CN115992460A - Closed condensation circulation bleaching reactor and efficient bleaching method - Google Patents
Closed condensation circulation bleaching reactor and efficient bleaching method Download PDFInfo
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- CN115992460A CN115992460A CN202310067914.9A CN202310067914A CN115992460A CN 115992460 A CN115992460 A CN 115992460A CN 202310067914 A CN202310067914 A CN 202310067914A CN 115992460 A CN115992460 A CN 115992460A
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- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims description 6
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- NTHWMYGWWRZVTN-UHFFFAOYSA-N sodium silicate Chemical compound [Na+].[Na+].[O-][Si]([O-])=O NTHWMYGWWRZVTN-UHFFFAOYSA-N 0.000 claims description 2
- 229910052911 sodium silicate Inorganic materials 0.000 claims description 2
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Images
Abstract
The invention discloses a closed condensation circulation bleaching reactor and a high-efficiency bleaching method. A slurry tray is placed in the reaction kettle body and comprises a tray body, and a steam channel is formed in the middle of the tray body; the middle part of the reaction kettle cover is provided with a condensing pipe, the outlet at the lower end of the condensing pipe is communicated with the inside of the reaction kettle body, and the inner diameter of the outlet at the lower end of the condensing pipe is larger than the outer diameter of the steam channel. After the reaction kettle cover is installed, the outlet at the lower end of the condensing tube should cover the steam channel to ensure that all solvent steam generated by the kettle bottom enters the condensing tube. The bleaching reactor is used for bleaching, the separation and placement of the pulp and the organic solvent can be realized through the pulp tray, so that the concentration of a bleaching system in the initial bleaching stage can be ensured, and the organic solvent flowing back from the condensing pipe can be used for repeatedly flushing the pulp in the later bleaching stage, so that chromophores can be better dissolved out, and the bleaching efficiency and the bleaching effect are improved.
Description
Technical Field
The invention belongs to the technical field of paper pulp bleaching, and particularly relates to a closed condensation circulation bleaching reactor and a high-efficiency bleaching method.
Background
The bamboo plants grow fast, the length-width ratio of the fibers is high, and the bamboo plants are slender and stiff, and are traditional pulping and papermaking raw materials in China. In recent years, natural color bamboo pulp household paper is accepted by consumers by the environment-friendly concept and the natural color attribute of fiber. The bamboo natural color chemimechanical pulp has excellent strength performance and can meet the paper making requirement of natural color packaging paper. However, in the field of bleached chemimechanical pulp, due to inherent characteristic of bamboo, the conventional aqueous phase bleaching technology cannot prepare high-whiteness bamboo chemimechanical pulp (whiteness is not less than 78% ISO), so that the application of bamboo resources in the field of high-added value paper products such as white cardboard, white paperboard and the like is restricted.
The bleaching process of bamboo pulp and its mechanism [ J ]. Technological guide, 2016, 34 (19): 76-80.) was conducted by using 5 optimized bleaching schemes of hydrogen peroxide bleaching, high temperature pressure hydrogen peroxide bleaching, peracetic acid bleaching, sodium borohydride bleaching, sodium dithionite bleaching, etc. the bleaching of powder single bamboo chemimechanical pulp was investigated by using the system of bleaching schemes, and found that Shan Duanpiao employs high temperature and high pressure hydrogen peroxide to bleach to the highest whiteness (70.90% ISO), and that the two-stage bleaching employs hydrogen peroxide-sodium dithionite to the highest whiteness (73.85%) ISO. The research results show that the refractory chromophoric groups of the bamboo chemimechanical pulp cannot be deeply removed under the conventional reaction conditions by using a conventional oxidant or a reducing agent. The group (Liang Fangmin, fang Guigan, jiao Jian, etc.) study of the pulping process and bleaching performance of the Ci Zhu CTMP [ J ]. Papermaking science and technology, 2013, (3) 1-5; liang Fangmin, fang Guigan, jiao Jian, etc. the influence of chemical pretreatment temperature on the bleaching performance of the Ci Zhu machine pulp [ J ]. Paper and papermaking, 2011,30 (5): 23-26; liang Fangmin, fang Guigan, jiao Jian, etc. the influence of chemical pretreatment on the pulping bleaching performance of the Ci Zhu machine pulp [ J ]. China paper industry, 2011 (8): 16-20.) system study on the alkaline hydrogen peroxide bleaching performance of the Ci Zhu chemical mechanical pulp, and the whiteness is found to be only 69.9% ISO and 70.9% ISO after the appropriate pretreatment, respectively, of the Ci Zhu chemical mechanical pulp with the original whiteness reaching 55.6% ISO is bleached by single-stage hydrogen peroxide and peracetic acid. After increasing the hydrogen peroxide usage to 12%, it was found that the pulp whiteness could not exceed 75% ISO even though there was a lot of hydrogen peroxide left in the bleaching raffinate. The above study demonstrates that certain yellow-green intractable chromophores in the bamboo pulping liquor cannot be destroyed by conventional bleach hydrogen peroxide.
The patent number ZL201610348522.X discloses a method for preparing bamboo high whiteness bleaching machine pulp by using alcohol solvent, the patent technology is characterized in that: (1) Adding organic solvent (preferably ethanol) based on conventional bleaching process; (2) sealing the bleaching system; (3) The temperature is always kept higher than the boiling point of the organic solvent during the bleaching process. Based on the characteristics, the main advantages of the technology of the patent are as follows: 1) The sediment in microscopic pore canals of the fiber raw materials is destroyed by utilizing the dissolution of solvent molecules, a liquid medicine permeation channel is opened, and the deep permeation of the bleaching liquid medicine into the slurry is assisted; 2) Hydrogen peroxide is active in nature and is easily decomposed into oxygen and water; in a normal pressure system, under the influence of temperature difference, oxygen generated by decomposition is dissipated into air along with water vapor, and does not participate in bleaching reaction; in the closed system, as the reaction proceeds, oxygen in a high-pressure environment deeply permeates the slurry and damages the conjugated chromophores of the slurry by itself oxidizing property. The closed system is beneficial to improving the utilization rate of hydrogen peroxide; 3) Most of the chromophoric groups in the pulp are conjugated structures formed by benzene rings in lignin structures and adjacent carbon-carbon double bonds, carbonyl groups and the like. The polarity of the structure is weaker, the solubility in water is small, and the solubility in organic solvent is large, so that the organic solvent is added into the bleaching system to facilitate the dissolution of the chromophores, and the bleaching effect is improved. ( Liang F, fang G, jiao J, et al modified Hydrogen Peroxide Bleaching of Bamboo Chemo-mechanical Pulp Using Aqueous Alcohol Media [ J ]. North Carolina State University, college of Natural Resources,2018 (1): 870-881. )
The key point of the technology is that a large amount of organic solvent is required to dissolve out the substances containing the chromophoric groups in the slurry. If a large amount of organic solvent is added at a time, the concentrations of hydrogen peroxide and sodium hydroxide, which are main reactants for bleaching, in the system are too low, and the final bleaching effect is reduced. Therefore, when using the conventional pressure-resistant reactor, it is necessary to repeat the bleaching treatment a plurality of times to achieve the optimum bleaching effect, repeatedly squeeze out the waste liquid in which the dissolved chromonic material has been saturated, and add a new reaction solvent. This results in a bleaching process that is cumbersome to operate, time consuming and inefficient.
Disclosure of Invention
Based on the defects of the prior art, the invention aims to provide a closed condensation circulation bleaching reactor and a high-efficiency bleaching method, the bleaching reactor is used for bleaching, and pure organic solvent generated by condensation circulation repeatedly washes pulp, so that chromophores can be better dissolved out, and the problems that the bleaching effect is influenced by one-time addition of the solvent, and the reaction efficiency is reduced by a small amount of repeated addition are solved.
In order to achieve the above purpose, the invention adopts the following technical scheme:
the first object of the invention is to provide a closed condensation cycle bleaching reactor, which comprises a reaction kettle body and a reaction kettle cover which is connected with the reaction kettle body in a sealing way; preferably, the reaction kettle body and the reaction kettle cover can be in sealing connection through a quick-opening flange; wherein:
a slurry tray is arranged above the inside of the reaction kettle body, and a supporting component for supporting the slurry tray is fixed on the inner wall of the reaction kettle body; the slurry tray comprises a tray body, a steam channel is formed in the middle of the tray body, and the outer diameter of the tray body is smaller than the inner diameter of the reaction kettle body, so that a gap is formed between the slurry tray and the reaction kettle body, and the organic solvent can flow downwards into the kettle bottom conveniently;
a condensing pipe is arranged in the middle of the reaction kettle cover, the outlet of the lower end of the condensing pipe is communicated with the inside of the reaction kettle body, and the outlet of the lower end of the condensing pipe faces the steam channel; the top of the condensing pipe is provided with a sealing valve. Further, the inner diameter of the outlet at the lower end of the condensing tube is larger than the outer diameter of the steam channel, the top end of the steam channel is positioned inside the outlet at the lower end of the condensing tube, so that the organic solvent steam evaporated at the bottom of the kettle can be ensured to fully enter the condensing tube, and meanwhile, the upward evaporation airflow and the downward condensation liquid drop are not mutually interfered.
As the preferable technical scheme, the supporting component is a plurality of supporting blocks fixed on the inner wall of the reaction kettle body, and the plurality of supporting blocks are fixed on the inner wall of the reaction kettle body at equal intervals along the circumferential direction. Through the supporting role of the supporting block on the slurry tray, the slurry tray can be stably clamped in the reaction kettle body. The height of the supporting block from the bottom of the reaction kettle is greater than half of the whole height of the reaction kettle body, so that enough space is ensured for placing the reflux organic solvent.
As an optimal technical scheme, the slurry tray is in an inverted funnel shape, the included angle alpha between the tray body and the horizontal plane is 2-10 degrees, and the small-angle included angle design can enable the solvent to flow downwards along the tray body, so that the separation of the solvent and the slurry is convenient to realize; the periphery side of tray body is fixed with the thick liquids baffle, and thick liquids baffle can prevent thick liquids gliding.
As an optimal technical scheme, a sample inlet, an exhaust port, a pressure gauge, a thermometer and a pressure relief device are also arranged on the reaction kettle cover; furthermore, the pressure relief device is a rupture disk or a safety valve, and when the pressure in the reaction kettle body rises to exceed a specified value, the pressure is relieved to the outside of the kettle through the pressure relief device, so that the pressure relief device plays an important role in protecting personal safety and equipment operation.
A second object of the present invention is to provide a high efficiency bleaching process which is accomplished using a closed condensing cycle bleaching reactor as described in the first object above, comprising the steps of:
adding an organic solvent into the reaction kettle body, wherein the height of the organic solvent is lower than that of the slurry tray; further, the organic solvent is at least one of methanol, ethanol, ethylene glycol, 1-propanol, 2-propanol, propylene glycol and glycerol; the height of the organic solvent is not more than half of the height of the reaction kettle.
Spreading filter cloth on a slurry tray, and spreading the slurry to be bleached mixed with bleaching agent on the filter cloth, wherein the filter cloth is preferably annular filter cloth, and the middle part of the annular filter cloth is provided with a through hole matched with the outer diameter of a steam channel; the number of holes of the filter cloth is not more than 200 meshes; the outer diameter of the filter cloth is larger than the inner diameter of the kettle body. The bleaching agents include hydrogen peroxide, sodium hydroxide, sodium silicate and DTPA (pentasodium diethylenetriamine pentaacetate, chelating agent). Covering the reaction kettle body and the reaction kettle cover, and discharging original air in the reaction kettle body; specifically, the method for exhausting the original air in the reaction kettle body comprises the following steps: keeping the kettle body airtight, increasing the temperature in the kettle to be higher than the boiling point of the organic solvent, opening an exhaust port on the kettle cover and a sealing valve at the top end of a condensing tube when the pressure gauge shows that the pressure in the kettle is higher than the atmospheric pressure, and ejecting the air in the kettle by utilizing solvent steam. When the pressure of the pressure gauge returns to the initial value, the air is considered to be exhausted, the kettle is filled with solvent vapor, and at the moment, the exhaust port on the kettle cover and the sealing valve at the top end of the condensing pipe are closed, and the reaction is continued.
The reaction kettle body is heated by a heating device with temperature control (such as an oil bath pot with temperature control) to enable the internal temperature of the reaction kettle body to reach a set temperature (the temperature is higher than the boiling point of an organic solvent), and the reaction is carried out for 30 minutes (more than 80% of the reaction can be completed in the first 30 minutes of alkaline hydrogen peroxide bleaching according to the classical bleaching theory, and solvent circulation is not used in the first half hour of the reaction in order to ensure the concentration of reactants). Injecting condensed water into the outer sleeve of the condensing tube, enabling organic steam generated by evaporation of the organic solvent to enter the inner tube of the condensing tube through a steam channel, dripping slurry into the inner wall of the condensing tube along the outlet of the lower end of the condensing tube after condensation, enabling the organic solvent to flow into the bottom of the reaction kettle from a gap between the outer edge of the slurry tray and the inner wall of the reaction kettle after being adsorbed and saturated by the slurry, and completing circulation; and stopping heating until bleaching is completed.
Compared with the prior art, the invention has the beneficial effects that:
(1) According to the closed condensing and circulating bleaching reactor provided by the invention, the slurry is borne by the slurry tray, so that the slurry is separated from the organic solvent at the bottom of the reaction kettle body in the bleaching process, and the concentration of the bleaching liquid is ensured. The organic solvent which flows back from the condensing pipe is used for repeatedly flushing the slurry, and the solvent which flows back from the condensing pipe is a pure solvent which does not contain chromophores, so that the solvent has better solubility to the slurry, chromophores can be better dissolved out, and the bleaching effect is improved.
(2) The closed condensation circulation bleaching reactor provided by the invention is utilized for bleaching, and in the bleaching process, the organic solvent circulated and reflowed from the inside of the condensation pipe is utilized for repeatedly flushing the slurry, so that the water washing step among multiple bleaching treatments in the conventional bleaching method can be omitted, the continuity of bleaching reaction can be ensured, and the bleaching efficiency is improved.
(3) The high-efficiency bleaching method provided by the invention can improve the utilization rate of the organic solvent, and because the color-forming substances are hard to volatilize, the color-forming substances dissolved by bleaching are gathered at the bottom of the reaction kettle body. The organic solvent generated by distillation and condensation is pure, so that the slurry is always washed by the pure solvent, and the material exchange efficiency is higher. The bleaching method provided by the invention realizes high-efficiency bleaching on the premise of using less solvent, reduces the use cost of raw materials on one hand, reduces the treatment pressure of waste water and waste liquid in the later stage on the other hand, and has good economic benefit.
Drawings
FIG. 1 is a cross-sectional view of a closed condensing cycle bleach reactor provided by the present invention;
fig. 2 is an enlarged view of the portion M of fig. 1;
FIG. 3 is a top view of the reactor cover;
FIG. 4 is a top view of the reactor body;
FIG. 5 is a top view of the slurry tray;
FIG. 6 is a schematic illustration of the placement of slurry in a slurry tray;
reference numerals: the reaction kettle comprises a 1-reaction kettle body, a 2-reaction kettle cover, a 3-quick-opening flange, a 4-tray body, a 5-steam channel, a 6-slurry baffle, a 7-condenser pipe, an 8-sealing valve, a 9-sample inlet, a 10-pressure gauge, an 11-thermometer, a 12-pressure relief device, a 13-supporting component, a 14-exhaust port, 15-slurry and 16-filter cloth.
Detailed Description
The present invention will be further described with reference to the following examples and drawings so that those skilled in the art may better understand the present invention and practice it, but the examples are not to be construed as limiting the present invention.
It should be noted that, in the present invention, unless explicitly specified and limited otherwise, terms such as "mounted," "connected," "fixed," and the like are to be construed broadly and may be, for example, fixedly connected, detachably connected, or integrally connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.
It is to be understood that the terms "upper," "lower," "top," "bottom," "inner," "outer," and the like are used in an orientation or positional relationship based on that shown in the drawings, merely to facilitate describing the present invention and to simplify the description, and do not indicate or imply that the devices or elements being referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore should not be construed as limiting the present invention.
Examples
Referring to fig. 1 to 6, a closed condensing cycle bleaching reactor comprises a reaction kettle body 1 and a reaction kettle cover 2 which is in sealing connection with the reaction kettle body 1; preferably, the reaction kettle body 1 and the reaction kettle cover 2 can be in sealing connection through a quick-opening flange 3; the reaction kettle body 1 and the reaction kettle cover 2 can be connected in a sealing manner by other connection modes such as threads. Wherein:
the slurry tray is placed above the inside of the reaction kettle body 1, the inner wall of the reaction kettle body is fixed with a supporting component 13 for supporting the slurry tray, and specifically, the supporting component 13 is a plurality of supporting blocks fixed on the inner wall of the reaction kettle body, and the plurality of supporting blocks are fixed on the inner wall of the reaction kettle body at equal intervals along the circumferential direction. As a preferred embodiment, the number of the support blocks is designed to be four; the slurry tray comprises a tray body 4, a steam channel 5 is formed in the middle of the tray body 4, and the outer diameter of the tray body 4 is smaller than the inner diameter of the reaction kettle body 1, so that a certain gap is reserved between the tray body and the reaction kettle body, and a solvent can flow into the kettle bottom conveniently under the action of gravity; further preferably, the slurry tray is in an inverted funnel shape, an included angle alpha between the tray body and the horizontal plane is 2-10 degrees, a slurry baffle 6 is fixed on the peripheral side of the tray body, and the slurry baffle 6 can prevent the slurry 15 from sliding downwards.
A condensing pipe 7 is arranged in the middle of the reaction kettle cover 2, the outlet of the lower end of the condensing pipe 7 is communicated with the inside of the reaction kettle body 1, and the outlet of the lower end of the condensing pipe 7 faces the steam channel 5; a sealing valve 8 is arranged at the top of the condensation pipe 7. Further, the inner diameter of the outlet at the lower end of the condensing tube 7 is larger than the outer diameter of the steam channel 5, and the top end of the steam channel 5 is positioned inside the outlet at the lower end of the condensing tube, so that the mutual noninterference of the solvent ascending evaporation air flow and descending condensation liquid drops can be ensured.
In order to facilitate the addition of reagents (if needed) into the reaction kettle body, a sample inlet 9 is designed on the reaction kettle cover 2; in order to monitor parameters such as temperature, pressure and the like in the reaction kettle body, a pressure gauge 10 and a thermometer 11 are arranged on the reaction kettle cover. In addition, in order to improve the safety performance of the reactor, a pressure relief device 12 is arranged on the reaction kettle cover, and the pressure relief device 12 can be a rupture disk or a safety valve; the reaction kettle cover is also provided with an exhaust port 14.
Comparative examples 1-2 and inventive example 1
Bleaching the slurry: mechanical pulp of Sagittaria sagittifolia
The vessel used in comparative application example 1 was a conventional pressure-resistant glass bottle, and the reaction solvent was added at one time. The specific operation is as follows: the preparation method comprises the steps of weighing a mechanical pulp of Sagittaria sagittifolia corresponding to 50g of absolute dry weight, adding bleaching chemicals according to the technological parameters of comparative application example 1 in table 1, fully and uniformly mixing, filling the pulp into a pressure-resistant glass bottle, bleaching in a water bath kettle, and carrying out bleaching reaction at the temperature of 95 ℃ for 2 hours. Taking out the slurry in the bottle after the reaction is finished, pouring the slurry into 1L of distilled water, fully and uniformly stirring, and washing the slurry in a buchner funnel filled with filter cloth by using a suction filtration device until the pH value of the filtrate is 7.0+/-0.5. The pulp whiteness is measured according to GB/T7974-2002 (measurement of brightness (diffuse/perpendicular) of paper, board and pulp).
The vessel used in comparative application example 2 was a conventional pressure-resistant glass bottle, and the reaction solvent was added in 3 portions. The specific operation is as follows: the preparation method comprises the steps of weighing a mechanical pulp of Sagittaria sagittifolia corresponding to 50g of absolute dry weight, adding bleaching chemicals according to the first stage treatment process parameters of comparative application example 2 in table 1, fully and uniformly mixing, filling the pulp into a pressure-resistant glass bottle, bleaching in a water bath kettle, and carrying out bleaching reaction at the temperature of 95 ℃ for 40min. Taking out the slurry in the bottle after the reaction is finished, pouring the slurry into 1L of distilled water, fully and uniformly stirring, and washing the slurry in a buchner funnel filled with filter cloth by using a suction filtration device until the pH value of the filtrate is 7.0+/-0.5. After measuring the dryness of the resulting pulp, the bleaching chemical was added according to the second stage treatment process parameters of comparative application example 2 in table 1, the dryness of the resulting pulp was measured after repeating the first stage treatment operation, the bleaching chemical was added according to the third stage treatment process parameters of comparative application example 2 in table 1, and the whiteness of the pulp was measured according to GB/T7974-2002 (measurement of brightness (brightness) of paper, board and pulp (diffusion/vertical method)).
The vessel used in application example 1 was a closed condensing cycle bleaching reactor shown in FIG. 1 of the present invention, and the reaction solvent was added at one time. The specific operation is as follows: the mechanical pulp of Sagittaria sagittifolia corresponding to 50g absolute dry weight is weighed, the bleaching chemical is added according to the process parameters of the application example 1 in the table 1, wherein one third of ethanol is mixed with the pulp to participate in the initial bleaching reaction, and two thirds of ethanol is placed at the bottom of the reactor for reflux flushing. After fully and uniformly mixing, the slurry is filled into the reactor of the invention, bleaching is carried out in a water bath kettle, the bleaching reaction temperature is 95 ℃, and the total reaction time is 2 hours. And in the initial stage of the reaction, all valves are closed, when the temperature in the reactor exceeds the boiling point of the solvent, the pressure gauge displays that the pressure of the closed system rises, the kettle cover exhaust port 14 and the condenser pipe sealing valve 8 are opened, the air in the kettle is discharged by utilizing solvent vapor, and after the pressure gauge displays that the pressure is zero, the exhaust port 14 and the sealing valve 8 are closed, and the temperature of the system is continuously increased to the process design temperature. And after the temperature in the kettle reaches the set temperature, keeping each valve closed, injecting condensed water into a condensing pipe after the reaction is carried out for 0.5 hour, stopping heating after the reaction is continued for 1.5 hours, opening an exhaust port 14 to guide steam in the kettle into a tail gas collecting system, closing the exhaust port 14 when the pressure gauge shows that the pressure in the kettle is normal pressure, opening a quick-opening flange 3, and taking out slurry. The obtained slurry was poured into 1L of distilled water, and after stirring well, the slurry was washed with distilled water in a buchner funnel with a filter cloth by using a suction filtration device until the pH value of the filtrate was 7.0.+ -. 0.5. The pulp whiteness is measured according to GB/T7974-2002 (measurement of brightness (diffuse/perpendicular) of paper, board and pulp).
Table 1 reaction conditions and experimental results for each application example
* : one third of the mixture is mixed with the slurry, and two thirds of the mixture is placed at the bottom of the reactor for reflux
As can be seen from the experimental results in Table 1, compared with comparative application examples 1 and 2, the whiteness of the obtained slurry is further improved by adopting the bleaching method performed by the closed condensation cycle bleaching reactor provided by the invention under the condition of the same bleaching chemical dosage, which can reach more than 80% ISO. Compared with the multi-stage bleaching method in the comparative application example 2, the bleaching method in the application example 1 omits the water washing operation between two adjacent stages of bleaching treatments, only needs to wash the obtained pulp once after bleaching is finished, obviously reduces the waste water yield, can avoid repeated material taking and discharging operations caused by multiple water washing, greatly simplifies the operation steps and improves the bleaching efficiency.
It will be apparent that the described embodiments are some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Claims (9)
1. A closed condensing cycle bleaching reactor, characterized in that: comprises a reaction kettle body and a reaction kettle cover which is connected with the reaction kettle body in a sealing way; wherein:
a slurry tray is arranged above the inside of the reaction kettle body, and a supporting component for supporting the slurry tray is fixed on the inner wall of the reaction kettle body; the slurry tray comprises a tray body, wherein a steam channel is formed in the middle of the tray body, and the outer diameter of the tray body is smaller than the inner diameter of the reaction kettle body;
a condensing pipe is arranged in the middle of the reaction kettle cover, and an outlet at the lower end of the condensing pipe is communicated with the inside of the reaction kettle body; the inner diameter of the outlet at the lower end of the condensing pipe is larger than the outer diameter of the steam channel, and the top end of the steam channel is positioned in the outlet at the lower end of the condensing pipe; and a sealing valve is arranged at the top of the condensing pipe.
2. The closed condensing cycle bleaching reactor according to claim 1, wherein: the support assembly is a plurality of support blocks fixed on the inner wall of the reaction kettle body, and the plurality of support blocks are fixed on the inner wall of the reaction kettle body at equal intervals along the circumferential direction.
3. The closed condensing cycle bleaching reactor according to claim 1 or 2, wherein: the slurry tray is in an inverted funnel shape, and the included angle between the tray body and the horizontal plane is 2-10 degrees; and a slurry baffle is fixed on the outer peripheral side of the tray body.
4. A closed condensing cycle bleaching reactor according to claim 3, wherein: the reaction kettle body and the reaction kettle cover are in sealing connection through a quick-opening flange.
5. The closed condensing cycle bleaching reactor according to claim 4, wherein: and the reaction kettle cover is also provided with a sample inlet, an exhaust port, a pressure gauge, a thermometer and a pressure relief device.
6. The closed condensing cycle bleaching reactor according to claim 5, wherein: the pressure relief device is a rupture disk or a safety valve.
7. A high efficiency bleaching method, characterized in that: the high efficiency bleaching process is accomplished using a closed condensing cycle bleaching reactor according to any one of claims 1 to 6, comprising the steps of:
adding an organic solvent into the reaction kettle body, wherein the height of the organic solvent is lower than that of the slurry tray;
spreading filter cloth on a slurry tray, spreading the slurry to be bleached mixed with bleaching agent on the filter cloth, covering a reaction kettle body and a reaction kettle cover, keeping no condensed water in a condensing tube outer sleeve at the moment, and discharging original air in the reaction kettle body;
keeping the reaction kettle body airtight, continuously heating the reaction kettle body to a set reaction temperature which is higher than the boiling point of the organic solvent, injecting condensed water into the outer sleeve of the condensing pipe after the reaction is carried out for thirty minutes, enabling organic steam generated by evaporation of the organic solvent to enter the condensing pipe through a steam channel, dripping slurry along the outlet of the lower end of the condensing pipe after the inner wall of the condensing pipe is condensed, enabling the organic solvent to flow into the kettle bottom from a gap between the outer edge of the slurry tray and the inner wall of the reaction kettle body after the organic solvent is adsorbed and saturated by the slurry, and completing circulation; and stopping heating until bleaching is completed.
8. The efficient bleaching method according to claim 7, wherein: the organic solvent is at least one of methanol, ethanol, ethylene glycol, 1-propanol, 2-propanol, propylene glycol and glycerol; the bleaching agents include hydrogen peroxide, sodium hydroxide, sodium silicate and pentasodium diethylenetriamine pentaacetate.
9. The efficient bleaching method according to claim 7, wherein: the filter cloth is annular filter cloth, and the middle part of the annular filter cloth is provided with a through hole matched with the outer diameter of the steam channel; the number of holes of the filter cloth is not more than 200 meshes; the outer diameter of the filter cloth is larger than the radius of the reaction kettle so as to ensure that the slurry is always on the slurry tray.
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| GB710691A (en) * | 1950-06-21 | 1954-06-16 | Robert Currie Campbell | Method and apparatus for the preparation and refining of fibres from cellulosic fibrous material |
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| CN108642943A (en) * | 2018-04-03 | 2018-10-12 | 中国林业科学研究院林产化学工业研究所 | A method of preparing high-whiteness high-strength Eucalyptus chemi-mechanical pulp |
| CN114053960A (en) * | 2021-11-08 | 2022-02-18 | 大连大学 | Boiling reaction kettle device and method for improving mass transfer and heat transfer efficiency of high-viscosity reaction system |
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Patent Citations (5)
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| GB710691A (en) * | 1950-06-21 | 1954-06-16 | Robert Currie Campbell | Method and apparatus for the preparation and refining of fibres from cellulosic fibrous material |
| CN106012627A (en) * | 2016-05-24 | 2016-10-12 | 中国林业科学研究院林产化学工业研究所 | Method for preparing high-brightness bleached mechanical pulp of bamboo by utilizing alcohol solvent |
| CN207031907U (en) * | 2017-05-17 | 2018-02-23 | 四川省犍为凤生纸业有限责任公司 | A kind of high pressure delignification equipment for preparing bamboo pulp |
| CN108642943A (en) * | 2018-04-03 | 2018-10-12 | 中国林业科学研究院林产化学工业研究所 | A method of preparing high-whiteness high-strength Eucalyptus chemi-mechanical pulp |
| CN114053960A (en) * | 2021-11-08 | 2022-02-18 | 大连大学 | Boiling reaction kettle device and method for improving mass transfer and heat transfer efficiency of high-viscosity reaction system |
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