GB2119080A

GB2119080A - Burner having combustion air preheating

Info

Publication number: GB2119080A
Application number: GB08311160A
Authority: GB
Inventors: Giordano Giavelli; Dario Carraroli
Original assignee: Officina Meccanica Giavelli SpA; CARFER Srl
Current assignee: Officina Meccanica Giavelli SpA; CARFER Srl
Priority date: 1982-04-23
Filing date: 1983-04-25
Publication date: 1983-11-09
Also published as: ES8403599A1; DE3313370A1; IT1159293B; GB8311160D0; ES521747A0; IT8246824A0; BR8302116A

Abstract

A burner, particularly for ceramic firing kilns, having combustion air preheating, comprises a combustion chamber 3 to which are connected a fuel nozzle 20 and an annular combustion- air chamber 26, which is disposed in surrounding relation with the nozzle 20. A finned annular preheating chamber 10 surrounds the combustion chamber 3 and the combustion air flows through this preheating chamber before it enters the annular combustion- air chamber 26 so that the air is preheated. <IMAGE>

Description

SPECIFICATION Burner having combustion air preheating For tile production in the ceramics industry, firing kilns are widely used comprising a horizontal tunnel along which the material is passed, and in the side walls of which there is disposed a plurality of burners arranged to create and maintain in the tunnel the necessary temperature for correct material firing.

These burners can be gas, liquid gas, oil or even coal fired.

Known burners of this type, which are not only suitable for the ceramics industry but also for other industrial sectors, comprise a tubular member in which a nozzle is coaxially inserted for feeding the fuel which, as stated, can be gaseous, liquid or solid.

Said tubular member is also provided internally at its front with a constricted portion which acts as the combustion chamber, and against the rear mouth thereof there rests a transverse baffle which is rigid with said nozzle and has a diameter greater than the diameter of the nozzle body.

In this manner, between said tubular member and nozzle body there is formed an annular chamber which is fed with combustion air and opens into the combustion chamber by way of a circumferential set of through bores provided in said transverse baffle external to the nozzle body. The fuel is fed into said combustion chamber through convenient apertures provided centrally in said baffle.

During the operation of the aforesaid burners, their head, ie the metal part surrounding the combustion chamber, reaches a high temperature which also propagates along the tubular body.

Consequently, there is a considerable dispersion of heat into the surrounding environment, this heat not being utilised for firing the material, which therefore requires a greater fuel consumption, with economic burdens on the kiln operation and finished product cost which are not indifferent.

Finally, it should be noted that because of the large number of burners present in a ceramic kiln, the considerable quantity of heat transmitted to the environment creates some discomfort to the kiln operators, particularly during summer months.

The present invention provides a burner able to alleviate the aforesaid drawback, within the framework of a simple and rational constructional design.

The fundamental idea on which the invention is based is to use the combustion air directed towards the burner to recover the heat which disperses about the combustion chamber, and to then feed the air heated in this manner into this latter.

In this manner, in the first place the head is constantly cooled, so preventing dispersion of heat into the environment, and in the second place the burner efficiency is improved or increased by virtue of the higher combustion air temperature.

This is attained according to the invention by providing a preheating chamber surrounding the combustion chamber, and through which the combustion air circulates before reaching its own annular chamber, which is provided between said tubular member and nozzle body.

In order to improve said heat recovery, head cooling or combustion air preheating, finning is provided in the preheating chamber to considerably increase the heat transfer surface.

Finally, a valve member for adjusting the hot combustion airthroughput is provided in the connection which exists between said annular and preheating chambers.

These and further merits and constructional characteristics of the invention will be more apparent from the detailed description given hereinafter with reference to the Figures of the accompanying drawings, which illustrate one particular and preferred embodiment thereof by way of non-limiting example.

Figure 1 is a partial longitudinal section through a burner according to the invention, of the type for gaseous fuels.

Figure2 is a section on the line ll-ll of Figure 1.

Figure 3 is a plan projection in the direction A of Figure 1.

As stated heretofore, the burner illustrated is of the type particularly suitable for gaseous fuels, this definition being necessary by virtue of the fact that the characterising elements of the invention do not change with changing fuel.

In this respect, in the case of liquid or solid fuels such as fuel oil or coal, it is only the nozzle feeding the fuel to the combustion chamber which changes in the burner concerned.

Said Figures, and in particular Figure 1, show an annular head 1 provided at its rear with a connection flange 2 for mounting the device according to the invention on to a kiln wall by known means.

The head 1 is provided centrally with a coaxial through bore 3 which constitutes the combustion chamber of the device according to the invention.

This combustion chamber is slightly flared downstream where at its end it comprises a mouth 4 with a very pronounced concordant flare. A fire mouth, not shown, constructed of a suitable material and designed to receive the hot products of combustion for successively feeding them into the kiln, is intended to be disposed in known manner as a direct extension of the combustion chamber 3.

On the same side as the flange 2, and concentric to the combustion chamber 3, the head 1 comprises a circumferential cavity 5, of which the maximum depth is substantially three quarters of the combustion chamber length.

From the base of this cavity 5 there branch two concentric circumferential ribs or fins 6, of which the free edges are coplanar with the outer face of the flange 2.

These fins, which constitute two heat transfer members for cooling the head 1, can vary both in number and size.

A cyathiform flange 8 is fixed to the flange 2 of the head 1 by four equidistant screws 7 (Figures 2 and 3), and branches from a coaxial tubuler member 9.

At its downstream end, this latter comprises a constriction 90 which perfectly mates with the wall of the combustion chamber 3.

Said cyathiform flange 8 and constriction 90 provide an annular channel which is disposed in front of the circumferential recess 5, and which in combination with this latter defines an annular preheating chamber 10 for the combustion air.

The cyathiform flange 8 comprises a first aperture 11 into which a longitudinal conduit 12 rigid with the tubular member 9 fits.

The upstream of this latter is provided with a connector 13 for connecting the burner to the normal combustion air feed means.

In a diametrically opposing position, said cyathiform flange 8 comprises a second aperture 14 into which a longitudinal channel 15 rigid with the tubuler member 9 fits.

The downstream end of the channel 15 is provided with a transverse bore through which a pin 16 is inserted with an accurate fit and has its free threaded end screwed into a respective threaded through bore provided in the tubular member 9.

The pin 16 is provided with a coaxial cavity 17 which communicates with the channel 15 by way of a radial passage 18.

Finally, said pin 16 is provided with a hexagonal key seat 19 to enable the quantity of hot combustion air fed into the burner to be adjusted in order to optimise combustion.

It is apparent that said adjustment depends on the extent to which the radial passage 18 is closed by the outerwall ofthechannel 15.

It is also apparent that the same adjustment can be obtained by a threaded pin screwed into the wall of the channel 15 and having a shaped, for example hemispherical or frusto-conical, end arranged for insertion into a through bore provided in the tubular member 9.

A nozzle 20 is coaxially inserted into the tubular member 9, and emerges from said tubular member 9 where it comprises a connector 21 for its connection to normal fuel feed means.

The nozzle 20 is fixed in the tubular member 9 by three equidistant screws 23.

The rear and front ends of the nozzle 20 are provided respectively with an enlargement 24 and a transverse disc 25 which exactly mate with the mouth and with the constriction 90 of the tubular member 9.

In this manner, between this latter and the nozzle 20 there is defined an annular chamber 26 for coliecting the hot combustion air directed towards the combustion chamber 3.

The connection between the annular chamber 26 and the combustion chamber 3 is made by a circumferential series of inclined passges 27 provided in that part of the disc 29 which juts beyond the body of the nozzle 20.

The fuel however is fed into the combustion chamber 3 through longitudinal bores 28 provided in the central portion of the disc 25.

In this manner, the combustion air and fuel mix in the combustion chamber 3 where they ignite.

The operation of the device according to the invention is apparent from the foregoing description and a simple examination of the accompanying Figures.

It need only be stated that the advantageous inclusion of the finned toroidal chamber 10 enables the head 1 to be continuously cooled, so preventing dispersion of heat into the environment, and using this recovered heatto preheat the combustion air in order to improve combustion and thus increase the burner efficiency, with consequent fuel saving.

The invention is not limited to the single embodiment heretofore described, and modifications and improvements can be made thereto without leaving the scope of the invention, the fundamental characteristics of which are summarised in the following

Claims

claims. CLAIMS

1. A burner having combustion-air preheating, comprising a fuel nozzle and a tubular member disposed one within the other to form a combustionair chamber therebetween, said combustion-air chamber and fuel nozzle opening into a combustion chamber, a preheating chamber, having heat transfer surfaces, surrounding the combustion chamber and connected to the combustion air supply and to the combustion-air chamber, respectively, by way of two passageways which are disposed on the outside of the tubular member, and a valve member for adjusting the quantity of hot combustion air delivered to the combustion chamber disposed between the second of said two passageways and the combustion-air chamber.

2. A burner as claimed in claim 1, wherein the preheating chamber also surrounds at least the terminal part of the tubular member which is in contact with the wall of the combustion chamber.

3. A burner as claimed in claim 1, wherein the heat transfer surfaces comprise fins projecting from walls defining the combustion chamber.

4. A burner as claimed in claim 1, wherein the valve member comprises an adjustable threaded pin which is inserted into a bore provided in the tubular member and which connects said second passageway to the combustion-air chamber.

5. A burner having combustion air preheating, constructed substantially as hereinbefore described with reference to the accompanying drawings.