US3097835A - Heating of zinc ovens - Google Patents

Description

July 16, 1963 A. A. J. QUINTIN HEATING OF ZINC OVENS Filed April 21, 1961 I Sl I I i Q lilll United States atent 3,097,835 Patented July 16, 1963 free 3,097,835 HEATING OF ZINC OVENS Albert Andr Joseph Quintin, Overpelt, Belgium, assignor to Compagnie des Metaux dGverpeit-Lommel et tie Corphalie, S.A., Overpelt-lez-Neerpelt, Belgium Filed Apr. 21, 1961, Scr. No. iiMJlil Claims priority, application Great Britain June 14, W69 6 Claims. (Cl. 263--37) This invention relates to the heating of zinc ovens by means of liquid fuel,

For heating metallurgical furnaces with liquid fuel, use is generally made of extra-heavy liquid fuel, which is least expensive. Owing to its viscosity when cold, such liquid fuel has to be heated before it is introduced into the combustion chamber of the furnace, and is admitted in a finely-divided form obtained by pulverization by means of steam or air under pressure, or by means of mechanical pulverizing devices. For applying such a process, the furnace should have a combustion chamber of a capacity and shape such that at no moment shall any pulverized liquid fuel come into contact with the surfaces to be heated. Otherwise, a cracking takes place and carbon in a form difficult to burn, is deposited upon the surface of the furnace, on which it hardens; such hard deposits grow rapidly and disturb the passage of the flames and thus the good working of the furnace.

When the combustion chamber of the furnace has in at least one direction small dimensions, for instance when it is obstructed by the objects to be heated, as is the case for instance with zinc ovens with multiple retorts, which generally are heated by means of gas (producer gas, natural gas, etc.) the difficulty may be avoided more or less satisfactorily by gasifying the liquid fuel outside the cost of construction, and leads to losses of heat.

The present invention consists in a process for heating the furnace in apparatus in which it is subjected to high temperatures. Such an arrangement however increases zinc ovens having a plurality of rctorts with liquid fuel such as heavy fuel oil which consists in injecting thin, non pulverized jets of said fuel between the retorts so that under the combined effect of the contact with the incandescent gases and of the radiation of the hot sur faces the liquid fuel is totally vaporized before it can strike a solid surface and form carbonaceous deposits.

The vapours thus produced are inflamed and ensure by their combustion the heating of the combustion chamber. Such an arrangement avoids all gasifying arrangement outside the combustion chamber and consequently important losses of heat, excessive size. It represents a great simplification of plant and ensures a maximum yield of heat, since the totality of the heat contained by the fuel is liberated inside the combustion chamber where it is utilized.

Generally zinc ovens have horizontal retorts, are heated with producer gas or natural gas, and work with periodical reversal of the gas and air inlets. In such ovens the space between the retorts is small.

According to one feature of the present invention the liquid fuel is injected in a downward direction into the spaces between the vertical rows of retorts, preferably in the direction of a vertical plane passing through the uprights supporting the roof of the oven, where owing precisely to the presence of the upright, there is a space between the vertical rows of retorts which is just sufficient for such injection.

The diameter of the streams of liquid and the speed of their injection are such that the gasifying process is achieved at the level of the lower row of retorts and no liquid fuel reaches the floor of the zinc ovens, thus avoiding its cracking and all production of hardened carbon.

The streams of liquid fuel travel thus in an opposite direction to that of the combustion air which is heated in the regenerators, rises in an upward direction and brakes to a certain extent the speed of the thin streams of. liquid fuel whilst becoming mixed with the vapours of liquid fuel, and the latter is immediately lighted.

In order to completely vaporize the fuel before the latter reaches the floor where the air is subdivided, the injection of fuel is generally subdivided in the vertical plane of the uprights of the oven into two or several jets of a small diameter, for instance comprised between about half a millimetre and about one millimetre. Such jets may have different diameters and directions, they may be even oblique, the main object being to ensure a regular conversion into vapour and combustion of the liquid fuel along the entire height of the oven, at its various levels, thus rendering the temperatures uniform. In certain cases, in order to obtain uniform temperatures along the entire height of the oven without liquid fuel reaching the floor of the oven, it may be advantageous to inject a small portion of fuel gas into the oven at its lower level, together with the combustion air, thus ensuring an additional heating at the lower level of the retorts, allowing thus to reduce the length of the streams of liquid fuel. Such an injection of gas may advantageously be made by using carbon monoxide (CO) as the gas, and namely the carbon monoxide gas which escapes from the rctorts. Such gas may be collected in any convenient manner.

When the direction of gases in the oven is to be reversed, that is generally every 15 to 30 minutes, the inlet of liquid is closed for one half of fuel injecting devices in operation on half the oven, the admission of air is reversed, and the liquid fuel is admitted to the other half of injecting devices, this latter half receiving now the combustion air which has been heated in the regenerators.

Such a heating arrangement with multiple injections of liquid fuel at different points of the zinc oven, allows of more regularly heating than what is generally obtained with a gaseous fuel. It is indeed sufficient to provide a flow meter and a throttle valve for each injector in order to maintain the required amount of fuel for each injector. It is also possible to provide for each injection a small pump of variable output remaining strictly constant for each position of the regulating device.

In the heating arrangement of zinc ovens above described, the injecting devices for liquid fuel placed on the roof of the oven above the narrow passages provided in the masonry, which allow a passage to the streams of liquid fuel, are subjected to radiation from the combustion chamber through the said passages during the period for which they deliver liquid fuel, and also during the period for which they are not working, when passing from one reversal to another. An overheating of the injector and therefore of the liquid fuel, should be prevented in order to avoid cracking and thus obstructions. For that purpose, a cooling of the injector may be ensured by a flow of liquid and by a thin curtain of water droplets provided between the injector and the passage in the roof, obtained for instance by injecting wet saturated water vapour. It is obvious that during the period for which the injectors do not work, it is also possible to provide a flap valve made of a material which is non-conductive of heat and resists well to the action of heat, which automatically closes the passage in the roof and protects the injecting device from heat radiated by the oven.

One of the advantages of the persent invention is that it may be readily applied at little cost to zinc ovens working with reversals, and heated with combustible gas. The heating arrangement by gas may be retained to pass from liquid fuel heating to gas heating, when liquid fuel is no longer available.

FIGURES I to 3 of the accompanying drawings show a mode of applying the invention to a Zinc oven with 4 rows of retorts of the type working with reversals.

FIGURE 1 is a vertical section made in a zinc oven by a plane perpendicular to the partitioning wall which divides the oven longitudinally in halves. The numeral 1 shows the said partitioning wall; the reference numerals 2, 2 show retorts which are supported at the rear into recesses provided in the wall, the numeral 3 shows the roof of the oven, the numerals 21, 21 show heat regenera tors with lattice-work packings, the numerals 4, 4 show pipes through which combustion air heated in the regenerators is introduced into the combustion chamber of the oven, whilst liquid fuel is injected into the corresponding half-oven, and through which leave the hot gases produced by the combustion of liquid fuel during the period which follows the reversal.

FIGURE 2, which is a view of the front wall of the oven, shows uprights 17, supporting plates 18 upon which are supported the front part of the retorts 2, the axial lines AA and BB showing the position of the axes of the uprights and of the openings or passages 5 shown in FIGURE 1.

The said axial lines show also the position of the injector shown in FIGURE 3.

The FIGURE 3 shows a section made in the arrangement for the injection of liquid fuel, along a vertical plane parallel to the partitioning wall and passing through the axis of a vertical injector.

A horizontal metal flooring of lattice-work formation not shown in the drawings, may be provided above the roof of the oven. It SBI'VEES for the suspension of the casings of fuel injecting devices and for the circulation of the workmen who supervise and maintain the arrangement in good working order.

The numeral 7 shows a casing with two boxes 8 and 9, cooled by a water flow. The water is brought by conduits 8' and 9', and leaves through conduits 8" and 9". Wet saturated water vapor is brought through a conduit 20 to the pipe 10 provided with orifices 11 through which the water vapour escapes and forms a veil of vapours underneath the injectors 13.

The numeral 12 shows a supporting block for the injectors 13 which are screwed into the mas of the supporting block, the orifices 14 of the injectors projecting thin jets of liquid fuel through the roof of the oven.

The numeral 15 shows a conduit for bringing in the liquid fuel and the numeral 16 shows a channel for its distribution to the various injectors belonging to one and the same block. Each block comprises preferably several injectors of different diameters.

The various blocks are arranged above the passage 5 provided in the roof 3 of the oven and the supports are fixed to the above mentioned metal flooring, by means of girders 6, 6.

The block 12 is made independent from the casing 7. It rests upon the machined and horizontal bearing surface 19. A sand joint 22 ensures if necessary, a tight joint.

It is thus possible to supervise the injectors in a rapid and easy manner, whilst avoiding all disturbance of the direction of the jets of liquid fuel, when the supporting blocks are removed or replaced in position.

The water cooling of the boxes 8 and 9 and the ad mission of wet saturated water vapour protects the injectors against any undesirable heating due to heat radiation from the combustion chamber, and protects the entire arrangement against any deformations produced by an excessive heating.

The above arrangement more particularly prevents an overheating of the liquid fuel which remains stationary ell) during the period of non-injection and also prevents the ensuing cracking, as the water vapour prevents any excessive cooling which would solidify the liquid fuel and would make a rc-starting of the injection uncertain.

What i claim is:

l. A process for heating zinc ovens having an enclosure in which a plurality of retorts is provided between which incandescent gases pass which heat the surfaces of the retorts, which comprises moving combustion air in an upward direction between the retorts, while injecting liquid fuel in a downwards direction between the retorts in jets, controlling the diameter of the jets of liquid fuel and the speed of the jets to allow the liquid fuel to be substantially completely converted into vapor state under the combined effect of the contact with the incandescent guses and of radiation of the hot surfaces of the retorts before they reach the floor of the oven, thus avoiding carbonaceous deposits upon the inner surface of the oven or the retorts.

Z. A process for heating zinc ovens having an enclosure in which a plurality of retorts is provided between which incandescent gases pass which heat the surfaces of the retorts, which comprises moving combustion air in an upward direction between the retorts while injecting liquid fuel in a downwards direction in jets of between about half a millimeter and about one millimeter diameter controlling the speed of the jets to effect conversion of the liquid fuel, into vapor state under the combined effect of the contact with the incandescent gases and of radiation of the hot surfaces of the retorts before they reach the floor of the oven, thus avoiding carbonaceous deposits upon the inner surfaces of the oven or the retorts.

3. A zinc oven having an enclosed casing with a roof, a floor and walls, a plurality of retorts inside the casing supported on the walls, means for supporting the retorts inside the casing, uprights arranged in a plane for supporting the roof, means for causing combustion air to pass upwards between the retorts and for causing incandescent gases formed in the oven to pass between the retorts to heat the surfaces of the retorts, and downwardly directed means arranged upon the roof of the oven for injecting thin jets of liquid fuel in a downward direction into the oven a sufficient distance into the oven and between said retorts to cause said liquid fuel jets to he completely converted into vapor state before they can strike the floor of the oven.

4. A zinc oven as claimed in claim 3, in which the means for injecting the thin jets of fuel in a downward direction into the oven are arranged in the plane of the said uprights.

5. A zinc oven as claimed in claim 3, having means associated with said means for injecting liquid fuel for providing a curtain of fine droplets of Water and steam protecting the means for injecting liquid fuel against radiation from the oven.

6. A Zinc oven as claimed in claim 3, having superimposed parallel. horizontal rows of retorts, and means for heating the lowest row of retorts with carbon monoxide gas which escapes from the interior of the retorts.

References Cited in the file of this patent UNITED STATES PATENTS 612104 Hegeler Oct. ll, 1898 876,891 Ziesing Jan. 14, 1908 893,560 Ziesing July 14, 1908 1,048,420 Londress et al Dec. 24, 1912 2,386,429 Breyer Oct. 9, 1945

Claims (1)

1. A PROCESS FOR HEATING ZINC OVENS HAVING AN ENCLOSURE IN WHICH A PLURALITY OF RETORTS IS PROVIDED BETWEEN WHICH INCANDESCENT GASES PASS WHICH HEAT THE SURFACES OF THE RETORTS, WHICH COMPRISES MOVING COMBUSTION AIR IN AN UPWARD DIRECTION BETWEEN THE RETORTS, WHILE INJECTING LIQUID FUEL IN A DOWNWARDS DIRECTION BETWEEN THE RETORTS IN JETS, CONTROLLING THE DIAMETER OF THE JETS OF LIQUID FUEL AND THE SPEED OF THE JETS TO ALLOW THE LIQUID FUEL TO BE SUBSTANTIALLY COMPLETELY CONVERTED INTO VAPOR STATE UNDER THE COMBINED EFFECT TO THE CONTRACT WITH THE INCANDESCENT GASES AND OF RADIATION OF THE HOT SURFACES OF THE RETORTS BEFORE THEY REACH THE FLOOR OF THE OVEN, THUS AVOIDING CARBONACEOUS DEPOSITS UPON THE INNER SURFACE OF THE OVEN OR THE RETORTS.

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