Multi-stage bleaching process including an enhanced oxidative extraction stage
AssigneeInternational Paper Company
InventorArthur J. Nonni
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Abstract
A multi-stage process for the delignification and bleaching of lignocellulosic pulp is disclosed wherein the first alkaline extraction stage comprises extracting the pulp with caustic in the presence of oxygen and either a hypochlorite or a peroxide.
Claims26
A multi-stage bleaching process including at least one alkaline extraction stage for the bleaching and delignification of lignocellulosic pulp wherein the first alkaline extraction stage comprises extracting the pulp with caustic in the presence of from about 0.2 to about 1.0% oxygen, based on the oven-dry weight of the pulp, and from about 0.05% to about 1.0% of a hypochlorite, based on the oven-dry weight of the pulp, or from about 0.05% to about 1.0% of a peroxide, based on the oven-dry weight of the pulp.
A sequential multi-stage process for the bleaching and delignification of lignocellulosic pulp, which comprises:
- (a) treating the lignocellulosic pulp with oxygen, ozone, peroxide, chlorine, chlorine dioxide, or mixtures of chlorine and chlorine dioxide, in an initial stage;
- (b) extracting the pulp with caustic in the presence of from about 0.2 to about 1.0% of oxygen, based on the oven-dry weight of the pulp, and from about 0.05% to about 1.0% of a hypochlorite, based on the oven-dry weight of the pulp, or from about 0.05% to about 1.0% of a peroxide, based on the oven-dry weight of the pulp in a first alkaline extraction stage.
A sequential multi-stage process for the delignification and bleaching of lignocellulosic pulp, which comprises:
- (a) delignifying the lignocellulosic pulp with oxygen;
- (b) treating the pulp with chlorine, chlorine dioxide, or mixtures thereof;
- (c) extracting the pulp with caustic in the presence of from about 0.2 to about 1.0% of oxygen, based on the oven-dry weight of the pulp, and from about 0.05% to about 1.0% of a hypochlorite, based on the oven-dry weight of the pulp, or from about 0.05% to about 1.0% of a peroxide, based on the oven-dry weight of the pulp in a first alkaline extraction stage.
Dependencies are inferred from the claim text.