Erco Industries Limited

Erco Envirotech Ltd.

Tenneco Canada Inc. (erco Division)

471199 Ontario Limited

Douglas W Reeve

W Howard Rapson

Gordon Rowlandson

Hoc N Tran

Raymond C Francis

The extent of delignification of chemical pulps by oxygen-containing chemicals, preferably hydrogen peroxide, is enhanced by demethylating the pulp prior to such oxidative delignification, to a degree of demethylation of at least about 30%, preferably at least about 50%. Demethylation may be achieved by chemical treatment of the already-formed pulp or by modification to the pulping process to result in demethylated pulp.

Process for the oxidative delignification of demethylated chemical pulp

A deposit measuring device, useful for improving combustion processes especially kraft mill recovery boilers, determines the temperature at the windward and leeward sides of a probe tube positioned in the flue gas stream transverse thereto and then determines the rate of build-up of deposits on at least the windward side and the temperature of the flue gas stream. This information is used by an operator or automatically to control boiler operations. The measuring device has a deposit removal means associated therewith periodically to remove deposits from the tube. The ability to control the boiler operation enables considerable economic benefits to be achieved.

Control of boiler operations

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.

Bleaching procedure using chlorine dioxide and chlorine solutions

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.

Method of bleaching pulp with an aqueous solution of chlorine dioxide

A pulp mill bleach plant operation having a low effluent volume, a low consumption of water, energy and chemicals, and yet provides efficient bleaching, caustic extraction and washing is described. Water conservation is practised by controlling the use of wash water in the bleach plant, controlling the design and operation of washers, deckers and other mechanical devices used in the bleach plant and controlling the inflow of water with chemicals. An aqueous polluting effluent-free pulp mill water utilization system is also described.

Low effluent pulp mill, bleach plant operation

Bleach plant operation

Acid and alkaline filtrates are separated from the bleach plant of a bleached pulp mill for use in washing unbleached pulp free from entrained pulping liquor. Acid effluent is neutralized with sodium hydroxide solution prior to use in the washing as the last washing step while alkaline filtrate is used in the remainder of the washing. Part of both the acid and alkaline filtrates are not used in the washing to allow bleed of calcium value and caustic extraction stage solids which otherwise would build up on the washed pulp mat passing to the bleach plant.

Bleach plant filtrate recovery

Sodium chloride is removed from Kraft mill smelts by fractionating the smelt to separate sodium carbonate and sodium sulphate in solid form from sodium sulphide and sodium chloride which usually is contaminated with residual quantities of sodium carbonate and sodium sulphate and is contained in an aqueous solution thereof. Sodium chloride subsequently is separated from the aqueous solution. Various fractionation procedures are described and various procedures for the removal of the sodium chloride in substantially pure form also are described.

Removal of dissolved salts from sulphide liquors

In the recovery and regeneration of spent pulping chemicals from the production of cellulosic fibrous material pulp there is provided a white liquor containing dissolved quantities of sodium chloride and unregenerated pulping chemicals. The white liquor is concentrated by evaporation to deposit therefrom sodium chloride and unregenerated pulping chemicals, unregenerated pulping chemicals substantially free from sodium chloride are recovered from the deposited materials, and sodium chloride is separated and recovered from the deposited materials. The deposition of sodium chloride and unregenerated pulping chemicals is usually carried out in two stages, with unregenerated pulping chemicals substantially free from sodium chloride being deposited in the first stage. The sodium chloride then is deposited in the second stage, possibly in admixture with unregenerated pulping chemicals, in which event substantially pure sodium chloride is separated from the deposited mixture. At least part of the unregenerated pulping chemicals substantially free from sodium chloride are forwarded to the spend pulping liquor.

Growing community of inventors

Orton, Canada

Douglas W Reeve