Method for preparing fluff pulp from bamboos and fluff pulp prepared thereby

Patent metadata

Field	Value
Publication number	US-12286750-B2
Application number	US-202218703721-A
Country	US
Kind code	B2
Filing date	Oct 31, 2022
Priority date	Mar 31, 2022
Publication date	Apr 29, 2025
Grant date	Apr 29, 2025

Abstract

Discloses are a method for preparing fluff pulp from bamboos, and the fluff pulp prepared thereby. The method comprises the following steps: treating the bamboos with high-concentration alkali at a relatively mild temperature, after a certain period of treatment, replacing a treatment liquid for separating hemicellulose with a weak black liquor; Kraft cooking the treated bamboos to obtain unbleached bamboo pulp, removing rejects in the unbleached bamboo pulp by using a slotted screen; then removing miscellaneous cells by using a microporous sieve; carrying out two stages of oxygen delignification on the screened pulp; carrying out ECF bleaching treatment of a D 0 EpD 1 P process; and finally obtaining the bamboo fluff pulp which has high whiteness, low DCM extract content, low ash content and long fiber length, contains 4.2-4.6 million fibers per gram, and has relatively high bulkiness.

First claim

What is claimed is:

1. A method for preparing fluff pulp from bamboos, comprising the following steps:
(1) alkali treatment of bamboos: treating a bamboo raw material with an alkali liquor in a cooking digester to obtain a treatment liquid and treated bamboos; wherein a temperature of the alkali treatment in the cooking digester is 60-90° C., a concentration of the alkali liquor is 60-100 g/L, and an alkali in the alkali liquor is sodium hydroxide; a ratio of mass of the bamboos to a volume of the alkali liquor is 1: (3-5) kg/L; and time of the alkali treatment is 60-120 minutes;
(2) separation of the treatment liquid: replacing the treatment liquid in the step (1) with a weak black liquor, and storing a replaced treatment liquid separately in a container for later use; wherein the weak black liquor refers to black liquor extracted from a pulp during washing; and the replacing refers to pumping the weak black liquor into the cooking digester to replace the treatment liquid in the step (1);
(3) cooking of the treated bamboos: replacing the weak black liquor with a warm black liquor, wherein the weak black liquor enters an original weak black liquor tank, then replacing the warm black liquor with a hot black liquor, wherein the warm black liquor enters a warm black liquor tank, after the replacement is completed, adding white liquor for cooking, after the cooking is completed, replacing the hot black liquor with the weak black liquor, wherein the hot black liquor enters a hot black liquor tank, and the warm black liquor enters the warm black liquor tank, and when a temperature of a pulp decreases, using a pump to pump the pulp to a pulp storage tower; wherein the warm black liquor refers to black liquor with a temperature greater than 100° C. but less than 140° C. obtained by replacing a cooked pulp with the weak black liquor; the hot black liquor refers to black liquor with a temperature of 140-165° C. obtained during the replacement and cooking; and the white liquor refers to cooking chemicals obtained from pulp production and alkali recovery, mainly comprising sodium hydroxide and sodium sulfide, wherein a ratio of an effective alkali dosage of the white liquor to mass of the bamboo raw material is 10.5%-14%, a sulfidity of the white liquor by NaOH is 25%-30%, a temperature of the cooking is 155-160° C., time of the cooking is 90-120 minutes, and the temperature decrease refers to the temperature dropping below 100° C.;
(4) washing of the pulp: washing the pulp in the pulp storage tower of the step (3) to obtain a washed pulp and a washed weak black liquor, sending the washed pulp to a washed pulp tower, and sending the washed weak black liquor to the weak black liquor tank;
(5) screening and cleaning of the pulp: screening the washed pulp to obtain a screened pulp and screened rejects, sending the screened pulp to a screened pulp tower for storage, re-screening the screened rejects to obtain an accepted pulp and tail rejects, reusing the accepted pulp, and collecting the tail rejects for later use, followed by cleaning to obtain a screened and cleaned pulp; wherein the screening refers to selecting and using a pressure screen with a width of 0.2-0.3 mm for a screen slot, wherein a mass percent concentration of the screened pulp is controlled between 0.5%-1%; and adopting two-stage screening, wherein first-stage screened rejects are sent to second-stage screening for secondary screening, the accepted pulp from the second-stage screening enters a pulp feed pump inlet of first-stage screening, and the tail rejects are collected for later use;
(6) screening of parenchyma cells: removing parenchyma cells and fine fibers from the screened and cleaned pulp using a microporous screen, sending a pulp with parenchyma cells and fine fibers removed to a long fiber pulp tower for storage, and sending a pulp containing parenchyma cells and fine fibers to a parenchyma cell pulp tower for storage and later use; wherein the microporous screen refers to a screen with a diameter between 0.1 and 0.5 mm, a mass percent concentration of the screened pulp is 0.1%-0.5%, the pulp with parenchyma cells and fine fibers removed is sent to the long fiber pulp tower for storage, and the pulp containing parenchyma cells and fine fibers is sent to the parenchyma cell pulp tower for storage and later use;
(7) oxygen delignification of the pulp with parenchyma cells and fine fibers removed: first concentrating the pulp with parenchyma cells and fine fibers removed, followed by the oxygen delignification to obtain a pulp after the oxygen delignification;
(8) ECF bleaching of the pulp after the oxygen delignification: performing ECF bleaching treatment of a D 0 EpD 1 P process on the pulp after the oxygen delignification to obtain bleached pulp, and sending the bleached pulp to a pulp board machine to obtain a bamboo fluff pulp board;
(9) ultrafiltration of the treatment liquid: treating the replaced treatment liquid obtained in the step (2) by ultrafiltration, obtaining a retentate and a permeate liquid, wherein the retentate is for separating hemicellulose, and continuing to use the permeate liquid for the alkali treatment in the step (1) after the permeate liquid is supplemented with sodium hydroxide; and
(10) recycling of the tail rejects: using the tail rejects obtained in the step (5) to prepare a tail reject pulp, concentrating and dehydrating the pulp containing parenchyma cells and fine fibers in the step (6) for recycling to obtain a parenchyma cell pulp, and mixing the tail reject pulp with the parenchyma cell pulp to prepare packaging paper.

2. The method for preparing fluff pulp from bamboos according to claim 1 , wherein in the step (1), the bamboos are one or more of Neosinocalamus affinis, Bambusa intermedia, Dendrocalamus membranaceus , and Lingnania chungii.

3. The method for preparing fluff pulp from bamboos according to claim 1 , wherein in the step (7), the concentrating refers to increasing a mass percent concentration of the pulp with parenchyma cells and fine fibers removed in the pulp tower to 9%-11%, which is achieved by combining a decker machine and a vacuum pulp washer, a concentrated pulp is sent to a medium concentration pulp tower, and a collected concentrated liquid is sent to a white water tower; and in the step (7), the oxygen delignification refers to delignification of the concentrated pulp under oxygen and alkaline conditions, two-stage oxygen delignification is used, chemicals are added in a first stage, and a process of first-stage oxygen delignification is as follows: a mass percent concentration of the concentrated pulp is 9%-11%, a temperature is 80-100° C., time is 20-30 minutes, oxygen pressure is 0.6-0.8 MPa, a ratio of a dosage of sodium hydroxide to mass of an oven dry pulp is 2%-3%, and a ratio of a dosage of magnesium sulfate to mass of an oven dry pulp is 0.2%-0.4%; and a process of second-stage oxygen delignification is as follows: a mass percent concentration of the pulp is 9%-11%, a temperature is 80-100° C., time is 60-90 minutes, and oxygen pressure is 0.4-0.5 MPa.

4. The method for preparing fluff pulp from bamboos according to claim 1 , wherein in the step (8), for the ECF bleaching of D 0 EpD 1 P, D 0 refers to first-stage chlorine dioxide bleaching, Ep refers to hydrogen peroxide-enhanced alkaline extraction, D 1 refers to second-stage chlorine dioxide bleaching, P refers to hydrogen peroxide bleaching, and ECF refers to an elemental chlorine-free bleaching process; for the D 0 bleaching process: a ratio of a dosage of chlorine dioxide to mass of an oven dry pulp is 0.7%-0.8%, a bleaching temperature is 60-70° C., bleaching time is 60-90 minutes, and a system pH is 2-3; for the Ep alkaline extraction process: a ratio of a dosage of hydrogen peroxide to mass of an oven dry pulp is 0.2%-0.4%, a ratio of a dosage of sodiu

Assignees

• Univ South China Tech

Inventors

• Lei Yichao
• Wang Mengdi
• Li Hailong
• Hu Jian

Classifications

• D21C11/02

  of {acid, neutral or alkaline} sulfite lye · CPC title

• D21C11/0035

  Introduction of compounds, e.g. sodium sulfate, into the cycle in order to compensate for the losses of pulping agents · CPC title

• D21C11/0014

  Combination of various pulping processes with one or several recovery systems (cross-recovery) · CPC title

• D21C9/163 Primary

  with peroxides · CPC title

• D21C9/02

  Washing {; Displacing cooking or pulp-treating liquors contained in the pulp by fluids, e.g. wash water or other pulp-treating agents} · CPC title