Abstract: A process for adjusting the pH of a cellulosic pulp in a pulp and/or paper mill, and to the production of pulp, paper or board from so treated cellulosic pulp is disclosed. In the process, the pH of an alkaline cellulosic pulp is adjusted at least twice with carbon dioxide before a neutral treatment and at least once with a strong acid before a subsequent acidic treatment. Between the first and the second carbon dioxide induced pH adjustment there is provided a (bi)carbonate removal step, which reduces the buffering capacity of the pulp. Also provided for is the use of (bi)carbonate removal for reducing the consumption of acid in the treatment of a cellulosic pulp.

Abstract: The invention relates to a process for the deresination of pulp as well as to the use of carbon dioxide or a (bi)carbonate compound for the deresination of pulp. The process concerns the removal of wood extractives or resin from an aqueous pulp suspension in an alkaline process stage of the pulping process, such as an oxygen delignification stage, at a pH above 10. Carbonate ions are provided in the pulp at the high pH for solubilizing a significant part of the wood extractives in the pulp. The alkaline pulp is dewatered to remove solubilized extractives and for providing a deresinated pulp.

Abstract: The invention refers to a method for an integrated treatment of cellulose pulp. The method includes the steps: providing said cellulose pulp (1), providing a determined quantity of white liquor (2) including alkali and sulphur components, providing an oxygen-containing gas, oxidizing (5) the sulphur components of the white liquor by the supply of a part of said gas in such a way that at least a part of the sulphur is present in the form of sulphate, transporting the cellulose pulp having a certain kappa number to at least one mixing device (4), and supplying the oxidized white liquor from the oxidizing step to the cellulose pulp, supplying a part of said gas to the cellulose pulp in said mixing device, mixing the cellulose pulp with the oxidized white liquor and said gas in said mixing device, and transporting the cellulose pulp from said mixing device to a delignification reactor (6) for oxygen delignification of said cellulose pulp, wherein the kappa number is reduced.

Abstract: A process for the bleaching of lignin present in pulp fibers in an aqueous environment such as a pulp suspension. The invention also relates to a process for producing paper or board from pulp containing bleached lignin. According to the invention carbon dioxide is used for the bleaching of lignin.

Abstract: A method of treating cellulose pulp which is subjected to an oxygen-delignification stage (3), a washing stage (4), an ozone-bleaching stage (1) and a further bleaching stage, for instance a peroxide-bleaching stage (7). A gas mixture of oxygen and ozone is delivered to the ozone-bleaching stage (1). The used gas mixture is regenerated, i.e. freed from carbon dioxide, and returned to the oxygen-delignification stage (3) and/or to a bleaching stage (7).