US3696010A - Method and apparatus for removing gas from an alkaline chloride electrolysis cell - Google Patents

Abstract

CHLORINE GAS MIXED WITH BRINE AND IN THE FORM OF FOAM IS WITHDRAWN FROM AN ALKALINE CHLORIDE ELECTROLYSIS CELL WITH A MERCURY CATHODE THROUGH PIPES LEADING FROM A CERTAIN NUMBERS OF ANODES AND ARRANGED ON OPPOSITE SIDES OF THE CELL. THE FOAM IS DELIVERED TO A TANK OR VESSEL WHEREIN THE GAS IS SEPARATED FROM THE BRINE BY DILUTED HYDROCHLORIC ACID AND CENTRIFUGAL ACTION. THE GAS AND BRINE ARE THEN SEPARATELY DISCHARGED FROM THE TANK.

Description

Oct. 3, 1972 os ETAL 3,696,010

METHOD AND APPARATUS FOR REMOVING GAS FROM AN ALKALINE CHLORIDE ELECTROLYSIS CELL Filed Aug. 24, 1970 2 Sheets-Sheet l FlG.l

INVENTOR$ Oct. 3, 1972 GLQS ETAL 3,696,010

METHOD AND APPARATUS FOR REMOVING GAS FROM AN ALKALINE CHLORIDE ELECTROLYSIS CELL Filed Aug. 24. 1970 2 Sheets-Sheet 2 Q S (mm FlG.2

FIG.3

INVENTORS "F a. 9322 3 WM United States Patent Office METHOD AND APPARATUS FOR REMOVING GAS FROM AN ALKALINE CHLORIDE ELECTROL- YSIS CELL Franz Glos, Salzgitter, and Joachim Mischke, Dortmund,

Germany, assignors to Friedrich Uhde G.m.b.H., Dortmund Germany Filed Aug. 24, 1970, Ser. No. 66,441 Claims priority, application Germany, Oct. 24, 1969, P 19 53 627.7 Int. Cl. C0111 1/12; B01k 3/00; C22d 1/04 US. Cl. 204-99 3 Claims ABSTRACT OF THE DISCLOSURE Chlorine gas mixed with brine and in the form of foam is withdrawn from an alkaline chloride electrolysis cell with a mercury cathode through pipes leading from a certain number of anodes and arranged on opposite sides of the cell. The foam is delivered to a tank or vessel wherein the gas is separated from the brine by diluted hydrochloric acid and centrifugal action. The gas and brine are then separately discharged from the tank.

CROSS REFERENCE TO RELATED APPLICATION Reference is made to the patent application of Franz Glos and Joachim Mischke, filed Jan. 10, 1969, Ser. No. 790,337, now abandoned, and entitled Method and Apparatus for the Electrolysis of Alkali Metal Chloride Solutions With Mercury Cathode (Group 114).

BACKGROUND OF THE INVENTION US. patent application, Ser. No. 790,337, now abandoned, describes an electrolysis method, in which the brine is forced into the reaction space between anode and cathode of an alkaline chloride electrolysis cell with horizontal mercury cathode and operating at high current density. As a result of the artificially created pressure gradient, the resulting intense flow rate in said reaction space flushes away the gas bubbles that form at the anode and removes them from the reaction space by the shortest possible route. Moreover, the anode is constructed in a manner that the bubbles travel to the upper part of the cell not only along the outer anode surface, but also through openings in the anode. In order to achieve the full effect intended by the method and apparatus described in said patent application, it is necessary to remove the foam quickly and efficiently from the upper part of the cell. The foam must not be allowed to accumulate in the upper part of the cell, since otherwise the foam may eventually cover the entire anode including its bottom surface resulting in a rise of the cell voltage. At low current densities, the gaseous chlorine may be mixed with the foam, whereas at high current densities it will entirely be in the form of foam and must be removed from the upper part of the cell quickly and efliciently.

One known method of satisfying this requirement is to suck out the foam from the upper part of the cell. The disadvantage of this method is the fast that, as a result, there will be underpressure or a partial vacuum within the cell and, in case of a leakage, air will penetrate into the cell. Air acts as an inert gas and will adversely affect the chlorine liquefaction process. A mechanical device is also known, with the aid of which the foam is scooped into so-called foam separators where brine and gas are separated. However, mechanical devices are costly and prone to faults owing to the corrosive process fluids with which they come in contact, such as chlorine and brine. Such known methods and devices are not efiicient enough to permit running the cell at a specific load which is 3,696,010 Patented Oct. 3, 1972 perfectly feasible with metal anodes, i.e. about 30 ka./m. or more. The amount of chlorine gas that will form per unit of cell volume at such high loads is so large that the chlorine gas will be in the form of gas/brine foam with bubbles of extremely small diameters.

SUMMARY OF THE INVENTION The present invention provides a method and apparatus that will permit a quick and eflicient removal of foam from the upper part of the cell in a simple manner and without the use of additional mechanical means, so as to prevent the foam from accumulating to an extent that the Whole anode is enveloped with foam thus impeding the formation of gaseous chlorine on the underside of the anode.

According to the invention, the task is achieved by discharging the chlorine gas in the immediate vicinity of the area where it forms through a plurality of apertures in each side wall of the cell. The plurality of apetures in each side wall of the cell for the purpose of removing chlorine gas foam are connected to a foam collecting pipe arranged along each side wall.

The particular advantage attained through the invention is that the advantages achieved by the distribution of brine at the anode and the removal of gaseous chlorine from the anode according to US. patent. application, Ser. No. 790,337, become fully effective, since the foam can be removed continuously and at the desired rate from the upper part of the cell. The foam discharge pipes at each side wall are arranged in such a manner that a certain number of anodes are apportioned to each set of two foam discharge pipes arranged opposite each other.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross sectional view of an alkaline chloride electrolysis cell taken substantially on the line 1-1 of FIG. 3;

FIG. 2 is a side elevational view of the cell showing pipes leading therefrom to a separation tank or vessel; and

FIG. 3 is a top plan view of the cell shown on FIG. 2. DESCRIPTION OF PREFERRED EMBODIMENT The illustrated embodiment of the invention comprises an alkaline chloride electrolysis cell in which the brine is introduced through a supply pipe 1 which has a series of branch pipes 2. The brine enters the reaction space through the hollow stems of the anodes 3, and the anode plates. As will be readily understood, the mercury cathode floats on the brine and the chlorine gas collects in the upper part 4 of the cell and flows therefrom through side wall apertures 5 from which lead vertical discharge pipes 6. The pipes extend downwardly and connect to horizontal foam collecting pipes 7 which, as shown, are sectional, the diameters of each section increasing toward the discharge end. The discharge end of the pipes 7 connect to the upper side of a tank 8 in which the chlorine gas is separated from the brine by addition of diluted hydrochloric acid and by centrifugal action. The chlorine gas is discharged from the tank 8 through a nozzle 9 at the upper side and the brine flows away through a nozzle 10 at the under side.

It will be seen that the apertures 5 are arranged opposite to each other. A certain number of anodes are apportioned to each set of foam discharge pipes 6, which are arranged opposite each other, one for each side of the reaction chamber.

What is claimed is:

1. A method of removing chlorine gas mixed with brine in the form of foam from an alkaline chloride electrolysis cell which consists in feeding brine to a reaction chamber interposed between separated anode surfaces and a mercury cathode so that the brine is distributed over each anode surface resulting in gas-brine foam, gravitationally flowing the foam through downwardly directed conduits leading from the immediate vicinity of the reaction chamber, and conducting the foam from said conduits to a gas-brine separating station.

2. A method as claimed in claim 1, which consists in feeding brine from above through the anodes, flowing the foam from both sides of the reaction chamber, and joining the two streams of foam in a gas-brine separating tank.

3. Apparatus for carrying out the method of claim 1,

comprising a housing providing a reaction chamber haveach side and to which the respective discharge pipes are connected, a tank to which each collecting pipe is connected, and gas and brine discharge nozzles respectively on said tank.

References Cited UNITED STATES PATENTS 3,535,223 10/1970 Baecklund et a1. 204278 X 3,575,837 4/1971 Shibata et a1. 20499 3,409,533 11/1968 Murayama et a1. 204219 3,445,373 5/1969 Schiicker et a1. 204220 X HOWARD S. WILLIAMS, Primary Examiner D. R. VALENTINE, Assistant Examiner US. Cl. X.R.

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