OZONE BLEACHING

摘要

A method and reactor for bleaching pulp with ozone in a pressurized vessel (1), the ozone being mixed into the pulp by a mixer (4) to form a homogenous gas-pulp mixture, and then stirring said mixture at consecutive points along the bleaching line by devices (25) with agitators (26) to improve the reaction conditions. According to the invention the quantity of ozone amounts to at least 3 kg per ADMT, and the entire quantity of gas-pulp mixture passing through a cross-sectional area of the bleaching line is subjected to stirring so that the gas-pulp mixture finally contains less than 10 % of said quantity of ozone. Further the first stirring and each subsequent stirring take place from near 0 to about 10 seconds after the initial mixing and the previous stirring, respectively, with respect to the feed speed of the gas-pulp mixture. The bleaching is finished by reducing the pressure in the gas-pulp mixture to remove a carrier gas for ozone and any remaining ozone.