Fused salt electrolyzer for magnesium production

Abstract

An electrolyzer for the manufacture of magnesium, which has at least one electrolysis compartment with a cathode in the form of a frame whose members make up a closed loop around an anode in the electrolysis compartment. The present invention relates to electrolyzers for the manufacture of magnesium. Known in the art are electrolyzers for the manufacture of magnesium, comprising two compartments for the electrolysis of magnesium chloride, between which is placed a compartment to collect metallic magnesium. Between the electrolysis compartments and the collecting compartment there are partitions fabricated from refractory materials. The electrolysis compartments hold electrodes. Cathodes are provided in the form of plates with rods passing through a lining to a busbar. However the above-mentioned electrolyzer has a low production rate. Attempts to increase the production rate of the electrolyzer by enlarging the electrolysis compartments reduce the current efficiency and entail increased power consumption per unit of the quantity of metal product. Attempts to improve the production rate of the electrolyzer by increasing its length results in requirement of extra shop floor area and inconveniences in servicing. The multitude of cathodes, with each cathode having a current-conducting connection of its own, passing through the lining, impair the strength of the lining at the fixation points. Another weak point about this type of electrolyzer lies in that the partitions made wholly of a refractory material. These partitions fail at a high rate, resulting in loss of chlorine. The main object of the present invention is to eliminate the above-mentioned disadvantages. Other aims and advantages of the invention will become more fully apparent from the following description. The object of the present invention is to provide an electrolyzer which offers a greater production rate, a high output of metal per unit area, improved utilization of the working volume, and simplified servicing, and has a reduced power consumption, fewer current-conducting connections built into the lining and an extended service life. This objective is accomplished by providing an electrolyzer for the manufacture of magnesium, which, according to the invention, has at least one electrolysis compartment with a cathode in the form of a frame whose members form a closed loop around an anode in that compartment. An electrolyzer of this type has a greater production rate. It is expedient to make the members of the cathode (frame) in the form of walls and place the longitudinal walls between the electrolysis compartment and the collecting compartment in such a way that they constitute the lower portion of a partition. With this construction, it is seen that the output of metal per unit area is increased. It is further preferable that the thickness of the longitudinal members of the cathode be made to increase towards the current-carrying connection. This improves the operation of the electrolyzer and provides a more uniform distribution of current in the cross members of the cathode frame. A greater production rate is obtained if the frame-shaped cathodes are installed in at least three electrolysis compartments with at least two collecting compartments provided in between. In a cell with three electrolysis .Iadd.compartments .Iaddend.the electrode in the middle compartment may be about twice as wide as the electrode in the outer electrolysis compartments. Thus better use is made of the operational area of an electrolyzer.

What is claimed is: 
     
       1. An electrolyzer for the manufacture of magnesium, comprising in combination: at least three electrolysis compartments housing electrodes; and at least one magnesium collecting compartment located between said electrolysis compartments each of the electrolysis compartments having a plurality of anode members and a cathode in the form of a frame whose members form a closed loop around each anode member in said electrolysis compartment. 
     
     
       2. An electrolyzer, as claimed in claim 1, which includes partition walls between electrolysis compartments and collecting compartments and in which said cathode members comprise longitudinal members which are made in the form of walls which form a lower portion of the partition walls. 
     
     
       3. An electrolyzer, as claimed in claim 2, in which the thickness of said longitudinal cathode members increases in the direction of the current-conducting connection thereof. 
     
     
       4. An electrolyzer, as claimed in claim 1, having three said electrolysis compartments, in which an electrode located in the middle electrolysis compartment is substantially twice as wide as the corresponding electrodes located in the outer electrolysis compartments. .Iadd. 5. In an electrolytic cell for melt-electrolytic production of magnesium, comprising electrolysis and collecting compartments, said electrolysis compartment containing cathodes and anodes, the improvement comprising each of said cathodes consisting of two longitudinal members and a plurality of transverse members, said members forming a closed frame around at least one anode in said electrolysis compartment. .Iaddend.