US2393330A - Electrolytic cell - Google Patents

Description

Jan. 22, 1946. R. J. McNlTT I ELECTROLYTIG CELL' 'Filed' July 11, r1,941

lNvEN'roR RoaERTJ.' MMV/ 27A BY ATTORNEYS Patented Jan. 22, 1946 2 Claims.

This invention relates tov electrolytic cells for the electrolysis of fused salt baths, and more collecting hood in which metal rising from the cathode collects and is withdrawn from the cell.'

During the usual operation of such cells, more or less gas, such as hydrogen, carbon monoxide and carbon dioxide, or mixtures thereof, enters l particularly to electrolytic cells having a metal' UNITED STATES PATENT OFFICE Robert J. McNitt, Perth Amboy, N. J.

Application July 11, 1941, Serial No. 401,892

In the cells heretofore used, it has been the A Practice to remove both the metal and the gas collected in the hood through a single duct leading upward from the hood to a receiver for the metal. In a type of cell now widely used, the

' metal and gas collected in the hood flow upward in the same duct and are discharged at the place where the metal is received. As a result or my investigations and discoveries, I have found that this gas very seriously interferes with the settling of particles of salt bath and other impurities from the metal in the duct causing them to becarried over with the metal into the receiver. The interference with the settling of impurities released from the metal rising in the duct aids in the formation of secretions or salt and other impurities with the metal on the inner walls of the duct with resulting interruptions in the flow of metal.

The gas causes slugs of crude metal with much impurity to be carried upward through the duct finto the receiver in the way liquids are lifted by an air-lift pump. In accordance with my invention. I provide a separate duct for removing the gas collected under the hood. I eliminate almoet entirely the passage of gas from .the hood up through the metal delivery duct and facilitate the separation of impurities from the metal in the duct and their return to the bath, thereby increasing the purity of the metal which flows from the duct to the receiver.

The single figure of the accompanying drawing is a sectional side view of an electrolytic cell embodying the invention. The cell is of the general type in which molten metal liberated at the cathode rises in the bath and is collected under the hood I. Cells of this type are provided with an upright duct 2 through which the metal flows by virtue of its low specific gravity from the hood at the rate it is formed and passes over into the ;receiver 3. In order to prevent the passage of the gases which are trapped beneath the hoodl upward through the duct 2, I provide in accordance with this invention, an upright sas duct 4 for the automatic removal of the gas from the hood. The duct 4 is preferably connected to the top of the hood at any suitable place. The entrance of duct 2 extends below the entrance to duct 4, thus compelling the gas to pass up through duct 4.

The molten metal rises in this gas duct to the level of the overflow from the duct 2 and I prefer to provide a larger cross-section in duct 4 at this level to permit the gas to escape from the metal quietly. The upper portion of the chamber is provided with an adjustable release valve l to permit the gas to escape at the desired rate and pressure. By means of this valve, air may be kept out of the aas duct and the gas may be released at a pressure slightly above atmospheric pressure.

In order to prevent the solidiflcation of molten metal in the gas duct 4, I surround it with thermal insulation I. f

I may provide a lvalve controlled tube 1 lor cated above the surface of metal in duct 4 to admit an inert gas, such as nitrogen, to prevent contamination due to the infiltration of air at times when there is little or no iiow of gas through the duct.

I claim:

1. An electrolytic cell for the electrolysis of fused salt baths which comprises a vessel for confining the fused salt, a hood for the collection of molten metal which is submerged in the fused saltI said hood having a top portion beneath which the non-anodic gas and metal are collected, anupwardly disposed metal delivery duct -which connects to and enters the hoodthrough which the collected metal is forced upward by the weight of the fused bath above the hood and discharged from the cell, said metal duct having a metal-entrance opening below the top portion of the hood which causes the metal to accumulate ina layer of appreciable thickness before it reaches said entrance opening, a gas discharge duct for the removal from the cell of non-anodic gas collected under the hood which connects to the hood land has a gas-entrance opening at a higher level than the metal-entrance opening, whereby the gas is selectively removed from the hood through the gas duct and the metal is selectively removed from the hood through the metal duct, thereby preventing the gas from blowing slugs of impure metal through the metal delivery duct, and means for the collection and removal from the cell of the anodicl gas produced in the decomposition of the salt.

2. In an electrolytic cell according to claim 1, the additional improvement which comprises a release valve connected to the gas duct for regulatins the pressure of the escaping gas.

ROBERT J. MUNI'IT.

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