Eka Nobel

Casco Nobel Ab

Eka Nobel Ab

Goran Sundstrom

Johan Landfors

Helena Falgen

Sten Porrvik

Bertil Hedvall

Gunnar Mattson

Birgitta Sundblad

Maria Norell

Roy Hammer-Olsen

John C Sokol

Disclosed is a process of producing chlorine dioxide having the steps of providing a reactor with an aqueous acidic reaction medium containing alkali metal chlorate and phosphate; reducing chlorate ions in the reaction medium to form chlorine dioxide; withdrawing chlorine dioxide gas from the reaction medium; withdrawing reaction medium from the reactor and transferring it to an electrochemical cell; treating the reaction medium electrochemically to increase the acidity and decrease the content of alkali metal ions; recycling the acidified reaction medium to the reactor; and adding make up alkali metal chlorate to the reaction medium before or after the electrochemical cell.

Process of producing chlorine dioxide

The invention relates to a process of producing chlorine dioxide using, in a first alternative atmospheric pressure and hydrogen peroxide in the reaction medium optionally with an electrolytic cell. In a second alternative, either atmospheric or subatmospheric pressure is used in the reaction medium together with an organic or inorganic reducing agent and an electrolytic cell.

The invention relates to a method of producing an acidified aqueous solution containing alkali metal sulfate and chlorate comprising the steps of introducing an aqueous solution containing alkali metal sulfate and chlorate into an electrochemical cell and electrochemically increasing the acidity of said aqueous solution, wherein the current efficiency of the cell is maintained below 70%. The invention also relates to a method of producing chlorine dioxide comprising the steps: Providing a reactor with an aqueous acidic reaction medium containing alkali metal chlorate and sulfate; reducing chlorate ions in said reaction medium to form chlorine dioxide; withdrawing chlorine dioxide gas from the reaction medium; withdrawing reaction medium from the reactor and transferring it to an electrochemical cell substantially without crystallization of sulfate or chlorate; electrochemically acidifying said reaction medium to increase the acidity and to decrease the content of alkali metal ions; recycling acidified reaction medium to the reactor; adding make up alkali metal chlorate to the reaction medium before or after the electrochemical cell; wherein the current efficiency of the electrochemical cell is maintained below about 80%.

Electrochemical process

The present invention relates to an electrochemical process for the production of sulphuric acid and alkali metal hydroxide, from an aqueous anolyte containing alkali metal sulphate. According to the invention, crystalline alkali metal sulphate is added to the anolyte, whereby the concentration of water can be maintained below about 55 percent by weight. In the electrolysis, the anolyte is brought to an electrochemical cell with a cation exchange membrane. In the cell, sulphuric acid and oxygen are formed in the anode compartment and alkali metal hydroxide and hydrogen in the cathode compartment. The steps normally preceding the electrolysis, i.e. dissolution and purification of the sulphate can be disposed of, since the process is less sensitive to impurities than the processes of the prior art. The present invention also relates to an apparatus for the production of sulphuric acid and alkali metal hydroxide according to the invention.

Process and apparatus for the production of sulphuric acid and alkali

Toner particles for electrophotographic copying and processes for their

Growing community of inventors

Sundsvall, Sweden

Goran Sundstrom