GB2154223A

GB2154223A - Method of hot briquetting fine-grained substances and of further treating the hot briquettes

Info

Publication number: GB2154223A
Application number: GB08430435A
Authority: GB
Inventors: Armand Wagner; Franz Beckmann
Original assignee: Laborlux SA
Current assignee: Laborlux SA
Priority date: 1983-12-06
Filing date: 1984-12-03
Publication date: 1985-09-04
Also published as: LU85116A1; ZA849083B; DE3440037A1; GB8430435D0; FR2561257A1; GB2154223B; BE901093A; FR2561257B1; NO844859L

Abstract

Fine-grained substances in the form of metal oxides charged with solid and/or fluid carbon carriers are heated in the flue stream, alone or mixed with additional non-caking solid carbon carriers, to about 600 DEG C and are then mixed with caking coal previously heated to a maximum of 360 DEG C. The mixture is detarred and briquetted at 500 DEG C +/- 40 DEG c and the briquettes are subsequently conveyed to pyrometallurgical reduction processes in order to obtain the metals contained in the briquettes.

Description

SPECIFICATION Method of hot briquetting fine-grained substances and of further treating the hot briquettes This invention relates to a method of hot briquetting fine-grained substances with caking coal as a binder and of further treating the hot briquettes.

It is known from the "ancit" method to mix at least two finely ground coal components, of which one is a non-caking component with only a few volatile constituents and the other component is a caking coal, approximately at the softening temperature of the caking coal component, and to briquette the mixture hot (cf. "Stahl und Eisen" [Steel and Iron] 92 (1972), Vol. 21, pp. 1039 to 1044).

In the iron and steel industry a number of residual substances or wastes occur which consist of metal oxides charged with solid and/or fluid carbon-containing materials or carbon carriers.

Thus, the rolling scale which occurs in rolling mills is contaminated with oil, and in particular the rolling scale present in fine fractions contains quite a high concentration of oil. In order to be able to smelt rolling scale, a sintering process must be provided. Since oils and their cracking products cause problems in electrostatic filters, it is not advisable to subject rolling scale to sintering without first having burnt off the oil. Since the plant required for burning off is expensive and demands a large amount of maintenance, however, rolling scale is generally dumped, both the oxide and the fuel remaining unused. These dumped substances represent a considerable environmental problem. It would also be possible for the oil to be separated from the rolling scale by washing out by means of organic solvents, but this method too is very expensive and is not economic.

Other substances to which the present invention is applicable are the iron, zinc, and lead oxide-containing sludges and powders which occur during the cleaning of the blast furnace gases and which contain finely-distributed solid carbon carriers.

These so-called throat sludges must, if wet-chemical separation are to be avoided, as a rule be dewatered with filters, and the filters get blocked very quickly. As a result of these problems these sludges are likewise generally dumped on tips. A similar drawback occurs in the case of the powders, in which the zinc and lead oxide content is not sufficient to justify smelting. In this way the sometimes quite high combustion content of the sludges and powders is likewise lost.

The high manganese- and carbon-containing powders occuring in the production of ferromanganese both in blast furnaces and in electric furnaces are at present likewise generally dumped on tips, since they cannot be further used for the production of ferromanganese on account of their fine grain size.

The disposal of all these above-mentioned substances, for example on dumps leads to environmental problems which, in the case of heavy metals for example, are extremely serious and injurious to health.

The object of the invention is to provide a method of rendering the substances described above suitable for metallurgical processes without the fuels contained in the substances having to be separated beforehand. The object of the invention is furthermore to protect the environment from the disposal of these health-endangering substances.

The invention provides a method which comprises hot briquetting fine-grained substances with caking coal as a binder and of further treating the hot briquettes, characterized in that fine-grained substances in the form of metal oxides charged with solid and/or fluid carbon carriers are heated in the flue stream, alone or mixed with additional non-caking solid carbon carriers, to about 600"C and are mixed with the caking coal, previously heated to a maximum of 360 C, and the mixture is detarred and briquetted at 500"C + 40 C and the briquettes are conveyed to a pyro metallurgical reduction process in order to obtain the metal contained in the briquettes.

Thus the invention provides a method of recovering metal from metal oxide waste contaminated with solid and/or fluid carbon-containing material.

Preferably the proportion of the fine-grained metal oxides, charged with solid and/or fluid carbon carriers, in the hot briquettes amounts to between 20 and 80% by weight, preferably between 25 and 60% be weight.

The entire carbon content in the finished briquettes preferably amounts to between 30 and 70% by weight (in the dry substance).

After the briquetting the hot briquettes may be held for at least 30 minutes in the range of the pressing temperature in order to remove the residual tar content.

By the use of the metal oxides chargaed with carbon carriers for hot briquetting, the fluid carbon carriers are largely burnt away and thus used as heat carriers, while the solid carbon carriers are by and large not burnt away, but are briquetted. After the hot briquetting the briquettes are in a form which can be used in various pyrometallurgical reduction processes. They can be used for example in blast furnaces or electric furnaces in addition to the conventional charging substances, such as coke and graded ores for example. The metal oxides are reduced in these furnaces, using the carbon content of the briquettes including the carbon from the wastes used.The excess carbon which is present in the briquettes and is not required for the reduction of the metal oxides contained in the briquettes is additionally available as a reduction agent and thus diminishes the otherwise necessary coke requirement.

Depending upon the nature of the wastes used or of the metal oxides contained therein the hot briquettes are used according to the invention to obtain the appropriate metal.

The metal oxides charged as fine-grained substances with solid and/or fluid carbon carriers may consist of rolling scale, which occurs in rolling mills, mixed with oil contamination, and these metal oxides are reduced after the hot briquettng in order to obtain iron.

Alternatively the metal oxides charged as finegrained substances with solid and/or fluid carbon carriers consist of zinc- and lead-oxide-containing sludges and/or powders which occur during the purification of blast furnace gases, and these metal oxides are reduced after the hot briquetting in order to obtain zinc and lead.

Alternatively the metal oxides charged as finegrained substances with solid and/or fluid carbon carriers consist of manganese powders occurring in the production of ferromaganese, and the metal oxides are reduced after the hot briquetting in order to obtain ferromanganese.

If the substances to be added according to the invention are not in a pourable state, it is recommended, before delivery to the flue stream reactor of the hot briquetting stage, to pre-dry the substances and thus to make them pourable. Depending upon the degree of moisture, they can also be mixed with appropriate dry substances in quantity ratios such that the desired degree of pourability is achieved. Thus, for example, the very wet sludges from blast furnace washers can be mixed with the dry powders produced from the blast furnace gas dry purification filters until the desired condition is achieved.

Thus, fine-grained substances with a substantial water content, in particular sludges, are previously dried before being charged into the flue stream reactor of the hot briquetting stage, or are mixed with other fine-grained, dry charging substances, and are thus made pourable.

Claims

1. A method of hot briquetting fine-grained substances with caking coal as a binder and of further treating the hot briquettes, characterized in that fine-grained substances in the form of metal oxides chargaed with solid and/or fluid carbon carriers are heated in a flue stream, along or mixed with additional non-caking solid carbon carriers, to about 600"C and are mixed with the caking coal, previously heated to a maximum of 360"C, and the mixture is detarred and briquetted at 5000C ~ 40"C and the briquettes are conveyed to pyrometallurgical reduction processes in order to obtain the metals contained in the briquettes.

2. A method of recovering metal from metal oxide waste contaminated with solid and/or fluid carbon-containing material, characterized in that fine-grained material in the form of sad contaminated metal oxide is heated, in a flue stream, alone or mixed with additional non-caking solid carboncontaining material, to about 600"C and is mixed with caking coal, previously heated to a maximum of 360"C, as a binder, the mixture is detarred and briquetted at 500"C C 40 , and the briquettes are subjected to a pyrometallurgical reduction process in order to recover metal contained in the briquettes.

3. A method according to Claim 1 or 2, characterized in that the proportion of the fine-grained metal oxides, charged with solid and/or fluid carbon carriers, in the hot briquettes amounts to between 20 and 80% by weight, preferably between 25 and 60% by weight.

4. A method according to Claim 1, 2, or 3 characterized in that the entire carbon content in the finished briquettes amounts to between 30 and 70% by weight (in the dry substance).

5. A method according to any of Claims 1 to 4, characterized in that the metal oxides charged as fine-grained substances with solid and/or fluid carbon carriers consist of rolling scale, which occurs in rolling mills, mixed with oil contamination, and these metal oxides are reduced after the hot briquetting in order to obtain iron.

6. A method according to any of Claims 1 to 4, characterized in that the metal oxides charged as fine-grained substances with solid and/or fluid carbon carriers consist of zinc- and lead-oxide-containing sludges and/or powders which occur during the purification of blast furnace gases, and these metal oxides are reduced after the hot briquetting in order to obtain zinc and lead.

7. A method according to any of Claims 1 to 4, characterized in that the metal oxides charged as fine-grained substances with solid and/or fluid carbon carriers consist of manganese powders occuring in the production of ferromanganese, and the metal oxides are reduced after the hot briquetting in order to obtain ferromanganese.

8. A method according to one of more of the preceding Claims, characterized in that the finegrained substances have a substantial water content, in particular sludge, and are previously dried before being charged into the flue stream reactor of the hot briquetting stage and are thus made pourable.

9. A method according to one or more of the preceding Claims, characterized in that the finegrained substances have a substantial water content, in particular sludges, and are mixed with other fine-grained, dry charging substances and are thus made pourable.

10. A method according to one or more of the preceding Claims, characterized in that after the briquetting the hot briquettes are held for at least 30 minutes in the range of the pressing temperature in order to remove the residual tar content.