Use of grinding swarfs of conglomerated stone production as an ingredient of clay raw material for brickware, earthenware and similar ceramic products

Technical field

The present invention relates to use of grinding swarfs of conglomerated stone production as an ingredient of clay raw material for brickware, earthenware and similar ceramic products, which are processed during their manufacturing by temperatures exceeding 900 ⁰ C.

Background Art

In the manufacturing process of the conglomerated stone commonly called as artificial stone, grinding swarfs develop during its grinding and polishing in the presence of water. The swarfs may contain 30 to 50 percent by weight of water, 75 to 85 percent by weight of silicon dioxide, 6 to 10 percent by weight of organic matter and 2 to 5 percent by weight of metal salt. The organic matter contained in the swarf is typically represented by residues of polymerized resin that is used as a binding agent for all substrate components employed for conglomerated stone manufacturing. The content of heavy metal is low and does not exceed the natural background that results from prevailing use of natural resources for conglomerated stone manufacturing, which level does not go beyond 30 mg.kg ^"1 .

Suspended solid particles are separated from the grinding swarfs for instance by decantation followed by filtration on a sludge press or other filtering device. The condensed grinding swarfs are laid down on a common disposal site as so called common waste. Important costs and legislation problems concerning waste production and its handling arise in connection with such an approach, however.

Disclosure of Invention

The object of the present invention is to find out a solution to stop wasteful treatment of grinding swarfs and to exploit their positive physical and chemical features for their secondary processing while respecting environmental issues regarding the waste treatment, whereby this specific goal is achieved by the use of grinding swarfs of conglomerated stone production as an ingredient of clay raw material for brickware, earthenware and similar ceramic products, which are processed during their manufacturing by temperatures exceeding 900 ⁰ C.

The use of grinding swarfs of conglomerated stone production as an ingredient of clay raw material for brickware, earthenware and similar ceramic products is particularly advantageous in the case where natural plastic raw clays, representing the basic raw material, do not contain the necessary content of siliceous chemicals, especially of silicon dioxide required to obtain quality final products. The use of grinding swarfs represents an issue for achieving an optimum composition of the mentioned basic raw material, especially for eliminating the effects of the lack of the mentioned silicon dioxide etc. The organic matter that are contained in grinding swarfs burn completely during the processing of the brickware, earthenware and other clay raw material and due to its calorific capacity influences positively the calorific balance of the baking process.

Best Mode for Carrying out the Invention

The ceramic products are manufactured by mixing suitable plastic clays with water completed by their shaping, drying, and baking. The plastic clays represent not solidified sedimentary rock constituted by a mixture of hydrated aluminic siliceous minerals whose structure is able to absorb a large amount of molecularly bound water.

The choice of natural raw material and the following manufacturing process are deciding for quality and properties ceramic products. If, for instance, the plastic clay based brick-clay that is the basic raw material for brickware, contains a lower proportion of silicon dioxide and other

silicon modifications, this lack is eliminated by addition of silicon dioxide either in the form, for instance, of native amorphous silicates or natrium silicate or similar that ensure a sufficient viscosity of the brickware raw material and, possibly, even easier transformation of heavy metal oxides into insoluble silicates during the baking process by temperatures exceeding 900 ⁰ C.

Apart from these additives, other different ingredients are added nowadays to the basic raw material when manufacturing brickware and similar products as for instance electrolytic-bath sludge, fly ash, wood sawdust, waste wood pulp and the like that, in certain measure, improve the final structure of the ceramic product and of which some, otherwise harmful as mentioned above, are subsequently sufficiently incinerated during the baking process.

Example 1

The grinding swarfs are put into the mixing device for basic plastic clay-based raw material preparation for ceramic products, for instance in the following proportion:

1000 parts by weight of plastic clay-based raw material with water

30 to 60 parts by weight of grinding swarfs corresponding to the degree of their density.

After the homogenization, the basic raw material with addition of the grinding swarfs and other components is processed with usual pressing, cutting and shaping to obtain desired forms. Other processing steps as raw product drying and its baking follow in a usual way, it means after drying follows one baking step at least by temperatures of 900 ⁰ C to 1 500 ⁰ C, without any negative impact of the grinding swarfs on these processes, except that they take partly part, together with other usual ingredients, as wood sawdust, in the calorific balance of the baking process and the subsequent product porosity and the like.

The grinding swarfs may possibly contain even some polymerized residues of the material substrate for artificial stone manufacturing that were scraped down from the walls of the manufacturing equipment during preventive maintenance.