US2238819A - Process for the condensation of zinc vapors - Google Patents

Description

April 15, 1941. E 2,238,819

PROCESS FOR THE CONDENSATION OF ZINC VAPORS Filed April 17, 1939 //7 van for:

A'M LM KMA/r @2 7 Patente'd Apr. 15, 1941 PROCESS FOR THE CONDENSATION OF ZINC VAPOBS Pierre Neve, Sclaigneaux, Belgium Application April 17, 1939, Serial No. 268,389

3 Claims.

This invention relates to a process for the condensation of pure zinc vapors, or zinc vapors diluted by as.

As a rule, the cooling eilect oi' the walls of a condensation chamber have hitherto been employed to withdraw from metallic vapors the calories to be extracted therefrom for the purpose of liquefaction. In so doing, the attainable yield of liquid metal is limited by the fact that the condensation ceases when the amount of liquefied metal obtained from the vapors has reached the value at which the metallic vapors still present forma mixture saturated at the temperature of the cooling wall, and the endeavor to attain the highest possible degree of condensation leads to the formation of metal dust, the conversion of which into homogeneous metal is 'diillcult and expensive.

Practically the same conditions prevail when,

as has already been proposed, the vaporous metal is passed in numerous thin Jets through a fused bath of the same metal and the temperature of the bath is kept at the 'same time at a level only as little as possible above the solidification point of the fused mass, sincein this process the cooling condensation chamber is, so to speak, replaced by the molten metal in the fused bath, with which the metallic vapors are brought into heat-extracting contact over a large surface in consequence of their division into Jets. In order to prevent premature escape of the vapor Jets from the fused bath, it is also necessary in this. process to cover the surface of the bath by a' protective coating of non-oxidising or inert puiverulent or liquid substance.

According to the present invention, the said principle of'bringing metal vapors into contact Germany May 9, 1988 with a metal melt is utilized for the condensation Y perature it, amounts to a fraction of the vapor tension P of the same body in the pure state, in accordance with the equation? p=kP where k is a coeillcient smaller than unity, and

I that, furthermore, the absorption oi the vapors of metals by a metal having a dissolving action on said vapors, or by an alloy having such an action, only ceases when equilibrium between the vapor pressure p of the condensed and dissolved metal in the alloy or the dissolving metal and the vapor pressure P of the metallic vapors at thetemperature t in question has been attained in accordance with the equation since It is smaller than unity. This means that, according to the present invention, the metal to be condensed is converted from the vaporous into the liquid state without needing to pass through the dew point of the vapor, as is necessary when using a cooling wall for withdrawing the calories.

The process of the present invention possesses the great advantage, by comparison with the customary condensation of metallic, vapors carried out with the aid of a cooling wall, that practically all of the metal to be treated can be condensed into the liquid state, since no metal is produced in the form of dust, as is inevitably theiusual case in condensation with a cooling wall when attempts are made to condense all of the metal present. It is known that metal in the form of dust causes losses in condensation, and the lower in metal the metallic vapors are, themore-metal dust is formed when condensing with a cooling wall. A further advantage of the method of working according to the present invention consists in that vapors or gases having a low metal content, for example containing only from 10 to 15% of metal, can also be condensed with favorable results.

More particularly, the process of the invention can be carried out, for example, in the condensation of zinc vapors by using molten lead, which is a solvent for zinc under determined conditions of temperature. If it be assumed that Raoult's law, according to which the vapor pressure of each component of a solution is equal to the vapor pressure of the component in the pure state multiplied by the ratio between the numbers of molecules of the component and'oiv the entire solution, is applicable without correction, then a lead-zinc alloy containing 5 gram-moleper 1 kg. of CO. accordingly,

Any apparatus may be employed for carrying the process or the present invention into per cent oi the vapor tension of pure zinc at the same temperature.

Let it now be assumed, for the sake oi exampic, that thezinc is to be condensed from a mixture coming from any apparatus and comprising 50% of zinc vapors and 50% of carbon monoxide at a temperature of 1000 C, If this condensation of the zinc be carried out by contact with a cold wall, which is kept at a uniform temperature oi, for example, 800 C., the

densing zinc vapors with the aid of molten lead.

In said draw ng, the molten lead passes through the pipe i into the condensation chamber, which is kept at a temperature of about 800 C., and

percentage of zinc contained in the condensed vapor can be calculated. The condensation ceases when the gaseous phase has given up such an amount of zinc that the remaining mixture of carbon monoxide and zinc vaporis a saturated mixture at a temperature of 800 C.

The vapor pressure of pure zinc at 800 C. is 175 'mm. mercury, i. e. 1 kg. of CO contains at thistemperature EX 175 28 TWO-175 while the originating-mixture, in which the partial pressure oi the zinc vapor was 380 mm. mercury, contained per 1 kg. of CO. Accordingly,

has condensed.

It the condensation of the zinc be now brought =0.695 kg. of zinc,

=2.s'21 kg. of zinc X100=70% of the zinc about not by contact with a cooling wall, but

pressure of, the zinc in the alloy. At a; temperature ofi800 C. thelatter vapor-pressure is 0.0554175 mercury=8.'75 mm. mercury and I the remaining gaseous mixture then only contains a has condensed.

vapor, which contains 0.027 kg. of zinc per 1 of zinc vapor and without formation 01' dust, by

flows into the annular vessel 2 disposed therein, whence it passes by way of an overflow pipe 3 to a second annular vessel 4 disposed thereunder, leaving the latter through an overflow pipe 5 which leads to another annular vessel lying at a lower level. passes through a series of superimposed spaced annular vessels in the condensation chamber, which are in communication with each other through overflow pipes, while the lowest of these vessels is connected to the container 1, which closes the condensation chamber at the bottom, by way of a further overflow pipe 6. From the container 1 the lead-zinc alloy which is formed is discharged through the pipe. 8.

The mixture of CO and zinc vapor passes, below the bottom annular vessel, into the condensation chamber through the pipe 9. Since the overflow pipe 6 leading out of this annular vessel projects into the mass of metal contained in the container 1, the mixture of CO and zinc vapor is obliged to make its way upwards by way of the edge of the conical cap i0 which is immersed in the molten metal contained in the.

bottom annular vessel as far as a point which lies below the top edge of the overflow pipe 6. After the mixture of CO and zinc vapor has passed through the molten metal contained in the bottom annular vessel, the same operation is repeated from one 01' the, annular vessels disposed one above the other to the next, in each of which annular vessels is submerged a conical cap acting in the same manner as the cap ill.

on thispath the mixture of carbon monoxide and. zinc vapor; which becomes lower in zinc with every contact with molten metal, encounters lead which is progressively lower in zinc and progressively colder, which is iavorable to the economy of the process. The completely lib-- or zinc vapors diluted by gas, comprising trans- 65.

ferring the zinc vapors into a liquid'condition without previous reduction below the dew point '.bringing the zinc vapor into contact with a molkg. of CO, is reached at a temperature of 606? C. The condensation of the entire quantity of zinc between 70% and 98.84% has thus necessarily been eilec'ted above the dew point oi the mixture of C0 and zinc vapor.

I ten mass of a metal different from zinc and having the property of dissolving zinc at a temperature above the dew point of zinc vapors.

2. The process of condensing pure zinc vapors or zinc vapors diluted with gas without passing In this manner the molten lead zine vapors into contact. with a molten mass of without passage through the dew point of zinc vapor and without formation of dust, comprising bringing the zinc vapor into contact with molten lead at a temperature at least as high 5 as the dew point oi. zinc vapor.

PIERRE m.

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