US1548972A - Method of eliquating zinc - Google Patents

Description

Aug. 11, W25; 1548372 F. ANDERSEN METHOD OF ELIQUATING ZINC Filed June 21. 23

Patented Aug. 11, 1925.

UNITED STATES 1,548,972 PATENT OFFICE.

FRIDTJ' OF ANDERSEN, OF TROLLHATTAN, SWEDEN, ASSIGNOR TO TROLLH A TTANS ELEKTROTHERMISKA AKTIEBOLAG, F STOGKHO'LM, SWEDEN.

METHOD OF ELIQUATING- ZINC.

Application filed June 21, 1923. Serial No. 646,897.

To all whom it may concern:

Be it known that I, FRIDTJOF ANDERsEN, a subject of the King of Norway, and residing at Trollhattan, Sweden, have invented certain new and useful Improvements in Methods of Eliquating Zinc, of which the I following is a specification.

In zinc, extracted from ores or products containing lead in addition to zinc, the zinc is always mixed with lead in a greater or lesser degree.

The capacity which zinc possesses of dissolving lead is known, to be dependent on the temperature, so that the higher the temperature, the greater, the percentage of lead, which the zinc is able to maintain dissolved. The same condition also concerns any iron present. This property of the zinc has been employed for purifying the same to a certain extent from these two impurities. Said process, which is called eliquation, and which consists in maintaining the spelter or impure zinc at a temperature just above the smelting point, whereby that portion of lead and iron, exceeding the percentage capable of dissolving at the temperature in question, is dissociated and may be separated from the zinc, has hitherto been effected inlreverberatory furnaces, heated with coal or 01 Said furnaces however have certain inconveniences, arising from the manner of heating the furnace. It is of the greatest importance in this process to maintain the temperature as constant as possible, and that a nonoxidizable atmosphere as regards the zinc exists over the bath, or in other words, the atmosphere in the furnace must be neutral or reducing.

The present invention has for its object to overcome these difliculties, and consists in employing radiant electric heat for the carrying out of the process, whereby the temperature can be maintained constant or may be varied to accommodate the process. Moreover the process is performed in an atmosphere, which, is maintained neutral or reducing. The employment of radiant heat results in the advantage that contact between the heating elements and the-metal under treatment is thereby avoided, and therefore no contamination of the said metal is v possible.

Moreover the provision of a non-oxidizing atmosphere about the heating elements avoids the oxidation both of the elements and the metal under treatment.

A further advantage of the arrangement resides in the fact that a temperature control within very narrow limits is thereby possible.

A constant, or if desired a variable, temperature is obtained in the best manner by employing electrically heated bodies located above the impure zinc under treatment. As material for such bodies there may be used bodies, manufactured of carbonaceous or graphitic materials, mixed with a suitable additional material for establishing the required electric resistance, and the different components may be bound by means of tar, asphalt or any other known adhesive.

Except these above mentioned resistance materials the heating body in certain cases may consist of any known metal alloy with a high electric resistance.

On the accompanying drawing a furnace for carrying out the said eliquation process is shown as an example.

Fig. 1 illustrates the furnace in longitudinal section, whereas Fig. 2 is a horizontal section on the line A-B in Fig. 1. e indicates resistance bodies of carbonaceous or graphitic material and t resistance members, consisting of metal wires, wound round an insulated pipe f or the like.

The different resistance bodies shown on the drawing may be employed either each by themselves or in combination with one another.

0 indicates the feeding opening for the crude product to be eliquated, b the metal bath proper, 0 an opening for the discharge of the purified product, and (Z the tapping device for the eliquated products.

It is clear that in the furnace above described, it will be possible to control the temperature within wide limits, partly by augmenting or diminishing the number of heating bodies, and partly by varying the strength of the current in said resistance bodies.

However it is to be noted that if the resistance bodies are situated in a free space above the zinc bath, as shown on the drawing, they are exposed to oxidation in a high degree, and to deterioration sooner or later, provided the atmosphere surrounding the resistance bodies, is not reducing or at least chemically neutral to the resistance material.

In order to establishan atmosphere which smelting impure zinc by means of radiant is suitable to the electrode material a pipe 9 heat from e ectrio resistance bodies located with a controlling cock h is introduced in above the metal under treatment, maintain- 5 the furnace, by means of which the furnace 'ing a non-oxidizing atmosphere above the can be filled 'with a. suitable gas or with a molten zinc, and maintaining 'the temperaliquid, which is converted to vapor at the ture required for eliquation. working temperature. If the pipe 9 is made In testimony" whereof I have slgned my of glass, it will be possible to directly obname 1 0 this specificatlon.

serve the \gas pressure in the furnace fro FRIDTJ OF ANDERSEN. outside thereof. Witnesses:

Claim. VERNER SvAN'rssoN,

Method or eliquating zinc consisting in AxnL JOHANBSON.

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