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US 5,688,367 AGranted
Method of monitoring and recovering oxygen-rich gas from ozone bleaching
AssigneeCanadian Liquid Air Ltd./Air Liquide Canada Ltee
InventorsDerek Hornsey, Gordon H. Homer, John R. Ayton
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Abstract
A method and installation for bleaching a lignocellulosic pulp with ozone, while recovering an oxygen-rich gas which may be recycled or re-used. Bleaching of the pulp with ozone is preferably carried out under conditions in which ingress of air is prevented. In a multi-step bleaching process, an oxygen-rich vent gas typically containing at least 90%, by weight, of oxygen may be recovered from a second contactor for potential use in different oxygen-consuming operations in a pulp mill.
Claims15
A method of bleaching lignocellulosic pulp, comprising:
- a) generating ozone from oxygen in an oxygen-containing feed gas;
- b) contacting at least a portion of lignocellulosic pulp with a mixture comprising oxygen and ozone in a first contactor to produce a treated pulp and a first effluent gas, said first effluent gas being suitable for conducting a secondary process wherein a presence of elevated amounts of gases other than ozone and oxygen is tolerated;
- c) transferring at least a portion of said treated pulp to a second contactor, and further treating said pulp portion with a mixture comprising oxygen and ozone, to produce a further treated pulp and a second effluent gas;
- d) recovering a bleach pulp;
- e) recovering said second effluent gas, said second effluent gas being oxygen-rich and being suitable for recycling for ozone generation;
- and
- f) monitoring both the first and second effluent gases and adjusting the properties of the mixtures comprising oxygen and ozone based upon the monitoring of the first and second effluent gases.
4 more elements
Dependencies are inferred from the claim text.