DD200896A1 - METHOD OF OBTAINING THE ALKALINE CONTENT OF INDUSTRIAL SUPPLIES - Google Patents

Abstract

The invention relates to a process for the recycling of ferrous and alkaline industrial residues, in particular alkali-rich red mud from bauxite processing according to the Bayer process. The object of the invention is to obtain pig iron and liquid calcium silicate-aluminate slag by means of a special mixture of the batches and an improved reduction melt such that in particular the alkali content of the industrial residue can be completely recovered. According to the invention, the object is achieved by adding enough lime to the mixture of lotion to form at least 20% calcium disilicate in the slag at levels of more than 45% CaO, bound TiOind2 as calcium titanate and Alind2Oind3 as calcium aluminate. The alkali contained in the industrial residue is quantitatively evaporated only during the melting process and recovered to more than 99% as fly ash. The iron content of the industrial residue is completely applied as a high quality iron alloy.

Description

Υerfehren, "to win ..,. Alkali content, industrial residues

The invention relates to a process for the residue-free recovery of iron and alkali-containing industrial residues, especially of alkali-rich Rotschlam-men from the bauxite after the Bayer process by reducing melting with the addition of coke, lime and sand, with an iron alloy and calcium silicate / aluminate slags , which then leached alkaline, the alumina content is applied and the lye residues are processed on cement and alkali dust are generated »

Characteristic of the known; technical solutions

The harnessing of the resulting in the wet pulping process from bauxite to alumina as a lifting product red s amine is a task that has been trying to solve for decades.

^ ?! β ?ήή ^ \ β β β β β β R R R R R R R R R R R R R R R R R R R R R R R R R Grund Grund Grund Grund Grund Grund Grund Grund Grund Grund Grund Grund Grund Grund Grund Grund Grund Grund Grund Grund Grund und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und und Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot Rot This also applies to the process of reducing the treatment of the hot-bath with the aim of obtaining the iron and alkali content and a slag containing the remaining components of the red mud.

The following technological possibilities of thermal red-mud processing have been investigated so far;

1 "Combined Bayer sintering process after the Krupp-Renn process, magnetic separation of the resulting iron slag from the slag, subsequent sintering of the slag with soda and limestone and leaching of the sintered product»

2 * Reducing smelting for the production of pig iron and sintering of the slag with soda and limestone «.

3. Reducing red mud melting and treating the molten slag with lime to form directly leachable sodium and potassium aluminate slag

4. Causticization of the Red Smelter and Subsequent Melting to Form a Self-Degrading, Directly Leachable Calcium Aluminate Calcium Disilicate Slag *

The leaching after o, g. Slag remaining sludge is processed into cement by all processes and the aluminate liquor is fed to the Bayer process.

From DE-OS 2328674 it is known that red mud is melt-reducing with the addition of certain amounts of lime, the resulting iron alloy by magnetic separation or in the molten state abgescherüt, the slag is ground and an alkaline leaching for the purpose of 'alumina and alkali extraction is subjected. The disadvantage of this method proposal is that due to the melting and reaction conditions no self-decomposing slag is formed, so that the large amount of slag must be ground at high cost and further that iron and alkali can not be completely recovered and converted into a usable product _e from the DD-AP 99971 is known that red mud subjected to a reduzieranden melting process and the cast iron obtained is liquid separated from the slag. The slag is ground with the addition of lime and homogenized, sintered, the sintered material in turn reduced and leached to the alkali and clay extraction It is not possible to influence the iron quality. Another aspect of the invention is a large number of comminution stages with high costs and incomplete

* ι s s ä ^ ^

13 3d I \ 6

Dea alkali-.Una iSiseninhaltes »From DS-OS 2807615 is known that molten slag from 1350 C a slow cooling

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of less than 10 C min, with a 3elb3tzerfall occurs and the disintegrating Schlakke is leached to the alumina extraction. The self-decomposition is accelerated by application of ultrasound at temperatures from <700 ⁰ C, a Bisengewinnung is not carried out, disadvantageous is the limitation of the cooling rate to less than

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10 C min, which requires high investment and processing costs in the realization.

According to DD-WP 11379, red mud is melted with the addition of reducing agents, hydrated lime and soda or other alkalis, the iron is separated off and the titanium is leached out of the slag. "The lye residue is processed in a known manner to form cement. The Bisenabtrennung takes place according to this proposal after grinding the melted or sintered product by magnetic separation, so that no complete iron extraction is possible, the alkali content is only used to 67%. According to DE-AS 1202297 red mud and other aluminum-containing raw materials are melted reducing, the iron separated and the slag sulfuric acid v / eiterbehandelt to obtain titanium Lind alumina "The alkali content of the precursors is not recovered by this procedure" The total amount of slag must be comminuted. It has also been proposed a process option in the DS-AP IO5OO4, red mud with lime in the ratio GaOsSiO ₂ = 1.8. "* 2.2; CaOsTiO ₂ «0.9 ....

1,1ΐ GaG ₅ Ie ₂ O ₃ - 1,8- ,, »2,2} CaOiAl ₂ O ₃ ZHa ₂ - 0 ... 12,7 to be mixed ^ to melt, to separate off the resulting iron in liquid form and to remove the sodium silicate and slag containing calcium aluminate and to be processed to alumina in a known manner. According to the given method, more lime is used than is necessary, since the Fe ₂ O _{3 is} reduced and is no longer contained in the slag, the alkali is recovered only to 61%, the iron to 90 % »The Aufmahlkosten for the slag very high"

From a Yugoslav method proposal (Heue hut, 1975, Issue 3) it can be seen that red mud melt-reducing melted, the resulting pig iron is separated and the slag is granulated. An alkali recovery is not provided, the slag must be comminuted before leaching with H ₂ SO ₄ finely »

In summary, it should be noted that according to the previously known method proposals, a red mud utilization is possible, which, however, shares the following after ists

- Iron and especially alkali are only partially recovered «

The methods consist in particular in the alkali extraction of too many costly Sinzeloperationen.

The favorable Schlackenselfbstzerfallsprozeß is due to the cooling conditions (cooling rate less than 10 ⁰ C min) difficult to reali Sieren and therefore costly.

The aim of the invention is an economical process for the complex and residue-free recycling of iron and alkali-containing industrial residues, preferably red mud, with all practically occurring alkali contents.

The invention has for its object to win by a special Möllermischung and an improved reduction smelting pig iron and liquid calcium silicate-Al uminat -Schlacke such that in particular the alkali content of the industrial residue can be completely recovered.

According to the invention, this object is achieved in that the lollipop mixture so much lime is added that at least 20% calcium disilicate are formed at levels of more than 45% GaO in.der slag, the TiOp as calcium titanate and the AIpO- be bound as calcium aluminate (iron can be neglected) and the slag produced in the melting process after tapping a cooling of not more than

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30 C min is subjected. The self-decomposition of the slag in the low temperature range to the particle size of <150 / _{to more} than 95 %. The remaining oversize is returned to the melting process. The alkali contained in the industrial residue is quantitatively evaporated only during the melting process and returned to more than 99% as fly ash.

CDR; cnnon. The ice content of the load residue is completely applied as a high grade ferrous alloy »

The process according to the invention utilizes the fact that the sodium compounds present in the slag are displaced by GaO at high temperatures, in particular in the electrode region of an electric melting furnace, the Ha released _. 0 evaporated and / or reduced with carbon to sodium, which is then evaporated and oxidized to NapO and removed with the furnace exhaust gases from the process. These are sufficient amounts of CaO ₃ greater than 70 % of the stoichiometric demand, for the formation of calcium disilicate, calcium aluminum silicate in calcium titanate required and further reducing agent, preferably carbon, in the form of coke and carbonaceous electrodes, the off. sufficient for Osidreduktion, alloying and alkali reduction, but at least 10%, based on dry industrial residue with, for example, greater than 25 % Pe ₃ O ₃ ,

In this case, a favorable for the formation of self-decomposing slag average melt bath temperature (simultaneously tapping temperature) of 1430 to 1450 G does not need to be exceeded and it is at the same time for the secured Schlackenselbstzerfallsprozeß maximum allowable alkali concentration of less than 1 % Na _? 0 set in the surprisingly short time of less than 5 min The inventive removal of the alkali from the red mud leads to a highly enriched alkali gas dust with

up to b / ^l Ma ₂ O + K "0, from which can be prepared by simple water leaching an alkali solution of any concentration, which contains up to 95 % of the leading in RotschlanM alkali and the slag leaching process for alumina extraction or the Bayer process can be supplied »

The direct use of alkali-dust is also possible «. In contrast to known methods, it has been found that with a composition of the slag characterized by a proportion of more than 20 % calcium disilicate, more than 50 % CaO and less than 5 % impurities, formation of non-self-decomposing compounds in the slag does not take place and a cooling rate of the slag is allowed up to 30 ⁰ C min, so that a complete self-decomposition after cooling to below 500 ⁰ C occurs in the interest of a favorable heat economy, a prereduction and preheating the Möllermischungen working in conjunction with an electric furnace, with cheap fuels heated rotary kiln.

Can be adjusted over a Schmelzkokszusatz for the electric furnace smelting of 10 to 25% and a residence time of the resultant by reduction of the ^ e ₂ O ,, and other oxides iron alloy up to 3 hours, the content of alloying elements, in particular! Titanium, silicon and carbon. Thus, it has been found that the titanium content can be lowered from 0.9 to 0.1 % in 3 hours and the silicon content from 0.5 to less than 0.1 % , with residence times

of 3 hours with intermittent tapping of the metal phase from an electric furnace can be achieved in each case. If such a residence time is maintained, direct melting to a metallurgically usable iron alloy is possible.

According to the invention, a slag with less than 0.1 % of PE is obtained and more than 99% of the iron is applied in the iron alloy if the slag is intermittently tapped at least 5 to 10 cm, preferably 10 cm above the phase interface metal slag.

It is proposed to supply the phosphine-containing exhaust air to the combustion in the prereduction or preheating process and thus render it harmless »

If the quantity of CaO required for the formation of calcium disilicate, calcium aluminate and calcium titanate is added to the red mud and also the other conditions according to the invention are maintained, the alkali can be more than 95 % and the iron completely soluble in red carbon with all practically occurring alkali contents an AIpO -, - yielding over 80 % can be won »

Au sf uh ru η gave eie Spie1

Filter moisturizer red mud with

8.47 to 16.6 % Al ₂ O ₃

6.59 ... H, 1 % SiO ₂

32.30 ... 39.7 % Pe ₂ O ₃

2.15 ... 4.3% TiO ₂

2.70 ... 23.8% CaO

1.90, ** 9.0% Ua ₂ O (+

0.16 ... 0.49% P ₂ O ₅

12,00 ... 14,00% loss on ignition

and about 48 % adhering moisture was dried in a rotary kiln to 6 % residual moisture, mixed with limestone grain size 10 mm and coke 10 mm and melted in a 450 kW Slektroofen. The addition of CaO in the limestone was calculated to give SiO ₂ as the calcium disilicate (2 CaO, SiO ₂ ), Al ₃ O ₃ as the calcium aluminate (12 CaO, 7 Al ₂ O ₃ ), and TiO ₂ as the calcium titanate (CaO "TiO ₂ ). could be tied. Since only 0.1 % Fe ₃ O was expected in the slag, a lime addition for Fe ₂ O. could be omitted, a 2 % excess was added only for the alkali reaction. The addition of coke was adjusted at 15 to 20 % according to the Fe ₂ 0 content of the red mud and the need for alloy formation and UapO reduction.

The average melt temperature was 1420 to 1450 ⁰ C, the temperature near the electrodes 1700 to 1800 ⁰ C and the Vervveilzeit was limited to 1, 5 hours. After melting the batch

From about 380 kg in 1 hour or continuous melting with intermittent tapping the slag was tapped into pans and cooled with ca '60 G min "of bath temperature to about 1200 ⁰ G and then with 30 ⁰ G min" ¹ . The slag fell to 95 to 98 % in grain sizes preferably 80 / Um and the remainder 150 / Um at 200 kg blocks in less than 2 hours, when the temperature was reached below 500 ⁰ C, in yellowish green to gray powder, the hydrometallurgical slag leaching was supplied.

The exhaust gas from the electric furnace with ca * 1100 G was cooled with false air and water to about 120 ⁰ C and dedusted in normal fabric filters. The filter dust contained little amount of primary grain, was easily separated from the filter and was then leached with water.

The iron alloy obtained was either tapped in batches after the selected residence time in the furnace or after collecting a larger amount in continuous operation and screwed.

The following results were obtained in the experimental investigations?

1. Alkaline recovery

Alkaline evaporation in electric furnace % 99.8

Alkali recovery in flue dust % 99

Grain analysis of the flue dust. %

0.001 mm 15

0,001 0,002

0.002 mm 0.003 mm

Ö _s 005 mm

Plugs deafness 18. 26.6

on

17.3

25 . " , 60 % Ia ₂ 1 , 11 % Al ₂ 2 * " , 7 % CaO 2 , 6 .. , 6 % SiO 0 ,1.. , 0 , 2% TiO

Alkaline release from the plug dust by water leaching

2. Slag utilization rate of self-destruction

Analysis of slag .-; "95

98

cooling regime

50. 54 % CaO 70 ⁰ C min "off 18 17.6. .. 22 ·· 20, % 2% Al ₂ O ₃ SiO ₂ C 30. 0.05. .. % Pe ₂ O ₃ 5 ⁰ C min " ¹ 1.51. •. 6 % TiO ₂ 0.1. ..% Eg ₂ O 0.1 % K ₂ O 0.2. .. 0, 3% C 0,5. ·· 0, 7% S from bath tempera door 1450 ⁰ C to ca, 1200 ⁰ C with 50 ... 1200 °

Al ₂ O "removal in slag leaching

82

/O

Analysis of the Lauger Licks tandes

Iron analysis (after melting)

3.6 .. 54.4 .. , 4. 57 , 3, 7 ^{/ 0 A} 2 3% GaO 20.5 ".. , 21 , 9 % SiO ₂ 0.05 % Fe ₂ S ₃ 1.50 % TiO ₂ 12 , 14 % Annealing

3 «Metal extraction

Iron yield % 99.6

Iron analysis (residence 1 ₅ 5 h 15% coke addition)

0.3 , 0 % Si 0.2 C ^ rp-i / ί? Χ JL 0.3 .c , 5% Mn 0.01 , 0 Cf q 0.1 , 0 % Al 0.2 _e . , 5 , 4%? 0.3 .. 0 , 4% Y 4.2 _e . 0 , OfO C , 5% Si , 9% Ti

Rotschlamin v / ird in a rotary kiln pre-reduced together with a subset of coke and limestone and supplied in the preheated state directly to a downstream electric furnace with the remaining amount of reducing coke and further treated according to Example 1.

Claims (2)

Inventive a nsp rueη "Κ Process for recovering the alkali content of industrial residues, preferably alkaline reds from bauxite processing by the Bayer process, by reduction melting with addition of coke, lime and sand in the electric furnace, producing pig iron and calcium silicate-Z aluminate slag, the latter for spreading the clay content leached alkaline and the lye residues are processed on cement, the lime mixture is added so much lime that at least 20 % calcium disilicate are formed at levels greater than 45 % GaO in the slag, the on. falling slag intermittently or continuously at least 10 cm above the phase interface metal slag tapped and after reaching the Solidustempera door cooling to not more than 30 ° C / min is subjected and the alkali contained in the industrial residues evaporated during the melting phase and in Plugstaub together with the accompanying elements may be present in the industrial residues, such as rare earths _s gallium, selenium u. a, is won · 2. The method according to item 1, characterized in that the carbon black reducing agent added to the industrial residues in the preparation of the Möllermischung v / earth, that together with the existing in the industrial residues carbon Together, about 10 to 25 % dry matter of Industrieriickstände, in addition to the reduction of iron oxides and the oxides of the accompanying elements in particular the reduction of the alkali content is ensured and at the same time the carbon demand of the forming iron alloys is taken into account.