DE1145596B - Process for cleaning aluminate liquors - Google Patents

Description

The invention relates to a method for cleaning products produced in the manufacture of alumina Sodium aluminate liquors, especially for the aftertreatment of those that have been pre-cleaned by settling Aluminate liquors.

In the sodium aluminate liquor, which is produced in the alumina production, are also after the with the usual cleaning methods that are very difficult to remove, some floating, some loosened particles Contain iron oxide, titanium oxide and silicon dioxide.

The sodium aluminate liquor can contain these impurities can only be cleaned by cumbersome costly procedures. With regard to the fact that At the moment ever greater demands are being made on the alumina with regard to purity, it appears It is very important that the above-mentioned components are as simple and inexpensive as possible from the Naitrium aluminate eye must be removed before the Stirring begins.

According to the process of the invention, the sodium aluminum hydroxide solution is prepared by one of a mixture Filter layer formed by limestone or dolomite and coke grit with a grain size of 1 to 4 mm, with the temperature of the aluminate liquor Maintained between 90 and 100 ° C during this filtration and expediently one at the beginning of the filtration preheated, e.g. B. filter sheet preheated with steam is used.

The limestone is expediently used in a quality which is also suitable for the production of quick lime; such limestone contains on average over 90% CaCO ₃ . But dolomite or marble quarry can also be used. It is expedient to use 0.5 to 2.0 parts by weight of limestone or dolomite per part by weight of coke.

In an advantageous form of the filter layer, a mixture of carbon-containing minerals and Coke stored between two layers of coke. The sodium aluminate liquor to be cleaned should be passed through be 90 to 100 ° C through the filter layer. The entire filter surface is advantageous with steam preheated before the liquor is fed to the filtration. The filter layer can easily pass through Leaching can be regenerated with water, advantageously in such a way that the hot wash water in countercurrent is fed.

There have been methods of purifying sodium aluminate liquor by filtering it over from it granular minerals existing filter layers described; so it was already for this purpose filtering over coke pellets or milled

Process for the purification of aluminate liquors

Applicant:

"Mineralimpex" Magyar Olaj-

es Bänyatermek Külkereskedelmi V.,

Budapest

Representative: Dr. G. W. Lotterhos

and Dr.-Ing. H. W. Lotterhos, patent attorneys,

Frankfurt / M., Lichtensteinstr. 3

Claimed priority:
Hungary from July 25, 1958 (No.KU-298)

Dipl.-Ing. Andor Kutas, Dipl.-Ing. Lajos Bartha,

Budapest,
and Dipl.-Ing. Endre Bogardi, Mosonmagyarovar

(Hungary),
have been named as inventors

Lenen limestone to remove the iron and titanium dioxide content proposed the aluminate liquor (cf.

Fulda-Ginsberg, "Clay and Aluminum", Part I: "The Clay", 1951, pp. 58 and 71). To remove the SiO ₂ content, treatment of the aluminate liquors with basic magnesium carbonates was also recommended (cf. German patent 752739). However, this known method can only incompletely remove the above-mentioned impurities and with rather poor success.

It has been found that by using one of a mixture of coke and limestone or dolomite existing filter layer an unforeseen and by separate application of the individual, per se known filter maizeirialien by far unattainable degree of cleaning can be achieved. The filter material to be used according to the invention binds not only iron but also silicon dioxide, and theirs is particularly noteworthy high cleaning effect with titanium dioxide.

As can be seen from the comparative tests summarized in the table below is, the cleaning effect achieved by the filter material to be used according to the invention can neither by applying a simple layer of coke

309 540/346

Claims (7)

or a limestone or dolomite layer can be achieved by using any other known filter material. This effect cannot be achieved even if the lye is passed through these layers one after the other. In order to remove the pre-impurities in the lye overflowing from the Dorr apparatus, comparative tests were carried out in the laboratory with a filter apparatus with a volume of 4 liters. A filter thickness of 100 mm in diameter and 500 m in height was used in the tests, and caustic at 90 to 100 ° C. was passed through this layer 501. The composition of the materials used is given below. The grain size of the filter substances, the flow rate of the lye and the contamination of the aluminate lye before and after filtering are also given. Filter material flow-through VELOCITY impurities in the aluminate mg / 1SiO2TiO2nach the FilternFe2O3SiO2TiO2keit1756 • 20170; 6The 11 Lauge1807181504in Sekundenvor the Filtern16551490365Fe2O315046100470251827151104702818061280365'241726240165231726250275296027602626 pebbles, 2 to 4 mm dolomite, 2 to 4 mm .. limestone, coke 2 to 4 mm, 2 to 4 mm pebble + limestone ... dolomite + limestone. Coke + limestone coke + dolomite. From the table it can be seen that dolomite or limestone, combined with coke, produces an unexpected and special effect. This effect is particularly surprising in the case of titanium dioxide, the amount of which is reduced to a third to a sixth after filtration. This is all the more surprising because the titanium dioxide is contained in the aluminate liquor in finely divided colloidal or dissolved form. The process of the invention removes the iron oxide as well as the silicon dioxide from the aluminate liquor as far as possible. The invention is explained with reference to the drawings, for example. Fig. 1 shows the longitudinal section of the Fiitaierapparates; Fig. 2 represents the curves of the Fe 1 Og content during a 62 day test period. The cylindrical container 1 is provided with a connecting lead 2 at the bottom and a connecting line 3 at the top. The wire mesh 5 is arranged on the ribbed insert 4 and the coke grit layer 6 is arranged on the wire mesh 5. The filtecfilling 7, formed from a mixture of 2 to 4 mm large dust-free chalk stone grains and coke granules, lies on this coke grit layer. The filter layer 7 is closed by the coke grit layer 8 with a grain fineness of 4 to 6 mm finned weight 10 fixed; will. The gas suction line U and the manometer 12 are arranged on the upper part of the apparatus. At the bottom of the filter apparatus is a. Manhole 13 provided !. During operation, the 90 to 100 ° C. warm sodium aluminate liquor to be filtered is introduced through the line 14 and through the nozzle 2. The filtered aluminate liquor is discharged through line 17. If the apparatus is to be cleaned, hot washing water is introduced through line 15. The washing water is discharged through line 16. The usable space of the device is 1.2 m3 and the filter surface 0.5 m2. The filter filler consists of a 1: 1 mixture of limestone and high-strength blast furnace coke of 863 1 volume. This mixture is advantageously composed of 2 to 4 mm large granules with a total weight of 900 kg. The coke layers 6 and 8 are formed from granules of 4 to 6 mm and have a volume of 3001 and a total weight of approx. 200 kg. Before the start of the filtration, the filled filter container was fed through line 16 and through the nozzle. 2 Steam introduced until the temperature of the filter filling reached approximately 100 ° C; The aluminate liquor to be filtered was introduced into the apparatus from below through line 14 and through nozzle 2 under 0.5 atmospheres. At the beginning of the filtration 50 l of aluminate liquor were introduced per minute. This rate was then increased up to 701 per minute. The filtration lasted 6 days, after which the filter apparatus was washed out in such a way that the hot washing water was introduced through line 15 and carried away through line 16. The curves in FIG. 2 illustrate the results for 2 months. Every sixth day, a total of eleven times, the filter apparatus was washed out. The FegOg content in milligrams, per liter of the aluminate liquor to be filtered was drawn with a voiei line, that of the filtered liquor was drawn with a thin line. These curves show that the considerable fluctuations in the F ^ Og content in the liquor to be filtered no longer occur in the filtered liquor1. Of particular note is that the performance of the filter between the seventh and eleventh washes has shown even better results than the initial filter performance. g5 PATENT CLAIMS: 1. Procedure for cleaning the ToDr Sodium aluminate lye produced in the earth's production, in particular for the aftertreatment of the put purified liquor by filtration using fine-particle coke or limestone, characterized in that the sodium aluminate liquor is passed through a filter layer formed from a mixture of limestone or dolomite and coke grit with a grain size of 1 to 4 mm, the temperature of the alumina eye during filtration is kept between 90 and 100 ° C and at the beginning of the filtration expediently a preheated, z. B. Preheated with steam Filterschidht is used. 2. The method according to claim 1, characterized in that the Nafaiumaluminatlauge a filter layer (7) is guided through the bottom and top through layers of coke grits (6, 8) is completed. 3. Method according to Anspnich 1 or 2, thereby characterized in that the filter layer consists of 1 part by weight of coke and 0.5 to 2 parts by weight There is limestone or dolomite !. Considered publications:
German Patent No. 752 739;
Fulda-Ginsberg: Clay and Aluminum, I. Part, 1951, pp. 58, 71. 1 sheet of drawings © 309 540/346 3.63