, to provide an integrated device for preparing industrial-grade alumina by calcination of crystalline aluminum salts, and to realize continuous feeding of crystalline aluminum salts without slagging by adopting a material crushing and storage feeding and conveying system, which can It solves the problems of poor adaptability to materials, high energy consumption of roasting, agglomeration of equipment and serious acid low-temperature dew point corrosion in the existing crystalline aluminum salt roasting process, and possible environmental pollution caused by acid gas in roasting flue gas. The system has high integration, reliable operation, The product quality is good and the environmental performance is good.

In order to achieve the above object, the technical scheme adopted in the present invention is:

An integrated device for preparing industrial-grade alumina by roasting crystalline aluminum salts. Raw crystalline aluminum salts enter the material crushing and storage feeding conveying system, and the crushed materials enter the low-temperature section of the fluidized integrated roasting furnace through multiple feeding pipelines; The acid-containing corrosive flue gas and entrained solid particles from the fluidized integrated roaster enter the dry dust collector through the second flue, and the solid particles after gas-solid separation enter the fluidized integrated roaster again through the fourth pipeline High-temperature section: After gas-solid separation, the acid-containing corrosive flue gas enters the waste heat boiler through the third flue to recover the waste heat of the flue gas, and then enters the acid recovery system through the fourth flue, and recovers by-products through cooling, washing and absorption processes Acid and tail gas are discharged up to environmental protection standards; solids from the fluidized integrated roaster enter the fluidized separator through the second discharge pipeline, and then enter the fluidized cooler through the first pipeline. After cooling down, the product alumina is sent to the Out of the output system of the finished alumina packaging system; the flue gas from the fluidized cooler passes through the second pipeline and part of the acid-containing and corrosive flue gas from the dry dust collector, and enters the flue gas recirculation system through the fifth pipeline After pressurization, the sixth pipeline merges into the hot blast stove. After being heated by fuel and air combustion, the flue gas is sent to the central area of the fluidized integrated roaster through multiple hot blast pipelines; the high-temperature flue gas after combustion is fluidized through the first The first hot flue gas pipeline and the second hot flue gas pipeline enter the fluidized integrated roaster to provide stable high-temperature fluidized air for solid fluidization; the lower part of the fluidized integrated roaster is equipped with a first discharge pipeline, which is a solid bed The discharge channel of the material reduces the stock of solid material in the furnace; 160°C preheated air and 0.6MPaG saturated water vapor enter the fluidized separator to cool the material and remove the hydroxyl content in the solid, providing stable low-temperature fluidization for solid fluidization wind.

The material crushing and storage feeding conveying system is made of acid-resistant material, including a screw feeding device and a pneumatic feeding device.

The fluidized integrated roaster is an overall fully enclosed fluidized roaster, with a multi-layer circulating fluidized bed and ebullating fluidized bed parallel structure inside, designed as a conventional circulating fluidized bed or a suspended fluidized bed , the furnace wall is a fully lined adiabatic furnace wall or a water-cooled furnace wall with a water-cooled wall.

The fluidized integrated roaster includes a low-temperature section and a high-temperature section. The low-temperature section and the high-temperature section are connected through the first flue at the top and the valve at the bottom. The valve controls the cycle rate and adjusts the amount of material entering the high-temperature section. The high-temperature flue gas passes through the first flue at the top to directly heat the primary alumina to realize cascaded utilization of energy levels; the low-temperature section on the left adopts a fluidized bed with a high circulation rate, the operating temperature is 350-450°C, and the circulation rate is 15-25. The residence time is 10 to 15 minutes, and the process of removing attached water, crystal water, and thermal decomposition of crystalline aluminum salt is continuously completed. The crystalline aluminum salt is roasted to remove all free water and crystal water, and all or 80% of it is converted into crude alumina; the right side The high-temperature section adopts a fluidized bed with a low circulation rate, and a cyclone separation device is installed on the upper part. After the gas-solid separation of the acid corrosive flue gas and entrained solid particles through the cyclone separation device, the crude alumina particles are continuously sent to the high-temperature section. The operating temperature of the high-temperature section is 850-1050°C, the maximum furnace temperature can be increased to 1500°C, the cycle rate is 1-5, and the reaction residence time is 0.5-2min. The crude alumina is converted into qualified γ-Al ₂ O ₃ , and the crystallization is completed continuously. Type transformation and gradation adjustment process to meet the requirements of metallurgical grade alumina products.

The low-temperature section of the fluidized integrated roaster has a lower dense-phase region and a middle-upper dilute-phase region. The dilute-phase region is composed of dilute suspended gas and powder, and the density changes sharply at the boundary of the two phases; There are multiple sets of baffle parts inside the section to control the flow direction of the flue gas; the acid-containing corrosive flue gas from the hot blast stove is sprayed into the middle and lower part of the low temperature section at the junction of the dense phase area and the dilute phase area through the hot air pipeline, and then The feed port has an upward inclination angle of 45-60° to the vertical direction, and the number of channels is 4-8; the finished alumina is discharged continuously through the second discharge pipeline through the discharge port at the bottom of the high-temperature section.

The flue gas recirculation system adopts a flue gas circulation fan and supporting system to reduce the amount of combustion-supporting air, reduce the excess air coefficient, and has the functions of acid corrosion resistance and solid dust wear resistance; the flue gas recirculation volume is 40-60%, and the component volume Content proportion: O ₂ accounted for 1.38%, H ₂ O accounted for 30.57%, N ₂ accounted for 44.78%, CO ₂ accounted for 9.44%, HCL accounted for 13.38%, dust 50mg/Nm ³ .

The acid recovery system adopts a low-energy pneumatic tower structure, and the acid gas enters from the bottom of the pneumatic tower. Under the action of the cyclone, an upward swirling airflow with a certain speed is formed, and the absorption liquid injected from the upper end supports the repeated swirl. cutting, enhanced mixing, to achieve the purpose of acid gas absorption and dust capture; part of the hydrochloric acid from the bottom of the low-energy pneumatic tower is sent to the third-stage acid tank, and most of the rest is sent back to the low-energy pneumatic tower by the acid pump as The absorption liquid is recycled; the flue gas volume of a single series is 200,000 Nm ³ /h, the absorption efficiency is not lower than 99.99%, and the acid concentration of the finished product is not lower than 31%.

The raw material crystalline aluminum salt includes crystalline aluminum chloride hexahydrate, crystalline aluminum sulfate, aluminum ammonium sulfate, aluminum ammonium carbonate and aluminum hydroxide, and the applicable maximum water content is 80%.

The waste heat boiler adopts a horizontal fire tube boiler structure, which has the functions of anti-acid corrosion, anti-dust adhesion and anti-clogging; after the high-temperature flue gas enters the horizontal flue from the inlet of the waste heat boiler, it flows through the slag tube bundle and the evaporation tube bundle in sequence II and evaporator bundle III, the water circulation system adopts a single-drum natural circulation evaporation system; the boiler body adopts a multi-layer lining structure, the part in direct contact with the flue gas is made of corrosion-resistant and wear-resistant heavy castable, and the middle layer is made of high-strength heat-insulating Lightweight castable, the third layer is made of ceramic fiberboard with good thermal insulation effect.

The HCl content in the tail gas is <50mg/Nm ³ , the NOx content is <400mg/Nm ³ , the SO ₂ content is <200mg/Nm ³ , and the smoke dust is <30mg/Nm ³ .

The beneficial effects obtained by the present invention are:

The present invention adopts an overall fully enclosed fluidized integrated roasting furnace, and uses high-temperature flue gas as a heat source to continuously complete the crystalline aluminum salt roasting process; adopts a material crushing and storage feeding and conveying system to realize continuous feeding of crystalline aluminum salt without slagging; Use hot blast furnace to recover flue gas waste heat and control flue gas temperature; use flue gas recirculation system to reduce excess air coefficient; use high-efficiency dry dust collector and waste heat boiler to jointly complete gas-solid separation and waste heat recovery of acid-containing and corrosive flue gas; The fluidized separator and fluidized cooler recover the waste heat of finished alumina and improve product quality; the low-energy pneumatic tower acid recovery system is used to complete the absorption of large flow flue gas and by-product finished acid.

The invention solves the problem of poor integration of roasting equipment, poor continuous operation stability and high energy consumption when the existing multi-stage series cyclone preheats the crystalline aluminum salt; Agglomeration and slagging are prone to occur in the low temperature state; acid low temperature dew point corrosion equipment and other problems. The invention has strong adaptability to the attached water content of crystallized aluminum salt, reasonable energy cascade utilization, which can maximize the energy input into the process system into effective energy, good system regulation and stability, high product purity, and low energy consumption , low investment, small footprint and other obvious advantages. Specifically:

(1) System reliability is improved. Compared with conventional roasting furnaces, the overall fully enclosed fluidized integrated roasting furnace of the present invention has higher heat transfer intensity in the furnace, higher furnace volume heat load, more reasonable temperature field and flue gas flow, reduced heat loss of the furnace body, and improved combustion efficiency. The number of devices is reduced, and maintenance and operation are easy. The equipment structure of the roasting furnace is simple, the processing capacity per unit furnace capacity is large, the floor area is small, and the investment is low.

(2) Continuously complete the crystalline aluminum salt roasting process. The fluidized integrated roasting furnace of the present invention continuously completes a series of physical and chemical evolution processes such as drying and dehydration of crystalline aluminum chloride and crystal transformation. The temperature of the low-temperature roasting section is 350-450°C, and the temperature of the high-temperature roasting section is 850-1050°C, with independent temperature control operation.

(3) It has a wide range of adaptability to crystalline aluminum salts. The material crushing and storage feeding conveying system realizes continuous feeding of crystalline aluminum salt without slagging. The integrated roasting system can meet the demand characteristics of large heat absorption of crystalline aluminum salt reaction, and solve the phenomenon of agglomeration and slagging of crystalline aluminum salt due to the concentrated release of a large amount of crystal water, insufficient and untimely heat energy supply.

(4) The energy consumption of the system is low. Use hot blast furnace to recover flue gas waste heat and control flue gas temperature; use flue gas recirculation system to reduce excess air coefficient; use high-efficiency dry dust collector and waste heat boiler to jointly complete gas-solid separation and waste heat recovery of acid-containing and corrosive flue gas; The fluidized separator and fluidized cooler recover the waste heat of finished alumina and improve product quality; the low-energy pneumatic tower acid recovery system is used to complete the absorption of large flow flue gas and by-product finished acid. Since the calcination temperature is half that of the conventional fluidized bed, the waste heat of the flue gas and the high-temperature alumina particles are recovered in multiple stages to minimize energy consumption; Energy level utilization, the energy consumption of the roasting system is significantly reduced, the fuel consumption is reduced, and the energy consumption per unit of alumina is low;

(5) The product quality is good. The system can adjust the calcination temperature according to the required alumina quality, change the crystal form of the product, remove hydroxyl groups, and obtain qualified products.

Description of drawings

Fig. 1 is the schematic structural diagram of the integrated device for preparing industrial-grade alumina by calcination of crystalline aluminum salt;

In the figure: 1. Raw material; 2. Material crushing and storage feeding conveying system; 3. Feed pipeline; 4. First flue; 5. Fluidized integrated roaster; 6. Second flue; 7. Dry 8. The third flue; 9. Waste heat boiler; 10. The fourth flue; 11. The first hot flue gas pipeline; 12. The first discharge pipeline; 13. The second hot flue gas pipeline; 14 .The second discharge pipeline; 15. Preheating air; 16. Water vapor; 17. Fluidized separator; 18. The first pipeline; 19. Fluidized cooler; 20. The second pipeline; 21. Hot blast stove; 22 .Flue gas recirculation system; 23. Air; 24. Fuel; 25. Hot air pipeline; 26. Third pipeline; 27. Finished alumina packaging system; 28. Valve; 29. Baffle parts; 30. Cyclone separation device; 31. Fourth pipeline; 32. Fifth pipeline; 33. Sixth pipeline; 34. Acid recovery system; 35. Tail gas; 36. Finished acid.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

As shown in Figure 1, an integrated device for preparing industrial-grade alumina by roasting crystalline aluminum salts according to the present invention includes a material crushing and storage feeding and conveying system 2, a fluidized integrated roasting furnace 5, a dry dust collector 7, and waste heat Boiler 9, fluidized separator 17, fluidized cooler 19, hot blast stove 21, flue gas recirculation system 22, finished alumina packaging system 27, cyclone separation device 30 and acid recovery system 34.

The raw material 1 enters the material crushing and storage feeding conveying system 2, and the crushed material enters the fluidized integrated roaster 5 through the multi-channel feeding pipeline 3.

The acid-containing corrosive flue gas and entrained solid particles from the fluidized integrated roaster 5 enter the dry dust collector 7 through the second flue 6, and the solid particles after gas-solid separation enter the fluidized state again through the fourth pipeline 31. The high-temperature section of the integrated roasting furnace 5; the acid-containing corrosive flue gas after gas-solid separation enters the waste heat boiler 9 through the third flue 8 to recover the waste heat of the flue gas, and then enters the acid recovery system 34 through the fourth flue 10, and passes through the system The cooling, washing, and absorption processes recover the by-product acid 36, and the tail gas 35 is discharged up to environmental protection standards.

The solid from the fluidized integrated roaster 5 enters the fluidized separator 17 through the second discharge pipeline 14, and then enters the fluidized cooler 19 through the first pipeline 18. After cooling down, it becomes the product alumina and enters it through the third pipeline 26. The finished alumina packaging system 27 is output outside the system.

The flue gas from the fluidized cooler 19 passes through the second pipeline 20 and part of the acid-containing corrosive flue gas from the dry dust collector 7, enters the flue gas recirculation system 22 through the fifth pipeline 32, and then passes through the The sixth pipeline 33 merges into the hot blast stove 21, and after the fuel 24 and air 23 are burned and heated, the flue gas is sent to the central area of the fluidized integrated roaster 5 through the multi-channel hot blast pipeline 25. After combustion, the high-temperature flue gas fluidization wind enters the fluidized integrated roaster 5 through the first hot flue gas pipeline 11 and the second hot flue gas pipeline 13, providing stable high-temperature fluidized wind for solid fluidization, and the fluidized integrated The lower part of the roasting furnace 5 is provided with a first discharge pipeline 12, which is a discharge channel for solid bed materials and reduces the stock of solid materials in the furnace; preheated air 15 and 0.6MPaG saturated water vapor 16 enter the fluidized separator 17 to form solid Fluidization provides stable low temperature fluidizing wind.

Material crushing and storage feeding conveying system 2 is made of acid-resistant and corrosion-resistant materials, including screw feeding device and pneumatic conveying feeding device, which can continuously convey corrosive solid materials that are easy to deliquesce, easy to agglomerate and harden when heated, and the single-set conveying capacity is 80 tons/hour.

The fluidized integrated roaster 5 adopts an overall fully enclosed fluidized roaster, and uses high-temperature flue gas as a heat source to continuously complete the roasting of crystalline aluminum salts. Continuously complete the crystalline aluminum salt removal of attached water, removal of crystal water, and thermal decomposition process. The appearance is a single round or square equipment, and the interior is a parallel structure of multi-layer circulating fluidized bed and ebullating fluidized bed. It can be designed as a conventional circulating fluidized bed or a suspended fluidized bed. The furnace wall can be adiabatic for the entire furnace lining. Furnace walls or water-cooled furnace walls with water-cooled walls. The low-temperature section on the left adopts a fluidized bed with a high circulation ratio, the operating temperature is 350-450°C, the circulation ratio is 15-25, and the reaction residence time is 10-15 minutes. In the technical process, the crystalline aluminum salt is roasted to remove all free water and crystal water, and all or 80% of it is converted into crude alumina (amorphous state). The high-temperature section on the right adopts a fluidized bed with a low circulation rate, the operating temperature is 850-1050°C, the maximum furnace temperature can be increased to 1500°C, the cycle rate is 1-5, and the reaction residence time is 0.5-2min. The crude alumina in the high-temperature section is transformed into For qualified γ-Al ₂ O ₃ , the process of crystal transformation and gradation adjustment is continuously completed to meet the requirements of metallurgical grade alumina products.

The low-temperature section and the high-temperature section of the fluidized integrated roaster 5 are communicated through the first flue 4 at the top and the valve 28 at the bottom to control the circulation rate respectively. The low-temperature section has a lower dense-phase region and a middle-upper dilute-phase region. Most of the low-temperature section is composed of dilute suspended gas and powder in the dilute-phase region, and the density changes sharply at the boundary of these two phases. Its low-temperature section has multiple sets of baffle parts 29 to control the direction of flue gas flow, which can prolong the reaction residence time, solve the phenomenon of material agglomeration, slagging, insufficient heat supply and untimely supply due to the concentrated release of a large amount of crystal water, and improve Adaptability to attached moisture of crystalline aluminum salts. The crystalline aluminum salt is fed continuously through the feed pipeline 3 at least 1 meter from the feed inlet at the top of the low-temperature section. The acid-containing corrosive flue gas from the hot blast stove 21 is sprayed through the hot blast pipeline 25 from the feed inlet at the junction of the middle and lower part of the low temperature section, the dense phase area and the dilute phase area. The inclination angle is 45-60°, and the number of channels is 4-8. The finished alumina in the high temperature section is continuously discharged through the second discharge pipeline 14 at least 1 meter from the bottom outlet of the high temperature section. The channel is single, and the second discharge pipeline 14 is directly connected to the fluidized separator 17 .

The hot blast stove 21 recovers the waste heat of flue gas. Part of the acid-containing corrosive flue gas from the fluidized cooler 19 and the dry dust collector 7 after dedusting, enters the flue gas recirculation system 22 through the fifth pipeline 32, after being pressurized, it merges into the hot blast stove 21, passes through the air 23 Combustion and heating with the fuel 24, the flue gas with a temperature of 1000±50°C enters the fluidized integrated roaster 5 again to provide heat for the chemical reaction process of the furnace. The hot blast stove 21 has the functions of acid corrosion resistance and solid particle sedimentation and blockage prevention.

The flue gas recirculation system 22 reduces the excess air ratio. Part of the acid-containing and corrosive flue gas after dedusting by the high-efficiency dry dust collector 7 is circulated back to the hot blast stove 21 to participate in combustion, thereby reducing the amount of combustion-supporting air and controlling the temperature of the flue gas at the outlet. The flue gas recirculation system 22 has the functions of acid corrosion resistance and solid dust wear resistance. The flue gas recirculation volume is 40-60%, and the volume content of main components is: O ₂ 1.38%, H ₂ O 30.57%, N ₂ 44.78%, CO ₂ 9.44%, HCL 13.38%, dust 50mg/Nm ³ .

The fluidized separator 17 cools the material and removes the hydroxyl content in the solid to improve product quality. Industrial-grade alumina has strict requirements on the content of hydroxyl groups. Preheated air 15 and 0.6MPaG saturated water vapor 16 enter the fluidized cooler 17 to provide stable low-temperature fluidized air for material cooling, reduce the temperature of alumina and remove hydroxyl groups, and improve product quality.

The acid recovery system 34 completes large-flow flue gas absorption and by-products acid. It adopts a low energy consumption pneumatic tower structure, the flue gas volume of a single series is 200,000 Nm ³ /h, the absorption efficiency is not lower than 99.99%, and the acid concentration of the finished product is not lower than 31%.

The invention is suitable for roasting crystalline aluminum salts with high water content (attached water and crystal water) to prepare industrial-grade alumina. For example: crystalline aluminum chloride hexahydrate, crystalline aluminum sulfate, aluminum ammonium sulfate, aluminum ammonium carbonate, aluminum hydroxide, etc., the applicable maximum moisture content can reach 80%.

The raw material 1 (crystalline aluminum salt) conveyed by the belt trestle enters the material crushing and storage feeding conveying system 2. Under industrial production conditions, since crystalline aluminum salts are easy to absorb water and deliquescence, it is difficult to control the external water content at 10%. High moisture content will greatly increase the heat consumption per unit of product. Therefore, the external water content should be reduced as much as possible and controlled at less than 10% is more appropriate; in addition, the particle size of raw material 1 has an impact on the quality of the product after roasting, and the particle size distribution of the material after crushing is 100-350mm, accounting for 80% is more appropriate. Since corrosive gas overflows during the crushing process of raw material 1, crystalline aluminum salts are prone to deliquescence and agglomeration when heated, the equipment should be made of acid-resistant and corrosion-resistant materials, and corrosion-resistant flexible screw feeding devices and pneumatic conveying feeding devices should be used. Due to the large amount of material conveyed, the conveying capacity of a single set should not be less than 80 tons/hour.

The industrial crystalline aluminum salt is continuously fed into the material crushing and storage feeding conveying 2 through the belt. After storage and crushing, it enters the furnace from the top of the fluidized integrated roasting furnace 5 through the multi-channel feeding pipeline 3, and the uniform distribution ensures that the material is evenly heated. In addition, multi-channel feeding is very beneficial to the stable operation of the roaster, which can prevent accidental shutdown caused by poor feeding. The operating temperature of the low-temperature section of the fluidized integrated roaster 5 is 350-450°C, a fluidized bed with a high circulation rate is adopted, the circulation rate is 15-25, and the reaction residence time is 10-15 minutes. The crystalline aluminum salt is roasted to remove all free water and crystal water. All or 80% of it is converted into crude alumina (amorphous); the acid-containing corrosive flue gas and entrained solid particles pass through the cyclone separation device 30 in the upper part of the high-temperature section for gas-solid separation, and the crude alumina particles are continuously sent into the flow stream The high-temperature section of the state-oriented integrated roaster 5 is converted into qualified γ-Al ₂ O ₃ products after high-temperature roasting at 850-1050°C. The high-temperature section adopts a fluidized bed with a low circulation rate, the circulation rate is 1-5, and the reaction residence time is 0.5 ~2min, continuously complete crystal transformation and gradation adjustment. The operating temperature and reaction residence time of the low-temperature section and high-temperature section are related to the reaction mechanism of the crystalline aluminum salt. Research shows that at a calcination temperature of 360°C, the crystalline aluminum salt can be completely decomposed; at a calcination temperature of 1000°C, it can be completely converted It is γ-Al ₂ O ₃ product.

The low temperature section and the high temperature section are connected through the first flue 4 at the top and the valve 28 at the bottom. The valve 28 can control the circulation rate and adjust the amount of material entering the high temperature section. The low temperature section and the high temperature section have good independent adjustment, and the high temperature smoke from the high temperature section The gas passes through the first flue 4 at the top to directly heat the primary alumina to realize cascaded utilization of energy levels. The fluidized integrated roasting furnace 5 is a single round or square equipment, with a circulating fluidized bed or a suspended fluidized bed inside, and the furnace wall can be a fully lined adiabatic furnace wall or a water-cooled furnace wall with a water-cooled wall. There are multiple sets of baffle parts inside the low-temperature section to control the direction of flue gas flow, which improves the heat transfer intensity in the furnace, prolongs the reaction residence time, and solves the problem of material agglomeration, slagging, insufficient heat supply, and insufficient heat due to the concentrated release of a large amount of crystal water. Timely phenomenon, improving adaptability to moisture attached to crystalline aluminum salts.

The finished alumina is continuously discharged through the discharge port at the bottom of the high temperature section, and enters the fluidized separator 17 through the second discharge pipeline 14 . Since the temperature of the material out of the furnace is relatively high, about 950-1000°C, it is necessary to cool down and eliminate the harmful components entrained in the material. In the present invention, 160°C low-temperature preheating air 15 and 0.6MPaG saturated water vapor 16 are sprayed into the fluidized separator 17 at the same time, and the hydroxyl groups are removed while the fluidized cooling is cooling down. When the temperature is lowered to 80°C, the composition and gradation reach the product standard of industrial metallurgical grade alumina, and the product is sent to the finished alumina packaging system 27 through the third pipeline 26 for output.

The finished alumina prepared by the invention has the characteristics of: γ-Al ₂ O ₃ ≥ 99%, loss of ignition < 0.6%, product average particle size: 60-90μm, residual chlorine and hydroxyl: 0.8wt%.

The acid-containing corrosive flue gas and entrained solid particles from the fluidized integrated roaster 5 enter the dry dust collector 7 through the second flue 6, and the combination of sintered metal and cyclone is adopted, and the separation efficiency is ≥92%. The solid after gas-solid separation is mainly the primary product γ-Al ₂ O ₃ , which can enter the high-temperature section of the fluidized integrated roaster 5 again and be used after secondary roasting. After the gas-solid separation, the acid-containing corrosive flue gas is about 400°C, and enters the waste heat boiler 9 to recover the waste heat of the flue gas. The temperature is reduced to 180°C, and the recovered heat can produce 0.6MPaG saturated water vapor. The waste heat boiler 9 adopts a horizontal fire tube boiler structure, and adopts anti-acid corrosion and anti-dust adhesion and blockage technology and equipment structure. After the high-temperature flue gas enters the horizontal flue from the inlet of the waste heat boiler 9, it flows through the slag tube bundle, evaporation tube bundle II, and evaporation tube bundle III in sequence. The water circulation system adopts a single-drum natural circulation evaporation system; the boiler body adopts a multi-layer lining structure. The part in direct contact with the flue gas is made of corrosion-resistant and wear-resistant heavy castable, the middle layer is made of high-strength heat-insulating light-weight castable, and the third layer is made of ceramic fiber board with good heat insulation effect.

Finally, the acid-containing corrosive flue gas enters the acid recovery system 34 through the fourth flue 10 . The acid recovery system uses a low-energy pneumatic tower to complete large-flow flue gas absorption and by-product acid. In the low-energy pneumatic tower, the acid gas enters from the bottom of the pneumatic tower unit, and under the action of the cyclone, an upward swirling airflow with a certain speed is formed, and the absorption liquid injected from the upper end is supported by repeated rotary cutting, which enhances the mixing. Mixing improves the mass transfer efficiency and achieves the purpose of acid gas absorption and dust collection. Compared with the conventional acid recovery system, the low-energy pneumatic tower has the technical advantages of large flue gas treatment capacity and high absorption efficiency, which can solve the problem that the conventional hydrochloric acid recovery system requires multiple sets of parallel connection, which is not conducive to the balance and distribution of system flow and pressure. Since the dissolution of HCl gas and the condensation of water vapor are both exothermic reactions, the heat released by them is taken away by the circulating cooling water flowing in the shell side of the falling film absorber. Part of the hydrochloric acid coming out of the bottom of the low-energy pneumatic tower is sent to the tertiary acid tank, and most of the rest is sent back to the low-energy pneumatic tower by the acid pump to be recycled as the absorption liquid. The single-series pneumatic deacidification tower can handle 200,000 Nm ³ /h of flue gas, the absorption efficiency is not lower than 99.99%, and the final acid concentration is not lower than 31%. After the cooling, washing and absorption processes of the acid recovery system, the tail gas is guaranteed to meet environmental protection standards, among which: HCl content: <50mg/Nm ³ , NOx content: <400mg/Nm ³ , SO ₂ content: <200mg/Nm ³ , Smoke dust: <30mg/Nm ³ .

The temperature of the flue gas from the fluidized cooler 19 is about 200°C, and a part of the acid-containing and corrosive flue gas from the dry dust collector 7 has a temperature of about 350°C, and enters the flue gas recirculation system 22 through the fifth pipeline 32 to increase After being pressed, they merge into the hot blast stove 21 through the sixth pipeline 33. The hot blast stove 21 adopts a fully enclosed vertical cylindrical furnace structure, the bottom burner burns upwards, and the fuel can be coal gas, natural gas, heavy oil, etc. After being heated by fuel combustion, the flue gas with a temperature of 1000±50°C is sent to the middle area of the fluidized integrated roaster 5 through multiple pipelines. The hot blast stove system can recover the waste heat of the flue gas and precisely control the temperature of the flue gas.

The flue gas recirculation system 22 adopts an acidic and corrosive flue gas circulation fan and supporting system to extract 40% of flue gas with a lower temperature and mix it with combustion air to increase the volume of flue gas and reduce the partial pressure of oxygen to make the combustion flame The temperature is lowered, the combustion speed is suppressed, and the formation of thermal NOx in the combustion process is reduced, thereby reducing the total amount of NOx by 25%. The use of the flue gas recirculation system 22 can reduce the amount of combustion air and reduce the excess air coefficient.

The high-temperature flue gas after fuel combustion enters the fluidized integrated roaster 5 through the pipeline to provide stable high-temperature fluidized air for solid fluidization, and the temperature of the fluidized air is 800-1000°C; the first discharge pipeline 12 is a solid bed The discharge channel of the material can reduce the stock of solid material in the furnace. The preheated air and 0.6MPaG saturated water vapor enter the fluidized cooler 19 to provide a stable low-temperature fluidized air for solid fluidization, reduce the temperature of alumina and remove hydroxyl groups to improve product quality.

Claims (10)

1. a kind of crystallization aluminium salt roasting prepares the integrating device of technical grade aluminium oxide, it is characterised in that：Material crystal aluminium salt enters Material is broken and deposit feed conveying system, broken material enter fluidization by multiple feed pipeline and integrate roaster Low-temperature zone；The flue gas of corrosion containing sour of roaster is integrated from fluidization and entrained solid particle is done by the entrance of the second flue Method deduster, the solid particle after gas solid separation are again introduced into the high temperature section that fluidization integrates roaster through the 4th pipeline；Gas-solid The flue gas of corrosion containing sour after separation enters waste heat boiler Mist heat recovering by third flue, enters using the 4th flue Acid recovery system recycles by-product finished acid, the discharge of tail gas environment protection standard by cooling, washing, absorption technique process；From fluidised form The solid for changing integrated roaster enters fluidisation separator by the second discharge line, enters fluidisation cooling using the first pipeline Device becomes product aluminium oxide and is sent into except finished product aluminium oxide packaging system output system through third pipeline after cooling；Carry out self-fluidized type A containing sour corrosion flue gas part of the flue gas of cooler after the second pipeline and from nonaqueous dust cleaner dedusting, through the 5th pipe After line enters flue gas recirculation system boost, converged into hot-blast stove by the 6th pipeline, after fuel and air combustion heating, Flue gas is sent into fluidization by multichannel hot wind pipeline and integrates roaster central region；High-temperature flue gas fluidized wind after burning is by the One heat smoke pipeline, the second heat smoke pipeline enter fluidization and integrate roaster, for it is solids fluidized provide it is stable high temperature fluidized Wind；Fluidization integrates roaster lower part and is provided with the first discharge line, is the discharge-channel of solid bed material, reduces solid material and exists Storage in stove；160 DEG C of preheated airs and 0.6MPaG saturated steams enter fluidisation separator, and cooling material simultaneously removes solid Middle hydroxy radical content provides stable low temperature fluidized wind to be solids fluidized.

2. crystallization aluminium salt roasting according to claim 1 prepares the integrating device of technical grade aluminium oxide, it is characterised in that：Institute The material stated is broken and deposit feed conveying system uses antiacid corrosion material, including helixes feed equipment and strength to be conveyed to material Device.

3. crystallization aluminium salt roasting according to claim 1 prepares the integrating device of technical grade aluminium oxide, it is characterised in that：Institute The fluidization stated integrates the fluidized roaster that roaster is whole total closed type, and inside is multilayer circulation fluid bed, boiling stream Change bed parallel organization, be designed as regular circulation fluid bed or suspended state fluid bed, furnace wall is the adiabatic furnace wall of full furnace lining or carries The water-cooled furnace wall of water-cooling wall.

4. crystallization aluminium salt roasting according to claim 1 prepares the integrating device of technical grade aluminium oxide, it is characterised in that：Institute It includes low-temperature zone and high temperature section, the valve of low-temperature zone and high temperature section through top the first flue and bottom that the fluidization stated, which integrates roaster, The couplet on the door is logical, and valve control loop multiplying power simultaneously adjusts inventory into high temperature section, and the high-temperature flue gas from high temperature section passes through top First flue directly heats first product aluminium oxide, realizes the cascade utilization of energy level；The low-temperature zone in left side is fluidized using high circulation multiplying power It is de- to be continuously finished crystallization aluminium salt by bed, 350~450 DEG C of operation temperature, circulating ratio 15~25,10~15min of reaction time Attachment removal water sloughs the crystallization water, thermal decomposition process process, the whole free waters of crystallization aluminium salt roasting abjection and the crystallization water, all or 80% is converted into crude product aluminium oxide；The high temperature section on right side uses low circulation multiplying power fluid bed, upper part to be provided with cyclonic separation dress It sets, the flue gas of corrosion containing sour and entrained solid particle are after cyclone separator gas solid separation, crude product alumina particle quilt It is continuously introduced into high temperature section, high temperature section operation temperature is 850~1050 DEG C, and highest fire box temperature can be increased to 1500 DEG C, cycle Multiplying power 1~5,0.5~2min of reaction time convert crude product aluminium oxide to qualified γ-Al₂O₃, it is continuously finished crystal form and turns Become, grading adjusting technical process, reaches metallurgical-grade aluminum oxide product requirement.

5. crystallization aluminium salt roasting according to claim 4 prepares the integrating device of technical grade aluminium oxide, it is characterised in that：Institute The fluidization stated integrates the dilute-phase zone of concentrated phase area and middle and upper part of the low-temperature zone with lower part of roaster, and dilute-phase zone is hanged by thin Floating gas and powder constituent, in the boundary density change dramatically of two phases；There is multigroup control flue gas flow direction inside low-temperature zone Baffling component；The flue gas of corrosion containing sour from hot-blast stove passes through hot wind pipeline from the middle and lower part concentrated phase area of low-temperature zone and dilute phase The feed inlet of area's intersection sprays into, and there are one upward with vertical direction in 45~60 ° of inclination angle, number of channels 4 for feed inlet ~8；Finished product aluminium oxide is by high temperature section bottom discharge mouth through the second discharge line continuous discharge.

6. crystallization aluminium salt roasting according to claim 1 prepares the integrating device of technical grade aluminium oxide, it is characterised in that：Institute The flue gas recirculation system stated uses flue gas recirculation blower fan and corollary system, reduces combustion-supporting air quantity, reduces excess air coefficient, Have the function of acid corrosion-resistant, the abrasion of anti-solid dust；Flue gas recirculation amount 40~60%, component volume content accounting：O₂It accounts for Than 1.38%, H₂O accountings 30.57%, N₂Accounting 44.78%, CO₂Accounting 9.44%, HCL accountings 13.38%, dust 50mg/ Nm³。

7. crystallization aluminium salt roasting according to claim 1 prepares the integrating device of technical grade aluminium oxide, it is characterised in that：Institute The acid recovery system stated uses the pneumatic tower structure of low energy consumption, enters below pneumatic tower containing acid gas, under the action of cyclone, shape At the upward swirling eddy with certain speed, rotary-cut repeatedly is held with the absorbing liquid of upper end injection, enhancing blending reaches acid The purpose of aspiration, dust catching；The hydrochloric acid come out by the pneumatic tower bottom of low energy consumption, a part are sent to three-level acid tank, remaining is big Part is recycled by the sour pneumatic tower of pumped back low energy consumption as absorbing liquid；The processing of single series exhaust gas volumn is 200,000 Nm³/ h inhales Rate of producing effects is not less than 99.99%, and finished product acid concentration is not less than 31%.

8. crystallization aluminium salt roasting according to claim 1 prepares the integrating device of technical grade aluminium oxide, it is characterised in that：Institute The material crystal aluminium salt stated includes six water crystallization aluminium chloride, crystalline sulfuric acid aluminium, alum, aluminium carbonate ammonium and aluminium hydroxide, is fitted Highest moisture content is 80%.

9. crystallization aluminium salt roasting according to claim 1 prepares the integrating device of technical grade aluminium oxide, it is characterised in that：Institute The waste heat boiler stated uses horizontal tubular boiler structure, has the anti-dust bonding of acid-proof burn into and anti-blockage function；High-temperature flue gas After the import of waste heat boiler enters horizontal flue, followed followed by Crust blocks pipe bundle, steam-generating bank II and steam-generating bank III, water Loop system uses the vapo(u)rization system of single drum Natural Circulation；Boiler body uses multilayer lining structure, and portion is in direct contact with flue gas The heavy castable using corrosion-proof wear, middle layer is divided to use the lightening casting material of high-strength heat-insulating, third layer, which uses, to be had well The ceramic beaverboard of heat insulation.

10. crystallization aluminium salt roasting according to claim 1 prepares the integrating device of technical grade aluminium oxide, it is characterised in that： HCl contents in the tail gas<50mg/Nm³, NOx content<400mg/Nm³, SO₂Content<200mg/Nm³, flue dust<30mg/Nm³。