Method for preparing biomechanical unbleached pulp from wheat straw and full utilization of by-products thereof

Patent metadata

Field	Value
Publication number	US-12454792-B2
Application number	US-202117561237-A
Country	US
Kind code	B2
Filing date	Dec 23, 2021
Priority date	Dec 31, 2020
Publication date	Oct 28, 2025
Grant date	Oct 28, 2025

Abstract

The disclosure belongs to the technical field of papermaking technology and waste comprehensive utilization, and specifically relates to a method for preparing biomechanical unbleached pulp from wheat straw and full utilization of by-products thereof. In the present disclosure, wheat straw is used as raw materials for pulping, and treated by hot water, then a trace of KOH is added, the temperature of the wheat straw after heat saturation and softening is adjusted, alkaline compound enzymes is added for biological treatment, and refining of wheat straw is performed at last. The mechanical pulp meets the production requirements for unbleached packaging paper and paper-based materials, meanwhile, the by-products are recycled to prepare a biomass compound fertilizer, turning solid waste into treasures, and realizing a high value full utilization of wheat straw. Thus a good practical application value and a broad application prospect are performed.

First claim

What is claimed is:

1. A method for preparing biomechanical unbleached pulp from wheat straw and full utilization of by-products thereof, wherein the method comprises the following steps:
(1) cutting a physically-screened and dust-removed wheat straw into small pieces of 1-8 cm as raw materials, putting them into a processor or a reactor, and performing a hot water treatment according to a liquid ratio of 1:4-1:8 for 15-90 min to obtain a mixture of hot water and a hot water treated wheat straw in the reactor or processor; meanwhile collecting rotten wheat straw which cannot be used for processing;
(2) adding KOH to the mixture of hot water and the hot water treated wheat straw in the reactor or processor, adjusting pH of the hot water to 10-14, and performing a hydrothermal saturation and softening treatment on the wheat straw to obtain a hydrothermally saturated and softened wheat straw; collecting waste lye;
(3) treating the hydrothermally saturated and softened wheat straw with an alkaline biological compound enzyme in a biological processor for 30-90 min in a liquid ratio of 1:3-1:8 (W/V) to obtain an enzyme treated wheat straw; collecting wastewater produced in an enzyme treatment stage;
(4) refining the enzyme treated wheat straw after treatment in step (3) with a pulp refiner to obtain a refined wheat straw; and
(5) washing the refined wheat straw to obtain a biomechanical pulp; disintegrating and mixing the biomechanical pulp homogeneously with a fiber disintegrator to obtain an unbleached pulp, collecting refining washing water;
treating the waste lye, the wastewater produced in the enzyme treatment stage, and the refining washing water with a multi-effect evaporator to prepare residue by evaporation and concentration, and recycling heat energy for use in the hot water treatment stage of step (1); mixing the residue and the rotten wheat straw which cannot be used for processing in step (1) and adjusting pH thereof to prepare fertilizer.

2. The method according to claim 1 , wherein the hot water treatment in step (1) is 80-120° C.

3. The method according to claim 1 , wherein the hydrothermally saturation and softening treatment in step (2) comprises: keeping a temperature of the hot water at 80-120° C. for 20-60 min.

4. The method according to claim 1 , wherein a pH of the wheat straw at the end of step (2) is 7-10.

5. The method according to claim 1 , wherein a temperature in step (3) is 40-60° C.

6. The method according to claim 1 , wherein the alkaline biological compound enzyme used in step (3) is a compound enzyme of an alkaline xylanase, an alkaline cellulase, and an alkaline pectinase with an enzyme dosage of 10-80 IU/mL, and an enzyme activity ratio of the alkaline xylanase, the alkaline cellulase, and the alkaline pectinase is 0-6:0-3:0-1.5, wherein each enzyme activity is not 0.

7. The method according to claim 6 , wherein the enzyme activity ratio of the alkaline xylanase, the alkaline cellulase, and the alkaline pectinase is 1-4:1-2:1-1.5.

8. The method according to claim 1 , wherein in step (5), a mass ratio of the waste lye, the wastewater produced in the enzyme treatment stage, and the refining washing water is 3-5:15-20:15-20;
a mass ratio of the residue to the rotten wheat straw which cannot be used for processing in step (1) is 5-8:1-2;
adjusting pH to prepare fertilizer is as follows: adding phosphoric acid to adjust the pH to 7, drying, pulverizing and granulating to obtain the fertilizer.

9. The method according to claim 1 , wherein the alkaline biological compound enzyme used in step (3) is a compound enzyme of an alkaline xylanase, an alkaline cellulase, and an alkaline pectinase with an enzyme dosage of 10-80 IU/mL, and an enzyme activity ratio of the alkaline xylanase, the alkaline cellulase, and the alkaline pectinase is 1-4:1-2:1-1.5.

10. The method according to claim 1 , wherein the hydrothermally saturation and softening treatment in step (2) comprises: keeping a temperature of the hot water at 80-120° C. for 20-60 min.

Assignees

• Univ Qilu Technology

Inventors

• Ji Xingxiang
• Wang Ruiming
• Tian Zhongjian
• Chen Jiachuan
• Yang Guihua
• Lv Gaojin

Classifications

• D21H11/12

  Pulp from non-woody plants or crops, e.g. cotton, flax, straw, bagasse · CPC title

• D21D1/20

  Methods of refining · CPC title

• D21C11/10

  Concentrating spent liquor by evaporation (evaporators B01D) · CPC title

• D21C11/0007

  Recovery of by-products, i.e. compounds other than those necessary for pulping, for multiple uses or not otherwise provided for (volatile compounds obtained by decomposition of spent liquors in order to regenerate them D21C11/125; compounds obtained by fractionating the liquors in order to regenerate them D21C11/0042) · 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