US2663559A - Combustion of liquid fuel - Google Patents

Description

Dec. 2 2, 1953 F. J. BATTERSHILL COMBUSTION OF LIQUID FUEL Filed April 24, 1951 Patented Dec. 22, 1953 COMBUSTION OF LIQUID FUEL Frederick James Battershill, Woodlands, South Croydon, England; Vivien Louise Lilian Battershill, sole cxecutrix of Frederick James Battershill, deceased Application April 24, 1951, Serial No; 222,560

Claims priority, application Great Britain June 28, 1950 Claims.

This invention relates to a method of burning liquid or gaseous fuel in such a manner that the temperature in the zone of combustion is lower and more uniform than that obtained by the usual methods of combustion. Such comparatively low temperatures are required in many processes in which, while the application of heat from a furnace is needed, the material or container to be heated must not be allowed to reach too high a temperature. As examples of such processes there may be mentioned annealing and the galvanising of iron articles. In the case of galvanising, the bath or container for the spelter requires careful temperature control, since the bath deteriorates rapidly if its temperature even slightly exceeds a critical value.

The invention consists in one aspect in a method of burning gaseous or liquid fuel wherein the fuel is introduced into a combustion chamber in the form of a gas, vapour or spray, which forms are referred to generically in the appended claims as the atomised form, and the greater part of the air for combustion is introduced into the combustion chamber, at a point remote from that at which the fuel is introduced, in admixture with a substantial proportion of an inert gas so that combustion, although complete, is retarded and distributed difiusely throughout the major part of the combustion chamber. The inert gas may conveniently consist of a part of the hot combustion products which is diverted from the stream of products flowing to the stack.

It is advantageous to introduce the combustion air through an injector nozzle and to entrain and mix the inert gas with the injecting stream of air by the action of the injector nozzle. By this means it is possible to maintain the correct proportion of air and inert gas automatically in spite of variations in the output of the furnace. The furnace may advantageously be so designed that the duct through which the combustion products flow from the combustion chamber to the stack passes the point of entry of the com bustion air into the chamber, the air being injected into the chamber through an injector nozzle situated in this duct.

In another aspect, the invention consists in apparatus for carrying out the method of combustion described above, which comprises a combustion chamber, means for introducing fuel into the chamber in the form of a gas, vapour or spray, an air inlet for combustion air remote from the said means, a duct passing the said inlet for leading combustion products from the combustion chamber to the stack, and an injector nozzle which communicates with a source of compressed air and is situated in the said duct and is arranged to inject a mixture of air and entrained combustion products into the combustion chamber.

Where it is undesirable to expose the container or material to be heated directly to the combustion zone, the latter may be separated from the former by a wall or partition which is spaced from the said container or material, the space between the container or material and the wall having access at one end to the combustion chamber at a point remote from the air inlet and communicating at the other end with a duct which passes the air inlet and leads to the stack, the injector nozzle for the combustion air being placed in this duct.

The invention is especially advantageous when applied to the heating of galvanising baths, and such application is illustrated by way of example by the accompanying drawing, which is a vertical section through part of a galvanising bath and the furnace for heating it.

The drawing shows that part of the galvanising bath which lies to the right of a vertical plane AA. The bath has a vertical wall I and a furnace 2 adjoins this wall. A similar furnace adjoins the left-hand Wall of the bath, which is not shown in the drawing. The furnace 2 comprises a row of several combustion chambers 3 arranged along the length of the wall I.

Each combustion chamber 3 is provided with a fuel injection nozzle 4 which, when liquid fuel is used, may be of any good atomising type. The

1 fuel is deliveredthrough a pipe 5 regulated by a valve 6. At the 'endof the chamber 3 opposite to the burner 4 is an air inlet furnished with an injector nozzle 14 provided with a throat 1. Air for combustion is supplied to this nozzle under pressure through a pipe 8. The interior of the chamber 3 is separated from the wall I of the galvanising bath by a partition wall 9 and a space 10, the latter having access to the chamber 3 by way of a gap at the top of the wall 9. The wall 9 is shown as a heat-resisting steel plate, but may be made of a refractory material if required.

The lower end of the space I0 communicates with a duct II which passes the air inlet of the chamber 3 and leads to the stack l2. The nozzle 14 and also the pipe 8 are situated in the duct I I. The outer wall of the combustion chamber 3 is provided with a lighting hole Hi.

In operation the air for combustion is preheated by the combustion products as it passes through the pipe 8, which acts as a recuperator. On issuing through the nozzle M, the air en trains and mixes with a portion of the hot combustion products flowing into the duct ll. This mixture of air and combustion products enters the lower end of the combustion chamber and supports the combination of the fuel introduced through the nozzle 4. The proportoin of air and combustion products in the mixture entering the chamber depends on the dimensions of the nozzle I4 and throat I and is so adjusted that combustion, although complete, is retarded and distributed diffusely throughout practically the whole of the chamber 3, with the result that the temperature in the chamber is-substantially lower and more uniform than would be the case if the fuel were burnt in the 'usualmanner with air unmixed with an inert gas and introduced near the nozzle 4. The combination products pass from the chamber 3 over the top of the wall 9 into the space If! and flow down through this space into the duct I I. Part of the products flows thence to the stack 12 and part is entrained in the throat I by the combustion air issuing from the nozzle M, to be recirculated through the combustion chamher. The output of the furnace has to be varied within wide limits according to the rate at which articles are being dipped in the galvanising bath. The output is controlled by means of the burner control 6 and by regulating the flow of air to the nozzle M by means of a valve (not shown). Since the quantity of combustion products entrained by the combustion air is proportional to the mass of air flowing through the nozzle [4, the correct proportion of air and combustion products is maintained over a range of furnace outputs.

By means of the method of firing described, it is possible to maintain the galvanising bath at a steady temperature sufficiently high to carry out the galvanising process but not high enough to cause rapid deterioration of the bath.

It will also be noted that the construction of the furnace is such that the maximum heat input is at the top of the bath, where the removal of heat is also at a maximum. Furthermore, the construction is compact, with the advantage that the distance from the wall I to the exterior of the furnace 2 is small, thus facilitating the dipping operations. Moreover the heat capacity of the furnace setting is low. A further advantage, which flows from the fact that there is no longitudinal flow from one combustion chamber to another perpendicular to the plane of the drawing, lies in the facility with which any one of the chambers can be put out of service for inspection and repair of the bath or setting without interrupting the operation of the remaining chambers.

I claim:

1. The method of firing a galvanising bath so that the wall thereof is subjected to a moderate and uniform heat over the whole of its surface,

which comprises introducing fluid fuel is atomised form and with a small amount of air into a combustion chamber, introducing the greater part of the air for combustion of said fuel into said combustion chamber at a point remote from that at which the fuel is introduced, through an injector located outside the combustion chamber and arranged to entrain inert gas so that the said greater part of the combustion air is admixed with a substantial proportion of inert gas whereby combustion, although complete, is retarded and distributed difiusely throughout the major part of the combustion chamber and causing the products of said combustion to flow over a wall of the galvanising bath.

2. The method of firing a galvanising bath according to claim 1, wherein the inert gas entrained by the injector consists of combustion products diverted from the stream of products flowing to the stack.

3. The method according to claim 2 wherein the combustion products are caused to flow in the direction from the top to the bottom of the galvanising bath.

4. In combination with a galvanising bath, a combustion chamber, means for introducing fuel in 'atomised form into a part of said chamber, a stack, a duct for the discharge of combustion products to said stack, and an injector nozzle which is located in said duct but outside said chamber at a point removed from the part of the said chamber receiving atomised fuel, which communicates with a source of air and which is arranged to inject a mixture of air and entrained combustion products into the combustion chamber, the products of combustion being caused to fiow over a wall of the galvanising bath before passing to the said duct.

5. The combination of apparatus claimed in claim 4, wherein the combustion chamber is separated from the galvanising bath wall by a narrow space communicating with the said chamber and with the duct and serving as a passage for combustion products leaving said chamber.

FREDERICK JAMES BATTERSHILL.

References Cited in the file of this patent UNITED STATES PATENTS FOREIGN PATENTS Country Date Great Britain July 8, 1920 Great Britain Nov. 23, 1933 France Feb. 7, 1951 Number Number

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