Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F27—FURNACES; KILNS; OVENS; RETORTS
  • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
  • F27B9/00—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity
  • F27B9/30—Details, accessories, or equipment peculiar to furnaces of these types
  • F27B9/40—Arrangements of controlling or monitoring devices
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B28—WORKING CEMENT, CLAY, OR STONE
  • B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
  • B28B11/00—Apparatus or processes for treating or working the shaped or preshaped articles
  • B28B11/24—Apparatus or processes for treating or working the shaped or preshaped articles for curing, setting or hardening
  • B28B11/243—Setting, e.g. drying, dehydrating or firing ceramic articles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B28—WORKING CEMENT, CLAY, OR STONE
  • B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
  • B28B17/00—Details of, or accessories for, apparatus for shaping the material; Auxiliary measures taken in connection with such shaping
  • B28B17/0063—Control arrangements
  • B28B17/0072—Product control or inspection
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F27—FURNACES; KILNS; OVENS; RETORTS
  • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
  • F27B9/00—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity
  • F27B9/30—Details, accessories, or equipment peculiar to furnaces of these types
  • F27B9/36—Arrangements of heating devices
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F27—FURNACES; KILNS; OVENS; RETORTS
  • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
  • F27D19/00—Arrangements of controlling devices
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F27—FURNACES; KILNS; OVENS; RETORTS
  • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
  • F27D21/00—Arrangements of monitoring devices; Arrangements of safety devices
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D11/00—Process control or regulation for heat treatments
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F27—FURNACES; KILNS; OVENS; RETORTS
  • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
  • F27D19/00—Arrangements of controlling devices
  • F27D2019/0028—Regulation
  • F27D2019/0056—Regulation involving cooling
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F27—FURNACES; KILNS; OVENS; RETORTS
  • F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
  • F27D21/00—Arrangements of monitoring devices; Arrangements of safety devices
  • F27D21/02—Observation or illuminating devices

Definitions

• the invention relates to kilns for ceramic tiles, and in particular to the product quality management thereof.
• tunnel kilns Success during the firing stage of tiles in kilns known as tunnel kilns depends almost exclusively on adherence to the longitudinal temperature curve maintained internally of the kiln throughout the transversal section thereof.
• the term longitudinal curve means the curve of the temperatures in the advancement direction of the material, i.e. in a parallel direction to the kiln axis.
• the kilns to which reference is made comprise a roller plane for material transport, located in a tunnel structure having lateral walls, as well as two series of burners directed towards the centre of the kiln and located in the lateral walls over the whole kiln length, one series being aligned above the roller plane and another series being aligned below the roller plane, where the burners of each series comprise first burners, known as radial burners, prevalently for heating the zones close to the lateral walls, alternated with second burners, known as axial burners, for heating prevalently the central zones of the kiln.
• rapid cooling means comprising variously-oriented nozzles which dispense pressurised cold air generated by means for generating pressurised air, such as axial or radial ventilators.
• All product quality parameters depend on the longitudinal temperature curve, such as for example the planarity of the tiles exiting the kiln and the regularity of the tile dimensions.
• the prior art describes processes which enable the longitudinal temperature curve to be kept constant automatically, even in the presence of discontinuity in the load, with the aim of maintaining the product quality within commercially acceptable limits.
• the prior art processes intervene retroactively on the temperature curve by acting on the burners which heat up the kiln; i.e. they intervene in the tract of the kiln which fires the tiles upon a defect being found in the product exiting the kiln.
• the aim of the present invention is to provide a process and an apparatus for retroactively controlling a tunnel kiln according to the quality of products as checked on exiting the kiln.
• the tile tends to shrink, increasingly so as the firing temperature rises; this shrinkage is due to the development of gases and to the closing-up of the interstices during partial sinterisation, and the control of the temperature in the transversal section of the kiln gives good results in maintaining the dimensions of the tile at a commercially acceptable level, even in proximity of the kiln walls.
• the planarity defects revealed at exit from the kiln occur also and prevalently in the rapid cooling zone, and can be imputed to a differentiated dimensional diminution of the material in the portions of the tile which are close to the upper surface and lower surface thereof.
• the invention therefore intervenes on the dilation coefficient of the material in order to have an effect on the tile planarity.
• the process of the invention includes experimentally determining the optimal longitudinal curve of the temperature CT 0 of firing in accordance with the material used and also according to the dimensions and the quality of the tiles in each batch to be fired.
• the kiln thermal plants are set with respect to both the heating and the cooling functions.
• the following are monitored internally of the kiln, at a discrete series of significant points: the temperature T
• deviations ⁇ T of the monitored temperatures T ⁇ s ⁇ from the stored optimal curve TCo are memorised and sent on to the processor controlling the kiln, which makes a first correction of the thermal plants in order to maintain the values within an acceptable field.
• first means for controlling planarity and second means for controlling dimensions are provided.
• the detected data is compared with standard memory-stored data typical of each type of product, and when the comparison shows a deviation from a predefined interval, the type of deviation is signalled to a processor which on the basis of its own program then modifies supply to the burners and the means for generating cooling air which are influencing the deviation.
• the processor is provided with at least a first memory containing the most common standard defects in tiles, statistically detected; a second memory containing the corrections of the firing and cooling temperatures for reducing any defect type; and a program for correlating the defects encountered with those stored in the first memory, and for rapidly commanding the burners and the means for generating pressurised air in order to achieve and adequate reduction in the detected defect, according to the data contained in the second memory.
• the apparatus of the invention comprises all the means necessary for enacting the activities making up the process. Brief description of the Drawings.
• figure 1 is a plan view of the kiln plane with the burners and the means for generating cooling air located above the roller plane
• figure 2 is a plan view of the kiln plane with the burners and the means for generating cooling air located below the roller plane. Best Mode for Carrying Out the Invention.
• the figures of the drawings show the roller plane of the kiln, denoted by 1 , on which the tiles advance from right to left in the figures.
• the roller plane Both above and below the roller plane are located known-type and axial-type burners 2, 20, 3 and 30, prevalently for heating the central zone of the kiln, and known-type radial-type burners 4, 40, prevalently for heating the zones proximal to the kiln walls.
• the burners are positioned facing the lateral walls of the kiln, and the burners on one wall are staggered with respect to the burners on the opposite wall.
• the axial-type burners 2, 20 close to the kiln entry are for pre-firing the tiles, while the burners 3, 30, 4 and 40 are for firing the tiles.
• the rapid cooling of the tiles starts downstream of the burners 4, 40, with an injection of cold air (room temperature) through nozzles facing towards the roller plane and arranged on two upper transversal manifolds 5 and 6, on two lower transversal manifolds 50 and 60, as well as on two longitudinal manifolds 70 parallel to the kiln axis and arranged below the roller plane.
• cold air room temperature
• Each of the manifolds is preferably connected to means for generating air which are independent of the means for generating of the other manifolds.
• the burners 2, 20, 3, 30, 4 and 40 are connected singly or in pairs to the central processor P (not illustrated) which governs the kiln and commands supply of the fuel and combustion air to each of them.
• the means for generating air of the manifolds 5, 50, 6, 60 and 70 are singly connected to the same processor P which also governs the operating pressure thereof.
• the sensors 11 and 11a of the temperature inside the kiln are located above the roller plane, respectively at the centre and in proximity of the walls thereof.
• the sensors 110 and 110a of the temperature internally of the kiln are located below the roller plane, respectively at the centre and in proximity of the walls thereof.
• the transversal lines of the tiles exiting the kiln are transferred in succession onto a transporter 8 having an axis which is perpendicular to the kiln axis, on which a single line of tiles 81 is formed.
• the first means 10 for controlling tile planarity defects are located above the transporter 8, and the second means 9 for controlling the dimensions, which are of known type, are also located above the transporter 8, and are also connected to the central processor P, to which they signal each defect encountered.
• the increase in flame temperature causes a reduction in the size of the piece.
• This defect is corrected by increasing the flame temperature in the radial burners 4, 40 both above and below the roller plane.
• This defect is corrected by reducing the flame temperature in the burners 4, 40.
• D Homogeneous concave shape - upwards-directed concavity. This defect is corrected by an intervention in the rapid cooling zone.
• the cooling air pressure is reduced in the manifolds 50 and/or 60 and increased in the manifolds 5 and/or 6.
• the flame temperature of burners 30 and 40, situated below the roller plane, is synergically increased while the flame temperature of the burners 3 and 4, situated above the roller plane, is reduced in the final firing zone.
• the flame temperature of the burners 20 and 30, situated below the roller plane is reduced in the pre-firing and start-firing zone, while the flame temperature of the burners 2 and 3 above the roller plane is increased.
• the pressure in the manifold 50 and/or 60, below the roller plane is reduced, and the pressure in the manifold 5 and /or
• manifold 50 and/or 60 pressures at the start of the rapid cooling zone are reduced from below, and manifold pressures 5 and/or 6 are increased from above.
• F Concave shape in the planes which are parallel to the rollers.
• manifold 50 and/or 60 pressure is reduced (from below) and manifold 5 and/or 6 pressure
• burner 20 flame temperature is reduced (below the roller plane) and burner 2 flame (above the roller plane) is increased by the same amount.
• burner 3 temperature above the roller plane is reduced at the start of the firing zone, while burner 3 and 4 temperature is increased at the end of the firing zone.
• the temperatures of the burners 30 is increased at the start of the roller plane (start-firing zone) and the temperatures of the burners
• burners 20 and 30 are increased in the pre-firing zone and start-firing zone below the roller plane, while the temperature of burners 2 and 3, above the roller plane, is lowered.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Ceramic Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Structural Engineering (AREA)
• Tunnel Furnaces (AREA)
• Furnace Details (AREA)
• Waste-Gas Treatment And Other Accessory Devices For Furnaces (AREA)
• Electric Stoves And Ranges (AREA)

Priority Applications (3)

Applications Claiming Priority (2)

Publications (1)

Family

ID=37852360

Family Applications (1)

Country Status (6)

Cited By (8)

Citations (3)

• 2006
  • 2006-01-26 IT IT000007A patent/ITRE20060007A1/it unknown
  • 2006-12-01 RU RU2008128554/03A patent/RU2406050C2/ru not_active IP Right Cessation
  • 2006-12-01 BR BRPI0620969-6A patent/BRPI0620969A2/pt not_active IP Right Cessation
  • 2006-12-01 WO PCT/EP2006/069231 patent/WO2007085317A1/en active Application Filing
  • 2006-12-01 CN CN2006800514225A patent/CN101360966B/zh not_active Expired - Fee Related
  • 2006-12-01 EP EP06830297A patent/EP1974173A1/en not_active Withdrawn

Patent Citations (3)

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