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Kraft-Pulping of Hot Water Extracted Woodchips

a hot water extraction and pulping technology, applied in the field of kraft pulping of hot water extracted wood chips, can solve the problems of high energy cost and damage to lignocellulosic fibers, and limiting the number of pulp applications, so as to reduce the weight of pulp, increase the bulk, and reduce the effect of pulp weigh

Inactive Publication Date: 2011-03-31
THE RES FOUND OF STATE UNIV OF NEW YORK
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The present invention is about a method for making pulp from lignocellulosic materials. The method involves several steps, including reducing the weight of the material, increasing its viscosity, or increasing the yield of the material. This is done by contacting the material with hot water or steam, which breaks it down and produces acetic acid. The pH is then lowered, and the material is removed from the vessel. It is then exposed to pulping chemicals, which form a pulp with a specific quality. The pulp is then exposed to whitening agents, resulting in a whitened, high-quality material. Overall, this method allows for efficient and effective pulping of lignocellulosic materials.

Problems solved by technology

It is a high-yield process but suffers from high energy costs and damage to the lignocellulosic fibers.
This damage produces lower strength paper.
These disadvantages (cost and quality) limit the number of applications for pulp.
One problem associated with the Kraft pulping process is non-uniformity of the pulp formed from the lignocellulosic material.
Incomplete penetration and inadequate diffusion of chemicals into lignocellulosic material remain the primary reasons for improper delignification and lower quality pulp.
Another problem associated with the Kraft pulping process is that the harsh chemicals used during the Kraft pulping process dissolve about 20-30% of the wood weight into the pulping liquor, this lost wood weight being in the form of lignin and hemicellulose.
The prior art has had difficulty in isolating hemicelluloses, with the majority of hemicelluloses being dissolved during Kraft pulping and discharged after pulping with the rest of the pulping liquor.
The inability to capture a pure stream of a hemicellulose has limited the overall economic efficiency of the pulping process.
Thus, conventional pulping does not address at least one major aspect of commercial exploitation of lignocellulosic materials, mainly the use of extracted hemicellulose.

Method used

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  • Kraft-Pulping of Hot Water Extracted Woodchips
  • Kraft-Pulping of Hot Water Extracted Woodchips
  • Kraft-Pulping of Hot Water Extracted Woodchips

Examples

Experimental program
Comparison scheme
Effect test

example 1

[0055]In all of the following examples, the lignocellulosic material used was Eucalyptus wood chips, unless otherwise noted. Although Eucalyptus wood chips were used as the lignocellulosic source, any lignocellulosic material could be used.

[0056]A liquor (water) to lignocellulosic material ratio of 4:1 was added to a vessel capable of holding pressure, for example a high pressure laboratory M / K circulation digester and brought from about room temperature to about a temperature of 160° C. over about a 40 minute period. During this hot water contacting time, acetic acid was produced through an auto-hydrolysis reaction to reach a concentration of about 0.06M.

[0057]The vessel was maintained at this temperature for about 30 minutes to about 80 minutes. The extracted lignocellulosic material was then thoroughly washed with water to remove dissolved substances. The remaining liquor in the vessel was then separated into its constituents.

[0058]The mass which was removed during hot water cont...

example 2

[0060]FIG. 5 shows the UV light absorptivities of the liquid, or black liquor, within the pulping reactor during the pulping process at 280 nm during the kraft pulping of hot-water extracted wood chips and control woodchips. Time zero represents when the reactor contents, including woodchips, water and an initial concentration of active alkali at 16% and sulfide at 18%, have been mixed for 15 minutes at room temperature, with the temperature about to be raised. The active alkali is the percentage of equivalent Na2O in the solution and the sulfidity is the ratio of Na2S (or specifically its equivalent in Na2O) to the total Na2O. The temperature reached 150° C. in about 30 minutes, and was maintained at that temperature. Based on FIG. 5, there is a noticeable increase in UV light absorptivities at 280 nm during the initial de-lignification periods (from the start of the temperature raise to around 70 minutes), after which the absorptivity increased more slowly and leveled off towards ...

example 3

[0061]FIG. 6 shows the sodium hydroxide concentration in the black liquor as a function of time during chemical pulping for control and hot-water extracted wood chips. Initially sodium hydroxide was added to water in the pulping reactor at a concentration of about 0.956 Molar, followed by the addition of woodchips. The contents of the pulping reactor were mixed for 15 minutes at room temperature. The temperature was increased to about 150° C. over about 30 minutes. As can be seen in FIG. 6, during the first 30 minutes, the drop in alkali concentration in the black liquor was very rapid for hot-water extracted woodchips. More alkali was consumed at a faster rate for the pulping of hot-water extracted woodchips as compared to the control chips, and the residual concentration of alkali was much higher in the control wood chips as compared to the hot-water extracted wood chips.

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Abstract

The method of the present invention is directed towards a method to increase the pulp yield of a lignocellulosic material, or increasing pulp bulk and / or pulp viscosity. This method comprises the following steps; preparing a lignocellulosic material, contacting the lignocellulosic material in a vessel with hot water or steam for a predetermined time, producing acetic acid from the reaction of the hot water or steam and the lignocellulosic material, lowering the pH to less than about 4, removing lignocellulosic material extracts including a large percentage of hemicellulose, acetic acid and metal ions, exposing contacted lignocellulosic material to pulping chemicals in a pulping reactor, forming a contacted lignocellulosic material pulp with a kappa number below about 19 after about 90 minutes of contact with the pulping chemicals, exposing the contacted lignocellulosic material pulp to whitening agents, and producing a whitened hot water contacted lignocellulosic material pulp.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application claims the benefit of U.S. Provisional Application No. 61 / 233,704 filed on Aug. 13, 2009, the entire contents of which are incorporated herein by reference.FIELD OF THE INVENTION[0002]The invention relates generally to the field of Kraft pulping of hot-water extracted wood chips. More specifically, the present invention is directed to treating lignocellulosic materials with a hot water extraction process to remove a substantial portion of hemicellulose, Kraft pulping the treated lignocellulosic material, thereby producing a lighter pulp with a lower lignin concentration, lower production time and / or lower chemical charge with lower residual chemical content.BACKGROUND OF THE INVENTION[0003]There are a number of processes that convert lignocellulosic materials to pulp. Lignocellulosic materials comprise cellulose, lignin and hemicellulose, with conventional pulping operations recovering the cellulose in the form of long, f...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): D21C1/02D21C3/22D21C3/02
CPCD21C1/02D21C3/22D21C3/02
Inventor LIU, SHIJIEMISHRA, GANGESHAMIDON, THOMAS E.GRATIEN, KATHRYN E.PUTNAM, JENNIFER A.
Owner THE RES FOUND OF STATE UNIV OF NEW YORK
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