Method for recovering aluminum hydroxide and sodium hydroxide from liquid waste of aluminum industry alkali waste

Abstract

Disclosed is a method for recovering aluminum hydroxide and sodium hydroxide from liquid waste of aluminum industry alkali waste. The method comprises the following steps of (1) obtaining liquid wastecontaining free alkali and aluminum ions at a ratio of 3.0-3.5; (2) adding seed crystal inside the liquid waste; (3) precipitating aluminum hydroxide; (4) performing solid-liquid separation on the liquid waste to recovering the aluminum hydroxide as well as alkali liquor containing sodium hydroxide. The method for recovering the aluminum hydroxide and the sodium hydroxide from the liquid waste ofthe aluminum industry alkali waste can effectively recover the aluminum hydroxide meeting national standard to achieve high-value resource reutilization of waste aluminum, to reduce the scaling riskof recovery equipment and to greatly prolong the maintenance period, and meanwhile, can on line recycle the alkali liquor containing the sodium hydroxide to reduce the production cost of mold boilingand further to achieve zero emission of liquid waste and waste residue of a mold boiling workshop.

Description

technical field [0001] The invention relates to the technical field of aluminum processing, in particular to a method for recovering aluminum hydroxide and sodium hydroxide from waste liquid of slag reduction in the aluminum industry. Background technique [0002] Aluminum and aluminum alloys have the advantages of excellent processing performance, good corrosion resistance, beautiful surface, high recovery rate, etc., and have been widely used in construction, transportation, machinery, electric power and other industries. In recent years, the trend of expanding the application of aluminum by replacing steel with aluminum has become more obvious . The aluminum processing industry is a traditional industry, and it is a sunrise industry full of vitality. According to statistics, the per capita annual consumption of aluminum in developed countries in Europe and the United States is more than 32kg, while the per capita consumption in my country is only about 13kg, which is onl...

AI Technical Summary

Problems solved by technology

[0010] 2.1. Extrusion mold waste liquid waste water waste residue

[0018] (2) Current status of treatment and utilization of waste slag in the aluminum industry

At present, there are three main routes for resource utilization of aluminum ash: (1) Recycling alumina and returning it to electrolysis, and recycling chloride salt as a melting and casting refining agent, but the main component of aluminum ash is α-Al 2 o 3 , the activity is poor, and it takes more energy to ionize it, resulting in an increase in the cell voltage

(2) Acid or alkali treatment to remove impurities, production of inorganic materials such as synthetic brown corundum, Sialon ceramics and refractory materials, production of water purification materials such as polyaluminum chloride and aluminum sulfate, and production of slagging desulfurizers for steelmaking, but due to The cost is higher than the existing ones, and industrial production cannot be realized

(3) Production of building materials or road construction materials, such as aluminate cement, calcium aluminate powder, clear water bricks, and road construction materials, etc., but the fluoride and chloride salts contained in them have an impact on performance, and the added value of the product is low, limiting practical application

This method is simple, but has the following disadvantages: first, it loses sulfuric acid, wastes aluminum ions, and the consumption of sulfuric acid reaches more than 60kg / t;

[0039] The recovery of hexavalent chromium ions is still a difficult problem, and it is impossible to realize online recovery of chromium-containing agents

[0043] To sum up, the traditional waste water and residue treatment methods have the following deficiencies: first, the waste water can reach the discharge standard after treatment, but the reuse rate of reclaimed water is low; Useful resources such as acid and alkali, metal aluminum, and chemicals are wasted; fourth, the waste residue is hazardous waste, and the disposal cost is high, and environmental protection tax must be paid

[0051] 3. There are problems in the treatment of waste water and residue in extrusion surface treatment

[0052] First, high water consumption, lack of mature water-saving technology, and low water reuse rate; second, online classification of wastewater has not become a pre-procedure, resulting in a large amount of waste residue; third, the comprehensive utilization of waste residue has little effect, and waste residue treatment Become a corporate burden and environmental risk

[0053] At present, there are three prominent contradictions and problems in the treatment of waste residues: First, the state implements the management of enterprise pollutant discharge permits to control the total amount of pollutants discharged by enterprises, but the actual amount of waste water and residues of enterprises is far greater than the allowable discharge amount; second, waste residues must be It is legally transferred to a qualified third party for disposal, but the disposal capacity is obviously insufficient to legally dispose of such a huge amount of waste residue; the third is to dispose of waste residue according to hazardous waste regulations, which has complicated procedures, low efficiency and high cost

However, this method sacrifices the alkali in the potting waste liquid and the sulfuric acid in the oxidizing liquid that can be recycled, which is a pity; Chinese patents CN201710461889.7 and CN201010273267. Aluminum hydroxide and sodium hydroxide can be recovered by analytical method. This method is feasible, but after partial aluminum hydroxide is decomposed, it is easy to scale, block pipes, valves, and pumps, and equipment maintenance is very troublesome. These problems are not solved in this patent, and the equipment cannot operate normally. The waste pot liquid will not be recyclable; Chinese patent CN201610128702.7 proposes to treat the pot liquid with lime to generate calcium aluminate and recover sodium hydroxide; this invention can completely recycle the pot liquid, but the recovered calcium aluminate is too valuable Low, it's a shame to waste a lot of aluminum

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