| 摘要 |
A method and apparatus for regulating reaction rate between a gaseous bleaching reagent and wood pulp in a bleaching system, of the type having a mechanically agitated pulp contactor (120), including the steps of co-currently or counter-currently introducing a recirculated contacting gas (R) for diluting freshly supplied reagent gas (F) and for thereby reducing the initial reaction rate between the reagent and pulp. Except for the initial reaction rate, overall bleaching performance is quite insensitive to wide variations in the amount of recirculating gas (R) introduced. This allows adjustment of flow rate to control gas velocity through the contactor (120) for purposes of overall bleaching efficiency. Degradation of pulp fibers due to overbleaching is virtually eliminated, and uniformity of bleaching is greatly enhanced without any sacrifice in production rate. |
