Pulping process for quality protection including methods for hemicellulose extraction and treatment of hemicellulose-extracted lignocellulosic materials

Abstract

A method for producing pulp by extracting hemicellulosic materials from lignocellulosic materials using water in an extraction stage, wherein the extraction stage is either a single extraction or a double extraction process; treating the lignocellulosic materials with an oxidizing agent in a treatment stage, wherein the treatment stage is selected from the group consisting of a second extraction process, an agent impregnation process, and a first pretreatment process; treating the lignocellulosic materials with a reducing agent in the treatment stage, wherein the treatment stage is selected from the group consisting of the second extraction process, the agent impregnation process, and a second pretreatment process; and then subjecting the lignocellulosic materials to a modified Kraft pulping process to produce pulp.

Description

STATEMENT OF RELATED APPLICATIONS[0001]This patent application claims priority on and the benefit of U.S. provisional patent application No. 61 / 165,995 having a filing date of 2 Apr. 2009, which is incorporated herein in its entirety by this reference.BACKGROUND OF THE INVENTION[0002]1. Technical Field[0003]This invention is related generally to the field of pulping processes preceded by hemicellulose extraction, and is related more specifically to modified pulping processes, and particularly modified Kraft pulping processes, preceded by a hemicellulose extraction process, that maintain yield and quality of pulp. This invention also is related to the field of yield and strength advantages that can be achieved by modified pulping processes compared to Kraft pulping processes not preceded by hemicellulose extraction.[0004]2. Prior Art[0005]Pulping is the process of converting wood or other lignocellulosic materials into separated pulp fibers for use in, for example, paper making. Comm...

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Benefits of technology

[0007]The present invention, briefly stated, includes modified pulping processes preceded by hemicellulose extraction processes in which hemicellulosic materials, such as polysaccharides and other organic compounds, are extracted from the lignocellulosic materials prior to pulping. The hemicellulosic materials are extracted prior to pulping and chemicals and / or other compounds are added to the lignocellulosic materials prior to or during pulping to compensate for the loss of the hemicellulosic materials. Using the present invention, the hemicellulosic materials can be removed as value added byproducts of the pulping process, yet the addition of the chemicals and / or other compounds to the lignocellulosic materials results in a yield and quality of pulp similar to conventional pulping processes, such as Kraft pulping processes. Thus, the present invention results in more economical pulping process, in which byproducts can be extracted and sold, while still yielding a quantity and quality of pulp similar to conventional pulping processes not having such a byproduct removal and capture.

[0008]The pulp industry has recognized that it has to continue to produce chemical pulp but also must look for additional revenue streams form existing technologies. For example, in the present invention, instead of simply taking wood chips and taking out the lignin, hemicellulosic materials can be removed and rather than leaving the hemicellulosic materials in the black liquor to be disposed of, some of the hemicellulosic materials can be removed and used to produce higher value byproducts. Most are polysaccharides (sugars) that have a potentially high value can be used to make ethanol or other chemicals, for example. However, in a typical extraction process, pulling out some of the hemicellulosic materials reduces the amount of wood that can go to pulping. If a significant amount of hemicellulosic materials are removed, the pulp may have different characteristics from the prior art pulp. The present invention addresses this by providing for the extraction of hemicellulosic materials while maintaining the pulp yield and the properties of the pulp.

[0009]The present invention comprises continuous processes for protecting hemicellulose pre-extracted lignocellulosic materials, such as wood chips, against degradation in alkaline pulping processes. One aspect of the present invention is the evolution of existing chemical pulp mills into integrated forest biorefineries (IFBR) for the production of value added products. For example, using the present invention, one selectively and efficiently can pre-extract hemicelluloses before pulping while maintaining the yield and quality of the pulp. Another aspect of the present invention is that the modified pulping process can be used in place of the Kraft process to achieve yield gain at the same level of lignin removal without any reduction in the pulp properties.

Problems solved by technology

However, in a typical extraction process, pulling out some of the hemicellulosic materials reduces the amount of wood that can go to pulping.

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