CN108083305B - System and process for recovering aluminum hydroxide from mold-stewing liquid - Google Patents
System and process for recovering aluminum hydroxide from mold-stewing liquid Download PDFInfo
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- CN108083305B CN108083305B CN201711471631.1A CN201711471631A CN108083305B CN 108083305 B CN108083305 B CN 108083305B CN 201711471631 A CN201711471631 A CN 201711471631A CN 108083305 B CN108083305 B CN 108083305B
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Abstract
The invention relates to a system for recovering aluminum hydroxide from a die-cooking liquid, which comprises a die-cooking liquid collecting system, a die-cooking liquid processing system, a die-cooking liquid separating system and a die-cooking liquid water re-reaction recovering system; the die cavity liquid collecting system comprises a die cavity liquid recovery tank and a first pump; the mould stewing liquid collecting system is used for collecting mould stewing liquid; the mold boiling liquid treatment system comprises a reaction tank, a second pump and an aluminum hydroxide crystal seed storage tank; the die-stewing liquid treatment system is used for carrying out chemical reaction on the die-stewing liquid and producing aluminum hydroxide; the mold boiling liquid separation system comprises a recovery tank and a centrifuge; the mold boiling liquid water re-reaction recovery system comprises a wastewater recovery tank and a third pump; the die-stewing liquid water re-reaction recovery system is used for recovering and treating the wastewater after solid-liquid separation; the invention utilizes the mold-stewing liquid to recover sodium hydroxide, improves the recovery utilization rate of the aluminum industry waste residue, and solves the problem of easy scaling.
Description
Technical Field
The invention relates to the technical field of aluminum processing, in particular to a system and a process for recovering aluminum hydroxide from mold-stewing liquid.
Background
The aluminum and the aluminum alloy have the advantages of excellent processing performance, good corrosion resistance, beautiful surface, high recovery rate and the like, are widely applied to the industries of buildings, transportation, machinery, electric power and the like, and have more obvious trend of expanding the application of the aluminum by replacing the steel with the aluminum in recent years. The aluminum processing industry is a traditional industry, and more particularly, the sunrise industry which is full of bobby vitality. According to statistics, developed countries in Europe and America consume more than 32kg of aluminum materials per year, but China only has about 13kg of aluminum materials per year and is only about one third of developed countries, and domestic aluminum material consumption has huge growth space, but under the new economic normal state, the problems of high energy consumption, large total pollution discharge amount and low resource recovery rate also become bottlenecks and obstacles for industry development.
The production in the aluminum industry comprises the working procedures of electrolysis, casting, pressure processing, surface treatment and the like, and waste water and waste residues are generated in different degrees in all the working procedures during production. A large amount of aluminum ash is generated during electrolysis and casting, alkaline waste liquid of a die is produced in the extrusion process, and various waste water and waste residues containing acid, alkali, treatment agents, chromium, nickel heavy metal ions and other complex components are generated in the surface treatment process.
One, waste residue source in aluminum industry
1. Electrolytic casting of aluminium ash
The aluminum ash is generated in the processes of electrolysis, smelting and casting of aluminum and aluminum alloy, and the total loss of aluminum caused by the aluminum ash is 1-12%. About 20-40kg of aluminum ash is generated when one ton of raw aluminum is processed, the amount of aluminum liquid generated during direct casting is less, the amount of aluminum ingot is more during remelting, and about 100-250kg of aluminum ash is generated during regeneration of one ton of waste aluminum. The aluminum ash can be divided into two types: one is primary aluminum ash, which is scum and skimming produced in the processes of electrolyzing raw aluminum, casting and the like without adding salt flux, and the like, and mainly comprises metal aluminum and aluminum oxide, wherein the content of aluminum can reach 15-70 percent, and the color is white; the other is secondary aluminum ash, which is the waste after the primary aluminum ash is subjected to aluminum extraction and recovery, and the aluminum content is lower than that of the primary aluminum ash, and the secondary aluminum ash is generally gray black. The secondary aluminum ash has complex components and contains toxic and harmful components such as metallic aluminum (5-30%), aluminum oxide (30-70%), silicon dioxide and ferric oxide (5-15%), potassium, sodium, calcium and magnesium chloride (10-30%) and nitrogen, fluorine, arsenic and the like.
The national electrolytic aluminum yield is 3250 ten thousand tons in 2016, the aluminum product yield of extrusion and calendering exceeds 2000 ten thousand tons, the conservative estimation of the aluminum ash amount in the whole country every year is more than 200 ten thousand tons, and the total amount of the aluminum ash is considered to be 850 ten thousand tons in 600 days. The aluminum ash is a renewable resource and has higher comprehensive recycling value, but the aluminum ash is not paid enough attention all the time, so that huge resource waste is caused. Meanwhile, the aluminum ash contains toxic and harmful substances such as fluoride, ammonia nitrogen, arsenic and the like, and is classified as dangerous waste, the waste category of the aluminum ash in 'national dangerous waste record' of 2016 edition is HW48, and the dangerous characteristic T (danger) -toxic dangerous waste. Along with the development of economy, the accumulation amount of the waste aluminum ash is greatly increased year by year, and if an economical, effective and harmless method is not found for treatment, the serious threat to the environment is more and more highlighted. At present, the recovery of the aluminum ash in China is still in a starting stage, a recovery method which is mature, reliable and good in economical efficiency is lacked, the aluminum ash treatment recovery rate is low, the energy consumption and the waste are large, and the utilization approaches are few. Even if the treated aluminum ash still contains a large amount of harmful substances, the aluminum ash can be only stockpiled or buried in a yard, so that the method has great environmental hazard and simultaneously a manufacturer bears great illegal risks. In 2018, the environmental protection tax Law of the people's republic of China, which is applied from 1 month and 1 day, stipulates that an aluminum ash emission enterprise will pay an environmental protection tax of 1000 yuan/ton.
2. Extrusion surface treatment of waste water and waste residue
The production of aluminum products consumes a large amount of water, at least 15 tons of water are consumed for producing 1 ton of aluminum materials, 1000 ten thousand tons of extruded materials are produced in the whole industry every year, nearly 3 hundred million tons of waste water are discharged, about 300 ten thousand tons of waste residues are produced after the waste water is treated, and the quantity is extremely remarkable.
2.1 extruding the waste liquid, waste water and waste residue of the pot mold
After the aluminum profile extrusion die is used, the aluminum profile extrusion die is put into high-concentration alkali liquor to be die-stewed, and aluminum in a die cavity is corroded. The concentration of sodium hydroxide in the mold-boiling liquid reaches 250-350g/L, the content of aluminum ions is continuously increased along with the reaction, and when the concentration reaches above 60-70g/L and the reaction speed is obviously reduced, the mold-boiling liquid needs to be discharged. The discharged waste liquid contains a large amount of aluminum ions and sodium hydroxide, and the potential economic value is very high. The treatment of the waste liquid of the die-stewing generally adopts a mode of treating waste by waste: the waste acid generated in the oxidation process is neutralized, the amount of waste residues generated by the treatment mode is very large, and the die-cooking waste residues can account for about 30% of the total amount of the slag of an enterprise. Enterprises do not utilize the economic value of the waste water, but increase the cost, and the treatment of waste water and waste residue becomes a heavy burden for environmental protection.
2.2 surface treatment of waste Water and slag
Aluminum materials are subjected to surface treatment in order to enhance corrosion resistance and decorative properties. Common surface treatment methods include anodic oxidation coloring, electrocoating, powder spraying, fluorocarbon paint spraying, and the like. The surface treatment process produces large amounts of wastewater of complex composition.
The waste water and waste residue of the anodic oxidation and electrophoretic painting processes are divided according to the processes as follows: the alkaline waste water and waste residue generated by the alkaline etching solution account for 20 percent of the total residue; acid waste water and waste residues generated by the oxidation liquid account for 30 percent of the total residue; the acid waste water and waste residue produced in the spraying procedure account for 20 percent of the total residue. The aluminum slag source of the wastewater center of the aluminum processing enterprise is subdivided into: the mold-stewing liquid caustic sludge accounts for 30% of the total slag, the caustic etching liquid caustic sludge accounts for 20% of the total slag, the oxidizing liquid acid sludge accounts for 30% of the total slag, and the spraying acid waste residue accounts for 20% of the total slag.
The wastewater contains cations such as Al3+, Na +, NH4+, Ni2+, Sn2+, Cr6+ and the like, anions such as SO42-, F-, NO3-, NO2-, S2-, Cl-and the like, and organic matters such as organic phenol, a surfactant, acrylic resin and the like. The acidic waste water and the alkaline waste water are usually mixed for post-treatment, while the chromium-containing waste water and the nickel-containing waste water must be treated separately. In recent years, the proportion of the oxidation electrophoresis material is reduced, but most aluminum material factories still have more acidic wastewater than alkaline wastewater, acid and alkali water are all mixed together for treatment, the wastewater is acidic after being mixed, a large amount of caustic soda flakes, lime, PAC and PAM are required to be added, and a large amount of waste residues are generated.
The latest version of the national records of dangerous wastes, which was applied from 8.1.2016, has recorded the records of acidic and alkaline waste water and waste residues in the records of HW34 and HW 35. According to the stipulation of the environmental protection tax Law of the people's republic of China, which is executed from 1 month and 1 day in 2018, an enterprise must pay 1000 yuan/ton of wastewater treatment sludge environmental protection tax.
The recycling rate of water in the current aluminum processing industry is less than 30%, and a large amount of waste residues are generated after wastewater treatment. On one hand, a large amount of useful resources such as metallic aluminum, acid, alkali and the like in the waste residue are not utilized, and huge resource waste is caused. The waste residue belongs to dangerous waste and has great environmental hazard. At present, the situation forces enterprises to change the development to the direction of energy conservation, emission reduction and resource recycling, but the enterprises lack a mature and reliable technology. Zero discharge of waste water, zero output of waste residues and maximum resource utilization value are realized, and the method has great environmental benefit, social benefit and economic benefit.
Second, the current situation of treatment and utilization of waste slag in aluminum industry
1. Electrolytic casting aluminum ash treatment and utilization status
Many methods for recycling and resource utilization of aluminum ash are developed at home and abroad successively, and in recent years, patents on recycling of aluminum ash are on the rise, but most of the aluminum ash are in experimental research stage, and the technology is limited to the aspects of extracting metal aluminum under high temperature condition, preparing inorganic materials such as aluminum oxide, aluminum chloride and aluminum sulfate and steelmaking auxiliary materials, and the like, and has a certain distance from industrialization and large-scale production.
1.1 aluminum ash recovery
The existing methods for recovering aluminum ash can be divided into a heat treatment method and a cold treatment method, and only metal aluminum in the aluminum ash is recovered. A large-scale domestic regenerated aluminum plant adopts a tilting rotary kiln treatment method: aluminum ash and additive salts (usually a mixture of sodium chloride, potassium chloride and a small amount of calcium fluoride) are placed in a tilting rotary kiln to be heated and then metal aluminum is separated, but smoke is generated in the recovery process, the metal recovery rate is low, the residual aluminum content in the aluminum ash is high, and further recovery space is still left. The manual ash frying method in a small workshop is also widely adopted, and the method is open-type operation and generates a large amount of dust and smoke. Other methods include press recovery, plasma dissolution, electric separation, MRM, and ALUREC.
1.2 comprehensive utilization of aluminum ash
Because the components of the aluminum ash are basically consistent with those of bauxite, the products produced by the bauxite are subjected to experimental research by using the aluminum ash. Currently, there are three main routes in resource utilization of aluminum ash: (1) the recovered alumina is returned to electrolysis, and the recovered chloride salt is used as a casting refining agent, but the main component in the aluminum ash is alpha-Al 2O3, the activity is poor, and more energy is consumed for ionizing the aluminum ash, so that the voltage of the cell is increased. (2) Acid method or alkali method for removing impurity, producing synthetic brown corundum, Sialon ceramic and refractory material, etc. inorganic material, producing polyaluminium chloride, aluminium sulfate and other water purifying material, and producing slag-forming desulfurizer for steel-making. (3) The production of building materials or road building materials, such as aluminate cement, calcium aluminate powder, ganged bricks, road building materials and the like, but the performance is influenced by the contained fluoride and chloride, and the added value of the product is low, so that the practical application is limited. The applications of the three aspects all have the defects of low product purity, low added value, secondary pollution of waste and the like. The waste after the aluminum ash is recycled still contains a large amount of soluble salts and fluorides, is dangerous waste and can be only buried or stacked, and the environmental hazard is not reduced.
Because the aluminum ash contains a certain amount of components such as chloride (NaCl, KCl and the like) and fluoride with high temperature resistance, corrosion resistance, toxicity and the like, the conventional method is difficult to realize the recycling of all components, the resource cost and the technical difficulty of the aluminum ash are increased, and the industrialization of the aluminum ash treatment is slowly progressed. In addition, the migration and transformation mechanism of harmful elements such as fluorine and heavy metals in the aluminum ash treatment process is not further discussed.
Under the conditions of resource shortage and increasingly serious environmental pollution, the development of the aluminum processing industry faces huge pressure on resources and environment, energy conservation, emission reduction and resource recycling, and the method is a development direction and a unique outlet in the future. In order to realize zero waste of the aluminum ash resource, the resource utilization idea must be changed, various components in the aluminum ash are fully utilized, and harmless treatment and resource maximized utilization are carried out. The work is urgent, needs to be oriented clearly, guided in a standard way and cooperated in multiple ways, and strives to make a real-time breakthrough in the early days.
2. Extrusion surface treatment wastewater and waste residue treatment and utilization status
1. The recovery treatment of waste water and waste residue, comprehensive utilization comprises two aspects: firstly, water is recycled; and secondly, the resource of the waste residue is comprehensively utilized.
1.1 extrusion die-stewing liquid and recovery of alkaline etching liquid before oxidation treatment
The extrusion die-cooking liquid contains a large amount of sodium hydroxide and aluminum ions, and a lot of research reports and patents exist in the aspect of die-cooking liquid recovery, such as a Crystalfix alkali recovery system in Italy, but the practical application is not many due to the complex flow and low comprehensive benefit. The current method for treating the die-cooking waste liquid in the aluminum processing enterprises is as follows: the mold-stewing wastewater and waste acid generated in the oxidation process are neutralized and precipitated for post-treatment slag making, and waste residues generated by mold-stewing liquid account for about 30 percent of the total slag amount of an enterprise. Enterprises do not recycle sodium hydroxide, aluminum ions and other useful resources in the mold-cooking liquid, but increase the cost, and the treatment of waste water and waste residues becomes a heavy burden on environmental protection.
The recovery of the oxidation pretreatment alkaline etching solution generally adopts a crystallization method to recover sodium hydroxide, but the sodium hydroxide has the advantages of fine granularity, low purity and low economic value. In addition, the crystallization method keeps the aluminum ions at a low concentration (less than 30g/L), which is easy to cause defects of coarse crystals, coarse sand, over corrosion and the like of the section bar, and the aluminum consumption is too high. The crystallization method has high requirements on operation and process, can precipitate and scale when being not managed well, can only stop production and clean manually at the moment, and is time-consuming and labor-consuming. A small number of manufacturers put on online alkali recovery devices, and most of the devices are abandoned due to poor recovery effect and high cost. The alkaline etching bath solution added with the corrosion inhibitor and the complexing agent is not suitable for an alkaline recovery device, and the application of the technology is also limited.
1.2 recovery of alumina ions and sulfuric acid from the oxidized liquid
The aluminum ions in the aluminum alloy anodic oxidation solution directly influence the conductivity and the film quality of the bath solution, and the optimal control concentration is within the range of 3-10 g/L. The aluminum ions are accumulated and increased along with the increase of the production quantity, the quality of a film layer is poor, and the power consumption is increased, but the aluminum ion concentration in the actual production of an enterprise is generally controlled within the range of 15-20g/L in consideration of the medicament cost and the environmental protection pressure. After reaching the upper limit, the aluminum ion content must be reduced. The common practice for reducing aluminum ions is to discharge half of the bath solution and continue production after sulfuric acid is replenished. The method is simple, but has the following defects: firstly, sulfuric acid is lost, aluminum ions are wasted, and the consumption of the sulfuric acid reaches more than 60 kg/t; secondly, the waste acid treatment increases considerable cost; thirdly, a great amount of waste residue causes environmental harm.
Sulfuric acid reclaimers that employ the principle of diffusion dialysis have been widely used as a means of controlling aluminum ions. The sulfuric acid recovery machine is a stabilizing device for aluminum ions, and the aim of recovering sulfuric acid and removing aluminum ions is fulfilled by adopting a diffusion dialysis ion exchange membrane. In actual operation, the method has the defects of poor recovery effect, high energy consumption, low efficiency, no reduction of slag quantity and the like. In view of the above-mentioned poor utilization of the sulfuric acid reclaimer, most aluminum processing enterprises have gradually stopped the plant, restoring the traditional method of inverting half of the oxidation bath.
1.3 spray pretreatment wastewater recovery
The market share of powder spray coated aluminum alloy products has increased significantly in recent years, now accounting for over 60% of aluminum alloy surface treated products. The purpose of the spraying surface pretreatment is to generate a layer of compact conversion coating on the surface of the aluminum material and firmly bond the base material and the spraying layer together. In order to ensure the quality of the conversion film, the process control requirement is very strict, and the over-standard bath solution and rinsing water must be drained. The waste water is acidic and contains a large amount of hexavalent chromium, fluotitanic acid, fluozirconate and fluorinion. The treatment of a large amount of waste acid not only increases the enterprise cost, but also wastes resources, and has environmental hazard. The spraying pretreatment and wastewater treatment technology has no obvious progress, and a traditional method is still adopted to form a large amount of waste residues after neutralization, precipitation, filter pressing and dehydration. Waste residues belong to strictly controlled hazardous wastes and must be transferred to qualified third parties for standardized harmless treatment.
1.4 chromium-and nickel-containing waste water
Chromium and nickel belong to a class of pollutants, chromium-containing or nickel-containing wastewater must be separately treated, and chromium slag (HW21) and nickel slag (HW17) belong to dangerous wastes.
The recovery of hexavalent chromium ions is still a difficult problem, and the online recovery of chromium-containing medicaments cannot be realized. The current treatment method of the chromium-containing wastewater comprises the following steps: adding reducing agents such as sodium pyrosulfite or sodium bisulfite and the like to reduce hexavalent chromium into trivalent chromium with lower toxicity, then adding alkali and PAM to perform reaction precipitation, and dehydrating and filter-pressing sludge to obtain chromium slag.
The recovery of nickel ions is only limited to a coloring tank, and the nickel ions in the hole sealing wastewater are directly discharged due to low content. The recovery of nickel ions adopts an RO recovery device, the principle is the same as that of acid recovery, and the device is used by part of manufacturers, but the efficiency is low, and a large amount of concentrated water is generated, so that the effect is not ideal. The nickel-containing wastewater is treated by a precipitation method, sodium hydroxide and PAM are added, the pH is adjusted, nickel hydroxide precipitate is generated by reaction, and the nickel slag is obtained after sludge dehydration and filter pressing.
1.5 extrusion surface treatment wastewater and waste residue comprehensive treatment
Many aluminum section manufacturers actively explore and practice in many aspects in the aspects of water saving and waste water treatment, and obtain certain effect. At present, the waste water in the aluminum processing industry is still treated by adopting a neutralization regulation and coagulating sedimentation method, and the treatment process comprises the following steps: the acid-base waste water is neutralized, the pH is adjusted to be neutral, and cation Al3+ and the like form hydroxide precipitates. And (3) pumping the neutralized and precipitated wastewater into a coagulation tank, adding flocculating agents PAC and PAM, flocculating, then entering the precipitation tank, discharging or recycling clear liquid after reaching the standard, and performing filter pressing on the water-containing sludge by a filter press to form aluminum-containing waste residues. The water content of the waste residue is about 80 percent, and the quantity is very large.
The traditional waste water and waste residue treatment mode has the following defects: firstly, the wastewater can reach the standard after being treated, but the reuse rate of reclaimed water is low; secondly, the wastewater treatment cost is high, and the consumption of manpower, medicament and power is increased; thirdly, a large amount of useful resources such as acid, alkali, metal aluminum, chemical agents and the like are wasted; fourthly, the waste residue belongs to dangerous waste, the disposal cost is high, and environmental protection tax needs to be paid.
2. Comprehensive utilization of waste water and waste residue in extrusion surface treatment
The comprehensive utilization comprises two aspects: firstly, water is recycled; and secondly, the resource of the waste residue is comprehensively utilized. The recycling status is not ideal, and the recycling rate of water is less than 30%, and the ways and methods for comprehensively utilizing the aluminum slag, the chromium slag and the nickel slag are limited.
2.1 comprehensive utilization of aluminum slag
The resource utilization research of the aluminum-containing waste residue has been carried out for many years, and a plurality of articles and patent technologies exist, and the technical path of resource utilization is basically the same as that of aluminum ash, and the resource utilization mainly comprises the following aspects: (1) directly recovering aluminum hydroxide or aluminum oxide; (2) synthesizing ceramics or refractory materials such as mullite, cordierite, ceramic frit, artificial resin marble and the like; (3) producing water purification materials such as calcium aluminate, polyaluminum chloride (iron), polyaluminum sulfate, and the like; (4) for example, Chinese patent CN 1350065A discloses a method for preparing ammonium aluminum sulfate, aluminum sulfate and aluminum hydroxide by using alkaline residue, Chinese patent CN101186282B discloses a method for reducing aluminum ions and preparing ammonium alum by using hard oxidized sulfuric acid tank liquor, and Chinese patent CN1319302C discloses a method for preparing cryolite by using fluorine-containing acid residue.
Except for the successful application of the technology for preparing the cryolite by utilizing the acid sludge, most other methods are not applied in scale, the comprehensive utilization rate of the aluminum slag is very low, and the main reasons are that the technology is immature, the added value of the product is low and the cost is high. Most of waste residues are paid and disposed by aluminum material factories, and the waste residues of a plurality of aluminum material factories are accumulated like a mountain at present, so that the blanched Chinese yam of the aluminum material factories is formed.
2.2 comprehensive utilization of chromium slag and nickel slag
The chromium slag is disclosed to be useful as a glass colorant and a crystallization accelerator, but the practical application is not described in detail. No public data of nickel slag resource utilization is found. The current method for the chromium slag and the nickel slag is to transfer to a third party organization for harmless burying treatment.
3. The extrusion surface treatment of waste water and waste residue has problems
Firstly, the water consumption is high, a mature water-saving technology is lacked, and the water reuse rate is low; secondly, the waste water is classified on line and cannot become a preposed program, so that the waste residue generation amount is large; thirdly, the comprehensive utilization effect of the waste residue is not large, and the waste residue treatment becomes the burden of enterprises and the environmental protection risk.
Currently, there are three outstanding contradictions and problems with waste residue treatment: firstly, the country manages the pollutant discharge license of the enterprise and controls the total pollutant discharge amount of the enterprise, and the actual waste water and waste residue amount of the enterprise is far larger than the allowable discharge amount; secondly, the waste residue must be legally transferred to a qualified third party for disposal, but the disposal capability is obviously insufficient, so that the huge amount of waste residue cannot be legally treated; thirdly, waste residues are treated according to dangerous waste specifications, the process is complex, the efficiency is low, and the cost is high.
In summary, the treatment of waste water and waste residue in the domestic aluminum processing industry at present is contradictory, the comprehensive treatment difficulty is high, the cost is high, the recovery rate is low, the resource waste is caused, and the environment pollution is serious. Therefore, for the aluminum processing industry, the method has wide prospect and huge environmental benefit, social benefit and economic benefit for research, development, popularization and application of wastewater zero discharge and resource comprehensive utilization technology.
Third, aluminum ash and aluminum slag reduction and resource direction in aluminum industry
1. The principle followed is: the reduction control, the harmless treatment and the resource utilization can be actively developed only by combining three forces of government promotion, enterprise dominance and third party market allocation resources;
2. source control, namely classification interception, on-line conversion and resource utilization of each medicament tank, and reduction of the discharge amount of waste water and waste residue;
3. the environment-friendly surface treatment technology is popularized and applied. Aiming at the pollution problem of the oxidation line, the technology of additive-free alkaline etching, nickel-free fluorine-free hole sealing and the like is popularized and applied;
4. and the production and research combination is strengthened, the thought and the field of comprehensive utilization of waste residues are expanded, and the maximum comprehensive utilization value is realized.
Disclosure of Invention
The invention aims to provide a system and a process for recovering aluminum hydroxide from a mold-stewing liquid, which are used for recovering aluminum hydroxide and are not easy to scale, aiming at the defects in the prior art.
In order to achieve the purpose, the invention adopts the following technical scheme:
a system for recovering aluminum hydroxide from a die-cooking liquid comprises a die-cooking liquid collecting system, a die-cooking liquid processing system, a die-cooking liquid separating system and a die-cooking liquid water re-reaction recovering system;
the die cavity liquid collecting system comprises a die cavity liquid recovery tank and a first pump; the mould stewing liquid collecting system is used for collecting mould stewing liquid;
the mold boiling liquid treatment system comprises a reaction tank, a second pump and an aluminum hydroxide crystal seed storage tank; the die-stewing liquid treatment system is used for carrying out chemical reaction on the die-stewing liquid and producing aluminum hydroxide;
the mold boiling liquid separation system comprises a recovery tank and a centrifuge; the die-filling liquid separation system is used for carrying out solid-liquid separation on the produced aluminum hydroxide;
the mold boiling liquid water re-reaction recovery system comprises a wastewater recovery tank and a third pump; the die-stewing liquid water re-reaction recovery system is used for recovering and treating the wastewater after solid-liquid separation;
the die-stewing liquid recovery tank, the first pump, the second pump of the reaction tank and the recovery tank are communicated in sequence through pipelines; the reaction tank comprises a first reaction tank and a second reaction tank; the first pump is communicated with the first reaction tank and the second reaction tank through a pipeline with a first valve and a pipeline with a second valve respectively; the outlet of the second pump is communicated with the tops of the first reaction tank and the second reaction tank through another pipeline; communicating with the centrifuge through an outlet of the recovery tank; a twenty-two valve is arranged between the die-stewing liquid recovery tank and the first pump; a ninth valve is arranged between the first reaction tank and the second reaction tank and between the second pump; a sixteen-number valve is arranged at an inlet of the recovery tank; a seventeen valve is arranged between the recovery tank and the centrifuge; and the aluminum hydroxide crystal seed storage tank is communicated with the second pump through a pipeline provided with a No. ten valve.
The inlet of the waste water recovery tank is communicated with the centrifuge through a pipeline; the bottom of the wastewater recovery tank is communicated with the third pump through a pipeline provided with a nineteen-valve; the middle part of the wastewater recovery tank is communicated with the third pump through a pipeline provided with an eighteen-type valve; the third pump is communicated with the first reaction tank through a pipeline provided with a twenty-first valve; the third pump is communicated with the die cavity of the pot through another pipeline provided with a twenty-valve; the bottoms of the first reaction tank and the second reaction tank are communicated with the second pump through pipelines; a seventh valve is arranged at the bottom of the first reaction tank; an eighth valve is arranged at the bottom of the second reaction tank; the ninth valve is arranged close to the second pump; the first reaction tank is communicated with the second pump through a pipeline provided with a third valve and a pipeline provided with a fifth valve respectively; the second reaction tank is communicated with the second pump through a pipeline provided with a fourth valve and a pipeline provided with a sixth valve respectively; the second pump is communicated with the wastewater recovery tank through a pipeline, a twelve-position valve is arranged at a position close to the second pump, and a fifteen-position valve is arranged at a position close to the wastewater recovery tank; the second pump is respectively communicated with the first reaction tank and the second reaction tank through another pipeline, an eleven-numbered valve is arranged at a position close to the second pump, a thirteen-numbered valve is arranged at a position close to the first reaction tank, and a fourteen-numbered valve is arranged at a position close to the second reaction tank.
In a further aspect, the claimed system for producing aluminum hydroxide from mold-stewing liquid is characterized in that: overflow pipes for preventing the mold boiling liquid from overflowing are arranged above the first reaction tank and the second reaction tank; the overflow pipe is communicated with the wastewater recovery tank.
In a further description, stirrers are arranged in the first reaction tank, the second reaction tank, the recovery tank and the wastewater recovery tank.
The process for recovering aluminum hydroxide from mold stewing liquid comprises the following steps:
the method comprises the following steps: opening the twenty-two valve, the first valve and the second valve, closing the third valve, the fourth valve, the fifth valve, the sixth valve, the seventh valve and the eighth valve, starting the first pump, pumping the mold stewing liquid to be treated into the first reaction tank and the second reaction tank, and finishing the operation of a mold stewing liquid collecting system;
step two: closing the third valve, the fourth valve, the fifth valve, the sixth valve, the eighth valve, the tenth valve, the twelfth valve and the fourteenth valve; opening the seventh valve, the ninth valve, the eleventh valve and the thirteenth valve, starting the second pump, and circulating the mold stewing liquid to be treated; opening a No. ten valve under the condition that a second pump keeps large circulation of the mold stewing liquid to be treated, and sucking the aluminum hydroxide seed crystal into the first reaction tank by utilizing negative pressure for reaction; adjusting a valve switch, and sucking aluminum hydroxide seed crystals into the second reaction tank by using negative pressure in the same way to perform reaction;
step three: opening a third valve or a fifth valve, opening a ninth valve, a twelfth valve and a fifteenth valve, and putting the supernatant in the first reaction tank into the wastewater recovery tank; closing the No. eleven valve, the No. fifteen valve and the No. seventeen valve; opening the No. seven valve and the No. sixteen valve; starting a second pump, and pumping the solid-liquid mixture in the first reaction tank into the recovery tank; starting the electric centrifugal machine; opening a seventeen valve, performing solid-liquid separation on aluminum hydroxide, and conveying the recovered liquid to a wastewater recovery tank; adjusting a valve switch, and separating the aluminum hydroxide and the liquid in the second reaction tank in the same way;
step four: closing a No. fifteen valve, a No. eighteen valve and a No. nineteen valve, and recycling the wastewater into the wastewater recycling tank; closing the valve No. fifteen, the valve No. nineteen and the valve No. twenty-one, opening the valve No. eighteen and the valve No. twenty, starting the pump No. three, and sending the supernatant back to the die cavity; closing the eighteen valve and the twenty valve; opening a nineteen valve and a twenty-first valve; starting a third pump, and sending the solid-liquid mixture of the aluminum hydroxide back to the first reaction tank for recycling;
step five: and (3) putting the pot mould liquid with the temperature of 90-100 DEG and the R & gt 4.0 into the pot mould liquid recovery tank, and enabling the pot mould liquid to sequentially pass through the pot mould liquid collection system, the pot mould liquid treatment system, the pot mould liquid separation system and the water re-reaction recovery system of the pot mould liquid, so as to dissolve aluminum scales in the systems and complete descaling of the system for recovering aluminum hydroxide from the pot mould liquid.
Further, in the second step, the aluminum hydroxide seed crystal is added, and when the concentration of aluminum ions in the reaction solution is reduced to 30g/L or less, the addition of the aluminum hydroxide seed crystal is stopped.
More specifically, the ratio of the concentration of the free alkali to the concentration of the aluminum ions in the die-stewing liquid recovered in the first step is 3.00-3.50.
Further, the ratio of the concentration of the free alkali to the concentration of the aluminum ions in the 90-100 DEG pot mold liquid added in the step five is more than 4.00.
Further, after stopping the addition of the seed crystal, the aluminum hydroxide is recovered after the crystallization is allowed to stand for not less than 2 hours.
Further, the first reaction tank, the second reaction tank, the recovery tank and the wastewater recovery tank are provided with stirrers, and the stirrers are stirred both when the alumina hydrate seed crystal is added and when the solid-liquid separation is performed.
More specifically, the stirring was continued for not less than 60 minutes after the addition of the alumina hydroxide seed crystal was stopped.
The invention has the beneficial effects that:
1. fully recovering aluminum ions in the die-cooking waste liquid, converting the aluminum ions into industrial aluminum hydroxide, changing waste into valuable, and realizing high-value resource utilization of the waste aluminum;
2. when the ratio of the concentration of free alkali to the concentration of aluminum ions in the die-cooking liquid is controlled to be 3.00-3.50 for the first time, the die-cooking liquid is partially decomposed to separate out aluminum hydroxide, and the wall of the die-cooking liquid is hardly scaled;
3. the invention utilizes the hot die-cooking liquid (the ratio of the concentration of the free alkali to the concentration of the aluminum ions of the die-cooking liquid is greater than 4.00 and 90-100 ℃) for the first time, completely dissolves the aluminum scale on the wall of the equipment, saves the trouble of manual cleaning, and recovers the production capacity of the equipment by a chemical method;
4. the aluminum hydroxide crystal seeds are sucked into the reaction tank by utilizing a negative pressure mode, the low-position addition of the aluminum hydroxide crystal seeds is realized, the high-position addition above the reaction tank is avoided, the risks of the aluminum hydroxide crystal seeds added from the upper surface of the mold boiling liquid and dangerous operation are avoided, and the labor intensity is reduced.
Drawings
The invention is further illustrated with reference to the following figures and examples.
FIG. 1 is a schematic overall structure of one embodiment of the present invention;
wherein: pot mould liquid recovery tank 1, retort 2, a first retort 21, a second retort 22, a hydrofluoric acid liquid storage tank 3, a recovery tank 4, a centrifuge 5, a wastewater recovery tank 6, a first pump 01, a second pump 02, a third pump 03, a stirrer 04, an overflow pipe 05, a first valve 0001, a second valve 0002, a third valve 0003, a fourth valve 0004, a fifth valve 0005, a sixth valve 0006, a seventh valve 0007, an eighth valve 0008, a ninth valve 0009, a tenth valve 0010, an eleventh valve 0011, a twelfth valve 0012, a thirteenth valve 0013, a fourteenth valve 0014, a sixteenth valve 0016, an eighteen valve 0018, a nineteen valve 0019, a twentieth valve 0020, a twenty-first valve 0021 and a twenty-second valve 0022.
Detailed Description
The technical scheme of the invention is further explained by the specific implementation mode in combination with the attached drawings.
The theoretical basis for producing the aluminum hydroxide by recovering aluminum ions from the mold-stewing waste liquid is as follows:
when the die is stewed, the aluminum stub bar in the grinding tool undergoes the following chemical reaction in the alkaline etching solution:
Al2O3+2NaOH＝2NaAlO2+H2o (removing natural oxide film) (1)
2Al+2NaOH+2H2O＝2NaAlO2+3H2↓ (dissolved aluminum) (2)
NaAlO2+2H2O＝Al(OH)3↓ + NaOH (groove liquid decomposition, regeneration lye) (3)
2Al(OH)3＝Al2O3.3H2O (pipe blockage and scale wall) (4)
According to the formulas (1) and (2), the higher the alkali concentration is, the higher the aluminum is dissolvedThe faster the speed; according to the two formulas (3) and (4), the mold boiling liquid is unstable, easy to decompose and form scales. According to the formula (3), in order to recover the aluminum hydroxide, the concentration of the sodium hydroxide can be properly reduced, the sodium metaaluminate is decomposed into the aluminum hydroxide and the sodium hydroxide, and the aluminum hydroxide can be separated by solid-liquid separation and the sodium hydroxide can be recycled. According to the formula (4), aluminum hydroxide is unstable and easily decomposed into Al2O3.3H2O, which forms aluminum scale and adheres to the tank wall, pipeline, valve, pump, stirrer, tank wall and other places where the tank liquid contacts, and the maintenance is very troublesome. In order to prevent the scale formation of the recovery equipment, it is necessary to increase the sodium hydroxide concentration appropriately so that the reaction formula (3) can be continued, and the reaction formula (4) is difficult to proceed.
The experimental result of the aluminum hydroxide production by recovering aluminum ions from the mold-stewing waste liquid is as follows:
grooving the mold-cooking liquid according to 100g/L of sodium hydroxide, starting mold cooking, rapidly heating the groove liquid to reach the boiling point, and increasing the concentrations of aluminum ions and free alkali. In the mould stewing process, every 20 minutes, one part of mould stewing liquid is respectively taken and stored for one week, and then indexes such as appearance, precipitation, scaling and the like of the bath solution are observed, and the results are as follows:
sample 1: taking 110g/L free alkali, Al3+20g/L of waste liquor, R ═ free base concentration/Al3+The concentration is 5.50, the bath solution is not decomposed, and no aluminum hydroxide is precipitated;
sample 2: taking 121g/L free alkali, Al3+34g/L of waste liquor, R ═ free base concentration/Al3+The concentration is 4.0, the bath solution is not decomposed, and no aluminum hydroxide is precipitated;
sample 3: taking 121g/L free alkali, Al3+34g/L of waste liquor, R ═ free base concentration/Al3+The concentration is 3.56, the bath solution is not decomposed, and no aluminum hydroxide is precipitated;
sample 4: taking 125g/L free alkali, Al3+38.5g/L of waste liquor, R ═ free base concentration/Al3+The concentration is 3.50, the bath solution is decomposed, a trace amount of aluminum hydroxide is separated out, and the wall of the container is free of scale;
sample 5: taking 125g/L free alkali, Al3+38.5g/L of waste liquor, R ═ free base concentration/Al3+The concentration is 3.25, the bath solution is decomposed, a small amount of aluminum hydroxide is separated out, and the wall of the container is free of scale; adding aluminum hydroxide seed crystal, stirringUniformly standing for 2 hours, and obviously increasing the aluminum hydroxide; and filtering and rinsing the crystal, drying for 2 hours at the temperature of 110 +/-5 ℃ to obtain an aluminum hydroxide sample, and then inspecting. Referring to the national standard of aluminum hydroxide (table 0), the sample is entrusted to the detection and test center of Guangzhou chemical institute of Chinese academy of sciences to test, and the result is shown in table 1, and the obtained aluminum hydroxide product completely meets the requirements of the national standard;
sample 6: taking free alkali of 128g/L, Al3+42.7g/L of waste liquor, R ═ free base concentration/Al3+The concentration is 3.00, the bath solution is decomposed, the precipitation of aluminum hydroxide is increased, and the wall of the container is free of scale;
sample 7: taking 131g/L free alkali, Al3+47.6g/L of waste liquor, R ═ free base concentration/Al3+The concentration is 2.95, the bath solution is decomposed, the precipitation of aluminum hydroxide is increased, and the wall of the container is slightly scaled; after recovering the aluminum hydroxide sample, adjusting the R ═ free alkali concentration/Al of the mold-stewing waste liquid3+Concentration of>4.00 at 90-100 deg.C, and after 30 min, the aluminum scale is completely dissolved and the wall is clean.
Sample 8: taking 134g/L free alkali, Al3+53.6g/L of waste liquor, R ═ free base concentration/Al3+The concentration is 2.50, the bath solution is decomposed, the precipitation of aluminum hydroxide is increased, and the scaling of the container wall is increased;
sample 9: 143g/L of free base, Al3+71.5g/L of waste liquor, R ═ free base concentration/Al3+When the concentration is 2.00, the bath solution is decomposed, the precipitation of aluminum hydroxide increases, and the fouling of the vessel wall increases.
TABLE 0 national standard for aluminum hydroxide
TABLE 1 test results for aluminum hydroxide samples of example 5
As shown in figure 1 of the drawings, in which,
a system for recovering aluminum hydroxide from a die-cooking liquid comprises a die-cooking liquid collecting system, a die-cooking liquid processing system, a die-cooking liquid separating system and a die-cooking liquid water re-reaction recovering system;
the die liquid collecting system comprises a die liquid recovery tank 1 and a first pump 01; the mould stewing liquid collecting system is used for collecting mould stewing liquid;
the mold boiling liquid treatment system comprises a reaction tank 2, a second pump 02 and an aluminum hydroxide crystal seed storage tank 3; the die-stewing liquid treatment system is used for carrying out chemical reaction on the die-stewing liquid and producing aluminum hydroxide;
the mold boiling liquid separation system comprises a recovery tank 4 and a centrifuge 5; the die-filling liquid separation system is used for carrying out solid-liquid separation on the produced aluminum hydroxide;
the mold boiling liquid water re-reaction recovery system comprises a wastewater recovery tank 6 and a third pump 03; the die-stewing liquid water re-reaction recovery system is used for recovering and treating the wastewater after solid-liquid separation;
the die-stewing liquid recovery tank 1, the first pump 01, the reaction tank 2, the second pump 02 and the recovery tank 3 are communicated in sequence through pipelines; the reaction tank 2 comprises a first reaction tank 21 and a second reaction tank 22; the first pump 01 is communicated with the first reaction tank 21 and the second reaction tank 22 through a pipeline provided with a first valve 0001 and a pipeline provided with a second valve 0002 respectively; the outlet of the second pump 02 is communicated with the tops of the first reaction tank 21 and the second reaction tank 22 through another pipeline; is communicated with the centrifuge 4 through the outlet of the recovery tank 3; a twenty-two valve 0022 is arranged between the die-stewing liquid recovery tank 1 and the first pump 01; a ninth valve 009 is arranged between the first reaction tank 21 and the second reaction tank 22 and the second pump 02; a sixteen-numbered valve 0016 is arranged at an inlet of the recovery tank 4; a seventeen valve is arranged between the recovery tank 4 and the centrifuge 5; and the aluminum hydroxide crystal seed storage tank 3 is communicated with the second pump 02 through a pipeline provided with a No. ten valve 0010.
The inlet of the waste water recovery tank 6 is communicated with the centrifuge 5 through a pipeline; the bottom of the wastewater recovery tank 6 is communicated with the third pump 03 through a pipeline provided with a nineteen-valve 0019; the middle part of the wastewater recovery tank 6 is communicated with the third pump 03 through a pipeline provided with an eighteen-position valve 0018; the third pump 03 is communicated with the first reaction tank 21 through a pipeline provided with a twenty-first valve 0021; the third pump 03 is communicated with the die cavity of the pot through another pipeline provided with a twenty-valve 0020; the bottoms of the first reaction tank 21 and the second reaction tank 22 are communicated with the second pump 02 through pipelines; a seventh valve 0007 is arranged at the bottom of the first reaction tank 21; an eighth valve 0008 is arranged at the bottom of the second reaction tank 22; the No. nine valve 0009 is arranged close to the No. two pump 02; the first reaction tank 21 is communicated with the second pump 02 through a pipeline provided with a third valve 0003 and a pipeline provided with a fifth valve 0005 respectively; the second reaction tank 22 is respectively communicated with the second pump 02 through a pipeline provided with a fourth valve 0004 and a pipeline provided with a sixth valve 0006; the second pump 02 is communicated with the wastewater recovery tank 6 through a pipeline, a twelve-gauge valve 0012 is arranged at a position close to the second pump 02, and a fifteen-gauge valve is arranged at a position close to the wastewater recovery tank 6; the second pump 02 is respectively communicated with the first reaction tank 21 and the second reaction tank 22 through another pipeline, an eleven-numbered valve 0011 is arranged at a position close to the second pump 02, a thirteen-numbered valve 0013 is arranged at a position close to the first reaction tank 21, and a fourteen-numbered valve 0014 is arranged at a position close to the second reaction tank 22.
The mould stewing liquid returns to the reaction tank 2 through the second pump 02 from the reaction tank 2 through a pipeline to form a major loop, the tenth valve 0010 is opened while the major loop is carried out, the aluminum hydroxide crystal seeds in the aluminum hydroxide crystal seed storage tank 3 are conveyed to the major loop of the mould stewing liquid by virtue of negative pressure to participate in the reaction with the mould stewing liquid, and under the continuous flow of the major loop liquid, the aluminum hydroxide crystal seeds can be more uniformly mixed with the mould stewing liquid, so that the reaction is quicker. The aluminum hydroxide seed crystal is fully mixed and reacted with the alkaline mold-boiling liquid at the second pump 02 without volatilization to generate aluminum hydroxide; the adding method realizes low-level adding of the aluminum hydroxide crystal seeds, avoids high-level adding above the reaction tank 2, avoids the risks of adding the aluminum hydroxide crystal seeds from the upper surface of the mold boiling liquid, seriously volatilizing at high temperature, harming the health of workers and polluting the environment, and reduces the labor intensity. After solid-liquid separation of aluminum hydroxide from the centrifuge 5, a large amount of free fluorine remains in the residual wastewater, fluorine in the wastewater recovery tank 6 is recovered by utilizing aluminum in the die-boiling liquid, and the reacted supernatant is sent back to the die-boiling tank to realize wastewater reuse; returning the residual solid-liquid mixture to the first reaction tank 21, and circularly recovering free fluorine; the wastewater is completely recycled, and the zero discharge of the wastewater and waste residues of the mold boiling liquid is realized.
Furthermore, overflow pipes 05 for preventing the mold boiling liquid from overflowing are arranged above the first reaction tank 21 and the second reaction tank 22; the overflow pipe 05 is communicated with the wastewater recovery tank 6.
The overflow pipe 05 is a safety safeguard to prevent excess liquid from overflowing the reaction tank 2. If the reaction solution exceeds the height of the overflow pipe 05, the reaction solution flows from the overflow pipe 05 to the waste water recovery tank 6, and the waste water recovery process is resumed.
In a further description, the first reaction tank 21, the second reaction tank 22, the recovery tank 4 and the wastewater recovery tank 6 are all provided with stirrers 04.
The chemical reaction of liquid exists in the first reaction tank 21, the second reaction tank 22 and the wastewater recovery tank 6, and the various reagents can be mixed more uniformly by fully stirring, so that the reaction speed is increased, and the reaction is more sufficient. In the recovery tank 4, sufficient stirring is performed to uniformly disperse the aluminum hydroxide in the reaction solution, and the effect is good when the centrifuge 5 performs solid-liquid separation.
The process for recovering aluminum hydroxide from mold stewing liquid comprises the following steps:
the method comprises the following steps: opening a twenty-two valve 0022, a first valve 0001 and a second valve 0002, closing a third valve 0003, a fourth valve 0004, a fifth valve 0005, a sixth valve 0006, a seventh valve 0007 and an eighth valve 0008, starting the first pump 01, pumping the die to be treated into the first reaction tank 21 and the second reaction tank 22, and finishing the operation of a die liquid collecting system;
step two: closing the third valve 0003, the fourth valve 0004, the fifth valve 0005, the sixth valve 0006, the eighth valve 0008, the tenth valve 0010, the twelfth valve 0012 and the fourteenth valve 0014; opening the seventh valve 0007, the ninth valve 0009, the eleventh valve 0011 and the thirteenth valve 0013, starting the second pump 02, and circulating the mold stewing liquid to be treated; opening a tenth valve 0010 under the condition that a second pump 2 keeps large circulation of the mold stewing liquid to be treated, and sucking aluminum hydroxide seed crystals into the first reaction tank 21 by utilizing negative pressure to react; adjusting a valve switch, and sucking aluminum hydroxide seed crystals into the second reaction tank 22 by using negative pressure in the same way to perform reaction;
step three: opening a valve No. three 0003 or a valve No. five 0005, opening a valve No. nine 0009, a valve No. twelve 0012 and a valve No. fifteen, and putting the supernatant in the reaction tank No. one 21 into the wastewater recovery tank 6; closing the No. eleven valve 0011, the No. fifteen valve and the No. seventeen valve; opening a seventh valve 0007 and a sixteenth valve 0016; starting a second pump 02, and pumping the solid-liquid mixture in the first reaction tank 21 into the recovery tank 4; turning on the electric centrifuge 5; opening a seventeen valve, performing solid-liquid separation on aluminum hydroxide, and conveying the recovered liquid to a wastewater recovery tank 6; adjusting a valve switch to separate the aluminum hydroxide and the liquid in the second reaction tank 22 in the same way;
step four: closing a valve No. fifteen, a valve No. eighteen 0018 and a valve No. nineteen 0019, and recycling the wastewater into the wastewater recycling tank 6; closing a fifteen-valve, a nineteen-valve 0019 and a twenty-first-valve 0021, opening an eighteen-valve 0018 and a twenty-valve 0020, starting a third pump 03, and sending the supernatant back to the die cavity; closing the eighteen valve 0018 and the twenty valve 0020; opening a nineteen valve 0019 and a twenty-first valve 0021; starting a third pump 03, and sending the solid-liquid mixture of the aluminum hydroxide back to the first reaction tank 21 for recycling;
step five: and (3) putting the 90-100-degree mould-stewing liquid into the mould-stewing liquid recovery tank 1, and enabling the mould-stewing liquid to sequentially pass through the mould-stewing liquid collection system, the mould-stewing liquid treatment system, the mould-stewing liquid separation system and the mould-stewing liquid water re-reaction recovery system to dissolve aluminum scales in the systems so as to complete descaling of the system for recovering aluminum hydroxide from the mould-stewing liquid.
Further, in the second step, the aluminum hydroxide seed crystal is added, and when the concentration of aluminum ions in the reaction solution is reduced to 30g/L or less, the addition of the aluminum hydroxide seed crystal is stopped.
The reaction rate is reduced by the decrease in the concentration of the reactants in the chemical reaction. When the concentration of aluminum ions in the reaction liquid is reduced to be below 30g/L, the concentration of the aluminum ions in the reaction liquid is already low, the reaction rate and the reaction efficiency can be continuously lowered by continuously adding the aluminum hydroxide seed crystals, and the aluminum hydroxide seed crystals are not added at this time for ensuring the production efficiency.
More specifically, the ratio of the concentration of the free alkali to the concentration of the aluminum ions in the die-stewing liquid recovered in the first step is 3.00-3.50.
A large number of accurate experiments prove that when the ratio of the concentration of free alkali in the die-stewing liquid to the concentration of aluminum ions is between 3.00 and 3.50, the die-stewing liquid is partially decomposed to separate out aluminum hydroxide, the wall of the die-stewing liquid is rarely scaled, aluminum hydroxide can be recycled after aluminum hydroxide crystal seeds are added, and an aluminum hydroxide product meeting the national standard requirement can be obtained after rinsing, filter pressing and drying.
Further, the ratio of the concentration of the free alkali to the concentration of the aluminum ions in the 90-100 DEG pot mold liquid added in the step five is more than 4.00.
The mold-stewing liquid under the condition can completely dissolve aluminum scale on the wall of the equipment, the trouble of manual cleaning is saved, the production capacity of the equipment is recovered by a chemical method, and the method is rapid and efficient.
Further, after stopping the addition of the seed crystal, the aluminum hydroxide is recovered after the crystallization is allowed to stand for not less than 2 hours.
The precipitation of aluminum hydroxide crystals is not a severe chemical reaction process, and it is necessary to stand still to sufficiently precipitate aluminum hydroxide.
Further, the first reaction tank 21, the second reaction tank 22, the recovery tank 4, and the wastewater recovery tank 6 are provided with stirrers 04, and stirring is performed both when alumina hydroxide seed crystals are added and when solid-liquid separation is performed.
More specifically, the stirring was continued for not less than 60 minutes after the addition of the alumina hydroxide seed crystal was stopped.
The above description is only a preferred embodiment of the present invention, and for those skilled in the art, the present invention should not be limited by the description of the present invention, which should be interpreted as a limitation.
Claims (7)
1. A process for recovering aluminum hydroxide from mold-stewing liquid is characterized by comprising the following steps: the system for recovering the aluminum hydroxide by using the die-cooking liquid comprises a die-cooking liquid collecting system, a die-cooking liquid processing system, a die-cooking liquid separating system and a die-cooking liquid water re-reaction recovering system;
the die cavity liquid collecting system comprises a die cavity liquid recovery tank and a first pump; the mould stewing liquid collecting system is used for collecting mould stewing liquid;
the mold boiling liquid treatment system comprises a reaction tank, a second pump and an aluminum hydroxide crystal seed storage tank; the die-stewing liquid treatment system is used for carrying out chemical reaction on the die-stewing liquid and producing aluminum hydroxide;
the mold boiling liquid separation system comprises a recovery tank and a centrifuge; the die-filling liquid separation system is used for carrying out solid-liquid separation on the produced aluminum hydroxide;
the mold boiling liquid water re-reaction recovery system comprises a wastewater recovery tank and a third pump; the die-stewing liquid water re-reaction recovery system is used for recovering and treating the wastewater after solid-liquid separation;
the die-stewing liquid recovery tank, the first pump, the second pump of the reaction tank and the recovery tank are communicated in sequence through pipelines; the reaction tank comprises a first reaction tank and a second reaction tank; the first pump is communicated with the first reaction tank and the second reaction tank through a pipeline with a first valve and a pipeline with a second valve respectively; the outlet of the second pump is communicated with the tops of the first reaction tank and the second reaction tank through another pipeline; communicating with the centrifuge through an outlet of the recovery tank; a twenty-two valve is arranged between the die-stewing liquid recovery tank and the first pump; a ninth valve is arranged between the first reaction tank and the second reaction tank and between the second pump; a sixteen-number valve is arranged at an inlet of the recovery tank; a seventeen valve is arranged between the recovery tank and the centrifuge; the aluminum hydroxide crystal seed storage tank is communicated with the second pump through a pipeline provided with a No. ten valve;
the inlet of the waste water recovery tank is communicated with the centrifuge through a pipeline; the bottom of the wastewater recovery tank is communicated with the third pump through a pipeline provided with a nineteen-valve; the middle part of the wastewater recovery tank is communicated with the third pump through a pipeline provided with an eighteen-type valve; the third pump is communicated with the first reaction tank through a pipeline provided with a twenty-first valve; the third pump is communicated with the die cavity of the pot through another pipeline provided with a twenty-valve; the bottoms of the first reaction tank and the second reaction tank are communicated with the second pump through pipelines; a seventh valve is arranged at the bottom of the first reaction tank; an eighth valve is arranged at the bottom of the second reaction tank; the ninth valve is arranged close to the second pump; the first reaction tank is communicated with the second pump through a pipeline provided with a third valve and a pipeline provided with a fifth valve respectively; the second reaction tank is communicated with the second pump through a pipeline provided with a fourth valve and a pipeline provided with a sixth valve respectively; the second pump is communicated with the wastewater recovery tank through a pipeline, a twelve-position valve is arranged at a position close to the second pump, and a fifteen-position valve is arranged at a position close to the wastewater recovery tank; the second pump is respectively communicated with the first reaction tank and the second reaction tank through another pipeline, an eleven-numbered valve is arranged at a position close to the second pump, a thirteen-numbered valve is arranged at a position close to the first reaction tank, and a fourteen-numbered valve is arranged at a position close to the second reaction tank;
the process for recovering the aluminum hydroxide by using the die-stewing liquid of the system for recovering the aluminum hydroxide by using the die-stewing liquid comprises the following steps of:
the method comprises the following steps: opening the twenty-two valve, the first valve and the second valve, closing the third valve, the fourth valve, the fifth valve, the sixth valve, the seventh valve and the eighth valve, starting the first pump, pumping the mold stewing liquid to be treated into the first reaction tank and the second reaction tank, and finishing the operation of a mold stewing liquid collecting system;
step two: closing the third valve, the fourth valve, the fifth valve, the sixth valve, the eighth valve, the tenth valve, the twelfth valve and the fourteenth valve; opening the seventh valve, the ninth valve, the eleventh valve and the thirteenth valve, starting the second pump, and circulating the mold stewing liquid to be treated; opening a No. ten valve under the condition that a second pump keeps large circulation of the mold stewing liquid to be treated, and sucking the aluminum hydroxide seed crystal into the first reaction tank by utilizing negative pressure for reaction; adjusting a valve switch, and sucking aluminum hydroxide seed crystals into the second reaction tank by using negative pressure in the same way to perform reaction;
step three: opening a third valve or a fifth valve, opening a ninth valve, a twelfth valve and a fifteenth valve, and putting the supernatant in the first reaction tank into the wastewater recovery tank; closing the No. eleven valve, the No. fifteen valve and the No. seventeen valve; opening the No. seven valve and the No. sixteen valve; starting a second pump, and pumping the solid-liquid mixture in the first reaction tank into the recovery tank; starting the electric centrifugal machine; opening a seventeen valve, performing solid-liquid separation on aluminum hydroxide, and conveying the recovered liquid to a wastewater recovery tank; adjusting a valve switch, and separating the aluminum hydroxide and the liquid in the second reaction tank in the same way;
step four: closing a No. fifteen valve, a No. eighteen valve and a No. nineteen valve, and recycling the wastewater into the wastewater recycling tank; closing the valve No. fifteen, the valve No. nineteen and the valve No. twenty-one, opening the valve No. eighteen and the valve No. twenty, starting the pump No. three, and sending the supernatant back to the die cavity; closing the eighteen valve and the twenty valve; opening a nineteen valve and a twenty-first valve; starting a third pump, and sending the solid-liquid mixture of the aluminum hydroxide back to the first reaction tank for recycling;
step five: placing the mold-stewing liquid at 90-100 ℃ into the mold-stewing liquid recovery tank, and enabling the mold-stewing liquid to sequentially pass through the mold-stewing liquid collection system, the mold-stewing liquid treatment system, the mold-stewing liquid separation system and the mold-stewing liquid water re-reaction recovery system to dissolve aluminum scales in the systems, so as to complete descaling of the system for recovering aluminum hydroxide from the mold-stewing liquid;
the ratio of the concentration of the free alkali to the concentration of the aluminum ions of the die-stewing liquid recovered in the step one is 3.00-3.50;
the ratio of the concentration of the free alkali to the concentration of the aluminum ions in the mold-cooking liquid at 90-100 ℃ added in the step five is more than 4.00.
2. The process for recovering aluminum hydroxide from the mold-stewing liquid as claimed in claim 1, wherein: overflow pipes for preventing the mold boiling liquid from overflowing are arranged above the first reaction tank and the second reaction tank; the overflow pipe is communicated with the wastewater recovery tank.
3. The process for recovering aluminum hydroxide from the mold-stewing liquid as claimed in claim 1, wherein: stirrers are arranged in the first reaction tank, the second reaction tank, the recovery tank and the wastewater recovery tank.
4. The process for recovering aluminum hydroxide from the mold-stewing liquid as claimed in claim 1, wherein: and adding aluminum hydroxide seed crystals in the second step, and stopping adding the aluminum hydroxide seed crystals when the concentration of aluminum ions in the reaction liquid is reduced to be below 30 g/L.
5. The process for recovering aluminum hydroxide from the mold-stewing liquid as claimed in claim 1, wherein: after stopping adding the seed crystal, standing for crystallization for not less than 2 hours, and recovering the aluminum hydroxide.
6. The process for recovering aluminum hydroxide from the mold-stewing liquid as claimed in claim 1, wherein: all be equipped with the agitator in a retort, No. two retort, recovery tank and the waste water recovery jar, all stir when adding aluminium hydroxide seed crystal and when carrying out solid-liquid separation.
7. The process for recovering aluminum hydroxide from the mold-stewing liquid as claimed in claim 6, wherein: the addition of the aluminum hydroxide seed crystal is stopped, and then the stirring is continued for not less than 60 minutes.
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| CN109112537B (en) * | 2018-07-27 | 2021-08-03 | 佛山市三水雄鹰铝表面技术创新中心有限公司 | Device and process for recovering aluminum hydroxide and sodium sulfate from oxidation liquid and deoiling neutralization liquid |
| CN108975295B (en) * | 2018-07-27 | 2020-06-23 | 佛山市三水雄鹰铝表面技术创新中心有限公司 | Method for recovering aluminum and sodium-containing byproducts from mold-cooking liquid in aluminum processing |
| CN109133131B (en) * | 2018-07-27 | 2021-01-12 | 佛山市三水雄鹰铝表面技术创新中心有限公司 | System and method for neutralizing and recovering aluminum hydroxide and sodium sulfate from oxidation liquid and mold-cooking liquid |
| CN109112546B (en) * | 2018-07-27 | 2021-04-20 | 佛山市三水雄鹰铝表面技术创新中心有限公司 | Oxidation line system and process for recovering aluminum hydroxide and sodium sulfate from mold-stewing liquid |
| CN113025415A (en) * | 2021-03-10 | 2021-06-25 | 德清骄阳建材贸易有限公司 | A environmental protection processing system for aluminium alloy drawing of patterns waste liquid |
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| CN103451436A (en) * | 2013-09-02 | 2013-12-18 | 佛山市三水雄鹰铝表面技术创新中心有限公司 | System for neutralizing treatment of demoulding waste liquor and anodic oxidation waste liquor and recovery of aluminum ions of aluminum processing plant |
| CN106367792A (en) * | 2016-11-11 | 2017-02-01 | 佛山市三水雄鹰铝表面技术创新中心有限公司 | Aluminum pretreatment alkaline three-in-one online recycling system for demolding alkaline liquor for extruding mold aluminum material heads and aluminum hydroxide |
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| CN103451436A (en) * | 2013-09-02 | 2013-12-18 | 佛山市三水雄鹰铝表面技术创新中心有限公司 | System for neutralizing treatment of demoulding waste liquor and anodic oxidation waste liquor and recovery of aluminum ions of aluminum processing plant |
| CN106367792A (en) * | 2016-11-11 | 2017-02-01 | 佛山市三水雄鹰铝表面技术创新中心有限公司 | Aluminum pretreatment alkaline three-in-one online recycling system for demolding alkaline liquor for extruding mold aluminum material heads and aluminum hydroxide |
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