HU198426B - Process for producing alkali-hydroaluminate - Google Patents

Abstract

The method comprises leaching a raw material containing aluminium oxides and an alkaline metal while obtaining the alkaline solution which is then desiliconized and concentrated by evaporation, the alkaline solution with a molar ratio of the alkaline metal oxide and aluminium oxide Me2O:Al2O3 of 1.1-1.7 being the subject of that concentration by evaporation. The concentration by evaporation is effected at a temperature of 120-150<o>C up to a concentration of the alkaline metal oxide of 350-400 g/l. After concentration by evaporation the solution at a temperature of 95-150<o>C is subjected to crystallization on a moving filtration surface having a temperature of 10-95<o>C so that a rapid crystallization of the product and its separation from the mother liquor takes place on the filtration surface. The resulting mother liquor is returned for the leaching of the raw material.

Description

The present invention relates to a process for the production of an alkali metal hydroaluminate by digesting a crude material containing aluminum and an alkali metal oxide, deacidifying and evaporating the resulting alumina base and crystallizing the alkali metal hydroaluminate.

Alkali metal bridge aluminate is essential for many industries, replaces resin glues in the pulp and paper industry, serves as a flocculating agent in wastewater and drinking water treatment, strengthens the soil when constructing underwater facilities, is used as a binder in molten oil, and as a binder in molding.

A process for the preparation of sodium hydroaluminate is known, whereby the raw material containing aluminosilicate is extracted with alkali hydroxide and lime, the resulting aluminate solution having a caustic molar ratio of Na ₂ O: Al ₂ O ₃ = 7 is de-silica, 20-40% (350-575 g / l) Na are evaporated until ₂ O content, and sodium hidroaluminát (Na ₂ 0 ₂ · Α1 Ο ₃ · 2.5 H ₂ O) are seeded with seed crystals, the product is crystallized and separated from the mother liquor of 20-60 ° C (3998927 U.S. Pat. The yield of the process is high (80%), but the equipment required for evaporation is expensive because it must be made of corrosion-resistant material and the energy required to evaporate the solution.

Sodium hydroaluminate is also obtained from a solution of silicon-free aluminum in the alumina production by evaporating the caustic molar ratio of 2.3 to 3.6 to 400-550 g / l Me ₂ O at 116-140 ° C. The alkali concentration of corroded steel appliances, and according to some authors (AJ Lainer, "Alumina" Proizvodsztvo glinozema, 1961, _{Moscow) r} MetaIlurgija 'rent) the rate of corrosion can reach a value of 8.5 to 34 mm / year.

Several attempts have been made to improve the process based on the evaporation of the alumina (Trudy Vzyeszoyznovo aluminievo-magnievovo institute, No. 70, GA Panasko and MJ Smirnova: "Poluchenie natrievoi kausticheskoi schelochi iz smeshannyh aluminatnykh", 1970, " p., VS Szazsin, Novye gidrokhimicheskie sposoby polucheniya glinozema, 1979, Kyiv, Naukova Dumka Publisher, 125-126, 130, 208).

In one experiment, a silica-free alumina solution having a molar ratio above 3.4 (the molar ratio Me ₂ O: Al ₂ O ₃ is hereinafter referred to as caustic molar) is evaporated to 500-510 g / l Me ₂ O and the product is concentrated to 30-90 g / l. It is crystallized at 0 ° C. The experiment was unsuccessful because crystallization at 30 ° C resulted in a thick paste which could not be separated into a precipitate and a mother liquor. The alumina residue remaining in the precipitate is not recycled, so the alkaline content of the digestion liquor must be replaced. The yield of the process is good (about 80%) but the product has a high water content and requires additional energy to be dried. Crystallization at about 90 ° C yields only a low yield (about 60%).

An attempt was made to obtain a better yield and recover more mother liquors by evaporating the be2-deactivated 2.3 caustic molar aluminate solution to 400-450 g / l Me ₂ O and then crystallizing it at 50-70 ° C. The crystallized solution is allowed to stand for another 1-2 hours and then the product is isolated by filtration. The process allows the mother liquor to be recovered, but the yield of alkali metal hydroaluminate is low (60%). To increase the yield, the mother liquor was more concentrated (450-510 g / l Me ₂ O), then crystallized at 30 ° C and the crystalline pulp filtered. However, some of the mother liquor could not be separated from the product, which adversely affects quality.

Kovasavmentesített caustic mole ratio of about 8 aluminátoldat hidroaluminátot obtained by concentration of alkali metal (LP Ni, LG Romanov: Physico-Khimiya gidroschelochnykh sposobov proizvodstva glinosema, AHM Ata 1975, "Nauka" rent, 237 pp.) 460 540 g / Me ₂ O by focusing on content. The product is paste-like, difficult to filter, yields up to 70%, but the product contains a lot of mother liquors, which is also apparent from the molar ratio of alkali metal oxide to aluminum oxide: Me ₂ O, Al ₂ O ₃ = 2.2. The water-containing product packaging :! and transportation is problematic.

Kovasavmentesített, 13-1> alkali hidroaluminátot obtained also by drying and granulation in the fluidised state aluminátoldat Na ₂ O containing 100-350 g / l (250 to 350 ° C, 3 min), the molar ratio caustic addition 6th The heat exchanger used is carbon dioxide-free air. The product is in the form of a dry granulate but has a high cost because it is dried and crystallized in an oven, which makes the process energy intensive. It is also disadvantageous that a large fraction (27%) of air is removed from the furnace.

From the above, it appears that modernizing the production of alkylphenol hydroaluminate, simplifying the process, increasing yields and reducing energy demand is a modern problem.

SUMMARY OF THE INVENTION The object of the present invention is to provide a process by which alkali metal hydroaluminate can be produced in a simple manner with less energy, higher yields and better quality.

The above task is accomplished by a process comprising digesting the raw material containing aluminum and alkali metal oxides, removing the resulting aluminum slurry by silica and evaporating, and then crystallizing the alkali metal hydroaluminate. The process according to the invention is characterized by starting from a caustic molar ratio of 1.1-1.7, the solution is concentrated at 120-150 ° C to an alkali metal oxide content of 350400 g / l, and then the solution at 95-150 ° C is 10-95 ° C. a temperature moving moving filter surface where the product is crystallized and separated and recycled to digest the raw material.

Compared to known processes, the process of the present invention simplifies the technology, reduces energy consumption in the evaporation and crystallization step, improves product quality and reduces chemical consumption.

Preferably, the evaporation is carried out in two stages; in the first step at 120 ° C, the solution was 225-230 g / l Me ₂ O-21

It is concentrated to 198,426, while in the second stage at about 150 ° C, e.g. Continue to concentrate until the alkali metal oxide content is 360-370 g / l. Two-stage evaporation requires less heat carrier (steam).

It is preferred that the aluminate solution is allowed to stand at 95-105 ° C for 2-3 hours after the second evaporation until the alkali metal oxide concentration reaches 385-395 g / l. During this time, the crystallization conditions improve.

The crystallization is carried out on a moving filter surface, preferably at a surface temperature of 20-50 ° C (this temperature is easily maintained under industrial conditions). On the filter surface, the alkali metal hydroaluminate rapidly crystallizes out of the mother liquor. Suitable filter surfaces include polyamide fabric, woven metal mesh and other suitable filter materials.

The process of the invention will be described in more detail below (the embodiment described corresponds to the most preferred embodiment).

Aluminum-containing raw materials such as nepheline and limestone are comminuted to a grain size of 80-95 microns. Nefelin, limestone, and alkali metal oxide are mixed so that the CaO: SiO ₂ molar ratio of the powder is 2.1: 1, and the molar ratio of Me ₂ O: (Al ₂ O ₃ + Fe ₂ O ₃ ) is 0.95 to 1 (Me = Na, K). The powder mixture is sintered in a rotary oven at 1150-1250 ° C. The sintered product is crushed and leached with an aluminate solution of 1.63-

At a caustic molar ratio of 4.2, it contains 14-30 g / l Al ₂ O ₃ , 35-36.5 g / l Me ₂ O, 0.5-0.7 g / l SiO ₂ . The concentration of the solution increases with leaching, but its caustic molar ratio decreases to 1.1-1.7.

The insoluble matter was filtered off from the resulting aluminate solution and the solution was de-silica to a residual SiO ₂ content of 0.05-0.07 g / l. The silica precipitated in the form of a white slurry is separated.

Most of the silica-free aluminate solution is used as starting material for alumina, potassium carbonate and soda, while the other portion is used to prepare alkali metal hydroaluminate. The caustic molar ratio of the starting alkali should be 1.1 to 1.7. This molar ratio occurs automatically when leaching the sintered feedstock when leaching with the above concentration of alkali. The specified molar ratio is concentrated at 120-150 ° C to 350-400 g / l Me ₂ O.

The evaporated alumina liquor does not corrode standard steel equipment, which is due to the presence of alkali metal oxides in the form of aluminate ions in the chemically bonded state.

If the alumina solution has a Me ₂ O: Al ₂ O ₃ ratio greater than 1.7, the product is difficult to crystallize because the Me2-Al ₂ -Al ₂ O ₃ system is relatively stable at 120-150 ° C. A caustic molar ratio of less than 1.1 is also undesirable because at the process temperature, the solution is supersaturated from alkali metal hydroaluminate, crystallizes too quickly, and the evaporators are clogged with precipitated crystals.

Evaporation of the caustic molar ratio of 1.1-1.7 produces a saturated alkali metal hydroaluminate solution, which is crystallized by passing a solution of 95-150 ° C onto a moving filter surface of 10-95 ° C. The knees are almost immediately removed from solution. The warm solution also warms the filter surface, so it must be cooled. In order to maintain a temperature between 10 ° C and 95 ° C, a refrigerant, preferably water, is introduced to the other side of the filter (or, for example, to the part of the filter which is not working). Cold water at +5 ° C cools the filter surface to 10 ° C. If the temperature of the filter surface exceeds 95 ° C, the rate of crystallization decreases and the product precipitation is not efficient enough. At temperatures below 10 ° C, the viscosity of the aluminate solution increases, forming a crustal layer on the filter surface, which prevents further crystalline deposition. Therefore, the specified filter surface temperature must be adhered to.

On a properly cooled filter surface, salt precipitates rapidly. The separated mother liquor in the filter is recycled to the leaching step, thus utilizing the alkali metal hydroxide in the mother liquor and saving the chemical.

The resulting alkali metal hydroaluminate is a homogeneous, crystalline, white product consisting of an alkali metal salt and aluminum trihydroxide of the formula Με2θ · Α1 ₂ Ο ₃ · 2.5Η ₂ ,, where Me represents sodium or potassium. The product is freely soluble in water and carbonates during storage (formation of a thin film of carbonate); the product has a hygroscopic bulk density of 1280-1320 kg / m ³ , prone to adhesion. The product is very pure, having a composition of 25-38% by weight Me ₂ 0. 37.5-44.5% by weight Al ₂ O ₃ , up to 0.1% by weight SiO _; ., up to 0.02% Fe ₂ O ₃ , 20-25% moisture. The molar ratio of alkali metal oxide to aluminum oxide is 1.1 to 1.4.

Compared to prior art processes, the process according to the invention has the following advantages:

- energy consumption is reduced by 5.5-8%;

- product yields 8.5-26% higher;

- the evaporation and crystallization step technology is simpler;

- the recovery of the solution used for leaching also results in recovery of the alkali content in the mother liquor.

Within the above parameter ranges, the following is particularly preferred. Aluminum-containing raw material, such as nepheline, is crushed to a particle size of 80 microns. The following oxide molar ratios were set: CaO: SiO ₂ = 2.05: 1 and Me ₂ O: (Al ₂ O ₃ + + Fe ₂ O ₃ ) = 0.95: 1. The mixture was sintered in a rotary tube furnace at 1200 ° C, followed by Me ₂ O: Al ₂ O ₃ = 1, 634.2 at a caustic molar ratio of 14-30 g / l AhO ₃ , 35-35.5 g / l Me ₂ The sintered product is leached with a second solution containing 0.5-0.7 g / l SiO ₂ . After leaching, the caustic molar ratio of the solution is 1.1 to 1.7.

After filtration, the aluminate solution is desulfurized to a residual SiO ₂ content of 0.07 g / l. The white slurry produced during the silica blow is separated and returned to the mixing stage at the beginning of the live writing.

The aliminate solution was evaporated. In the first evaporation step at 120 ° C until a content of 225-230 g / 1 Me ₂ 0 is reached,

Concentrate the solution in the second stage at 135-150 ° C to a content of 360-370 g / l Me ₂ O at 135-150 ° C. Two-stage evaporation is preferred because it is more productive and efficient.

During evaporation, a solution of aluminate saturated with alkali metal hydroaluminate is formed, which is left at 95-105 ° C for 2-3 hours, when its alkali metal oxide content rises to 385-395 g / l. The solution is now supersaturated, dense, with an alkali metal oxide molar ratio of 2.05. The dense solution is passed to a filter surface consisting of a woven metal mesh at 50 ° C where the product crystallizes and separates from the mother liquor. Filtration combined with crystallization results in a reduction of the crystallization time, an increase in the yield, and a more efficient separation.

The mother liquor is recycled to leach the sintered starting material to save caustic soda.

The procedure detailed above has the following advantages:

- in the case of single-stage evaporation, the product may be deposited on the walls of the evaporator, which may impair the thermal characteristics of the evaporation. Therefore, two-stage evaporation is preferred, whereby in the first stage an alkali metal oxide concentration of 225-230 g / l is achieved at 120 ° C. Such a solution is not yet saturated and the substance is dissolved. In the second step, the solution is evaporated to a content of 360 370 g / l Me ₂ O at 135-150 ° C, increasing the evaporation temperature decreases the viscosity of the solution, while increasing the solubility of the alkali metal hydroaluminate, thus precipitating a solid phase product. , ie no product is deposited on the evaporator walls. It is recommended that the saturated viscous solution be allowed to stand at 95-105 ° C for 2-3 hours, during which time the alkali metal oxide concentration rises to 385-395 g / l. The position positively influences crystal formation. The product is then crystallized on a moving filter surface at 10-95 ° C. The filter is cooled with running cold water. With the two-stage evaporation described, the process energy (primary steam) is not high.

The invention will now be further illustrated by the following examples.

Example 1

278.4 kg nephron ore (20.8 wt% Me ₂ 0, 34.2 wt% Al ₂ O ₃ , 3.5 wt% Fe ₂ O ₃ , 43 wt% SiO ₂ , others: other) and 490 kg limestone (54 wt.% CaO, 2 wt.% SiO ₂ , the rest: other) was reduced to 85 micron particle size and mixed with 330 kg water. The CaO: SiO ₂ molar ratio was 2.05 and the Me ₂ O: (Al ₂ O ₃ + Fe ₂ O ₃ ) molar ratio was 1. The mixture was sintered in a rotary tube furnace at 1200 ° C, crushed and then 35 g / l of alkali metal. oxide, 30 g / l solution of Al ₂ O ₃ (Me ₂ O: Al ₂ O ₃ = 1.93). The solution obtained after leaching is filtered, its composition (g / l):

Me ₂ O 72.5

A1 ₂ O ₃ 109

SiO ₂ 0.6 caustic molar ratio: 1.1.

The solution was desulfurized (0.05 g / l SiO ₂ ) and the resulting white slurry was filtered and recycled to make the Ki4 starter mixture. The filtered aluminate solution (1 m ³ ) is placed in a film evaporator where it is concentrated at 120 ° C to a concentration of 350 g / l of alkali metal oxide. The remaining 0.206 m ^{3 of} solution at 120 ° C is passed from the evaporator to a moving filter surface, the filter surface consisting of a polyamide fiber and an in-line filter. The non-operating filter is supplied with 5 ° C water continuously, resulting in a filter surface temperature of 10 ° C. The cooled filter immediately separates the product and separates it from the mother liquor. The mother liquor contains at a caustic molar ratio of 1.93 35 g / l Me ₂ O and 30 g / l Al ₂ O ₃ . The mother liquor is returned to the leaching step. Yield: 63 kg (68.5% of theory), Composition:

Me ₂ 0 25% A1 ₂ O ₃ 37.5% SiC) ₂ 0.051% Fe ₂ O ₃ 0.02%

Me ₂ O: Al ₂ 0 = 1.1 Moisture: 25%

The product is a bulk white solid, commercial product.

Example 2

280.3 kg of nephron or 521.7 kg of limestone - the composition of the materials as in Example 1 - is chopped to a size of 80 microns. To the combined flour was added 335 kg of water. The resulting mixture has a CaO: SiO ₂ molar ratio of 2.1 and Me ₂ O: (Al ₂ O ₃ + Fe ₂ O ₃ ) molar ratio of 1.1. The mixture was sintered in a rotary tube oven at 1250 ° C and leached with a solution containing 35 g / l of alkali metal oxide and 14 g / l of Al ₂ O ₃ (Me ₂ O: Al ₂ O ₃ = 4.1). The composition of the solution is as follows:

Me ₂ 0 72.5 g / l

THE! ₂ O ₃ 70 g / l

SiO ₂ caustic molar ratio 0.1 g / l: 1.7.

The SiO ₂ content of the deacidified solution is 0.05 g / l. The white sludge formed during silicon removal is separated by filtration and returned to the beginning of the process. The solution was evaporated in a film evaporator at 150 ° C to 400 g / l Me ₂ O. The remaining 0.182 m ^{3 of} solution (temperature: 150 ° C) is passed through a movable filter surface made of polyamide fiber fixed on its pouring filters, the temperature of which is maintained at 95 ° C by passing 30 ° C of water to the non-working surface of its filters. The product crystallizes immediately and is separated from the mother liquor. The mother liquor containing 35 g / l Me ₂ O and 14 g / l Al ₂ O ₃ (caustic molar ratio: 1.7) is returned to the leaching step. Yield: 56 kg (80%). composition: 36.5 weight percent Me Cl _2, 43% A1 ₂ O _3, 0.07% SiO _2, 0.02 wt ') Fe ₂ O _3, remainder being bound water of Me ₂ 0 and A1 ₂ O ₃ molar ratio: 1.4, moisture content: 21%. The product is a bulk white powder which is commercially available in this form.

example

Nephrine ore having the composition given in Example 1

280.3 kg and given in Example 1

490 kg of 198,426 limestone were crushed to 85 micron particle size and then mixed with 330 kg water. The mixture had a CaO: SiO ₂ ratio of 2.05 and a Me ₂ O: (Al ₂ O ₃ + Fe ₂ O ₃ ) ratio of 1.05. The material was sintered in a rotary tube oven at 1200 ° C and then leached with a solution containing 35 g / l Me ₂ O and 21.5 g / l Al ₂ O ₃ (caustic molar ratio 1.63). After filtration, the composition of the solution is as follows:

Me ₂ 0 72.5 g / l

A1 ₂ O ₃ 80 g / l

SiO ₂ 03 g / l

Me ₂ O: Al ₂ O ₃ = 1,5.

The solution was decontaminated with SiO ₂ content of 0.05 g / l, while the concentration of the other components remained unchanged. The white slurry is separated and recycled to the beginning of the process. The solution was evaporated in a film evaporator to a content of 375 g / l Me ₂ O at 135 ° C. The remaining 0.95 m ³ solution at 135 ° C is returned to the filter described in Example 2, where the temperature of the filter surface is maintained at 5 ° C with 20 ° C water.

t

The alkali metal hydroaluminate crystallizes. The mother liquor containing 35 g / l Me ₂ O and 213 g Al ₂ O ₃ (Me ₂ O: Al ₂ O ₃ ratio: 1.63) is recycled to the leaching step. The product yield was 583 kg (yield 73%), composition: 30.5 wt% Me ₂ 0, 39% by weight Al ₂ O _3, 0.06 wt% _SiO2, 0.015% Fe ₂ O _3, the rest of the water is in knitted form. Me ₂ O: Al ₂ O ₃ ratio: 13, moisture content 22.5%. The product is a crystalline bulk white powder.

Example 4

280.3 kg of nefe and some 521.7 kg of limestone (the composition of the raw materials as in Example 1) were crushed to 80 micron particle size and then mixed with 335 kg of water. The CaO: SiO ₂ ratio is 2.1 and the molar ratio of Me ₂ O: (Al ₂ O ₃ + Fe ₂ O ₃ ) is 1.1. The material was sintered in a rotary tube oven at 1250 ° C and then leached with a solution containing 363 g / l Me ₂ O and 143 g / l Al ₂ O ₃ (molar ratio 4.2). After filtration, the composition of the aluminate solution is as follows:

Me ₂ 0 72.5 g / l

AliOj 70 g / l

SiO ₂ 0.1 g / l

Me ₂ O: Al ₂ O ₃ = 1.7.

The solution was decontaminated with SiO ₂ content of 0.05 g / l, while the concentration of the other components remained unchanged. The white sludge from the silica removal is recycled to the beginning of the process. The solution is evaporated in two stages, first in a film evaporator at 120 ° C to 230 g / l Me ₂ 0 and 0.16 g / l SiO ₂ , and in a second stage also in a film evaporator at 135-150 ° C 370 g / 1 Me ₂ 0 and 0.25 g / l SiO _{2 are} paired with the 0.315 m ³ solution remaining after step 1. The 150 ° C solution (0.195 m ³ ) exiting the second evaporator is charged to a crystallizer with stirring, where at 105 ° C

Allow to stand for 2-3 hours until the concentration of alkali metal oxide is 385-395 g / l. The decrease in temperature and the increase in alkali metal oxide concentration are the result of the solution's own evaporation. Me _{2 is concentrated to} 0 390 g / l and SiO ₂ is concentrated to 0.26 g / l. The thickened solution (0.185 m ³ ) contains 360 g / l Me ₂ O and 290 g / l Al ₂ O ₃ (caustic molar ratio: 2.05) at 105 ° C. The solution is passed to a metal mesh filter screen, which is located in a filter drum. The inactive portion of the filter was cooled with water to 95 ° C. Crystallization and isolation of the product and recycling of the mother liquor are carried out as described in the previous examples.

Yield: 60 kg (86%), Composition: 38% Me ₂ 0, 443% Al ₂ O ₃ , 0.06% SiO ₂ , 0.01% Fe ₂ O ₃ , other bound water, Me ₂ 0: Al ₂ 0 ₃ = 1.4, Humidity 20%. The product is a bulk white powder.

The preparation of alkali metal hydroaluminate described herein is an industry; localization: processing of aluminum-containing ores, such as nephels, bauxites, and aluminum-containing wastes from the chemical, metal and other industries to produce alumina, soda and potassium carbonate; in alumina production, a small portion of the aluminate solution from the leaching of the raw material (sintered material) can be used to produce alkali metal hydroaluminate. Alkali metal hydroaluminate is used in the pulp and paper industry, petroleum extraction, mining, foundry and water facility construction.

comparison between the process according to the invention and the method according to the state of the art (G. A. Panasko and I. I. Smimova, "Poluchenie natrijevoj kausticseszkoj Svlochi ...", 1970, Moskau, "Metallurgy", pp. 126-134).

Parameter Known process Invention of process The caustic molar ratio of the hydroaluminate produced 1.68 to 2.07 13-1.4 cycle time (hours) 10-12 0.1-3 crystallization temperature ° C 60 10-95 yield of alkali metal hydroaluminate,% 60-80 683-86.0 purity of mother liquor (% of Fe ₂ O ₃ ) 0.1 0.01

The yield of the final product is calculated as follows:

He ~ dh where dm - Caustic molar ratio of mother liquor d _a - Caustic molar ratio of alumina dh - Caustic molar ratio of hydroaluminate

Claims (5)

Claims A process for the preparation of an alkali metal hydroaluminate by digestion of a raw material containing aluminum and an alkali metal oxide, deacidification and evaporation of the resulting alumina base, and crystallization of the alkali metal hydroaluminate, characterized in that ca. the solution is evaporated to an alkali metal oxide content of 120-150'Con 350-400 g / l, then the 95-105 ° C solution is passed to a 10-95 ° C mobile filter, whereupon the product is crystallized and separated and the mother liquor is recycled to explore the raw material. A process according to claim 1, characterized in that the aluminate solution is evaporated in two stages, the first stage at 120 ° C to 225-230 g / l of alkali metal oxide and the second stage 135-150 ° C. on an alkali metal oxide content of 360-370 g / l. 3. The process according to claim 1 or 2, wherein after evaporation, the aluminate alkali is allowed to stand at 95-105 ° C for 2-3 hours to reach a content of 385-395 g / l of alkali metal oxide. 4. The process according to any one of claims 1 to 3, characterized in that the product is crystallized on a filter surface at 20-50 ° C. 5. A method according to any one of claims 1 to 3, characterized in that the filter is a polyamide fiber fabric or a woven metal mesh.