| 摘要 |
The pulp is fed (1) to a first stage vessel after mixing (2) with oxygen and alkali. Vessel (3) operates at a pressure of over 3 bar. Additional oxygen as hydrogen peroxide with more alkali is mixed (9) and fed to second vessel (4) with low pressure steam for heating purposes. Vessel (4) operates at 90-120 deg C and the pressure is adapted to the operating temperature. Preferably most oxygen and alkali is added to mixer (2) just after pump means (1). Hydrogen peroxide at up to 5Kg per ton and more alkali are added before the downward flowing second treatment vessel (4). Low pressure steam can be used to heat said vessel (4) to a temperature in the range 90-120 deg C. A gas space at the top of vessel(4) allows degassing (6) of the pulp with heat recovery by flashing (5,7) or by heating dilution liquids to further improve the process economy. |
