CN112342814B

CN112342814B - Method for producing high-strength natural-color paper pulp by taking eucalyptus bark as raw material

Info

Publication number: CN112342814B
Application number: CN202011306344.7A
Authority: CN
Inventors: 林伟民; 陈宏富; 玉秀学; 李建斌
Original assignee: Hengxian Dongtang Sugar Industry Co ltd Paper Industry Branch
Current assignee: Hengxian Dongtang Sugar Industry Co ltd Paper Industry Branch
Priority date: 2020-11-19
Filing date: 2020-11-19
Publication date: 2023-03-31
Anticipated expiration: 2040-11-19
Also published as: CN112342814A

Abstract

A method for producing high-strength natural color paper pulp by taking eucalyptus bark as a raw material comprises the following production steps: (1) Mixing eucalyptus bark and mulberry stem according to the weight ratio of (75-85) to (15-25), and screening to remove stones, impurities and scraps; (2) washing to remove silt and dust; (3) preheating tail gas, and removing non-fiber carbohydrate; (4) Steaming with a continuous cooker under steam pressure of 0.6-0.8mpa for 0.5 hr, and adding alkali 4-6 wt% of the additive material; (5) pulping by using a high-consistency pulping machine with pressure to reach the beating degree of 15-17; (6) washing, extracting and recovering black liquor, and sending the black liquor to an alkali recovery system; (7) grinding the obtained paper pulp to 25-30 beating degrees through low-concentration grinding; (8) And (3) passing the slurry through a two-stage screening system, removing slag and impurities, and finally extruding by using a high-concentration screen filter press to obtain a wet slurry product, wherein the dryness of the wet slurry is 42-45%. The method has high yield of the natural color paper pulp and good fiber strength.

Description

Method for producing high-strength natural-color paper pulp by taking eucalyptus bark as raw material

Technical Field

The invention relates to the technical field of pulping and papermaking, in particular to a method for producing high-strength natural color paper pulp by taking eucalyptus bark as a raw material.

Background

The paper making is one of four inventions in China, and along with the rapid development of the paper making industry in China, particularly after natural forest protection engineering is implemented in China, the contradiction between supply and demand of paper making raw materials is increasingly prominent. Guangxi is the main production area of sucrose in China, and in order to comprehensively utilize bagasse resources and improve the economic benefits of enterprises, from 2001, sugar manufacturing enterprises in Guangxi are developing ways of combining sugar paper according to structural adjustment scheme of Guangxi paper making industry, and in 2015, 12 bagasse paper manufacturing enterprises are commonly utilized in the whole area, the capacity is about 110 ten thousand tons per year, and the bagasse demand for pulping reaches 440 ten thousand tons per year. And about 4500 ten thousand tons of sugarcane are produced in the whole area in 2015, about 200 thousand tons of bagasse which can be used for pulping and papermaking are produced, the problem of insufficient bagasse raw materials is obvious, statistics shows that the raw material gap of each bagasse pulp enterprise in the 2016 year is up to more than 55%, the cost of each enterprise real estate operation is high, and the enterprise continuously falls into the situation of loss. Therefore, wood pulp and waste paper are used as two main raw materials in the paper making industry of China, and the import dependence of the wood pulp and the waste paper is high. However, under the prohibition of solid waste import, external waste or zero import supervision is faced, and the limitation on the quantity and quality of the external waste import reaches the unprecedented level of history, which directly influences the development of the paper making industry in China.

There have been proposals by experts to broaden the imported papermaking wood, but broadening the imported wood also faces three major problems: firstly, the great countries of the wood successively go out of laws and regulations to limit the wood cutting, so that the wood price is continuously increased; second, the international oil price rises sharply, which causes the shipping cost to rise sharply; thirdly, the requirements of inspection and quarantine on wood chip fumigation are met, and the supply cost is also increased. Therefore, how to fully utilize the leftover materials separated from wood processing, enlarge the channel of paper making raw materials, improve the pulp yield on the basis of the original raw materials and reduce the material consumption has been increasingly concerned by pulping enterprises. The pulping enterprise using the fast-growing eucalyptus wood (or leftover) as the paper making raw material is a great complement. However, the novel forest waste generated by planting a large amount of fast-growing eucalyptus trees cannot be effectively utilized, a large amount of eucalyptus bark is generated by a large number of enterprises using eucalyptus trees, a boiler has to be modified for consuming the eucalyptus bark and reducing the environmental pressure, and the eucalyptus bark which is low in heat value and difficult to dry is combusted.

According to the research, the eucalyptus bark has a distinct characteristic compared with other barks: (1) the concentration degree is high, and the utilization is easy; (2) The bark structure is loose, and the method of simple alkali treatment and the like is adopted, so that the bark is easy to defiber and grind; (3) The bark is wood waste, so the cost is low and the source is wide; (4) The eucalyptus bark replaces woody materials, and fibers of a considerable part of bark can be utilized, so that the eucalyptus bark has good development prospect, and how to reasonably utilize the eucalyptus bark for pulping and papermaking can fill the blank of insufficient bagasse raw materials of pulping and papermaking enterprises, improve the income of wood processing enterprises, reduce the cutting amount of forests to the maximum extent and achieve the win-win economic and social benefits. Thus, paper making by using eucalyptus bark pulp has been developed, and some techniques for paper making by using eucalyptus bark pulp have been reported in the open literature, such as:

1. chinese patent: a method for pulping and papermaking by using eucalyptus bark, which is applied in the following application number: 201010540158.X, application date: 2010.11.11, patentee: beam edge, address: 510650 guangdong province, guangzhou city, tianhehaixin street No. 18 402, inventor: beam front, abstract: a method for pulping and papermaking by using eucalyptus bark comprises crushing eucalyptus bark, alkali treating, and pulping to obtain corrugated paper; the eucalyptus bark is crushed, the colored substances in the bark are extracted, and then the crushed eucalyptus bark is directly used for producing high-grade corrugated paper through alkali treatment, pulp grinding and the like; the eucalyptus bark is ground into the mill base after extracting the colored substances through the processes of cooking, decoloring, bleaching and the like, and is used for producing white paper. Forest waste is utilized to turn waste into valuable, a new process is created, and new resources are developed; the process of the invention is practical and feasible, and can be carried out by common paper mills and fiber manufacturers; forest wastes polluting the environment are used, so that the environmental pollution is reduced; forest workers and farmers increase income by selling barks; the invention produces high-quality pulp with low cost, and can ensure that production enterprises realize social benefit and economic benefit.

2. Chinese patent: a method of producing papermaking pulp from eucalyptus bark and pulp, application No.: 201811036112.7, application date: 2018.09.06, applicant: beam vessel, address: 529300 lane No. 7 of Shanghai, jiangmen, guangdong province, maokang town, longgang juqing village, inventor: beam vessel, abstract: the invention discloses a method for producing papermaking pulp by using eucalyptus bark, which comprises the following steps: 1) Pulverizing eucalyptus bark, and soaking in alkaline solution for 30-48 hr; 2) Mixing the eucalyptus bark soaked in the alkali liquor in the step 1) with water, and then grinding and squeezing to obtain the papermaking paper pulp. The pulping method has the advantages of simple process, low cost, environmental protection and no pollution, and the produced paper pulp is particularly suitable for producing paper products such as corrugated paper, high-grade corrugated paper, white paper and the like and has good economic benefit.

However, the inventor researches and discovers that the method reported in the literature has many defects, namely 1, the method is limited by process conditions, the fiber recovery rate is low, and the yield is not high; 2. poor quality and low pulp strength; 3. unbleached pulp has a high content of non-fiber carbohydrates and is black in color, and even when used for manufacturing wrapping paper, the unbleached pulp belongs to a low-grade category.

Disclosure of Invention

The invention aims to provide a method for producing high-strength natural-color paper pulp by taking eucalyptus bark as a raw material, the method reasonably utilizes the eucalyptus bark as a waste material to prepare pulp, reduces the pressure of the eucalyptus bark on the environment, adopts an improved process to prepare semi-chemical pulp, has no discharged wastewater, and is high in pulping yield, high in paper pulp strength, high in quality and easy to realize industrial production.

The technical scheme adopted by the invention for solving the technical problems is as follows:

a method for producing high-strength natural-color paper pulp by taking eucalyptus bark as a raw material comprises the following production steps:

(1) Mixing eucalyptus barks and mulberry stem sections, and screening out chippings and stones by adopting a combined vibrating sheet sieve, wherein large eucalyptus barks need to be cut into small pieces meeting the requirement of cooking; the mulberry stem section is a small section which is cut into the length of less than 5 cm by using mulberry stems, and does not need twigs and branches; the weight ratio of the eucalyptus bark to the mulberry stem is (75-85) to (15-25).

(2) And (4) washing the raw materials obtained in the previous step by using washing equipment to remove silt and dust. The washing equipment adopts a drum type washing machine.

(3) The washed raw materials enter a pre-steaming bin, the pre-steaming bin is a container which can be filled with steam to preheat the raw materials, and tail steam at the outlet of the high-concentration pulping machine with pressure is filled into the pre-steaming bin to preheat the raw materials. The tail gas at the outlet of the high-concentration pulping machine with pressure is used for preheating the raw material, so that the cooking efficiency can be improved, and the tail gas has higher temperature (110-130 ℃) and can easily separate out non-fiber carbohydrates in the raw material after being contacted with the raw material, so that substances influencing paper pulp fibers, such as lignin, tannin, grease, resin and substances which are easy to oxidize, in the raw material can be removed. And the paper pulp obtained after treatment is not easy to brown and not black, and can be produced to be used as high-grade packing paper.

(4) The preheated raw materials are extruded and dehydrated by a feeder and then are cooked by a continuous cooker under the steam pressure of 0.6-0.8MPa for 0.5 hour, and alkali with the absolute dry weight of 4-6% of additive materials is needed in the continuous cooker before the cooking is started.

(5) And (3) blowing the pulp obtained by steaming and boiling into a high-concentration pulp grinder with pressure, and grinding the pulp to the SR beating degree of 15-17 ℃.

(6) After the pulp is ground, the pulp is put into a submergence pool for submergence, and then the pulp is sent to a pulp washer for pulp washing, extraction and recovery of black liquor and sent to an alkali recovery system. The alkali recovery system can directly enter the alkali recovery system for bagasse papermaking.

(7) The obtained paper pulp is further ground to 25-30 DEG SR beating degree through a low-concentration mill and then discharged to a pulp discharge pool for storage.

(8) And (3) passing the slurry obtained in the previous step through a two-stage screening system, removing slag and impurities, and finally extruding by using a high-concentration screen filter press to obtain a wet slurry product, wherein the dryness of the wet slurry is 42-45%.

The alkali is sodium hydroxide, or a compound alkali can be adopted.

The above process may also be adapted to a batch cooking pulping process, with appropriate modifications.

The combined vibrating plate sieve, the rotary drum washing machine, the pressurized high-concentration pulp grinder, the feeder, the continuous digester, the pulp washer, the low-concentration mill and the high-concentration net-clamping filter press can be installed and used by adopting the existing general pulping equipment.

The beneficial effects of the invention are:

1. the method needs strict production steps and strict control parameters, the yield of the produced semi-chemical pulp is more than 75 percent, the dryness of the wet pulp is 42 to 45 percent, the quality reaches the quality standard of the national waste B grade of common natural color waste paper pulp and more, and the industrial production can be realized.

2. The raw materials are added with a proper amount of mulberry stems, which is beneficial to fully utilizing agricultural wastes, as is well known, silkworm breeding is a good way for farmers to become rich in a wide area in the south of the Yangtze river in China, mulberry leaves are used for silkworm breeding every year, so that the farmers are brought good income, but the mulberry trees need to be subjected to summer cutting and autumn cutting twice every year to generate a large amount of mulberry stems, a small number of mulberry stems are used for culturing edible fungi or other firewood, the mulberry stems have little use and can not be stacked in the field to cause pollution, but contain a large amount of vitamins, the mulberry stems are added into eucalyptus barks, have long fibers and contain viscous glue, and are steamed and then ground into pulp together with the eucalyptus barks, so that the fibers of the eucalyptus barks can be protected, the pulp grinding yield can be improved, and the fibers can be enhanced.

3. The method adopts two-stage pulping of the raw materials, namely the processes of first cooking, then coarse grinding and finally fine grinding, the first cooking can lead the tissue structure of the raw materials to be loose, the fiber loss is less during the coarse grinding, the fiber strength can be improved during the final fine grinding, the fluffiness is high, the brooming is good, the cellulose and the hemicellulose can be kept to different degrees as far as possible, an important measure of the pulping yield can be ensured, the fibers can absorb water and swell during the pulping, the elasticity and the plasticity are higher, the production requirement of a paper machine can be met, and the produced paper can reach the expected quality index.

4. Before the raw materials are cooked, the tail steam with the pressure at the outlet of the high-concentration pulping machine is used for preheating the raw materials, so that the cooking efficiency can be improved, the energy consumption can be reduced, the temperature of the tail steam is higher, non-fiber carbohydrates in the raw materials can be separated out after the tail steam is contacted with the raw materials, the paper pulp obtained after treatment is not prone to brown stain, and the quality of the prepared unbleached paper is good. Energy sources (saturated steam) can be recovered; 1/4-1/3 of water vapor can be saved for pulping enterprises every year, and the economic benefit of factories is improved.

Drawings

FIG. 1 is a stacking view of eucalyptus bark;

FIG. 2 is a diagram of a finished semi-chemical pulp;

as seen in the figure, the prepared paper pulp is uniform, soft in fiber and good in color and luster, and is suitable for being used as high-grade packaging paper.

Detailed Description

In order to more clearly show the application and technical route of the patent, the invention is explained in detail with reference to the following examples.

Example 1

The method comprises the following steps of:

(1) Mixing eucalyptus barks and mulberry stem sections, and screening out chippings and stones by adopting a combined vibrating sheet sieve, wherein large eucalyptus barks need to be cut into small pieces meeting the requirement of cooking; the mulberry stem section is a small section which is cut into the length less than 5 cm by using mulberry stems; the weight ratio of the eucalyptus bark to the mulberry stem is (75-85) to (15-25);

(2) Washing the raw materials obtained in the previous step by using washing equipment to remove silt and dust;

(3) The washed raw material enters a pre-steaming bin, tail gas (at the temperature of 110-130 ℃) with a pressure high-concentration pulping machine outlet is introduced into the pre-steaming bin to preheat the raw material, so that non-fiber carbohydrates in the raw material can be easily separated out, and substances influencing paper pulp fibers, such as lignin, tannin, grease, resin and substances easy to oxidize, in the raw material are removed.

(4) Extruding and dehydrating the preheated raw materials by using a feeder, and then cooking the raw materials by using a continuous digester, wherein the raw materials are cooked for 0.5 hour under the steam pressure of 0.6-0.8MPa, and sodium hydroxide accounting for 4-6 percent of the total weight of the raw materials is required to be added into the continuous digester before the raw materials are cooked;

(5) The pulp obtained by steaming is fed into a high-concentration pulping machine with pressure by blowing, and the pulp is grinded to 15-17 DEG SR beating degree;

(6) After the pulp is ground, the pulp is put into a submergence eliminating pool for submergence, and then the pulp is sent to a pulp washer for pulp washing, extraction and recovery of black liquor and sent to an alkali recovery system;

(7) Further grinding the obtained paper pulp through a low-concentration mill to 25-30 DEG SR beating degree, and then discharging the paper pulp to a pulp discharging pool for storage;

The eucalyptus bark pulping application test is reported in the following table (without the addition of mulberry stalk segments, using a mill-first and then cook process).

The paper sheet physical property detection results of the ground pulp obtained by sheet making with a standard paper sheet former are shown in the following table (the serial number corresponds to the pulp, and the PFI beating revolution is 1500).

About 70 percent of the paper sheet quality reaches the quality standard of C grade waste of common natural color waste paper pulp.

The following table (with mulberry stalk segments added) was recorded using the process of the present application.

About 90 percent of the paper quality reaches the quality standard of the national waste B grade of common natural color waste paper pulp.

The above embodiments are only preferred embodiments of the present invention, and not intended to limit the scope of the present invention, and all equivalent structures or equivalent processes that are exchanged by the present specification, or directly or indirectly applied to other related technical fields are also included in the scope of the present invention.

Claims

1. A method for producing high-strength natural color paper pulp by taking eucalyptus bark as a raw material is characterized by comprising the following steps: the production steps are as follows:

(1) Mixing eucalyptus barks and mulberry stem sections, and screening out stones, impurities and scraps by adopting a combined vibrating sheet sieve, wherein large eucalyptus barks need to be cut into small pieces meeting the requirement of cooking; the mulberry stem section is a small section which is cut into the length less than 5 cm by using mulberry stems, and tender branches and leaves are not used; the weight ratio of the eucalyptus bark to the mulberry stem is (75-85) to (15-25); the mulberry stems are added into the eucalyptus bark, the fibers of the mulberry stems are long and contain viscous glue, and the mulberry stems and the eucalyptus bark are cooked together and then ground into pulp, so that the fibers of the eucalyptus bark can be protected, the pulp grinding yield can be improved, and the fibers can be enhanced;

(3) The washed raw materials enter a pre-steaming bin, tail steam with the temperature of 110-130 ℃ at the outlet of a high-concentration pulping machine with pressure is introduced into the pre-steaming bin to preheat the raw materials so as to remove non-fiber carbohydrates in the raw materials, the tail steam at the outlet of the high-concentration pulping machine with pressure is used for preheating the raw materials, the steaming efficiency can be improved, the temperature of the tail steam is higher, the tail steam can be contacted with the raw materials to easily separate out the non-fiber carbohydrates in the raw materials, and the treated paper pulp is not easy to brown and has no black color;

(4) Extruding and dehydrating the preheated raw materials by using a feeder, and then cooking by using a continuous cooker, wherein the raw materials are cooked for 0.5 hour under the steam pressure of 0.6-0.8MPa, and alkali accounting for 4-6 percent of the total weight of the raw materials needs to be added into the continuous cooker before the raw materials are cooked, wherein the alkali is sodium hydroxide; the tissue structure of the raw materials can be loosened by cooking;

(5) The pulp obtained by steaming is fed into a pressurized high-concentration pulp grinder in a spraying manner, the pulp is ground to 15-17 DEG SR beating degree, and the fiber loss is less during high-concentration grinding;

(7) Further grinding the obtained paper pulp through a low-concentration mill to 25-30 DEG SR beating degree, and then discharging the paper pulp to a pulp discharging pool for storage; the low-concentration grinding can improve the fiber strength, has high fluffing degree and good brooming, can ensure the pulping yield, also ensures that the fiber absorbs water and swells during pulping, has higher elasticity and plasticity, and meets the production requirement of a paper machine so that the produced paper can reach the expected quality index;

(8) And (3) removing slag and impurities of the slurry obtained in the previous step through a two-stage screening system, and finally extruding the slurry by using a high-concentration screen filter press to obtain a wet slurry product, wherein the yield of the semi-chemical slurry is over 75 percent, and the dryness of the wet slurry is 42-45 percent.