DD208338A1 - PROCESS FOR THE PRODUCTION OF SODIUM ALUMINATE LIQUID - Google Patents

Abstract

The invention relates to a process for Natriumaluminatlauge from the products salt slag of the aluminum scrap processing and mother liquor of the molecular sieve synthesis. The salty aluminum rotary kiln slag is subjected to a crushing of an intensive treatment with water to herausloesen the salt content. The resulting aluminum-containing sludge is digested with a natronlaugehaltigen mother liquor from the molecular sieve synthesis. The finely divided elemental aluminum is dissolved with hydrogen evolution to sodium aluminate. The insoluble constituents and the resulting precipitates are separated by filtration. After concentration by heat treatment, a pure sodium aluminate liquor with at least 8% by weight Na 2 O deep and 8% by weight Al deep 2 O deep 3 is formed.

Description

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Title of the invention:

Process for the preparation of sodium aluminate lye

Field of application of the invention:

The invention relates to a process for the preparation of Hatriumaluminatlauge from the products salt slag of aluminum scrap processing and mother liquor of Moiekularsiebsynthese.

Characteristic of the known technical solutions: It is known that 3-sodium aluminate liquor is formed during the alkaline decomposition of Bauzit. The finely ground 3auxite is pressurized with caustic soda in an autoclave at 4 to 6 atm. open minded. The lye concentration must weight above 35 -.% 5aOH are "However, the filtration of the previously diluted Alumlnatlauge makes great difficulties because of Eisenhydroxidniederschlag of slimy texture is t.

To prepare molecular sieves, a dilute silicate solution is initially charged at room temperature and a dilute aluminate solution containing the required amount of ITaOH is added with vigorous stirring. The mixture is homogenized and heated to 50 to 10O ⁰ C. During the crystallization time, the mixture is not stirred. After crystallization, the hot reaction mixture is filtered and washed. The molecular sieve is then dried. The mother liquor is fed as waste product to the wastewater treatment plant.

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When melting aluminum and its alloys, the use of flux is recommended. Especially when melting aluminum wastes, the use of suitable fluxing agents is required to protect the metal through the riverbed against the action of the puffing gases. The flux consists of salt mixtures such as potassium chloride, sodium chloride or Abraumsalzen such as carnallite. The resulting melt residues (dross, molten salts, salt slags, foams) are removed from the melt. This metal particles are entrained in more or less large amount · For the recovery of some methods are known, however, which are associated with additional process steps with high energy inputs. It is known to remelt the dross or crush it and treat it in a chlorine-inert gas atmosphere. For the most part, however, the scrapes are not worked up and fed to the waste product landfill.

Object of the invention

The aim of the invention is to supply the salt-containing aluminum rotary kiln slag and the mother liquor of the molecular sieve synthesis for use as a secondary raw material.

Explanation of the essence of the invention

The invention is based on the object enschlacke produce pure sodium aluminate from the salt-containing Aluminiumdrehrohrof the task.

It has now been found that pure sodium aluminate can be prepared by crushing the salt-containing aluminum rotary kiln slag, dissolving the salt with water and, after filtration, digesting the molecular sieve-containing sludge containing up to 25% by weight of aluminum. The silicate contained in the mother liquor used precipitates as insoluble aluminosilicate and is separated by filtration. This gives a pure silicate-free Sodium Aluminate Lye ♦

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To dissolve the salt components in the slag, the TVasser is recirculated until it reaches the saturation concentration. In order to completely remove the soluble salt content and thus to guarantee the purity of the sodium aluminate to be produced, washing out with water or with the circulated salt solution at a higher temperature is advantageous. Optimum dissolution rates were found at 9O ⁰ C. The remaining sludge contains in addition to the finely divided pure aluminum impurities such as aluminum and magnesium oxide, water-insoluble compounds of copper, manganese, silicon, iron and zinc.

The synthesis of molecular sieves produces a sodium-containing mother liquor which contains 5 to 12% strength sodium hydroxide solution, depending on the type of molecular sieve produced. In addition, it is contaminated with aluminate and Silikatrestmengen concentrations below 2 wt - . % . With such mother liquors can be digested with water pretreated aluminum-containing slags. The process is already possible at room temperature, but advantageous for accelerating the dissolution cie application of temperatures from 30 to 10O ⁰ C. The aluminum is dissolved under 7 / as se rs tcff development of the sodium hydroxide to sodium aluminate. It is best to use the about 10% mother liquor of the molecular sieve 4A preparation, which already contains about O, β wt .-% aluminate, since this Älumπniumanteil can be recycled in this way again in the Molekularsisbsjntheseprozeß. When using a silicate-containing mother liquor this is as a sodium aluminosilicate gel the composition 2Na ₂ O composition. Al ₂ Oo. 7SiO ₂ . zH ₂ 0 precipitated during digestion. After possible constriction of the liquid and subsequent filtration, a pure ETatriumaluminatlauga, the at least 3 wt .-% ITa ₃ O and 8 wt .-% ^

₂ ⁰ 3

The aluminate prepared according to the invention has the advantage that it can be used without further treatment in the preparation

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can be used by molecular sieves. "Substantial costs for the import of bauxite and for the sodium hydroxide, which are so far required for the production of Natriumaluminatlauge, can be avoided" Sin another advantage of the method is that the mother liquor of the molecular sieve synthesis almost quantitatively in the Synthesis process can be recycled and no longer pollutes the environment as wastewater · In addition, the large amounts of aluminum varnishes are worked up.

embodiment

The invention will be explained below by way of example:

example

17.5 kg lumpy rotary kiln slag containing aluminum, alumina and inorganic salts is treated with 120 1 of water at 90 ⁰ C. Each about 10 hours, the pesticide is separated by filtration and washed. The residual, containing alumina slurry (7.5 kg) is a weight 50 1 8 -.% ITa ₂ O and 0.9 wt .- # Al ₂ O containing aqueous 2eolith 4A mother liquor cooked, concentrated to 40 1 , filtered off and the filter cake washed with 5 1 10 & Lger HaOH. This gives 4-3.5 l of sodium aluminate solution containing 9.19% by weight of Al ₂ O and 10.2% by weight of Ea ₂ O and 4.6 kg of insoluble residue.

Claims (3)

- 241398 7 Br ϊ ind ungs ana χ> ru ch: 1. A process for the preparation of pure Hatriumaluminatlauge from aluminum-containing slags, characterized in that the slags are freed by treatment with water from the soluble salts and after filtration of the aluminum-containing sludge with an aluminate and / or silicate-containing mother liquor, for example from the molecular sieve at Temperatures of 30 to 100 ⁰ C digested and dia resulting ilatriuaaluminatlauge is separated by filtration of the insoluble constituents and resulting precipitates. 2. The method according to item 1, characterized in that dia treatment of the slag with water at a higher temperature, in particular at 90 ⁰ C, takes place and / or the water is circulated. 3. The method according to points 1 and 2, characterized in that the molecular sieve mother liquors 4 to 12 wt -% 0 contain.