US1308879A - Method of eliminating carbon dioxid and oxygen in electric smelting-furnaces. - Google Patents

Description

J. THOMSON.

METHOD OF ELIMINATING CARBON DIOXlD AND OXYGEN IN ELECTRIC SMELTING FURNACES.

APPLICATION mgo OCT. 24. 1918.

1,308,879 PatentedJuly 8,1919.-

% luvs/lion UNITED sTA Es PATENT OFFICE.

JOEIN THOMSON, OF YORK, N. Y.

IETHOD OF ELIXINATING CARBON DIOXID AND OXYGEN IR ELECTRIC SMELTING- FURNACES.

Specification of Letters Patent.

Patented July 8, 1919.

Application fl1ed ctohcr 24, 1918. Serial No. 259,560.

To all whom it may concern: Be it known that I, J our: THOMSON, a c1t1' zen of the United States, and a resident of the borough of Manhattan, city of New York, county and State of New York, have invented certain new and useful Improvements in Methods of Eliminating Carbon Dioxid and Oxygen in Electric Smelting- Furnaces, ofwhich the following is a specification, reference being made to the accompanying drawing, forming a part thereof.

This invention relates to metallurgy and concentrates thereof.

The single figure of the drawing is a sectional view of a' furnace as when fully charged, and is.a semi-diagrammatic illusof power, as E.

tration'which is employed to show a preferred manner of carrying the method into useful effect rather than to denote precise details of construction, v

The type of electric furnace required to utilize this method is one in which a carbon thermal element-such as a resistoror an arc-imparts its heat by radiation to an underlying charge. 4

In essence, th furnace, as here depicted, is comprised in-a brick casing, A, having a chamber, B, with a zig-zag resistor, C, interpolated between and suspended by suitable terminals, as D, D, energized from a source If, for example, the furnace is to be used for smelting roasted zinc concentrates, according to the classical formula ZnO+C= Zn-l-CO', the zinc being distilled in the form of fume, then the resistor-chamber would needs be provided with a throat, as F, leading to a suitable means for condensation, not deemed necessary of being here illus trated. So, too, an open retort. H, disposed beneath the resistor, would be necessary, which contains the charge; and this retort, when exhausted, is preferably capable of being removed and substituted by a duplicate recharged member.

One of the gravest difficulties metwith in zinc-smelting is the prescnce'of G0,; which has the pernicious effect of forming ZnO, or blue-powder, or a combination of both, and to the extent thereof, whatever it may be, minimizing the quantity of zinc that may be condensed in the form of liquid metal. Another grave difliculty resulting from the presence of CO in electric furnaces is its attack on such portions thereof as may best be made from amorphous or graphitlzed carbon.

The foregoing controlling objections are obviated by the practice" of this method; which consists in placing upon the top of the charge, preferably prior to its insertion in the furnace, a distinct and relatively thin layer of broken or granular carbon and maintaining it at a temperature of about or above l,l00 C.

In view of the state of the art, it may seem like asuperero ative statement that the use of carbon for t e elimination of CO in the presence of zinc-fume has hitherto been proposed; but in such instances, or as have been shown in patents issued to others as well as the present applicant, the carbon has been employed as a curtain or porous septum in, or at, or near to, the condenser.

It should be borne in mind that in dealing with zinc-fume and the gases of carbon the following reversible reaction takes place:

CO C2200 (1) At the smelting temperature, the reaction is from left to right, that is in the presence of carbon any G0, which maybe The consequence is that it is nearly always difiicult if not impracticable to maintain carbon at such a temperature, when in or contiguous to the condenser, as will be ado quate to produce the desired result. In fact it has variously been proposed to separately heat such carbon-screensg which, while effective as to the elimination of the pernicious gas, has the contingent objectionable result of super-heating the zinc-fume immediately prior to its entry into the condenser.

Moreover, CD, is generated at. a much lower temperature than CO, or at the latters initial temperature of active reaction with ZnO, wherefore the furnace chamber andthe condenser becoine more or less pre-filled with an oxidizing atmosphere.

sarily be adhered to; as, for he stokeddn, through 0 nings mice-walls, or be sifted-1n throng tubes or These ditiiculties and objections are wholly obviated, in a practical sense, by the-simple expedient of applying directly upon the top of the charge S a relatively thin layer of granular carbon R. This top dressing of carbon is virtually a filter-bed, through which all of the ascending volatiliz ed fume, vapor or gases generated in and ascending from the charge must percolate.

When feasible to do so,'the filter-carbon should preferably be 'pre-heated; consequently, when the charged retort is placed in the furnace, the resistor, orwhatever su'bstitute therefor may be used, quickly raises the temperature of this carbon to a state of incipient incandeseence both before CO is And the same observations apply to such oxygen as may be entrained or combined in the charge. Then, as the Zinc-fume mingles only with perfectly clean CO, the gases -may be progressively cooled as they flow toward the condenser wherea-t all of the zinc can be condensedto liquid metal. Moreover, in these circumstanceasuch portions of the furnace asmay best be constructed of carboniferous materials are completelyimmune from destructive attack and will endure indefinitely;

It is true-that, when the reaction begins, a certain minimum amount of the'filtercarbon, in direct contact with the charge, is lost by reduction; but this consumption ceases when a thin interposed layer of residuum is produced and the only further diminution will'be that due to the reaction with up-flowing C0,, or O, or hydrous vapors.

Nor does the addition of this filter-carbon involve extra expense; for it thus becomes feasible to at least correspondingly;diminish the amount of reaction-carbon mixed with the concentrate. .Or, to otherwise state the case, instead of having an excess of carbon mixed with the Zn(). serving to in.- crcasc the production of C0,, it is placed upon the top of the charge where it acts to convert the pernicious gas into one that is benign.

hile the within described mode of applying the filter-carbon to an ore charge is regarded as preferable, such need not necesexample, it may the fur the said thermal element from the erosive attack of CO and O', or either of them, which consists ih covering the said charge with a layer of filter-carbon and maintaining it. at a temperature of about or above eleven hundred degrees centigrade.

2. In an electric-smelting furnace provided with a carbon thermal element whose heat is transmitted by radiation to an underlying reacting charge composed of. ZI10+C, the method of converting, at the source of generation, CO into G0 which consists in covering the said charge with a layer of filtor-carbon and maintaining it at a temperature of about or above eleven hundred degrees. centigrade.

3. In an electric smelting furnace provided with a carbon thermal element Whose heat is transmitted by radiation to an underlying charge in which CO and O, or either of them, maybe evolved and whose presence would be pernicious, the method of converting them into benign gases which consists in covering the charge with a layer of filter-carbon and maintaining it at a temperature of about or above eleven hundred degrees centigrade.

4. In an electric smelting furnace provided with a carbon thermal element whose heat is transmitted by radiation to an under: lying charge in which CO and O, or either of them, may be evolved with pernicious effect, the method of rendering the said gases non-oxidizable which consists in applying to the top of the charge, prior to its introduction in the furnace, a layer of filter-can bon which is thereafter acted upon by the thermal element and maintained at a temperature higher than the charge. 5. In the treating of metals in a furnace having an electrical thermal element, the method which comprises employing the thermal element to heat the metal sufliciently to' drive off fame of the metal and protecting the thermal element a ainst the action of gases such as CO or g, passing off or mixed with the fume, by filter carbon lo cated between the metal being treated and the thermal element.

6. In the treating of metal in an electric furnace having a thennal element compris ing cmlmn as an essential part than f. the methml which cmnprl: .a: employing the the"- 111211 element. to heat a char e of the. metal sufficiently to drive off met-:11 fume and pro tecting the thermal clement, against, the #0- tion of ()0 or O by 1L layer of filter-carbon which is on said charge, said layer of filtercarbon being located so that the heat suppliekl l'rmn (ilk: thermal OlfiilK'nl', in the metal 10 to he uon eriml said layer.

This specification signed and witnessed this 13th day ml September, A. D. 1 318.

J (JHN THOMSON. Signal in tin; }')lO5unCQ 0f RALPH M. THOMSON, H.. (I). \VEED.

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