阅读说明：本技术 一种竹材牛皮纸浆低温置换蒸煮方法 (Low-temperature replacement cooking method for bamboo kraft pulp ) 是由 高焱仁 杨笃明 蒋大春 黄林 黄明建 蒋河 于 2021-08-27 设计创作，主要内容包括：一种竹材牛皮纸浆低温置换蒸煮方法,包括切削竹片、筛选、再碎、洗涤、滤水、称重和计算、预浸装料、温液填充、热液填充、升温蒸煮、冷喷放、取料等步骤。筛选步骤使用的竹片筛选装置包括一对翻转单元、一对筛盘输送单元、一接收单元。筛盘输送单元设于两个翻转单元之间,接收单元设于两个筛盘输送单元之间。本发明操作简单,产品得率高,制得的牛皮纸浆未蒸解物含量低,卡伯值低,均匀性好,强度高,特性粘度高,耐破指数高,抗张指数高,撕裂指数高,mit耐折度高,蒸汽单耗低,碱单耗低,用该方法生产出的竹材牛皮纸浆质量高,可替代针叶木牛皮纸浆。竹片筛选装置能充分筛出小于筛盘预定孔径的竹末,提高工作效率。(A low-temperature displacement cooking method for bamboo kraft pulp comprises the steps of cutting bamboo chips, screening, crushing, washing, filtering water, weighing and calculating, presoaking and charging, warm liquid filling, hot liquid filling, heating and cooking, cold spraying, material taking and the like. The bamboo chip screening device used in the screening step comprises a pair of overturning units, a pair of screen disc conveying units and a receiving unit. The sieve tray conveying unit is arranged between the two overturning units, and the receiving unit is arranged between the two sieve tray conveying units. The method has the advantages of simple operation, high product yield, low content of non-hydrolysate of the prepared kraft pulp, low kappa number, good uniformity, high strength, high intrinsic viscosity, high bursting index, high tensile index, high tearing index, high mit folding resistance, low steam consumption and low alkali consumption, and the bamboo kraft pulp produced by the method has high quality and can replace softwood kraft pulp. Bamboo chips sieving mechanism can fully sieve out the bamboo powder that is less than the predetermined aperture of sieve tray, improves work efficiency.)

1. The low-temperature replacement cooking method of bamboo kraft pulp is characterized by comprising the following steps of:

s01: cutting bamboo chips: cutting the bamboo into bamboo chips;

s02: screening: conveying the bamboo chips obtained in the step S01 to a bamboo chip screening device through a conveying device, screening the bamboo chips with a preset aperture, taking out the bamboo chips with the aperture larger than the preset aperture to perform the step S03, and collecting bamboo powder with the aperture smaller than the preset aperture to perform the step S04;

s03: and (3) crushing again: conveying the bamboo chips exceeding the preset aperture in the step S02 to a re-crusher through a conveying device, cutting the bamboo chips by the re-crusher, and repeating the screening process in the step S02 on the cut bamboo chips;

s04: washing: washing the bamboo powder collected in the step S02 by a washing machine;

s05: water filtration: conveying the bamboo powder washed in the step S04 to a storage bin provided with a filter screen through a conveying device for storage and water filtration;

s06: weighing and calculating: measuring the water content of the bamboo powder filtered in the step S05, calculating the dry weight of the bamboo powder according to the water content, and taking 13-15% of the dry weight of the bamboo powder as the total alkali consumption;

s07: pre-dipping and loading: uniformly mixing cold white liquor with the temperature of 80-90 ℃ and cold black liquor with the temperature of 70-80 ℃ in a preset proportion to form first mixed liquor, wherein the alkali content of the white liquor accounts for 2-4% of the total alkali content, conveying the bamboo powder subjected to water filtration in the step S06 to a cooking pot opening through a conveying device, and flushing the bamboo powder into the cooking pot through the first mixed liquor for presoaking for 40-60 min;

s08: filling warm liquid: closing a pot cover of the cooking pot, uniformly mixing cold white liquor with the temperature of 80-90 ℃ and warm black liquor with the temperature of 110-120 ℃ in a preset proportion to form second mixed liquor, wherein the alkali content of the white liquor accounts for 35-40% of the total alkali content, and filling the second mixed liquor into the pot body;

s09: hot liquid filling: uniformly mixing 130-140 ℃ hot white liquor and 140-150 ℃ hot black liquor in a preset proportion to form third mixed liquor, wherein the alkali amount of the white liquor accounts for 56-63% of the total alkali amount, and filling the third mixed liquor into a pot body;

s10: heating and cooking: starting a circulating pipe steam heater, heating the temperature in the cooking pot to 140-150 ℃ within 50-70 min through the circulating pipe steam heater, and closing the circulating pipe steam heater;

s11: cold spraying: filling 60-80 ℃ pulp washing black liquor into a digester from two filling ports of the digester simultaneously, and cooling the temperature in the digester to 90-100 ℃;

s12: taking materials: and pumping the pulp in the cooking pot from the cooking pot into the blowing pot through a pulp discharging pump to obtain the pulp.

2. The low-temperature replacement cooking method for bamboo kraft pulp according to claim 1, wherein the washing time of the step S04 is 2-3 h.

3. The low-temperature displacement cooking method for bamboo kraft pulp according to claim 1, wherein the step S05 is to filter water in the bamboo dust out of a filter screen until the moisture of the bamboo dust is 48.5% -49.5%.

4. The low-temperature displacement cooking method for bamboo kraft pulp according to claim 1, wherein the weight of the first mixed solution added into the cooking pot in the step S07 is 1.0-1.7 times of the dry weight of the bamboo powder calculated in the step S06; and controlling the first mixed solution to uniformly flush the bamboo powder into the cooking pot through the dispersion control system.

5. The low-temperature displacement cooking method for bamboo kraft pulp according to claim 1, wherein the weight of the second mixed solution filled into the bottom of the cooking pot in the step S08 is 2.7-4.2 times of the dry weight of the bamboo powder calculated in the step S06; after the second mixed solution is filled, the black liquor generated in the cooking pot flows back from the top of the pot body, the temperature of the back-flowing black liquor is measured, the black liquor with the temperature not higher than 90 ℃ flows into the cold black liquor tank, and the black liquor with the temperature higher than 90 ℃ flows into the warm black liquor tank; filling the second mixed solution into the pot body from the bottom of the digester at a constant speed within 35-45 min through a dispersion control system; and starting a liquor circulating pump of the digester after filling, and performing pumping circulation for 15-25 min.

6. The low-temperature displacement cooking method for bamboo kraft pulp according to claim 5, wherein the weight of the third mixed solution filled into the bottom of the cooking pot in the step S09 is 2.7-4.2 times of the dry weight of the bamboo powder calculated in the step S06; after the third mixed solution is filled, the black liquor generated in the cooking pot flows back from the top of the pot body, the temperature of the back-flowing black liquor is measured, the black liquor with the temperature not higher than 135 ℃ flows into the temperature black liquor tank, and the black liquor with the temperature higher than 135 ℃ flows into the hot black liquor tank; filling the third mixed solution into the pot body from the bottom of the digester at a constant speed within 45-55 min through a dispersion control system; and starting a liquor circulating pump of the digester after filling, and performing pumping circulation for 15-25 min.

7. The low-temperature replacement cooking method for bamboo kraft pulp according to claim 1, wherein in the step S10, the temperature in the cooking pot is uniformly raised by 1 ℃ every 5-7 min by controlling a circulating pipe steam heater through a dispersion control system; and after the steam heater of the circulating pipe is closed, starting the liquor circulating pump of the digester, and performing pumping circulation for 20-40 min.

8. The low-temperature displacement cooking method for bamboo kraft pulp according to claim 6, wherein the pulp washing black liquor of step S11 is simultaneously fed into the cooking pot from two inlets of the cooking pot, the black liquor generated in the cooking pot is ejected out from the middle part of the pot body, the black liquor with a temperature not higher than 135 ℃ flows into the warm black liquor tank, and the black liquor with a temperature higher than 135 ℃ flows into the hot black liquor tank; and after the temperature in the digester is cooled to 90-100 ℃, starting a liquid medicine circulating pump of the digester, and performing pumping circulation for 5-10 min.

9. The low-temperature displacement cooking method for bamboo kraft pulp according to claim 8, wherein the cold black liquor, the warm black liquor and the hot black liquor recovered in steps S08, S09 and S11 are used for the next pot cooking.

Technical Field

The invention relates to bamboo pulp paper, in particular to a low-temperature replacement cooking method for bamboo kraft paper pulp.

Background

The kraft pulp is a plant fiber material obtained by chemically removing lignin and dissociating cellulose from a plant material, and the main components of the kraft pulp are cellulose and hemicellulose, and the kraft pulp is a degradable environment-friendly material.

With the continuous upgrade of national plastic restriction, the kraft pulp is used for replacing plastics to manufacture various production and living goods such as packaging paper, paper bags, paper boxes and the like, the demand is more and more large, the quality requirement on the kraft pulp is more and more high, and especially the kraft pulp with high mechanical strength becomes a popular material. At present, domestic high-mechanical-strength kraft pulp mainly depends on imported European and American softwood pulp, China has the most abundant bamboo resources in the world, and renewable bamboo resources are used as raw materials of the high-mechanical-strength kraft pulp to replace wood resources which are in short supply in China, so that felling of natural resources can be reduced, the protection of natural forests is facilitated, and the basic national conditions of China are met.

The replacement cooking technology is derived from wood pulp production, because the uniformity of a bamboo plant chemical structure is far lower than that of softwood, the content of bamboo lignin is lower than that of softwood, the content of bamboo hemicellulose is far higher than that of softwood and the like, the problems of low yield, high energy consumption, poor uniformity, high chemical medicine consumption, low mechanical strength and the like exist in the bamboo kraft pulp directly produced according to the wood pulp replacement cooking technology, the yield of the bamboo kraft pulp produced by the prior art is about 52%, the intrinsic viscosity is about 900-1000 mL/g, the steam unit consumption is about 0.7t/adt, the alkali unit consumption calculated by Na2O is about 320kg/adt, the quality of the softwood kraft pulp cannot be achieved, and the downstream use has limitation.

When the prior art sieves bamboo chips, because the conveying capacity of the bamboo chips is usually large, in the sieving equipment, bamboo powder which is positioned at the upper part and is smaller than the preset aperture of the sieve tray is sometimes blocked by bamboo materials positioned at the lower part and is not sieved to the subsequent processing procedure, and the bamboo powder and the bamboo chips which exceed the preset aperture are jointly sent into a re-crusher for re-crushing, so that the working efficiency is low.

Disclosure of Invention

Aiming at the problems, the invention provides the low-temperature displacement cooking method for the bamboo kraft pulp, which has the advantages of simple operation, high product yield, low content of non-digested matters in the prepared kraft pulp, low kappa number, good uniformity, high strength, high intrinsic viscosity, high bursting index, high tensile index, high tearing index, high mit folding resistance, low steam consumption and low alkali consumption. Bamboo chips sieving mechanism can fully sieve out the bamboo powder that is less than the predetermined aperture of sieve tray, improves work efficiency.

In order to realize the purpose of the invention, the following scheme is adopted:

a low-temperature replacement cooking method for bamboo kraft pulp comprises the following steps:

s01: cutting bamboo chips: cutting the bamboo into bamboo chips;

s02: screening: conveying the bamboo chips obtained in the step S01 to a bamboo chip screening device through a conveying device, screening the bamboo chips with a preset aperture, taking out the bamboo chips with the aperture larger than the preset aperture to perform the step S03, and collecting bamboo powder with the aperture smaller than the preset aperture to perform the step S04;

s03: and (3) crushing again: conveying the bamboo chips exceeding the preset aperture in the step S02 to a re-crusher through a conveying device, cutting the bamboo chips by the re-crusher, and repeating the screening process in the step S02 on the cut bamboo chips;

s04: washing: washing the bamboo powder collected in the step S02 by a washing machine;

s05: water filtration: conveying the bamboo powder washed in the step S04 to a storage bin provided with a filter screen through a conveying device for storage and water filtration;

s06: weighing and calculating: measuring the water content of the bamboo powder filtered in the step S05, calculating the dry weight of the bamboo powder according to the water content, and taking 13-15% of the dry weight of the bamboo powder as the total alkali consumption;

s07: pre-dipping and loading: uniformly mixing cold white liquor with the temperature of 80-90 ℃ and cold black liquor with the temperature of 70-80 ℃ in a preset proportion to form first mixed liquor, wherein the alkali content of the white liquor accounts for 2-4% of the total alkali content, conveying the bamboo powder subjected to water filtration in the step S06 to a cooking pot opening through a conveying device, and flushing the bamboo powder into the cooking pot through the first mixed liquor for presoaking for 40-60 min;

s08: filling warm liquid: closing a pot cover of the cooking pot, uniformly mixing cold white liquor with the temperature of 80-90 ℃ and warm black liquor with the temperature of 110-120 ℃ in a preset proportion to form second mixed liquor, wherein the alkali content of the white liquor accounts for 35-40% of the total alkali content, and filling the second mixed liquor into the pot body from a filling opening;

s09: hot liquid filling: uniformly mixing 130-140 ℃ hot white liquor and 140-150 ℃ hot black liquor in a preset proportion to form third mixed liquor, wherein the alkali amount of the white liquor accounts for 56-63% of the total alkali amount, and filling the third mixed liquor into a pot body from a filling opening;

s10: heating and cooking: starting a circulating pipe steam heater, heating the temperature in the cooking pot to 140-150 ℃ within 50-70 min through the circulating pipe steam heater, and closing the circulating pipe steam heater;

s11: cold spraying: filling 60-80 ℃ pulp washing black liquor into a digester from two filling ports of the digester simultaneously, and cooling the temperature in the digester to 90-100 ℃;

s12: taking materials: and pumping the pulp in the cooking pot from the cooking pot into the blowing pot through a pulp discharging pump to obtain the pulp.

Furthermore, the washing time of the step S04 is 2-3 h.

Further, in the step S05, water in the bamboo powder is filtered out from the filter screen until the moisture of the bamboo powder is 48.5% -49.5%.

Further, the weight of the first mixed solution added into the cooking pot in the step S07 is 1.0-1.7 times of the dry weight of the bamboo powder calculated in the step S06; and controlling the first mixed solution to uniformly flush the bamboo powder into the cooking pot through the dispersion control system.

Further, the weight of the second mixed liquid filled to the bottom of the cooking pot in the step S08 is 2.7-4.2 times of the dry weight of the bamboo powder calculated in the step S06; after the second mixed liquid is filled, the black liquid generated in the cooking pot flows back from the top outlet at the top of the pot body, the temperature of the back-flowing black liquid is measured, the black liquid with the temperature not higher than 90 ℃ flows into the cold black liquid tank, and the black liquid with the temperature higher than 90 ℃ flows into the warm black liquid tank; filling the second mixed solution into the pot body from the bottom of the digester at a constant speed within 35-45 min through a dispersion control system; and starting a liquor circulating pump of the digester after filling, and performing pumping circulation for 15-25 min.

Further, the weight of the third mixed liquid filled to the bottom of the cooking pot in the step S09 is 2.7-4.2 times of the dry weight of the bamboo powder calculated in the step S06; after the third mixed solution is filled, the black liquor generated in the cooking pot flows back from the top outlet at the top of the pot body, the temperature of the back-flowing black liquor is measured, the black liquor with the temperature not higher than 135 ℃ flows into the temperature black liquor tank, and the black liquor with the temperature higher than 135 ℃ flows into the hot black liquor tank; filling the third mixed solution into the pot body from the bottom of the digester at a constant speed within 45-55 min through a dispersion control system; and starting a liquor circulating pump of the digester after filling, and performing pumping circulation for 15-25 min.

Further, in the step S10, the steam heater of the circulating pipe is controlled by the distributed control system to uniformly heat the temperature in the cooking pot by 1 ℃ every 5-7 min; and after the steam heater of the circulating pipe is closed, starting the liquor circulating pump of the digester, and performing pumping circulation for 20-40 min.

Further, after the pulp washing black liquor in the step S11 is simultaneously filled into the digester from the two filling inlets of the digester, the black liquor generated in the digester is ejected out of the middle part of the digester, the black liquor with the temperature not higher than 135 ℃ flows into the warm black liquor tank, and the black liquor with the temperature higher than 135 ℃ flows into the hot black liquor tank; and after the temperature in the digester is cooled to 90-100 ℃, starting a liquid medicine circulating pump of the digester, and performing pumping circulation for 5-10 min.

Further, the cold black liquor, the warm black liquor and the hot black liquor recovered in the steps S08, S09 and S11 are used for the next pot for cooking.

The bamboo material special cooking pot comprises a cooking pot opening capable of temporarily storing materials, a pot cover capable of being opened and closed is arranged at the upper end of the pot opening, a filling opening enabling liquid to flow into the pot body in a one-way mode is formed in the bottom of the pot body, a top outlet enabling the liquid to flow out of the pot body in a one-way mode is formed in the upper end of the pot body, a pair of filling openings are formed in one end of the outer peripheral side of the pot body, and a middle top outlet is formed in one side of each filling opening.

Specifically, the total alkali amount is Na₂And (4) measuring O.

Specifically, steps S07, S08, S09 measure only the amount of white liquor alkali, not the amount of black liquor alkali.

Specifically, the dispersion control system is further connected to the blending equipment, the percentage of the alkali amount of the white liquid in each step to the total alkali amount is determined in steps S07, S08 and S09, and after the total liquid amount of the mixed liquid prepared in each step is determined, the white liquid and black liquid ratio in each step is set in the dispersion control system, and the white liquid amount and the black liquid amount of the blending equipment in the stage of preparing the mixed liquid in each step are automatically controlled to prepare the mixed liquid.

The beneficial effects of this technical scheme lie in:

1. the washed bamboo powder is stored in a bin with a filter screen and filtered, no additional operation is needed, the bamboo powder is kept stand for several hours, and the filtering operation is simple.

2. The bamboo materials fall into the cooking pot under the impact of the pre-soaking liquid, and the pre-soaking liquid and the bamboo materials can uniformly enter the cooking pot through the control of the dispersion control system, so that the bamboo materials are fully mixed; the bamboo chips are presoaked for 40-60 min, and starch and grease on the surfaces of the bamboo chips can be fully dissolved.

3. In the warm liquid filling step and the hot liquid filling step, liquid with the temperature higher than that in the cooking pot is slowly and uniformly filled into the cooking pot through the dispersion control system, and then pumping and circulating are carried out through the liquid medicine circulating pump, so that the effects of soaking alkali liquor and removing lignin are enhanced, the degradation of hemicellulose and cellulose is weakened, and meanwhile, the heat preservation effect is also achieved by carrying out short-time pumping and circulating through the liquid medicine circulating pump. The kraft pulp produced by the method of the invention has low content of non-digested matter and low kappa number. The technical scheme adopts a low-temperature low-alkali sulfate replacement cooking method, slowly raises the temperature for a long time, keeps the temperature for a short time, and can better keep the cellulose strength.

4. When the temperature is increased for cooking, the steam flow of the circulating pipe steam heater is controlled by the dispersion control system, the temperature in the cooking pot is uniformly increased by 1 ℃ every 5-7 min, and the influence of local temperature higher than cellulose degradation on uniformity and strength can be prevented.

5. In the warm liquid filling step, the backflow black liquid with the temperature similar to that of the first mixed liquid is ejected out of the cold black liquid tank and the warm black liquid tank; in the hot liquid filling step, the backflow black liquid with the temperature similar to that of the second mixed liquid is ejected out of the hot black liquid tank and the hot black liquid tank; in the cold spraying step, the backflow black liquor is ejected from the top outlet at the middle part to the warm black liquor tank and the hot black liquor tank, and the black liquor recovered from the cold black liquor tank, the warm black liquor tank and the hot black liquor tank can be used for cooking in the next pot, so that the material consumption is reduced, and the production cost is reduced.

6. The technical scheme can improve the product yield, the product intrinsic viscosity, the breakage resistance index, the tensile index, the tearing index, the mit folding endurance, the steam unit consumption and the alkali unit consumption.

7. The product produced by the technical scheme has high quality and can replace softwood kraft pulp.

Drawings

Fig. 1 shows a flow chart of the method of the present application.

Fig. 2 shows an overall perspective view of a four-bamboo-sheet screening device according to an embodiment of the present application.

Fig. 3 is a perspective view illustrating an overturning unit of a four-bamboo-chip screening apparatus according to an embodiment of the present application.

Fig. 4 is a perspective view illustrating another turning unit of the four-bamboo-chip screening apparatus according to the embodiment of the present application.

Fig. 5 shows a perspective view of a rotating frame, a single-axis linear cylinder, a sieve tray clamp and a baffle of the four-bamboo-chip screening device in the embodiment of the application.

Fig. 6 is a perspective view showing a screen tray conveying unit and a receiving unit of the four-bamboo-chip screening device according to the embodiment of the present application.

Detailed Description

The present application will be described in further detail below with reference to specific embodiments in order to enable those skilled in the art to better understand the present application. It is to be understood that the embodiments described are only a few embodiments of the present application and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

In one to four embodiments, the conveying device is a belt conveyor.

Example one

The low-temperature replacement cooking method of bamboo kraft pulp is implemented according to the following steps:

s01: cutting bamboo chips: cutting the bamboo into bamboo chips;

s02: screening: conveying the bamboo chips obtained in the step S01 to a bamboo chip screening device through a belt conveyor, screening the bamboo chips with a preset aperture, taking out the bamboo chips with the aperture larger than the preset aperture to perform the step S03, and collecting bamboo powder with the aperture smaller than the preset aperture to perform the step S04;

s03: and (3) crushing again: conveying the bamboo chips exceeding the preset aperture in the step S02 to a re-crusher through a belt conveyor, cutting the bamboo chips by the re-crusher, and repeating the screening process in the step S02 on the cut bamboo chips;

s04: washing: washing the bamboo powder collected in the step S02 for 2h by a washing machine;

s05: water filtration: conveying the bamboo powder washed in the step S04 to a storage bin provided with a filter screen through a belt conveyor for storage and filtering water until the water content is 49.5%;

s06: weighing and calculating: measuring the water content of the bamboo powder after water filtration in the step S05, calculating the dry weight of the bamboo powder according to the water content, and taking 15% of the dry weight of the bamboo powder as the total alkali consumption;

s07: pre-dipping and loading: setting a white liquid and black liquid proportion parameter in a dispersion control system according to the fact that the alkali amount of a white liquid accounts for 2% of the total alkali amount, setting a mixed liquid total weight parameter in the dispersion control system according to the fact that the weight of the white liquid is 1.0 time of the dry weight of the bamboo dust calculated in the S06 step, uniformly mixing cold white liquid at 80 ℃ and cold black liquid at 70 ℃ in a uniformly mixing device through the dispersion control system to form first mixed liquid, conveying the bamboo dust after water filtration in the S06 step to the opening of a cooking pot through a belt conveyor, controlling the first mixed liquid through the dispersion control system to uniformly flush the bamboo dust into the cooking pot, mixing the bamboo dust and the first mixed liquid in the cooking pot, and presoaking the mixed liquid for 40 min;

s08: filling warm liquid: closing a pot cover of the cooking pot, setting proportion parameters of white liquor and black liquor in a dispersion control system according to the fact that the alkali amount of the white liquor accounts for 35% of the total alkali amount, setting total weight parameters of mixed liquor in the dispersion control system according to the weight which is 2.7 times of the dry weight of the bamboo powder calculated in the step S06, uniformly mixing cold white liquor at the temperature of 80 ℃ and warm black liquor at the temperature of 110 ℃ in a uniformly mixing device into second mixed liquor through the dispersion control system, and filling the second mixed liquor into the pot body from the bottom of the cooking pot at a constant speed within 35min through the dispersion control system; after the second mixed liquid is fully filled, the black liquid generated in the cooking pot flows back from the top outlet at the top of the pot body, the temperature of the back-flowing black liquid is measured, the black liquid with the temperature not higher than 90 ℃ flows into the cold black liquid tank, the black liquid with the temperature higher than 90 ℃ flows into the warm black liquid tank, and the recovered cold black liquid and warm black liquid are used for cooking in the next pot; starting a liquor circulating pump of the digester after filling, and circulating for 15 min; the temperature in the pan was measured to be 100 ℃ after the pumping cycle was completed.

S09: hot liquid filling: setting proportion parameters of white liquid and black liquid in a dispersion control system according to that the alkali amount of the white liquid accounts for 63% of the total alkali amount, setting total weight parameters of mixed liquid in the dispersion control system according to that the weight is 2.7 times of the dry weight of the bamboo powder calculated in the step S06, uniformly mixing hot white liquid at 130 ℃ and hot black liquid at 140 ℃ in a mixing device into third mixed liquid through the dispersion control system, and filling the third mixed liquid into a pot body from the bottom of a digester at a constant speed within 45min through the dispersion control system; after the third mixed liquid is fully filled, the black liquor generated in the cooking pot flows back from the top outlet at the top of the pot body, the temperature of the back-flowing black liquor is measured, the black liquor with the temperature not higher than 135 ℃ flows into the temperature black liquor tank, the black liquor with the temperature higher than 135 ℃ flows into the hot black liquor tank, and the recovered warm black liquor and hot black liquor are used for cooking in the next pot; starting a liquor circulating pump of the digester after filling, and circulating for 15 min; the temperature in the pan was measured to be 130 ℃ after the end of the pumping cycle.

S10: heating and cooking: and starting a circulating pipe steam heater, controlling the circulating pipe steam heater to uniformly heat the temperature in the cooking pot to 1 ℃ every 5min through a dispersion control system, closing the circulating pipe steam heater when the temperature in the cooking pot is heated to 140 ℃, starting a liquor circulating pump of the cooking pot, and circulating for 20 min.

S11: cold spraying: filling 60 ℃ pulp washing black liquor into a digester from two filling inlets of the digester simultaneously, ejecting the black liquor generated in the digester from the middle part of the digester, allowing the black liquor with the temperature not higher than 135 ℃ to flow into a warm black liquor tank, allowing the black liquor with the temperature higher than 135 ℃ to flow into a hot black liquor tank, and allowing the recovered warm black liquor and hot black liquor to be used for the next digester; after the temperature in the digester is cooled to 90 ℃, a liquor circulating pump of the digester is started, and the liquor is pumped and circulated for 5 min.

S12: taking materials: and pumping the pulp in the cooking pot from the cooking pot into the blowing pot through a pulp discharging pump to obtain the pulp.

The content of the non-digested matter of the kraft pulp prepared in the example is 0.47%, and the Kappa number of the discharged pulp is 24.6 Kappa; the product yield is improved to 56 percent; the intrinsic viscosity is increased to 1208 mL/g; the quantitative determination of the sheet made is 135g/m²The mechanical strength index is tested according to GB24324-2009 under the condition of the beating degree of 38SR, and the burst index is 3.43KPa.m²G, tensile index 40.52N.m/g, tear index 14.36mN.m²(vii)/g, mit fold resistance 153 times; the steam consumption is reduced to 0.41t/adt, and the alkali consumption (calculated as Na 2O) is reduced to 250 kg/adt.

Example two

The low-temperature replacement cooking method of bamboo kraft pulp is implemented according to the following steps:

s01: cutting bamboo chips: cutting the bamboo into bamboo chips;

s02: screening: conveying the bamboo chips obtained in the step S01 to a bamboo chip screening device through a belt conveyor, screening the bamboo chips with a preset aperture, taking out the bamboo chips with the aperture larger than the preset aperture to perform the step S03, and collecting bamboo powder with the aperture smaller than the preset aperture to perform the step S04;

s03: and (3) crushing again: conveying the bamboo chips exceeding the preset aperture in the step S02 to a re-crusher through a belt conveyor, cutting the bamboo chips by the re-crusher, and repeating the screening process in the step S02 on the cut bamboo chips;

s04: washing: washing the bamboo powder collected in the step S02 for 2.5h by a washing machine;

s05: water filtration: conveying the bamboo powder washed in the step S04 to a storage bin with a filter screen through a belt conveyor for storage and filtering water until the water content is 48.5%;

s06: weighing and calculating: measuring the water content of the bamboo powder after water filtration in the step S05, calculating the dry weight of the bamboo powder according to the water content, and taking 14 percent of the dry weight of the bamboo powder as the total alkali consumption;

s07: pre-dipping and loading: setting a white liquid and black liquid proportion parameter in a dispersion control system according to the fact that the alkali amount of a white liquid accounts for 3% of the total alkali amount, setting a mixed liquid total weight parameter in the dispersion control system according to the fact that the weight of the mixed liquid is 1.3 times of the dry weight of the bamboo dust calculated in the S06 step, uniformly mixing cold white liquid at 85 ℃ and cold black liquid at 75 ℃ in a uniformly mixing device through the dispersion control system to form first mixed liquid, conveying the bamboo dust subjected to water filtration in the S06 step to the opening of a cooking pot through a belt conveyor, controlling the first mixed liquid through the dispersion control system to uniformly flush the bamboo dust into the cooking pot, mixing the bamboo dust and the first mixed liquid in the cooking pot, and presoaking the mixed liquid for 50 min;

s08: filling warm liquid: closing a pot cover of the cooking pot, setting proportion parameters of white liquor and black liquor in a dispersion control system according to the fact that the alkali amount of the white liquor accounts for 37% of the total alkali amount, setting total weight parameters of mixed liquor in the dispersion control system according to the weight which is 3.4 times of the dry weight of the bamboo powder calculated in the step S06, uniformly mixing cold white liquor at the temperature of 81 ℃ and warm black liquor at the temperature of 115 ℃ in a uniformly mixing device into second mixed liquor through the dispersion control system, and filling the second mixed liquor into the pot body from the bottom of the cooking pot at a constant speed within 40min through the dispersion control system; after the second mixed liquid is fully filled, the black liquid generated in the cooking pot flows back from the top outlet at the top of the pot body, the temperature of the back-flowing black liquid is measured, the black liquid with the temperature not higher than 90 ℃ flows into the cold black liquid tank, the black liquid with the temperature higher than 90 ℃ flows into the warm black liquid tank, and the recovered cold black liquid and warm black liquid are used for cooking in the next pot; starting a liquor circulating pump of the digester after filling, and performing pumping circulation for 20 min; the temperature in the pan was measured to be 105 ℃ after the end of the pumping cycle.

S09: hot liquid filling: setting proportion parameters of white liquor and black liquor in a dispersion control system according to the fact that the alkali amount of the white liquor accounts for 60% of the total alkali amount, setting total weight parameters of mixed liquor in the dispersion control system according to the fact that the weight of the mixed liquor is 3.4 times of the dry weight of the bamboo powder calculated in the step S06, uniformly mixing 135-DEG C hot white liquor and 145-DEG C hot black liquor in a mixing device into third mixed liquor through the dispersion control system, and filling the third mixed liquor into a pot body from the bottom of a digester at a constant speed within 50min through the dispersion control system; after the third mixed liquid is fully filled, the black liquor generated in the cooking pot flows back from the top outlet at the top of the pot body, the temperature of the back-flowing black liquor is measured, the black liquor with the temperature not higher than 135 ℃ flows into the temperature black liquor tank, the black liquor with the temperature higher than 135 ℃ flows into the hot black liquor tank, and the recovered warm black liquor and hot black liquor are used for cooking in the next pot; starting a liquor circulating pump of the digester after filling, and performing pumping circulation for 20 min; the temperature in the pan was measured to be 135 ℃ after the end of the pumping cycle.

S10: heating and cooking: and (3) starting a circulating pipe steam heater, controlling the circulating pipe steam heater to uniformly heat the temperature in the cooking pot to 1 ℃ every 6min through a distributed control system, closing the circulating pipe steam heater when the temperature in the cooking pot is heated to 145 ℃, starting a liquor circulating pump of the cooking pot, and circulating for 30 min.

S11: cold spraying: filling 70 ℃ pulp washing black liquor into a digester from two filling inlets of the digester simultaneously, ejecting the black liquor generated in the digester from the middle part of the digester, allowing the black liquor with the temperature not higher than 135 ℃ to flow into a warm black liquor tank, allowing the black liquor with the temperature higher than 135 ℃ to flow into a hot black liquor tank, and allowing the recovered warm black liquor and hot black liquor to be used for the next digester; after the temperature in the digester is cooled to 95 ℃, a liquid medicine circulating pump of the digester is started, and the liquid medicine is pumped and circulated for 7 min.

S12: taking materials: and pumping the pulp in the cooking pot from the cooking pot into the blowing pot through a pulp discharging pump to obtain the pulp.

The content of the non-digested matter of the kraft pulp prepared in the example was 0.42%, and the Kappa number of the discharged pulp was 26.8 Kappa; the product yield is improved to 56.5 percent; the intrinsic viscosity is improved to 1243 mL/g; the quantitative determination of the sheet made is 135g/m²The mechanical strength index is tested according to GB24324-2009 under the condition of the beating degree of 38SR, and the burst index is 3.68KPa.m²G, tensile index 42.56N.m/g, tear index 15.71mN.m²(vii)/g, mit flex endurance 176 times; the steam consumption is reduced to 0.44t/adt, and the alkali consumption (calculated as Na 2O) is reduced to 233 kg/adt.

EXAMPLE III

The low-temperature replacement cooking method of bamboo kraft pulp is implemented according to the following steps:

s01: cutting bamboo chips: cutting the bamboo into bamboo chips;

s02: screening: conveying the bamboo chips obtained in the step S01 to a bamboo chip screening device through a belt conveyor, screening the bamboo chips with a preset aperture, taking out the bamboo chips with the aperture larger than the preset aperture to perform the step S03, and collecting bamboo powder with the aperture smaller than the preset aperture to perform the step S04;

s03: and (3) crushing again: conveying the bamboo chips exceeding the preset aperture in the step S02 to a re-crusher through a belt conveyor, cutting the bamboo chips by the re-crusher, and repeating the screening process in the step S02 on the cut bamboo chips;

s04: washing: washing the bamboo powder collected in the step S02 for 3h by a washing machine;

s05: water filtration: conveying the bamboo powder washed in the step S04 to a storage bin with a filter screen through a belt conveyor for storage and filtering water until the water content is 48.9%;

s06: weighing and calculating: measuring the water content of the bamboo powder after water filtration in the step S05, calculating the dry weight of the bamboo powder according to the water content, and taking 13 percent of the dry weight of the bamboo powder as the total alkali consumption;

s07: pre-dipping and loading: setting a white liquid and black liquid proportion parameter in a dispersion control system according to the fact that the alkali amount of a white liquid accounts for 4% of the total alkali amount, setting a mixed liquid total weight parameter in the dispersion control system according to the fact that the weight of the white liquid is 1.7 times of the dry weight of the bamboo dust calculated in the S06 step, uniformly mixing cold white liquid at 90 ℃ and cold black liquid at 80 ℃ in a uniformly mixing device through the dispersion control system to form first mixed liquid, conveying the bamboo dust subjected to water filtration in the S06 step to the opening of a cooking pot through a belt conveyor, controlling the first mixed liquid through the dispersion control system to uniformly flush the bamboo dust into the cooking pot, mixing the bamboo dust and the first mixed liquid in the cooking pot, and presoaking the mixed liquid for 60 min;

s08: filling warm liquid: closing a pot cover of the cooking pot, setting proportion parameters of white liquor and black liquor in the dispersion control system according to the fact that the alkali amount of the white liquor accounts for 40% of the total alkali amount, setting total weight parameters of mixed liquor in the dispersion control system according to the weight which is 4.2 times of the dry weight of the bamboo powder calculated in the step S06, uniformly mixing cold white liquor at 90 ℃ and warm black liquor at 120 ℃ in the mixing equipment into second mixed liquor through the dispersion control system, and filling the second mixed liquor into the pot body from the bottom of the cooking pot at a constant speed within 45min through the dispersion control system; after the second mixed liquid is fully filled, the black liquid generated in the cooking pot flows back from the top outlet at the top of the pot body, the temperature of the back-flowing black liquid is measured, the black liquid with the temperature not higher than 90 ℃ flows into the cold black liquid tank, the black liquid with the temperature higher than 90 ℃ flows into the warm black liquid tank, and the recovered cold black liquid and warm black liquid are used for cooking in the next pot; starting a liquor circulating pump of the digester after filling, and performing pumping circulation for 25 min; the temperature in the pan was measured to be 110 ℃ after the pumping cycle was completed.

S09: hot liquid filling: setting proportion parameters of white liquor and black liquor in a dispersion control system according to the fact that the alkali amount of the white liquor accounts for 56% of the total alkali amount, setting total weight parameters of mixed liquor in the dispersion control system according to the fact that the weight of the mixed liquor is 4.2 times of the dry weight of the bamboo powder calculated in the step S06, uniformly mixing hot white liquor at 140 ℃ and hot black liquor at 150 ℃ in a mixing device into third mixed liquor through the dispersion control system, and filling the third mixed liquor into a pot body from the bottom of a digester at a constant speed within 55min through the dispersion control system; after the third mixed liquid is fully filled, the black liquor generated in the cooking pot flows back from the top outlet at the top of the pot body, the temperature of the back-flowing black liquor is measured, the black liquor with the temperature not higher than 135 ℃ flows into the temperature black liquor tank, the black liquor with the temperature higher than 135 ℃ flows into the hot black liquor tank, and the recovered warm black liquor and hot black liquor are used for cooking in the next pot; starting a liquor circulating pump of the digester after filling, and performing pumping circulation for 25 min; the temperature in the pan was measured to be 140 ℃ after the pumping cycle was completed.

S10: heating and cooking: and (3) starting a circulating pipe steam heater, controlling the circulating pipe steam heater to uniformly heat the temperature in the digester to 1 ℃ every 7min through a distributed control system, closing the circulating pipe steam heater when the temperature in the digester is heated to 150 ℃, starting a liquor circulating pump of the digester, and circulating for 40 min.

S11: cold spraying: filling 80 ℃ pulp washing black liquor into a digester from two filling inlets of the digester simultaneously, ejecting the black liquor generated in the digester from the middle part of the digester, allowing the black liquor with the temperature not higher than 135 ℃ to flow into a warm black liquor tank, allowing the black liquor with the temperature higher than 135 ℃ to flow into a hot black liquor tank, and allowing the recovered warm black liquor and hot black liquor to be used for the next digester; after the temperature in the digester is cooled to 100 ℃, a liquor circulating pump of the digester is started, and the liquor is pumped and circulated for 10 min.

S12: taking materials: and pumping the pulp in the cooking pot from the cooking pot into the blowing pot through a pulp discharging pump to obtain the pulp.

The kraft pulp produced in this example had an undistilled content of 0.38% and a discharge Kappa number of 29.1 Kappa; the product yield is improved to 57 percent; the intrinsic viscosity is increased to 1298 mL/g; the quantitative determination of the sheet made is 135g/m²The mechanical strength index is tested according to GB24324-2009 under the condition of beating degree of 38SR, and the burst index is 3.86KPa.m²G, tensile index 45.71N.m/g, tear index 16.21mN.m²(iv)/g, mit fold resistance 203 times; the steam consumption is reduced to 0.47t/adt, and the alkali consumption (calculated as Na 2O) is reduced to 217 kg/adt.

Example four

As shown in fig. 2 to 6, the bamboo chip screening apparatus used in the first, second and third embodiments includes a pair of turning units 1, a pair of screen tray conveying units 2 and a receiving unit 3.

The overturning unit 1 comprises a base 11, a rotating motor 12 is arranged on the upper end face of the base 11, a gear 121 is arranged at one end of an output shaft of the rotating motor 12, the gear 121 is meshed with a gear ring 13, a pair of connecting rods are arranged on the inner peripheral side of the gear ring 13, a rotating frame 14 is fixed at one end of each connecting rod, an extension rod 141 is arranged at one end of each rotating frame 14, a single-shaft linear cylinder 15 is respectively arranged on each of the upper end face and the lower end face of each rotating frame 14, a sieve tray clamp 16 is arranged on the output shaft of each single-shaft linear cylinder 15, each sieve tray clamp 16 is a semicircular arc, a sieve tray groove 161 is formed in the inner wall of each semicircular arc, a baffle 17 matched with each sieve tray clamp 16 in shape is extended at one end of each sieve tray clamp 16, a rotating seat 111 is further arranged on the upper end face of the base 11, the extension rod 141 penetrates through the rotating seat 111, and a balancing weight 18 made of tungsten alloy is arranged at one end of the extension rod 141;

the screen disc conveying unit 2 is arranged between the two overturning units 1 and comprises a support 21, a rodless cylinder 22 is arranged at the upper end of the support 21, a sliding block of the rodless cylinder 22 is positioned at the upper end of the support, an L-shaped frame 23 is arranged on the upper end face of the sliding block of the rodless cylinder 22, the heights of the two L-shaped frames 23 are respectively matched with the heights of the two grooves 161, and the L-shaped frame 23 is used for placing the screen disc 4 on the upper end face of the L-shaped frame 23;

the receiving unit 3 is arranged between the two sieve tray conveying units 2 and comprises a bamboo powder frame 31, the upper end of the bamboo powder frame 31 is provided with an opening 32 with the diameter increasing upwards, and the lower end of the bamboo powder frame 31 is provided with a plurality of universal wheels 33.

The working mode of the bamboo chip screening device is as follows:

the bamboo powder frame is moved between the two sieve tray conveying units and is ready to be received.

Placing two sieve trays 4 on one end of the upper end faces of two L-shaped frames 23 respectively, starting a rodless cylinder 22 located below, moving the sieve trays 4 between two sieve tray clamps 16 located below, starting two single-shaft linear cylinders 15 located below, clamping the sieve trays 4 between two sieve tray grooves 161, and simultaneously starting the rodless cylinder 22 located below to withdraw the L-shaped frames 23. At this time, the two sieve tray clamps 16 positioned below are tightly attached, and the two baffle plates 17 positioned below are combined into a cylinder shape.

Two single-shaft linear air cylinders 15 positioned at the upper part are started, two sieve tray clamps 16 positioned at the upper part are attached tightly, and two baffle plates 17 at the upper part are also combined into a cylindrical shape and are matched with two baffle plates 17 at the lower part in position.

Adding bamboo chips into the combined cylinder through a belt conveyor, starting two single-shaft linear air cylinders 15 located above after adding, separating two sieve tray clamps 16 located above, starting a rodless air cylinder 22 located above, moving a sieve tray 4 between the two sieve tray clamps 16 located above, starting the two single-shaft linear air cylinders 15 located above, clamping the sieve tray 4 between two sieve tray grooves 161, simultaneously starting the rodless air cylinders 22 located above, and withdrawing the L-shaped frame 23 thereof.

In the space formed by the upper and lower sieve trays 4 and the four retaining pieces 17, a part of the bamboo dust with the diameter smaller than that of the sieve trays 4 falls to the bamboo dust frame 31 from the sieve tray 4 below.

Start two rotating electrical machines 12, drive gear ring 13 by gear 121 and rotate, gear ring 13 drives revolving frame 14 and rotates, the unipolar straight line cylinder 15 and the unipolar straight line cylinder 15 of below of every upset unit 1 top exchange the position, two sieve tray clamps 16 of every upset unit 1 also exchange the position, two separation blades 17 of every upset unit 1 also exchange the position, the bamboo chip rocks at this in-process, more bamboo chips that are less than 4 apertures of sieve tray are located the sieve tray 4 of below from this moment and fall bamboo end frame 31. After repeated overturning, the bamboo powder with the aperture smaller than that of the sieve tray 4 is completely sieved into the bamboo powder frame 31.

The two single-shaft linear cylinders 15 located above at the moment are started, the two sieve tray clamps 16 located above are separated, the sieve tray 4 located above at the moment is taken out at the same time, and bamboo chips exceeding the aperture of the sieve tray 4 can be crushed again.

The principle and the implementation of the present application are explained in the present application by using specific examples, and the above description of the embodiments is only used to help understanding the technical solution and the core idea of the present application. It will be apparent to those skilled in the art that various changes and modifications can be made in the present invention without departing from the principles of the invention, and these changes and modifications also fall within the scope of the claims of the present application.