AU2014280959B2

AU2014280959B2 - Process For The Complex Processing Of Bauxite

Info

Publication number: AU2014280959B2
Application number: AU2014280959A
Authority: AU
Inventors: Alexander Welter
Original assignee: PLEASON VENTURES Ltd
Current assignee: PLEASON VENTURES Ltd
Priority date: 2014-12-24
Filing date: 2014-12-24
Publication date: 2020-10-22
Anticipated expiration: 2034-12-24
Also published as: AU2014280959A1

Abstract

The process for complex processing of bauxite relates to the metallurgy of non ferrous metals, especially the field of producing alumina from bauxites, and is 5 particularly effective when processing siderite-containing bauxites. The industrial result when processing bauxite is the production of alumina and a metallurgical iron ore concentrate as well as a conditioned iron ore concentrate. The hydrochemical process extracts iron compounds from the bauxite to form an iron-ore concentrate that is suitable for the production of steel, wherein the 10 bauxite is completely desideritised and then further processed into alumina using known processes. The separation of the iron compounds at the beginning of the process and the desideritisation of the bauxite ensure an increased efficiency for the production of alumina. 1/2 bauxite milling and Fe extraction Bayer enriched flrto ftepl Process bauxite (solid flrto ftepl phase) solution of the iron chelate (liquid phase) NaHCO sodumhyroenNeutralisation at pH 7 - 8 NaC0 carboaluminate (solid filtration of the pulp calcination solution of the iron chelate (liquid phase) nre-extraction of iron at pH 12 F . Fe(OH)3-iron ore filtration of the pulp -Wconcentrate (solid (: phase) mother liquor of the Chelate (liquid phase) concentration by evaporation cooling CO2 ,, carbonation Filtration of the sodium hydrogen PEIP -- c a rbonate (solid phase) circulation soln. of the sintering chelate (liquid phase) Fig. 1

Description

1/2 bauxite

milling and Fe extraction

Bayer enriched flrto flrto ftepl ftepl Process bauxite (solid phase)

solution of the iron

phase) (liquid chelate at pH 7 - 8 NaC0 sodumhyroenNeutralisation carboaluminate (solid

pulp filtration of the NaHCO

solution of the iron calcination

chelate (liquid phase) nre-extraction of iron at pH 12

F. filtration of the pulp Fe(OH)3-iron ore -Wconcentrate (solid

(: phase)

mother liquor of the

(liquid phase) Chelate

concentration by evaporation

cooling

CO2 ,, carbonation

Filtration of the sodium hydrogen PEIP -- c arbonate (solid phase)

circulation soln. of the sintering chelate (liquid phase)

Fig. 1

Process for the complex processing of bauxite

The present invention relates to the metallurgy of non-ferrous metals, especially the field of the production of alumina from bauxites. The process is particularly effective for the processing of siderite-containing bauxites.

The principal components of bauxite are aluminium and iron compounds. In the production of alumina from bauxites the maximum possible fraction of aluminium oxide is recovered, whereas all iron compounds are stockpiled, wherein up to a million tons per year of iron oxide can accumulate in some alumina production units. The separation of the iron compounds in the production of alumina leads not only to an improvement in the process parameters of the working steps for concentrating and washing red mud or for sintering the mud batch, but also has a positive environmental influence by extending the lifetime of the mud fields.

Processes are known for separating iron both from bauxite and from red mud. In the Pedersen Process a mixture of bauxite and calcium oxide is melted in an electric arc furnace at a temperature of 1500 °C to afford pig iron and aluminium-calcium slag that is further processed hydrometallurgically to produce alumina (see Ni L.P., Gol'dman M.M., Solenko T.V. Pererabotka vysokozelezistych boksitov - Metallurgija, M., 1979, S. 203).

The modified sequential variant of the Bayer Process is also known, i.e. sintering with the intermediate step of iron separation by melting red mud in the presence of a reducing agent at a temperature of 1250 - 1300 °C according to the Krupp-Renn Process with magnetic separation of iron, sintering the slag with limestone and soda at 1200 °C, leaching the sinter cake in order to obtain the sodium aluminate solution and use of the mud to produce cement (ibid., p 205).

The process of magnetising calcination of siderite-containing bauxite is known for the purpose of siderite decomposition and the conversion of the iron compounds into magnetic compounds with their subsequent recovery by means of magnetic separation (ibid., p 215).

The above processes for the separation of iron from both bauxite and red mud requires the pyrometallurgical steps of calcination and melting, thereby necessitating an increase in constructional capital costs and in running costs for energy sources and the reducing agent. The pyrometallurgical process steps are linked with considerable environmentally harmful emissions.

The closest solution in regard to the claimed invention is a process for the extraction of aluminium and iron from aluminium-containing ores (see US Patent no 2155919, cl. C22B 3/10, C225 3/22, C22B 21/00, C22B 3/38, C22B 3/00, published 24.02.2010). Processes for the extraction of aluminium and iron ions from alumina-containing ores are described in this patent document. The ore extraction process consists in the leaching of the roasted ore with the use of acid to produce the leachate and a solid precipitate. The leachate comprises aluminium and iron ions in solution. The process for recovering the aluminium ions from a mixture that comprises the iron and aluminium ions consists in the recovery of the aluminium ions from a mixture that comprises iron and aluminium ions, an organic solvent and an extractant that is capable of producing an organometallic complex essentially selectively with the cited iron or aluminium ions, which are soluble in said solvent.

The disadvantage of this process consists in the need for the ore roasting and in the difficulty of recovering the acid in the course of the leaching, all of which requiring an increased energy outlay and being very environmentally harmful.

Disclosed herein are processes which may have increased efficiency for bauxite processing, and/or including the processing of siderite-containing bauxites for the production of alumina and/or for commercial iron ore concentrate.

In one aspect there is provided a process for processing bauxite, said process comprising the following steps: (a) grinding bauxite using a circulating chelate solution to form a suspension; (b) heating the suspension to form a mixture comprising an iron chelate and an aluminium chelate; (c) separating the mixture into a solid phase and a liquid phase; (d) processing the solid phase to form alumina; (e) treating the liquid phase with a circulating sodium hydrogen carbonate to adjust the pH of the liquid phase to from 7 - 8 to form a sodium hydrogen carboaluminate precipitate; (f) separating the sodium hydrogen carboaluminate precipitate from the liquid phase to form a sodium hydrogen carboaluminate depleted liquid phase; (g) adjusting the pH of the sodium hydrogen carboaluminate depleted liquid phase to more than 12 to form an iron hydroxide precipitate; (h) separating the iron hydroxide precipitate from the sodium hydrogen carboaluminate depleted liquid phase to form an iron hydroxide depleted liquid phase; (i) concentrating the iron hydroxide depleted liquid phase by evaporation to form a concentrate; (j) cooling the concentrate to form a cooled concentrate; (k) treating the cooled concentrate with pressurised gaseous carbon dioxide to form a sodium hydrogen carbonate precipitate; and (1) separating the sodium hydrogen carbonate precipitate from the cooled concentrate to form the circulating sodium hydrogen carbonate used in step (e) and the circulating chelate solution used in step (a).

The industrial result is the separation of iron compounds in the form of a commercial product to the first step of the bauxite processing to alumina according to the Bayer process or according to the Bayer sintering process.

Disclosed herein are two variants:

3a Variant 1 The basic process scheme is illustrated in Fig. 1. Bauxite is milled using a circulating solution of chelate, i.e. a mixture of the sodium salt of ethylenediaminetetraacetic acid and a weak acid such as e.g. acetic acid. Warming the suspension then results in the iron separation of iron-containing compounds from bauxites with the formation of an iron chelate: Fe20 +2Na 2HAedta+2CH$COOH=2Na[Feedta]+2CH, 3COONa+3H2O [1]

FeCO 3 + Na 2H 2edta = Na[Fe edta] + H2 0+CO 2 [2]

In addition to the iron chelate, minor quantities of the aluminium chelate Na[AI edta] are also formed. After the iron separation, the suspension is separated into a solid phase, an enriched desideritised bauxite that is further processed by any known process to alumina, and into a liquid phase that is decomposed by a double change in the pH of the solution. The iron chelate is neutralised at pH 7 - 8 with circulating sodium hydrogen carbonate, wherein sodium hydrogen carboaluminiate precipitates and is removed from the solution.

Na[Aledta] + 4 NaHCO3 = NaA[CO3](OH) 2 t + Na4edta + 3C0 2 +H2 0 [3]

The renewed extraction of iron from the iron chelate occurs at a pH of the solution of up to 12 with the precipitation of iron hydroxide:

Na[Fe edta] + 3NaOH= Fe(OH) 31 + Na 4 edta [4]

Na 2[Fe edta] + 2NaOH= Fe(OH) 21 + Na4 edta [5]

The suspension is then separated, namely into iron hydroxide as the solid phase that represents the commercial product, and into a liquid phase, the mother liquor of the chelate. The mother liquor of the chelate is then concentrated by evaporation, cooled and carbonated with gaseous carbon dioxide under a pressure of at least 16 bar so as to crystallise out sodium hydrogen carbonate:

Na 4edta+ 2CO2 + 2H 20 -- Na2 H 2edta + 2NaHCO3s [6]

CH 3COONa + C02 + H2 0 = CH 3COOH + NaCHOs3 [7]

The suspension is then separated into a liquid phase, the circulating solution of chelate, and a solid phase, that represents the sodium hydrogen carbonate. The solid phase is separated into 2 streams, namely into a circulating stream for neutralisation and into a second stream that is led out and e.g. supplied to the sintering of the alumina batch.

The sodium hydrocarboaluminate is calcined at a temperature of 700 - 900 0C with the formation of sodium aluminate:

NaAI[CO 3 ](OH) 2 -- Na 20 A12 0 3 + C02T + H 20T [8]

The solid sodium aluminate is then fed to the production of alumina.

Variant 2 The basic process scheme is illustrated in Fig. 2. Bauxite is ground with the use of a circulating solution of chelate (sodium salt of ethylenediaminetetraacetic acid). Warming the suspension under carbonation with C02 under a pressure of at least 16 bar then results in the iron separation of iron-containing compounds from the bauxite with the formation of iron chelate:

Fe 2 0 3 + 2Na 2H 2edta + 2CO2 = 2Na[Fe edta] + 2NaHCO 3 + H 2 0 [9]

FeCO 3 + Na 2H 2edta = Na 2[Fe edta] + C02+ H 2 0 [10]

The chelate is decomposed and the renewed iron separation are carried out as in Variant 1.

After the renewed iron separation the suspension is separated, namely into iron hydroxide as the solid phase that represents the commercial product, and into a liquid phase, the mother liquor of the chelate. The mother liquor of the chelate is then concentrated by evaporation, cooled and carbonated with gaseous carbon dioxide under pressure so as to crystallise out sodium hydrogen carbonate:

Na 4edta+ 2CO2 + 2H 20 -- Na2 H 2edta + 2NaHCO3 [11]

The process continues as in Variant 1. The present process ensures the complex processing of bauxite with the production of metallurgical alumina and conditioned iron ore raw material.

Examples of use.

Example 1 A siderite-containing bauxite sample was used for the experiment. The chemical composition of the bauxite is shown in Table 1.

The bauxite sample was milled in a laboratory mill and treated with the solution of a mixture of the disodium salt of ethylenediaminetetraacetic acid at a concentration of 150 g/dm 3 and 70 g/dm 3 acetic acid for the iron separation.

Extraction conditions weight ratio liquid: solid in the initial suspension of the solution and the weight ratio liquid: solid of the bauxite solution is 14.5. Time 1 hour. Temperature 100 °C.

After the extraction the suspension was separated by filtration and the solid precipitate was washed. The solid precipitate represents the enriched C0 2 -free bauxite. The liquid phase, the solution of the iron chelate, was neutralised with sodium hydrogen carbonate to a pH of 7.5, whereupon the sodium hydrogen carboaluminate precipitated out. The precipitate was filtered off and washed. A caustic liquor was added to the neutralised solution of the iron chelate in order to increase the pH of the solution to 12. This caused the iron chelate to decompose and the iron-containing product precipitated out. The precipitate was filtered off and washed.

Decomposition conditions: Temperature 100 °C. Time 5 hours.

The hydrogen aluminocarbonate was calcined at a temperature of 750 °C for 30 minutes and afforded solid sodium aluminate.

The composition of the initial bauxite and the resulting products are presented in Table 1.

Example 2

A siderite-containing bauxite sample was used for the experiment. The chemical composition of the bauxite is shown in Table 2. The bauxite sample was milled in a laboratory mill and treated with the solution of the disodium salt of ethylenediaminetetraacetic acid at a concentration of 120 g/dm 3 for the iron separation.

Extraction conditions weight ratio liquid: solid in the initial suspension of the solution and the weight ratio liquid: solid of the bauxite solution is 14.5. Time 5 hours. Temperature 120 °C. C02 pressure 40 bar.

After the extraction the suspension was separated by filtration and the solid precipitate was washed. The solid precipitate represents the enriched C0 2-free

bauxite. The liquid phase, the solution of the iron chelate, was neutralised with sodium hydrogen carbonate to a pH of 7.5, whereupon the sodium hydrogen carboaluminate precipitated out. The precipitate was filtered off and washed. A caustic liquor was added to the neutralised solution of the iron chelate in order to increase the pH of the solution to 12. This caused the iron chelate to decompose and the iron-containing product precipitated out. The precipitate was filtered off and washed.

Decomposition conditions: Temperature 100 °C. Time 5 hours.

The hydrogen aluminocarbonate was calcined at a temperature of 750 °C for 30 minutes and afforded solid sodium aluminate. The composition of the initial bauxite and the resulting products are presented in Table 2.

Table 1 - Chemical composition of the initial bauxite and the processed products of Variant 1

Iron Chemical Initial Enriched Sodium Sodium Composition, bauxite bauxite containing hydrogen aluminate Product % carboaluminate

A12 0 3 40.1 51.0 0.3 35.8 58.3 Na 20 0.5 0.15 1.2 20.6 33.6 SiO 2 10.2 12.7 0.4 3.6 5.8 Fe 20 3 22.2 7.1 83.8 1.2 2.0 TiO 2 2.3 2.7 0.1 - CO 2 1.5 0.1

Table 2 - Chemical composition of the initial bauxite and the processed products of Variant 2

A1203 40.1 50.4 0.4 35.8 55.5 Na 20 0.5 0.3 0.8 20.8 32.2 SiO 2 10.2 12.5 0.4 6.7 10.0 Fe 20 3 22.2 7.1 82.6 1.2 1.7 TiO 2 2.3 2.7 0.3 - CO 2 1.5 0.1

Claims

1. A process for processing bauxite, said process comprising the following steps: (a) grinding bauxite using a circulating chelate solution to form a suspension; (b) heating the suspension to form a mixture comprising an iron chelate and an aluminium chelate; (c) separating the mixture into a solid phase and a liquid phase; (d) processing the solid phase to form alumina; (e) treating the liquid phase with a circulating sodium hydrogen carbonate to adjust the pH of the liquid phase to from 7 - 8 to form a sodium hydrogen carboaluminate precipitate; (f) separating the sodium hydrogen carboaluminate precipitate from the liquid phase to form a sodium hydrogen carboaluminate depleted liquid phase; (g) adjusting the pH of the sodium hydrogen carboaluminate depleted liquid phase to more than 12 to form an iron hydroxide precipitate; (h) separating the iron hydroxide precipitate from the sodium hydrogen carboaluminate depleted liquid phase to form an iron hydroxide depleted liquid phase; (i) concentrating the iron hydroxide depleted liquid phase by evaporation to form a concentrate;

() cooling the concentrate to form a cooled concentrate; (k) treating the cooled concentrate with pressurised gaseous carbon dioxide to form a sodium hydrogen carbonate precipitate; and (1) separating the sodium hydrogen carbonate precipitate from the cooled concentrate to form the circulating sodium hydrogen carbonate used in step (e) and the circulating chelate solution used in step (a).

2. Process according to claim 1, wherein the circulating chelate solution is a mixture of a sodium salt of ethylenediaminetetraacetic acid or of ethylenediaminetetraacetic acid and a weak acid.

3. Process according to claim 1, wherein the circulating chelate solution comprises a sodium salt of ethylenediaminetetraacetic acid, or ethylenediaminetetraacetic acid; and the suspension is heated under carbonisation with C02 under a pressure of at least 16 bar.

4. Process according to any one of claims I to 3, wherein the temperature of the heating in step (b) is 100 °C.

5. Process according to any one of claims 1 to 4, wherein the pH adjusting in step (g) is effected by metering in sodium hydroxide.

6. Process according to any one of claims I to 5, wherein a circulating seed crystal solution formed from the iron hydroxide precipitate separated in step (h) is used in step (g).

7. Process according to any one of claims 1 to 6, wherein the C02 pressure used in step (k) is at least 16 bar.

8. Process according to any one of claims I to 7, wherein the sodium hydrogen carboaluminate precipitate separated in step (f) is calcined at a temperature of 700 - 900 °C to form sodium aluminate that is processed in a Bayer process to form alumina.

Pleason Ventures Ltd Patent Attorneys for the Applicant/Nominated Person SPRUSON & FERGUSON