Method and apparatus for firing base ceramic articles

Abstract

Method and apparatus (1) for firing base ceramic articles (BC) which comprises: conveying the base ceramic articles (BC) along a given path (T) through a firing chamber (4) of a kiln (2); firing the base ceramic articles (BC) by operating a heating system (8) and a cooling system (17) adapted to impose a given temperature on the base ceramic articles (BC) going through the firing chamber (4) so as to fire them and gradually cool them to obtain ceramic products (P); which, leaving the kiln (2), are analysed to detect any density unevenness and / or colour unevenness so as to adjust, consequently, the operation of the kiln (2).

Description

[0001] "METHOD AND APPARATUS FOR FIRING BASE CERAMIC ARTICLES"

[0002] Cross-Reference to Related Applications

[0003] This Patent Application claims priority from Italian Patent Application No . 102024000021170 filed on September 23 , 2024 , the entire disclosure of which is incorporated herein by reference .

[0004] Technical Field

[0005] The present invention relates to a method and an apparatus for firing base ceramic articles with automatic adj ustment . In particular, the present invention is advantageously applied in firing base ceramic articles to obtain ceramic products , in particular ceramic slabs or tiles , to which the following description will explicitly refer without thereby losing generality .

[0006] Background of the Invention

[0007] In the field of manufacturing ceramic slabs or tiles , it is known to fire the base ceramic articles at high temperature , obtained by pressing a semi-dry mix (possibly followed by a decoration step ) , inside a kiln, typically of the tunnel type .

[0008] A kiln for firing base ceramic articles is normally divided into a pre-heating zone , an actual firing zone and a cooling zone . The base ceramic articles , carried by a conveying device , pass through the di f ferent zones of the kiln characteri zed by di f ferent temperatures and are fired so as to obtain the final ceramic products .

[0009] Usually, the ki ln comprises a plurality of burners organi zed in groups of burners , and arranged along the bottom to heat , in a controlled manner, the various zones of the kiln ( in particular, at least the pre-heating zone and the firing zone) . Each burner comprises a mixing body, in which a predefined quantity (flow rate) of fuel mixture (for example comprising methane gas or LEG) and a predefined quantity (flow rate) of oxidizer (typically ambient air having about 21% oxygen) are mixed together to generate a combustion mixture, and a combustion chamber in which the combustion mixture is burned so as to heat the firing chamber of the kiln.

[0010] To obtain an optimal firing of the base ceramic articles, it is important to precisely control the firing conditions within the various zones of the kiln. In fact, firing the ceramic articles in non-optimal conditions, for example at an overly low or overly high firing temperature, inevitably leads to defects in the final ceramic products, such as for example defects in shape, such as lack of flatness, or defects in colour or brightness, or cracks or fractures, especially along the edges, etc. This results in an increase in production rejects.

[0011] A relevant role in the variations of the firing conditions is played by the volume ratio between the oxidizer mixture and the fuel mixture. For example, in the presence of higher or lower percentages of oxygen (more or less oxidizing environment) different colour effects can be obtained and phenomena can arise, such as incomplete combustion of the organic residues included in the mix or subtraction of oxygen from iron oxides in base ceramic articles having an uneven density in the thickness that occur with the appearance of the so-called "black core", or with the presence of halos of a different colour, generally yellow-green or black, or in any case with the presence of diffuse colour unevenness in the body of the final ceramic product .

[0012] However, the adj ustment of the volume ratio between the oxidi zer and the fuel mixture in the combustion mixture in the known kilns is a rather complex operation that is executed manually, or by means of pneumatic systems , and which requires , in any case , the intervention of a skilled technician who acts on the fuel mixture feeding device and / or on the oxidi zer mixture feeding device , resulting in long production downtimes . It is understood that to guarantee the ef ficiency of the firing cycle , al so in terms of energy and consumption, such adj ustment should be carried out whenever any of the firing conditions changes , for example , the composition of the ceramic powder that forms the base ceramic articles or the kiln filling degree , the temperature , the duration of the firing cycle , the oxidi zer mixture or the fuel mixture etc . In reality, such adj ustment is often carried out much more rarely, adj usting the kiln to the most di f ficult firing conditions and accepting in the remaining cases an operation in non-optimal conditions in terms of ef ficiency and consumption .

[0013] Precisely to try to address such problems , some solutions have been developed over the years which entail the monitoring of some operating parameters of the kiln ( for example , the temperature in the firing zone ) and the consequent control of the operation of the fuel mixture and / or the oxidi zer mixture feeding systems , as explained in IT202100023858 of the same applicant . However, such solution, based on a detection of the temperature inside the kiln, does not take into account the variations of those conditions that depend on the product that is introduced in the kiln, for example , more or less signi ficant variations in the composition of the base ceramic articles, in their thickness, in their format and / or in their degree of compaction thereof, etc.

[0014] Other known solutions instead entail measuring the shape and / or size of at least some of the fired ceramic products, and adjusting through feedback the firing temperature inside the kiln. However, such solutions also have limitations.

[0015] The detection of the finished products is generally carried out once the products reach the so-called lines of choice, i.e., near the storage and / or packaging area of the ceramic products. This does not allow to have real-time feedback of the kiln; in fact, the adjustment will take place with a non-negligible delay, with a consequent increase in production waste and decrease in the adjustment precision. Furthermore, such solutions do not allow understanding whether any defects detected affect all the areas of the kiln or only some parts, with consequent limitations in determining the adjustments, which will be applied to all the areas of the kiln in the same manner.

[0016] Furthermore, the known methods for adjusting the kiln are designed to ensure that the temperature in the various parts of the kiln is always consistent with the set firing cycle. In some cases, this determines non-optimal firing conditions, at least from the point of view of energy consumption and therefore emissions, an increasingly critical aspect, especially in view of the increasingly stringent environmental and energy regulations.

[0017] The object of the present invention is to provide a method and an apparatus for firing base ceramic articles, which make it possible to overcome, at least in part, the drawbacks of the prior art .

[0018] Summary

[0019] In accordance with the present invention, a method and an apparatus for firing base ceramic articles are proposed, according to what is described in the appended independent claims , and preferably, in any of the claims directly or indirectly dependent on the aforementioned independent claims .

[0020] The claims describe preferred embodiments of the present invention, forming an integral part of the present description .

[0021] Brief Description of the Drawings

[0022] The invention i s described in the following with reference to the accompanying drawings , which illustrate some non-limiting example embodiments thereof , wherein :

[0023] - Figure 1 is a side and schematic view of a firing apparatus of base ceramic articles that schematically illustrates the kiln, the monitoring station and the automatic control system of the kiln; and

[0024] - Figure 2 is a schematic view of a possible embodiment of the monitoring station of ceramic products schematically illustrated in Figure 1 .

[0025] Detailed Description

[0026] In the accompanying figures , the reference numeral 1 indicates , as a whole , an apparatus for firing base ceramic articles BC with automatic adj ustment . In particular, the present discussion will refer in particular to firing base ceramic articles BC which are substantially (but not necessarily) flat to obtain ceramic products P, more in particular ceramic slabs or tiles .

[0027] The substantially (but not necessarily) flat base ceramic articles BC, referred to in the present discussion, hereinafter defined for the sake of brevity as only "ceramic articles BC" , are generally obtained by pressing a ceramic mix ( i . e . , a semi-dry mix, in particular having a humidity ranging from 4 % to 9% ) mainly based on silica ( at least about 35% - in particular, at least about 40% - by weight with respect to the total weight of the silica base ceramic articles BC ) and having less than about 50% ( in particular, less than about 30% ) by weight , with respect to the total weight of the ceramic articles BC, of alumina . According to some non-limiting embodiments , the ceramic articles BC comprise up to about 80% by weight , with respect to the total weight , of silica . Normally, the ceramic articles BC comprise further inorganic oxides such as the oxides of Magnesium, Zirconium, Sodium and Potassium . For example , a generic mix for a common porcelain stoneware has : about 10e25 by weight with respect to the total weight o f illitic clay mix ; about 25^55% by weight with respect to the total weight of kaolinitic clay mix; about 25e45% by weight with respect to the total weight of Feldspar mix; up to a maximum of about 10% by weight with respect to the total weight of Kaolin mix ; up to a maximum of about 10% by weight with respect to the total weight of quartz sand mix ; and up to a maximum of about 5% by weight with respect to the total weight of the mix of complementary materials ( e . g . , Dolomite ) .

[0028] Advantageously but not necessarily, the ceramic articles BC thus formed are then decorated and / or treated in treatment stations ( known per se and not described in detail herein) before being conveyed towards a kiln 2 , typically a tunnel kiln, by means of a conveying device 3 ( schematically illustrated in Figure 1 with a dashed line ) which passes through a firing chamber 4 of the kiln 2 .

[0029] The conveying device 3 is configured to convey the ceramic articles BC along a given path T extending from an input station 5 to an output station 6 of the apparatus 1 in an advancement direction A through the firing chamber 4 .

[0030] According to some non-limiting and non-illustrated embodiments , the conveying device 3 comprises a plurality of ceramic rollers (possibly moved at di f ferent speeds along the firing chamber 4 to di f ferentiate the firing of the ceramic articles BC ) .

[0031] In detail , advantageously, the kiln 1 comprises a side wall 7 (preferably tubular ) that laterally delimits the firing chamber 4 , which, advantageously but not limitedly, is divided into a pre-heating zone PZ , an actual firing zone C, arranged downstream of the pre-heating zone PZ along the given path T , and a cooling zone R, placed downstream of the firing zone C, to reduce the temperature of the ceramic articles BC before they leave the kiln 2 .

[0032] Advantageously but not limitedly, the firing chamber 4 is at least about 40m long; in particular, at least about 60m; more in particular, at least about 130m ( even more in particular, up to about 600m) .

[0033] The kiln 2 further comprises a heating system 8 comprising a plurality of burners 9 arranged in series along at least a segment of the firing chamber 4 ( in particular, along a segment extending at least through the pre-heating zone PZ and the firing zone C ) and each configured to burn a combustion mixture comprising a fuel mixture and an oxidi zer so as to heat the firing chamber 4 ( in particular, at least the pre-heating zone PZ and the firing zone C of the firing chamber 4 ) , imposing a given firing temperature in the various zones of the kiln 2, so as to fire the ceramic articles BC and obtain the ceramic products P (in particular, ceramic slabs or tiles) .

[0034] According to some advantageous but non-limiting embodiments, such as, for example, that illustrated in Figure 1, the burners 9 are organized in a plurality of groups 10, 10a, 10b of burners 9 independent of one another, placed above and below, or only above, or only below the given path T .

[0035] In detail, at least one first group 10a of burners 9 is arranged in the pre-heating zone PZ of the firing chamber 4 and is configured to impose in such zone PZ a variable preheating temperature along the given path T from about 500°C to about 1000°C and at least one other group 10b of burners 9 is arranged in the firing zone C (in particular, in the embodiment of the accompanying figure two groups 10b, 10 of burners 9 are arranged in the firing zone C) to impose in such zone C a firing temperature ranging from at least about 1000°C (in particular, at least about 1200°C; more in particular, at most about 1400°C; more in particular, equal to at most about 1300°C) .

[0036] Advantageously but not necessarily, each burner 9 comprises a mixing body (not illustrated) in which a fuel mixture, comprising at least a first fuel (for example methane gas or LPG) , and an oxidizer, typically ambient air with about 21% oxygen, are mixed to obtain the combustion mixture, and a combustion chamber (not illustrated) in which the combustion mixture (once ignited so as to obtain a flame) is burned, thus heating the firing chamber 4 and firing the ceramic articles BC .

[0037] According to some advantageous but non-limiting embodiments, the heating system 8 further comprises: at least one first feeding device 11 (only partially illustrated in Figure 1) configured to feed the fuel mixture towards each of the groups 10a, 10b, 10 of burners 9 and provided with at least one first electronically controlled flow adjustment element 12 (advantageously but not limitedly an electrically controlled partialization valve, and a second feeding device 13 (only partially illustrated in Figure 1) configured to feed an oxidizer mixture towards each of the groups 10a, 10b, 10 of burners 9 and provided with at least one second electronically controlled flow adjustment element 14 (advantageously analogous to the flow adjustment element 12) .

[0038] Even more advantageously but not necessarily, the fuel mixture feeding device 11 comprises (consists of) : at least one feeding duct 15 fluidly connected to each group 10a, 10b, 10 of burners 9 (more advantageously, as illustrated in Figure 1, the feeding duct 15 has a number of branches equal to the number of burners 9 of each group 10a, 10b of burners 9, respectively) and an electrically operated adjustment valve 12 arranged along the fuel mixture feeding duct 15 and operable (suitably openable) to adjust the quantity (the flow rate - i.e., the quantity by weight in the unit of time) of the fuel mixture to be fed to each group 10a, 10b, 10 of burners 9, and thus the quantity (flow rate) of the fuel mixture comprised in the combustion mixture.

[0039] Similarly, the oxidizer feeding device 13 comprises (in particular, consists of) : at least one feeding duct 16 fluidly connected to each group 10a, 10b, 10 of burners 9 (more advantageously, as illustrated in Figure 1, the feeding duct 16 has a number of branches equal to the number of burners 9 of each group 10a, 10b o f burners 9 , respectively) and an electrically operated adj ustment valve 13 arranged along the oxidi zer supply duct 16 and operable ( suitably openable ) to adj ust the quantity ( the flow rate - i . e . , the quantity by weight in the unit of time ) of oxidi zer to be fed to each group 10a, 10b, 10 of burners 9 , and therefore the quantity ( flow rate ) of the oxidi zer comprised in the combustion mixture .

[0040] It is specified that within the scope of the present description, the term " second" does not necessarily imply the presence of a " first" . Such terms are sometimes used as labels to improve clarity .

[0041] Advantageously, the kiln 2 further comprises a cooling system 17 arranged in the cooling zone R of the firing chamber 4 , and operable to lower the temperature of the ceramic articles BC going through at the cooling zone R of the firing chamber 4 . More advantageously but not limitedly, the cooling system 17 comprises at least one duct 18 for inj ecting cooling air into the firing chamber 4 .

[0042] According to some advantageous but non-limiting embodiments , the cooling system 17 comprises at least one air generator 19 ( only schematically illustrated in Figure 1 ) configured to generate a cooling air flow and at least the aforementioned duct 18 configured to inj ect such cooling air flow into the firing chamber 4 at the cooling zone R and at least one suction system 20 to suck air from inside the firing chamber 4 and convey it outwards , for example in the case illustrated in Figure 1 through the chimney 21 placed at the cooling zone R .

[0043] According to some advantageous but non-limiting and non-illustrated embodiments , the cooling system 17 further comprises a flow distribution element arranged along the duct 18 and configured to adj ust the distribution of the cooling air flow inside the firing chamber 4 ; in particular, crosswise to the firing chamber 4 ; for example , by directing a greater flow o f cooling air near the walls of the kiln 2 with respect to the centre or vice versa, or by directing a greater flow of cooling air under the ceramic rollers of the conveying device 3 with respect to above , or vice versa .

[0044] Advantageously but not limitedly, the kiln 2 also comprises a suction chimney 21 ' ( known per se ) arranged in the inlet segment of the firing chamber 4 and configured to suck the exhaust fumes from the firing chamber 4 , in particular at least from the pre-heating zone PZ and from the firing zone C and convey them outwards ( as schemati zed by arrows in Figure 1 ) .

[0045] With particular reference to the accompanying figures , advantageously, the apparatus 1 further comprises a monitoring system 22 arranged along the given path T , immediately out o f the kiln 2 , and configured to analyse the ceramic products P and to detect any density unevenness in the finished ceramic product P and / or any colour unevenness in both the thickness and in the outer perimeter surface of the finished ceramic product P .

[0046] More advantageously but not limitedly, such monitoring system 22 is arranged at a monitoring station 23 that is located immediately ( i . e . , without the interposition of other stations ) downstream of the kiln 2 along the given path T . This allows the almost instantaneous adj ustment of the kiln 2 on the basis of the collected monitoring data . In addition, the quality monitoring of the ceramic products P immediately downstream of the kiln 2 permits tracking, even with greater precision, the zones of the kiln 2 from which any defective ceramic products P come , as will be better explained below, and in which an intervention is necessary, permitting a more precise adj ustment of the operation of the kiln 2 .

[0047] According to some advantageous but non-limiting embodiments , such as the one shown in Figure 1 , the conveying device 3 also extends outside the kiln 2 up to the monitoring station 23 . According to other advantageous but non-limiting embodiments , such as the one illustrated in Figure 2 , the monitoring system 22 comprises a conveyor 24 which extends immediately ( seamlessly) downstream of the conveying device 3 and is configured to receive the ceramic products P leaving the kiln 2 and convey them towards the output station 6 , through the monitoring station 23 , and a detection unit 25 for detecting and analysing the ceramic products P and detecting at least the aforementioned density unevenness .

[0048] With particular reference to the embodiment , schematically illustrated in Figure 2 , advantageously but not limitedly, the monitoring system 22 comprises at least one emitter 26 configured to emit a radiation beam, for example of the radar type or comprising X-rays or a continuous beam of sub-THz FMCE ( frequency-modulated continuous-wave ) waves , onto an outer surface S of each ceramic product P which advances at the monitoring station 23 , which, advantageously but not limitedly, will be coated with absorbent material , and at least one optical reader, for example a 3D scanner, which can be integrated in the emitter 26 ( i . e . , carried by the same support structure ) or be separate from the emitter 26 , to capture images of the ceramic product P crossed by said radiation beam and assess possible density unevenness by means of an analysis of such image . Alternatively, instead of the optical reader there can be a receiver, for example placed on the opposite side to the emitter 26 with respect to the conveyor 3 , and configured to receive the radiation beam leaving ( i . e . , after it has crossed the ) ceramic product P and configured to assess based on the properties of such radiation beam leaving the ceramic product P any density unevenness and / or colour unevenness .

[0049] Even more advantageously but not l imitedly, the emitter 26 is carried in a mobile manner by a portal frame , as schematically illustrated in Figure 2 , in order to be able to move parallel to the surface S of the ceramic product or perpendicularly to the ceramic product P .

[0050] Alternatively, according to other non-illustrated embodiments , the monitoring system 22 is configured to analyse some ceramic products P on a sample basis , more in particular at regular time intervals , and comprises a robotic arm configured to make , on a sample basis , a fracture in a ceramic product P to be analysed, which is leaving the kiln 2 , and a viewing sensor ( for example a camera) conf igured to extract an image of the ceramic product P at said fracture and analyse the image by means of graphic analysis software , known per se , in order to detect a possible colour unevenness in the thickness of the ceramic product . It is , in fact , known in the field that the presence of colour unevenness , typically darker spots inside the body of the ceramic product P, the so-called "black core" is a symptom of a non-uni form density, typically due to firing under inadequate oxidation conditions inside the firing chamber 4 and / or to firing under conditions in terms of oxygen percentage and / or inadequate temperature and / or firing time etc .

[0051] Alternatively or additionally, according to some advantageous but non-limiting embodiments , the monitoring system 22 comprises at least one further detector 27 , for example in the illustrated case two cameras , which according to some advantageous but non-limiting embodiments coincide with or form part of the detection device 25 , each configured to also detect any tone defects .

[0052] According to some advantageous but non-limiting embodiments , the monitoring system 22 comprises a further detector 27 configured to detect tone defects which, in turn, comprises ( in particular, consists of ) : a lighting unit , for example provided with a LED source , to emit a light beam, advantageously LED, onto an outer surface S of each ceramic product P that advances at the monitoring station 23 ; and a linear RGB colour camera to capture images of the illuminated ceramic product P and an image processor configured to process , with analysis techniques known per se and not described in detail herein, the detected images and, even more advantageously but not limitedly, compare them with sample images to detect possible tone defects . More advantageously but not limitedly, the image processor comprises ( in particular, contains stored) sample images , one for each type of ceramic product P intended to be fired in the kiln 2 , and is configured ( in particular, programmed) to divide each image captured by the linear RGB colour camera into parts ( or plots ) and to associate each part ( or plot ) of the CIE Lab coordinates and to compare the CIE lab coordinates of the various parts o f the captured image with the coordinates of the corresponding sample image so as to determine i f there is a deviation and, when present , i f such deviation is greater than an acceptability limit value , also stored in such image processor so as to identi fy any tone defects .

[0053] It is specified that the CIE Lab coordinate system is a colour classi fication system standardi zed by the Commission Internationale de 1 ' Eclairage ( CIE ) used to classi fy the various colours based on three parameters : L* (brightness ) , a* ( green-red colour coordinates ) and b* (blue-yellow colour coordinates ) .

[0054] Alternatively or additionally, advantageously but not limitedly, the monitoring system 22 is configured ( for example by means of the further detector 27 ) to also detect any defects in shape and / or si ze and / or flatness of each output ceramic product P .

[0055] Alternatively or additionally, the monitoring system 22 is configured to also detect any breaks , fractures or structural defects of the ceramic product P .

[0056] According to some advantageous but non-limiting embodiments , the monitoring system 22 comprises yet another detector 27 configured to detect shape and / or si ze and / or flatness defects of each product P and / or structural defects which, in turn, comprises : an emitter configured to emit a laser beam onto an outer surface S of each ceramic product P advancing at the monitoring station 23 so that it intercepts the ceramic product P defining what is commonly called a " laser blade" ; and a receiver, for example advantageously but not limitedly an optical sensor, configured to capture the reflected beam and to estimate , by means of triangulation techniques ( known per se and not described in detail herein) , the distance of each reflection point from the receiver so as to reconstruct a three- dimensional profi le of the ceramic products P going through along the monitoring station 23 ; and a processor configured to analyse such profile to detect a possible shape and / or si ze and / or flatness of each output ceramic product P and any breaks , fractures or defects .

[0057] According to some advantageous but non-limiting and non-illustrated embodiments , the conveying device 3 comprises several conveying planes , in particular several planes of parallel rollers superimposed from one another at di f ferent heights . In this case, advantageously but not limitedly, the monitoring system 22 is configured to ( separately) analyse the ceramic products P leaving the kiln 2 by means of the various conveying planes ; for example , it comprises several detection units 25 , one for each conveying plane . Even more advantageously but not limitedly, in this case , the monitoring system 22 is also configured to compare the monitoring data obtained from the various monitoring units 25 with one another, or in any case the monitoring data of the ceramic products P coming from the various conveying planes , in order to assess , based on the distribution of the defects , whether there are areas of the kiln 2 that are critical from the point of view of the firing conditions and, i f there are , to identi fy the position thereof , so as to consequently adj ust the operation of the kiln 2 accordingly, as will be better explained below .

[0058] In this regard, it is speci fied that , advantageously but not limitedly, the groups 10a, 10b, 10 of burners 9 have burners 9 distributed above and below the ( or each) conveying plane . Therefore , i f during the monitoring one or more critical zones of the kiln 2 are identi fied, i . e . which generate ceramic products P having a greater number of defects , it is acted upon by adj usting the feeding of the fuel mixture and / or the oxidi zer in a di f ferentiated manner not only between the various groups 10a, 10b, 10 of burners 9 , but i f necessary also between the various burners 9 of the same group 10a, 10b, 10 of burners 9 so as to make the environmental conditions ( in particular, temperature , pressure and humidity) inside the firing chamber 4 as uni form as possible .

[0059] In detail , the apparatus 1 comprises a control unit CU, schematically illustrated in Figure 1 , which is configured ( i . e . programmed) to adj ust the operation of the kiln 2 in real time as a function of is the data detected by the monitoring system 22 .

[0060] Advantageously but not limitedly, the control unit CU is configured to command ( in particular, to control the operation of ) at least the heating system 8 ; more in particular, at least the electronically controlled flow adj ustment elements 12 , 14 to vary the flow rate of oxidi zer or fuel mixture to be fed to the various groups 10a , 10b, 10 of burners 9 . Advantageously but not limitedly, the control unit CU is also configured to command ( in particular, to control the operation) of the cooling system 17 ; in particular, of the air generator 19 and / or of the suction system 20 as a function of what is detected by the monitoring system 22 .

[0061] The control unit CU, which can also be arranged in a remote position with respect to the apparatus 1 , is advantageously but not limitedly configured to exchange data with the monitoring system 22 and with the kiln 2 ( in particular, at least with the heating system 8 and with the cooling system 17 ) to adj ust the operation thereof as a function of what is detected by the monitoring system 22 .

[0062] More advantageously but not limitedly, the kiln 2 is provided with a control group 28 adapted to command the operation of the heating system 8 ( in particular in the case illustrated at least of the various electronically controlled flow adj ustment elements 12 , 14 ) , so as to vary the firing temperature or the oxidation conditions in the various zones PZ , C of the firing chamber 4 , and the cooling system 17 , so as to vary the quantity of cooling air and / or the amount of suction and the control unit CU is also connected to the control group 28 . More in particular, the control unit CU receives data from the monitoring system 22 ( advantageously processes and / or analyses them by means of analysis techniques known per se ) and commands the kiln 2 accordingly, sending command signals to the control group 28 .

[0063] According to some advantageous but non-limiting embodiments , the control unit CU processes the data obtained from the monitoring system 22 , in particular at least the data regarding the presence of density unevenness and / or colour unevenness in the body of the ceramic product P and / or on the outer surface of such ceramic product P, to identi fy an operating condition of minimum consumption of the kiln 2 , which is associated with certain operating parameters of the kiln 2 and, therefore , commands the kiln 2 ( in particular, at least the heating system 8 ; more in particular, at least the group 10a of burners 9 ) to vary at least the quantity of oxidi zer fed at least to the pre-heating zone PZ , when density unevennes s and / or colour unevenness are detected in the body ( in the thickness ) of the ceramic product P and to vary the quantity of oxidi zer fed at least to the firing zone C, when colour unevenness is detected on the outer surface of the ceramic product P .

[0064] "Operating condition of minimum consumption of the kiln 2" means the limit operating condition, at least in terms of the percentage of oxidi zer fed to each group 10 , 10a, 10b of burners 9 (which will be the minimum possible ) , in which the kiln 2 fires the ceramic articles BC generating ceramic products P without density discontinuity .

[0065] When the conveying device 3 compri ses several conveying planes , as already mentioned above , i f the monitoring system 22 detects , as explained above , the presence of particularly critical zones of the firing chamber 4 , the control unit CU commands the feeding devices 11 and 13 (more in particular the adj ustment elements 12 , 14 ) of the various burners 9 arranged in the various parts of the kiln 2 in a di f ferentiated manner so as to find a way to make the firing conditions in the various zones of the firing chamber 4 uni form .

[0066] Alternatively or additionally, in this case , based on the position of any critical zones , the control unit CU commands the suction system 20 in a di f ferentiated manner, for example it reduces the suction force to the chimney 21 or increases the cooling air pressure , when critical zones are highlighted near the top wall of the kiln 2 .

[0067] According to some advantageous but non-limiting and non-illustrated embodiments , the heating system 8 also comprises a plurality of electric heaters ( flow heater type ) , at least at the firing zone C . This permits a reduction in the number of fuel burners 9 under the same firing conditions and therefore an advantage in terms of environmental emissions . In this case , advantageously but not limitedly, the control unit CU is configured to also command the operation of such electric heaters as a function of the data captured by the monitoring system, with the same logic clari fied above .

[0068] Advantageously but not limitedly, when the monitoring system 22 comprises at least one further detector 27 , the control unit CU is also configured to adj ust the heating system 8 , in particular the feeding system 13 of at least the group 10b of burners 9 so as to adj ust ( in particular, increase ) the flow rate of oxidizer to be fed to the burners 9 placed in the firing zone C . Alternatively or additionally, in this case , the control unit CU is configured to also adj ust the cooling system 17 , in particular the suction system 20 so as to adj ust ( in this case , for tone defects , reduce ) the pressure at least inside the firing zone C of the kiln 2 .

[0069] Advantageously but not limitedly, the control unit CU is also configured to adj ust the operation of the heating system 8 and / or o f the cooling system 17 also as a function of the defects of tone and / or shape and / or of si ze and / or of flatness and / or of the breaks detected by the further detector 27 , or by the further detectors 27 (when there is more than one ) .

[0070] According to some advantageous but non-limiting embodiments , the control unit CU comprises a writeable memory containing a programming of the interventions , which programming, in turn, comprises : a plurality of possible classi fied defects and which associates to each of said defects an order of priority and an intervention instruction . In greater detail , the control unit CU is configured to compare the data obtained from the monitoring system 22 with the possible defects contained in such programming to veri fy whether and how many of the classi fied defects are detected in each ceramic product P that is analysed by the monitoring system 22 and to execute the intervention instruction corresponding to the defect with the highest order of priority .

[0071] Advantageously but not limitedly, the apparatus 1 further comprises sensors 29 , known per se and not described in detail herein, arranged in the firing chamber 4 at di f ferent points and configured to detect at least the temperature and advantageously but not limitedly also the pressure at di f ferent points of the firing chamber 4 and which, even more advantageously but not limitedly, are in connection with the control group 28 , so that it can control the actual environmental conditions , in terms of temperature and pressure inside the firing chamber 4 .

[0072] According to another aspect of the present invention, a method for firing ceramic articles BC of the type described above is presented, advantageously but not limitedly implemented with an apparatus 1 made in accordance with one of the embodiments described above .

[0073] Advantageously, the method comprises the following steps : a conveying step, during which ceramic articles BC are conveyed along a given path T extending from an input station 5 to an output station 6 through a firing chamber 4 of a kiln 2 , advantageously by means of a conveying device 3 , made according to one of the embodiments described above ; a firing step, which is ( at least partially) simultaneous with the conveying step, during which a heating system 8 comprising at least a plurality of burners 9 , more advantageously made according to one of the embodiments described above , and a cooling system 17 , also advantageously made according to one of the embodiments described above , are operated to impose a given temperature on the ceramic articles BC going through the firing chamber 4 so as to fire and gradually cool them, obtaining ceramic products P .

[0074] Advantageously but not limitedly, the kiln 2 through which the firing step is carried out is made according to one of the embodiments described above and comprises the aforementioned pre-heating zone PZ , firing zone C and cooling zone R and a plurality of burners 9 divided into groups 10a, 10b and 10 , as described above in relation to the apparatus 1 .

[0075] Advantageously but not limitedly, the firing step comprises : a first feeding sub-step, during which a first feeding system 11 ( advantageously made as described above in relation to the apparatus 1 ) feeds a fuel mixture, comprising at least a first fuel , towards each of the groups 10a, 10b, 10 of burners 9 independently of one another, and a second feeding sub-step, during which a second feeding system 13 ( advantageously also made as described above in relation to the apparatus 1 ) feeds an oxidi zer mixture towards each of the groups 10a, 10b, 10 of burners 9 independently of one another .

[0076] The method further comprises : a monitoring step, which is ( at least partially) subsequent to the firing step, during which the ceramic products P leaving the kiln 2 are analysed, at a monitoring station 23 placed immediately downstream of the kiln 2 along the given path T , to detect any density unevenness in the finished ceramic product P and / or colour unevenness in both thicknes s and in the outer perimeter surface of the ceramic product P . In detail , according to some advantageous but non-limiting embodiments , the monitoring step i s carried out with an automatic monitoring system 22 ; more advantageously but not limitedly, made according to one of the embodiments described above .

[0077] The method further comprises an adj ustment step, which is ( at least partially) simultaneous with the firing step, during which a control unit CU adj usts , in real time , the operation of the kiln 2 ( in particular at least of the heating system 8 ) as a function of what is detected in the monitoring step .

[0078] Advantageously but not limitedly, during the adj ustment step the control unit CU adj usts at least the flow rate of oxidi zer that is fed to the first group 10a of burners 9 as a function of the density unevennes s and / or colour unevenness detected in the thickness of the ceramic product P . In particular, during the operation sub-step the control unit CU adj usts the operation of the first group 10a of burners 9 , increasing the flow rate of the oxidi zer fed by the feeding system 13 and therefore the percentage of oxidi zer in the combustion mixture fed to the burners 9 of the first group 10a of burners 9 , when during the monitoring step density unevennes s and colour unevenness have been detected within the ceramic product P . Alternatively or additionally, when during the monitoring step surface colour unevenness on an outer surface of the ceramic product P and / or tone defects are detected, during the operation sub-step the control unit CU adj usts the operation of the second group 10b of burners 9 by increasing the flow rate of oxidi zer to be fed to such group 10b of burners 9 .

[0079] According to some advantageous but non-limiting embodiments , the adj ustment step comprises : a processing sub-step, during which the control unit CU processes the data obtained in the monitoring step to identi fy an operating condition of minimum consumption of the kiln 2 ( already described in relation to the apparatus 1 ) , which is associated with given operating parameters of the kiln 2 ( as already mentioned above in relation to the apparatus 1 ) ; and an operation sub-step, during which the control unit CU commands the operation of at least the heating system 8 ( in particular, also of the cooling system 17 ) so as to impose the aforementioned given operating parameters of the kiln 2 .

[0080] Alternatively or additionally, during the adj ustment step, the control unit CU is also configured to adj ust ( i . e . , vary) the operation of the conveying device 3 , in order to vary the advancement speed of the ceramic articles BC and therefore their exposure time to certain firing conditions .

[0081] According to some preferred but non-limiting embodiments , the control unit CU is configured to identi fy the point of minimum consumption o f the kiln 2 , lowering the flow rate of oxidi zer in the pre-heating zone PZ until reaching a limit condition, at which the ceramic product P begins to have density unevenness and / or colour defects , and then increasing the quantity of oxidi zer fed to the preheating zone PZ and / or to the firing zone C enough to move away from the limit condition .

[0082] According to some non-limiting embodiments , during the monitoring step, a processing unit (not illustrated) , which is advantageously part of the monitoring system 22 , generates a first warning signal whenever a ceramic product P having density unevennes s is detected and a second warning signal , di f ferent from the first , whenever a ceramic product P having colour unevenness is detected and during the adj ustment step ( in particular during the operation sub- step) , the control unit CU commands the second feeding device 13 to reduce the flow rate of fuel that is fed in the aforementioned second feeding sub-step until it receives the aforementioned first warning signal and to increase the flow rate of fuel fed at least to the first group 10a of burners 9 , once the first warning signal is received and / or to reduce the flow rate of oxidi zer that is fed to the second group 10b of burners 9 until it receives the second warning signal and to increase the flow rate of oxidi zer fed to at least the second group 10a of burners 9 , once the second warning signal is received .

[0083] More in particular, once the kiln 2 is operated with certain initial operating parameters , the processing unit , included in the monitoring system 22 , processes a signal each time it analyses a ceramic product P and, the control unit CU receives data from the monitoring system 22 ( in particular, receives the signals processed by the processing unit ) and commands , consequently, the heating system 8 . In particular, the control unit CU commands a lowering of the flow rate of oxidi zer to be fed to the first group 10a of burners 9 each time it receives data di f ferent from a warning signal . In greater detail , once a warning signal has been received for the first time , the control unit CU commands an increase in the flow rate of oxidi zer to be fed to the first group 10a and / or to the second group 10b of burners 9 and then maintains such oxidi zer flow rate constant for a certain period, advantageously that necessary for the kiln 2 to enter into operating regime . Advantageously but not limitedly, such period is variable , based on the format of base ceramic articles BC treated, from at least about 10 minutes to at least about 120 minutes ; more in particular, from at least about 15 min to at least about 60 min . I f , after such period, the next signal received from the monitoring system 22 is not a warning signal , the control unit CU commands the heating system 8 to maintain the operating conditions constant until it receives a further warning signal . In this manner, it is possible to automatically adj ust the kiln 2 , which will always operate at the lowest consumption conditions with consequent obvious advantages .

[0084] Advantageously but not limitedly, the control unit CU is configured to receive data from the processing unit at regular intervals of time , and, consequently, to adj ust (vary i f necessary) the operation of the kiln 2 , for example by increasing or reducing the feeding of oxidizer or fuel to at least one group 10a, 10b, 10 of burners 9 .

[0085] According to some advantageous but non-limiting embodiments , during the monitoring step an analysis of the tone of the ceramic products P is also carried out in order to detect any tone defects , by means of comparison with standard tone data and during the adj ustment step the control unit CU commands the operation o f the feeding system 13 at least of the second group 10b of burners 9 , increasing the flow rate of oxidi zer to be fed to the burners 9 whenever colour unevenness is detected on the outer surface of the ceramic product P and / or tone defects . Alternatively or additionally, in this case , during the adj ustment step, the control unit CU also commands the operation of the cooling system 17 to increase the pressure inside the firing zone .

[0086] Even more advantageously but not limitedly, during the monitoring step an analysis of the shape and / or si ze of the ceramic products P is also carried out in order to detect possible defects ( in particular, to detect ceramic products P that are too large and / or too small , having flatness defects and / or cracks or irregularities ) and during the adj ustment step, the control unit CU commands the operation of the heating system 8 and / or of the cooling system 17 also based on the detected si ze and / or shape defects .

[0087] In detail , advantageously but not limitedly, during the aforementioned processing step, the monitoring system 22 ( in particular, the processing unit contained in the monitoring system 22 ) , which advantageously comprises a memory containing a series of standard data on the ceramic products P to be manufactured, detects any defects based on the comparison between what is detected and what is contained in the memory . In greater detail , advantageously but not limitedly, such memory comprises , for each type of ceramic product P to be manufactured, data on standard tones , standard shapes and standard si zes . According to still other advantageous but non-limiting embodiments , the memory also contains a plurality of types of possible defects in tone , and / or shape and / or flatness .

[0088] According to some preferred but not exclusive embodiments , the memory contained in the control unit CU further comprises a programming of the interventions , which programming, in turn, comprises : a plurality of possible defects classi fied by increasing order of priority and which associates an intervention instruction with each of the defects ; and during said adj ustment step, the control unit CU compares the data obtained in such monitoring step with the possible defects contained in the programming to veri fy whether and how many of the classi fied defects are detected in each ceramic product P and executes the intervention instruction corresponding to the defect with the highest order of priority among those found in such monitoring step .

[0089] For example , when a ceramic product P with gauge de fects ( i . e . , too large or too small ) is detected, during the adj ustment step the heating system 8 is adj usted, in order to increase (when the ceramic product P is too small ) or reduce (when the ceramic product P is too large ) the firing temperature , for example by increasing or decreasing the fuel mixture flow rate or by reducing or increasing the advancement speed of the conveying device 3 in order to increase the firing time .

[0090] When a ceramic product P with flatness defects is detected, e . g . concave shape with concavity facing upwards or downwards , during the adj ustment step the cooling air pressure emitted by the air generator 19 is respectively reduced or increased and / or the orientation of the air flow generated by such air generator 19 is adj usted; or the cooling air flow to be sent towards the base ceramic articles BC is varied as these advance through the cooling zone R, advantageously by means of operation of the above-described flow distribution element , e . g . , by sending a greater cooling air flow above the base ceramic articles BC with respect to below, or vice versa, or a greater air flow from one side of the firing chamber 4 , rather than from the opposite side . Alternatively or additionally, also in this case , the temperature in the firing zone C is increased or reduced, increasing the flow of fuel fed to the group 10b of burners 9 .

[0091] According to some advantageous but non-limiting embodiments , when the conveying device 3 has several conveying planes , the method comprises at least one analysis step, which is ( at least partially) prior to the adj ustment step, during which the monitoring data of the ceramic products P leaving the kiln 2 by means of the various conveying planes are compared with one another in order to assess , based on the distribution of the defects , whether there are areas of the kiln 2 which are critical from the point of view of the firing conditions and i f , there are , how they are arranged; and during the adj ustment step, the control unit CU adj usts the operation of at least the heating system 8 as a function of what has been assessed in such analysis step .

[0092] The apparatus 1 and the method for firing ceramic articles BC of the present invention have numerous advantages , among which the following are mentioned .

[0093] Firstly, they allow an automatic adj ustment of the kiln 2 , guaranteeing a firing of the ceramic articles BC in optimal conditions both in terms of performance , i . e . the quality of the ceramic products P obtained, and in terms of energy without the need for manual interventions , with consequent economic advantages .

[0094] Furthermore , the arrangement of the monitoring station 23 guarantees real-time control , without delay, considerably reducing the number of production rej ects .

Claims

C L A I M S1. A method for firing base ceramic articles (BC) , the method comprises the following steps: a conveying step, during which base ceramic articles (BC) are conveyed along a given path (T) , which extends from an input station (5) to an output station (6) through a firing chamber (4) of a kiln (2) for firing ceramic articles; said firing chamber (4) being divided into a pre-heating zone (PZ) , a firing zone (C) , arranged downstream of the pre-heating zone (PZ) along said given path (T) , and a cooling zone (R) , placed downstream of the firing zone (C) along said given path (T) ; a firing step, which is at least partially simultaneous with said conveying step and during which a heating system (8) , comprising at least a plurality of burners (9) arranged in series along at least a segment of said firing chamber (4) , and a cooling system (17) configured to lower the temperature of at least part of said firing chamber (4) , arranged at said cooling zone (R) and comprising at least one duct (18) for injecting cooling air into the firing chamber (4) , are operated to impose a given temperature on the base ceramic articles (BC) going through said firing chamber (4) so as to fire said base ceramic articles (BC) , gradually cool them and obtain ceramic products; a monitoring step, which is at least partially subsequent to the firing step, and during which a monitoring system (22) with automatic control, located at a monitoring station (23) , placed immediately downstream of the kiln (2) along said given path (T) analyses said ceramic products (P) leaving the kiln (2) and detects a possible densityunevenness and / or colour unevenness; an adjustment step, which is at least partially simultaneous with said firing step and during which a control unit (CU) adjusts in real time at least the operation at least of said heating system (8) and of said cooling system (17) of said kiln (2) as a function of the data detected during said monitoring step; said adjustment step comprising, in turn: a processing sub-step, during which the control unit (CU) processes the data obtained in said monitoring step to identify an operating condition of minimum consumption of the kiln (2) , which is associated with given operating parameters of the kiln (2) ; and an operation sub-step, during which said control unit (CU) controls the operation at least of said heating system (8) and of said cooling system (17) ) so as to impose said given operating parameters of the kiln (2) inside said firing chamber (4) .

2. The method according to claim 1, wherein: said firing chamber (4) of said kiln (2) is divided into a pre-heating zone (PZ) , a firing zone (C) , which is arranged downstream of the pre-heating zone (PZ) along said given path (T) , and a cooling zone (R) , which is arranged downstream of said firing zone (C) along said given path (T) ; said plurality of burners (9) of said heating system (8) are divided into at least two independent groups (10a, 10b) of burners (9) , a first group (10a) of burners (9) arranged at said pre-heating zone (PZ) and a second group (10b) of burners (9) arranged at said firing zone (C) ; during said operation sub-step, at least the flow rate of the oxidizer fed to said first group (10a) of burners (9)is adjusted, when, during said monitoring step, a density unevenness and a colour unevenness are detected within the ceramic product (P) .

3. The method according to claim 1, wherein: said firing chamber (4) of said kiln (2) is divided into a pre-heating zone (PZ) , a firing zone (C) , which is arranged downstream of the pre-heating zone (PZ) along said given path (T) , and a cooling zone (R) , which is arranged downstream of said firing zone (C) along said given path (T) ; said plurality of burners (9) of said heating system (8) are divided into at least two independent groups of burners (9) , a first group (10a) of burners (9) arranged at said pre-heating zone (PZ) and a second group (10b) of burners (9) arranged at said firing zone (C) ; during said monitoring step, an analysis of the tone of said ceramic products (P) is also carried out in order to detect any tone defects by comparison with standard tone data; during said operation sub-step, at least the flow rate of the oxidizer fed at least to said second group (10b) of burners (9) is adjusted, when, during said monitoring step, a superficial colour unevenness is detected on an outer surface of said ceramic product (P) and / or tone defects are detected, increasing the flow rate of the oxidizer to be fed to the burners (9) of the group (10b) of burners (9) .

4. The method according to claim 2 or 3, wherein said firing step comprises: a first feeding sub-step, during which a first feeding system (11) feeds a fuel mixture, which comprises at least one first fuel, to each one of said groups (10a, 10b, 10) of burners (9)independently of one another, and a second feeding sub-step, during which a second feeding system (13) feeds an oxidizing mixture to each one of said groups (10a, 10b, 10) of burners (9) independently of one another; during said monitoring step, a processing unit generates a first warning signal each time a ceramic product (P) having a density unevenness is detected and a second warning signal each time a ceramic product (P) having a colour unevenness is detected; during said adjustment step (in particular, during said operation sub-step) , said control unit (CU) in connection to said processing unit commands said second feeding system (13) to reduce the flow rate of oxidizer fed to said first group (10a) of burners (9) in said feeding sub-step, until it receives said first warning signal, and to increase the flow rate of oxidizer fed at least to said first group (10a) of burners (9) , once it receives said first warning signal, and / or to reduce the flow rate of oxidizer fed to said second group (10b) of burners (9) in said feeding sub-step, until it receives said second warning signal, and to increase the flow rate of oxidizer fed at least to said second group (10a) of burners (9) , once it receives said second warning signal.

5. The method according to any one of the preceding claims, wherein: during said monitoring step, an analysis of the shape and / or size of said ceramic products is also carried out in order to detect any size and / or shape defects; during said adjustment step, the control unit (CU) controls the operation of the heating system and / or of the cooling system also based on the detected size and / or shape defects .

6. The method according to any one of the preceding claims, wherein: during said conveying step, the base ceramic articles (BC) are conveyed along said given path (T) on different conveying planes parallel to one another at different heights ; during said monitoring step, all the ceramic products leaving the kiln (2) through the various conveying planes are analysed; and the method comprises at least one analysis step, which is at least partially prior to the adjustment step and during which the monitoring data of the ceramic products (P) leaving the kiln (2) through the various conveying planes are compared with one another in order to assess, based on the distribution of the defects, whether there are areas of the kiln (2) that are critical from the point of view of the firing conditions and, if there are any, how they are arranged; and during the adjustment step, the control unit (CU) adjusts the operation at least of the heating system (8) as a function of the data assessed in said analysis step.

7. The method according to any one of the preceding claims, wherein: the control unit (CU) comprises a memory containing a programming of the interventions, said programming comprising, in turn: a plurality of possible defects classified by order of increasing priority and which associates an intervention instruction with each one of said defects ; during said adjustment step, said control unit (CU) compares the data obtained in said monitoring step with thepossible defects contained in said programming to verify whether and how many of the classified defects are detected in each ceramic product (P) and executes the intervention instruction corresponding to the defect with the highest order of priority among those found in said monitoring step.

8. The method according to any one of the preceding claims, wherein said monitoring step is carried out by an automatically controlled monitoring system (22) .

9. An apparatus (1) for firing base ceramic articles (BC) with automatic adjustment, the apparatus comprises: a conveyor device (3) for conveying the base ceramic articles (BC) along a given path (T) , which extends through a firing chamber (4) from an input station (5) to an output station (6) ; said firing chamber (4) being divided into a pre-heating zone (PZ) , a firing zone (C) , arranged downstream of the pre-heating zone (PZ) along said given path (T) , and a cooling zone (R) , arranged downstream of the firing zone (C) along said given path (T) ; a kiln (2) , which is configured to fire the base ceramic articles (BC) and obtain ceramic products (P) , def ines / delimits said firing chamber (4) and comprises, in turn: a heating system (8) , which is provided, in turn, with a plurality of burners (9) arranged in series along at least a segment of said firing chamber (4) and each configured to burn a combustion mixture comprising a fuel mixture and an oxidizer to impose a given temperature on said base ceramic articles (BC) going through said firing chamber (4) , and a cooling system (17) arranged at said cooling zone (R) , comprising at least one duct (18) for injecting cooling air into the firing chamber (4) , and which can be operated to lower the temperature at least part of said firing chamber(4) ; a monitoring system (22) with automatic control arranged along said given path (T) , immediately out of said kiln (2) , and configured to analyse said ceramic products (P) leaving the kiln (2) in order to detect any density unevenness and / or colour unevenness; a control unit (CU) configured to adjust in real time the operation of said heating system (8) and of said cooling system (17) as a function of the data detected by the monitoring system (22) ; said control unit (CU) being configured to process the data obtained in said monitoring step so as to identify an operating condition of minimum consumption of the kiln (2) , which is associated with given operating parameters of the kiln (2) ; and to control the operation of at least said heating system (8) and said cooling system (17) so as to impose said given operating parameters of the kiln (2) within said firing chamber (4) .

10. The apparatus (1) according to claim 9, wherein: said firing chamber (4) is divided into a pre-heating zone (PZ) , a firing zone (C) , which is arranged downstream of the pre-heating zone (PZ) along said given path (T) , and a cooling zone (R) , which is arranged downstream of said firing zone (C) along said given path (T) ; said plurality of burners (9) of said heating system (8) are divided into at least two independent groups (10a, 10b) of burners (9) , a first group (10a) of burners (9) arranged at said pre-heating zone (PZ) and a second group (10b) of burners arranged at said firing zone (C) ; said heating system (8) further comprises a first feeding device (11) , which is configured to feed a fuelmixture, which comprises at least one first fuel, to each one of said groups (10a, 10b) of burners (9) and is provided with at least one first electronically controlled flow adjustment element (12) for each one of said groups (10a, 10b) of burners (9) , and a second feeding device (13) , which is configured to feed an oxidizing mixture to each one of said groups (10a, 10b) of burners (9) and is provided with at least one second electronically controlled flow adjustment element (14) for each one of said groups (10a, 10b) of burners (9) ; said cooling system (17) comprises at least one air generator (19) configured to generate a cooling air flow and at least one duct (18) configured to inject said cooling air flow into said cooling zone (R) and at least one suction system (20) to suck air from inside said firing chamber (4) ; and said control unit (CU) is configured to control said first and second electronically controlled flow adjustment elements (12, 14) to vary the flow rate of oxidizer or fuel mixture to be fed to said burners (9) and to control said air generator (18) and / or said suction system (19) as a function of the data detected by said monitoring system (21) .

11. The apparatus (1) according to claim 10, wherein: said cooling system (17) comprises at least one flow distribution element arranged along said duct (18) and configured to adjust the distribution of the emission of the cooling air flow inside the firing chamber (4) (in particular, crosswise to said firing chamber (4) ) ; and said control unit (CU) being configured to also control the operation of said distribution element as a function of the data detected by said monitoring system (22) .

12. The apparatus (1) according to any one of the claims from 9 to 11, wherein said monitoring system (22) comprises at least one emitter (26) configured to emit a radiation beam onto an outer surface (S) of each ceramic product (P) which advances at said monitoring station (23) and at least one reader configured to capture at least one image of the ceramic product (P) crossed by said radiation beam and assess a possible density unevenness based on an analysis of said image captured by said reader.

13. The apparatus (1) according to any one of the claims from 9 to 11, wherein said monitoring system (22) comprises a robotic arm configured to make, on a sample basis, a fracture in a ceramic product (P) leaving the kiln (2) and a viewing sensor configured to extract an image of said ceramic product (P) at said fracture and analyse the image by means of graphic analysis software in order to detect a possible colour unevenness.

14. The apparatus (1) according to any one of the claims from 9 to 13, wherein said monitoring system (21) comprises at least one further detector (27) configured to detect any tone defects and / or shape defects and / or size defects of each ceramic product (P) leaving said kiln (2) ; in particular, it comprises at least two further detectors (27) , one configured to detect any shape and / or size defects of each ceramic product (P) leaving said kiln (2) and another one configured to detect any tone defects of each ceramic product (P) leaving said kiln (2) .

15. The apparatus (1) according to any one of the claims from 9 to 14, wherein the control unit (CU) comprises a memory containing a programming of the interventions, said programming comprising, in turn: a plurality of possibledefects classi fied by order of increasing priority and which associates an order of priority and an intervention instruction with each one of said defects ; said control unit ( CU) being configured to compare the data obtained from said monitoring system ( 22 ) with the possible defects contained in said programming to veri fy whether and how many of the classi fied defects are detected in each ceramic product ( P ) and to execute the intervention instruction corresponding to the defect with the highest order of priority .

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