| 摘要 |
<p>The present invention relates to a method of bleaching sulfate cellulose pulp to a brightness of at least ISO 85 by using at least two of the following bleaching chemicals: oxygen, ozone, and peroxide. Characteristic features of the invention are that the pulp is digested; subjected to a heavy metals removal treatment with at least one of the following treatment agents or methods: acidification, EDTA, and DTPA; delignified in a pressurized two-step oxygen stage; and bleached at least in one acid peroxide stage.</p> |
