Filtered kaolinitic clay-based product with feldspar addition

Abstract

The subject of the invention relates to a kaolinitic clay, which, despite comprising feldspar instead of chemical additive and despite being unground, still has the levels of filtration time, plasticity, and strength at least corresponding to the levels present in the case kaolinitic clay comprises chemical additives, and to a method for obtaining said kaolinitic clay. The filtered kaolinitic clay according to the invention basically comprises 85-90% by weight filtered kaolinitic clay and 10-15% by weight Na feldspar.

Description

[0001] FILTERED KAOLINITIC CLAY-BASED PRODUCT WITH FELDSPAR ADDITION

[0002] Subject of the Invention

[0003] The subject of the invention relates to a kaolinitic clay, which, despite comprising feldspar instead of chemical additive and despite being unground, still has the levels of filtration time, plasticity, and strength at least corresponding to the levels present in the case kaolinitic clay comprises chemical additives, and to a method for obtaining said kaolinitic clay.

[0004] State of the Art

[0005] The clay group of minerals consists of the fine-grained materials, which exist in the nature in the form of aqueous aluminum and magnesium silicates and which are used especially in the ceramic, paper, petroleum, agriculture, casting, rubber, and cement industries. While the clay minerals may be present at the same location as the parent rock where they are formed, it is also possible that they are separated from the parent rock and transported to another location under the influence of water and exist in the deposited form at the location where they are transported. Some of the transported clays, including kaolinite that forms as a result of transportation of the kaolin mineral, a type of clay obtained from the granitic rocks, undergo ion exchange as they advance by rolling and contacting the other rocks during their transport and acquire a thin laminar structure with round grains as a result of friction. Consequently, they have high water retention capacity, plastic character, and high green strength, but also a high content of impurities.

[0006] The grain size and plasticity affecting the processing of the filtered clay have influence also on obtaining the filtered clay. Although the clays with fine grains, great surface area, capability to retain high water content in the structure, high plasticity, and high strength are preferred for these properties, they do not easily release the water due to the same properties and thus increase the time for draining the water. For the production of kaolinitic clay, the different clay sources are mixed according to their properties and in a way to provide the target recipe composition. After mixing, the material is subjected to the purification steps, is dewatered by being passed through the filter presses and is thus made ready for the drying process. The filtration time is one of the major limitations in the production. However, the filtration time increases with increasing plastic clay quantity in the clay recipes and the strength also increases in parallel. The shortening of this time may provide a capacity increase. The increased filtration time causes the prolongation of the whole process under the plant conditions and increases the operation costs, and the increased operation costs in turn increase the costs for obtaining the filtered clay. In order to be able to filter the clays having such properties by means of the existing methods, a sludge with low clay content, i.e. a low-density sludge, is fed into the presses, as a result of which a low quantity of filtered clay may be obtained in one go. The reason for this is that the clays with high plasticity agglomerate when mixed with water and brought into sludge form and lead to the clogging in the system as a result of adhesion.

[0007] In order to prevent the clogging, plenty of water is used in the process of dispersing the clay in water and the density of clay that is supplied to the system and that is to be expanded in the water is kept at all times at a level that would avoid the clogging in the system. In that case, it becomes necessary to repeatedly perform the feed into the system and to repeat the process steps over and over again in order to be able to obtain the targeted quantity of filtered clay within a certain time. This in turn causes an increase in the operation costs and the filtered clay costs. Another method employed according to the state of the art for the purpose of reducing the agglomeration and shortening the filtration time in the rheological structure involves the use of various chemical additives. While the filtration time without any additive being used is 10-12 hours and 8-10 hours respectively for the kaolinitic clays and the clays with lower plasticity, said time is reduced by 20-25% as a result of the use of chemical additives. However, the use of chemical additives adversely affects both the human health and the environment, as they lead to the exposure in the production process and also generate wastes after the production. The use of chemical additives also increases the production costs.

[0008] For the reasons mentioned above, there is a need for the products, which, despite lacking any chemical additive and any substance with similar effects to those of the chemical additives, provide a filtration time for the kaolinitic clays that is at least the same as the filtration time achieved in the presence of such additives and substances and which at the same time have the ideal levels of plasticity and strength. Accordingly, the manufacturers are in search of the substances, which have the properties similar to the technical properties of the chemical additives enabling said chemical additives to be preferred in such fields, reduce the requirement for said chemical additives, and lack any adverse health effect.

[0009] Our country is in a geography rich in the sodium feldspar mineral. The feldspar reserve of Turkey accounts for around 14% of the worldwide reserve. Feldspar is used in high quantities as a sintering agent in the ceramic and glass industries and as a filler or a functional additive in the rubber, plastic, and paint industries. While the feldspar improves the hardness, durability, and chemical corrosion resistance of the finished product, it also serves as a barrier by lowering the melting temperature of the finished product, owing to its calcium oxide, potassium oxide, and sodium oxide contents. Feldspar has no plasticity, and thus, it does not negatively affect the filtration time of the clay and does not cause a reduction in the strength. Consequently, it is envisaged that it would be possible to obtain the products, which have properties similar to those of the products with chemical additives used in the state of the art, upon the use of a correct quantity of feldspar with similar properties, instead of using high quantities of the chemical additives.

[0010] Both the feldspar and the filtered kaolinitic clay are generally used in the ceramic and glass industries. They are both used as glazing ingredients in the production of ceramics. They are both natural minerals and are abundant in the earth. Both the feldspar and the filtered kaolinitic clay are resistant to high heat, and therefore, they are used in numerous industrial applications. Both the feldspar and the filtered kaolinitic clay have a white or light color and have similar mineralogical properties. Therefore, it is considered that they are two ingredients, which could be compatible with each other in terms of their properties.

[0011] Object of the Invention

[0012] The subject of the invention relates to a kaolinitic clay-based product, which comprises feldspar instead of chemical additives in order to shorten the filtration time of the kaolinitic clay, leads to no adverse effect on the plasticity and strength, and has the properties that are similar to or are an improved version of the properties of the finished products obtained by the use of the additives. In particular, it is made possible to obtain, within the same time or within a shorter time and without any clogging in the system, the same or greater quantity of the filtered clay compared to that obtained in one go according to the state of the art, by preserving the chemical properties of the fine-grained clays with high plasticity. With the invention, the filtration time of the kaolinitic clay, which is filtered in 420 minutes according to the state of the art, has been reduced to as short as 310 minutes. This provides a 25% saving on time and energy and enables a reduction in the production costs. The effect of the feldspar and the other chemical additives on the filtration time of the clay may vary depending on the specific material composition and the conditions of application. For this reason, these quantities are quite important for the achievement of the technical effect provided by the invention and the solution of the respective technical problem. The importance of this issue may also be understood from the analysis results of the test compositions.

[0013] Another object of the invention is to develop a kaolinitic clay-based product, the filtration rate of which is increased with the raw materials that are environment- and human healthfriendly.

[0014] Another object of the invention is to provide around 1-10% by weight of the feldspar quantity to be present in the filtered kaolinitic clay from the feldspar present in the vitrified sludge for which the clay is to be used as the raw material. Due to its high degree of hardness, the feldspar mineral is ground prior to use in the recipes for the ceramic applications. In the present study, a balance is achieved by the use of less feldspar in the final recipe as a result of adding, when preparing the clay recipe, the feldspar up to a quantity that would allow the expansion in the expander. Under the normal conditions, the feldspar is prepared by way of being ground in the mills and has high grinding cost. Therefore, it is evident that a cost advantage will be provided upon the use of the product according to the invention.

[0015] Another object of the invention is to provide a new field of use for the feldspar. The feldspar simply regulates the rheological properties of the clay and causes no change in the chemical properties of the same; with this feature, the feldspar offers further advantages for the manufacturers.

[0016] Description of the Tables

[0017] Table 1. Chemical, casting, and firing properties of the first group of test compositions

[0018] Table 2. Chemical, casting, and firing properties of the second group of test compositions

[0019] Description of the Invention

[0020] The subject of the invention relates to a kaolinitic clay, which, despite comprising feldspar instead of chemical additive and despite being unground, still has the levels of filtration time, plasticity, and strength at least corresponding to the levels present in the case kaolinitic clay comprises chemical additives, and to a method for obtaining said kaolinitic clay.

[0021] In order to obtain the kaolinitic clay recipe according to the invention, various test compositions were prepared by the use of the filtered kaolinitic clay in quantities varying in the range of 60-75% by weight in combination with Na feldspar in quantities varying in the range of 25-40% by weight or in combination with K feldspar in quantities varying in the range of 25-40% by weight, the test compositions were subjected to the chemical analyses and the casting properties of the same were determined. In the compositions, Na feldspar comprising 0.24% by weight K.K. (LOI), 69.56% by weight SiC>2, 18.55% by weight AI2O3, 0.08% by weight Fe2Os, 0.1% by weight TiCh, 0.96% by weight CaO, 0.1% by weight MgO, 9.99% by weight Na2O, and 0.4% by weight K2O was used. In the compositions, K feldspar comprising 0.2% by weight K.K. (LOI), 71.32% by weight SiO2, 15.65% by weight AI2O3, 0.14% by weight Fe20s, 0.01% by weight TiO2, 0.36% by weight CaO, 0.1% by weight MgO, 2.1% by weight Na2O, and 10.01% by weight K2O was used. The chemical properties and the casting and firing properties of the test compositions respectively comprising 75% by weight filtered kaolinitic clay and 25% by weight Na feldspar, 60% by weight filtered kaolinitic clay and 40% by weight Na feldspar, 75% by weight filtered kaolinitic clay and 25% by weight K feldspar, and 60% by weight filtered kaolinitic clay and 40% by weight K feldspar are given in Table 1.

[0022] Table 1. Chemical, casting, and firing properties of the first group of test compositions

[0023] The analysis results in Table 1 were evaluated and it was noted that the increases occurred, as expected, in the values of Na20 and K2O in the compositions after the addition of Na and K feldspar. In mineralogical terms, the casting properties also showed variability, due to the addition of hard minerals to the structure. Whereas the casting concentration increased, the electrolyte quantity required to balance the viscosity and the fluidity of the sludge decreased. The value of the dry bond strength, which is related to the grain size, decreased with increasing feldspar quantity in the compositions. However, these are on the levels possible to be compensated within the recipe. The filtration times showed a tendency of decrease by 25% with increasing feldspar quantity in the compositions. Nevertheless, the lower values were also screened in the trials and no big difference was noticed in the filtration time. According to the results, it is possible to shorten the filtration time and provide a semi-finished product by mixing the clay and the feldspar.

[0024] As a result of the evaluation of the analyses, it was observed that the compositions prepared with K feldspar did not sinter sufficiently. It was understood that there was no sufficient melting action in the system with increasing content of K2O, and thus, the addition of K feldspar did not cause any negative effect. Thus, the trials were based on the content of Na2O, which has higher extent of sintering behavior. Consequently, it was decided to proceed with the tests by the use of Na feldspar. However, since an extent of sintering that was more than desired was noted in the compositions prepared with Na feldspar, it was decided to reduce the quantity of Na feldspar in the new compositions to be prepared. It was realized that the phase deformation increased and the stabilization of the structure was deteriorated with increasing quantity of excess Na feldspar. Various test compositions were prepared by the use of the filtered kaolinitic clay in quantities varying in the range of 85-

[0025] 90% by weight in combination with Na feldspar in quantities varying in the range of 10-15% by weight, the test compositions were subjected to the chemical analyses and the casting properties of the same were determined. The chemical properties and the casting and firing properties of the test compositions respectively comprising 90% by weight filtered kaolinitic clay and 10% by weight Na feldspar and 85% by weight filtered kaolinitic clay and 15% by weight Na feldspar are given in Table 2. According to the results of the trials conducted, it was understood that a filtered clay that is produced with the composition comprising 10% by weight filtered kaolinitic clay and 15% by weight Na feldspar has better quality than that obtained in the state of the art was

[0026] Table 2. Chemical, casting, and firing properties of the second group of test compositions

[0027] The filtered kaolinitic clay according to the invention basically comprises 85-90% by weight filtered kaolinitic clay and 10-15% by weight Na feldspar. The effect of the feldspar and the other chemical additives on the filtration time of the clay may vary depending on the specific material composition and the conditions of application. No adverse effect with the possibility of impacting the production was observed on the plasticity values upon the addition of feldspar. As for the values of strength, a decrease of nearly 10% was observed due to the effect of feldspar, which is a hard mineral. However, this decrease is at a level tolerable in the recipe for the finished product. For this reason, these quantities are quite important for the achievement of the technical effect provided by the invention and the solution of the respective technical problem. The importance of this issue may also be understood from the analysis results of the test compositions.

[0028] The filtered kaolinitic clay according to the invention comprises 85% by weight filtered kaolinitic clay and 15% by weight Na feldspar.

[0029] The filtered kaolinitic clay according to the invention comprises 90% by weight filtered kaolinitic clay and 10% by weight Na feldspar.

[0030] A part of the feldspar quantity to be present in the filtered kaolinitic clay according to the invention is provided from the feldspar present in the vitrified sludge for which the clay is to be used as the raw material. Since the advantage of directly feeding in the expander without having to perform the grinding process will result, there will be a corresponding contribution in terms of the cost. The reason is that, under the normal conditions, the feldspar is prepared by way of being ground in the mills and has high grinding cost. Therefore, it is evident that a cost advantage will be provided upon the use of the product according to the invention.

[0031] The filtered kaolinitic clay according to the invention comprises Na feldspar comprising 0.20- 0.30% by weight, preferably 0.24% by weight, K.K. (LOI); 68-72% by weight, preferably 69.56% by weight, SiCh; 16-20% by weight, preferably 18.55% by weight, AI2O3; 0.04-0.1% by weight, preferably 0.08% by weight, Fe2Os; 0.05-0.2% by weight, preferably 0.1% by weight, TiCh; 0.5-1.2% by weight, preferably 0.96% by weight, CaO; 0.05-1.2% by weight, preferably 0.1% by weight, MgO; 8.5-10% by weight, preferably 9.99% by weight, Na2O; and 0.4% by weight K2O.

Claims

CLAIMS1. A filtered kaolinitic clay-based product characterized in that the product comprises85-90% by weight filtered kaolinitic clay and 10-15% by weight Na feldspar.

2. A product according to Claim 1 characterized in that the product comprises 85% by weight filtered kaolinitic clay and 15% by weight Na feldspar.

3. A product according to Claim 1 characterized in that the product comprises 90% by weight filtered kaolinitic clay and 10% by weight Na feldspar.

4. A product according to any one of the preceding claims characterized in that around 1-10% by weight of the feldspar is the feldspar present in the vitrified sludge for which the clay is to be used as the raw material.

5. A product according to any one of the preceding claims characterized in that the product comprises Na feldspar comprising 0.20-0.30% by weight K.K. (LOI); 68-72% by weight SiCh; 16-20% by weight AI2O3; 0.04-0.1% by weight Fe2Os; 0.05-0.2% by weight TiCh; 0.5-1.2% by weight CaO; 0.05-1.2% by weight MgO; 8.5-10% by weight Na2O; and 0.4% by weight K2O.

6. A product according to any one of Claims 1-4 characterized in that the product comprises Na feldspar comprising 0.24% by weight K.K. (LOI); 69.56% by weight SiO2; 18.55% by weight AI2O3; 0.08% by weight Fe2Os; 0.1% by weight TiO2; 0.96% by weight CaO; 0.1% by weight MgO; 9.99% by weight Na2O; and 0.4% by weight K2O.

7. A product according to any one of the preceding claims characterized in that the feldspar is the unground feldspar.

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