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Title:
CLAY FILTRATION METHOD AND FILTERED CLAY OBTAINED BY SAID METHOD
Document Type and Number:
WIPO Patent Application WO/2022/139760
Kind Code:
A2
Abstract:
The subject of the invention relates to a clay filtration method, which allows the use of a raw material with increased weight per liter by preserving the chemical properties of especially the fine-grained clays with high plasticity, enables filtration times for the same to be reduced, and relates to the filtered clay obtained by said method. The clay filtration method according to the invention basically comprises the process steps of dispersing the clay in water in the presence of at least one first agent that enables the clay grains to diverge by sliding over one another and filtering the clay in the presence of at least one second agent that enables the clay grains to converge to thereby easily release the water in their structure.

Inventors:
UCAR DEMIR TUGBA (TR)
HALLAC BURCU CEREN (TR)
Application Number:
PCT/TR2021/051442
Publication Date:
June 30, 2022
Filing Date:
December 20, 2021
Export Citation:
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Assignee:
ESAN ECZACIBASI ENDUSTRIYEL HAMMADDELER SANAYI VE TICARET ANONIM SIRKETI (TR)
International Classes:
C04B33/00; B28C1/00
Attorney, Agent or Firm:
GOZTEPE, Burcu Eylem (TR)
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Claims:
CLAIMS

1. A clay enrichment/filtration method comprising the process steps of mechanically dispersing/expanding the clay blend in a certain amount of water in rotary sieves known as trommel, then conveying the formed sludge to the sizers and then to the separator called cyclone, and filtering and drying the sludge characterized in that the method comprises the process steps of

• dispersing the clay fed into the system in water in the presence of at least one first agent that enables the clay grains to diverge by sliding over one another and/or

• filtering the clays in the presence of at least one second agent that enables the clay grains in the clay sludge to converge, thereby to easily release the water in their structure.

2. A method according to Claim 1 characterized in that said first agent is added at the trommel inlet, at the point where the clays first contact the water.

3. A method according to Claim 1 or Claim 2 characterized in that said second agent is added at the cyclone outlet.

4. A method according to Claim 1 or Claim 2 characterized in that a mixture containing polyacrylate, i.e. polyacrylic acid, and sodium salt is used as the first agent.

5. A method according to Claim 1 or Claim 4 characterized in that the first agent is used in a weight that is 0.1-0.3% of the weight of the clay fed into the system.

6. A method according to Claim 1 or Claim 4 characterized in that the first agent is used in a weight that is 0.2% of the weight of the clay fed into the system.

7. A method according to any one of the preceding claims characterized in that a mixture containing the compounds polyethylene polyamine and tetraethylenepentamine is used as the second agent.

8. A method according to Claim 1 or Claim 7 characterized in that the second agent is used in a weight that is 0.015-0.025% of the weight of the clay fed into the system.

9. A method according to Claim 1 or Claim 7 characterized in that the second agent is used in a weight that is 0.020% of the weight of the clay fed into the system.

10. A method according to Claim 1 characterized in that said sludge is collected in at least one sludge tank.

11. A method according to Claim 1 characterized in that said filtration process is realized in the filter presses.

12. A method according to any one of the preceding claims characterized in that the method comprises the process step of adding, prior to the filtration process, at least one third agent that enables the clay grains to diverge by sliding over one another.

13. A method according to Claim 10 or Claim 12 characterized in that said third agent is added into the sludge tank.

14. A method according to Claim 12 or Claim 13 characterized in that the lime is added as the third agent.

15. A method according to any one of the preceding claims characterized in that it is a method for the filtration of kaolinitic clay. 16. Filtered clay characterized in that the filtered clay is obtained by a method according to any one of the preceding claims.

17. Filtered clay according to Claim 16 characterized in that the filtered clay contains the clay grains with size less than 45 microns.

18. Filtered clay according to Claim 16 or Claim 17 characterized in that said filtered clay is the filtered kaolinitic clay obtained by way of filtration of kaolinitic clay.

Description:
CLAY FILTRATION METHOD AND FILTERED CLAY OBTAINED BY SAID METHOD

Subject of the Invention

The subject of the invention relates to a clay filtration method, which allows the use of a raw material with increased weight per liter by preserving the chemical properties of especially the fine-grained clays with high plasticity, enables filtration times for the same to be reduced, and thus enables a quantity of filtered clay that is greater than the quantities obtained in the state of the art to be obtained in one go in a shorter time and without any clogging in the system, and to the filtered clay obtained by said method.

State of the Art

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.

It is necessary to remove said impurities via an enrichment/filtration process in order to ensure that said characteristic features of such clays, which, with their fine-grained structure, high water retention capacity and plasticity, are quite easy to be brought into the workable sludge form and have a high strength, are not altered adversely. The enrichment process comprises the steps of washing the clay with water and expanding the same mechanically, classifying the same according to size and settling the same. The clays with impurities and with different properties, which are obtained from different pits, are passed through the crushers to be reduced to the determined sizes and are blended so that they will have the same finished product features, and a clay that is free of impurities/enriched/filtered, has high plasticity and is ready for processing is obtained by subjecting the clay obtained from the blending to the trommel, expander, sieve and cyclones.

According to the state of the art, the filtered clay is obtained by mechanically dispersing/expanding the clay blend in a certain amount of water and removing the coarsegrained impurities from the same in the rotary sieves known as trommel, conveying with the help of a centrifugal pump the expanded and sieved clay first to the pump pond and then from the pump pond to the 350-micron multiple batch sizers/sieves, pumping the sludge with a clay content with size smaller than 350 microns that has passed through the sizers to the first stage cyclone, the coarse grains within the rapidly rotating suspension in the first stage cyclone moving towards the bottom outlet of the cyclone under the influence of the centrifugal force while the small-size grains moving upward and being received as the overflow from the top outlet, delivering the overflow with the help of a pump first to the product tank and from the product tank to the sludge tank, pumping the sludge from the sludge tank to the filter presses, which enable the water content of the sludge to be removed with the help of pressure, and draining the water content of the sludge. The clay, the water content of which has been drained, is fed first into the pasta machine and from the pasta machine into the band dryers in order to reduce its moisture content. The finished products taken out of the dryers are allowed to stand in the product compartments. The underflow from the first stage cyclone containing the coarse clays is conveyed to another cyclone. The overflow of the other cyclone is fed back into the pump pond and is subjected to the same process steps. In this way, it is attempted to obtain more filtered clay from the clay that is supplied to the system.

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. The increased draining 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 method, 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. 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.

In order to eliminate said drawbacks, a clay filtration method has been developed within the scope of the invention, wherein said method involves the use of the agents, which enable the grains of clay fed into the system to be filtered to diverge by sliding over one another and/or enable the grains of clay within the clay sludge entering the presses to converge to thereby easily release the water in their structure, and wherein said method is also suitable forfiltering the fine-grained clays including kaolinitic clay. The density of clay is increased in the clay sludge prepared by this method, a greater quantity of clay compared to that of the state of the art may be supplied to the system, the efficiency of the filtration process is improved and hence it becomes possible to obtain a quantity of filtered clay greater than the quantity of filtered clay obtained in one go according to the state of the art, without causing any clogging in the system. Moreover, the time for draining the water content of the clay sludge is shortened, the filtered clay is obtained in one go from the clay fed into the system in a shorter time as compared to the state of the art, and the operation costs are thus reduced. The method where the agents having said properties are employed does not alterthe chemical properties of the clay and only regulates the rheological properties thereof, and with this aspect, it provides advantage to the producers.

Object of the Invention

An object of the invention is to develop a clay filtration method, which enables a greater quantity of clay as compared to the state of the art, i.e. a clay with increased weight per liter, to be fed into the system and which enables a greater quantity of filtered clay to be obtained in one go, by way of dispersing the clay in water and separating the clay grains from one another.

Another object of the invention is to develop a clay filtration method, which shortens the time for draining the water content of the clay sludge and thus enables the filtered clay to be obtained in a shorter time as compared to the state of the art from the clay fed into the system.

Another object of the invention is to develop a clay filtration method, which achieves the functions mentioned under the other objects of the invention without altering the chemical properties of the clay.

Another object of the invention is to develop a clay filtration method, having the features mentioned under the previous objects of the invention, for filtering the kaolinitic clay.

Description of the Tables

Table 1. Chemical properties of the filtered clay obtained by the use of the agent, which enables the clay grains to converge to thereby easily release the water content in their structure

Table 2. Casting and firing properties of the filtered clay obtained by the use of the agent, which enables the clay grains to converge to thereby easily release the water content in their structure

Table 3. Chemical properties of the filtered clays obtained by the use of the agent, which enables the clay grains to diverge by sliding over one another Table 4. Casting and firing properties of the filtered clays obtained by the use of the agent, which enables the clay grains to diverge by sliding over one another

Table 5. Filtration times for the filtered clays obtained with clay sludge having different clay densities

Table 6. Chemical properties of the filtered clay obtained by the combined use of the agents

Table 7. Casting and firing properties of the filtered clay obtained by the combined use of the agents

Description of the Invention

The subject of the invention relates to a clay filtration method, which allows the use of a raw material with increased weight per liter by preserving the chemical properties of especially the fine-grained clays with high plasticity, enables filtration times for the same to be reduced, and thus enables a quantity of filtered clay that is greater than the quantities obtained in the state of the art to be obtained in one go in a shorter time and without any clogging in the system, and to the filtered clay obtained by said method.

The filtered clay is basically obtained by mechanically dispersing/expanding the clay blend in a certain amount of water in rotary sieves known as trommel, then conveying the clay to the sizers/sieves and then to the separators called cyclone, and finally filtering the sludge through the filter presses and drying the same.

In more detail, the filtered clay is obtained by mechanically dispersing/expanding the clay blend in a certain amount of water and removing the coarse-grained impurities from the same in the rotary sieves known as trommel, conveying with the help of a centrifugal pump the expanded and sieved clay first to the pump pond and then from the pump pond to the 350- micron multiple batch sizers/sieves, pumping the sludge with a clay content with size smaller than 350 microns that has passed through the sizers to the cyclone, the coarse grains within the rapidly rotating suspension in the cyclone moving towards the bottom outlet of the cyclone underthe influence of the centrifugal force while the small-size grains moving upward and being received as the overflow from the top outlet, delivering the overflow with the help of a pump first to the product tank and from the product tank to the sludge tank, pumping the sludge from the sludge tank to the filter presses, which enable the water content of the sludge to be removed with the help of pressure, and draining the water content of the sludge. The clay, the water content of which has been drained, is fed first into the pasta machine and from the pasta machine into the band drying oven in order to reduce its moisture content. The finished products taken out of the drying oven are allowed to stand in the product compartments.

The clay filtration method being the subject of the invention basically comprises the process step of adding at least one first agent in the aforesaid method. An alternative embodiment of the invention comprises the process step of adding at least one second agent.

The method developed within the scope of the invention comprises the process steps of

• dispersing the clay fed into the system in water in the presence of at least one first agent that enables the clay grains to diverge and separate by sliding over one another and/or

• obtaining a clay sludge that contains fine clay grains by filtering the clays in the clay sludge in the presence of at least one second agent that enables the clay grains to converge to thereby easily release the water in their structure.

The process of dispersion in water in the presence of at least one first agent is performed in the trommel and the process of filtration in the presence of at least one second agent is performed in the filter presses. Said first agent is added at the trommel inlet, at the point where the product first contacts the water, while said second agent is added at the cyclone outlet.

In an alternative embodiment of the invention, the addition of a third agent to the clay sludge in the sludge tank is preferably performed in order to further shorten the filtration time.

When developing the method according to the invention, shortening the filtration time of the clay and/or increasing the clay density in the sludge while avoiding any alteration in the chemical properties of the clay is adopted as the principle. For the purpose of evaluating the suitability of performing said functions by the use of chemical agents, the studies were conducted to obtain filtered clay using varying types and quantities of agents.

Within the scope of the studies conducted, the effect of the various types and quantities of agents, which enable the clay grains to diverge by sliding over one another, on the chemical, casting and firing properties of the filtered clay obtained, especially on the time for draining the water, was assessed. Moreover, the effect of the various types and quantities of agents, which enable the clay grains in the clay sludge to converge to thereby easily release the water in their structure, on the chemical, casting and firing properties of the filtered clay obtained, especially on the clay density/weight per liter, was examined. Subsequently, the filtered clay was obtained by the combined use of the agents with said functions in the determined types and quantities, and the effect of combined use of the agents on the chemical, casting and firing properties of the filtered clay obtained, especially on the time for draining the water and on the clay density/weight per liter, was examined.

As a result of the studies, the agents with suitable properties to be used in the method according to the invention, which, without altering the chemical properties of the clay, enable the filtration time of the clay to be reduced and/or more clay to be fed into the system and thus the density of clay within the sludge to be increased, were determined. Within the scope of the studies performed for shortening the time for draining the water content of the clay sludge, in order to determine the agent enabling the clay grains in the clay sludge to converge to thereby easily release the water in their structure, various clay sludges were prepared by adding varying proportions of at least one of preferably lime, aluminum sulfate or an agent mixture containing the compounds polyethylene polyamine and tetraethylenepentamine as said agent to the clay sludge obtained by dispersing the clay in water. The proportions of the agents used were determined according to the weight of the clay fed into the system.

The 1 st clay sludge prepared comprises the lime, the weight of which is 0,15% of the weight of the clay fed into the system, as the agent that enables the clay grains in the clay sludge to converge to thereby easily release the water in their structure.

The 2 nd clay sludge prepared comprises aluminum sulfate, the weight of which is 0,15% of the weight of the clay fed into the system, as the agent that enables the clay grains in the clay sludge to converge to thereby easily release the water in their structure.

The 3 rd clay sludge prepared comprises an agent mixture containing the compounds polyethylene polyamine and tetraethylenepentamine, the weight of which is 0,015% of the weight of the clay fed into the system, as the agent that enables the clay grains in the clay sludge to converge to thereby easily release the water in their structure.

The 4 th clay sludge prepared comprises an agent mixture containing the compounds polyethylene polyamine and tetraethylenepentamine, the weight of which is 0,020% of the weight of the clay fed into the system, as the agent that enables the clay grains in the clay sludge to converge to thereby easily release the water in their structure.

The 5 th clay sludge prepared comprises an agent mixture containing the compounds polyethylene polyamine and tetraethylenepentamine, the weight of which is 0,025% of the weight of the clay fed into the system, as the agent that enables the clay grains in the clay sludge to converge to thereby easily release the water in their structure.

Each of the clay sludges prepared was subjected to sizing, the water content was drained from the sludge comprising the fine clay grains that was output as overflow from the sizing, and the analysis results for the chemical, casting and firing properties of the filtered clay obtained from each clay sludge were compared to the analysis results of other filtered clays and to the analysis results of the filtered clay obtained by draining the water content of the clay sludge not comprising said agent. Thus, the effect of said agent on the time for draining the water content of the clay sludge was evaluated. It was observed that the water content of the 1 st clay sludge was drained in 525 minutes, the water content of the 2 nd clay sludge was drained in 510 minutes, the water content of the 3 rd clay sludge was drained in 440 minutes, the water content of the 4 th clay sludge was drained in 480 minutes, and the water content of the 5 th clay sludge was drained in 440 minutes. The time for draining the water content was about 570 minutes from the clay sludge without any agent addition. The lime and aluminum sulfate compound were observed to also shorten the draining time for the water content of the clay sludge. However, they were able to reduce the draining time at most by 0.5-1 hour despite being added in a quantity about 10 times more than the ratio of the compounds polyethylene polyamine and tetraethylenepentamine. The time for draining the water content was 570 minutes for the clay sludge not containing said agent, i.e. for the clay sludge obtained by the method employed in the state of the art, and it was observed that said time could be shortened by 2-2.5 hours by the use, as said agent, of the agent mixture containing the compounds polyethylene polyamine and tetraethylenepentamine and having a weight that is 0.015-0.025% of the weight of the clay fed into the system.

The use of every type and every ratio of agent that were employed in the studies is possible within the scope of the invention. However, the use of the agent mixture containing the compounds polyethylene polyamine and tetraethylenepentamine, the weight of which is 0.020% of the weight of the clay fed into the system, as the agent that enables the clay grains in the clay sludge to converge to thereby easily release the water in their structure was preferred in the continuation of the studies as it was more effective.

The analysis results for the filtered clay obtained by the use of the agent mixture containing the compounds polyethylene polyamine and tetraethylenepentamine, the weight of which is 0.020% of the weight of the clay fed into the system, and the analysis results for the filtered clay obtained without using said agent are provided in the following tables; it can be seen from the tables that the rheological properties of the clay were regulated and the draining time for the water content of the clay was reduced as a result of the use of the agent, whereas the chemical properties and some critical casting and firing properties of the clay did not change.

Table 1. Chemical properties of the filtered clay obtained by the addition of the agent, which enables the clay grains to converge to thereby easily release the water content in their structure Table 2. Casting and firing properties of the filtered clay obtained by the addition of the agent, which enables the clay grains to converge to thereby easily release the water content in their structure

In an alternative embodiment of the invention, the addition of at least one second agent that enables the clay grains to diverge by sliding over one another and that will allow a greater quantity of clay to be fed into the system was performed. Various clay sludge compositions were prepared by way of adding, at varying ratios, a mixture as at least one second agent, which preferably contains polyacrylate, i.e. polyacrylic acid, and sodium salt, at the point where the clay first contacts the water during the dispersion of the clay in the water.

The 6 th clay sludge prepared comprises the mixture containing polyacrylate, i.e. polyacrylic acid, and sodium salt as the agent that enables the clay grains to diverge by sliding over one another at a quantity such that the weight of said agent is 0.1% of the weight of the clay fed into the system.

The 7 th clay sludge prepared comprises the mixture containing polyacrylate, i.e. polyacrylic acid, and sodium salt as the agent that enables the clay grains to diverge by sliding over one another at a quantity such that the weight of said agent is 0.2% of the weight of the clay fed into the system.

The 8 th clay sludge prepared comprises the mixture containing polyacrylate, i.e. polyacrylic acid, and sodium salt as the agent that enables the clay grains to diverge by sliding over one another at a quantity such that the weight of said agent is 0.3% of the weight of the clay fed into the system.

Each clay sludge prepared was subjected to sizing, the overflow containing the fine particles separated as a result of sizing was freed of its water content at the draining step, and the chemical, casting and firing properties, especially the density/weight per liter, of the filtered clays obtained were analyzed. The analysis results of each filtered clay were compared to the analysis results of other filtered clays and to the analysis results of the filtered clay obtained with the clay sludge not comprising said agent. Thus, the effect of said agent on the density of clay in the sludge was examined.

It was observed that the 6 th clay sludge, the 7 th clay sludge and the 8 th clay sludge had the same clay density and that the density was increased as compared to the clay density of the clay sludge not containing said agent. The viscosity of the sludge was observed to decrease with increasing agent content in the clay sludge. The clay grains contained in each sludge were observed to diverge and become liberated and the times for draining the water content were observed to shorten, owing to the agent used. Further, an increase was observed in the dry bond strength, i.e. the strength, of the filtered clay with increasing quantity of the agent. The reason for this is that the agent bonded owing to its chemical contents to the fine-grained clays.

An examination of the crude forms of the filtered clays obtained from each clay sludge revealed an increase in the yellowness of the color of the crude clay with increasing quantity of the agent. However, the yellowness of the ceramic materials obtained following the firing of the clays decreased with increasing quantity of the agent. The reason for this is that the soluble salts and sulfates gathered on the surface as a result of the dissolution of the agent in water. The trials involving the glaze application were also performed considering the possibility that this condition could cause agglomerations on the glaze to be applied to the surface of the ceramic material and no agglomeration or surface defect resulting from the soluble salts was observed in the glazed ceramic materials.

The analysis results for the filtered clay obtained by the use of the mixture containing polyacrylate, i.e. polyacrylic acid, and sodium salt as the agent that enables the clay grains to diverge by sliding over one another at a quantity such that the weight of said agent is 0.2% of the weight of the clay fed into the system and the analysis results for the filtered clay obtained without using said agent are provided in the following tables; it can be seen that the use of the agent did not alter the chemical properties of the clay and did not adversely affect some critical casting and firing properties.

Table 3. Chemical properties of the filtered clays obtained by the addition of the agent, which enables the clay grains to diverge by sliding over one another

Table 4. Casting and firing properties of the filtered clays obtained by the addition of the agent, which enables the clay grains to diverge by sliding over one another As a result of the determination and evaluation of the properties of the filtered clays obtained in the studies performed, it was concluded that the use of the agents employed in the studies is possible within the scope of the invention. In the studies, the chemical properties of the clay sludge containing the coarse grains output from the sizing process, i.e. chemical properties of the underflow, were also examined and it was observed that the use of the second agent did not alter the properties of the coarse grains either. Within the scope of the invention, the mixture containing polyacrylate, i.e. polyacrylic acid, and sodium salt as the agent that enables the clay grains to diverge by sliding over one another was preferred to be used in a quantity such that the weight of said agent is 0.2% of the weight of the clay fed into the system. The dry matter concentration in the mixture is 44-46%. A certain quantity of the agent was added to the sludges of different density in order to more clearly demonstrate the effect of increasing the density/weight per liter of the clays in the clay sludge on the filtration time. Each of the filtered clays obtained with the sludges prepared with the agent that enables the clay grains to diverge by sliding over one another, the weight of said agent being 0.2% of the weight of the clay fed into the system, was analyzed and the properties of each can be seen in Table 5. The times for draining the water content of each composition were observed to reduce with increasing density. Further, whereas the clay sludge according to the state of the art may have a maximum clay content of 25-30% by weight so that no clogging is caused in the system, it may now contain maximum 40% by weight clay owing to the ability to increase the weight per liter by the addition of the agent. In this way, it becomes possible to feed more clay into the system and obtain more filtered clay; in other words, the efficiency of the process for obtaining the filtered clay may be increased.

Table 5. Filtration times for the filtered clays obtained with clay sludge having different clay densities

Following the determination of the agents to be used within the scope of the invention and the use ratios thereof, the effect of the combined use of the agents on the chemical, casting and firing properties of the filtered clay, especially on the time for draining the water and on the density/weight per liter, was examined.

The filtered clay was obtained by the addition of the first agent, which enables the clay grains to diverge by sliding over one another, at a quantity such that the weight of said first agent is 0.2% of the weight of the clay fed into the system, and the second agent, which enables the clay grains in the clay sludge to converge to thereby easily release the water in their structure, at a quantity such that the weight of said second agent is 0.020% of the weight of the clay fed into the system. The chemical, casting and firing properties of the filtered clay obtained by the use of two agents within the scope of the invention were analyzed, and the results were compared to the analysis results for the filtered clay obtained without using any agent, the filtered clay obtained by the addition of the first agent only and the filtered clay obtained by the addition of the second agent only. The analysis results can be seen in Table 6 and Table 7.

Table 6. Comparison of the chemical properties of the filtered clay obtained by the combined use of the agents

Table 7. Comparison of the casting and firing properties of the filtered clay obtained by the combined use of the agents

As a result of all the studies performed, the following were observed:

• The dry bond strength, i.e. strength, of the filtered clays obtained by the separate or combined use of said agents for obtaining the filtered clay were higher as compared to those of the filtered clays obtained by the method of the state of the art;

• the soluble salts and sulfates agglomerated on the surface during the drying, which caused the color to become darker but did not have an adverse effect after firing and glazing;

• no change occurred in the rheological properties upon increasing the density/weight per liter and it was possible to continue the study with appropriate viscosity and thixotropy;

• the efficiency of the clay enrichment/filtration process was increased by increasing the clay density in the clay sludge; i.e., a greater quantity of filtered clay than that of the state of the art was obtained;

• it was possible to feed a greater quantity of clay into the system in one go as compared to the quantity fed according to the state of the art and therefore the quantity of clay obtained in one go was greater than that in the state of the art;

• the times for draining the water content of the clay sludge were shortened and it was possible to easily drain the water content of even the sludge with high clay density; and

• the separate or combined use of the agents did not cause any change in the chemical properties of the filtered clay obtained, while such use of agents regulated the rheological properties of the same.

With the study performed within the scope of the invention, the agents and the use ratios of such agents suitable for use in developing the method that enables the filtration time of the clay to be shortened and/or the density of the clay in the sludge to be increased without altering the chemical properties of the clay were determined. The method according to the invention is characterized by the processes of

• dispersing the clay fed into the system in water in the presence of at least one first agent that enables the clay grains to diverge and separate by sliding over one another and/or

• obtaining a clay sludge that contains fine clay grains by filtering the clays in the clay sludge in the presence of at least one second agent that enables the clay grains to converge to thereby easily release the water in their structure.

In the method according to the invention, a mixture of preferably polyacrylate, i.e. polyacrylic acid, and sodium salt is used as said first agent.

In the method according to the invention, the clay sludge is obtained by dispersing the clay in water in the presence of at least one first agent, the weight of which is preferably 0.1-0.3% of the weight of clay fed into the system.

In a preferred embodiment of the method according to the invention, the clay sludge is obtained by dispersing the clay in water in the presence of at least one first agent, the weight of which is 0.20% of the weight of clay fed into the system.

In the method according to the invention, the use of a mixture containing the compounds polyethylene polyamine and tetraethylenepentamine as said second agent was preferred.

In the method according to the invention, the clay sludge that contains fine clay grains is obtained by filtering the clay in the presence of at least one second agent, the weight of which is preferably 0.015-0.025% of the weight of clay fed into the system.

In a preferred embodiment of the method according to the invention, the second agent is added such that its weight is 0.020% of the weight of clay fed into the system.

It is possible to use the first agent and the second agent separately or in a combined manner in the method according to the invention.

A preferred embodiment of the method according to the invention comprises the process step of adding at least one third agent, said at least one third agent enabling the clay grains to converge to thereby easily release the water in their structure, to the clay sludge in the sludge tank that contains the fine clay grains, prior to the process step of draining the water content of the clay sludge.

In a preferred embodiment of the method according to the invention where a third agent enabling the clay grains to diverge by sliding over one another is added to the clay sludge in the sludge tank that contains the fine clay grains, prior to the process step of draining the water content of the clay sludge, said third agent is lime.

The subject of the invention also relates to the filtered clay obtained by said clay filtration method. In a preferred embodiment of the invention, the filtered clay contains the clay grains with size smaller than 45 microns.

The method according to the invention is preferably a method for filtering the kaolinitic clay and the filtered clay according to the invention obtained by this method is the filtered kaolinitic clay.

The clay obtained by way of dispersing the clay, which is fed into the system to be filtered, in water in the presence of at least one first agent that enables the clay grains to diverge by sliding over one another is also included in the scope of the invention.

The clay sludge containing the fine clay grains obtained by way of filtering the clays in the clay sludge in the presence of at least one second agent that enables the clay grains to converge to thereby easily release the water in their structure is also included in the scope of the invention.

Owing to the method according to the invention, a greater quantity of clay compared to that of the state of the art may be supplied to the system, also the efficiency of the filtration process is improved and hence, it becomes possible to obtain a quantity of filtered clay greater than the quantity of filtered clay obtained in one go according to the state of the art, without causing any clogging in the system. Moreover, the times for draining the water content of the clay sludge are shortened, the filtered clay is obtained in one go from the clay fed into the system in a shorter time as compared to the state of the art and the operation costs are thus reduced. The method where the agents having said properties are employed does not alter the chemical properties of the clay and only regulates the rheological properties thereof, and with this aspect, it provides advantage to the producers.