Spray dryer for producing atomized ceramic powder from aqueous suspension of ceramic material

Abstract

A spray dryer (1) comprising: a body (2) defining an atomizing chamber (3); a supply system (5) for supplying an aqueous suspension of ceramic material into the atomizing chamber (3), the supply system comprising at least one injection unit (7) for injecting the aqueous suspension of material; a heating system (6) for generating a hot gas flow (F) having a temperature of at least about 400 DEG C, in particular in the range of from about 500 DEG C to about 600 DEG C, using at least one electric heater (18); and a distribution device (12) for distributing the hot gas flow (F) into the atomizing chamber (3) such that the hot gas flow impinges on the sprayed aqueous suspension of ceramic material, thereby drying the solid ceramic material contained therein and producing an atomized ceramic powder (CPA).

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This patent application claims the priority of Italian Patent Application No. 102022000016980 filed on August 8, 2022, the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] The invention relates to the field of manufacturing ceramic products such as tiles, ceramic plates, tableware, toilets, etc. In particular, the invention is applicable to the field of processing aqueous suspensions of ceramic materials (also called barbotine) to obtain atomized ceramic powders. Background Art

[0004] In the field of producing ceramic articles, it is known to produce at least part of an atomized ceramic powder using a spray dryer designed to produce a granular material having suitable particle size characteristics and residual humidity that make it suitable for forming ceramic articles, in particular substantially flat ceramic articles, such as tiles and ceramic plates. The known spray dryers generally comprise a body defining an atomization chamber, in which a treatment of the above-mentioned aqueous suspension of ceramic material (the so-called decorative slip) is carried out to obtain an atomized ceramic powder, which is then sieved and stored in special storage silos, from which it is taken out for use after an aging period that allows the humidity and temperature values ​​to be evenly distributed between the particles of this atomized ceramic powder.

[0005] In more detail, the spray dryer comprises: a supply system configured to supply a jet of a ceramic material aqueous suspension under high pressure into an atomizing chamber, usually via a plurality of nozzles; a heating assembly, which is usually composed of a natural gas, LPG or liquid fuel burner, to provide heat and heat the air, thereby generating a hot air flow with a temperature in the range of about 500°C to 600°C; and a hot air distributor, which is placed at the top of the atomizing chamber and is configured to receive the hot air flow from the heating assembly and distribute the hot air flow into the atomizing chamber according to certain paths, for example, by causing the hot air to move in a vortex motion, so that the ceramic material aqueous suspension ejected from the nozzle and the appropriately distributed hot air flow meet and form atomized ceramic powder and exhaust fumes, which will be discharged to the atmosphere via an exhaust chimney after appropriate filtering and / or reduction, for example, using a cyclone separator, a bag filter scrubber, etc. In contrast, the atomized ceramic powder, once dried, falls downward and is discharged toward a subsequent processing station via an exhaust belt.

[0006] Although these spray dryers offer excellent performance, they also have some disadvantages, which are mainly environmental and energy related.

[0007] In the system for producing ceramic products, the spray dryer is actually one of the most critical machines in terms of environment and energy usage along with the furnace, because it is the machine that requires the most input energy and is the main cause of producing most of the carbon dioxide produced in the entire ceramic product production system, especially about 30% of the total carbon dioxide produced by the ceramic product manufacturing system.

[0008] Problems related to carbon dioxide emissions are combined with more recent problems related to the increasing difficulty in obtaining raw materials such as fossil fuels.

[0009] The object of the present invention is to provide a spray dryer which can at least partially overcome the disadvantages of the prior art and at the same time ensure a performance similar to that of known spray dryers. Summary of the invention

[0010] According to the present invention, there is provided a spray dryer for producing atomized ceramic powders from an aqueous suspension of ceramic material according to what is claimed in the accompanying independent claim and preferably in any claim directly or indirectly dependent on the independent claim.

[0011] The claims describe preferred embodiments of the invention which constitute an integral part of the present description. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The invention is described below with reference to the accompanying drawings showing some non-limiting embodiments of the invention, in which:

[0013] - Figure 1 is a schematic perspective view of a spray dryer according to a first embodiment of the present invention;

[0014] - Figure 2 is a schematic perspective view of a spray dryer according to an additional embodiment of the present invention;

[0015] - Figure 3 yes Figure 1 A schematic side view of a spray dryer of the type shown;

[0016] - Figure 3A is a schematic side view of a spray dryer according to an additional embodiment of the present invention; and

[0017] - Figure 4 , Figure 4A , Figure 5 and Figure 6 are schematic diagrams of three different possible electric heater arrangements. DETAILED DESCRIPTION

[0018] In the drawings, reference numeral 1 denotes as a whole a spray dryer for producing an atomized ceramic powder CPA from an aqueous suspension of ceramic material, also referred to in the art as decorative slip.

[0019] Specifically, advantageously but not limitingly, such a ceramic material aqueous suspension comprises water in an amount ranging between about 30% and about 40% by weight (particularly, about 33%; more particularly, about 32%) and the remainder (particularly, at least about 67% by weight) of solid ceramic material. Advantageously but not limitingly, the solid ceramic material comprises clay, kaolin, feldspar, quartz sand and / or a combination thereof (particularly, consisting of clay, kaolin, feldspar, quartz sand and / or a combination thereof). More advantageously but not limitingly, such a ceramic material aqueous suspension has a density ranging from about 1600 g / l to about 1750 g / l and a density ranging from about 5.0×10 -6 m 2 / s to about 3.0×10 -5 m 2 / s different kinematic viscosities.

[0020] Special reference Figures 1 to 3 Advantageously, the spray dryer 1 comprises a body 2 delimiting an atomization chamber 3 and comprising at least one discharge outlet 4 configured to allow atomized ceramic powder CPA to leave the atomization chamber 3, advantageously but without imposing limitation, having a water content that may vary from about 4% to about 7%, in particular equal to about 5%. Advantageously, but without imposing limitation, the body 2 of the spray dryer 1 has a substantially vertical axis of symmetry Z.

[0021] Advantageously (again with particular reference to Figures 1 to 3 ), the spray dryer 1 also includes a supply system 5 (in Figure 3 ), the supply system is configured to supply the above-mentioned ceramic material water suspension into the atomization chamber 3 after appropriately spraying the above-mentioned ceramic material water suspension; and a heating system 6, the heating system is configured to generate a hot air flow F with a temperature of at least about 400°C (in particular, in the range between about 500°C and about 600°C) and send the hot air flow F to the inside of the atomization chamber 3, so that the hot air flow F encounters the sprayed ceramic material water suspension, thereby drying the solid ceramic material contained therein and producing an atomized ceramic powder CPA.

[0022] In particular (advantageously but not restrictively), the supply system 5 includes at least one injection unit 7, which is advantageously arranged inside the atomization chamber 3 and is configured to spray the ceramic material aqueous suspension and send the sprayed ceramic material aqueous suspension into the atomization chamber 3 so as to form a series of very fine droplets of the ceramic material aqueous suspension.

[0023] According to some advantageous but non-limiting embodiments, Figures 1 to 3 In the embodiment shown, the spray unit 7 comprises a plurality of nozzles 8 (particularly, consists of a plurality of nozzles 8), each of which is configured to send a jet of the ceramic material aqueous suspension into the atomization chamber 3 (e.g. Figure 3 Schematically shown), advantageously but not limitatively at a speed of at least 15 m / s (in particular, at a speed that can vary from at least about 15 m / s to at least about 50 m / s; more specifically, from at least about 20 m / s to at least about 40 m / s) and / or at an inlet pressure that can vary between about 15 bar and about 30 bar, so as to spray the ceramic material aqueous suspension and introduce a plurality of very fine droplets of the ceramic material aqueous suspension into the atomization chamber 3.

[0024] According to some advantageous but non-limiting embodiments (e.g. Figure 3 ), the spray unit 7 comprises a plurality of nozzles 8 arranged along a substantially annular crown (in particular, substantially circular), the center of which is located on the symmetry axis Z of the body 2. In other words, advantageously but not limitingly, the spray unit 7 comprises a plurality of nozzles 8 arranged along a substantially circular closed line. More specifically, according to some advantageous but non-limiting embodiments (such as Figure 3 In the embodiment shown), these nozzles 8 are arranged on a circular fixed support 9 which is arranged centrally with respect to the axis of symmetry Z and is preferably, but not necessarily, made of stainless steel.

[0025] According to other advantageous but non-limiting embodiments (e.g., Figure 3A), the nozzles 8 are arranged on linear supports 33, also preferably but not necessarily made of stainless steel (including said nozzles), connected so as to be suspended in an equidistantly spaced manner on the inner wall of the body 2. More advantageously but not limitingly, in this case, these linear supports 33 are also arranged along a substantially annular crown (but more advantageously a circular crown), the center of which is located on the symmetry axis Z. According to some advantageous but non-limiting variants of this embodiment (i.e. variants involving the embodiment in which the nozzles 8 are arranged on linear supports 33), each of these linear supports 33 is rotatably connected to the inner wall of the body 2 so as to be able to rotate on its own, in particular around an axis extending along the main extension direction of each linear support 33 (more specifically around an axis substantially orthogonal to the symmetry axis Z; more specifically around an axis extending in a radial direction relative to the body 2). This makes it possible to adjust the emission direction of the jet of the aqueous ceramic material suspension emitted by each nozzle 8, for example according to the type of the aqueous ceramic material suspension.

[0026] It will be appreciated that the substantially annular crown along which the nozzles 8 are arranged may be substantially elliptical or square or irregular, as long as it is configured to be centered relative to the axis Z of symmetry.

[0027] More advantageously, but not limitingly, the nozzles 8 of the spraying unit 7 are oriented such that the respective jet of the aqueous ceramic material suspension is substantially vertical and directed upwards, in particular towards the upper part of the atomization chamber 3 .

[0028] Advantageously, but not limitingly, the supply system 5 comprises at least one collecting unit 10 (e.g. a basin or a tank), a pumping assembly 11, advantageously formed by at least one piston pump, configured to extract the aqueous ceramic material suspension from the collecting unit 10 and pump it to the injection unit 7 at a pressure that can vary from about 15 bar to about 30 bar (see Figure 3 ).

[0029] According to other advantageous but non-limiting embodiments that are not shown, the supply system 5 also comprises a filter interposed between the pumping assembly 11 and the spraying unit 7 , in order to filter the aqueous ceramic material suspension before it is introduced into the atomization chamber 3 .

[0030] Advantageously, the spray dryer 1 (more specifically, the above-mentioned heating system 6) further comprises a distribution device 12, which is configured to distribute the hot air flow F into the atomization chamber 3 so that it impacts the sprayed ceramic material aqueous suspension, thereby drying the solid ceramic material contained therein and generating an atomized ceramic powder CPA.

[0031] According to some advantageous but non-limiting embodiments, the distribution device 12 comprises at least one annular guide duct 13 (in particular, consists of at least one annular guide duct 13), which is configured to impart a vortex movement in the form of a spiral around the axis of symmetry Z to the hot gas flow F, so as to enable the ceramic material aqueous suspension to be properly dehydrated (the ceramic material aqueous suspension encounters the hot gas flow F, that is, is impacted by the hot gas flow F during use) and obtain an atomized ceramic powder CPA with specific characteristics in terms of particle size and / or humidity.

[0032] More advantageously, but not limitingly, the distribution device 12 comprises a plurality of openings (not visible in the attached figures) for sending a hot gas flow F towards the atomization chamber 3; a plurality of spiral ducts (centered with respect to the axis of symmetry Z) for guiding the hot gas flow F towards the plurality of openings and a plurality of deflectors (also not visible in the attached figures).

[0033] According to an alternative, advantageous but non-limiting embodiment, for example Figure 3A In the embodiment shown, the spray dryer 1 (in particular, the distribution device 12) comprises a suction system 30, which is advantageously fluidly connected to the atomization chamber 3, comprises at least one aspirator 31, and is configured to distribute the hot gas flow F into the atomization chamber 3. Specifically, advantageously but not limitingly, the suction system 30 is configured to pressurize the hot gas flow F supplied by the heating system 6 and impart a vortex motion in the form of a spiral around the symmetry axis Z to the hot gas flow F, so as to enable the ceramic material aqueous suspension to be properly dehydrated (the ceramic material aqueous suspension encounters the hot gas flow F, that is, is hit by the hot gas flow F in use) and obtain an atomized ceramic powder CPA having characteristics in terms of particle size and / or moisture. Advantageously but not limitingly, the discharge outlet 4 through which the atomized ceramic powder CPA leaves the atomization chamber 3 comprises a discharge valve (in particular, consists of a discharge valve), which is known and is not further described or shown here, and is configured to be able to control the discharge of the atomized ceramic powder CPA. In addition, according to some advantageous but non-limiting embodiments (e.g. Figure 3 ), the spray dryer 1 further comprises at least one conveyor 14 extending below the discharge outlet 4 and configured to receive the atomized ceramic powder CPA from the discharge outlet 4 and convey it away from the spray dryer 1.

[0034] According to some advantageous but non-limiting embodiments, for example Figure 1 , Figure 2 and Figure 3In the embodiments shown in FIG. 1 , the body 2 comprises a substantially cylindrical upper portion 15, a substantially frustoconical lower portion 16 and a substantially cylindrical central portion 17 which is inserted without a gap between the upper portion 15 and the lower portion 16 and delimits the atomization chamber 3 (see in particular FIG. Figure 3 ). In this case, advantageously but without imposing limitations, the above-mentioned distribution device 12 is arranged at the upper part 15, the injection unit 7 is arranged along the interface section (i.e., transition section) between the lower part 16 and the central part 17, and the discharge outlet 4 is arranged at one end of the second (lower) part 15 arranged on the opposite part (i.e., on the opposite side) compared to the central part 16.

[0035] As already mentioned above, according to some advantageous but non-limiting embodiments, the spraying unit 7 is configured to send the sprayed aqueous suspension of ceramic material in the form of a vertical jet towards the distribution device 12 (in particular, towards the upper part 15; more specifically, upwards). Additionally or alternatively, advantageously but without imposing limitations, the distribution device 12 is configured to direct the above-mentioned hot air flow F in the opposite direction, thus towards the lower part 16 (in particular, downwards). In this way, it is possible to increase the time that the aqueous suspension of ceramic material (and more specifically, the solid ceramic material) remains in the atomization chamber 3. This aqueous suspension of ceramic material is in fact initially emitted upwards in the opposite direction relative to the hot air flow F (therefore, in counterflow), and then once it reaches the highest end of the central part 17, it re-passes through the atomization chamber 3 downwards (therefore in the same direction as the hot air flow F), thereby significantly improving the efficiency of the spray dryer in terms of heat exchange.

[0036] In this discussion, the terms "high", "low", "upper" and "lower" are used with reference to the spray dryer 1, which has a longitudinal symmetry axis Z, and the spray dryer 1 rests on the ground so that the longitudinal symmetry axis Z is substantially perpendicular to the ground (e.g., Figure 1 , Figure 2 and Figure 3 shown).

[0037] According to some advantageous but non-limiting embodiments, the body 2 comprises (in particular is made of) stainless steel, more advantageously but without imposing limitation, the stainless steel being insulated with high-density mineral wool.

[0038] Advantageously, the heating system 6 comprises at least one electric heater 18 (in particular, consists of at least one electric heater 18 ).

[0039] This makes it possible to reduce carbon dioxide emissions and obtain significant energy savings with the same performance. Advantageously, in practice, the electric heater 18 has a yield of up to 95% (in particular, a yield that can vary from about 80% to about 90%).

[0040] According to some advantageous but non-limiting embodiments of the present invention, for example Figure 4 , Figure 5 and Figure 6 In the embodiments shown in the drawing, the electric heater 18 further comprises: a housing 19 defining a heating chamber 20; an inlet 21 for supplying gas into the heating chamber 20; a plurality of electric heating elements 22 extending inside the heating chamber 20, the plurality of electric heating elements 22 being configured to transfer heat to the gas found (i.e. passing through) in the heating chamber 20 by the Joule effect so as to generate the above-mentioned hot gas flow F; and an exhaust outlet 23, the exhaust outlet 23 being configured to enable the hot gas flow F to be discharged from the heating chamber 20 and being placed in fluid communication with the distribution device 12.

[0041] According to some advantageous but non-limiting embodiments (such as those shown), the inlet 21 and the exhaust outlet 23 face each other, and the electric heating element 22 is inserted between the inlet 21 and the exhaust outlet 23 so as to be passed through (or hit) by the gas to be heated. In this way, the gas to be heated will be heated by these electric heaters 22 when it passes through the heating chamber 20.

[0042] Advantageously but without limitation, the electric heater 18 is configured to heat the 3 / h to about 200000m 3 / h (especially from about 30000m 3 / h to about 200000m 3 / h; more specifically, from about 30000m 3 / h to about 80000m 3 / h varies; more advantageously, it is equal to about 50000m 3 / h) to generate the above-mentioned hot air flow F.

[0043] According to some advantageous but non-limiting embodiments, the gas comprises (in particular consists of) ambient air with at least 14% oxygen. Alternatively or in combination, the gas to be heated comprises (in particular consists of) recycled gas.

[0044] According to some advantageous but non-limiting embodiments, the housing 19 of the electric heater 18 has a substantially parallelepipedal cross section, for example a cuboid cross section with the following dimensions: 3000x2000x3000.

[0045] According to some advantageous but non-limiting embodiments of the invention, at least a portion of these plurality of electric heating elements 22 comprises (in particular is made of) a resistor 24 extending inside the heating chamber 20 .

[0046] According to some advantageous but non-limiting embodiments, these resistors 24 are in the form of coils (see for example Figure 5 or Figure 6 ). Alternatively, the shape of these resistors resembles a spiral (see, for example, Figure 4 ).

[0047] Furthermore, according to some advantageous but non-limiting embodiments, these resistors are smoothed, preferably but not limitedly enhanced (see for example Figure 5 ).

[0048] According to other advantageous but non-limiting embodiments, the resistor has fins (see for example Figure 6 ). This makes it possible to increase the size of the heat exchange surface and thus improve the thermal efficiency of the spray dryer 1.

[0049] Alternatively or additionally, advantageously but not limitingly, at least a portion of the plurality of electric heating elements 22 comprises (particularly consists of) an oblong resistive element 25, preferably but not necessarily made of aluminum and / or ceramic, and a metal cover 26 having a three-dimensional mesh structure, for example like a basket, and arranged to be at least partially wound around the oblong resistive element 25 on the outside, and to heat the gas found (i.e. passing) in the heating chamber 20 by the Joule effect. More advantageously but not limitingly, the metal cover 26 comprises (particularly consists of) a metal wire comprising (particularly made of) an iron-chromium-aluminum alloy or a nickel-chromium-aluminum alloy (more advantageously but not limitingly, an iron-nickel-chromium alloy) or a combination thereof.

[0050] According to some advantageous but non-limiting embodiments, in this case the electric heater 18 comprises (is in particular) a known electric air heating module.

[0051] According to some advantageous but non-limiting embodiments, Figure 1 , Figure 2 and Figure 3In the embodiment shown in the figure, the heating system 6 comprises at least one pressurized fan 27, which is configured to suck the above-mentioned gas (in particular, from the outside) and convey it towards the inlet of the electric heater 18, so as to circulate the gas to be heated in the heating chamber 20; and a duct 28 inserted between the electric heater 18 and the distribution device 12, which is configured to supply the hot gas flow F to the distribution device 12. Advantageously, but without imposing limitations, the duct 28 has an inlet section tangential to the body, which is substantially cylindrical (see Figure 1 , Figure 2 and Figure 3 ).

[0052] According to other advantageous but non-limiting embodiments, Figure 3A In the embodiment shown, the spray dryer 1 comprises a duct 28 inserted between the electric heater 18 and the body 2 to supply a hot gas flow F to the atomization chamber 3, wherein the hot gas flow F is pressurized by the above-mentioned suction system 30, in particular by the aspirator 31, without the need for a fan 27. In this case, advantageously but without imposing limitations, the duct 28 is joined to the top of the cylindrical body 2 (in particular, to the top of the substantially cylindrical upper part 15) to send the hot gas flow F to the atomization chamber 3 (see Figure 3A ). Advantageously but not limitingly, the pipe 28 is made of steel and more advantageously it is insulated.

[0053] The use of a heating system 6 of the type described above with an electric heater 18 significantly reduces the radiant heat transfer. This makes it possible in particular to reduce the amount of insulation required in the pipe 28 to approximately 25%.

[0054] According to some advantageous but non-limiting embodiments, the heating system 6 comprises (particularly consists of) a plurality of electric heaters 18 arranged in series, wherein each electric heater 18 is advantageously but without limitation made according to any of the above-described embodiments.

[0055] According to some advantageous but non-limiting embodiments, Figure 2 In the embodiment schematically shown in FIG. 1 , the heating system 6 also comprises a standard burner 29, for example, which uses known fossil fuels (gas or liquid). In this case, advantageously but not limitingly, the gas to be heated first passes through the electric heater 18 and then through the standard burner 29. This enables better control of the temperature and volume of the hot gas flow F sent to the atomization chamber 3.

[0056] According to some advantageous but non-limiting embodiments, Figure 3 and Figure 3AIn the embodiment shown, the spray dryer 1 further comprises a fume extraction system 30 for eliminating the exhaust fumes generated in the case of drying of the aqueous suspension of ceramic material in the atomization chamber 3. The extraction system 30 is configured to convey these exhaust fumes leaving the spray dryer 1 and to filter them and / or reduce them.

[0057] According to some advantageous but non-limiting embodiments, the exhaust system 30 comprises: at least one aspirator 31 for absorbing the exhaust fumes; at least one filtering and / or reducing device for filtering the exhaust fumes, such as a bag filter; and a chimney 32 for sending the fumes to the external environment.

[0058] According to some advantageous but non-limiting embodiments, for example Figure 3A In the embodiment shown, the smoke extraction system 30 is at least partially identical to the extraction system 30 described above.

[0059] According to another aspect of the present invention, there is provided a method for producing an atomized ceramic powder CPA from an aqueous ceramic material suspension (advantageously but not limitatively manufactured as described above with respect to the spray dryer 1) by atomizing the aqueous ceramic material suspension using the spray dryer 1 (advantageously manufactured as described above).

[0060] More specifically, advantageously but not limitingly, the production of atomized ceramic powder CPA is carried out by spraying an aqueous ceramic material suspension, the aqueous ceramic material suspension comprising at least about 30% by weight (particularly at least about 32%) of water and the remainder of solid ceramic material (particularly, consisting of at least about 30% by weight (particularly, at least about 32%) of water and the remainder of solid ceramic material). In particular, as already mentioned above with respect to the spray dryer 1, advantageously but not limitingly, the solid ceramic material comprises clay, kaolin, feldspar, quartz sand and / or a combination thereof (particularly, consisting of clay, kaolin, feldspar, quartz sand and / or a combination thereof). More advantageously but not limitingly, such an aqueous ceramic material suspension has a density that can vary from about 1600 g / l to about 1750 g / l and a density that can vary from about 5.0×10 -6 m 2 / s to about 3.0×10 -5 m 2 / s different kinematic viscosities.

[0061] Advantageously, the method for producing atomized ceramic powder CPA comprises the following steps: a supply step, during which the supply system 5 (advantageously but not limitatively implemented according to one of the above-mentioned embodiments) supplies (particularly, a defined amount, i.e. a controlled or measured amount) of a ceramic material aqueous suspension to the spray dryer 1, and the spray unit 7 of the supply system 5 sprays the ceramic material aqueous suspension and sends the sprayed ceramic material aqueous suspension into the above-mentioned atomization chamber 3; a heating step, during which the heating system 6 (advantageously but not limitatively implemented according to any one of the above-mentioned embodiments) generates a hot gas flow F having a temperature of at least about 400° C. (particularly, in the range between about 500° C. and about 600° C.); and a distribution step, during which the distribution device 12 distributes the hot gas flow F into the atomization chamber 3 so that the hot gas flow F hits the sprayed ceramic material aqueous suspension, thereby causing drying of the solid ceramic material contained therein and producing atomized ceramic powder CPA.

[0062] Advantageously, as already mentioned above with respect to the spray dryer 1, the heating system 6 comprises (in particular consists of) at least one electric heater 18 (advantageously manufactured according to one of the above-mentioned embodiments). More advantageously but not limitingly, in these cases, during the heating step, the electric heater 18 heats a certain amount of gas to generate the above-mentioned hot gas flow F; more specifically, the electric heater 18 heats a certain amount of gas from about 4000 m 3 / h to about 200000m 3 / h (especially, 30000m 3 / h to about 200000m 3 / h; more specifically, from about 30000m 3 / h to about 80000m 3 / h; more particularly, equal to about 50000m 3 / h) of air flow to generate the above-mentioned hot air flow F.

[0063] Advantageously, but without imposing limitation, when the distribution device 12 of the spray dryer 1 for implementing the production method comprises the above-mentioned annular guide duct 13, this annular guide duct 13 imparts a swirl movement about the axis of symmetry Z to said hot gas flow F during the distribution step.

[0064] Alternatively or in combination, advantageously but without limitation, when the distribution device 12 of the spray dryer 1 for implementing the production method comprises a suction system 30, this suction system 30 imparts a swirl movement about said axis of symmetry Z to the hot gas flow F during the distribution step.

[0065] Advantageously but not restrictively, the production method also includes: a gas supply sub-step, during which gas is supplied into the heating chamber 20 through the inlet 21 of the heating chamber 20 of the electric heater 18; a heating sub-step (at least partially) simultaneous with the gas supply sub-step, during which a plurality of electric heating elements 22 extending inside the heating chamber 20 (as better explained with respect to the spray dryer 1, the plurality of electric heating elements 22 are included in the electric heater 18) transfer heat to the gas found inside the heating chamber 20 through the Joule effect, thereby generating the above-mentioned hot gas flow F; and a gas discharge sub-step, during which the hot gas flow F leaves the discharge outlet 23 and is transferred to the distribution device 12.

[0066] According to some advantageous but non-limiting embodiments, the production method further comprises: (at least partially) an suction step preceding the gas supply sub-step, during which a pressurized fan 27 as part of the heating system 6 sucks (in particular, a certain amount / flow rate) of gas and conveys it towards the inlet 21 of the electric heater 18; and (at least partially) a transfer step simultaneously with the gas discharge sub-step, during which a hot gas flow F coming out of the discharge outlet 23 passes through (in particular, moves through) a pipe 28 inserted between the electric heater 18 and the distribution device 12.

[0067] The above-described spray dryer 1 and production method for producing atomized ceramic powder CPA have many advantages, among which we list the following advantages.

[0068] With the same performance in terms of the volume of hot gas sent into the atomization chamber 3 and the temperature of this hot gas flow F, the use of a heating system 6 comprising (in particular consisting of) an electric heater reduces CO 2 emissions and energy consumption.

[0069] Furthermore, the above-described heating system 6 is easily adaptable to the configuration of prior art spray dryers equipped with gas or liquid fuel burners.

[0070] Finally, it should be noted that the use of an electric heater 18 of the above-described type reduces the water content (in fact, water is eliminated as a waste product of combustion) compared to the use of gas or liquid fuel burners used in prior art solutions, thereby promoting the drying of the sprayed aqueous suspension of ceramic material and, therefore, promoting the production of atomized ceramic powder CPA and reducing energy consumption.

Claims

1. A spray dryer (1) for producing atomized ceramic powder (CPA) from an aqueous suspension of ceramic material, the spray dryer (1) comprising: a body (2) defining an atomization chamber (3) and comprising at least one discharge outlet configured to allow the atomized ceramic powder (CPA) to leave the atomization chamber (3); a supply system (5) for supplying a ceramic material aqueous suspension containing at least about 30% by weight of water and the remainder of solid ceramic material into the atomization chamber (3), the supply system (5) comprising at least one spray unit (7) configured to spray the ceramic material aqueous suspension and introduce the sprayed ceramic material aqueous suspension into the atomization chamber (3); a heating system (6) for generating a hot gas flow (F) having a temperature of at least about 400° C. (particularly in the range from about 500° C. to about 600° C.); a distribution device (12) configured to distribute the hot gas flow (F) into the atomization chamber (3) so that the hot gas flow (F) hits the sprayed ceramic material aqueous suspension, thereby drying the solid ceramic material contained therein and producing an atomized ceramic powder (CPA); The heating system (6) comprises at least one electric heater (18) (in particular, consists of at least one electric heater (18)); The spray dryer (1) is characterized in that the at least one electric heater (18) further comprises: a housing (19) defining a heating chamber (20); an inlet (21) for supplying gas into the heating chamber (20); a plurality of electric heating elements (22) extending inside the heating chamber (20), the plurality of electric heating elements (22) being configured to transfer heat to the gas located inside the heating chamber (20) through the Joule effect, so that the gas generates the hot gas flow (F); and an exhaust outlet (23), the exhaust outlet (23 ) is configured to make the hot gas flow (F) leave the heating chamber (20) and is fluidly connected to the distribution device (12); and at least a part of the electric heating element (22) includes an oblong resistor element (25) and a metal cover (26) (in particular, consists of an oblong resistor element (25) and a metal cover (26)), the metal cover (26) having a three-dimensional mesh structure and being arranged to at least partially wrap around the oblong resistor element (25) on the outside and heat the gas located inside the heating chamber (20) by the Joule effect.

2. The spray dryer (1) according to claim 1, wherein the metal cover (26) comprises (in particular, consists of) a metal wire, wherein the metal wire is made of an iron-chromium-aluminum alloy or a nickel-chromium alloy or an iron-nickel-chromium alloy or a combination thereof.

3. A spray dryer (1) according to claim 1 or 2, wherein at least a portion of the electric heating element (22) comprises a resistor (24) extending inside the heating chamber (20) (in particular, consists of a resistor (24) extending inside the heating chamber (20)).

4. The spray dryer according to any one of the preceding claims, wherein the heating system (6) comprises: at least one pressurized fan (27), the at least one pressurized fan (27) being configured to draw the gas (G) and convey the gas (G) toward the inlet (21) of the at least one electric heater (18); and a duct (28), the duct (28) being inserted between the at least one electric heater (18) and the distribution device (12) and being configured to supply the hot gas flow (F) into the atomization chamber (3) (in particular, to the distribution device (12)).

5. The spray dryer (1) according to any one of the preceding claims, wherein: The body (2) has a substantially vertical axis of symmetry (Z); The spraying unit (7) comprises a plurality of nozzles (8) arranged along at least one substantially annular crown, the center of the crown being located on the axis of symmetry (Z); and The distribution device (12) comprises at least one annular guide duct (13) configured to impart a swirling motion about the axis of symmetry (Z) to the hot gas flow (F).

6. The spray dryer (1) according to claim 5, wherein the distribution device (12) comprises: a plurality of openings for directing the hot gas flow (F) toward the atomization chamber (3); A plurality of spiral ducts and a plurality of deflectors for directing the hot gas flow (F) toward the plurality of openings.

7. The spray dryer (1) according to any one of claims 1 to 4, wherein: The body (2) has a substantially vertical axis of symmetry (Z); The spraying unit (7) comprises a plurality of nozzles (8) along at least one substantially annular crown, the center of which is located on the axis of symmetry (Z); and The distribution device (12) comprises a suction system (30) configured to impart a swirling motion about the axis of symmetry (Z) to the hot gas flow (F).

8. The spray dryer (1) according to any one of the preceding claims, wherein: The body (2) comprises a substantially cylindrical first portion (15), a substantially conical second portion (16) and a substantially cylindrical central portion (17), the central portion (17) being inserted without gap between the first portion (15) and the second portion (16) and defining the atomization chamber (3); The distribution device (12) is arranged at the first portion (15); and The discharge outlet (4) is arranged at an end of the second portion (16) opposite to the central portion (17).

9. The spray dryer (1) according to any one of the preceding claims, wherein the heating system (6) comprises a plurality of electric heaters arranged in series.

10. A method for producing atomized ceramic powder (CPA) from an aqueous suspension of ceramic material using a spray dryer (1) according to any of the preceding claims; The production method comprises the following steps: a supplying step, during which the supplying system (5) supplies a ceramic material aqueous suspension containing at least about 30% by weight of water and the remainder of solid ceramic material into the spray dryer (1), and the spraying unit (7) sprays the ceramic material aqueous suspension and sends the sprayed ceramic material aqueous suspension into the atomizing chamber (3); a heating step, during which the heating system (6) generates a hot gas flow (F) having a temperature of at least about 400° C. (particularly, in the range from about 500° C. to about 600° C.); and A distribution step is at least partially subsequent to the heating step, during which a distribution device (12) distributes the hot gas flow (F) into the atomizing chamber (3) so that the hot gas flow (F) hits the sprayed ceramic material aqueous suspension, thereby drying the solid ceramic material contained therein and producing an atomized ceramic powder (CPA).

11. The production method according to claim 10, wherein the heating step comprises: a gas supply sub-step, during which gas is supplied into the heating chamber (20) of the electric heater (18) through the inlet (21); a heating sub-step at least partially simultaneous with the gas supplying sub-step, during which the plurality of electric heating elements (22) extending inside the heating chamber (20) transfer heat to the gas inside the heating chamber (20) by the Joule effect and generate the hot gas flow (F); and A gas exhaust sub-step, during which the hot gas flow (F) leaves the exhaust outlet (23) and is transferred to the distribution device (12).

12. The production method according to claim 11, comprising: an extraction step at least partially preceding the gas supply sub-step, during which a pressure fan (27) as part of the heating system (6) extracts the gas (G) and conveys the gas (G) towards the inlet (21) of the at least one electric heater (18); and a transfer step at least partially simultaneous with the gas discharge sub-step, during which the hot gas flow (F) coming out of the discharge outlet (23) passes through (in particular, moves through) the duct (28) inserted between the at least one electric heater (18) and the distribution device (12).

13. A production method according to any one of the preceding claims 10 to 12, for producing atomized ceramic powder (CPA) from an aqueous suspension of ceramic material using a spray dryer (1) made according to claim 5; wherein during the distribution step, the annular guide duct (13) imparts a swirling motion around the axis of symmetry (Z) to the hot gas flow (F).

14. A production method according to any one of the preceding claims 10 to 12, for producing atomized ceramic powder (CPA) from an aqueous suspension of ceramic material using a spray dryer (1) made according to claim 6; wherein during the distribution step, the suction system (30) imparts a swirling motion around the axis of symmetry (Z) to the hot gas flow (F).

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