Abstract: Methods for bleaching oxygen delignified and washed pumps having a consistency of between 8 and 20% are disclosed including a first chlorine dioxide bleaching step, washing the bleached pulp, subjecting the washed pulp to an alkaline extraction step to obtain an alkali-containing pulp, adding chlorine dioxide and adjusting the pH in a second chlorine dioxide bleaching step performed directly after the alkaline extraction step without an intermediate washing step, and subjecting the bleached alkali-containing pulp to a peroxide treatment step directly after the second chlorine dioxide bleaching step or with an intermediate washing step prior to the peroxide treatment step.

Abstract: Methods for bleaching oxygen delignified and washed pumps having a consistency of between 8 and 20% are disclosed including a first chlorine dioxide bleaching step, washing the bleached pulp, subjecting the washed pulp to an alkaline extraction step to obtain an alkali-containing pulp, adding chlorine dioxide and adjusting the pH in a second chlorine dioxide bleaching step performed directly after the alkaline extraction step without an intermediate washing step, and subjecting the bleached alkali-containing pulp to a peroxide treatment step directly after the second chlorine dioxide bleaching step or with an intermediate washing step prior to the peroxide treatment step.

Abstract: Methods for bleaching chemical pulp are disclosed including dewatering the pulp to a concentration of from 25 to 40%, bleaching in a first chlorine dioxide stage, followed by a second alkaline bleaching stage, followed by a third chlorine dioxide bleaching stage, dewatering the bleached pulp to a concentration of from 10 to 40% and producing a filtrate, and recycling the filtrate to control the pulp concentration of the dewatered chemical pulp to from 8 to 15% in the first bleaching stage.

Abstract: A method of bleaching chemical pulp, comprising two bleaching stages (D0 and, respectively, D1) with chlorine dioxide as dominating bleaching chemical and at least one intermediate alkaline bleaching stage (E). The ingoing pulp is dewatered to a concentration of 25-40% before the first chlorine dioxide stage (D0) and to 10-40% after the second chlorine dioxide stage (D1). Filtrate from the dewatering after the second chlorine dioxide stage (D1) is re-cycled and utilized for controlling the pulp concentration to 8-15% of the dewatered pulp to the first chlorine dioxide stage (D0).

Abstract: Methods for oxygen delignification of a pulp are disclosed, including initially delignifying the pulp at a delignification temperature of less than 90° C., adding oxygen to the pulp so that the oxygen is present during the initial delignification step, and further delignifying the pulp at a delignification temperature of greater than 90° C., the difference between the two delignification temperatures being less than about 20° C., and the pressure being greater in the initial delignification step. The method also includes adding alkali solely to the initial delignification step in order to obtain high alkalinity therein.

Abstract: Methods for oxygen delignification of a pulp are disclosed, including initially delignifying the pulp at a delignification temperature of less than 90° C., adding oxygen to the pulp so that the oxygen is present during the initial delignification step, and further delignifying the pulp at a delignification temperature of greater than 90° C., the difference between the two delignification temperatures being less than about 20° C., and the pressure being greater in the initial delignification step. The method also includes adding alkali solely to the initial delignification step in order to obtain high alkalinity therein.

Abstract: Methods for oxygen delignification of a pulp are disclosed, including initially delignifying the pulp at a delignification temperature of less than 90° C., adding oxygen to the pulp so that the oxygen is present during the initial delignification step, and further delignifying the pulp at a delignification temperature of greater than 90° C., the difference between the two delignification temperatures being less than about 20° C., and the pressure being greater in the initial delignification step. The method also includes adding alkali solely to the initial delignification step in order to obtain high alkalinity therein.

Abstract: Methods for oxygen delignification of a pulp are disclosed, including initially delignifying the pulp at a delignification temperature of less than 90° C., adding oxygen to the pulp so that the oxygen is present during the initial delignification step, and further delignifying the pulp at a delignification temperature of greater than 90° C., the difference between the two delignification temperatures being less than about 20° C., and the pressure being greater in the initial delignification step. The method also includes adding alkali solely to the initial delignification step in order to obtain high alkalinity therein.

Abstract: Methods for oxygen delignification of a pulp are disclosed, including initially delignifying the pulp at a delignification temperature of less than 90° C., adding oxygen to the pulp so that the oxygen is present during the initial delignification step, and further delignifying the pulp at a delignification temperature of greater than 90° C., the difference between the two delignification temperatures being less than about 20° C., and the pressure being greater in the initial delignification step. The method also includes adding alkali solely to the initial delignification step in order to obtain high alkalinity therein.

Abstract: Methods of treating process water containing metal ions is disclosed including contacting the process water with a pulp comprising lignocellulose-containing material at a pH of above about 7 and a temperature of from about 50.degree. to 120.degree. C. whereby at least a portion of the metal ions are removed from the process water. Preferably the process water is produced from initially washing a pulp solution prior to a bleaching step employing hydrogen peroxide or ozone.