Abstract: A process for the production of essentially chlorine free chlorine dioxide whereby a flow of chlorine dioxide obtained from reduction of alkali metal chlorate and containing by-product of chlorine gas is absorbed in water and the chlorine gas is treated with formic acid in the water solution. The formic acid is added in an amount resulting in a mole ratio formic acid to chlorine gas of >1:1.

Abstract: The invention describes a procedure for production of chlorine dioxide where, in a primary reactor chlorate, sulphuric acid and a reducing agent with optional extra additions of chloride ions are reacted, the resulting gas mixture mainly containing chlorine dioxide and air are forced through a scrubber to an absorption tower for absorption of the product gas. Where the reactor solution is withdrawn from the reactor optionally to a secondary reactor in which reducing agent is also added, the procedure being characterized by that of the primary reactor solution is recirculated optionally via a cooler to the upper part of a scrubber and then returned to the reactor.

Abstract: Process for production of magnesium chloride with sufficient purity for the production of magnesium metal, by leaching a magnesium containing raw material in hydrochloric acid. It is essential to keep the ratio between acid soluble iron and nickel greater than 120 and the ratio between acid soluble iron and phosphorus greater than 20 in the primary magnesium chloride solution, to obtain a sufficiently pure product. The acid soluble iron can partly or completely be substituted by an equal, molar amount of acid soluble aluminium. It is especially preferred to use mixtures of macro- and crypto-crystalline magnesites in the ratio 1:10-10:1 as raw material.

Abstract: Sodium sesquisulfate produced in crystalline form in a high acidity methanol-based highly efficient chlorine dioxide generating process is converted by metathesis to crystalline anhydrous neutral sodium sulfate and the acid recovered as a result is recycled to the chlorine dioxide generating step. The metathesis is effected by contacting the crystalline sodium sesquisulfate with aqueous sodium chlorate solution, aqueous sodium chloride solution, aqueous methanol or water alone. The metathesis is effected in such manner as to minimize the additional evaporative load imposed on the chlorine dioxide generating process by the metathesis medium.

Abstract: A process for the generation of chlorine dioxide from an alkali metal chlorate is provided that employs a waste sulphuric acid containing oxidizable organic material. Alkylation waste sulphuric acid from petroleum refining is particularly useful in this process. Conventional chlorate reducing agents used in the generation of chlorine dioxide can be partially or completely replaced by the organic material contained in the alkylation waste acid.

Abstract: A process for the production of chlorine dioxide by reacting in a reaction vessel an alkali metal chlorate, mineral acid and a reducing agent in such proportions that chlorine dioxide is produced in a reaction medium which is maintained at a temperature of from about 50.degree. C. to about 100.degree. C. and at an acidity within a range of from about 2 to about 11N and which is subjected to subatmospheric pressure sufficient for evaporating water. A mixture of chlorine dioxide and water vapor is withdrawn from an evaporation zone in the reaction vessel, and alkali metal sulfate is precipitated in a crystallization zone in the reaction vessel. Straight chained alcohols with the formula CH.sub.2 OH(CHOH).sub.n CH.sub.2 OH where n=0-5, are used as reducing agents. Preferred reducing agents consist of glycol or glycerol. The reaction may also be performed in the presence of a catalyst.

Abstract: A process for the production of chlorine dioxide by reacting in a reaction vessel an alkali metal chlorate, mineral acid and a reducing agent in such proportions that chlorine dioxide is produced in a reaction medium which is maintained at a temperature of from about 50.degree. C. to about 100.degree. C. and at an acidity within a range of from about 2 to about 5N. The reaction medium is subjected to subatmospheric pressure sufficient for evaporating water, a mixture of chlorine dioxide, oxygen and water vapor being withdrawn from an evaporation zone in the reaction vessel, and alkali metal sulfate being precipitated in a crystallization zone in the reaction vessel. As the reducing agent hydrogen peroxide is used.

Abstract: A process for the production of chlorine dioxide by reacting in a reaction vessel an alkali metal chlorate, mineral acid and a reducing agent in such proportions that chlorine dioxide is produced in a reaction medium which is maintained at a temperature of from about 50.degree. C. to about 100.degree. C. and at an acidity within a range of from about 5N to about 11N. The reaction medium is subjected to subatmospheric pressure sufficient for evaporating water, a mixture of chlorine dioxide, oxgen and water vapour being withdrawn from an evaporation zone in the reaction vessel, and alkali metal sulfate being precipitated in a crystallization zone in the reaction vessel. As the reducing agent hydrogen peroxide is used.

Abstract: Chlorine dioxide is produced from sodium chlorate, sulphuric acid and methanol at the boiling point of the reaction medium under a subatmospheric pressure applied to a reaction zone. High purity of chlorine dioxide production is retained while the proportion of acid sodium sulphate in the product is decreased by effecting the reaction at high acidity in a physically-separate reaction zone from which the reaction products discharge into a mass of recycling sodium chlorate solution.

Abstract: The present invention relates to a process for production of chlorine dioxide by reacting in a reaction vessel an alkali metal chlorate, sulfuric acid and methanol as a reducing agent. A reaction medium is maintained at a temperature from about 50.degree. C. to about 100.degree. C. and is subjected to a subatmospheric pressure sufficient to effect evaporation of water whereby a mixture of chlorine dioxide and water vapor is withdrawn from an evaporation region in the reaction vessel and alkali metal sulfate is precipitated in a crystallization region in the reaction vessel. Raw methanol purified by separation and adsorption is used as reducing agent. The raw methanol is purified by dilution with water whereby an unpolar phase is separated and and the remaining methanol-water phase is contacted by an adsorbing agent. The adsorbing agents used can be zeolites, active carbon or polymer adsorbing agents.

Abstract: For the production of a gaseous mixture contains chlorine dioxide and chlorine, alkali chlorate in an aqueous solution with acid is reacted in a reactor. The reactor comprises a plurality of superimposed reaction levels which are traversed by the solution from top to bottom. In the lower portion of the reactor the solution in which chlorate and acid have been depleted is reboiled in a reboiling chamber by an indirect heating at a temperature in the range from 100.degree. to 110.degree. C. The depleted solution is conducted from the reboiling chamber to a pressure chamber, in which a pressure of at least 1.2 bar is maintained. In the pressure chamber the solution is reboiled at temperatures from 110.degree. to 150.degree. C. and the vapors formed by the reboiling in the pressure chamber are conducted through the reboiling chamber for an indirect heating therein.

Abstract: The present invention relates to a process for production of chlorine dioxide by reacting in a reaction vessel an alkali metal chlorate, sulfuric acid and a reducing agent, preferably methanol, in proportions to generate chlorine dioxide in a reaction medium maintained at a temperature from about 50.degree. C. to about 100.degree. C. and an acidity within the interval from 4.8 to 11 N and subjected to a subatmospheric pressure sufficient to effect evaporation of water. A mixture of chlorine dioxide and water vapour is withdrawn from an evaporation region in the reaction vessel and alkali metal sulfate is precipitated in a crystallization region in the reaction vessel. The alkali metal sulfate, which is an alkali metal sesquisulfate, from the crystallization region is heated to the formation of gaseous sulfur trioxide and a neutral alkali metal sulfate. The gaseous sulfur trioxide is absorbed in water to the formation of sulfuric acid.

Abstract: A safe continuous process is disclosed for generating superatmospheric pressure mixtures of chlorine and chlorine dioxide, wherein the chlorine dioxide is generated in situ by chemically reducing inorganic chlorates in aqueous sulfuric acid solutions, and most of the chlorine is supplied from a high-pressure external source. The mixed gaseous products contain Cl.sub.2 and ClO.sub.2 in volumetric Cl.sub.2 /ClO.sub.2 ratios of at least 10/1, and preferably between about 11/1 and 99/1, and are ideally suited for direct use in various industrial treatments, notably in the purification and bleaching of wood pulp and the like.

Abstract: A process and apparatus for producing an aqueous solution of chlorine dioxide and chlorine wherein the likelihood of autodecomposition of chlorine dioxide is significantly reduced or practically eliminated and, in the unlikely event that such CLO.sub.2 autodecomposition occurs, it is quickly detected and the process is automatically corrected.

Abstract: A process for the production of an aqueous solution containing chlorine dioxide and chlorine, which comprises:(a) feeding to a reaction zone a first reactant stream comprising an aqueous solution containing an alkali metal chlorate and an alkali metal chloride;(b) feeding to said reaction zone a second reaction stream comprising an acid admixture of phosphoric acid and sulfuric acid, wherein the weight ratio of said phosphoric acid to said sulfuric acid as expressed as H.sub.3 PO.sub.4 :H.sub.2 SO.sub.4, is from about 1:16 to about 1:3;(c) mixing said first and second reactant streams in said reactant zone; said streams being fed into said reaction zone at rates sufficient to form a reaction product stream comprising an aqueous solution of chlorine dioxide and chlorine in said reaction zone; and(d) withdrawing the resulting aqueous reaction product stream from said reaction zone.

Abstract: A hydrochloric acid-based chlorine dioxide generating process is integrated with an electrolytic process for sodium hydroxide production. Generator liquor in the form of a sodium chloride-enriched solution from the chlorine dioxide generator is passed to the central compartment of a three-compartment cell. Hydrogen ions formed in the anode compartment of the three-compartment cell migrate through a cation-exchange membrane to the central compartment to form hydrochloric acid with the sodium chloride solution while sodium ions migrate through a further cation-exchange membrane to form sodium hydroxide with hydroxyl ions produced in the cathode compartment of the three-compartment cell. The acidified generator liquor containing the hydrochloric acid formed in the central compartment is forwarded to the chlorine dioxide generator to provide half the acid requirement therefor.

Abstract: Chlorine dioxide is generated from chlorate salt and introduced into a treatment stream. Initially following dissolution of the salt in aqueous medium, the solution is subjected to ion exchange for producing intermediate chloric acid. The acid is next converted to chlorine dioxide by electrolysis. The chlorine dioxide produced can then be extracted for use with a treatment stream. The chlorine dioxide generated can be free from unwanted by-products. The total generation system lends itself to recycling of unused product for obtaining virtually complete conversion of chlorate salt to useful chlorine dioxide.

Abstract: Chlorine dioxide is formed by reduction of sodium chlorate in a sulphuric acid-containing reaction medium. Sulphuric acid is introduced to the reaction medium in air atomized form to promote rapid and efficient mixing of the sulphuric acid, thereby avoiding chlorine dioxide decomposition at hot spots resulting from inefficient mixing of acid with the reaction medium.

Abstract: Effluent acid from a non-evaporating chlorine dioxide-generating process is subjected to diffusion-dialysis across an anion-exchange membrane to preferentially transfer sulphuric acid from the effluent acid stream to a recipient aqueous medium while sodium sulphate remains in a waste stream. The sulphuric acid extracted from the effluent acid stream on this way may be recycled to the chlorine dioxide generator, after concentration, if desired.

Abstract: A mixture of sulfuric acid and hydrochloric acid essentially free from dissolved sulfur dioxide to be used in a chlorine dioxide reactor is produced by reacting chlorine and sulfur dioxide in at least two reaction zones. In the bottom of a primary reaction zone the total amount of sulfur dioxide needed for the mixed acid production is introduced in an aqueous mixture of sulfuric and hydrochloric acid containing dissolved chlorine and gaseous chlorine. The sulfur dioxide reacts with chlorine in the aqueous phase to produce sulfuric acid and hydrochloric acid. The mixed acid produced in the primary reaction zone contains dissolved quantities of sulfur dioxide and is forwarded to a secondary reaction zone. Chlorine is introduced into the lower part of the secondary reaction zone. The amount introduced can be the total amount of chlorine to be used in the production of the mixed acid for the chlorine dioxide reactor, or it can be a part of that amount, the balance being introduced in the primary reaction zone.

Abstract: A process for production of chlorine dioxide and chlorine by reacting sodium chlorate with chloride ions and sulfuric acid where the chlorine ions partly are obtained from hydrochloric acid is described. In the process chlorine obtained as a by-product is reacted with sulfur dioxide in a reactor equipped with a condenser. The heat of reaction is removed by keeping the reactor at or above the boiling point of the reaction medium and the vapors are condensed in the condenser and brought back to the reactor. The obtained mixed acid comprising sulfuric acid and hydrochloric acid is returned to the chlorine dioxide reactor.

Abstract: Chlorine dioxide is generated at high efficiency from feeds of chlorate cell liquor, sulphuric acid and methanol by a hybrid of reaction of sodium chlorate with sulphuric acid and methanol and reaction of sodium chlorate with sulphuric acid and sodium chloride. The reaction medium is maintained at its boiling point under a subatmospheric pressure while sodium sesquisulphate precipitates from the reaction medium.

Abstract: A method of generating chlorine dioxide that comprises forming chloric acid by the action of sulphuric acid on a chlorate in a generator in the liquid phase. The chloric acid is reduced to produce chlorine dioxide. The chlorate is fed to the generator as a solid slurry.

Abstract: The present invention provides a process for the continuous production of chlorine dioxide by the reaction of hydrochloric acid with an alkali metal chlorate solution, which is obtained by means of an electrolysis plant from a chlorate solution containing alkali metal chloride circulating in the process, together with cathodically-formed hydrogen, in a cascade reactor with the introduction of air, wherein the reaction of the alkali metal chlorate solution with the hydrochloric acid is carried out under reduced pressure and chlorine gas separated off from the reaction product is reacted with the cathodically-formed hydrogen with the introduction of external chlorine gas to give the required amount of hydrochloric acid.

Abstract: Chlorine dioxide, particularly for water treatment but useful in other applications of chlorine dioxide, such as the bleaching of pulp, is produced in an enclosed reaction zone filled with chlorine dioxide-generating reaction medium under sufficient pressure to prevent chlorine dioxide from forming a continuous gaseous phase and the resulting aqueous solution of chlorine dioxide in spent reaction medium is discharged to a recipient aqueous medium, such as a flowing water body to be treated, without the formation of gaseous phase chlorine dioxide.

Abstract: A method of generating chlorine dioxide that comprises forming chloric acid by the action of sulphuric acid on a chlorate in a generator in the liquid phase. The chloric acid is reduced to produce chlorine dioxide. The chlorate is fed to the generator as a solid.

Abstract: Chlorine dioxide is formed at high efficiency from a solution of acid sodium chlorate at high sulphuric acid normality to which methanol is fed. The reaction medium is at its boiling point under a subatmospheric pressure. Total acid normality values in the range of about 7 to about 9 normal may be used while high efficiency of chlorine dioxide production is maintained.

Abstract: Chlorine dioxide is formed at high efficiency from a solution of acid sodium chlorate at high sulphuric acid normality in excess of 9 normal to which methanol is fed. The reaction medium is at its boiling point under a subatmospheric pressure. The incidence of white-outs is avoided by feeding chloride ions to the reaction medium, while the efficiency of chlorine dioxide production remains high.

Abstract: Highly pure chlorine dioxide is generated very efficiently and safely in a single generator-crystallizer by reducing an alkali metal chlorate with chloride ion in a strong acid in the presence of hydrogen peroxide and a complex catalyst of palladium (II) with chloride ion.

Abstract: The advantages of the serial application of chlorine dioxide and chlorine without intermediate wash during the bleaching of wood pulp in the absence of significant amounts of dissolved organic materials are improved by the presence of small quantities of dissolved chlorine in the chlorine dioxide solution.

Abstract: Chlorine dioxide for waste water treatment is formed by reaction of sodium chlorate, sodium chloride and sulphuric acid at high acidity while the reaction zone is subjected to subatmospheric pressure and spent reaction medium overflows from the reaction zone. The subatmospheric pressure preferably is applied using a water eductor to which the water to be treated is fed, so that direct contact between the produced gases and the water to be treated is effected.

Abstract: The adverse effects of dissolved organic material in the aqueous phase of pulp suspensions during bleaching using mixtures of chlorine dioxide and chlorine are overcome by applying the chlorine dioxide and chlorine serially to the pulp in two steps without an intermediate wash. An aqueous solution of chlorine dioxide and chlorine in which the chlorine constitutes from about 6 to about 10% of the total available chlorine of the solution is used in the first step and chlorine is used in the second step. The aqueous solutions are formed by dissolving in water chlorine dioxide and chlorine formed in a chlorine dioxide generator.

Abstract: The advantages of the serial application of chlorine dioxide and chlorine without intermediate wash during the bleaching of wood pulp in the absence of significant amounts of dissolved organic materials are improved by the presence of small quantities of dissolved chlorine in the chlorine dioxide solution.

Abstract: A process for the production of chlorine dioxide by the reaction of an alkali metal chlorate and hydrochloric acid in aqueous solution at temperatures of from about 35.degree. to about 70.degree. C. wherein the chlorate and the hydrochloric acid are introduced into a first reaction zone (the primary reactor) and after a residence time of two to ten minutes the reactants are fed through a system of reaction zones (secondary reactors) filled and emptied in sequence, the temperature of the reaction mixture in each secondary reactor being equal to or at most 15.degree. C. above that in the primary reactor, the residence time in each secondary reactor being from 20 to 40 minutes, the process permitting the use of less expensive reactor materials, such as polyvinyl chloride, with consequent savings in the cost of the reactors so employed.

Abstract: A mixture of hydrochloric acid and sulphuric acid for use as a feed to a chlorine dioxide generator to provide reactant chemicals therefor is formed by the reaction of chlorine, sulphur dioxide and water. The reaction is effected in the presence of excess chlorine to avoid the presence of dissolved sulphur dioxide in the acid mixture. The proportion of the excess of the chlorine also can be used to control the strength of the acid mixture which can be made without dissolved sulphur dioxide.

Abstract: A chlorine dioxide generating process is described wherein chlorine formed with the chlorine dioxide is used to form acid reactant for the chlorine dioxide generating process by reaction with sulphur dioxide and water. The substantial evaporation of the water which would otherwise result from the exothermic nature of the reaction is prevented by controlling the temperature of the water during the reaction. In one embodiment, the temperature control is achieved by effecting the reaction in a cooled falling film absorber having integral cooling passages and to which liquid water is fed to form the falling film. In another embodiment, the reaction is effected in a packed tower with a substantial proportion of the product acid being recycled through an external heat exchanger and diluted with water.

Abstract: A catalyst together with a heterogeneous catalytic method for making chlorine dioxide from an acid and a metal chlorate solution. The catalyst generally comprises at least one of a valve metal oxide, ruthenium oxide, iridium oxide, palladium oxide, platinum oxide and rhodium oxide.

Abstract: From a chlorate cell liquor containing an alkali metal chlorate, an alkali metal chloride and Cr(VI) ions, Cr(VI) ions are recovered by means of a combination of simple chemical procedures and re-used in an electrolysis step for manufacturing an alkali metal chlorate.

Abstract: In the continuous production of chlorine dioxide wherein an alkali metal chlorate solution is reacted with hydrochloric acid in a reactor through which an air stream is passed countercurrent to the alkali metal chlorate solution, and there discharged from the reactor chlorine dioxide and alkali metal chloride solution, the improvement which comprises including chlorine gas in the air stream, thereby permitting the overall efficiency of the process to be increased at a given content of chlorine dioxide in the gas discharged from the reactor.

Abstract: A catalyst together with a catalytic method for making chlorine dioxide from an acid and a metal chlorate solution. The catalyst generally comprises at least one of a valve metal oxide, ruthenium oxide, iridium oxide, palladium oxide, platinum oxide and rhodium oxide.

Abstract: 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.

Abstract: The adverse effects of dissolved organic material in the aqueous phase of pulp suspensions during bleaching using mixtures of chlorine dioxide and chlorine are overcome by applying the chlorine dioxide and chlorine serially to the pulp in two steps without an intermediate wash. An aqueous solution of chlorine dioxide and chlorine in which the chlorine constitutes from about 6 to about 10% of the total available chlorine of the solution is used in the first step and chlorine is used in the second step. The aqueous solutions are formed by dissolving in water chlorine dioxide and chlorine formed in a chlorine dioxide generator.

Abstract: The advantages of the serial application of chlorine dioxide and chlorine without intermediate wash during the bleaching of wood pulp in the absence of significant amounts of dissolved organic materials are improved by the presence of small quantities of dissolved chlorine in the chlorine dioxide solution.

Abstract: A process for the production of chlorine dioxide by membrane electrolysis of aqueous sodium chloride, reaction of hydrogen and chlorine so-formed to form hydrogen chloride and reaction of the so-formed hydrogen chloride with the sodium chlorate also formed by the electrolysis to form chlorine dioxide is disclosed. Also disclosed is the production of chlorine by such a process.

Abstract: A modular chlorine dioxide generating unit (10) is disclosed wherein recycled reaction mixture passes along a flow path (18) internally of the generator vessel (12) out of direct fluid flow communication with the reaction medium (13) from the lower end (16) of the vessel (12) to a discharge point in the vapor phase (15 ) above the liquid level (13) in the generator vessel (12).

Abstract: 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.

Abstract: 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.

Abstract: The proportion of chlorine dioxide to chlorine in aqueous solutions formed from gaseous mixtures of chlorine dioxide and chlorine is improved over conventional separation techniques. The gaseous product stream from a chlorine dioxide generator is scrubbed with an aqueous salt mixture containing an approximately stoichiometric quantity of sodium hydroxide, which reacts preferentially with the chlorine, yielding chlorine dioxide of high purity. The absorption system is operated under such conditions that the chlorine is converted to sodium chlorate and sodium chloride, which may then be recirculated to the chlorine dioxide generating system. The scrubbing salt solution is adjusted so as to produce an R-2 mixture upon reaction with the chlorine in the chlorine/chlorine dioxide stream.

Abstract: An improved process is provided for the production of chlorine dioxide and chlorine wherein a chlorine dioxide generator may be operated interchangeably in either sulfuric acid or hydrochloric acid mode without changing acidity levels or evacuating the liquor of one mode and refilling with liquor of the second mode before continuing generation. The versatile process for production of chlorine dioxide comprises maintaining saturated solutions of both alkali metal chloride and alkali metal sulfate in the generator at an acid normality of from about 2 to about 11 in the presence of a small amount of catalyst selected from the group consisting of vanadium pentoxide, silver ions, manganese ions, dichromate ions and arsenic ions. Thus, the instant process provides high yields of chlorine dioxide even at high acidities making it possible to manufacture balanced quantities of saltcake and alkali metal chloride by-products as may be required.

Abstract: The entrainment of reaction medium in the vapor phase is decreased in a chlorine dioxide generator producing a gaseous mixture of chlorine dioxide, chlorine and steam from a boiling reaction medium and wherein generator liquor is recycled with make up chemicals by providing a tangential entry of recycled liquor to the generator in the vapor space above the liquid level in the generator and a helically-arranged baffle projecting inwardly from the generator wall at least in the height of the generator corresponding to the tangential entry opening into the vapor space. The baffle is arranged to be above the trajectory of the recycled liquor as it enters the generator. Decreased liquor entrainment enables the generator diameter to be decreased, with consequentially decreased capital costs.