Kamyr, Inc.

Ahlstrom Machinery, Inc.

Stephen J Dunn

Erwin D Funk

Kaj Henricson

Brian F Greenwood

Joseph R Phillips

Toivo J Niskanen

Kari Peltonen

Mika P Makela

A method and apparatus supply ozone containing gas under superatmospheric pressure to an ozone delignification device. The speed of a water ring compressor is controlled so that it compresses as much ozone gas per unit time at desired superatmospheric pressure as the ozone delignification unit utilizes, with essentially no excess. The ozone containing gas is fed from the water ring compressor through a separator buffer tank which levels out pressure pulses and separates cooling water from compressed ozone gas prior to the gas entering the ozone delignification unit. The gas passes through a control valve controlled by a mass flowmeter which senses the amount of cellulose pulp fed to the ozone delignification unit. The speed control of the compressor may be provided by a differential pressure controller connected across the control valve.

Method of controlling pressurized ozone to a pulp delignification reactor

Medium consistency (e.g. about 6-15%) paper pulp is effectively bleached with ozone in a carrier gas (typically oxygen) by effecting efficient separation of carrier gas from the pulp after reaction with the ozone, and introducing the ozone into the pulp at a pressure of about 10-13 bar. Ozone in oxygen and medium consistency paper pulp are fed to a fluidizing mixer; the intimate uniform mixture produced is then passed upwardly in a reaction vessel until about 99% of the ozone has been consumed, and then separation of gas from the pulp is initiated by moving the pulp mixture into a generally horizontal tube leading to a gas zone in a large diameter retention vessel. A pressurized gas pad is maintained at and above the introduction of the pulp into the retention vessel, while the level of pulp in the retention vessel is maintained below the point of introduction. The pulp may be withdrawn from the retention vessel with a fluidizing degassing pump, and the pressurized gas removed from the top of the vessel may be fed to an apparatus using oxygen gas under pressure.

Medium consistency pulp ozone bleaching

Pressurized ozone pulp delignification reactor and a compressor for

A method and mixer are provided for mixing chemical (such as a gas like chlorine or oxygen) with a slurry (such as paper pulp having a consistency of about 1-16%) in such a way that separation of gas from the slurry at the discharge from the mixer is avoided. Where the mixer housing has a radial discharge, the leading and trailing walls of the discharge (in the direction of circular and tangential movement of slurry within the main body housing of the mixer) present curved configurations to transition the slurry from circular/tangential movement to radial movement. The curvature of the configurations (which may be provided by inserts) does not exceed an angle of about 10 degrees at any point along them until radial flow is established. Alternatively, the discharge may allow the tangential movement of the pulp in the main housing to continue by cutting off the original radial pulp discharge outlet, and welding or otherwise attaching a retrofit new discharge outlet to the main housing body similar to a pump volute with a gradually increasing cross-section.

Minimizing gas separation in a mixer outlet

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Glens Falls, NY, United States of America

Stephen J Dunn