The present invention relates to a burner, usable in both the industrial and civil sector.
Burners are used in the ceramic industry, for example, inside the equipment for the heat treatment of ceramic products, such as kilns and dryers.
The burners of known type generally comprise a first tubular element, which defines a flow duct of a combustion fluid, a second tubular element arranged externally to the first tubular element, where the volume placed between them defines a flow duct of a combustive fluid, generally air, and a third tubular element arranged externally to the second tubular element and defining the outlet mouth of the flame of the burner itself.
In correspondence to the extremity of the first tubular element is arranged a combustion head, in correspondence to which the mixing occurs between the combustion fluid and the combustive fluid and the combustion of this mixture.
On the external surface of the second tubular element are defined a plurality of openings able to allow the flow of one part of the combustive fluid flowing along the relevant duct inside the gap defined between the second and the third tubular element.
The air flowing inside the duct defined between the first and the second tubular element is also called "primary air", as it participates directly in the combustion, while the air escaping from said openings and flowing between the second and the third tubular element, reaching the combustion head laterally, is defined as "secondary air".
These openings have in particular the function of allowing venting of any combustive fluid in excess, so as to avoid phenomena of flame detachment that might occur in case of the flow of combustive fluid reaching the combustion area with an excessive speed, causing the detachment of the flame and the consequent stop of the burner.
These burners of known type do have a number of drawbacks.
In particular, the burners on the market today do not allow to adjust the amount of combustive fluid which passes through the openings defined on the second tubular element, or the amount of secondary air which crosses the gap placed between the second and the third tubular element.
This considerably limits the maximum flow rate of the combustive fluid that can be sent to the burner in the pre-heating zones, since an excessive flow rate can not be disposed of.
The amount of combustive fluid that passes through these openings only depends on the load losses incurred along the path, thus making it difficult to manage the flame in the various areas of a ceramic kiln in which excesses of air different to one another are required. A burner having the features specified in the preamble of claim 1 is known from
The main aim of the present invention is to provide a burner which allows to adapt to the specific operating needs, by adjusting the flow rate of secondary air and, therefore, without resulting in the detachment of the flame.
Within this aim, one object of the present invention is to adapt the stoichiometric ratio, by adjusting the flow rate of secondary air, depending on the specific area of the ceramic kiln in which the burner is located.
One object of the present invention is to optimize the efficiency of the burner according to the specific operating needs.
Another object of the present invention is to avoid detachment of the flame in the pre-heating zones of a ceramic kiln and at the same time to reduce the firing cycles of the kiln itself.
Another object of the present invention is to provide a burner which allows to overcome the mentioned drawbacks of the prior art within the ambit of a simple, rational, easy and effective to use as well as affordable solution.
The above mentioned objects are achieved by the present burner according to claim 1.
Other characteristics and advantages of the present invention will become better evident from the description of a preferred, but not exclusive embodiment of a burner, illustrated by way of an indicative, but not limitative example in the accompanying drawings in which:
With particular reference to these figures, it is globally indicated by reference number 1 a burner according to the invention, usable for both civil and industrial applications.
The burner 1 comprises a body 2 having a first tubular element 3 defining a first duct 3a for the flow of a combustion fluid, a second tubular element 4 arranged externally to the first tubular element 3, where the volume placed between the first and the second tubular element 3 and 4 defines a second duct 4a for the flow of a combustive fluid, and a third tubular element 5 arranged externally to the second tubular element 4 and defining the outlet mouth 6 of the flame of the burner itself, where the volume interposed between the second and third tubular element 4 and 5 defines a gap 5a external to the second duct 4a.
The second tubular element 4 has a plurality of first openings 7 which allow the flow of the combustive fluid from the second duct 4a towards the gap 5a.
As already mentioned above, it is hereinafter referred to as "primary air" the air that passes through the second duct 4a and as "secondary air" the air that runs through the gap 5a.
The burner 1 also comprises at least a combustion head 8 associated with the body 2 and arranged in correspondence to the extremity of the first tubular element 3.
The combustion head 8 defines a combustion area 9 in correspondence to which the mixing occurs between the combustion fluid and the combustive fluid as well as the ignition of the flame.
More particularly, flame ignition means 10 are provided, such as, e.g., a pair of electrodes that pass through the second duct 4a and the extremities of which are arranged in correspondence to the combustion area 9.
As is known to the expert in the field, the first openings 7 are able to convey inside the gap 5a the amount of combustive fluid in excess, in particular in the pre-heating zones of a ceramic kiln, in order to avoid detachment of the flame that might occur in the event of the combustive fluid reaching the combustion area 9 with an excessive speed.
The third tubular element 5 therefore covers the outside of the first and the second tubular element 3 and 4 and contains the combustion head 8. The outlet mouth 6 defined by the third tubular element 5 is spaced away from the combustion head 8.
According to the invention, the burner 1 comprises at least a covering element 11 arranged externally to the second tubular element 4 and movable with respect to it to vary the flow section of the first openings 7.
The covering element 11 is then interposed between the second and the third tubular element 4 and 5.
Advantageously, the covering element 11 has a plurality of second openings 12 which can be superimposed to the first openings 7 as a result of the movement of the covering element 11 with respect to the second tubular element 4.
More in detail, the covering element 11 is movable between a closing configuration, wherein it obstructs the first openings 7 at least partially so as to partialize the amount of combustive fluid entering the gap 5a, and an opening configuration, wherein the second openings 12 are completely superimposed to the first openings 7 so as to allow the flow of the combustive fluid through the entire flow section of the first openings themselves, passing through at least one intermediate configuration between the closing configuration and the opening configuration. In the closing configuration, the flow section of the combustive fluid through the first openings 7 is minimum and increases as it moves close to the opening configuration.
Preferably, the covering element 11 has a tubular shape, is fitted externally to the second tubular element 4 and is movable in rotation with respect to the latter, the first and second openings 7 and 12 being angularly spaced from one another.
More particularly, the first and second openings 7 and 12 have the same angular distance between them, so that in the opening configuration each second opening 12 is superimposed to a respective first opening 7.
Suitably, the covering element 11 is movable in a continuous manner with respect to the second tubular element 4, so as to allow its positioning in a plurality of intermediate configurations.
Advantageously, the burner 1 also comprises locking means 13 of the angular position of the covering element 11 with respect to the second tubular element 4.
More in detail, the locking means 13 comprise at least a through hole defined on the covering element 11 and in which a locking element (not shown in the illustrations), such as a threaded element, is insertable in a removable manner and is able to rest against the external surface of the second tubular element 4.
The operation of the present invention, with specific reference to the use in a ceramic kiln, is as follows.
Depending on the area of the kiln in which the burner 1 is positioned and based therefore on the operating condition required, intervention is made on the covering element 11 in order to adjust the flow section of the first openings 7 and, consequently, the amount of primary air that reaches the combustion head 8.
More particularly, in the burners 1 arranged in correspondence to the pre-heating zones of a ceramic kiln the covering element 11 is positioned in the opening configuration, so as to let the greater amount of air as possible pass through the first openings 7 and, therefore, along the gap 5a.
In this way the flow rate of the combustive fluid that reaches the combustion head 8 is not excessive and such as to "tear the flame", thereby making only the amount of combustive fluid participate in the combustion sufficient for the ignition and maintenance of the flame itself.
More particularly, by placing the covering element 11 in the opening configuration a large amount of air may be sent inside the burner 1, but only the amount needed to ignite and maintain the flame is conveyed along the second duct 4a and the remaining part diverted inside the gap 5a.
The position of the covering element 11 is therefore modified according to the required needs in the specific area of the kiln in which the burner 1 is positioned and, therefore, according to the parameters one wishes to control, such as the size of the environment to be heated, the air-gas stoichiometric ratio and the geometry of the flame.
For example, during the firing phase of a ceramic article, whenever one wishes to minimize the firing cycle and maximize production, the covering element 11 is brought to the closing configuration, so that the flow rate of the combustive fluid is almost entirely sent to the combustion head 8.
Each time the covering element 11 is positioned in the configuration of interest its position must be secured with respect to the second tubular element 4 by means of the locking means 13, i.e. by inserting the locking element within the relevant hole made in the covering element itself.
In practice it has been observed how the described invention achieves the proposed objects and in particular the fact is underlined that the burner making the subject of the present invention allows to adjust the amount of combustive fluid which participates directly in the combustion according to the specific requirements of the case.
More in detail, by adjusting the position of the covering element with respect to the second tubular element, the amount of primary air reaching directly the combustion head and of the secondary air passing through the outer gap is adjusted accordingly.
This allows to prevent the flame from tearing in the pre-heating positions of the kiln and at the same time to optimize the production cycle in the firing step.
Furthermore, by making a high amount of air passing through the gap interposed between the second and the third tubular element, in particular in the pre-heating zones, a very long flame geometry is obtained, thus facilitating the removal of the so-called "black heart" present in ceramic articles.
The burner according to the invention therefore allows to adjust the flow rate of the combustive fluid which participates directly in the combustion so as to maintain it within the stoichiometric ratio or even much above the same as is required in the pre-heating zones of a ceramic kiln.
This flexibility of use allows to maximize the efficiency of the burner itself in all areas of a ceramic kiln, optimizing the flow rate of air that directly participates in the combustion, thus overcoming the construction and adjustment drawbacks of the burners known so far.
In particular, by making the pre-heating phase of a ceramic article more efficient, the evacuation of the drying residual water is speeded up, as well as of the water of reaction and of the carbonaceous substances, thereby reducing the duration of the firing cycle.
This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.