Batch kiln

Abstract

 An improved batch kiln comprises: a box-like structure (2) made of refractory-type material, which forms a thermal treatment chamber (4) provided with at least one opening for inserting and removing movable trolleys (5), adapted to constitute the bottom of the chamber (4), for conveying manufactured articles (S) to be treated, and with at least one corresponding closure door, the chamber (4) being associated with a system of burners and with a circuit for aspirating the fumes generated during the thermal treatment; a hermetic outer jacket (6), which is adapted to form an interspace (7) between the chamber (4) and the outside environment; a ventilation circuit, which is associated with the interspace (7); and first and second means (8, 9) for adjusting the pressures respectively inside the chamber (4) and inside the interspace (7), which interact with each other and are adapted to drive the aspiration and ventilation circuits and to differentiate the values of the pressures.

Description

[0001] The present invention relates to an improved batch kiln.

[0002] As it is known, the so-called batch kilns, i.e. kilns in which operation is interrupted in order to load and unload the material to be subjected to thermal treatment, are constituted by a box-like supporting structure which internally supports walls made of refractory material which delimit a chamber for the thermal treatment of the loaded material.

[0003] Said chamber is provided with one or more lateral openings for the entry and exit of movable trolleys made of refractory material, on which the products to be treated are conveyed, and with corresponding hermetic doors which close the openings during the operation of the kiln.

[0004] The trolleys are inserted in the chamber adjacent to each other and constitute the bottom wall of said chamber.

[0005] The chamber is equipped with a system of burners and with a system for aspirating and evacuating the combustion products which allow to create inside it the temperature, pressure and atmospheric conditions related to the thermal treatment to which the products loaded therein must be subjected.

[0006] These conventional kilns are not devoid of drawbacks, including the fact that they do not allow to modify the value assumed by the pressure of the atmosphere inside the chamber over a wide variability range and do not ensure hermetic containment of the pressurized gases generated during thermal treatment, which often contain toxic components and tend to escape through the walls of the chamber, polluting the surrounding environment.

[0007] Reverting to the first drawback, there is a very limited possibility to modify the methods of heat exchange (convection, conduction) between said atmosphere and the products loaded into the chamber in relation to the several steps of the intended thermal treatment (heating, firing, cooling) and to the transformations affecting said products.

[0008] The aim of the present invention is to eliminate the above-noted drawbacks of conventional kilns, by providing an improved batch kiln which allows to modify the value of the pressure of the atmosphere inside the thermal treatment chamber over a wide variability range, to modify the heat exchange methods in relation to the different steps in which said treatment is performed, to improve the exploitation of the energy potential of the combustion products, and to ensure the hermetic containment of the pressurized gases generated inside the chamber, limiting the pollution of the surrounding environment.

[0009] Within the scope of this aim, an object of the present invention is to achieve the intended aim with a structure which is simple, relatively easy to provide in practice, safe in use, effective in operation, and relatively low in cost.

[0010] This aim and this and other objects which will become better apparent hereinafter are achieved by the present improved batch kiln, comprising a box-like structure made of refractory-type material which forms a thermal treatment chamber provided with at least one opening for inserting and removing movable trolleys for conveying manufactured articles to be treated, said trolleys being adapted to constitute the bottom of said chamber, and with at least one corresponding closure door, said chamber being associated with a system of burners and with a circuit for aspirating the fumes generated during the thermal treatment, characterized in that it comprises a hermetic outer jacket adapted to form an interspace between said chamber and the outside environment, a ventilation circuit which is associated with said interspace, and first and second means for adjusting the pressures respectively inside the chamber and inside the interspace, which interact with each other and are adapted to drive said aspiration and ventilation circuits and to differentiate the values of said pressures.

[0011] Further characteristics and advantages of the present invention will become better apparent from the detailed description of a preferred but not exclusive embodiment of an improved batch kiln, illustrated only by way of non-limitative example in the accompanying drawing, wherein:
   Figure 1 is a schematic front view of a portion of a kiln according to the invention.

[0012] With reference to the figure, 1 generally designates an improved batch kiln, for example for the thermal treatment of ceramic manufactured articles, such as sanitary fittings S and/or the like.

[0013] The kiln 1 comprises a box-like structure 2 which internally supports walls 3 made of a refractory-type material and form a thermal treatment chamber 4.

[0014] An opening is formed in one of the walls 3 through which movable trolleys 5 for conveying the sanitary fittings S to be treated are inserted and removed from the chamber 4; a corresponding closure door, not shown for the sake of simplicity, is also provided.

[0015] The trolleys 5 constitute the bottom of the chamber 4, and said chamber is associated with a system of burners and with a circuit for aspirating the fumes generated during thermal treatment; both are not shown, since they are of a conventional type.

[0016] The kiln 1 further comprises a hermetic outer jacket 6 which forms an interspace 7 between the chamber 4 and the outside environment, first means 8 for adjusting the pressures inside the chamber 4 being adapted to drive the aspiration circuit, and second means 9 for adjusting the pressures inside the interspace 7 being adapted to drive a ventilation circuit which is associated with said interspace 7 and is not shown since it is of a conventional type.

[0017] The first and second adjustment means 8 and 9 interact with each other and are adapted to differentiate the values assumed by the pressures inside the chamber 4 and the interspace 7.

[0018] Conveniently, the jacket 6 comprises an opening for the passage of the trolleys 5 corresponding to the opening of the chamber 4 and being closed by an element which forms a hermetic seal.

[0019] The jacket 6 is constituted by a bell 10 which externally surrounds the box-like structure 2 and whose base perimeter is hermetically fixed to the ground 11, so as to ensure good hermetic retention of the atmosphere inside the interspace 7 and so as to seal the box-like structure 2.

[0020] Advantageously, the jacket 6 is made of refractory-type material or, alternatively, of metallic material; the door and/or the closure element are instead of the vertical or horizontal "guillotine" type and/or are provided with pneumatic locking jacks.

[0021] In an alternative embodiment of the kiln 1, the interspace 7 is provided inside the box-like structure 2.

[0022] The first adjustment means 8 comprise first means for detecting the values assumed by the pressure of the atmosphere inside the chamber 4, which are constituted by a first sensor 12 and first means 13 for transducing the sensed values, which communicate with the first sensor 12 and are connected to first means 14 for driving the aspiration circuit.

[0023] The second adjustment means 9 comprise second means for sensing the values of the pressure of the atmosphere inside the interspace 7, which are constituted by a second sensor 15 and by second means 16 for transducing the sensed values, which communicate with the second sensor 15 and are connected to second means 17 for driving the ventilation circuit.

[0024] The first and second transducer means 13 and 16 communicate with each other.

[0025] The operation of the invention is as follows: using P1 and P2 to designate generic values assumed by the pressures respectively inside the chamber 4 and inside the interspace 7, and using ΔP to designate the positive or negative difference to be set between the values P2 and P1, once the values P1 and P2 have been sensed, the second adjustment means 9 act on the ventilation circuit so as to produce the intended pressure differential between the chamber 4 and the interspace 7, i.e. so that P2 = P1 + ΔP.

[0026] In order to have an overpressure in the interspace 7 with respect to the chamber 4, positive ΔP, the ventilation circuit sends air into the interspace 7, e.g. through a variable flow-rate fan.

[0027] This avoids the escape of the gases present in the chamber 4; by acting on the aspiration circuit it is also possible to modify the values of P1 over a wide variability range, since said values can be compensated by means of P2.

[0028] The value of P1 can be increased (reduced) far more than it is currently possible with conventional kilns; this allows to modify, for an equal temperature, the methods and rates of heat exchange in relation to the type of thermal treatment to be performed and to the type of manufactured item loaded into the chamber 4.

[0029] The presence of the interspace 7 and the possibility to differentiate the pressure P2 with respect to the pressure P1 allow to create, inside the chamber 4, the operating conditions that are most adapted for the execution of the intended thermal treatment, leading to better exploitation of the energy potential of the kiln and to cost savings.

[0030] In practice it has been observed that the described invention achieves the intended aim and objects.

[0031] The invention thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims.

[0032] All the details may further be replaced with other technically equivalent ones.

[0033] In practice, the materials used, as well as the shapes and the dimensions, may be any according to requirements without thereby abandoning the scope of the protection of the appended claims.

[0034] The disclosures in Italian Patent Application No. MO2000A000070 from which this application claims priority are incorporated herein by reference.

[0035] Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly, such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.

Claims

1. An improved batch kiln, comprising a box-like structure (2) made of refractory-type material which forms a thermal treatment chamber (4) provided with at least one opening for inserting and removing movable trolleys (5) for conveying manufactured articles (S) to be treated, said trolleys (5) being adapted to constitute the bottom of said chamber (4), and with at least one corresponding closure door, said chamber (4) being associated with a system of burners and with a circuit for aspirating the fumes generated during the thermal treatment, characterized in that it comprises a hermetic outer jacket (6) which is adapted to form an interspace (7) between said chamber (4) and the outside environment, a ventilation circuit which is associated with said interspace (7), and first (8) and second means (9) for adjusting the pressures respectively inside the chamber (4) and inside the interspace (7), which interact with each other and are adapted to drive said aspiration and ventilation circuits and to differentiate the values of said pressures.

2. The kiln according to claim 1, characterized in that said jacket (6) comprises a passage opening for the passage of the trolleys (5) which corresponds to said opening of the chamber (4), and an element for hermetically closing said passage opening.

3. The kiln according to one or more of the preceding claims, characterized in that said jacket (6) is constituted by a bell (10) which externally surrounds said box-like structure (2) and whose base perimeter is hermetically fixed to the ground (11).

4. The kiln according to one or more of the preceding claims, characterized in that said interspace (7) is provided inside said box-like structure (2).

5. The kiln according to one or more of the preceding claims, characterized in that said bell (10) is made of a refractory-type material.

6. The kiln according to one or more of the preceding claims, characterized in that said bell (10) is made of a metallic-type material.

7. The kiln according to one or more of the preceding claims, characterized in that said first adjustment means (8) comprise first means (12) for sensing the pressure values of the atmosphere inside said chamber (4) and first means (13) for transducing the sensed values which are connected to first means (14) for driving said aspiration circuit.

8. The kiln according to one or more of the preceding claims, characterized in that said second adjustment means (9) comprise second means (15) for sensing the pressure values of the atmosphere inside said interspace and second means (16) for transducing the sensed values which are connected to second means (17) for driving said ventilation circuit.

Drawing