CS267151B1 - A method of reducing the liquid slag from the production of the refining ferochrome - Google Patents

Abstract

The solution concerns the problem of increasing the utilization of chromium in the production of refined ferrochrome in an electric furnace by reducing its losses in the tailings slag by approximately one half by performing additional reduction outside the furnace with a minimum threefold excess of the reducing agent - silicochrome, resulting in tailings slag with a content of up to 2% by weight of chromium oxide and an intermediate silicochrome with a chromium content of over 30% by weight. If necessary, slag-forming additives, in particular lime and raw materials containing aluminum or its compounds, can be used to adjust the properties of the tailings slag during the additional reduction process.

Description

2 EN 267 151 B1

BACKGROUND OF THE INVENTION The present invention relates to a reduction in the chromium content of the wreckage debris generated by the production of a ferrochromising ferrochrome in an electric furnace in order to make it more useful.

In the prior art processes for the production of this ferro-chrome in an electric furnace, a waste slag with a content of about 4% by weight is produced. chromium oxide, with its high shorter! significant 20 to 25% chromium loss, one half of which is attributable to chromium present in slag in oxide form. For the production of ferochrome with a carbon content of up to 0.04% by weight. are used! known one- or two-stage in-process procedures. The principle is that a special slag with a chromium oxide content of 25 to 30% by weight is known to be melted in an electric furnace, also known as a red-calcium mixture, which is ultimately reduced by silico-chromium in one or two stages known as Perren wherein in the second stage the slag from the first stage comprises at least 14 to 15 wt. chromium oxide. In the case of out-of-office procedures, I get it! better results in the use of chromium by about 5%, but mainly higher utilization of silicon. According to the Author's Certificate No. 197 396, low-carbon ferro-chromium is obtained by repeatedly refining the silicochrome with a hollow slag from a production refinery ferochrome containing 5 to 15% by weight. chromium oxide.

The drawbacks of these processes are the low use of chromium when more than 2 wt. chromium oxide.

The problem has been solved and the disadvantage of the prior art has been eliminated by reducting the slag using a high, at least three times excess of silicochrome over stoichiometric consumption until the chromium oxide content in the wreckage is below 2% by weight, yielding a silicochrome intermediate with a chromium content of over 30% wt. In order to adjust the physical properties and chemical composition of the hull, it is possible to add up to 20% of the wax-forming additives, especially lime and aluminum-containing raw materials or its compounds.

Compared to previously known processes, the process is simple, less demanding to control the quality of the refining result, whereby the materials obtained - chromium-depleted slag and chromium-enriched silicochrome - have a more suitable chemical composition for further use. Slag containing chromium oxide up to 2% by weight it disintegrates more quickly, which improves its further processing and becomes suitable as calcium fertilizer in agriculture. Silicochrome with chromium content over 30% by weight which is used as a reducing agent in the production of refining ferochrome, increases production efficiency. Example 1

In the production of ferochrome containing up to 0.1% carbon in an electric arc furnace, a liquid heap slag containing 8% chromium oxide, 42.5% calcium oxide, 23.2% silica, 1.8% iron oxide, is produced. a residue of up to 100 wt. magnesium and aluminum oxide. The slag was reduced in a reaction vessel outside the furnace with a silicochrome containing 26% by weight. chromium. The following table shows an overview of the results achieved.

Table 1 Spotřebakg

Aluminum slag SiCr 1 5 000 1 360 2 5 000 1 100 3 3 900 2 300 4 4 500 1 700 5 4 500 1 750 6 4 500 1 600 15 Lime Excess SiCrecial sp. .7 before doreduction - 7.9 times 6.1 1.1 - 4.9 times 6.4 2.0 - 9.3 times 9.8 0.6 - 7.8 times 7.8 0.2 100 8.6 times 8.1 0.6 200 5.7 times 8.4 0.3

Claims (2)

OBJECT OF THE INVENTION A process for the redox reduction of liquid slag from the production of refining ferrochrome, by out-of-furnace casting with silico-chromium, characterized in that the slag is cast with at least a threefold excess of the stoichiometric need for silico-chromium until the chromium oxide content falls below 2% by weight. 2. The process according to item 1, characterized in that up to 20% by weight of liquid slag is added to the liquid slag. slag-forming additives such as lime and aluminum or its compounds.