DE2343341C3 - Process for the production of alumina with processing of the by-products - Google Patents

Description

The invention relates to a process for the production of alumina with processing of the accruing by-products, e.g. B. amorphous silicon dioxide, sodium and ammonium sulfates, which when Melting aluminum, widely used in the manufacture of zeolites and glass.

It is a method of producing alumina and by-products by processing aluminosilicate raw material known, in which natural minerals such as bauxite, kaolins, clays,

R ₂ O • Al ₂ O., • / 1 SiO ₂ -I- (ti - 2) • Na ₂ O + »1 H ₂ O
Perlite

Alum stones used (M a s e 1, W. A .: Proiswodstwo günosjoma, Moscow 1955 - Gosudarstvennoje Nautschno-Technicheskoje Isdatelstwo Literatury po chernoj i zwetnoj Metallurgii).

To achieve an amorphous structure, the natural raw material is ^{roasted and cooled at a temperature of 700 to 900 °} C. The material is then treated with sulfuric acid with a concentration of not more than 40%.

The sludge obtained is filtered off. Silicon oxide (silica) remains in the precipitate, while the Filtrate containing aluminum sulphates, alkalis and iron by the action of an ammonia solution Separation of aluminum and iron in the form of hydroxides R (OH) 3 is precipitated.

The aluminum hydroxide is purified from the iron (III) hydroxide by passing gaseous through it Hydrogen chloride, or by adding manganese oxide. This gives you clay as well as sodium and Ammonium sulfates.

The use of natural raw materials for the production of clay requires the preceding Roasting and subsequent cooling, which complicates the technological process and the product becomes more expensive. The use of dilute sulfuric acid makes filtering and washing the more difficult Silica because the process of degradation of the alkaline aluminosilicates forms silica gel.

The percentage yield of clay from the natural alkaline aluminosilicates is not high and is in a range from 80 to 85%. Therefore, the alumina and silica get contaminated due to particles of the parent rock that reduce the quality of the product.

In DT-PS 7 53 121 and 2 99 121, a mixture with sulfuric acid at 450 to 750 ^° C. is roasted beforehand to increase the reactivity of rocks containing aluminum, primarily clay, and the sintered product is then cooled and

4u marry.

Thereafter, ^{H2SO4, heated to 100 °} C., and H ₂ O are added. When the reaction is complete, the mixture is filtered and washed to remove sulfates from the precipitate.

According to the invention, the aluminosilicate material produced by leaching perlite is used as the aluminosilicate used:

= R ₂ O · Al ₂ O, · 2SiO ₂ · 2H ₂ O + (11-2) Na ₂ O · SiO ₂ + (m-2) H ₂ O

Precipitate solution

In contrast to the known methods, according to the invention, it is not the original rock, such as clay, nepheline, etc., that is subjected to the acid treatment, but an artificially produced substance that is highly reactive, which in turn enables acid treatment without prior roasting, even without prior heating. The special properties of the precipitate, such as amorphism, high alkalinity and hydration, allow the use of highly concentrated H ₂ SO4, with high filtration efficiency being ensured, since the reaction is exothermic.

In the process according to the invention, the yield of main component (AI ₂ Oj) is 98 to 99%, which is related to the high reactivity of the alkaline aluminosilicates produced from perlite.

The purpose of the present invention is to avoid the disadvantages mentioned.

The invention is based on the object of using a method for producing alumina of the by-products produced using such a raw material and application of such to develop technological process steps that make it possible to increase the technological process (\ s simplify as well as alumina and by-products higher Maintain quality.

The invention therefore relates to a process for the production of alumina using the

Accruing by-products, in which an aluminosilicate raw material with concentrated sulfuric acid unlocks, the remaining silica is filtered off, then aluminum and iron hydroxides with ammonia solution precipitate from this precipitate (R2O3) dissolves the aluminum hydroxide with an aqueous sodium hydroxide solution, the sodium aluminate is filtered off from the iron hydroxide, from which aluminum hydroxide is precipitated, which is then dried and calcined, which is characterized in that one

a) Alumocilicate remaining as aluminosilicate raw material through alkaline leaching of perlite used,

b) digesting this raw material with sulfuric acid at a concentration of 80 to 90%,

c) from the aluminate liquor with the aluminum hydroxide Carbon dioxide precipitates,

d) the Na ^ Ch solution obtained according to c) _{causticized with Ca (OH) 2} and the sodium hydroxide solution returned,

e) washes the silica with a hydrochloric acid solution and dries it,

f) the filtrate from the R2O3 precipitation with ground perlite and limestone mixed, the mixture dried and granulated.

The process steps c) and d) are per se in the Technology of aluminum or alumina known.

The production of aluminosilicates in the alkaline processing of perlite is from the SU-PS 164 584 known

In the course of the exothermic reaction the temperature of the mixture rises abruptly to 160 to 17O ⁰ C This leads to dehydration of the Silica gels, which aggregates the silica, the is the cause of good sludge filtration. The high percentage recovery of clay from the Starting raw material and the high quality of the products obtained have a positive effect on the cost of the Product. The use of caustic soda solution for cleaning the alumina from ferric hydroxide is more advanced because it achieves a high degree of purification of the end product.

For a better understanding of the invention, a specific example is given for carrying out the method according to the invention.

example

5 Alkaline aluminosilicates R ₂ O · Al ₂ O ₃ η SiO ₂ m H ₂ O with a small amount of admixtures such as Fe ₂ O3; CaO; MgO (the total amount of which in the alkaline aluminosilicates can vary in a range from 3 to 6% by weight) of the general chemical composition:

SiO ₂ 38 wt. O / o; Al ₂ O ₃ 29 wt%; R ₂ O 19 wt%; Fe ₂ O ₃ 1.68 wt%; CaO 1.62 wt%; MgO 0.7 wt%; Losses during annealing + moisture 10% by weight are treated with 80 to 90% sulfuric acid solution. By treatment with acid, the alkaline perlitalum silicates are converted into silicon dioxide (SiO ₂ ) and sulfates of the same cations that are contained in the starting _{raw material (K 2} SO ₄ ; Na ₂ SO ₄ ; CaSO ₄ ;

MgSO ₄ ; Al ₂ (SO ₄ J ₃ ; Fe ₂ (SO ₄ ) ,, according to the following reaction

(Na, K) ₂ O AI ₂ O, 2SiO ₂ DiH ₁ O + 4H ₂ SO ₄ = (Na ₅ K) ₂ SO ₄ + Al ₂ (SO ₄ J ₃ + 2SiO ₂ + (m + 4) H ₂ O

disassembled.

The obtained sludge is subjected to filtration. The soluble sulfates (K ₂ SO ₄ ; Na ₂ SO ₄ ; Al ₂ (SOO ₃ ; ""<· Fe ₂ (SO ₄ ) S) pass into the filtrate, while in the precipitate SiO ₂ essentially poorly soluble calcium sulfates and admixtures of the The chemical composition of the precipitate (SiO ₂ ) is as follows: SiO ₂ 81.40% by weight; MgO 0.4% by weight; Al ₂ O ₃ 1.2% by weight; Na ₂ O 0.2 wt%;

K ₂ O 0.2 wt%; Fe ₂ O ₃ traces; CaO 0.6 wt%; Annealing + moisture losses 16.00 wt%.

To produce pure silicon dioxide, the precipitate is treated with a hydrochloric acid solution, dried after washing and packaged as a commercial product with the chemical composition: SiO ₂ 89.84% by weight; Annealing losses + moisture 938 wt%; all remaining 0.78% by weight.

The sulfate solution (filtrate) is treated with aqueous ammonia solution (25%) to precipitate aluminum and iron in the form of hydroxides according to the following reaction:

following reaction:

Al (OH) ₃ + NaOH = NaAlO ₂ + 2H ₂ O,

while Fe (OH) _{3 forms} unchanged in the form of a precipitate, which is separated off by filtration.

The filtrate (sodium aluminate) is subjected to carbonization according to the known method

2NaAIO ₂ + 4H ₂ O + CO ₂

► 2Al (OH) ₃ + Na ₂ CO ₃ + H ₂ O,

+ 6NH ₄ OH = 2RiOH)., + 3 (NH ₄ I ₂ SO ₄ ,

where R stands for Al and Fe.

The suspension is subjected to filtration to separate R (OH) ₃ from the sodium, potassium and ammonium sulfate. The precipitate R (OH) _{3 is} treated with a solution of caustic soda with an Na ₂ O concentration of about 400 to 450 g / l. Then Al (OH) ₃ reacts with NaOH, and sodium aluminate (NaAIO ₂ ) is formed after the where AI (OHJj is deposited, which after separation by filtration from sodium and potassium carbonate is subjected to calcination (at 1000 to 110O ⁰ C) and as commercial alumina with the chemical composition:

Al ₂ O ₃ 99.6 wt%; SiO ₂ 0.25 wt%; Na ₂ O 0.14 wt%; Fe ₂ O ₃ 0.01 wt .-% is packed.

During the treatment of the alkaline aluminosilicates (as can be seen from the above) by-products such as the solution of sodium, potassium and ammonium sulfate and the solution of sodium carbonate Na ₂ CO ₃ (obtained during the carbonation of the sodium aluminate) arise.

The sodium carbonate solution is subjected to causticizing with lime

Na ₂ CO, + Ca (OH) ₂ = 2HaOH + CaCO,

CaCOi is separated off by filtration, and the filtrate is passed through (NaOH) in the process of dissolving AI (OHj)

back, while the calcium carbonate and the sodium, potassium and ammonium sulfates for the preparation of Glass sets can be used.

To make glassware, the solution of sodium, potassium and ammonium sulfate is mixed with ground perlite and limestone.

It was found that in the processing, 1 t alkaline aluminosilicates 1.61 sodium sulphate and when adding 63 t of perlite (with the chemical Composition:

SiO; 7337 wt% IAl ₂ O ₃ Ϊ3.41 wt%; R ₂ O 73 wt%; Fe ₂ O ₃ 0.76 wt%;

CaO 1.17 wt%; MgO 0.44 wt%; Loss on annealing + moisture 3.94 % By weight) and 1.1 t calcium carbonate (CaCO ₃ ) 9 t

Glassware of the following chemical composition can be obtained:

SiO ₂ 62.2 wt%; Al ₂ O ₃ 11 M wt%; Na ₂ O 15.1 wt% JFe ₂ O ₃ O 4 wt% _; CaO 10.44 wt%; MgO 034 wt%; TiO ₂ 0.08

Wt%.

■ ο The glass set produced in this way is according to his Properties better because it is more homogeneous, does not separate and is cheap.

Claims (1)

Claim: Process for the production of alumina with processing of the by-products which you can use an aluminosilicate raw material with concentrated Dissolves sulfuric acid, the remaining silica is filtered off, then aluminum and iron hydroxide precipitates with ammonia solution, from this precipitate (R2O3) with a aqueous sodium hydroxide solution dissolves the aluminum hydroxide, the sodium aluminate from the iron hydroxide filtered off, from which aluminum hydroxide precipitates, which is then dried and calcined, characterized in that one a) aluminosilicate remaining as aluminosilicate raw material through alkaline leaching of perlite used, b) the digestion of this raw material with sulfuric acid with a concentration of 80 to 90% performs, c) the aluminum hydroxide from the aluminate liquor precipitates with carbon dioxide, _{d) the Na 2} CO3 solution obtained according to c) is causticized with Ca (OH) ₂ and the sodium hydroxide solution is recycled, e) washes the silica with a hydrochloric acid solution and dries it, f) the filtrate of the R2O3 precipitation mixed with ground perlite and limestone, the mixture dries and granulates.