RU2245944C1 - Electrolyzer for producing magnesium - Google Patents

Abstract

FIELD: light-metal metallurgy, possibly production of magnesium by electrolysis of melt salts.

SUBSTANCE: electrolyzer includes casing, lining, anodes, cathodes, roofs, built-up cell and it is provided with metering tank for continuously feeding raw material. Said tank is mounted in roof of built-up cell and it has branch pipes for charging and discharging raw material arranged in opposite ends of vessel.

EFFECT: enhanced efficiency, reduced outburst of chlorine to maintenance zone, lowered quantity of slime in electrolyzer, increased time period of operation at minimum suction of sanitary-technological gases from built-up cell.

1 dwg

Description

The invention relates to the metallurgy of light metals and can be used to produce magnesium by electrolysis of molten chlorides.

Known electrolyzer, including a casing, lining, an electrolytic compartment with cathodes and anodes, as well as a separation diaphragm (X.L. Strelets. Electrolytic production of magnesium. - M .; Metallurgy, 1972, p.266).

The disadvantages of this type of electrolyzer are: low productivity, high costs for removing sludge from the bottom of the working compartment and chlorine emissions in the service area, which range from 15-200 kg / t of magnesium, depending on the condition of the dividing wall as the service life of the cell increases.

Known diaphragmless electrolyzer, including a casing, lining, cathodes, anodes, dividing walls and prefabricated cells located parallel to the main working surfaces of the electrodes (AS USSR No. 558973, published in BI No. 19, 1977).

A significant drawback of this design of the electrolyzer is the difficulty of removing sludge from the electrolytic compartments during the collapse of the anodes on the hearth and a significant destruction of the circulation channels in the partitions during the main fillings of raw materials, accompanied by intense boiling of the electrolyte.

Of the known analogues, the closest to the claimed technical solution in terms of features is an electrolyzer for producing magnesium - a prototype (OA Lebedev. Production of magnesium by electrolysis. - M .: Metallurgy, 1988, p.196-199).

The electrolyzer includes a casing, lining, working compartments with electrodes, a collection cell with a removable cover, dividing walls with circulation channels and pipes for the extraction of chlorine and sanitary gases.

The cell operates as follows. The molten chloride salts are periodically poured into the collection cell, having previously removed raw magnesium and spent electrolyte from it. Magnesium and chlorine released on the electrodes float to the surface of the electrolyte. Chlorine is removed through a piping system for further processing, magnesium is transferred to the collection cell by the electrolyte flow, where it is accumulated, and the electrolyte is circulated between the working compartments and the collection cell.

Partly with the circulating electrolyte, chlorine enters the collection cell through the circulation windows, which leads to a decrease in the chlorine yield, worsening working conditions when performing operations during the maintenance of the electrolyzer, and an increase in production costs for organizing the disposal of sanitary gases from chlorine and hydrogen chloride.

A significant drawback of the electrolyzer is the need for frequent removal of sludge from interelectrode distances manually with a special tool. This operation does not allow to increase the working width of the electrodes, which limits the conditions for increasing the productivity of the cell.

The claimed technical solution is aimed at solving the problem of creating conditions to reduce the formation of sludge in the cell, which will reduce the labor costs for its removal and will increase the productivity of the cell by supplying raw materials from the metering tank. The dosed supply of the melt in time will allow the electrolyzer to operate without periods of intense boiling of the electrolyte, which will increase its productivity, reduce chlorine emissions in the service area and increase the operating time with minimal suction of sanitary gases from the collection cell.

The problem is solved in such a way that in the electrolyzer for producing magnesium, which includes a casing, lining, anodes, cathodes, anode overlays and a collection cell, it is new that it is equipped with a dosing tank for continuous supply of raw materials installed in the overlap of the collection cell, with loading pipes and unloading of raw materials located at opposite ends of the tank.

The proposed design of the electrolyzer will allow:

- intensify electrolyzers by about 10% by increasing current density;

- to increase the service life of electrolyzers due to the lower operating anodes, working on higher quality raw materials for magnesium oxide;

- reduce the loss of chlorine with the gases of service stations by reducing the amount of suction gases for gas purification during operation in a sealed mode;

- reduce labor costs for the removal of sludge from electrolyzers by increasing the time periods of picking up and removing sludge manually with a sharp decrease in the supply of magnesium oxide with raw materials;

- reduce the specific consumption of graphite by 10% due to the work with the optimal level of electrolyte above the cathodes in the mode of continuous loading of the molten chloromagnesium salts;

- reduce heat dissipation from the overlap of the collection cell by insulating the overlap of the supply tank with insulating material.

The drawing shows a cross section and a plan of an electrolyzer for producing magnesium. The cell consists of a steel casing 1, lined with refractory material 2, anodes 3, cathodes 5, anode ceilings 6. The collection cell 7 is covered by a removable overlap 8, and the capacity 4 is installed in the overlap 8 of the collection cell 7. The capacity 4 is integral with the overlap 8 of the assembly cell 7, and the nozzles for loading raw materials 10 and its unloading 11 are located at opposite ends of the tank 4. At the ends of the collection cell 7 on the ceiling 8 are removable covers 9 for performing technological operations for servicing the cell.

The cell operates as follows. When passing through electrodes and a direct current electrolyte, chlorine gas is released at the anodes 3, and liquid magnesium is released at the cathodes 5. The gas-filled electrolyte layer together with magnesium droplets rises in the interelectrode space, is separated from chlorine and moves towards the collecting cell 7, where liquid magnesium droplets merge into a compact mass and are periodically removed through a vacuum ladle through open covers 9 of the ceiling 8.

The supply tank 4 is installed in the overlap 8 of the collection cell 7, from which the electrolyzer is continuously fed with anhydrous carnallite. As the tank 4 is emptied through the drain device 11, the next portion of the melt is poured into the loading nozzle 10 until the tank 4 is completely filled. During the filling of the tank 4 with the melt, the drain device 11 stops the supply of raw materials to the collection cell 7 so that the magnesium oxide precipitated in the melt is stirred in the tank 4 did not fall into the volume of the working electrolyte of the electrolyzer. The placement of the raw material pipe 10 and the discharge pipe 11 at the opposite ends of the tank 4 allows you to control and regulate the process of pouring molten salts by opening the cover 9. In addition, this placement of the pipes provides the maximum zone of distribution of oxide sediment on the bottom of the supply tank 4 from anhydrous carnallite.

When the electrolyzer is fed with molten material through a dosing tank of a continuous feed of raw materials, the influx of harmful impurities (MgO, MgOHCl, SO $\genfrac{}{}{0ex}{}{\text{2-}}{\text{4}}$ ), changes the ratio of their content in the working electrolyte to the content of impurities in a portion of the melt entering per unit time. With the existing technology for supplying melt, the one-time maximum load of raw materials is about 13900 g / s. The melt loading speed in the proposed electrolyzer ranges from 50 to 100 g / s. This feed rate allows you to drastically change the ratio of the flow of impurities in time to the total volume of the electrolyte and allows the electrolyzer to operate without periods of boiling of the electrolyte during the main fill of the raw material. Typically, electrolyte boiling reaches 60 minutes per electrolyzer per day. In addition, the continuous feed of the electrolyzer with raw materials allows you to drastically change the schedule for manual removal of sludge in the direction of increasing time, because The conditions for the natural chlorination of harmful impurities with active chlorine are improved, and the main share of magnesium oxide and a suspension of carbon are retained in the supply tank. The organization of a continuous supply of molten raw materials to the electrolyzer allows you to work with the minimum optimal overlap of the circulation channels in the separation walls, this leads to an increase in the service life of the lining in the zone of fluctuation of the electrolyte level and increase the current yield of magnesium, since From the literature it is known that a sharp increase in the level of electrolyte leads to a delay in magnesium in the anode space and its combustion in chlorine.

The proposed electrolyzer will increase productivity without changing the geometric dimensions of the electrodes and the volume of the electrolyte, reduce emissions of chlorine in the environment and reduce labor costs for the extraction of sludge.

Claims (1)

An electrolyzer for producing magnesium, containing a casing, lining, anodes, cathodes, floors and a collection cell, characterized in that it is equipped with a metering tank for continuous supply of raw materials installed in the overlap of the collection cell, with raw material loading and unloading nozzles located at opposite ends of the tank .