CN109267413B - A method and device for preparing oxygen-based high-efficiency clean and bleached pulp - Google Patents

Abstract

The invention discloses a method for preparing oxygen-based high-efficiency clean and bleached pulp and its device; the hollow mixing rotor in the device is connected to the shaft end of the high-speed frequency conversion motor main shaft located at the bottom of the mixing reaction chamber through bolts; the blades of the hollow mixing rotor have a symmetrical hollow structure Multiple linear blades or spiral blades distributed. It is widely applicable to oxygen bleaching or ozone bleaching of chemical pulp of any raw material. All oxygen-containing bleaching agents are used. The final products of chemical reaction decomposition are oxygen and water, which eliminates the residue of harmful substances in the bleached pulp. The bleaching agent prepared by this device The pulp whiteness is higher, more uniform, and less likely to return to yellow; a variable frequency motor is used to drive the hollow rotor through the main shaft and mechanical seal for high-speed mixing, making the mass transfer between the medium and high-concentration slurry and the oxygen-based gaseous bleach in the mixing reaction chamber more efficient , the mixing contact is more uniform and sufficient; the device has a reasonable structure, can accurately control the consumption of chemical liquid, oxygen and ozone, and the process of preparing bleached pulp is simple and efficient.

Description

A method and device for preparing oxygen-based high-efficiency clean and bleached pulp

Technical field

The invention relates to the technical field of pulping and papermaking, and in particular to a method for preparing oxygen-based high-efficiency clean and bleached pulp and its device.

Background technique

Due to the constraints of resources, environment, efficiency and other aspects, the pulp and paper industry continues to develop towards a modern large-scale industry with high efficiency, high quality, low consumption, low pollution and low emissions. In recent years, our country has introduced a series of strict policies and regulations to achieve the sustainable development of pulp and paper, continuously promote technological upgrading of enterprises, save energy and reduce emissions, prevent and control pollution, achieve clean production, and accelerate the advancement of oxygen delignification, ozone bleaching, and ECF element-free Chlorine bleaching and TCF chlorine-free bleaching technologies are widely used.

Oxygen is a common oxidant that can oxidatively degrade residual lignin in pulp under alkaline conditions. Oxygen delignification (also known as oxygen bleaching) is a process that uses oxygen and alkali to remove residual lignin in unbleached pulp. This process does not produce organic chlorides and can significantly reduce the residual lignin in the pulp and improve the whiteness of the pulp. degree and low cost. Ozone is the strongest oxidant available in industry. Its oxidation potential is 2.07 and its oxidation ability is higher than _ClO2 . The high bleaching efficiency of ozone can greatly reduce the consumption of bleaching chemicals, including ClO ₂ for ECF bleaching and H ₂ O ₂ for TCF bleaching. Ozone bleaching will not produce harmful chlorine-containing compounds. The main mechanism of ozone bleaching is the reaction between ozone and lignin, destroying the aromatic ring structure of lignin into a muconic acid structure. At present, in the industrial application and experimental research of oxygen delignification and ozone bleaching, medium-consistency and high-consistency pulp concentrations are mainly used. Most of the current bleaching processes are medium-consistency bleaching technical processes, and the process has become increasingly mature. Medium-concentration bleaching technology has considerable advantages in all aspects compared to low-concentration bleaching technology. However, the realization of the bleaching process requires a medium consistency pump to fluidize the medium consistency pulp. In addition, the mixing effect of the medium consistency pulp with oxygen and ozone bleaching agents is also the key to determining the process effect. Good and efficient mixing provides uniform bleaching conditions, reduces chemical and energy consumption, reduces reaction time and improves product quality. Before the oxygen-based gaseous bleach comes into contact with the fiber, it must go through a gas-liquid mass transfer process. It is first dissolved in the water on the surface of the fiber, and then quickly interacts with the fiber cell cavity and the water adsorbed on the cell wall through the action of the medium-thickness mixer. Exchange, dissolve in the exchanged water, and repeat the cycle until the fiber is completely surrounded by the oxygen-based gaseous bleach dissolved in the water. The size of oxygen bleach bubbles directly affects the diffusion rate. The smaller the bubbles, the more conducive to diffusion and mixing. However, the realization of smaller-sized bubbles mainly depends on the degree of turbulence of the gas, liquid and solid phases, and thus also depends on the high shear stress generated by the medium-concentration mixer.

Patent CN206562539U discloses an experimental device for ozone bleaching of medium and low consistency pulp. The device is equipped with an air inlet pipe and an aeration head at the bottom of the tank. In theory, it can realize the bottom air intake of ozone, and form a large amount of ozone in the slurry through the aeration head. Small bubbles increase the contact area between ozone and fiber. Driven by the stirring paddle, the slurry reacts quickly with ozone. However, the size of the bubbles formed by relying solely on the aeration head is still large. During the mixing process, due to the gravity and centrifugal force exerted on the slurry, especially when the pulp concentration is slightly higher, it is very easy to block the aeration head and affect the air intake; in addition, the tank There is a separate air inlet pipe on one side of the body and an aeration head on the bottom, which is particularly easy to form a dead corner for mixing. The slurry can easily block the gap between the air inlet pipe and the tank. In addition, the air inlet pipe and aeration head have the risk of entangling the stirring paddle during mixing; The motor is placed upward, the stirring shaft is vertically covered and goes deep into the tank, and the stirring paddle is fixed on the bottom end of the stirring shaft. In this structure, the stirring shaft is long, the stirring paddle is square, and the actual mixing working area of the stirring paddle is very small. Its implementation In this example, the pulp concentration is low-consistency 3% to 5%, which is more suitable for low-consistency bleaching. If it is medium-high-consistency pulp, its stirring effect is extremely limited; the sealing of the rotation gap between the stirring shaft and the cover is not introduced.

Rapid and efficient mixing is a key factor in achieving medium and high-concentration ozone bleaching. Since most of the theoretical research on ozone bleaching conducted in China focuses on process conditions, practical applications include pilot tests of rapid mixing of ozone and medium- and high-concentration pulp and efficient reactions. The development of experimental devices and engineering equipment involves relatively little. At present, there are only a few production lines that use ozone for medium and high concentration bleaching in China. There is no complete set of experimental equipment for medium and high concentration ozone bleaching. It is impossible to conduct systematic experiments on medium and high concentration ozone. Pulp bleaching, especially the mass transfer mechanism and delignification mechanism of ozone in medium-consistency pulp, as well as the process parameters of ozone medium-concentration bleaching, were studied in depth. Due to the complex mass transfer of medium-concentration ozone bleaching, which requires higher experimental conditions such as experimental equipment, ozone concentration pressure and high-intensity mixing technology, the research reported so far is mostly limited to low-concentration, high-concentration ozone bleaching and medium-concentration ozone bleaching with uneven low-speed mixing. Ozone bleaching has little reference value for upgrading the current medium-concentration ozone bleaching technology. Most of the existing experimental devices for oxygen bleaching and ozone bleaching are reactors with good sealing but cannot be mixed; or they can be stirred and mixed at medium and low speeds and have good sealing, but are limited to the reaction of low-consistency pulp. Tank; or it has good sealing and uses rolling or rotating for mixing, but it is mostly used in reaction kettles for high-consistency pulp bleaching. In addition, the above-mentioned experimental equipment is difficult to achieve the experimental requirements of high turbulence, fluidization, ozone introduction, pressure reaction, high-speed mixing, rapid reaction, efficient bleaching, and uniform whiteness of medium-consistency pulp at the same time. In addition, medium-consistency pulp used in factory industrial applications is used. Experimental research on pumps, ozone medium-consistency mixers, and reaction towers is expensive and difficult to implement. Therefore, there is an urgent need to develop an experimental ozone bleaching device for medium-to-high consistency pulp, and to develop an oxygen-based oxygen and ozone efficient bleaching medium-to-high consistency pulp. Method for preparing thick pulp.

Contents of the invention

The object of the present invention is to overcome the shortcomings and deficiencies of the above-mentioned prior art and provide a method for preparing oxygen-based high-efficiency clean and bleached pulp and its device. It solves the difficulty of existing technology in meeting the demand for efficient reactions of oxygen bleaching and ozone bleaching, and overcomes the shortcoming of being unable to oxygenate medium-consistency pulp to high whiteness under high-intensity turbulent conditions.

The present invention is realized through the following technical solutions:

An oxygen-based high-efficiency cleaning and bleaching experimental device for pulp, including a mixing reaction chamber 16 with a cover 10 located on a frame 27, a high-speed variable frequency motor 24, and a DCS operating system 26;

A cover 10 is provided above the mixing reaction chamber 16, a heater 15 is installed on the outer wall of the mixing reaction chamber 16, and a hollow mixing rotor 13 is provided inside the mixing reaction chamber 16;

An aeration pipe 14 with a porous array is provided below the center of the cover 10 and can be inserted into the center of the hollow mixing rotor 13; the outer port of the aeration pipe 14 is connected to the liquid inlet valve 3 and the liquid pump 2 through a three-way interface. , liquid inlet pipe 1 and air inlet valve 6, air pump 5, air inlet pipe 4;

An exhaust valve 11 is provided above the cover 10, and the exhaust valve 11 is connected in sequence to an exhaust ozone concentration detector 22 and an ozone exhaust treatment device 23 through an exhaust pipe 12;

The hollow mixing rotor 13 is connected to the shaft end of the main shaft 19 of the high-speed variable frequency motor 24 at the bottom of the mixing reaction chamber 16 through bolts 28; the blades of the hollow mixing rotor 13 are a plurality of linear blades or hollow structures that are parallel and symmetrically distributed. Multiple spiral blades distributed symmetrically.

The two ends of the blades of the hollow mixing rotor 13 are respectively fixed on two coaxially distributed rings up and down, and the lower ring is connected to the shaft end of the main shaft 19 at the bottom of the mixing reaction chamber 16 through bolts 28; a porous array is provided The aeration tube 14 extends into the inner center of the hollow mixing rotor 13 through the upper ring; when the hollow mixing rotor 13 rotates, a vacuum area is formed at its center; under the disturbance of the blades, the fluid in the mixing reaction chamber 16 is Convection is formed in the vacuum area, between each blade, between each blade and the inner wall of the mixing reaction chamber, and between each blade and the upper ring and the inner wall of the mixing reaction chamber.

A sealing sleeve 18 is vertically mounted on the end face of the rotation axis of the main shaft 19 for sealing the circumferential gap between the main shaft 19 and the mixing reaction chamber 16; a cooling water circulation channel connected to the external cooling water is provided on the circumference of the sealing sleeve 18 .

A slurry discharge valve 17 is provided at the bottom of the mixing reaction chamber 16, and the slurry discharge valve 17 is connected to the slurry storage tank 21 through a pipeline.

The high-speed variable frequency motor 24 is connected to the frequency converter 25, its front end cover is installed vertically below the frame 27, and the output shaft is connected to the main shaft 19 through the coupling 20.

The cover 10 is provided with a pressure sensor 8 and a temperature sensor 9; the DCS operating system 26 can display the temperature and pressure of the mixing reaction chamber in real time, and can control the switching flow of the chemical liquid pump 2 and the air pump 5 and the high-speed variable frequency motor 24. Rotating speed.

A preparation method of oxygen delignification pulp, which includes the following steps:

Preparation of oxygen delignified pulp:

Installing the pot: Remove the cover 10, and select and install the corresponding hollow mixing rotor 13 according to the pulp consistency characteristics of the pulp to be bleached. That is, the hollow mixing rotor 13 with linear blades is selected for low-consistency and medium-concentration bleaching, and the spiral type is selected for high-concentration bleaching. The hollow mixing rotor 13 of the blade; add absolutely dry slurry, install the cover 10, insert the aeration tube 14 into the center of the hollow mixing rotor 13, and use the end cover bolts 7 to securely seal the cover 10 and the mixing reaction chamber 16;

Adjust the slurry concentration: turn on the chemical liquid pump 2, pump the dilution water through the liquid inlet pipe 1 and the aeration pipe 14, turn on the frequency converter 25, set the frequency, use a rotation speed of 800 to 1500r/min to mix and adjust the concentration, and adjust the mixing reaction The slurry to be bleached in chamber 16 is medium consistency 10% to 14% or high consistency 25% to 30%;

Alkali pretreatment: medium-concentration bleaching, turn on the liquid pump 2, pump in the dosage of 2.0% to 3.0% NaOH, 0.4% to 0.6% MgSO ₄ , 0.4% to 0.6 through the liquid inlet pipe 1 and the aeration pipe 14 % H ₂ O ₂ ; or high-concentration bleaching, pump in the dosage of 2.0% to 6.0% NaOH and 0.3% to 0.6% MgSO ₄ ; turn on the frequency converter 25 and use a rotation speed of 800 to 1500r/min to mix evenly;

Oxygen bleaching: Turn on the heater 15, heat the slurry in the mixing reaction chamber 16 to 90°C, enter the constant temperature mode, turn on the air pump 5, pump the oxygen into the mixing reaction chamber 16 to a pressure of 0.5~0.7MPa, turn on the frequency conversion Device 25 uses a rotation speed of 800 to 1500 r/min to perform a mixed oxygen delignification reaction. The reaction time for medium-concentration bleaching is 60 minutes, and the reaction time for high-concentration bleaching is 30 minutes;

Unloading: When the reaction time is over, close the air pump 5, stop the oxygen intake, close the heater 15, close the frequency converter 25 and the high-speed variable frequency motor 24, open the exhaust valve 11, and deflate, until the pressure in the mixing reaction chamber 16 is At zero, open the chemical liquid pump 2 to pump in dilution water for washing and unloading, open the slurry discharge valve 17, and collect the bleached slurry in the slurry storage tank 21.

A preparation method for ozone bleached pulp, which includes the following steps:

Preparation of ozone bleached pulp:

Installing the pot: Remove the cover 10, and select and install the corresponding hollow mixing rotor 13 according to the pulp consistency characteristics of the pulp to be bleached. That is, the hollow mixing rotor 13 with linear blades is selected for low-consistency and medium-concentration bleaching, and the spiral type is selected for high-concentration bleaching. The hollow mixing rotor 13 of the blade; add absolutely dry slurry, install the cover 10, insert the aeration tube 14 into the center of the hollow mixing rotor 13, and use the end cover bolts 7 to securely seal the cover 10 and the mixing reaction chamber 16;

Adjust the slurry concentration: turn on the chemical liquid pump 2, pump dilution water through the liquid inlet pipe 1 and the aeration pipe 14, turn on the frequency converter 25, mix and adjust the concentration at a speed of 800~1500r/min, and adjust the slurry to be bleached in the reaction chamber to medium Concentrated 10% to 14% or high concentrated 30% to 35%;

Acid pretreatment: Turn on the chemical liquid pump 2, pump in the acid liquid through the liquid inlet pipe 1 and the aeration pipe 14, turn on the frequency converter 25, use a rotation speed of 800~1500r/min, mix evenly, and adjust the pH of the slurry to 2; turn on The heater 15 heats the slurry in the mixing reaction chamber 16 to the corresponding temperature of 40°C, enters the constant temperature mode, turns on the frequency converter 25, uses a medium and low speed of 800 to 1500r/min, and continuously mixes and stirs. The acid pretreatment time is 30 minutes;

Protective agent pretreatment: Turn on the chemical liquid pump 2, pump in organic solvents such as ethylene glycol, ethanol, methanol or dioxane through the liquid inlet pipe 1 and the aeration pipe 14, turn on the frequency converter 25, and use a rotation speed of 800~1500r /min, mix evenly;

Ozone bleaching: Turn on the heater 15 to heat the slurry in the mixing reaction chamber 16 to the required temperature and enter the constant temperature mode, or turn off the heater 15 to perform conventional room temperature ozone bleaching; the exhaust valve 11 above the cover 10 remains open. , turn on the air pump 5, pump in ozone, the concentration is 180mg/L, the flow rate is 4L/min, the inlet pressure is 0.2~0.4MPa, at the same time turn on the frequency converter 25, use a medium to high speed of 1500~3000r/min to perform mixed ozone bleaching reaction, the ozone introduction and mixing time is 5 minutes. After the mixing reaction is completed, close the air pump 5, close the air inlet valve 6, close the frequency converter 25, and the unreacted ozone passes through the exhaust valve 11, the exhaust ozone concentration detector 22, and the ozone exhaust gas Treatment device 23; or close the exhaust valve 11, open the air pump 5, pump in ozone, the concentration is 180mg/L, the flow rate is 4L/min, the air inlet pressure is 0.2~0.4MPa, and the reaction chamber pressure is 0.8~1.2MPa, Turn off the ozone pump 5 and turn on the frequency converter 25 at the same time. Use a medium to high speed of 1500 to 3000 r/min to perform a mixed ozone bleaching reaction. The mixing reaction time is 5 minutes. After the mixing reaction is completed, close the frequency converter 25 and open the exhaust valve 11. The reacted ozone passes through the tail gas ozone concentration detector 22 and the ozone tail gas treatment device 23. When the reaction chamber pressure drops to zero, nitrogen can be pumped in to replace the unreacted ozone in the mixing reaction chamber 16;

Unloading: Open the chemical liquid pump 2 to pump in dilution water to wash the pulp and unload the pulp, open the pulp discharge valve 17, and collect the bleached pulp in the pulp storage tank 21.

A method for preparing oxygen pressurized ozone bleached pulp, which includes the following steps:

Preparation of oxygen pressurized ozone bleached pulp:

Installing the pot: Remove the cover 10, and select and install the corresponding hollow mixing rotor 13 according to the pulp consistency characteristics of the pulp to be bleached. Select the hollow mixing rotor 13 with linear blades for low-consistency and medium-concentration bleaching, and select spiral blades for high-concentration bleaching. The hollow mixing rotor 13; add absolutely dry slurry, install the cover 10, insert the aeration tube 14 into the center of the hollow mixing rotor 13, and use the end cover bolts 7 to tightly seal the cover 10 and the mixing reaction chamber 16;

Adjust the slurry concentration: turn on the chemical liquid pump 2, pump in dilution water through the liquid inlet pipe 1 and the aeration pipe 14, turn on the frequency converter 25, use a medium and low speed of 800~1500r/min, mix and adjust the concentration, and adjust the mixing reaction chamber 16 The internal slurry to be bleached is medium consistency 10% to 14% or high consistency 30% to 35%;

Acid pretreatment: Turn on the chemical liquid pump 2, pump in the acid liquid through the liquid inlet pipe 1 and the aeration pipe 14, turn on the frequency converter 25, use a medium-low speed of 800 to 1500r/min to mix evenly, and adjust the pH of the slurry to 2; Turn on the heater 15 to raise the temperature of the slurry in the mixing reaction chamber 16 to 40°C, enter the constant temperature mode, turn on the frequency converter 25, use a medium and low speed of 800 to 1500r/min, continuously mix and stir, and the acid pretreatment time is 30 minutes;

Protective agent pretreatment: Turn on the chemical liquid pump 2, pump in organic solvents such as ethylene glycol, ethanol, methanol or dioxane through the liquid inlet pipe 1 and the aeration pipe 14, turn on the frequency converter 25, and use a medium-low speed of 800 -1500r/min, mix evenly;

Oxygen pressurized ozone bleaching: turn on the heater 15 to heat the slurry in the mixing reaction chamber 16 to the required temperature and enter the constant temperature mode, or turn off the heater 15 to perform conventional room temperature ozone bleaching; close the exhaust valve 11 and open The air pump 5 pumps in ozone with a concentration of 180mg/L, a flow rate of 4L/min, and an air inlet pressure of 0.2~0.4MPa. When the pressure in the mixing reaction chamber 16 reaches a pressure of 0.8~1.2MPa, stop the ozone air intake; then turn on the air pump 5. Enter oxygen until the pressure in the mixing reaction chamber 16 is 1.5MPa. Turn off the air pump 5 and turn on the frequency converter 25 at the same time. Use a medium to high speed of 1500 to 3000r/min to perform a mixed ozone delignification reaction. The mixing reaction time is 5 minutes and the mixing reaction is completed. Finally, close the frequency converter 25 and open the exhaust valve 11. The unreacted ozone passes through the tail gas ozone concentration detector 22 and the ozone tail gas treatment device 23. When the pressure of the mixing reaction chamber 16 drops to zero, pump nitrogen into the mixing reaction chamber. Unreacted ozone is replaced within 16 days;

Unloading: Open the chemical liquid pump 2 to pump in dilution water to wash the pulp and unload the pulp, open the pulp discharge valve 17, and collect the bleached pulp in the pulp storage tank 21.

Compared with the existing technology, the present invention has the following advantages and effects:

The experimental device of the present invention for oxygen-based high-efficiency cleaning and bleaching of paper pulp uses a variable frequency motor to drive a hollow rotor through a main shaft and a mechanical seal for high-speed mixing, so that the medium-consistency slurry in the mixing reaction chamber achieves a highly turbulent fluidized state. At this time, the The mass transfer process of the oxygen-based gaseous bleach is turbulent diffusion, strong shearing and high-speed pulsation, which can accelerate mixing and reaction; the high-pressure oxygen-based gaseous bleach fed into the hollow position of the hollow mixing rotor has a certain initial speed and pressure, and the impact is When it enters the fluidized medium-consistency pulp, it will produce strong convection, accelerating the mass transfer between different mixing speed areas, making the mixing and mass transfer in each mixing area consistent, and making the bleaching effect more uniform.

The experimental device of the present invention can realize high-intensity turbulence and high-efficiency mixing of medium-consistency paper pulp under laboratory conditions. The mass transfer process is mainly turbulent diffusion and convection diffusion. Compared with the static or low-speed mixing of existing devices and technologies, It is molecular diffusion, and the mass transfer efficiency is very obvious. In addition, since the water in the fiber cell cavity and the water adsorbed on the cell wall in the medium-to-high consistency slurry hinder the direct contact between the gaseous bleach and the fiber, high-intensity shearing and the local strong velocity generated must be used. Pulsation to weaken the obstructive effect of this part of water, so the experimental device of the present invention can reduce the obstructive effect of water on the gaseous bleach through high-strength turbulence and high-speed mixing.

Compared with the existing technology, the present invention adopts a combination of ozone medium-concentration mixer and reactor, which has a compact structure and reasonable design. It adopts a lower-mounted motor and uses a mechanical sealing sleeve with a cooling water channel to take away the high-speed rotation generated At the same time, it realizes the high-speed rotation and mixing under laboratory conditions, and at the same time, the oxygen gaseous bleach is introduced into the seal, which solves the problem that highly corrosive ozone can easily cause the aging and failure of rubber sealing materials, leading to leakage of liquid and material. .

According to the characteristics of different pulp concentrations to be bleached, the present invention designs and adopts replaceable mixing rotors of different types. Applying sufficient shear stress to the medium-consistency pulp can disperse the fiber network and put the medium-consistency pulp in a completely turbulent state. The design uses a hollow linear rotor, which can cause strong turbulence, convection and diffusion between the pulp and the gaseous bleaching agent. and molecular diffusion; for high-consistency pulp with only a small amount of free water and obvious viscoelasticity, a hollow spiral rotor is designed and used, using a method of combining dispersion and high shear. The spiral blades make the high-consistency pulp easy to evacuate and have a higher The large surface area allows the gaseous bleaching agent to fully contact the fiber. High-speed mixing can produce high shearing effect on the slurry and promote efficient reaction. In addition, compared with existing devices and technologies, due to the centrifugal force of high-speed rotation, a vacuum area is easily formed in the center of the hollow mixing rotor, which makes it easier for the gaseous bleach to enter. The centrifugal force also keeps the slurry away from the center of the rotor. The aeration tube will not be clogged.

The device of the present invention is simple and convenient to adjust the pulp consistency, and can be widely used in the bleaching of medium- and high-consistency pulps, and can also be used in experimental research on the bleaching of low-consistency pulps. However, in industrial applications, due to the low concentration, there are problems such as high water consumption and energy consumption. Problems such as high consumption and heavy pollution will not be further elaborated in the present invention. The device of the invention has a reasonable structure, is easy to use, has a high degree of automation, can accurately control the consumption of chemical liquid and oxygen and ozone, and has a simple and efficient process for preparing bleached pulp.

The preparation method of oxygen-based high-efficiency clean bleached pulp of the present invention is widely applicable to oxygen bleaching or ozone bleaching of chemical pulp of any raw material. All oxygen-containing bleaching agents are used, and the final products of the chemical reaction decomposition are oxygen and water, eliminating the need for bleached pulp. There are no residues of harmful substances in the pulp; the bleached pulp prepared by the invention has higher whiteness, is more uniform and is less likely to return to yellow.

The preparation method of oxygen-based high-efficiency clean bleached pulp of the present invention adopts oxygen delignification (also known as oxygen bleaching), which is hydrogen peroxide-enhanced oxygen delignification. It combines the advantages of alkali oxygen bleaching and hydrogen peroxide bleaching. Oxygen delignification , fragments lignin and degrades lignin into water-soluble and alkali-soluble fragments. Hydrogen peroxide can not only reduce and eliminate the chromogenic groups of lignin, but also break down lignin to dissolve it, significantly improving the bleaching effect. In addition, oxygen delignification has a higher delignification rate at higher oxygen pressure and higher temperature. Adding MgSO ₄ can effectively protect the degradation of carbohydrates in the pulp, improve the selectivity of oxygen delignification, and make oxygen delignification more efficient. Pulp viscosity and strength are significantly improved.

The preparation method of oxygen-based high-efficiency clean bleached pulp of the present invention adopts ozone bleaching and oxygen pressurized ozone bleaching, and utilizes the strong oxidizing property of ozone to destroy the aromatic ring structure of lignin into a muconic acid-type structure, resulting in higher delignification. The efficiency can greatly improve the whiteness of pulp. Oxygen pressurized ozone bleaching can combine the advantages of oxygen bleaching and ozone bleaching. Under higher oxygen pressure, it can increase the solubility of oxygen and ozone and strengthen mass transfer, significantly improving the lignin removal rate of pulp. Through acid pretreatment and the addition of protective agents, transition metal ions in the slurry can be effectively removed, as well as reducing the degradation of carbohydrates, increasing the stability and solubility of ozone, and improving the delignification selectivity of ozone.

The preparation method of oxygen-based high-efficiency clean bleached pulp of the present invention can significantly improve the subsequent bleachability and high whiteness stability of the pulp, and can greatly reduce and replace harmful and high-cost chemicals in the subsequent bleaching section, such as chlorine dioxide. and hydrogen peroxide, thereby reducing the pollution load in the bleaching section. It has the advantages of cleanliness, low bleaching cost, and excellent pulp quality.

Description of the drawings

Figure 1 is a schematic structural diagram of the present invention.

Figure 2 is a schematic structural diagram of a linear double-blade hollow mixing rotor.

Figure 3 is a side view of the linear double-blade hollow mixing rotor structure.

Figure 4 is a schematic structural diagram along A-A in Figure 3.

Figure 5 is a schematic structural diagram of a linear three-blade hollow mixing rotor.

Figure 6 is a side view of the linear three-blade hollow mixing rotor structure.

FIG. 7 is a schematic structural diagram along A-A in FIG. 6 .

Figure 8 is a schematic structural diagram of a spiral blade hollow mixing rotor.

Figure 9 is a side view of the spiral blade hollow mixing rotor structure.

Figure 10 is a schematic structural diagram along A-A in Figure 9 .

Detailed ways

The present invention will be further described in detail below with reference to specific embodiments.

Example

As shown in Figure 1-10. The invention discloses an oxygen-based high-efficiency cleaning and bleaching experimental device for paper pulp, which includes a mixing reaction chamber 16 with a cover 10 located on a frame 27, a high-speed variable frequency motor 24, and a DCS operating system 26;

A cover 10 is provided above the mixing reaction chamber 16, a heater 15 is installed on the outer wall of the mixing reaction chamber 16, and a hollow mixing rotor 13 is provided inside the mixing reaction chamber 16;

An aeration pipe 14 with a porous array is provided below the center of the cover 10 and can be inserted into the center of the hollow mixing rotor 13; the outer port of the aeration pipe 14 is connected to the liquid inlet valve 3 and the liquid pump 2 through a three-way interface. , liquid inlet pipe 1 and air inlet valve 6, air pump 5, air inlet pipe 4;

The liquid inlet pipe 1 is made of duplex stainless steel, and the liquid pump 2 is a duplex stainless steel magnetic pump.

The air inlet pipe 4 is made of polytetrafluoroethylene, and the air pump 5 is a special ozone compressor, which is pressurized and corrosion-resistant, and can meet the requirements for transporting oxygen and ozone.

The cover 10 is detachable and made of highly transparent and high-strength organic glass.

The heater 15 is covered on the outer wall of the mixing reaction chamber 16 and may be equipped with a temperature control device. The heating element is a corrosion-resistant nickel complex alloy wire, and the surface of the electric heating plate is treated with polytetrafluoroethylene for anti-corrosion treatment.

The tail gas ozone concentration detector 22 is an online detector with a detection range of 0-200g/m ³ , adopts an integrated split layer light pool structure, and has RS-485 signal output.

The (rotating) spindle 19 is made of No. 45 steel.

An exhaust valve 11 is provided above the cover 10, and the exhaust valve 11 is connected in sequence to an exhaust ozone concentration detector 22 and an ozone exhaust treatment device 23 through an exhaust pipe 12;

The hollow mixing rotor 13 is connected to the shaft end of the main shaft 19 of the high-speed variable frequency motor 24 at the bottom of the mixing reaction chamber 16 through bolts 28; the blades of the hollow mixing rotor 13 are a plurality of linear blades (2- 3 blades) or multiple spiral blades (2-3 blades) symmetrically distributed in a hollow structure.

The two ends of the blades of the hollow mixing rotor 13 are respectively fixed on two coaxially distributed rings up and down, and the lower ring is connected to the shaft end of the main shaft 19 at the bottom of the mixing reaction chamber 16 through bolts 28; a porous array is provided The aeration tube 14 extends into the inner center of the hollow mixing rotor 13 through the upper ring; when the hollow mixing rotor 13 rotates, a vacuum area is formed at its center; under the disturbance of the blades, the fluid in the mixing reaction chamber 16 is Convection is formed in the vacuum area, between each blade, between each blade and the inner wall of the mixing reaction chamber, and between each blade and the upper ring and the inner wall of the mixing reaction chamber.

A sealing sleeve 18 is vertically mounted on the end face of the rotation axis of the main shaft 19 for sealing the circumferential gap between the main shaft 19 and the mixing reaction chamber 16; a cooling water circulation channel connected to the external cooling water is provided on the circumference of the sealing sleeve 18 , to cool the heat generated by friction with the spindle when it rotates at high speed.

A slurry discharge valve 17 is provided at the bottom of the mixing reaction chamber 16, and the slurry discharge valve 17 is connected to the slurry storage tank 21 through a pipeline.

The high-speed variable frequency motor 24 is connected to the frequency converter 25, its front end cover is installed vertically below the frame 27, and the output shaft is connected to the main shaft 19 through the coupling 20.

The cover 10 is provided with a pressure sensor 8 and a temperature sensor 9; the DCS operating system 26 can display the temperature and pressure of the mixing reaction chamber in real time, and can control the switching flow of the chemical liquid pump 2 and the air pump 5 and the high-speed variable frequency motor 24. Rotating speed.

The method for preparing oxygen-based high-efficiency clean and bleached pulp using the experimental device of the present invention is as follows:

Example 1

Preparation of oxygen delignified pulp:

(1) Install the pot: Remove the cover 10, and install the corresponding hollow mixing rotor 13 according to the pulp consistency characteristics of the pulp to be bleached; select the hollow mixing rotor 13 with linear blades for low- and medium-concentration bleaching, and select the hollow mixing rotor 13 for high-concentration bleaching. Hollow mixing rotor 13 with spiral blades; add an appropriate amount of absolutely dry slurry, install the cover 10, insert the aeration tube 14 into the center of the hollow mixing rotor 13, and use the end cover bolts 7 to tighten the cover 10 and the mixing reaction chamber 16 Solid seal.

(2) Adjust the slurry concentration: turn on the chemical liquid pump 2, pump in the corresponding volume of dilution water through the liquid inlet pipe 1 and the aeration pipe 14, turn on the frequency converter 25, use a medium and low speed of 800~1500r/min, mix and adjust the concentration , adjust the slurry to be bleached in the reaction chamber to medium consistency 10% or high consistency 25%.

(3) Alkali pretreatment: Medium-concentration bleaching: Turn on the liquid pump 2, and pump in the dosage of 2.0% NaOH, 0.4% MgSO ₄ and 0.4% H ₂ O ₂ through the liquid inlet pipe 1 and the aeration pipe 14. ; Or high-concentration bleaching, pump in the dosage of 2.0% NaOH and 0.3% MgSO ₄ ; turn on the frequency converter 25, use a low speed of 800r/min, and mix evenly.

(4) Oxygen bleaching: Turn on the heater 15 to raise the temperature of the slurry in the reaction chamber to 90°C, enter the constant temperature mode, turn on the air pump 5, pump in a corresponding volume of oxygen until the pressure in the reaction chamber is 0.5MPa, turn on the frequency converter 25, and use The low rotation speed is 800r/min, and the mixed oxygen delignification reaction is carried out. The medium-concentration bleaching reaction time is 60 minutes, and the high-concentration bleaching reaction time is 30 minutes.

(5) Unloading: When the reaction time is over, turn off the air pump 5, stop the oxygen intake, turn off the heater 15, turn off the frequency converter 25 and the motor 24, open the exhaust valve 11, and deflate, until the pressure in the reaction chamber reaches zero, Turn on the chemical liquid pump 2 to pump in dilution water for washing and unloading, open the discharge valve 17, and collect the bleached slurry in the stock tank 21.

Preparation of ozone bleached pulp:

(1) Installing the pot: Remove the cover 10 and install the corresponding mixing rotor 13 according to the pulp consistency characteristics of the pulp to be bleached. For low- and medium-concentration bleaching, choose a hollow mixing rotor 13 with linear blades. For high-concentration bleaching, choose a spiral. Type blade hollow mixing rotor 13; add an appropriate amount of absolutely dry slurry, install the cover 10, insert the aeration tube 14 into the center of the hollow mixing rotor 13, and use the end cover bolts 7 to fasten the cover 10 and the mixing reaction chamber 16 seal.

(2) Adjust the slurry concentration: turn on the chemical liquid pump 2, pump in the corresponding volume of dilution water through the liquid inlet pipe 1 and the aeration pipe 14, turn on the frequency converter 25, use a low speed of 800r/min, mix and thicken, and adjust the mixing The slurry to be bleached in the reaction chamber 16 is medium consistency 10% or high consistency 30%.

(3) Turn on the chemical liquid pump 2, pump an appropriate amount of acid liquid through the liquid inlet pipe 1 and the aeration pipe 14, turn on the frequency converter 25, use a medium-low speed of 800, mix evenly, and adjust the pH of the slurry to 2. Turn on the heater to heat the slurry in the mixing reaction chamber 16 to the corresponding temperature of 40°C, enter the constant temperature mode, turn on the frequency converter 25, use a low speed of 800r/min, continuously mix and stir, and the acid pretreatment time is 30 minutes.

(4) Protective agent pretreatment: Turn on the chemical liquid pump 2, pump in an appropriate amount of organic solvents such as ethylene glycol, ethanol, methanol or dioxane through the liquid inlet pipe 1 and aeration pipe 14, turn on the frequency converter 25, Use low speed 800r/min to mix evenly.

(5) Ozone bleaching: Turn on the heater 15 to heat the slurry in the mixing reaction chamber 16 to the required temperature and enter the constant temperature mode, or turn off the heater 15 to perform conventional room temperature ozone bleaching. The exhaust valve 11 above the cover 10 remains open, the air pump 5 is turned on, and a corresponding volume of ozone is pumped in. The concentration is 180mg/L, the flow rate is 4L/min, the air inlet pressure is 0.2MPa, and the frequency converter 25 is turned on at the same time. The rotating speed is 1500r/min, and the mixed ozone delignification reaction is carried out. The ozone introduction and mixing time is 5 minutes. After the mixing reaction is completed, close the air pump 5, the air inlet valve 6, and the frequency converter 25. The unreacted ozone passes through the exhaust valve. 11. Exhaust gas ozone concentration detector 22, ozone exhaust gas treatment device 23; or close the exhaust valve 11, open the air pump 5, pump in the corresponding volume of ozone, the concentration is 180mg/L, the flow rate is 4L/min, and the inlet pressure is 0.2 MPa, when the pressure in the mixing reaction chamber 16 is 0.8MPa, turn off the ozone pump 5 and turn on the frequency converter 25 at the same time. Use a medium speed of 1500r/min to perform a mixed ozone delignification reaction. The mixing reaction time is 5 minutes. After the mixing reaction is completed, Close the frequency converter 25 and open the exhaust valve 11. The unreacted ozone passes through the tail gas ozone concentration detector 22 and the ozone tail gas treatment device 23. When the pressure of the mixing reaction chamber 16 drops to zero, an appropriate amount of nitrogen can be pumped into the mixing reaction chamber. Unreacted ozone is replaced within 16 seconds.

(6) Unloading: Open the chemical liquid pump 2 to pump in dilution water to wash and unload the pulp, open the pulp discharge valve 17, and collect the bleached slurry in the pulp storage tank 21.

Preparation of oxygen pressurized ozone bleached pulp:

(1) Install the pot and remove the cover 10. Select and install the corresponding hollow mixing rotor 13 according to the pulp consistency characteristics of the pulp to be bleached. Select the hollow mixing rotor 13 with linear blades for low-consistency and medium-concentration bleaching. Select the spiral for high-concentration bleaching. Type blade hollow mixing rotor 13; add an appropriate amount of absolutely dry slurry, install the cover 10, insert the aeration tube 14 into the center of the hollow mixing rotor 13, and use the end cover bolts 7 to securely seal the cover 10 and the reaction chamber 16 .

(2) Adjust the slurry concentration: turn on the chemical liquid pump 2, pump the corresponding volume of dilution water through the liquid inlet pipe 1 and the aeration pipe 14, turn on the frequency converter 25, use a low speed of 800r/min, mix and adjust the concentration, and adjust the reaction The indoor slurry to be bleached is medium consistency 10% or high consistency 30%.

(3) Acid pretreatment: Turn on the chemical liquid pump 2, pump an appropriate amount of acid liquid through the liquid inlet pipe 1 and the aeration pipe 14, turn on the frequency converter 25, use a low speed of 800r/min, mix evenly, and adjust the pH of the slurry is 2. Turn on the heater 15 to raise the temperature of the slurry in the reaction chamber to the corresponding temperature of 40°C, enter the constant temperature mode, turn on the frequency converter 25, use a low speed of 800r/min, continuously mix and stir, and the acid pretreatment time is 30 minutes.

(4) Protective agent pretreatment: Turn on the chemical liquid pump 2, pump in an appropriate amount of organic solvents such as ethylene glycol, ethanol, methanol or dioxane through the liquid inlet pipe 1 and aeration pipe 14, turn on the frequency converter 25, Use low speed 800r/min to mix evenly.

(5) Oxygen pressurized ozone bleaching: Turn on the heater 15 to heat the slurry in the mixing reaction chamber 16 to the required temperature, and enter the constant temperature mode, or turn off the heater 15 to perform conventional room temperature ozone bleaching. Close the exhaust valve 11, open the air pump 5, pump in the corresponding volume of ozone, the concentration is 180mg/L, the flow rate is 4L/min, the air inlet pressure is 0.2MPa, until the reaction chamber pressure is 0.8MPa, stop the ozone air intake. Then open the air pump 5 to pump in oxygen until the pressure in the reaction chamber is 1.5MPa. Close the air pump 5 and open the frequency converter 25 at the same time. Use a medium speed of 1500r/min to perform a mixed ozone delignification reaction. The mixing reaction time is 5 minutes. The mixing reaction After completion, close the frequency converter 25 and open the exhaust valve 11. The unreacted ozone passes through the tail gas ozone concentration detector 22 and the ozone tail gas treatment device 23. When the pressure of the mixing reaction chamber 16 drops to zero, pump in an appropriate amount of nitrogen to mix. Unreacted ozone in the reaction chamber 16 is replaced.

(6) Unloading: Open the chemical liquid pump 2 to pump in dilution water to wash and unload the pulp, open the pulp discharge valve 17, and collect the bleached slurry in the pulp storage tank 21.

Example 2

Preparation of oxygen delignified pulp:

(1) Installing the pot: Remove the cover 10, and select and install the corresponding mixing rotor 13 according to the pulp consistency characteristics of the pulp to be bleached. Select a linear hollow rotor for low- and medium-concentration bleaching, and a spiral hollow rotor for high-concentration bleaching; Add an appropriate amount of absolutely dry slurry, install the cover 10, insert the aeration tube 14 into the center of the rotor 13, and use the end cover bolts 7 to tightly seal the cover 10 and the mixing reaction chamber 16.

(2) Adjust the slurry concentration: turn on the chemical liquid pump 2, pump the corresponding volume of dilution water through the liquid inlet pipe 1 and the aeration pipe 14, turn on the frequency converter 25, use a medium speed of 1500r/min, mix and adjust the concentration, and adjust the mixing The slurry to be bleached in the reaction chamber 16 is medium consistency 14% or high consistency 30%.

(3) Alkali pretreatment: medium-concentration bleaching: turn on the chemical solution pump 2, and pump in the dosage of 3.0% NaOH, 0.6% MgSO ₄ and 0.6% H ₂ O ₂ through the liquid inlet pipe 1 and the aeration pipe 14 ; Or high-concentration bleaching, pump in the dosage of 6.0% NaOH and 0.6% MgSO ₄ ; turn on the frequency converter 25, use a medium speed of 1500r/min, and mix evenly.

(4) Oxygen bleaching: Turn on the heater 15 to heat the slurry in the mixing reaction chamber 16 to 90°C, enter the constant temperature mode, turn on the air pump 5, pump in a corresponding volume of oxygen until the pressure in the reaction chamber is 0.7MPa, and turn on the frequency converter 25. Use a medium rotation speed of 1500r/min to perform a mixed oxygen delignification reaction. The reaction time for medium-concentration bleaching is 60 minutes, and the reaction time for high-concentration bleaching is 30 minutes.

(5) Unloading: When the reaction time is over, turn off the air pump 5, stop the oxygen intake, turn off the heater 15, turn off the frequency converter 25 and the motor 24, open the exhaust valve 11, and deflate, until the pressure of the mixing reaction chamber 16 is At zero, open the chemical liquid pump 2 to pump in dilution water for washing and unloading, open the slurry discharge valve 17, and collect the bleached slurry in the slurry storage tank 21.

Preparation of ozone bleached pulp:

(1) Installing the pot: Remove the cover 10 and install the corresponding mixing rotor 13 according to the pulp consistency characteristics of the pulp to be bleached. For low- and medium-concentration bleaching, choose a hollow mixing rotor 13 with linear blades. For high-concentration bleaching, choose a spiral. Type blade hollow mixing rotor 13; add an appropriate amount of absolutely dry slurry, install the cover 10, insert the aeration tube 14 into the center of the hollow mixing rotor 13, and use the end cover bolts 7 to fasten the cover 10 and the mixing reaction chamber 16 seal.

(2) Adjust the slurry concentration: turn on the chemical liquid pump 2, pump the corresponding volume of dilution water through the liquid inlet pipe 1 and the aeration pipe 14, turn on the frequency converter 25, use a medium speed of 1500r/min, mix and adjust the concentration, and adjust the mixing The slurry to be bleached in the reaction chamber 16 is medium consistency 14% or high consistency 35%.

(3) Acid pretreatment: Turn on the chemical liquid pump 2, pump an appropriate amount of acid liquid through the liquid inlet pipe 1 and the aeration pipe 14, turn on the frequency converter 25, use a medium speed of 1500r/min, mix evenly, and adjust the pH of the slurry is 2. Turn on the heater 15 to raise the temperature of the slurry in the mixing reaction chamber 16 to the corresponding temperature of 40°C, enter the constant temperature mode, turn on the frequency converter 25, use a medium speed of 1500r/min, continuously mix and stir, and the acid pretreatment time is 30 minutes.

(4) Protective agent pretreatment: Turn on the chemical liquid pump 2, pump in an appropriate amount of organic solvents such as ethylene glycol, ethanol, methanol or dioxane through the liquid inlet pipe 1 and aeration pipe 14, turn on the frequency converter 25, Use a medium speed of 1500r/min to mix evenly.

(5) Ozone bleaching: Turn on the heater 15 to heat the slurry in the mixing reaction chamber 16 to the required temperature and enter the constant temperature mode, or turn off the heater 15 to perform conventional room temperature ozone bleaching. The exhaust valve 11 above the cover 10 remains open, the air pump 5 is turned on, and a corresponding volume of ozone is pumped in. The concentration is 180mg/L, the flow rate is 4L/min, the air inlet pressure is 0.4MPa, and the frequency converter 25 is turned on at the same time. The rotating speed is 3000r/min, and the mixed ozone delignification reaction is carried out. The ozone introduction and mixing time is 5 minutes. After the mixing reaction is completed, close the air pump 5, the air inlet valve 6, close the frequency converter 25, and the unreacted ozone passes through the exhaust valve. 11. Exhaust gas ozone concentration detector 22, ozone exhaust gas treatment device 23; or close the exhaust valve 11, open the air pump 5, pump in the corresponding volume of ozone, the concentration is 180mg/L, the flow rate is 4L/min, and the inlet pressure is 0.4 MPa, the pressure in the mixing reaction chamber 16 is 1.2MPa, turn off the ozone pump 5, and turn on the frequency converter 25 at the same time. Use a high speed of 3000r/min to perform a mixed ozone delignification reaction. The mixing reaction time is 5 minutes. After the mixing reaction is completed, Close the frequency converter 25 and open the exhaust valve 11. The unreacted ozone passes through the tail gas ozone concentration detector 22 and the ozone tail gas treatment device 23. When the pressure in the reaction chamber drops to zero, an appropriate amount of nitrogen can be pumped in to remove the unreacted ozone in the reaction chamber. Ozone is displaced.

(6) Unloading: Open the chemical liquid pump 2 to pump in dilution water to wash and unload the pulp, open the pulp discharge valve 17, and collect the bleached slurry in the pulp storage tank 21.

Preparation of oxygen pressurized ozone bleached pulp:

(1) Installing the pot: Remove the cover 10 and install the corresponding mixing rotor 13 according to the pulp consistency characteristics of the pulp to be bleached. For low- and medium-concentration bleaching, choose a hollow mixing rotor 13 with linear blades. For high-concentration bleaching, choose a spiral. The hollow mixing rotor 13 of the type blade; add an appropriate amount of absolutely dry slurry, install the cover 10, insert the aeration tube 14 into the center of the empty mixing rotor 13, and use the end cover bolts 7 to tightly seal the cover 10 and the reaction chamber 16 .

(2) Adjust the slurry concentration: turn on the chemical liquid pump 2, pump in the corresponding volume of dilution water through the liquid inlet pipe 1 and the aeration pipe 14, turn on the frequency converter 25, use a medium speed of 1500r/min, mix and adjust the concentration, and adjust the reaction The indoor slurry to be bleached is medium consistency 14% or high consistency 35%.

(3) Acid pretreatment: Turn on the chemical liquid pump 2, pump an appropriate amount of acid liquid through the liquid inlet pipe 1 and the aeration pipe 14, turn on the frequency converter 25, use a medium speed of 1500r/min, mix evenly, and adjust the pH of the slurry is 2. Turn on the heater 15 to raise the temperature of the slurry in the mixing reaction chamber 16 to the corresponding temperature of 40°C, enter the constant temperature mode, turn on the frequency converter 25, use a medium-low speed of 1500r/min, continuously mix and stir, and the acid pretreatment time is 30 minutes.

(4) Protective agent pretreatment: Turn on the chemical liquid pump 2, pump in an appropriate amount of organic solvents such as ethylene glycol, ethanol, methanol or dioxane through the liquid inlet pipe 1 and aeration pipe 14, turn on the frequency converter 25, Use a medium speed of 1500r/min to mix evenly.

(5) Oxygen pressurized ozone bleaching: Turn on the heater 15 to heat the slurry in the mixing reaction chamber 16 to the required temperature, and enter the constant temperature mode, or turn off the heater 15 to perform conventional room temperature ozone bleaching. Close the exhaust valve 11, open the air pump 5, pump in the corresponding volume of ozone, the concentration is 180mg/L, the flow rate is 4L/min, the air inlet pressure is 0.4MPa, until the pressure of the mixing reaction chamber 16 is 1.2MPa, stop the ozone air inlet . Then open the air pump 5 to pump in oxygen until the pressure in the mixing reaction chamber 16 is 1.5MPa. Close the air pump 5 and open the frequency converter 25 at the same time. Use a high speed of 3000r/min to perform a mixed ozone delignification reaction. The mixing reaction time is 5 minutes. After the mixing reaction is completed, close the frequency converter 25 and open the exhaust valve 11. The unreacted ozone passes through the tail gas ozone concentration detector 22 and the ozone tail gas treatment device 23. When the reaction chamber pressure drops to zero, pump in an appropriate amount of nitrogen to mix. Unreacted ozone in the reaction chamber 16 is replaced.

(6) Unloading: Open the chemical liquid pump 2 to pump in dilution water to wash and unload the pulp, open the pulp discharge valve 17, and collect the bleached slurry in the pulp storage tank 21.

As described above, the present invention can be better implemented.

The implementation of the present invention is not limited to the above-mentioned embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent substitutions and are included in within the protection scope of the present invention.

Claims (4)

1. A method for preparing paper pulp by adopting an oxygen-series high-efficiency clean bleached paper pulp experimental device is characterized in that the device comprises a mixing reaction chamber (16) with a cover body (10), a high-speed variable-frequency motor (24) and a DCS operation system (26) which are arranged on a frame (27),

a cover body (10) is arranged above the mixing reaction chamber (16), a heater (15) is arranged on the outer wall of the mixing reaction chamber (16), and a hollow mixing rotor (13) is arranged in the mixing reaction chamber (16);

an aeration pipe (14) which can be inserted into the center of the hollow mixing rotor (13) and is provided with a porous array is arranged below the center of the cover body (10); the outer port of the aerator pipe (14) is respectively and sequentially communicated with a liquid inlet valve (3), a liquid medicine pump (2), a liquid inlet pipe (1), an air inlet valve (6), an air pump (5) and an air inlet pipe (4) through three-way interfaces;

An exhaust valve (11) is arranged above the cover body (10), the exhaust valve (11) is sequentially connected with an exhaust ozone concentration detector (22) through an exhaust pipe (12), and an ozone exhaust gas treatment device (23);

the hollow mixing rotor (13) is connected to the shaft end of a main shaft (19) of a high-speed variable-frequency motor (24) positioned at the bottom of the mixing reaction chamber (16) through a bolt (28); the blades of the hollow mixing rotor (13) are a plurality of linear blades with hollow structures distributed in parallel and symmetrically or a plurality of spiral blades with hollow structures distributed in symmetrical manner;

two ends of the blades of the hollow mixing rotor (13) are respectively fixed on an upper ring and a lower ring which are coaxially distributed, and the lower ring is connected with the shaft end of a main shaft (19) positioned at the bottom of the mixing reaction chamber (16) through bolts (28); an aeration pipe (14) with a porous array extends into the inner center of the hollow mixing rotor (13) through an upper circular ring; when the hollow mixing rotor (13) rotates, a vacuum area is formed at the central position thereof; under the disturbance of the blades, the fluid in the mixing reaction chamber (16) forms convection among a vacuum area, the blades and the inner wall of the mixing reaction chamber, and the blades, the upper circular ring and the inner wall of the mixing reaction chamber;

the end face of the rotation axis of the main shaft (19) is vertically sleeved with a sealing sleeve (18) for sealing a circumferential gap between the main shaft (19) and the mixing reaction chamber (16); a cooling water circulation flow passage communicated with external cooling water is formed in the circumference of the sealing sleeve (18);

The method for preparing the paper pulp comprises the steps of preparing oxygen delignification paper pulp, preparing ozone bleaching paper pulp and preparing oxygen pressurized ozone bleaching paper pulp;

preparation of oxygen delignified pulp:

loading a pot: the cover body (10) is taken down, and a corresponding hollow mixing rotor (13) is selectively installed according to the pulp consistency characteristics of the pulp to be bleached, namely, a hollow mixing rotor (13) with low-consistency and medium-consistency bleaching selecting linear blades and a hollow mixing rotor (13) with high-consistency bleaching selecting spiral blades; adding absolute dry slurry, mounting a cover body (10), inserting an aeration pipe (14) into the center position of a hollow mixing rotor (13), and fastening and sealing the cover body (10) and a mixing reaction chamber (16) by using an end cover bolt (7);

and (3) adjusting the slurry concentration: starting a liquid medicine pump (2), starting a frequency converter (25) through dilution water pumped by a liquid inlet pipe (1) and an aeration pipe (14), mixing and concentrating at the rotating speed of 800-1500 r/min, and regulating the slurry to be bleached in a mixing reaction chamber (16) to be 10-14% of medium concentration or 25-30% of high concentration;

alkali pretreatment: the method comprises the steps of medium concentration bleaching, starting a liquid medicine pump (2), pumping NaOH with the dosage of 2.0-3.0% and MgSO with the dosage of 0.4-0.6% through a liquid inlet pipe (1) and an aeration pipe (14) ₄ 0.4 to 0.6 percent of H ₂ O ₂ The method comprises the steps of carrying out a first treatment on the surface of the Or high-concentration bleaching, pumping NaOH with the dosage of 2.0-6.0% and MgSO with the dosage of 0.3-0.6% ₄ The method comprises the steps of carrying out a first treatment on the surface of the Starting a frequency converter (25), and uniformly mixing at a rotating speed of 800-1500 r/min;

oxygen bleaching: starting a heater (15) to heat slurry in a mixing reaction chamber (16) to 90 ℃, performing a constant temperature mode, starting an air pump (5), pumping oxygen until the pressure in the mixing reaction chamber (16) is 0.5-0.7 MPa, starting a frequency converter (25), and performing a mixed oxygen delignification reaction at a rotating speed of 800-1500r/min, wherein the medium-concentration bleaching reaction time is 60min, and the high-concentration bleaching reaction time is 30min;

and (3) unloading: after the reaction time is over, closing the air pump (5), stopping oxygen gas inlet, closing the heater (15), closing the frequency converter (25) and the high-speed variable-frequency motor (24), opening the exhaust valve (11), deflating, starting the liquid medicine pump (2) to pump dilution water for pulp washing and discharging when the pressure in the mixed reaction chamber (16) is zero, opening the pulp discharging valve (17), and collecting the bleached pulp in the pulp storage tank (21);

preparation of ozone bleached pulp:

loading a pot: the cover body (10) is taken down, and a corresponding hollow mixing rotor (13) is selectively installed according to the pulp consistency characteristics of the pulp to be bleached, namely, a hollow mixing rotor (13) with low-consistency and medium-consistency bleaching selecting linear blades and a hollow mixing rotor (13) with high-consistency bleaching selecting spiral blades; adding absolute dry slurry, mounting a cover body (10), inserting an aeration pipe (14) into the center position of a hollow mixing rotor (13), and fastening and sealing the cover body (10) and a mixing reaction chamber (16) by using an end cover bolt (7);

And (3) adjusting the slurry concentration: starting a liquid medicine pump (2), pumping dilution water through a liquid inlet pipe (1) and an aeration pipe (14), starting a frequency converter (25), mixing and concentrating at the rotating speed of 800-1500r/min, and regulating the concentration of slurry to be bleached in a reaction chamber to be 10-14% of medium concentration or 30-35% of high concentration;

acid pretreatment: starting a liquid medicine pump (2), pumping acid liquor through a liquid inlet pipe (1) and an aeration pipe (14), starting a frequency converter (25), uniformly mixing at a rotating speed of 800-1500r/min, and regulating the pH value of slurry to be 2; starting a heater (15) to heat the slurry in the mixing reaction chamber (16) to the corresponding temperature of 40 ℃, performing a constant temperature mode, starting a frequency converter (25), and continuously mixing and stirring at a medium and low rotating speed of 800-1500r/min for 30min;

pretreatment of a protective agent: starting a liquid medicine pump (2), pumping an organic solvent such as glycol, ethanol, methanol or dioxane through a liquid inlet pipe (1) and an aeration pipe (14), starting a frequency converter (25), and uniformly mixing at a rotating speed of 800-1500 r/min;

ozone bleaching: starting a heater (15) to heat the slurry in the mixing reaction chamber (16) to a required temperature, performing a constant temperature mode, or closing the heater (15) to perform conventional normal-temperature ozone bleaching; an exhaust valve (11) above a cover body (10) is kept in an open state, an air pump (5) is started, ozone is pumped in, the concentration is 180mg/L, the flow is 4L/min, the air inlet pressure is 0.2-0.4 MPa, a frequency converter (25) is started, a medium-high rotating speed of 1500-3000 r/min is adopted for carrying out a mixed ozone bleaching reaction, the ozone introducing and mixing time is 5min, after the mixing reaction is finished, the air pump (5) is closed, an air inlet valve (6) is closed, the frequency converter (25) is closed, unreacted ozone passes through the exhaust valve (11), a tail gas ozone concentration detector (22) and an ozone tail gas treatment device (23); or closing the exhaust valve (11), opening the air pump (5), pumping ozone with the concentration of 180mg/L, the flow of 4L/min, the air inlet pressure of 0.2-0.4 MPa, the pressure of the reaction chamber of 0.8-1.2 MPa, closing the ozone air pump (5), simultaneously opening the frequency converter (25), carrying out mixed ozone bleaching reaction at the medium-high rotating speed of 1500-3000 r/min, the mixed reaction time of 5min, closing the frequency converter (25) after the mixed reaction is finished, opening the exhaust valve (11), allowing unreacted ozone to pass through the tail gas ozone concentration detector (22) and the ozone tail gas treatment device (23), pumping nitrogen when the pressure of the reaction chamber is reduced to zero, and replacing the unreacted ozone in the mixed reaction chamber (16);

And (3) unloading: the liquid medicine pump (2) is started to pump in dilution water, pulp washing and discharging are carried out, the pulp discharging valve (17) is opened, and the pulp storage tank (21) is used for collecting the bleached pulp;

preparation of oxygen pressurized ozone bleached pulp:

loading a pot: the cover body (10) is taken down, a corresponding hollow mixing rotor (13) is selectively installed according to the pulp consistency characteristics of the pulp to be bleached, the hollow mixing rotor (13) with linear blades is selected for low-consistency and medium-consistency bleaching, and the hollow mixing rotor (13) with spiral blades is selected for high-consistency bleaching; adding absolute dry slurry, mounting a cover body (10), inserting an aeration pipe (14) into the center position of a hollow mixing rotor (13), and fastening and sealing the cover body (10) and a mixing reaction chamber (16) by using an end cover bolt (7);

and (3) adjusting the slurry concentration: starting a liquid medicine pump (2), pumping dilution water through a liquid inlet pipe (1) and an aeration pipe (14), starting a frequency converter (25), adopting a medium-low rotating speed of 800-1500 r/min, mixing and concentrating, and regulating the slurry to be bleached in a mixing reaction chamber (16) to be 10-14% of medium concentration or 30-35% of high concentration;

acid pretreatment: starting a liquid medicine pump (2), pumping acid liquor through a liquid inlet pipe (1) and an aeration pipe (14), starting a frequency converter (25), uniformly mixing at a medium-low rotating speed of 800-1500 r/min, and regulating the pH value of slurry to be 2; starting a heater (15) to heat the slurry in the mixing reaction chamber (16) to 40 ℃, performing a constant temperature mode, starting a frequency converter (25), and continuously mixing and stirring at a medium-low rotating speed of 800-1500 r/min for 30min;

Pretreatment of a protective agent: starting a liquid medicine pump (2), pumping an organic solvent such as glycol, ethanol, methanol or dioxane through a liquid inlet pipe (1) and an aeration pipe (14), starting a frequency converter (25), and uniformly mixing at a medium-low rotating speed of 800-1500 r/min;

oxygen pressurized ozone bleaching: starting a heater (15) to heat the slurry in the mixing reaction chamber (16) to a required temperature, performing a constant temperature mode, or closing the heater (15) to perform conventional normal-temperature ozone bleaching; closing the exhaust valve (11), opening the air pump (5) to pump ozone, wherein the concentration is 180mg/L, the flow is 4L/min, the air inlet pressure is 0.2-0.4 MPa, the pressure in the mixing reaction chamber (16) is 0.8-1.2 MPa, and ozone air inlet is stopped; then the air pump (5) is started to pump oxygen until the pressure of the mixed reaction chamber (16) is 1.5MPa, the air pump (5) is closed, the frequency converter (25) is started at the same time, the mixed ozone delignification reaction is carried out at a medium-high rotating speed of 1500-3000 r/min, the mixed reaction time is 5min, after the mixed reaction is finished, the frequency converter (25) is closed, the exhaust valve (11) is opened, unreacted ozone passes through the tail gas ozone concentration detector (22) and the ozone tail gas treatment device (23), and when the pressure of the mixed reaction chamber (16) is reduced to zero, nitrogen is pumped, and the unreacted ozone in the mixed reaction chamber (16) is replaced;

And (3) unloading: and (3) starting a liquid medicine pump (2) to pump in dilution water, washing and discharging, starting a pulp discharging valve (17), and collecting the bleached pulp in a pulp storage tank (21).

2. The method for preparing paper pulp by adopting the oxygen-based efficient clean bleached paper pulp experimental device according to claim 1, which is characterized in that: the bottom of the mixing reaction chamber (16) is provided with a pulp discharging valve (17), and the pulp discharging valve (17) is connected with a pulp storage tank (21) through a pipeline.

3. The method for preparing paper pulp by adopting the oxygen-based high-efficiency clean bleached paper pulp experimental device as claimed in claim 2, which is characterized in that: the high-speed variable frequency motor (24) is connected with the frequency converter (25), the front end cover of the high-speed variable frequency motor is vertically arranged below the frame (27), and the output shaft is connected with the main shaft (19) through the coupler (20).

4. The method for preparing paper pulp by adopting the oxygen-based high-efficiency clean bleached paper pulp experimental device as claimed in claim 2, which is characterized in that: the cover body (10) is provided with a pressure sensor (8) and a temperature sensor (9); the DCS operation system (26) can display the temperature and the pressure of the mixing reaction chamber in real time, and can control the switching flow of the pharmaceutical liquid pump (2) and the air pump (5) and the rotating speed of the high-speed variable-frequency motor (24).