GB2028787A

GB2028787A - Blast furnace operation

Info

Publication number: GB2028787A
Application number: GB7928529A
Authority: GB
Original assignee: Foseco International Ltd
Current assignee: Foseco International Ltd
Priority date: 1978-08-19
Filing date: 1979-08-16
Publication date: 1980-03-12
Also published as: GB2028787B

Abstract

In making iron in a blast furnace, the charge includes briquettes of particulate ilmenite bonded by alkali metal silicate and bentonite clay. The ilmenite is reduced in the furnace, titanium carbide is formed and this provides a wear-resistant layer to protect the hearth. The briquettes are made by mixing the ilmenite, the bentonite clay and water, compacting the mixture into briquettes and allowing them to harden.

Description

SPECIFICATION Blast furnace operation This invention concerns a method of making iron in a blast furnace, a product for use in the method and a method of making the product.

According to the present invention, in a method of making iron in a blast furnace, the materials charged to the furnace include briquettes of particulate ilmenite bonded by a binder comprising alkali metal silicate and bentonite clay.

In making iron in a blast furnace, the hearth, which may consist of graphite blocks, gradually becomes worn and consequently the hearth temperature may become undesirably high. Use of improved refractories and/or repair methods for the walls of the furnace means that deterioration of the hearth may necessitate a shut-down of the furnace before this is required for any other reason.

The use of the briquettes in the method of the invention means that the hearth can adequately survive a longer period of use. As the briquettes pass down through the furnace, the ilmenite (FeTiO3) is reduced and a wear-resistant layer of titanium carbide is formed on the top surface of the hearth.

The carbon in the titanium carbide is derived from carbon, e.g. in the form of coke in the charge. The layer of titanium carbide protects the hearth and opposes the tendency for the hearth temperature to rise. Indeed, depending on the application rate for the briquettes, and thus the thickness of the wearresistant layer, the hearth temperature can actually be reduced.

Satisfactory results are not obtainable by the addition of ilmenite by itself e.g. in the form of ilmenite sand and the briquettes used in accordance with the invention have good resistance to breakdown at high temperatures. The high temperature breakdown resistance of the briquettes enables to pass through in a suitable form the burden of matter in the furnace.

The briquettes themselves form a part of the invention. The particulate ilmenite in the briquettes is preferably in the form of ilmenite sand and, whilst this may be of any suitable particle size, it preferably has an AFS (American Foundrymen's Society) grain fineness of 81.

The alkali metal silicate is preferably a sodium silicate although other such silicates may be used.

Sodium silicates having a SiO2: Na2O ratio of from 1.6:1 to 3.3 : 1 are readily available commercially and in the invention the preferred ratio is from 2.0:1 to 1.

The bentonite clay may be a naturally occurring sodium montmorillonite, a naturally occurring calcium montmorillonite or a sodium montmorillonite made by treatment of a naturally occurring calcium montmorillonite with sodium ions.

The binder preferably contains less than about 20% by weight of bentonite clay, especially 12 to 18%, and preferably contains at least 80% by weight, especially 82 to 88%, of alkali metal silicate.

The optimum quantity of binder depends inter alia on the desired strength of the briquettes and the fineness of the particulate ilmenite and the amount is preferably 3 to 10% by weight of the particular ilmenite.

The briquettes may have a variety of shapes and sizes but briquettes having the following characteris tics are especially suitable: Shape - almond-like, with two curved oval faces Dimensions - 6.2 cm long, 4.3 cm wide and 3.0 cm thick Weight 100 to 125 grams.

According to the invention a method of making an ilmenite briquette comprises mixing together parti culate ilmenite and a binder system comprising alkali metal silicate, bentonite clay and water, com pacting the mixture to form a briquette and allowing the briquette to harden.

The alkali metal silicate is preferably used in the form of an aqueous solution. The alkali metal silicate and the bentonite clay may separately be mixed with the particulate ilmenite but it is preferred to premix the bentonite clay into an aqueous alkali metal silicate solution and to allow this mixture to stand for about 24 hours before mixing it into the particulate ilmenite.

The briquettes may be formed using conventional briquetting equipment. Once formed, the briquettes can be hardened by being left at ambient tempera tures: no heating is necessary. Usually the briquet tes will be sufficiently strong to be used after they have been left for about two hours. The rate of hardening can be varied by varying the amount of binder used and/or the proportions of the ingre dients of the binder.

The method of making the briquettes is advantageous in that it is easy and quick to perform and does not require special apparatus or any expensive ingredient. The advantages are important because, although suitable application ratesforthe briquettes in relation to the overall rate of charging the furance are small, the overall rate of charging large modern furnaces is high.

The invention is illustrated by the following ex ample.

A binder system was formed by mixing the following: Aqueous sodium slicate solution (SiO2: Na2O , 2:1; solids content, 48%) 83% by weight Bentonite clay (sodium montmorillonite) 17% by weight This mixture was allowed to stand for 24 hours and then mixed with ilmenite sand of AFS grain fineness 81 at a rate of 5% by weight of the ilmenite sand. This mixture was then briquetted using a double roll briquetting press at a pressure of 13.79 N/mm2(2000 p.s.i.).

The briquettes hardened on being left at ambient temperature and could withstand a 6.1 m drop one hour after forming.

The hardened briquettes were added to a blast furnace charge at a rate of 11Kg per tonne of charge and the addition resulted in protection of the hearth of the furnace.

Claims

1. A method of making iron in a blast furnace in which the material charged to the furnace include briquettes of particulate ilmenite bonded by a binder comprising alkali metal silicate and bentonite clay.

2. A method according to claim 1 in which the alkali metal silicate is a sodium silicate having a SiO2 : Na2O ratio of from 2.0:1 to 2.5:1.

3. A method according to claim 1 or claim 2 in which the binder contains 12to 18% by weight of bentonite clay.

4. A method according to any of claims 1 to 3 in which the binder is present in an amount of 3 to 10% by weight of the particulate ilmenite.

5. A method according to claim 1 substantially as described with reference to the example.

6. A briquette of particulate ilmenite bonded by a binder comprising alkali metal silicate and bentonite clay.

7. A briquette according to claim 6 in which the alkali metal silicate is sodium silicate having a SiO2: Na2O ratio of from 2.0:1 to 2.5:1.

8. A briquette according to claim 6 or claim 7 in which the binder contains 12 to 18% by weight of bentonite clay.

9. A briquette according to any of claims 6 to 8 in which the binder is present in an amount of 3 to 10% by weight of the particulate ilmenite.

10. A briquette according to claim 6 substantially as described with reference to the example.

11. A method of making a ilmenite briquette comprising mixing together particulate ilmenite and a binder system comprising alkali silicate and bentonite clay, compacting the mixture to form a briquette and allowing the briquette to harden.

12. A method according to claim 11 substantially as described with reference to the example.

13. An ilmenite briquette made by a method according to claim 11 or claim 12.