RU2441927C2 - Method for alumina industry slag treatment - Google Patents

Abstract

FIELD: metallurgy. ^ SUBSTANCE: invention relates to the area of iron-and-steel industry, to alumina industry slag treatment (red mud) in particular and may be used for ferrosilicon alloy production. The reduction melting shall be performed in an ore thermal furnace. Alumina industry slag shall be intriduced into the furnace charge in the amount of 10 to 81 mass % of the total of silicon oxides in the furnace charge, wherein the furnace charge contains quartz stone with the following component ratio, mass %: alumina industry slag 25-53, carbon reducing agent 13-24, quartz stone 26-52. ^ EFFECT: enhanced slag treatment and production of ferrosilicon at low energy costs. ^ 1 tbl, 6 ex

Description

The invention relates to metallurgy, in particular to the processing of alumina production waste - red mud, and can be used in the production of ferroalloys in ore-thermal furnaces.

The processing of sludge from alumina production with their subsequent use as metallurgical or chemical raw materials is one of the important technological problems of the aluminum industry.

Sludge, being poorly utilized waste from the production of alumina from bauxite, accumulates in sludge storages, thereby posing a threat to the environment, as it contains caustic alkali. Annually, up to 2 million tons of such waste is discharged into sludge fields, despite the fact that they are promising sources of valuable substances. The main components of the sludge are alumina (up to 30% Al ₂ O ₃ ), iron oxides (up to 60% Fe ₂ O ₃ ), silicon oxides (up to 15% SiO ₂ ), alkali (up to 9% Na ₂ O).

The problem of utilization and processing of sludge has long attracted the attention of researchers and producers. Sludge is considered as a potential source of obtaining practically useful products, such as alumina, caustic alkali, iron, etc.

A known method of processing red mud, including the processing of red mud [Complex processing and use of waste sludge from alumina production. Shmorgunenko N.S., Korneev V.I. - M .: Metallurgy, 1982. - P.128], in which the sludge is subjected to reduction smelting in an electric furnace mixed with limestone. In this case, cast iron and calcium aluminum slag are formed. Slag is further processed into alumina or cement. In addition, the method is quite time-consuming, requires significant capital costs, high energy consumption and is characterized by low quality of the resulting products.

Another analogue is a method including [Production of alumina. Liner A.I., Eremin N.I., Liner Yu.A. - M .: Metallurgy, 1978. - S.287-291] reduction smelting of red mud in a mixture with coal and slag-forming additives in blast furnaces or ore-thermal (arc) furnaces to produce cast iron and alumina-containing slag. However, the known method does not allow to obtain ferrosilicon, and the resulting cast iron contains a large amount of impurities and such cast iron as a commercial product is not in sufficient demand.

The closest in technical essence, adopted for the prototype is a method that allows you to process red mud of alumina production for ferrosilicon and alumina-containing slag (RU 2179590 C1, C22B 7/04, C04B 7/32, 02.20.2002). The mixture, consisting of a mixture of red mud, siliceous and calcareous components, was loaded into a heat treatment unit, the melt obtained at 1500 ° C was loaded into a bath, where it was heated to 1800 ° C, then it was purged with cold natural gas to obtain hot reducing gas, which used to obtain ferrosilicon.

The signs of the prototype, coinciding with the essential features of the proposed method are: the use as a charge mixture of sludge from alumina production, production of ferrosilicon and alumina-containing slag.

The disadvantages of this prototype method are the complexity of the process due to the large number of redistributions (multi-stage), in connection with this, the complexity of its hardware design, as well as the low quality of the obtained ferrosilicon.

The task of the invention is to obtain at minimal energy consumption using as an additive to the mixture of waste alumina production of a conditioned commercial product - ferrosilicon of various grades. The technical result of the claimed invention is to increase the efficiency of processing sludges from alumina production to produce conditioned ferrosilicon, as well as the production of alumina-containing slag - alumina or high alumina cement.

The technical result is achieved by the fact that in the method of processing sludge from alumina production, including loading into the furnace a mixture containing sludge from alumina production, a carbon reducing agent, reducing smelting to produce ferrosilicon and alumina-containing slag, according to the invention, a mixture containing alumina sludge is subjected to reduction smelting in an ore-thermal furnace production in an amount of 10 to 81 mass% of the total mass of silicon oxides in the mixture, quartzite in the following ratio of components, wt.%:

sludge from alumina production 25-53 carbon reducing agent 13-24 quartzite 26-52

Table The material composition of sludge from alumina production The content of basic oxides, wt.% Fe ₂ O ₃ Al ₂ O ₃ TiO ₂ Na ₂ O SiO ₂ Cao P.p.p. 22.0-60.0 13.0-20.0 0.9-5.0 2.0-3.0 5.0-15.5 12.0-25.0 11.20

Due to the presence of a large amount of iron oxide in the sludge, they can be attributed to iron-containing raw materials. Along with iron, they contain aluminum, silicon, titanium, calcium, sodium, rare earth and other elements [Red mud - properties, storage, use. Korneev V.I., Suss A.G., Tsekhova A.I. - M .: Metallurgy, 1991. - P.121].

The introduction of alumina production into the sludge charge in an amount from 10 to 81 mass% of the total mass of silicon oxides in the charge allows: to reduce quartzite consumption and not to introduce metal shavings into the charge, due to the sufficient iron content in the sludge; to improve the environmental condition of the enterprises of the aluminum industry. In addition, the use of waste from alumina production allows for the production of ferrosilicon with any amount of charge, since the sludge from alumina production is not scarce and its amount is very significant. Currently, sludge does not find industrial application and is stored in dumps.

It is known from the prior art to use iron-containing material as a reducing agent in a mixture, for example, when producing ferrosilicon in ore-thermal furnaces [RF patent No. 2109836, IPC С22С 33 \ 04, publ. 04/27/1998] and steel production [RF patent No. 225371, СВВ 3/04, СВВ 13/00, publ. January 27, 2005].

However, ferroalloys and, in particular, ferrosilicon are in relatively high demand, for which sufficient amounts of silica and iron oxides are contained in the sludge from alumina production.

The method is implemented under conditions of smelting in ore-thermal furnaces with a capacity of 25-63 MV · A as follows.

In the work used sludge from alumina production of the following chemical composition, wt.%: Fe ₂ O ₃ 45.1; Al ₂ O ₃ 13.3; SiO ₂ 10.1; CaO 9.3; TiO ₂ 4.6; Na ₂ O 3.6; CaO 11.0; MgO 1.1; P ₂ O ₅ 0.7.

The mixture is loaded into the furnace. The charge consumption is controlled through funnels around the electrodes, and its composition in order to avoid obtaining a non-standard silicon alloy is periodically controlled by the addition of a charge with a high content of sludge from alumina production. The melt is discharged from the furnace into the ladle with an energetic jet 2-4 times per shift. The melt temperature is 1400 ° C. The obtained melting products were investigated by chemical and x-ray phase analysis methods.

Example 1

The composition of the charge:

sludge from alumina production - 80.51%;

carbon reducing agent - 13.55%;

quartzite - 5.94%.

Received low quality ferrosilicon. The content of alumina production in the sludge mixture in an amount of more than 80% leads to contamination of the final product with impurities contained in the sludge, and leads the process towards the formation of cast iron.

Example 2

The composition of the charge:

sludge from alumina production 53%;

carbon reducing agent 18.81%;

quartzite 28.19%.

Received ferrosilicon grade FS-45 (GOST 1415-93 - Ferrosilicon).

Example 3

The composition of the charge:

sludge from alumina production 48.08%;

carbon reducing agent 19.59%;

quartzite 32.33%.

Received ferrosilicon grade FS-50.

Example 4

The composition of the charge:

sludge from alumina production 33.51%;

carbon reducing agent 22.30%;

quartzite 44.20%.

Received ferrosilicon grade FS-65.

Example 5

The composition of the charge:

Alumina production sludge 25%;

carbon reducing agent 24%;

quartzite 51%.

Received ferrosilicon grade FS-75.

Example 6

The composition of the charge:

sludge from alumina production 11.28%;

carbon reducing agent 26.44%;

quartzite 62.28%.

Received low quality ferrosilicon. The content of quartzite in the amount of more than 52% leads to sintering of the charge, which in turn reduces the gas permeability of the charge layer, so-called "fistulas" are formed, losses of silicon with gaseous silicon monoxide increase, and the extraction of the final product decreases.

The use of alumina production sludge as part of the charge reduces the escape of silicon monoxide from the reaction zone and improves the course of the smelting process in an ore-thermal furnace.

It was experimentally found that with a different ratio of the components of the charge it will not be possible to obtain ferrosilicon of the required quality. Based on stoichiometric calculations, the flow rate of the loaded materials into the charge is determined by the composition of the melted ferrosilicon.

If the content of the carbonaceous reducing agent in the composition of the charge is less than 13%, then due to a lack of carbon during the heating of the charge gaseous silicon monoxide will form, which, flying out of the furnace with gas, will reduce the yield of the target product. If the carbon reducing agent is more than 24%, then with a regular excess of the reducing agent, it accumulates in the furnace bath with the formation of a large amount of carborundum. In essence, when using the charge of the proposed composition, the amount of carbon reducing agent is higher than that required for the reduction of silicon from silica and quartzite. Excess carbon is consumed in reducing iron from sludge from alumina production. If the content of silicon and iron oxides in the sludge of alumina production is more than 75%, then the amount of slag in the furnace bath increases, and the loss of silicon in the form of silicon oxide also increases.

The proposed method in comparison with the prototype allows you to get the following advantages: reduce energy consumption, process alumina slimes most efficiently and rationally to produce a product more valuable to industry - ferrosilicon of various grades of alumina-containing slag, which can be used to produce alumina and high-alumina cement.

Claims (1)

A method of processing sludge from alumina production, including loading into the furnace a mixture containing sludge from alumina production and a carbon reducing agent, reducing smelting to obtain ferrosilicon and alumina-containing slag, characterized in that the reducing smelting is carried out in an ore-thermal furnace, the sludge from alumina production is introduced into the charge in an amount of 10 up to 81 wt.% of the total mass of silicon oxides in the mixture, while the mixture additionally contains quartzite in the following ratio of components, wt.%:
sludge from alumina production 25-53 carbon reducing agent 13-24 quartzite 26-52