CN112726256B

CN112726256B - Cavitation device for refining production of reinforced cellulose pulp

Info

Publication number: CN112726256B
Application number: CN202011439434.3A
Authority: CN
Inventors: 陈颂英; 孙逊; 玄晓旭; 丛山昊; 林劲松
Original assignee: Shandong University
Current assignee: Shandong University
Priority date: 2020-12-11
Filing date: 2020-12-11
Publication date: 2022-04-26
Anticipated expiration: 2040-12-11
Also published as: CN112726256A

Abstract

The utility model provides a cavitation device of intensive cellulose pulp refining production, includes the stator, the apparatus further comprises a rotating shaft, rotor and ultrasonic transducer, the pivot includes first pivot and second pivot, the rotor includes first rotor of group and the second rotor of organizing, the stator is airtight barrel, the relative both sides of stator are equipped with feed inlet and discharge gate respectively, it has ultrasonic transducer to distribute on the inner wall of stator, first pivot and second pivot are installed respectively on the relative both sides face of stator, first rotor of group and the second rotor of organizing all set up in the stator and install respectively in first pivot and second pivot, first rotor of group and the second rotor of organizing all distribute the rotor cavitation including the outer peripheral face of each rim plate of two rim plates that separate at least, it has stator cavitation hole to distribute on the inner wall of stator. The invention applies the cavitation technology to the paper pulp refining, has the advantages of simplicity, high efficiency, good utilization rate and the like, not only has the effect of physical stirring, but also accelerates the paper pulp refining process by utilizing the cavitation reaction.

Description

Cavitation device for refining production of reinforced cellulose pulp

Technical Field

The invention relates to a device for strengthening refining production of cellulose pulp by utilizing hydraulic and ultrasonic cavitation technologies, and belongs to the technical field of paper production.

Background

Papermaking comprises the following stages: cellulose production, refining, squeezing dehydration, drying, rolling and other links. In the above-mentioned manufacturing process, refining of cellulose pulp is a key step in obtaining high quality paper. However, this process is slow and expensive to produce and has been lacking in effective techniques and equipment for refining long needles of conifers. Refining techniques include acid hydrolysis, high pressure homogenization, and mechanical processing (milling, ultrasonic cavitation, freeze-crushing), among others. Among them, ultrasonic cavitation has been proven to be an effective pulp refining method, but is limited to refining shorter fibers, and the use of ultrasonic cavitation alone has disadvantages of high energy consumption, inability to continuously treat a large amount of pulp, and difficulty in scale-up to an industrial scale. The standard equipment most widely used at present is the paddling, PFI milling and Jokro milling, etc., but mechanical milling accounts for a considerable part of the total energy consumption during pulping. The cavitation technology is a novel degradation treatment technology with huge development potential, and is concerned by wide scientists and scholars. The hydrodynamic cavitation is the generation, growth and rupture of vapor bubbles caused by the increase of fluid velocity and the simultaneous decrease of static pressure, and releases huge energy in the form of heat and shock waves, chemical bonds between water molecules in water and atoms of dissolved oxygen molecules are broken, and hydroxyl radicals with strong oxidizing property are formed, and the mechanism of ultrasonic cavitation is that when ultrasonic waves are propagated in liquid, as sound waves are alternately circulated in sparse phase (negative pressure phase) and dense phase (positive pressure phase), cavitation bubbles are generated, collapsed and collapsed, and then instantaneous high temperature and high pressure are generated in the tiny periphery thereof, strong shock waves and high-speed jet flows are formed, and hydroxyl radicals with strong oxidizing property are formed. The cavitation effect can serve to enhance the refining of cellulose pulp and the present invention can be readily scaled up to industrial scale while being used in a continuous processing system. But the conventional Venturi tube type cavitation device is easy to block and is not suitable for refining paper. Therefore, a cavitation treatment device with simple structure, low energy consumption and good effect is urgently needed.

Us patent 2666368 proposes a column refiner, us patent 3506199 proposes a double-inlet disc refiner, CN1274302A proposes a double-disc refiner and a pulp refining control system and method, wherein the refiner described in the principle is to use a bearing to drive a rotor to physically stir and shear, although the purpose of pulp refining can be achieved, other reaction processes are not involved, so the refining efficiency is not high.

Disclosure of Invention

Aiming at the problems of limitation, high energy consumption and the like of the conventional long cellulose refining technology, the invention provides a cavitation device for the refining production of reinforced cellulose pulp, which has good refining effect and high efficiency and is coupled with hydrodynamic cavitation and ultrasonic cavitation.

The cavitation device for refining production of the reinforced cellulose pulp adopts the following technical scheme:

the device comprises a stator, a rotating shaft, rotors and an ultrasonic transducer, wherein the rotating shaft comprises a first rotating shaft and a second rotating shaft, the rotors comprise a first group of rotors and a second group of rotors, the stator is a closed cylinder, a feed inlet and a discharge outlet are respectively arranged at two opposite sides of the stator, the ultrasonic transducer is distributed on the inner wall of the stator, the first rotating shaft and the second rotating shaft are respectively arranged at two opposite side surfaces of the stator, the first group of rotors and the second group of rotors are both arranged in the stator and are respectively arranged on the first rotating shaft and the second rotating shaft, the first group of rotors and the second group of rotors at least comprise two separated wheel discs, rotor cavitation holes are distributed on the outer peripheral surface of each wheel disc, stator cavitation holes are distributed on the inner wall of the stator, and the gap distance between the outer end surface of each cavitation hole and the opposite surface of each cavitation hole is 4-8 mm,

the ultrasonic transducer is arranged on the inner wall of the stator at intervals of 2-8 circles and 2-6 circles in total and is distributed along the axial direction and the circumferential direction.

Each ultrasonic transducer is connected with an ultrasonic generator, the frequency of the ultrasonic generator is 40-80 kHz, and the single-machine power is 1500-3000W.

The wheel discs on the first group of rotors and the second group of rotors are symmetrically arranged, and the rotating directions are opposite.

The rotor cavitation hole and the stator cavitation hole are blind holes, and the ratio of the diameter to the depth is 3: 4. most preferably 40mm in depth and 30mm in diameter.

The cavitation holes on the upper end face of the wheel disc are distributed in concentric circles.

The rotating speed of the first rotating shaft and the rotating speed of the second rotating shaft are 3600-6000 r/min.

The surface roughness Ra of the inner wall of the cavitation hole is smaller than 1.6mm, so that the cavitation initial effect is enhanced, and further the cavitation efficiency is improved.

The feeding flow of the feeding hole is 1.5-4.5 m³And h, the reaction temperature in the stator is 50-95 ℃ (the heating effect is caused by cavitation phenomenon).

The device adopts a rotating hydrodynamic cavitation technology, innovatively drives the rotor through the high-speed rotation of the rotating shaft, so that cavitation holes in the rotor and paper pulp to be refined move relatively to generate cavitation bubbles efficiently, and the cavitation bubbles collapse and release huge energy when static pressure is restored. This energy is manifested as local hot spots up to 5000K, high pressures of 1000bar, with powerful shock waves and high-speed microjets (150 m/s). Under the extreme conditions, water molecules can be hydrolyzed to generate hydroxyl radicals, perhydroxyl radicals and hydrogen peroxide with strong oxidizing property. In addition, when the hydrodynamic cavitation effect is acted, ultrasonic waves are added, the two can efficiently cooperate to refine the cellulose pulp, the energy generated when cavitation collapse is greatly enhanced, and the generation of hydroxyl radicals is promoted, so that the refining effect of the cellulose pulp is finally improved, and the total refining effect (at least two times more) which is far higher than that of the two when the two are used independently can be obtained. In the design of the rotor, considering that the consistency of the pulp is greater than that of the common liquid, the sharpness and the friction force of the edge of the rotor are increased remarkably, and the cavitation phenomenon can be guaranteed to the maximum extent. The unique design of the device improves the contact area of the rotor and the stator, effectively increases the cavitation area and improves the paper pulp refining efficiency.

The invention applies the cavitation technology to the paper pulp refining, has the advantages of simple device, high efficiency, good utilization rate and the like, not only has the effect of physical stirring, but also accelerates the paper pulp refining process by utilizing the cavitation reaction. The invention has the following characteristics:

1. the device provided by the invention is used for refining the cellulose pulp by combining the cooperation of the hydrodynamic cavitation and the ultrasonic cavitation, the efficiency is far higher (can be improved by more than 3-4 times) than that of a method using the hydrodynamic cavitation or the ultrasonic cavitation alone, the efficiency is high, the refining amount of the method is large, and the continuous operation can be realized.

2. By adopting a unique stator design, the contact reaction surface is increased, and the cavitation area is ensured to be larger.

3. Two sets of six-wheel disc rotors are adopted, the structure is symmetrical and compact, the sharpness and friction design are increased on the edges of the rotors, and the cavitation efficiency is improved. The device can effectively balance the axial force during operation, so that the equipment can operate more stably, and the service life of the equipment is effectively prolonged.

4. The special design of the edge and the holes of the rotor greatly increases the cavitation area and further strengthens the cavitation effect.

5. The discharge port is additionally provided with a controllable valve, so that the discharging opportunity is conveniently controlled.

6. The size of the rotor and the stator can be increased, the space between the stator and the rotor is guaranteed to be 4-8 mm, and the requirement for refining larger paper pulp can be met by replacing a high-power variable frequency motor.

7. The electric energy is adopted as the energy, zero emission is realized, no pollution is caused, the environmental protection performance is good, the influence of the external environment is avoided, the flexibility is high, and the electric energy can be started and stopped as required.

8. The rotor of the device is of a hollow structure, and compared with the solid structure of the existing shear type cavitator, the device has the advantages of good stability, low energy consumption and easiness in assembly and disassembly.

9. The device has strong amplification, can change the size according to different working environments, and only needs to change the sizes of the stator and the rotor in the equipment.

10. The structure and technological parameters of the device are obtained by computational fluid mechanics simulation, multi-objective optimization design or actual degradation experiments.

Drawings

FIG. 1 is a schematic diagram of the configuration of the cavitation apparatus of the present invention for enhanced cellulose pulp refining production.

Fig. 2 is a schematic diagram of the distribution of ultrasonic transducers in the present invention.

FIG. 3 is a schematic diagram of the distribution of cavitation holes on the outer layer turntable of the present invention.

FIG. 4 is a schematic diagram of the distribution of cavitation holes on the intermediate turntable in the present invention.

FIG. 5 is a schematic diagram of the distribution of the cavitation holes on the inner layer of the turntable according to the present invention.

Fig. 6 is a pulp processing flow chart.

In the figure: 1. the rotor structure comprises a feeding hole, 2 mechanical seals, 3 a first rotating shaft, 4 angular contact ball bearings, 5 end covers, 6 sealing covers, 7 stators, 8 rotors in a first group, 9 rotor excircle cavitation holes, 10 stator cavitation holes, 11 rotors in a second group, 12 wedge keys, 13 second rotating shafts, 14 shaft sleeves, 15 control valves, 16 discharge holes, 17 ultrasonic transducers and 18 ultrasonic generators.

Detailed Description

The cavitation device for intensive cellulose pulp refining production of the present invention, as shown in fig. 1, comprises a stator 7, a rotating shaft, a rotor and an ultrasonic transducer 17. The shafts include a first shaft 3 and a second shaft 13. The rotors comprise a first set of rotors 8 and a second set of rotors 11.

The stator 7 is a closed cylinder body and is formed by enclosing two half shells, and the outer sides of the two half shells are conical. An ultrasonic transducer 17 is distributed on the inner wall of the stator 7. Each ultrasonic transducer 17 is connected to an external ultrasonic generator 18 to induce an ultrasonic cavitation phenomenon. Referring to fig. 2, the ultrasonic transducers 17 are embedded in the inner wall of the stator 7 along the axial direction and the circumferential direction in a manner of 2-8 turns per turn, 2-6 turns in total, and equal intervals. The number of the ultrasonic generators 18 is 1-4, the frequency is 40-80 kHz, and the single-machine power is 1500-3000W. After the ultrasonic wave is coupled, the energy generated when the cavitation bubble collapses can be greatly enhanced, the generation of hydroxyl free radicals is promoted, and the refining treatment effect is promoted.

Two opposite sides of the stator 7 are respectively provided with a bearing shell 5, a feed inlet 1 and a discharge outlet 16, an angular contact ball bearing 4 is arranged in the bearing shell 5, and the bearing shell 5 is connected with a sealing cover 2. The feed port 1 and the discharge port 16 are diagonally arranged to prevent a short flow phenomenon. A control valve 15 is arranged at the discharge opening 16 for controlling the timing of discharging the refined pulp.

The first group of rotors 8 and the second group of rotors 11 are arranged in the stator 7 and are respectively installed on the first rotating shaft 3 and the second rotating shaft 13 through wedge keys 12, the first rotating shaft 3 and the second rotating shaft 13 are respectively installed on two opposite side surfaces of the stator 7 through angular contact ball bearings 4, one end of each end of the first rotating shaft 3 and the second rotating shaft 13 extends out of the end of each end of the end of each end of the first rotating shaft 3 and the second rotating shaft 13, and the end of each end of the first rotating shafts and second group of the first rotating shafts 8 and second rotating shafts 13 and the second rotating shafts extend out of the end of each end of the end of each end of the end of each end of the end of each end of the end of each end of the end of each end of the end of each end of the stator 7 is connected to the end of each end of the end of each end of the end of. The first rotating shaft 3 drives the first set of rotors 8 to rotate, and the second rotating shaft 13 drives the second set of rotors 11 to rotate in the opposite direction. The angular contact ball bearing 4 is fixed through a bearing support cover, the top of the bearing support cover is connected with the bearing end cover 5 through screws, and the bearing support cover is fixed on the outer side of the stator 7 through screws. Sealing devices 2 are arranged in bearing shells 6 at two ends of a stator 7 on the rotating shaft, and mechanical sealing can be adopted to isolate paper pulp and prevent leakage.

The first set of rotors 8 and the second set of rotors 11 are arranged relatively in the stator, and each include three discs separated by a shaft sleeve 14, and are divided into an outer disc, a middle disc and an inner disc. The three discs of the first set of rotors 8 and the second set of rotors 11 are symmetrically arranged and rotate in opposite directions.

Rotor cavitation holes 9 are distributed on the outer peripheral surface (two end surfaces and an outer circular surface) of each wheel disc, stator cavitation holes 10 are distributed on the inner wall of the stator 7, the rotor cavitation holes 9 and the stator cavitation holes 10 are blind holes, the depth is 40mm, the diameter is 30mm, and the ratio of the diameter to the depth is 3: 4. the surface roughness Ra of the inner wall of the cavitation hole is smaller than 1.6mm, so that the cavitation primary effect is enhanced, and further the cavitation efficiency is improved. The clearance distance between the outer terminal surface of each cavitation hole and its opposite face is 4 ~ 8mm, and the clearance between the outer disc of rim plate and the stator inner wall that is exactly, the clearance between the adjacent rim plate and the clearance between outer rim plate and the stator inner end face are 4 ~ 8mm to guarantee that cavitation phenomenon is high-efficient to form. The distribution of the cavitation holes on the upper end surfaces of the outer layer wheel disc, the middle wheel disc and the inner layer wheel disc is shown in fig. 3, 4 and 5 and is concentric circle distribution. The rotating speed of the first group of rotors 8 and the second group of rotors 11 is 3600-6000 r/min.

The apparatus of the invention is applied to the refining of cellulose pulp in a process where the equipment used comprises a mixing tank, a filtration tank, a consistency adjustment tank, the apparatus of the invention and a collecting tank, as shown in fig. 4. The bleached cellulose pulp to be treated flows into a stirring tank, and sulfate is added to be fully stirred so as to ensure good strength (long fibers), opacity and printability (short fibers) of the paper. After being stirred uniformly, the mixture enters a filter tank to remove large granular solid matters. The paper pulp in the filter tank is added into a consistency adjusting tank, after the proportion of cellulose and water is adjusted to be the most suitable concentration of 3 percent, the paper pulp is sent into the device by a slurry pump to be refined.

The bleached wood cellulose pulp to be treated enters a stator 7 from a feeding hole 1, and the feeding flow is 1.5-4.5 m³The reaction temperature in the stator is 50-95 ℃, and the temperature rise is caused by the thermal effect of cavitation.

The first rotating shaft 3 and the second rotating shaft 13 respectively drive the first group of rotors 8 and the second group of rotors 11 to rotate, so that cavitation holes 10 in the stator 7 and cavitation holes 9 in the two groups of rotors interact with each other to shear fluid at high speed, local static pressure is lower than saturated vapor pressure, and hydrodynamic cavitation is induced. Meanwhile, the external ultrasonic sounder 18 converts electricity into a high-frequency alternating current signal matched with the ultrasonic transducer 17, and transmits the high-frequency alternating current signal to the ultrasonic transducer 17 embedded on the inner wall of the stator 7, and the ultrasonic transducer 17 converts electric energy into sound energy to generate high-frequency ultrasonic waves. The ultrasonic wave acts on the cellulose pulp to induce the ultrasonic cavitation phenomenon, thereby greatly strengthening the number of cavitation bubbles generated by the hydrodynamic cavitation and the collapse intensity thereof, realizing the effect of refining the cellulose pulp, outputting the finally produced treated pulp from a discharge port 16 to obtain the treated pulp, conveying the treated pulp to a collecting tank, and carrying out subsequent treatments such as rolling, drying and the like.

In the invention, the refining production experiment is carried out on the conifer and eucalyptus pulp, in order to prepare a sample easy to refine, 1.57% cellulose suspension consisting of 80% eucalyptus and 20% conifer fiber is suspended in tap water, and the cellulose pulp refining experiment is carried out after mechanical pre-refining is carried out by using a standard. The RGHC was washed before and after each cavitation experiment using a wash protocol that included 10 washes with tap water, 10 washes with 5% (v/v) sodium lauryl sulfate (Sigma, USA), and 20 washes with tap water. Finally, the RGHC pipework is dried using compressed air. Local pressure measurements were performed using a Hygrosens DRTre-10V-R16B pressure probe (uncertainty ± 0.2%). The flow was measured using a Buerkert SE32 flow meter (uncertainty ± 1%). The temperature of the water sample was monitored by a resistance thermometer model PT100A (uncertainty ± 0.2K). The heat exchanger was installed to be immersed in 10L of water in a stainless steel vessel to limit the heating temperature of the treated sample to 34 ℃. The stator and surrounding housing are made of clear acrylic glass, which acts as a cover. This enables us to shoot vacuole clouds using a high speed camera photon SA-Z. Motor power of RGHC is measured in units of Kilowatts (KW) by Norma4000 (Fluke). The cavitation number (σ), a parameter that indicates the relative sensitivity of the water flow to cavitation, is calculated using the following equation:

in the formula, p_VIs the vapor pressure of water (3169 Pa at 25 ℃); p is a radical of_LIs the pressure (Pa) measured locally before the treatment chamber; v (m/s) is the circumferential speed on the circumference (r ═ 0.025 m); ρ is the density of water (1,000 kg/m at 25 ℃) [28 ]]. The smaller the cavitation number, the more cavitation tends to occur. Shear rate (gamma) generated in the process chamber^·) Is calculated by dividing the circumferential velocity (v) by the height (l) of the gap between the rotor and stator teeth.

The following table shows the bleaching 1 for a concentration of 3%: 1 operating characteristics of rotary generators for softwood and eucalyptus pulp samples. At a rotation speed of 1000rpm and a flow rate of 7.5L/min (PL value of 153kPa, RGHC device head pressure of 7.0m), a value of 43.6 is sufficient to ensure that the RGHC operates in non-cavitated conditions. When the RGHC rotating speed is 5400rpm (the flow rate is 13.5L/min, p)_LValue of 124kPa, head of 9.2m) and a value of 1.2, cavitation was evident. Finally, at 6000rpm (flow 15.2L/min, p)_LValue 98kPa, head 10m), a value of 0.7, indicating greater cavitation intensity. This also reflects the higher shear rate (γ · is) produced in the reaction chamber

). To observe cavitation development in the treatment chamber, the washed RGHC was injected with tap water and run at the same rotational frequency as when filling the softwood and eucalyptus pulps. The rotor is moving in a counter-clockwise direction. However, at 5400rpm, developed cavitation forms were visible behind each gap between the opposing tips of the rotor and stator teeth, and shedding and collapse of cavitation clouds was observed. Finally, at 6000 revolutions per minute, the cavitation cloud formed becomes more violent and violent.

1 at 3% concentration: 1 operating characteristics of bleached softwood and eucalyptus pulp sample rotary generators

Experiments prove that under the optimal working condition and the structure (parameters are that the inner diameter of the stator is 400mm, and the width of the stator isThe degree is 340mm, and the wall thickness is 30 mm; rotor radius 100mm and 196mm, ultrasonic transducers were distributed in 6 rows with 4 equal distances per row) the following conclusions were reached: rotation speed 5400rpm, cavitation number 0.14, cellulose pulp flow 2.6m³The paper pulp can be refined by processing for 22 times and 4 minutes each time under the conditions that the reaction temperature is 75 ℃ and the auxiliary cavitation process is not needed; and the refining of the cellulose pulp can be completed within 2.5 minutes each time after the hydrodynamic cavitation and the ultrasonic cavitation are coupled for 22 times, so that the process flow is efficient and environment-friendly in the refining process of the cellulose pulp.

Claims

1. A cavitation device for intensifying refining production of cellulose pulp is characterized in that: the rotor comprises a first rotating shaft and a second rotating shaft, the rotor comprises a first group of rotor and a second group of rotor, the stator is a closed cylinder, a feed inlet and a discharge outlet are respectively arranged at two opposite sides of the stator, the ultrasonic transducers are distributed on the inner wall of the stator, the first rotating shaft and the second rotating shaft are respectively arranged at two opposite side surfaces of the stator, the first group of rotor and the second group of rotor are both arranged in the stator and are respectively arranged on the first rotating shaft and the second rotating shaft, the first group of rotor and the second group of rotor respectively comprise three separated wheel discs, which are divided into an outer wheel disc, a middle wheel disc and an inner wheel disc, cavitation holes at the upper end surfaces of the outer wheel disc, the middle wheel disc and the inner wheel disc are distributed in concentric circles, rotor cavitation holes are distributed at the outer peripheral surface of each wheel disc, the outer peripheral surface comprises an end surface and an outer circular surface, and stator cavitation holes are distributed on the inner wall of the stator, the gap distance between the outer end face of each cavitation hole and the opposite face of each cavitation hole is 4-8 mm;

the ultrasonic transducers are distributed on the inner wall of the stator at intervals of 2-8 circles, and 2-6 circles in total are distributed along the axial direction and the circumferential direction; each ultrasonic transducer is connected with an ultrasonic generator, the frequency of the ultrasonic generator is 40-80 kHz, and the single-machine power is 1500-3000W; the wheel discs on the first group of rotors and the second group of rotors are symmetrically arranged, and the rotating directions are opposite.

2. The cavitation device for refining production of enhanced cellulose pulp as set forth in claim 1, wherein: the rotor cavitation hole and the stator cavitation hole are blind holes, and the ratio of the diameter to the depth is 3: and 4, the depth is 40mm, the diameter is 30mm, and the cavitation holes on the upper end surface of the wheel disc are distributed in concentric circles.

3. The cavitation device for refining production of enhanced cellulose pulp as set forth in claim 1, wherein: the rotating speed of the first rotating shaft and the rotating speed of the second rotating shaft are 3600-6000 r/min, and the feeding flow of the feeding hole is 1.5-4.5 m³And h, the reaction temperature in the stator is 50-95 ℃.