METHOD AND PLANT FOR PREPARING A MATERIAL SUITABLE FOR MANUFACTURING

CERAMIC TILES Technical field

[01] The present invention relates to a method and a plant for preparing a material, in particular in powder or in granular form, suitable for manufacturing ceramic tiles.

Prior art

[02] The need to mass-produce ceramic material products, in particular products such as tiles and the like, has long been known.

[03] Ceramic tiles are usually produced with a standardized technological system, which involves the continuous batching of raw materials to mix the different components intended to be part of the mixture. These are normally materials with very different physical and rheological characteristics: for example plastic materials, fluxes, stabilizers, etc. Each component is used to control one or more quality parameters of the product, such as stability in green, in dry, in firing, to achieve the desired quality of the fired ceramic tiles, for example made tangible by the color of the body formulation, by the water absorption capacity, dimensional regularity, the absence of surface defects and many other measurable parameters.

[04] The production process then proceeds with the wet or dry milling of the mixture of raw materials.

[05] In the case of dry milling, the raw materials, mixed according to a specific method, are milled in a roller or hammer mill, without adding water. Then, the milled body formulation is granulated, for example in a rotating drum, adding, only in this step, a specific, but reduced, amount of water.

[06] In the case of wet milling, however, the raw materials are added with a high quantity of water, usually equal to 35% of the total weight, so as to form an aqueous suspension called "slurry". The amount of water added to the solid raw materials can vary depending on the body formulation, for example it can reach over 40%.

[07] Wet milling usually takes place by means of mills, in which the mixture of raw materials is fed, together with a specific amount of water, and it comes out milled with residues between 3 and 8%, through a 63 micron sieve. These average reference values, for example, refer respectively to the production of porcelain stoneware and red-body floors.

[08] Wet milling has significant advantages over dry milling. In fact, it requires less frequent maintenance of the system, exploits the disintegrating power of water and, compared to dry milling, it offers the possibility of sieving at the previously mentioned fine grain sizes. Furthermore, the resulting body formulation is not subject to possible reclassification due to the difference in the specific weight of the raw materials in following transport. [09] Furthermore, while dry milling requires that the raw materials are selected from a limited number of materials, wet milling allows the widest choice of formulations, in order to obtain, as previously described, the control of the various process parameters and the desired end result.

[10] It should be emphasized that the non-extreme milling and the mixing obtained with the dry process are not optimal and that the result of sieving can also be problematic. Consequently, even the vitrification of a product obtained with a dry process can be problematic.

[11] Therefore, wet milling is generally preferred, which achieves products of high quality and resistance. In particular, with wet milling it is possible to obtain highly vitrified products, even below 0.2% water absorption, with minimal surface defects, and also having large size, with no complications of the production process.

[12] The wet process, however, requires the extraction of large quantities of water, to bring the body formulation mixture back to the moisture content, usually around or below 8%, necessary for forming the tiles.

[13] For this reason, in the plants known in the art, which carry out wet milling, very bulky and operationally expensive apparatuses are used, which extract excess water. These are the spray dryer, which extract the water from the slurry, feeding the latter under pressure, in the nebulized state, in countercurrent with a flow of hot air.

[14] The spray dryer has significant economic and environmental disadvantages, due to the large consumption of energy, water, as well as the emissions of dust and CO2.

[15] First of all, in fact, the rapid counter-current drying process, carried out by the spray dryer, requires large volumes of fuel, usually natural gas.

[16] It can be calculated that in ceramic plants known in the art the thermal consumption values are on average about 440 kcal/kg in the spray drying process, 90 kcal/kg in the drying process after the forming step, and 490 kcal/kg in the firing step. In this case, an average product is considered in which the slurry fed into the spray dryer has a percentage of inlet water equal to 35% and outlet water equal to 8%. In this regard, it is only mentioned that different inlet and outlet humidity levels affect the consumption of thermal energy. For example, an increase in water in the slurry entering the spray dryer or a decrease in the moisture content in the outgoing body formulation, equal to one percentage point, can lead to an increase of about 4% in thermal energy consumption.

[17] In addition, actual consumption may fluctuate, depending on the efficiency of the system, up to total values increased by 20%.

[18] Taking into consideration, for example, a production line of 10,000 m ² /day, for producing a product of 21 kg/m ² , it can be calculated that for spray drying it is necessary to consume 92,400,000 kcal/day: [19] dally thermal energy consumption = 440x21x10000 = 92.400.000 kcal/day

[20] As for water consumption, the use of spray dryers in production plants certainly involves high ecological cost.

[21] In fact, in the processes known in the art, the spray dryer must extract about 27% of the initial water content from the slurry. The extracted water is materially visible in the white plumes that come out of the factories and which testify to how it is substantially dispersed into the environment.

[22] It can be calculated that approximately 0.45 liters of water/kg of body formulation are emitted into the atmosphere, that is, considering approximately 21 kg of body formulation/m ² , this is equivalent to 9.45 liters of water/m ² . In a production line that produces 10,000 m ² /day, it can then be calculated that 94,500 liters of water/day are emitted, that is dispersed, and therefore 32,130,000 liters/year.

[23] It should also be considered that dust also comes out from the chimney of the spray dryer, in addition to combustion fumes and extracted water.

[24] Through the use of suitable filter means, such as bag filters, emission levels may be reduced, but hardly below 20 mg/Nm ³ .

[25] Although the emission value may appear to be very low, in reality, the enormous volumes of air involved, equal for example to about 140,000 Nm ³ /h in a 14,000-liter/h spray dryer, involve a considerable introduction into the atmosphere of powders with a high content of silica, therefore of particles, as is known, very dangerous for health.

[26] Approximately, for a 14.000 liters/h spray dryer, we can calculate: kq

140,000 x 20 x 10 ⁶ = about 2.8 — of dust h

[27] The powders emitted by the ceramics are mainly silicon, which effect in the lungs is known to cause both silicosis, TB and tumors, as also emerges from the study of the National Health Service entitled "Evaluation of exposure to free crystalline silica in some production sectors in Emilia Romagna, summary of the results/SSN - 2005”, in which, in particular, the high risks for workers in the ceramic tile production sector are highlighted.

[28] In addition to the workers inside the plants, it is important to consider the exposure of the population, and therefore the potential negative impacts on health, of the release of these harmful dust into the atmosphere.

[29] Finally, it is important to highlight how production plants that include spray dryers also emit high quantities of CO2.

[30] In practice, it can be considered, for example, that the Sassuolo area uses approximately 442,000,000 m ³ of gas, from which combustion 1.8 kg of CO2 are obtained per m ³ of methane. The rough calculation of CO2 emitted by the spray dryers is therefore about 790,000 tons/year, equal to about 2,300 tons per day.

[31] These are therefore substantial emissions, with a negative impact on the environment, that must not be disregarded.

[32] For example, patent application CN 110407587 discloses a process of dry and wet milling of materials suitable for producing ceramic tiles.

Disclosure

[33] The aim of the present invention is to solve the aforementioned problems, devising a method and a plant for preparing a material, in particular in powder or granular form, suitable for manufacturing ceramic tiles which minimizes consumption, in particular of thermal energy and water.

[34] Within this aim, a further object of the invention is to provide a method and a plant for preparing a material suitable for producing ceramic tiles, capable of minimizing the environmental impact, in particular with regard to the emission of dust and carbon dioxide.

[35] Another purpose of the invention is to provide a method and a plant for preparing a material suitable for producing ceramic tiles that are adapted to maximize energy savings.

[36] It is a still further purpose of the invention to provide a plant for preparing a material suitable for manufacturing ceramic tiles, with a smaller overall dimensions than the plants known in the art, having reliable operation, versatile use, and relatively inexpensive cost.

[37] The above objects are achieved, according to the present invention, by the method for preparing a material suitable for manufacturing ceramic tiles of claim 1 , as well as by the plant of claim 14.

[38] In practice, the method according to the invention makes it possible to prepare a material having a desired moisture content, preferably in the powder or granular state, therefore suitable for being formed by pressing and intended for manufacturing ceramic tiles by pressing and then firing. This material is made up of a number of different substances, according to a formulation or recipe known in the ceramic production sector.

[39] The method according to the invention therefore provides for preparing, according to a specific recipe, a batched quantity of solid raw materials, suitable for manufacturing ceramic tiles.

[40] In a known way, a recipe or formulation, also called "body formulation" for producing ceramic tiles, usually includes a fraction of so-called "plastic" raw materials, for example clays, and so-called "non-plastic" raw materials, for example inert and fluxes.

[41] The method then provides for wet milling or blunging at least a part of the recipe, using a wet milling or blunging apparatus known in the art, adding a certain percentage by weight of water, in order to obtain a material at the inlet, preferably a slurry, that is an aqueous suspension of particles of solid materials or in any case a "wet" material.

[42] This percentage by weight corresponds to an initial moisture content of the input material, which can be for example equal to, or included in a range of a few percentage points around 35%. [43] I he solid raw materials in aqueous suspension are also called "slip" in the specific sector of the production of ceramic tiles.

[44] According to an advantageous prerogative of the method, a moisture regulator assembly is then arranged, comprising a tank containing a plurality of bodies freely arranged inside the tank. In particular, the tank can be rotated according to a longitudinal axis and is associated with a feeding assembly for a controlled flow of an operating fluid, in particular air, to feed thermal energy to the tank to extract by evaporation an excess quantity of water from the input material.

[45] The method then provides for feeding the input material into the tank of the regulator assembly and for rotating the same tank around the longitudinal axis, to obtain an output material of the regulator assembly, having a desired moisture content.

[46] The aforementioned bodies can therefore perform a crushing and/or milling and/or stirring action of the substances placed inside the tank, when the tank is rotated.

[47] More precisely, the aforementioned regulator or stirrer assembly is a moisture regulator assembly of the fed aqueous suspension, which also comprises a feed assembly for an operating fluid, configured to exchange heat with the aqueous suspension inserted in the tank, and thus reduce its moisture content.

[48] In addition, the milling and/or stirring bodies are arranged free inside the tank, so as to be dragged in rotation by the rotational motion of the tank itself, to usefully stir and crush the solid raw material preferably in aqueous suspension, introduced into the tank. This crushing favors, in particular, not only a mixing action, but also an optimal heat exchange, in particular between the operating fluid and aqueous suspension, drying the latter, if required.

[49] It is important to note that the movement of the bodies inside the tank, dragged by the rotational motion of the tank itself, facilitates the escape of the interstitial water present inside the solid substances, fed into the tank.

[50] In practice, the method involves regulating, in particular correcting, the moisture content of the material entering the tank, by rotating the tank, then mixing by stirring and/or removing an excess amount of water by operating the assembly for feeding the operating fluid, preferably hot air, at a determined temperature, for example around or above 40° C.

[51] In particular, in the same step of regulating the moisture content of the input material, the method involves stirring, then homogenizing, and crushing the incoming material, rotating the tank around the longitudinal axis, thus obtaining a material coming out from the regulator assembly, preferably in powder or granular form, having a desired moisture content.

[52] The method can then provide for transferring the output material obtained from the regulator assembly to a granulator assembly, to granulate it and obtain a granular material suitable for producing ceramic tiles.

[53] The abovementioned tank is therefore loaded with bodies, for example balls, preferably of sintered alumina.

[54] The method can provide for extracting, or sieving, the output material coming out of the regulator assembly through filtering means, for example cyclones.

[55] In particular, the tank of the regulator assembly can provide extraction means, for example made by means of a perforated sector arranged at a section of the tank, associated with suction members, to separate the flow of operating fluid heavy with moisture from the output material, obtained by stirring and crushing.

[56] The ceramic body formulation or output material obtained comprises substantially the same batched quantity of solid materials initially introduced into the regulator assembly and a residual amount of water, i.e. a desired content preferably around 2 - 5%.

[57] According to a possible regulation alternative, in the stirring and milling step, in particular in regulating the moisture content, the method can therefore provide for the further step of regulating the moisture content of the input material, in particular in the slurry state, in order to obtain the desired content, by feeding the aforementioned controlled flow of operating fluid through the tank, in particular against the current, that is against the input material.

[58] The introduction of the operating fluid into the tank can be controlled by control means known in the art, associated with the aforementioned feed assembly, for example as a function of the initial moisture content and/or the humidity or quantity of excess water to be extracted.

[59] The method preferably provides that the aforementioned operating fluid is supplied by a heat recovery assembly, configured to recover the operating fluid produced at the outlet of a firing kiln for manufacturing ceramic tiles, set up for operation, and/or by an assembly of cogeneration arranged, in order to dry the input material, in particular the slurry or aqueous suspension, and to extract by evaporation an excess quantity of water, so as to obtain the body formulation or output material having the desired moisture content.

[60] In practice, the method can provide for separating the excess quantity of water from the input material, in particular from the slurry, by thermal separation means, through the same regulator assembly.

[61] The flow of operating fluid, preferably hot air, can pass through the regulator assembly, for example inside the tank and/or in a cavity made in a respective tank shell.

[62] Therefore, the regulator assembly preferably uses amounts of thermal energy made available through the heat recovery assembly from other steps of the tile production process, for example, and mainly, from the step of firing in the kiln.

[63] Preferably, the recovered thermal energy is in the form of hot air coming from the cooling areas of the firing kiln itself or from the flue gas outflow chimney.

[64] The method may provide, in order to thermally extract excess water, for using thermal recovery energy produced as an alternative, if, for example, the system does not have a tiring kiln, by a cogeneration assembly set up in the system. A cogeneration assembly is an electrical energy production system, comprising means such as turbines or endothermic engines, suitable for generating electrical energy, and for recovering the heat generated by them as exhaust gas and/or cooling air.

[65] According to a particular aspect, the method can provide, in addition or alternatively, to provide a device for feeding the thermal energy, necessary to extract the aforementioned amount of excess water, for example comprising a burner acting on the flow of operating fluid, in particular hot air, inserted for example in an independent pipe or in a pipe of the heat recovery assembly, in this case to make up for at least temporarily the possible lack of hot recovery air, due to production stops of the kiln or of the kilns connected thereto, or the temporary shutdown of the aforementioned cogeneration assembly.

[66] If necessary, according to a further particular aspect, the step of separating the excess quantity of water by thermal separation means can be preceded by an intermediate step, in which a part of the excess quantity of water to be extracted is separated, with the aid of a mechanical separation assembly. The mechanical separation carried out in this intermediate step, for example by a filter press or similar means, involves the reduction in the percentage of water in the slurry or initial aqueous suspension, and the obtainment of an intermediate material with an intermediate moisture content, but it may require still a following step, by the stirring assembly, of bringing the moisture content to the desired level. Furthermore, it must be considered that the water mechanically extracted in the aforementioned intermediate step is rich in water-soluble substances, in particular salts. Therefore, it is not always reusable directly in the process, but preferably requires decanting or other processing to eliminate or reduce the content of these substances. For example, if the salt content is greater than a certain threshold value, this extracted water is not reused, but is disposed of.

[67] The method may further include the step of shredding the body formulation with an intermediate moisture content using a shredding assembly.

[68] Furthermore, the method can comprise the further step of recovering at least part of the aforementioned excess amount of water, extracting it by condensation from the stirrer assembly, and of using it at least in part for the initial step of preparing the slurry and/or for the step of humidifying and re-granulating the body formulation.

[69] According to a prerogative of the invention, the regulator assembly includes a rotary tank, with continuous or discontinuous operation.

[70] According to a particular aspect, the method can advantageously provide for recovering, at least in part, preferably totally, by condensation, the excess quantity of water, possibly separated by the regulator assembly, by means of a water recovery assembly, and to reuse the condensate upstream of the process such as milling water in the apparatus for wet milling or tor blunging. By means of the water recovery assembly, a considerable part of the process water, for example estimated at about 60%, may be recovered in this way.

[71] The method thus permits to obtain preferably a powder of suitable particle size, avoiding the use, for example, of a pin mill or similar means.

[72] The method preferably provides for subsequently moisturizing the powder obtained to a suitable final moisture content, for example between 6% and 8%, and re-granulating it by means of the granulators known in the art.

[73] This step makes it possible to obtain a granular mixture suitable, due to its physical shape and moisture content, for loading known forming apparatuses, such as, for example, presses for forming ceramic tiles.

[74] Finally, the method may provide for storing the body formulation or granulated material in containment units, for example silos, to allow its subsequent use, according to the operating steps known in the ceramic tile production sector.

[75] According to a particular embodiment, the method can provide for the further step of feeding into the tank of the stirring assembly a further batched quantity of raw materials in powder obtained by dry milling, thus forming in this case a semiliquid mixture with a lower moisture content. In this case, the regulator assembly optimizes the energy required for mixing this semiliquid mixture. Moreover, in this case, the batched portion of raw materials, prepared in aqueous suspension, and the additional batched quantity pre-dry milled combine to constitute the desired formulation or recipe for the production of ceramic tiles.

[76] In this case, in particular, it may not be necessary, in the aforementioned moisture regulation step, to extract excess water, but to maintain the percentage of water already present or to add an additional quantity of water in a suitable phase, to obtain the desired moisture content for the formulation.

[77] In this case, moreover, the action of the regulator assembly is to mix and blend in an optimal way the "wet" portion, consisting of the substances introduced in aqueous suspension or in any case "wet", with the "dry" portion, consisting of pre-dry milled substances. In addition to this, the control of the overall moisture content of the introduced substances, made by the regulator assembly, permits to obtain the outlet a material having the desired moisture content, feeding any combination of dry and wet material.

[78] Basically, the method according to the invention has the advantage of avoiding the use of spray dryers, for the extraction of water from the slurry. This results in significant savings in the consumption of energy resources and water, as well as in a considerable reduction in the environmental impact of ceramic production.

[79] In practice, the method permits, therefore, to reduce the emission of dust with a high silica content, which is extremely harmful, as is known, for the body, and of CO2.

[80] The plant according to the invention, suitable for implementing the aforementioned method, comprises at least an apparatus for wet milling or for blunging a mixture of a specific batched quantity of solid raw materials and a percentage by weight of water, according to an initial moisture content, for producing an input material, preferably a slurry or aqueous suspension, a stirrer or regulator assembly, connected to the apparatus for wet milling or for blunging and configured to stir and crush solids in suspension in the input material. The regulator assembly comprises a tank containing a plurality of grinding and/or stirring bodies, for example balls, preferably of sintered alumina, and operable around a longitudinal axis, preferably substantially horizontal, to obtain from the input material an outlet material with a desired moisture content.

[81] The stirring assembly includes a feeding assembly for a controlled flow of an operating fluid, suitable for exchanging heat with the input material inserted into the tank, to extract excess moisture therefrom.

[82] The tank of the regulator assembly is configured to be supplied with the operating fluid for extracting by evaporation an excess amount of water from the input material and thus obtain an output material, preferably in powder form, having the desired moisture content.

[83] The plant may include control means to control the controlled flow of operating fluid.

[84] The plant may also include a granulator assembly configured to receive the aforementioned body formulation from the stirring assembly, in order to obtain a granular material suitable for ceramic production.

[85] The assembly for supplying operating fluid may comprise a device for producing the thermal energy used to extract the amount of excess water, for example comprising a burner acting on the flow of operating fluid, in particular hot air.

[86] The plant can comprise at least one kiln for firing the body formulation, configured to produce the outlet heating operating fluid, and/or a cogeneration assembly for producing electricity, from which, preferably, thermal energy may be recovered, and a heat recovery assembly, configured to recover the outlet operating fluid produced in the firing kiln and, alternatively or in addition, in the cogeneration assembly, so as to at least partially feed the stirring assembly.

[87] Said tank preferably comprises a casing, for example cylindrical, which can be rotated around said longitudinal axis, preferably horizontal.

[88] Advantageously, the regulator assembly according to the invention can allow the regulation of the moisture of the input material, in particular of the slurry or aqueous suspension, in a dynamic way, avoiding, thanks to the action of the bodies inside the tank, the aggregation of the material and therefore, the need for further treatments for its reduction to fine dust, suitable for subsequent regranulation.

[89] A further advantage is that the dynamic effect of the grinding bodies carries out a further grinding and/or, preferably, the crushing of the substances fed into the regulator assembly according to the invention. Therefore, this allows to increase the granulometry of the input material, in particular of the slurry coming out of the wet milling or blunging apparatus. Consequently, this apparatus can produce a greater quantity of slurry for the same energy consumption.

[90] Said method, according to the particular aspect, also permits to exploit considerable quantities of recovered thermal energy, at relatively low temperatures.

[91] Said particular aspect, for regulating the moisture of the input material, in particular of the slurry, also exploits the effect of the dragging motion operated by the regulator assembly on the material itself, in particular on the slurry. In fact, thanks to this motion, the material to be dried can have a higher relative speed in countercurrent, relative to the operating fluid, thus optimizing the heat exchange.

[92] At the same time, the heating of the grinding and/or stirring bodies and of the input material, in particular the slurry, due to the preferably counter-current flow of operating fluid, according to the same particular aspect, produces the adhesion of the same material to the grinding bodies and the subsequent detachment, due to the mechanical action of the same bodies, which continually collide inside the shell.

[93] The input material fed is continuously subjected, inside the regulator assembly, to the crushing action of the grinding bodies, so as to be reduced to the desired particle size.

[94] At the same time the action of the grinding bodies to which the solid material contained in the tank is continuously subjected determines the elimination of the evaporative boundary layer that usually is created between the material to be dried and the operating drying fluid, thus facilitating the process of drying.

[95] In addition, the action of the grinding bodies also causes the interstitial water to escape, thus making it possible for the operating fluid to interact with the water, facilitating its evaporation.

[96] The plant can also comprise mechanical separation means, functionally interposed between the apparatus for wet milling or for blunging and the stirring regulator assembly, to extract part of the aforementioned amount of excess water from the input material, obtaining an intermediate material having an intermediate moisture content.

[97] Preferably, the aforementioned mechanical separation means comprise a filter press or similar mechanical extraction means.

[98] The plant may further comprise a shredding unit for the separate intermediate body formulation, for example a material chipper or a rotary harrow teeth or similar means.

[99] The system can usefully include at least one water recovery assembly, configured to recover the aforementioned excess amount of water, in particular extracted from the regulator assembly.

[100] Preferably, the water recovery assembly is configured to recover, by condensation, the excess quantity of water or part of it, which can be removed by means of the regulator assembly.

[101] The water recovery assembly can additionally or alternatively feed the granulator assembly.

[102] The aforementioned plant is therefore more compact and relatively less expensive than a plant known in the art for manufacturing ceramic tiles, in which spray dryers are used.

[103] In addition, the system according to the invention minimizes energy expenditure, in particular the consumption of thermal energy, and the environmental impact, thus preserving the environment and the health of the population.

[104] In fact, a considerable amount of the process water can be recycled, instead of being dispersed in the environment, and the emission of dust which, on the other hand, is released into the environment in high quantities, even after filtering, from the chimneys of the spray dryers in the plants known in the art, can be reduced.

Description of drawings

[105] The details of the invention will become more evident from the detailed description of a preferred embodiment of the method for preparing a granular body formulation for manufacturing ceramic tiles, illustrated as an indication in the attached drawing, in which: Figures 1 - 3 show respectively a flow chart, representative of the operating steps provided for by the method according to the invention, in different embodiments;

Figure 4 schematically shows a plant for manufacturing ceramic tiles according to the invention;

Figure 5 schematically shows a further embodiment of the plant for manufacturing ceramic tiles according to the invention;

Figure 6 shows a schematic view of a regulator assembly used in the plant according to the invention.

Description of embodiments of the invention

[106] With particular reference to Figures 1 , 4 and 6, the method according to the invention can be implemented, for example, by a plant 10 for manufacturing ceramic tiles comprising at least an assembly 1 for batching raw materials, at least an apparatus 2 for the wet milling of raw materials or for blunging, for producing an input material S, preferably an aqueous suspension, usually called "slurry" or "slip", a moisture regulator or stirrer 3 of the input material S or of the slurry, to obtain a blended output material P, preferably in powder or granular form, having a desired moisture content.

[107] The plant also preferably comprises a heat recovery assembly 4 of thermal energy, preferably coming from a firing kiln 40 of the body formulation obtained and formed or, in addition or alternatively, from a cogeneration assembly 41 possibly provided.

[108] The batching assembly 1 , known in the art, is configured to batch, by means of a preferably continuous weighing system, the different raw materials of a given recipe for manufacturing ceramic tiles. The batching assembly 1 therefore permits to obtain a batched quantity of predetermined raw materials.

[109] The apparatus 2 for wet milling or for blunging, also known in the art, can be made up for example of a ball mill, configured to add to the batched quantity of batched raw materials or part of them a certain percentage by weight of water, so as to obtain, following milling, the incoming material, preferably slurry. This percentage by weight can be equal to 35%, or it can be included in a suitable range, for example of a few percentage points, around this value. A high percentage of water in the slurry allows for easier wet milling. This is convenient, in particular, if sufficient thermal energy is available for reducing afterwards, in the following steps described below, the moisture content of the slurry to the desired value for the desired body formulation. In cases in which, on the other hand, the thermal energy available to subsequently reduce the moisture content is relatively low, a lower water content in the slurry may then be introduced, for example around 30%, possibly adding deflocculating agents.

[110] The term "water" is used hereinafter to also mean an aqueous solution or mixture to which additives are added, to adjust certain properties of the solution or mixture itself, or of the mixture, preferably in powder, to be obtained.

[111] The apparatus 2 for wet milling or for blunging can be associated downstream with a sieving and iron removal assembly 21 of a known type, to treat the input material S in a manner suitable for the following steps.

[112] The regulator assembly 3, arranged downstream of the apparatus 2 for wet milling or blunging and possibly of the assembly 21 , is configured to receive at least part of the recipe directly in the form of slurry, i.e. substances of the recipe in aqueous suspension, therefore in liquid form, with the amount of water deriving from wet milling or blunging or, as described below, with a reduced amount of water compared to that of wet milling, following an intermediate process of mechanical separation. In this case, the intermediate material obtained, with a reduced amount of water, can possibly be shredded, as described below, before being introduced into the regulator assembly (see Figure 5).

[113] Alternatively, according to an advantageous embodiment, the regulator assembly 3 can be partially fed with slurry in liquid form coming from wet milling or from blunging and partially with the other substances of the same recipe, in powder form, produced in a known way by dry milling.

[114] The input material S inserted altogether into the tank 30 constitutes the specific recipe for the type of ceramic tiles to be obtained.

[115] The regulator assembly 3 according to the invention primarily performs a stirring function, therefore mixing the liquid mixture, in particular the slurry, fed thereto.

[116] The regulator assembly 3 then performs a crushing or grinding function, thanks to the action o† crushing or grinding bodies C.

[117] Finally, the regulator assembly 3 performs a regulating function of the moisture content present in the mixture of substances or fed input material S. Preferably, it can provide for adjusting this parameter from an initial input content to a desired final moisture content, in particular by drying the fed mixture.

[118] More precisely, the regulator assembly 3 comprises a particular tank 30 which internally defines a chamber containing inside it a plurality of crushing or grinding bodies C, for example balls, preferably of sintered alumina (see Figure 6).

[119] The tank that forms the regulator assembly 3 according to the invention can be rotated, advantageously and preferably according to a horizontal axis, and is configured to be crossed by a flow of an operating fluid T.

[120] For this purpose, the regulator assembly 3 comprises a supply circuit for a controlled flow of operating fluid T, preferably hot air. This flow of operating fluid T is introduced in a controlled manner by a feeding assembly, in order to extract, by removing heat, an excess quantity of water from the input material S, preferably in aqueous suspension, inserted in the tank 30.

[121] The operating fluid T, preferably hot air, is preferably made available by the heat recovery assembly 4, at a temperature preferably higher than 35-40 °C, to regulate the moisture content of the input material S, for example slurry, particularly in order to dry it properly.

[122] Alternatively, the aforementioned power supply circuit can be associated with an autonomous thermal energy production device, for example made by a burner, acting on the same circuit.

[123] The rotation of the tank 30 produces the effect of dragging the crushing or grinding bodies C into motion, together with the input material S inserted inside the chamber. In practice, the rotation of the tank 30 with the grinding bodies C has the effect of stirring, in particular mixing, the substances S inserted in aqueous solution or slurry.

[124] The dragging of the grinding bodies C can also have the advantageous effect of further milling the materials or formulation of substances S introduced into the tank 30.

[125] Furthermore, with regard to the aforementioned function of regulating the moisture content, when the operating fluid T is introduced into the tank 30 of the regulator assembly 3, the contact with it can cause the adhesion of the input material S to the bodies C and to the inner wall of the chamber defined inside the tank 30 itself. Then, the crushing or grinding bodies C exert an action on the input material S and therefore it separates from the bodies C themselves and from the internal wall of the chamber to be then extracted from the regulator assembly 3.

[126] The rotatory motion of the tank 30 then has the effect of dynamically moving the slurry or substances in aqueous solution S inserted inside the chamber towards the operating fluid I , Increasing the relative speed between the input material S or the slurry and the operating fluid T itself, therefore the effectiveness of the heat exchange within the regulatory function of the regulator assembly 3.

[127] Thanks to this dynamic action, the interaction between the input material S, in particular the slurry, driven in motion by the rotation of the tank, and the flow of operating fluid T does not present "shady areas", but involves every part of the product.

[128] Furthermore, again thanks to the aforementioned dragging motion, the grinding bodies C exert a continuous crushing action on the product, thus tending to eliminate an evaporative boundary layer on the particles of the latter and increasing the thermal interaction with a drying effect.

[129] The same crushing action causes the interstitial water to escape, thus making possible the direct interaction of the water with the operating fluid T and thus facilitating its evaporation.

[130] Furthermore, it should be noted that the motion in which the grinding bodies C are dragged produces itself a quantity of heat, useful for creating or contributing to the regulation of the moisture of the product inserted inside the chamber.

[131] Furthermore, the mechanical action of the grinding bodies C permits to obtain a perfectly amalgamated ceramic body formulation or output material P, even if the tank 30 is partially fed with product in liquid form, coming from wet milling or blunging, and partially with product in powder form, coming from dry milling, as described in detail below.

[132] The regulator assembly 3, in particular, can form a first casing, preferably cylindrical, which internally defines the aforementioned containment chamber of the slurry or of the substances S to be treated.

[133] The regulator assembly 3 also preferably comprises a second casing, also preferably cylindrical, arranged externally to the first casing, so as to define with it a cavity, configured for the passage of the operating fluid. In this case it is possible to perform, by feeding the operating fluid T inside the cavity, the heating, substantially by conduction, of the first internal casing and, therefore, of the chamber and its contents.

[134] Preferably, the regulator assembly 3 comprises valve means, configured to maintain the tank chamber in an empty or half-empty condition. In this case, a condenser device can be further provided, for the recovery of evaporated water.

[135] The regulator assembly 3 can further comprise filtering means 31 , for example a bag filter like or of a cyclone-like, for sucking the operating fluid T and recovering any residual dust coming out of the regulator assembly 3.

[136] The tank 30 of the regulator assembly 3 can provide for extraction means, for example made by means of a perforated sector F arranged at a section of the tank 30 itself, associated with suction members, to separate the flow of operating fluid T heavy with moisture from the output material P, obtained by stirring and crushing (see Figure 6). [13 ] I he heat recovery assembly 4 comprises means for conveying a flow of operating heating fluid T coming out of the firing kiln 40 and/or the cogeneration assembly 41 which may be present in the system.

[138] The regulator assembly 3 can be advantageously associated with the aforementioned heat recovery unit 4, so as to receive, at least in part, the thermal energy accumulated in the cooling air leaving the firing kiln 40 or by other assemblies, as described below, like operating fluid T.

[139] The firing kiln 40 is preferably of the known type, with rollers.

[140] In particular, thanks to the aforementioned heat recovery assembly 4 the thermal energy present in the cooling air of a firing kiln may be recovered, which, in known systems, is instead often expelled into the atmosphere.

[141] The heat recovery unit 4 can fully recover from the firing kiln 40 any thermal energy required by the process according to the invention.

[142] For prudential purposes, however, it is also possible in this case to associate an auxiliary thermal energy production device 42 to the regulator assembly 3, to meet a possible additional request or to serve in the event of failure or incomplete recovery from the firing kiln 40.

[143] The system 10 can also usefully comprise a water recovery assembly 5 that can be associated with a flow of air leaving the regulator assembly 3, configured to extract therefrom, by means of a condensing device 51 , a respective share of water.

[144] The water recovery assembly 5 can be associated with the regulator assembly 3, to recover the aforementioned amount of excess water or at least part of it, for reuse, for example, in the apparatus 2 for wet milling or blunging.

[145] The plant 10 can also comprise a humidifier/granulating unit 6, to bring the material P coming out from the regulator assembly 3, with the desired moisture content, to a physical form suitable for forming in known apparatuses, such as presses.

[146] For this forming, in fact, particular physical characteristics are required, for example the flowability of the powders and moisture.

[147] The plant 10 can also include, in the section dedicated to preparation, containment means known in the art, such as silos, in which the pulverized and granulated material can be stored until it is used in the production process.

[148] The plant 10 can further comprise a dust recovery assembly 7, configured to convey the dust recovered from the filtering means 31 or from other parts of the plant, for example from the recovery of broken and unfired tiles, from storage silos, from presses, inserting them in suitable percentages for subsequent firing during the step of mixing the slurry.

[149] The method for preparing a material suitable for the production of ceramic tiles, according to the invention, and the operation of the plant that implements it are easily understood from the above description.

[150] The method according to the invention provides to prepare the apparatus 2 for wet milling or for blunging raw materials suitable for preparing a granular mixture, as well as the regulator assembly 3. Furthermore, the kiln 40 for firing ceramic products is preferably arranged for operation. Alternatively, the cogeneration assembly 41 and/or the thermal energy production device directly associated with the humidity regulator assembly 3 is preferably arranged.

[151] In a first step of preparation, the batched quantity of solid raw materials suitable for producing ceramic tiles is prepared according to a specific recipe.

[152] At least part of the batched quantity of raw materials with the determined percentage by weight of water is then mixed and milled or blunged, by means of the apparatus 2 for wet milling or for blunging, so as to obtain the input material S, in particular the ground slurry or "slip", therefore the formulation in aqueous suspension.

[153] Subsequently, the moisture content of the incoming material S is regulated by means of the regulating assembly 3 according to the invention, preferably using the operating fluid T, in particular hot air, preferably recovered by means of the heat recovery assembly 4 coming out of the firing kiln 40 prepared, preferably coming from the cooling zones of the firing kiln 40. In addition, the stirring assembly 3 can be provided to be powered by the thermal energy production device 42, for example to compensate for the lack or variations in availability of thermal energy recovered from the kiln 40 and/or from the cogeneration assembly 41 , if present.

[154] The method can provide for operating, by means of the aforementioned water recovery assembly 5, the recovery of this amount of excess water, extracting it, by condensation, during the drying process.

[155] Furthermore, it is possible to suck the operating fluid T, in particular air, at the outlet of the regulator assembly 3, and to filter it through the filtering means 31 , to recover any residual dust.

[156] It is further possible to activate the dust recovery assembly 7, configured to convey the dust recovered from the aforementioned filtering means 31 , as well as from other steps of the plant, for example from the recovery of broken and unfired tiles, from storage silos, from presses, in percentages suitable for subsequent firing, by inserting them during the step of mixing the slip.

[157] The method can preferably provide for pulverizing, humidifying and granulating the dried body formulation, that is, the material P leaving from the regulator assembly 3, through the humidifier/granulating assembly 6. In particular, it is possible to reuse the aforementioned excess amount of water, once recovered, to wet the dried and pulverized body formulation, in the granulation step. [158] In this way, a granular body formulation suitable for subsequent forming can be obtained.

[159] Finally, the method can provide for the storage of the granulated material in containment units, silos for example, to allow its subsequent use.

[160] According to an alternative solution, it is possible to provide that the method is implemented by a plant for the production of a material for the production of ceramic tiles, comprising, in addition or as an alternative to a firing kiln 40, a cogeneration assembly 41 , configured to produce and recover thermal energy.

[161] In this case, it is possible to provide that the heat recovery assembly 4 is powered by the thermal energy produced by the cogeneration assembly 41 , to produce the drying that generates the desired output material of the regulator assembly 3.

[162] For the rest, as far as applicable, the method does not differ from that described above.

[163] The plant that can implement the method according to this alternative solution can produce the dried material, advantageously even in the absence of a firing kiln 40 in operation.

[164] According to a further embodiment illustrated in Figures 2 and 5, the plant 10', otherwise similar to that described above, can further comprise a mechanical separation assembly 8 of at least part of the excess water, interposed between the apparatus 2 for wet milling or blunging and the regulator assembly 3.

[165] The mechanical separation assembly 8 is instead configured to mechanically separate the solid part of the slurry from an excess amount of water, therefore coming out of the wet milling or blunging apparatus 2.

[166] The mechanical separation assembly 8 can be made by means of a known type filter press or by an equivalent apparatus.

[167] The mechanical separation assembly 8 can be configured to reduce the slurry to a body formulation in which the share by weight of water is preferably reduced to around 18%.

[168] It should be noted that the part of water mechanically extracted from the slurry can carry salts and other water-soluble substances. In the event that the excess water was extracted by evaporation, these substances would remain in the body formulation and would subsequently be ceramic coated in the firing process.

[169] To reuse the part of excess water mechanically extracted from the slurry, it is therefore preferable to perform a treatment by flocculation and/or decantation, as well as appropriately disposing of the residual substances.

[170] The aforementioned water recovery assembly 5 can thus also be associated with the mechanical separation assembly 8, for the recovery of a further quantity of excess water, separated from the slurry.

[171] The plant 10' can further comprise a shredding assembly 9, interposed between the mechanical separation assembly 8, if provided, and the regulator assembly 3 (see Figure 3). For example, the shredding assembly 9 can be made by means of a material chipper or a rotary harrow teeth or other known apparatuses, suitable for the purpose.

[172] The shredding assembly 9 reduces the intermediate material resulting from the mechanical separation of part of the excess water to a size suitable for introduction into the regulator assembly 3 according to the invention.

[173] As regards the implementation of the method according to the invention in this embodiment, with reference to the further embodiment described for the plant 10', in addition to what has been described above, it is possible to provide that between the mixing of the slurry and the relative drying by means of the regulating assembly 3, a preliminary extraction step of a part of the excess water is interposed, for example by means of the aforementioned mechanical extraction assembly 8. After the partial extraction of the excess water, by means of the mechanical extraction assembly 8, it is possible to provide that the mixture thus obtained is reduced to a smaller particle size, by means of the shredding assembly 9.

[174] The method can advantageously provide for recovering, at least in part, the part of the excess quantity of water separated mechanically, by means of the water recovery assembly 5, and reusing it, for example, for mixing a new slurry.

[175] Alternatively, as illustrated in Figure 3, it is possible to provide for feeding the regulator assembly 3 with a mixture in semi-liquid form, resulting from the slurry obtained from the wet milling or from the blunging of a portion of the formulation, made by a wet milling or blunging apparatus 2, and from a material in powder form, produced by a dry milling apparatus. In this case, the rolling of the bodies C of the regulator assembly 3 produces a dynamic effect which also allows the dry product and the "wet" product to be mixed in an optimal way, in order to obtain a homogeneous mixture.

[176] It should be noted that the mixing of the two portions of the mixture, dry and wet, in the absence of the regulator assembly according to the invention, could be particularly difficult. However, thanks to the primary dynamic action of the bodies C driven in rotation, the regulator assembly 3 can perform its own dynamic action on the mixture, obtaining an optimal mixing with minimum energy consumption.

[177] Advantageously, in this case the overall amount of moisture introduced into the mixture to be blended is less, so as to more easily obtain the desired final moisture content for the final mixture, intended as the final material obtained.

[178] In this case it is possible to provide that the moisture content of the mixture introduced into the tank is close to or substantially equal to the desired moisture content. Consequently, the flow of fluid T operating in the tank 30 can be correspondingly modulated, so as to further reduce or maintain this moisture content. In the latter case, when it is not necessary to reduce the moisture content inside the tank 30, an additional amount of water can possibly be added, preferably only in the granulation step.

[179] The method according to the invention therefore achieves the aim of reducing heat consumption and the environmental impact of the process of production of ceramic tiles.

[180] The method for preparing a granular material for manufacturing ceramic tiles according to the present invention therefore achieves the aim of minimizing, in particular, the consumption of thermal energy and water, thus maximizing energy savings.

[181] Furthermore, the method according to the invention and the plant that implements it are able to minimize the environmental impact, in particular by considerably reducing the emissions of dust and carbon dioxide.

[182] The system described by way of example is susceptible of numerous modifications and variations according to the different needs.

[183] In the practical embodiment of the invention, the used materials, as well as the shape and the dimensions, may be modified depending on needs.

[184] Should the technical features mentioned in any claim be followed by reference signs, such reference signs were included strictly with the aim of enhancing the understanding of the claims and hence they shall not be deemed restrictive in any manner whatsoever on the scope of each element identified for exemplifying purposes by such reference signs.