FI86409B - REDUCERING AV JAERNSILIKATSLAGG FOER FRAMSTAELLNING AV ELDFAST OCH KEMISKT BESTAENDIG FIBER OCH BOTTENMETALL. - Google Patents

Description

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REDUCTION OF IRON SILICATE SLAG FOR THE MANUFACTURE OF REFRACTORY AND CHEMICALLY RESISTANT FIBER AND BOTTOM METAL

This invention relates to a method of utilizing ferrous silicate slag to produce a fiber resistant to high temperatures and harsh chemical conditions as well as a base metal.

As such, metallurgical slags are not suitable for defibering. Known methods of utilizing slags to make fibers are based on mixing the slags with additives. The alloying elements change the physical properties of the slag melt to be suitable for defibering. In industrial manufacturing, blast furnace slags are used almost exclusively, which are melted in a dome furnace and defibered by a four-wheel spinner. The most commonly manufactured end products are building insulation.

The use of non-blast furnace slags has been very rare. For example, iron silicate slags, a by-product of copper and nickel production, have not been used as raw materials in the production of fibers, despite the many advantages offered by slags. The unique chemical composition of iron silicate * ·, '·· slag slags:: *: enables e.g. the production of fibers that can withstand exceptionally high temperatures and harsh chemical conditions. The failure to exploit these opportunities has been mainly due to fiber manufacturing. restrictions on the melting unit, the dome furnace. Coke used in cupola furnace smelting tends to *. to reduce the iron contained in the raw materials to metal, "" · which in turn interferes with the defibering. • The grain size of the raw materials • · 2 86409 is also required. The materials fed to the dome furnace must be in piece size

In recent years, the introduction of electric furnace smelting in fiber production has also changed the situation and made it possible to utilize new raw materials. The use of an electric oven is known e.g. from patent FI-72502.

The use of iron silicate slags in the production of fibers is known from patent application FI-845114, which discloses two methods of mixing slag to obtain a fibrous melt. In general, the aim of the doping is to change the properties of the slag by adding acidic slag components so that the melt becomes highly fibrous and the final product has the desired properties.

The starting point of the present invention is another. This invention is based on modifying the chemical composition of iron silicate slag to be suitable for defibering by removing iron oxide from the slag. Iron is present in the slag mainly in the divalent, oxygen-bound, form FeO.

Iron oxide - FeO is a basic component in slag that: prevents acidic slag components from forming continuous: network structures whose existence is necessary for the defibering of the melt. By removing iron oxide from the slag, the composition of the slag is changed '' in an acidic direction, whereby the concentrations of S1O2 and Al2O3 in the slag increase and the physical properties of the slag become more fibrous. The essential features of the invention are set out in the appended claims.

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The removal of iron oxide is carried out by taking advantage of the reduction effort of iron oxides which has also been found in dome furnace smelting. The iron oxide content of the slag is reduced by reducing iron in the slag, for example by means of fine coke or coal dust. The metal obtained as a reduction product separates from the slag and settles to the bottom of the melting furnace as a base metal. Precious metals contained in slag, such as copper, nickel and cobalt, are also enriched in the base metal. The FeO content of the slag and at the same time the amount of metal formed is controlled by the amount of reducing agent fed to the furnace. Exhaust gas containing CO and CO2 is also produced as a product of reduction reactions.

The reduction of iron silicate slag according to the invention is carried out in a suitable furnace unit, for example an electric furnace. Iron silicate slag can be fed to the furnace either solid or molten. The reducing agent, e.g. fine coke, can be fed into the molten slag, for example by injection through a lance or electrodes. In this case, the melt mixing necessary for the reduction reactions is also provided. Mixing is also needed to promote the separation of the resulting metal droplets. ' the slag. As a result of the reduction reactions, the melting: V point of the slag rises and the slag is removed from the furnace at an elevated temperature. Slag extraction for defibering::: arranged to be continuous. Instead, the metal is removed from the furnace through a counter hole designed for a discontinuous purpose.

In the process according to the invention, iron oxide is reduced from the iron silicate slag to such an extent that the basicity in which the slag melt is fibrous is obtained, mol-% · “·· (FeO + CaO + MgO) / (S1O2 + Al2O3) = 0.5-0.8. Thereafter, 4 86409 melt can be made into a fiber resistant to high temperatures and harsh chemical conditions using well-known fiberization methods.

According to the invention, the composition of the metal formed during the reduction of iron silicate slag depends essentially on the amount of reducing metal oxides contained in the slag. The Fe content of the base metal is usually more than 90%, the rest being e.g. precious metals such as copper, nickel and cobalt.

If for some reason it is desired, in the reduction step of the iron silicate slag according to the invention, alloying elements which have a positive effect on e.g. the properties of the final product can also be added to the slag.

The advantages of the method of utilizing the iron silicate slag according to the invention are e.g. the following: 1) two valuable end products are obtained from iron silicate slag: fiber and metal, 2) 100% of the slag itself (except for the reducing agent) is sufficient as a raw material, and • · · • 3) iron silicate slag can be fed into the reduced • ·: / ·· to the furnace as molten, so that the thermal energy contained in the slag can also be utilized.

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The method of utilizing iron silicate slag according to the invention is illustrated by the following example.

Example

As a by-product of nickel production, iron silicate slag is obtained, the typical chemical composition of which is: <· M · ii 5 86409

Fe 41.5%, Sic> 2 29.5%, CaO 1.5%, MgO 6.5% and Al2O3 4.1%.

When 75% of the iron contained in the slag is reduced according to the invention, a suitable slag with a composition of: Fe 17.6%, S1O2 51.0%, CaO

2.6%, MgO 11.1% and Al2O3 7.5%. All percentages are by weight. The molar alkalinity of the slag is 0.69. About 590 kg of fibrous slag mixture and about 325 kg of metal are produced per tonne of iron silicate slag consumed.

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Claims (3)

6 86409 PATENT CLAIM 1. A method of utilizing iron-silicate slag with a high iron content to produce a refractory as well as a chemically resistant fibrous material, wherein the iron-silicate. the iron oxide content of the slag is reduced by reducing the iron and precious metals in the slag, characterized in that the FeO content of the slag melt to be reduced and the amount of metal formed are controlled by the ^ + AlgO ^) is adjusted to 0.5-0.8, whereby the products are a fibrous slag melt and a metal melt in which, in addition to iron, at least copper, cobalt and nickel are present. 1. Sätt att utnyttja järnsilikatslagg med hög järnhalt vid framställning av eldfast och kemiskt fixtures fibermaterials of metal in the form of a picture; * in the case of a game of fineness or stinking, some of which may be reduced by a reduction, having the basic molar content (FeO + CaO + MgO) / (SiC fiberbar ". slaggsmälta och metallsmälta som utom järn innehäller ätmin- stone koppar, cobalt och nickel. li