Medium consistency pulp ozone bleaching.

摘要

Medium consistency (e.g. about 6-15%) paper pulp (from 38) is effectively bleached with ozone (from 16) 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 (12); the intimate uniform mixture produced is then passed upwardly in a reaction vessel (17) 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 (21) leading to a gas zone in a large diameter retention vessel (22). A pressurized gas pad (26) is maintained at and above the introduction of the pulp into the retention vessel, while the level (29) 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 The pulp may be withdrawn from the retention vessel with a fluidizing degassing pump (32), and the pressurized gas removed from the top of the vessel (through 35) may be fed to an apparatus (61) using oxygen gas under pressure. <IMAGE> <IMAGE>