SU1717675A1 - Method of producing concentrated solution of sodium hydroxide - Google Patents

Abstract

This invention relates to electrochemical technology. In order to reduce energy consumption, a concentrated solution of sodium hydroxide is obtained in two stages in electrolytic cells with ion-exchange membranes, while a solution of sodium hydroxide from the cathode space of the first-stage electrolyzers is fed into the anode space of the second-stage electrolyzers and the spent solution of the second stage electrolyzers into the cathode space of the first stage electrolyzers.

Description

The invention relates to the technology of electrochemical production, in particular to the preparation of a solution of sodium hydroxide by electrolysis of a solution of sodium chloride in electrolytic cells with an ion-exchange membrane.

The aim of the invention is to reduce energy costs.

Example 1. Electrolysis is carried out in two identical laboratory cells, each of which consists of an anodic and a cathodic, spaces separated by an ion-exchange membrane. Nickel plates are used as cathode and anode. The surface of the working part of the ion-exchange membrane in each cell is 12.5 cm2. The distance between the cathode and the anode in the cell is 3 cm. The electrolysis is carried out at 85-90 ° C and a current density of 2 kA / m2. 1 dm3 of sodium chloride solution containing 315 g / l of NsCf is poured into the anode space of the first and second cells. 50 cm views are poured into the cathode space of the first cell and electrolysis is carried out in

for 3 hours. A solution of caustic soda containing 20% NaOH is withdrawn from the cathode space of the first cell after electrolysis, and this solution is poured into the cathode space of the second cell, and electrolysis is carried out for 9 hours.

As a result of electrolysis, a 45% solution of caustic soda is obtained in the cathode space of the second cell. The voltage on the first cell is 5 V, on the second cell is 6 V. The current output on the first cell is 90%, on the second cell it is 85%. The energy efficiency in the process is 32.5%. The first and second cells work with the Fimion membrane. The total energy consumption of 4457 kWh / 1 t MaOH.

 Example 2. Electrolysis was carried out in the same two laboratory cells and under the same conditions as described in Example 1. A new electrolysis resulted in a 50% solution of caustic soda from the cathode space of the second cell. The electrolysis in the second cell is carried out for 11.5 hours.

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with

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The voltage in the second cell is 6.3 V, the current output is 83%. The energy efficiency in the process is 28.7%. Total power consumption 4600 kWh / 1 t NaOH.

EXAMPLE 3. Electrolysis was carried out in the same two laboratory cells and under the same electrolysis conditions as described in Example 1, but 1 dmg of a 20% aqueous solution of caustic soda was poured into the anode space of the second cell. The chamber is filled with 50 cm3 of a 20% NaOH solution, and electrolysis is carried out for 8 hours and 50 minutes to obtain a 45% solution of caustic soda in the cathode compartment of the second cell.

The voltage on the second cell is 5.5 V. The current output on the second cell is 87%. The energy efficiency in the process is 35.4%. Total electricity consumption 4049 kWh / 1 t NaOH. The electrolyte from the cathode space of the electrolyzer of the second stage is returned to the anode space of the electrolyzer of the first stage.

EXAMPLE 4. Electrolysis was carried out in the same two laboratory cells and under the same conditions as in Example 3, but electrolysis was carried out for 11.2 hours until the second electrochemical cell 50- was obtained in the cathode space. % solution of caustic soda.

The voltage on the second cell is 6.0 V. The current output on the second cell is 85%. The efficiency of using electricity in the process is 31.5%. Total electricity consumption 4560 kWh / 1 t NaOH.

Thus, the proposed method allows to obtain a finished commercial product (45-50% solution of caustic soda), while the efficiency of using electricity is higher than in the known method by 3-4%.

Claims (1)

Invention Formula A method of obtaining a concentrated solution of sodium hydroxide in electrolytic cells with an ion-exchange membrane in two stages, comprising feeding the sodium chloride solution into the anode space and water into the cathode space of one or more electrolyzers of the first stage, withdrawing the sodium hydroxide solution from the cathode space of the first-stage electrolyzers and feeding it into the cathode space the space of one or several electrolyzers of the second stage, that is, with the fact that, in order to reduce energy costs, a solution of sodium hydroxide from atodnogo space electrolyzers first stage serves as the anode space and the second-stage electrolytic sodium hydroxide solution electrolyzers of the second stage is recycled to the anode compartment the cathode compartment of electrolytic first stage.