Technical field

The Invention belongs to the field of production of ceramic products, bricks and similar products, with the possibility of implementation in general, and refers to the production of ceramic tiles, thermal blocks, roof tiles, bricks, blocks, sanitary facilities, electrical insulating materials and similar clay products.

The Finding refers to the technological processes of shaping clay: extrusion, pressing and casting.

According to the International Classification of Patents (MKP) tags are:

C04B 33/36

C04B 33/13

C04B 33/131

C04B 2235/3201

C04B 2235/3427

C04B 2235/447

C04B 2235/6021

Finding a resolves:

1. Increasing energy efficiency during firing of the clay products, which can be technically achieved either by shortening the time of exposure to the peak temperature or by reducing (lowering) the firing temperature.

2. Increased mechanical hardness of the fired product

3. Reduced water-absorption of fired products

4. Reducing the efflorescence effect when firing (FIG 1, FIG 2)

5. The Possibility of firing clay with organic content up to 4% without

deformations on the product (FIG 3)

6. Complete substitution of other additives that help sintering Background Art

One of the biggest problems in the industry of brick and ceramic products is the uneven raw material composition of clay and a great consumption of energy when firing. Patents EP2660221, EP2660220, EP2660219 and W02006YU00020 20060802 explains the lowering of the firing temperature and improving the physical characteristics of fired clay products by using phosphoric acid and water glass to form three calcium phosphate and (poly) calcium silicates in clay.

This procedure, given the raw material composition of clay, is not always efficient and the final product of chemical reactions is not always predictable. This is due to the fact that phosphorous anion and silicate can be divided by the available amount of calcium, and it depends on whether calcium phosphate or calcium silicate will be dominant. Their Mutual relationship depends on the firing temperature, so the baking result is not predictable.

All the methods applied in the specified patents (EP2660221, EP2660220, EP2660219 and W02006YU00020 20060802) use the existing calcium from the clay, which is usually from calcium carbonate. Very often calcium carbonate in clay is not present at the point of adding phosphoric acid and thus it is not possible to accurately tell if and in what measure the desired chemical reactions are described. Unlike the aforementioned methods (EP2660221, EP2660220, EP2660219 and W02006YU00020 20060802), our invention controls completely desired chemical reactions, which leads to a much smaller mass of the additive in clay.

Disclosure of the Invention

The Essence of this finding is the addition of additives to clay, for the formation of the highest tricalcium phosphate, and possible calcium polyphosphates in the final (fired) products made of clay. The formation of calcium phosphosilicates has also been demonstrated.

The Finding is applicable in the production of ceramic tiles, bricks, building blocks, roof tiles and similar clay products. Using the above procedure, better mechanical characteristics of the product are obtained (increased hardness and reduced water consumption) and more efficient use of energy during baking. In this way, the shortening of the firing process drastically increases production.

The Invention represents addition mixture of calcium carbonate and mono calcium phosphate. This mixture (additive) is added to the clay in a mass percentage of 0.05% to 49% in relation to the dry matter of clay.

When making additives, the ingredients are mixed in a weight ratio: from 5% to 95% mono calcium phosphate and calcium carbonate (in an adequate percentage to 100%). This relationship is changed depending on the empirical results of the testing for clay on which it is applied as well as the chemical composition of mono calcium phosphate supplied on the market, because phosphate can react with other ingredients of the clay, and again excess carbonates, if it does not affect the desired chemical reactions. The Function of calcium carbonate other than the formation of three calcium phosphate with mono calcium phosphate is that the use of a part that is unused in the aforementioned chemical reactions is regulated by water-absorption in a fired product to a level given by the manufacturer's standards.

In Order to efficiently apply the mixture of mono calcium phosphate and calcium carbonate must be grinded to a particle size of 5 to 120 microns.

The Main chemical equation, which is based on the action of the additive, is the formation of tricalcium phosphate:

2CaC0 ₃ +Ca(H ₂ P0 ₄ )2 = Ca3(P0 ₄ )2+2C02+2H ₂ 0

Calcium carbonate and mono calcium phosphate at a temperature of over 650 ° C form Ca ₃ (P0 ₄ ) ₂ and calcium polyphosphates and other minerals such as calcium phosphosilicates (e.g. Berlinite).

The Common feature of these minerals is that they arise at lower temperatures than those common for firing ceramic products and improved mechanical hardness.

According to Mohs' scale, these minerals are close to the hardness of 6 which is characteristic of quartz.

Best Mode for Carrying Out of the Invention

Depending on the method of clay grinding, the addition of additives is carried out: 1. For dry (extrusion) additive is best added on the conveyer belt before the mills for better mixing with clay

2. For Wet grinding (Schlicker, Barbot), the additive can be added directly to water mills in the form of a powder or water suspension or in a grinded clay (Schlicker, Barbot) pool - good mixing required

Industrial Applicability

Sample 1 - Laboratory testing in ceramic tile production

The finding (additive) is made as a compound 54% mono calcium phosphate and 46% calcium carbonate. Both substances were pre-mixed and grinded to a particle size of 60 - 90 microns.

The standard factory mixture of atomized clay for floor tiles was used (so called sinter in the amount of 4 kg) divided into 4 equal groups of 1 kg. In four water laboratory mills was first added clay and water for grinding (62% dry matter + 38% water).

The first (control) mill was without additive, and in the remaining 3 the additive was added in concentrations (calculated by weight of the clay dry matter only): 0,15%, 0,30% and 0,50%. After grinding with an additive, the mills were emptied and the clay was dried to 5% moisture and dry grinded for pressing. Then the atomized clay was formed by pressing and fired in the factory kiln at a standard temperature of 1209 ° C. The results of the fired products are presented in the enclosed tables below - the standard parameters of quality control of the tiles are measured.

1) SINTER (FLOOR TILE) - WITHOUT ADDITIVE (1209°C)

2) SINTER (FLOOR TILE) - WITH ADDITIVE 0,15 % (1209°C)

3) SINTER (FLOOR TILE) - WITH ADDITIVE 0,30 % (1209°C) 4) SINTER (FLOOR TILE) - WITH ADDITIVE 0,50 % (1209°C)

The Analysis of the results showed a significant increase in the bending strength, i.e. reduction of water-absorption of the tiles with an additive concentration of 0,15% compared to the standard obtained tiles, which is particularly significant in the manufacture of floor tiles.

Sample 2 - Factory test of the shortened firing cycle in ceramic tile production

The Invention (additive) was made as a compound 54% mono calcium phosphate and 46% calcium carbonate. Both substances are pre-mixed and grinded to a size of 60 - 90 microns. Based on the prior laboratory tests, it was determined that 0,15% concentration of additive was suitable for the factory test, but due to the

exceptionally small concentrations of additives and the inability to accurately measure the clay during the industrial test, it was decided to increase the portion of the additive to 0,25%. So that in the water mills for every 10 1 of dry matter (mixture of more types of clay) was added a total of 25 kg of additive. After the milling and atomization, tiles were formed by pressing, drying and firing (floor tiles dimensions 33 x 33 cm).

The Standard firing cycle of floor tiles dimensions 33 x 33 cm was 59 minutes and during factory testing it was agreed to start with these parameters and then to gradually accelerate one or two minutes - up to 55 minutes. In The accompanying table are given the results of testing and the quality of regular production and test production tiles.

Analysis of results:

- The reduction of the firing cycle from 59 minutes to 55 minutes resulted in a savings of 10% of energy - The analysis of the size of the tiles showed that the firing cycle can be further accelerated (shortened) as the size of the tiles with an additive was 330 mm as opposed to the tiles from the regular production where it was 332 mm

- Fired biscuit of a standard composition is heavier than a biscuit from a composition with an additive

- The process of atomizing has been performed without difficulty

Sample 3-Laboratory test shortening of the firing cycle from 24 h to 21 h when producing extruded products (bricks)

The invention (additive) is made as a compound of 54% mono calcium phosphate and 46% calcium carbonate. Both substances are pre-mixed and grinded to a particle size of 60 - 100 microns. 50 kg of clay from Morocco was prepared in the laboratory. The content of calcium carbonate in the clay was over 10% by weight. The Clay was 1

divided into two parts by 25 kg each. The first part was without additive, and in the second part additive was added 0,25% by weight (to the 25 kg of clay 62,5 gr of additive). Additive was mixed with adequate water for extrusion process.

After mixing, the mixture was added and mixed with clay before extrusion and then such obtained samples were dried and fired. Clay samples without additives were fired on a standard firing curve of 24 h, and the clay samples with an additive on the shortened firing curve of 21 h.

Analysis of results:

- The reduction of the firing cycle from 24 hours to 21 hours saves 15% of energy

- Analysis of the hardness of the fired brick is shows that the firing cycle can be further accelerated (shortened) as the hardness of the brick with an additive was 17,34 MPa while in bricks without additives (fired on the 24 h cycle) was 13,98 MPa.