| 摘要 |
<p>The process consists of an alkaline extraction stage reinforced with at least some of the oxygen from the chemicals, hydrogen peroxide and ozone prior to final bleaching which can comprise one or more stages. Prior to the alkaline extraction stage, the pulp-water suspension is treated partly with a sulphur dioxide soln. which is added at the rate of 1-20 kg SO2/ton of pulp, with the property of reducing heavy metals in the suspension, including manganese, and partly with at least one complex builder with the ability to bind at least the main parts of the manganese and other heavy metals. The pulp is then washed before the reinforced alkaline extraction stage. As complex builder can be used at least some of the following: diethylene triamine penta-acetic acid, ethylene diamine tetra-acetic acid, nitrolo tri-acetic acid, citric acid and tartaric acid.</p> |
