Erco Industries Limited

Tenneco Canada Inc.

Richard Swindells

Gerald Cowley

Maurice C Fredette

Marek Lipsztajn

Zbigniew Twardowski

Edward J Bechberger

Mark Kostanecki

The formation of sodium sulfate by-product in sulfuric acid-based chlorine dioxide generating processes is decreased and preferably eliminated entirely, by effecting electrochemical treatment of sodium ion-containing feed materials for the generator to remove sodium ions and to add hydrogen ions. Sodium hydroxide may be produced as a by-product. The process is generally applicable to the electrochemical treatment of alkali metal chlorates, alkali metal sulfates and mixtures thereof to produce acidified solutions useful in providing chlorate ion-containing feeds to such chlorine dioxide generating processes or for other purposes.

Electrochemical processing of aqueous solutions

A highly efficient chlorine dioxide generating process which produces chlorine-free chlorine dioxide and neutral solid phase sodium sulphate from sodium chlorate, sulphuric acid and methanol is described. Solid phase sodium acid sulphate recovered from the high acidity reaction medium is metathesized using controlled quantities of water and controlled quantities of methanol to form the solid phase neutral sodium sulphate. Sulphuric acid recovered from the acid sulphate by the metathesis is recycled to the generator along with a part of the methanol used in the metathesis.

Production of chlorine dioxide with conversion of by-product solid phase

A machine-controlled chlorine dioxide generating process which produces a gaseous mixture of chlorine dioxide and chlorine is described. Efficiency determinations are made from gas analysis and adjustment made as required. The gas analysis may be used in combination with actual production rate and required production rate machine determinations, possibly along with reaction medium analysis, to adjust operating parameters as required to attain optimum production rate and chemical usage.

Control system for chlorine dioxide plants

An automatic continuous monitoring system for a chlorine dioxide generating process (10) which produces a gaseous mixture of chlorine dioxide and chlorine (12) is described. The automatic system eliminates the need for periodic manual analysis of the off-gas stream and enables changes in the process efficiency to be rapidly compensated for. The system preferably utilizes a gas-liquid chromatograph analyzer (36) to analyze the off-gases from the generator (10) and to provide signals (42, 44) corresponding to the measured amounts of chlorine dioxide and chlorine. These signals then are converted (46) to a signal (47) corresponding to the ratio of chlorine dioxide and chlorine in the off-gas stream. The ratio then is converted to the efficiency (48). The efficiency value so obtained (49) may be compared with a previously determined value and changes compensated for by catalyst and/or reactant feed variations.

Efficiency control system for chlorine dioxide plants

The efficiency of a low actual hydrogen ion concentration chlorine dioxide producing process in which a chlorate and hydrochloric acid or hydrogen chloride are fed to a reaction medium in a single vessel generator-evaporator crystallizer is increased by the use of small quantities of methanol.

High efficiency chlorine dioxide production using HCl as acid and

The efficiency of a low total acid normality chlorine dioxide producing process in which a chlorate, a chloride and sulphuric acid are fed to a reaction medium in a single chambered generator-evaporator-crystallizer vessel is increased by the use of small quantities of methanol.

High efficiency chlorine dioxide production at low acidity with methanol

Chlorine dioxide and chlorine are produced by reduction of sodium chlorate with chloride ions in an aqueous acid medium having a total acid normality of 2 to 4.8 normal. The reaction medium is maintained at its boiling point under a subatmospheric pressure to provide steam dilution of the chlorine dioxide and chlorine and anhydrous neutral sodium sulphate is deposited therefrom. Chlorine dioxide is recovered as an aqueous solution containing some dissolved chlorine while the bulk of the chlorine is recovered in gaseous form. Part of the recovered chlorine is reacted with sulphur dioxide and water, preferably in heat exchange relationship with the reaction medium to impart heat of reaction thereto, to form hydrochloric acid and sulphuric acid for feed to the reaction medium in sufficient quantity to provide no more than the quantity of sulphate ions required at the prevailing efficiency of the chlorine dioxide-producing reaction to form neutral sodium sulphate from sodium ions introduced to the reaction medium with the sodium chlorate. The remainder of the hydrogen ion and chloride ion feed requirements of the reaction medium are provided either by hydrogen chloride or hydrochloric acid, preferably formed by reaction of chlorine, including recovered chlorine, and hydrogen, or by a mixture of 2 moles of sodium chloride and one mole of sulphuric acid.

Integrated chlorine dioxide producing system

Chlorine dioxide is produced in a continuous process by reaction of sodium chlorate and hydrochloric acid. The reaction medium is maintained at its boiling point under subatmospheric pressure and the resulting steam is used to dilute the chlorine dioxide and chlorine and remove the same from the reaction zone. Sodium chloride is deposited from the reaction medium in the reaction zone. The reaction medium also contains buffering anions and the actual hydrogen ion concentration of the reaction medium is maintained in the range of about 0.05 to 0.3 normal to maintain an economic production rate for the chlorine dioxide.

Production of chlorine dioxide from buffered reaction media

The efficiency of the Solvay chlorine dioxide producing process is enhanced by the use of a high total acid normality and a single vessel generator-evaporator-crystallizer.

Growing community of inventors

Caledon, Canada

Richard Swindells