Method for producing a raw material for the production of refractory ceramic products, a raw material produced according to the method and a raw material for producing refractory ceramic products

Abstract

The invention relates to a method for producing a raw material for the production of refractory ceramic products, a raw material produced by said method, and a raw material for producing refractory ceramic products.

Claims

1. Method for producing a raw material for the production of refractory ceramic products that comprises the following steps: provision of a raw material containing Cr(VI) that is present to at least 50% by weight in a particle size greater than 50 m; provision of ascorbic acid; provision of water; combining of the raw material containing Cr(VI) with the ascorbic acid and the water; mixing of the raw material containing Cr(VI) with the ascorbic acid and the water; drying of the raw material containing Cr(VI); wherein the method is carried out such that the particle size of the raw material containing Cr(VI) does not change or does not change significantly during the course of the method.

2. Method as claimed in claim 1, in which the raw material containing Cr(VI) is provided in the form of used refractory ceramic products.

3. Method as claimed in claim 1, in which the raw material containing Cr(VI) is provided with a content of Cr(VI) of at least 500 ppm.

4. Method as claimed in claim 1, in which after drying, the raw material containing Cr(VI) has a content of Cr(VI) of less than 500 ppm.

5. Method as claimed in claim 1, in which after drying, the raw material containing Cr(VI) is provided as a raw material for the production of refractory ceramic products.

Description

(1) Further features of the invention are derived from the claims, the figures, and the accompanying description of the figures.

(2) All of the features of the invention, individually or in combination, may be combined with one another as desired.

(3) An example of the invention is explained below.

(4) According to the example, a raw material containing Cr(VI), an aqueous ascorbic acid granulate, and an ascorbic acid granulate were provided for carrying out the method according to the invention.

(5) The raw material containing Cr(VI) provided was in the form of used, crushed chromium corundum bricks. The raw material containing Cr(VI) was composed of about 78.8% by weight of aluminum oxide and 19.8% by weight of chromium oxide, with the remainder being composed of further oxides, more particularly ZrO.sub.2, Na.sub.2O, SiO.sub.2 and MgO. The total content of Cr(VI) in the raw material containing Cr(VI) was about 4.000 ppm. The corresponding raw material containing Cr(VI) for carrying out the method according to the invention was present as bulk material, wherein about 97% by weight was present in a particle size greater than 50 m. The particle size distribution curve of the raw material is given in the FIGURE.

(6) The ascorbic acid provided for carrying out the method according to the invention was present on the one hand as a granulate and on the other in the form of an aqueous solution. The ascorbic acid granulate was composed of granules of a particle size in the range of 2 to 3 mm. The aqueous ascorbic acid granulate was in the form of a 15% aqueous solution. The weight ratio of the ascorbic acid granulate to the aqueous ascorbic acid granulate was about 1:0.3. The total weight of ascorbic acid in the granulate and in the aqueous solution was such that the ratio of the molar weight of the ascorbic acid provided for carrying out the method according to the invention to the molar weight of the Cr(VI) in the raw material containing Cr(VI) provided for carrying out the method according to the invention was about 1.5.

(7) At the same time, this resulted in a weight percentage of water in the aqueous ascorbic acid granulate of 5.7% by weight relative to the total weight of the raw material containing Cr(VI) provided for carrying out the method according to the invention.

(8) The water provided for carrying out the method according to the invention was present exclusively as a component of the aqueous ascorbic acid granulate.

(9) In order to combine and mix the raw material containing Cr(VI) with the ascorbic acid granules and the aqueous ascorbic acid granulate, these components were fed into a drum mixer, and by starting said drum mixer, combined and mixed with one another therein. The mixing time in the drum mixer was 15 minutes.

(10) The raw material containing Cr(VI), after mixing in the drum mixer with the ascorbic acid granules and the aqueous ascorbic acid granulate, was fed into a drum dryer and dried therein at a temperature of 150 C. for a duration of about 1.5 hours.

(11) After mixing and before drying, the moisture content of the raw material containing Cr(VI) was about 5.7% by weight relative to the total weight of the raw material containing Cr(VI).

(12) After drying in the drum dryer, the residual moisture content of the raw material containing Cr(VI) was about 0.1% by weight relative to the total weight of the treated raw material containing Cr(VI).

(13) During mixing of the raw material containing Cr(VI) with the ascorbic acid, the content of Cr(VI) in the raw material containing Cr(VI) was substantially reduced by the ascorbic acid. In total, the content of Cr(VI) in the raw material containing Cr(VI) could be reduced from an initial content of 4,000 ppm to about 300 ppm in the treated raw material containing Cr(VI).

(14) The particle size of the raw material containing Cr(VI) provided for carrying out the method was essentially unchanged to a significant degree during the course of the method. The particle size distribution curve of the raw material containing Cr(VI) treated by the method according to the example therefore corresponded to the particle size distribution curve of the raw material originally provided for carrying out the method.

(15) The chemical composition of the raw material containing Cr(VI) treated by the method according to the example corresponded to the chemical composition of the raw material containing Cr(VI) originally provided for the method according to the example.

(16) The raw material containing Cr(VI) treated by the method according to the example was provided as a raw material for the production of refractory ceramic products.