CN211947299U

CN211947299U - Preparation system of lyocell spinning solution

Info

Publication number: CN211947299U
Application number: CN202020471589.4U
Authority: CN
Inventors: 刘斌; 魏良红; 杨丽君; 郝建全
Original assignee: Asia Symbol Shandong Pulp And Paper Co ltd
Current assignee: Asia Symbol Shandong Pulp And Paper Co ltd
Priority date: 2020-04-02
Filing date: 2020-04-02
Publication date: 2020-11-17
Anticipated expiration: 2030-04-02

Abstract

The application provides a preparation system of lyocell spinning solution, this system includes swelling device and dissolving device, the swelling device is used for dry pulp of NMMO solution swelling, the swelling device is the rotary drum, feed inlet and discharge gate are seted up respectively to rotary drum length direction both ends, the rotary drum makes its inside material take the position that is close to the top from the bottom and then free fall returns the bottom again through pivoted form, carries the material after the swelling towards the discharge gate simultaneously. Feeding cellulose dry pulp and an NMMO solution into a rotary drum, and repeatedly beating the mixed material in the rotary drum to obtain a swelled material; and discharging the swelled material from the rotary drum, and feeding the swelled material into a dissolving device for dissolving to obtain the lyocell spinning solution. The method can be used for treating the mixing of the whole pulp and the solvent, and the pulp and the solvent are mixed more fully in the beating process in the rotary drum. The application preferably adopts sectional type swelling, and is beneficial to reducing the number of white cores. The application is continuous production and has low energy consumption.

Description

Preparation system of lyocell spinning solution

Technical Field

The application relates to the technical field of lyocell fiber production, in particular to a preparation system of lyocell spinning solution.

Background

Lyocell (Lyocell) is a regenerated cellulose fiber produced by a tertiary amine oxide (N-methylmorpholine-N-oxide) solvent spinning technique, and is called a green fiber in the 21 st century because the solvent can be recovered.

In the process of preparing the Lyocell fiber, the mixing and swelling effects of cellulose pulp in a NMMO aqueous solution with a certain concentration are the key to complete dissolution of cellulose, the problems of uneven solid content of cellulose in the solution, formation of white cores and the like are easily caused by uneven mixing and swelling, the subsequent processes of spinning and the like are not facilitated, and the spinning quality is seriously influenced. The preparation of the spinning solution is mainly divided into a wet process and a dry process. The so-called wet process, namely: mixing cellulose pulp and water, pulping, squeezing the obtained pulp solution to remove water, crushing, mixing with NMMO, and swelling in a storage tank to fully combine NMMO and cellulose to form cellulose pulp porridge. After swelling, the obtained slurry is conveyed to a reaction kettle (such as a thin film evaporator) to be evaporated and dissolved, and a spinning solution is formed.

Chinese patent publication No. CN 108004611a discloses a method for preparing solvent-process cellulose fiber spinning dope by using dry pulp, which comprises preparing NMMO solution containing NaOH, then gradually adding pulp into the NMMO solution, mixing uniformly to obtain a slurry-porridge mixture; evaporating and dehydrating the paste mixture to swell cellulose, adding a stabilizer and an antioxidant into the swelled cellulose mixture, and uniformly mixing to obtain a premix; and finally, dehydrating, dissolving and defoaming the premix to obtain the cellulose spinning solution.

The prior art described above belongs to the dry process for the preparation of lyocell spinning solutions, generally having the following characteristics: (1) pulp does not need to be processed by crushing and the like, and is directly mixed with the NMMO solution in a pulp board form; this eliminates the process of hydraulic pulping, as compared to the wet process. (2) The process flow is simple; compared with a wet process, the dry pulp and the NMMO solution are mixed and then enter the film evaporator, so that the process flow is shortened. (3) The energy consumption of the film evaporator is reduced, and the productivity is improved; the reason is that the water content of the dry pulp is about 6-7%, compared with wet process pulp (the water content is 50%), the water amount brought by the dry pulp is greatly reduced, the energy consumption of film steam can be reduced, and the capacity can be improved. (4) The unit consumption of the NMMO solution evaporation steam is reduced; in the wet process, the concentration of NMMO is between about 80% and 84% when wet pulp is mixed with NMMO solution, and the concentration of NMMO solution required for dry pulp mixing is between 75% and 80%. The NMMO solution is recycled in the production process, the low-concentration NMMO solution is evaporated to obtain the high-concentration NMMO solution, and in the process, the evaporation concentration of the final NMMO solution is reduced, so that the steam consumption can be reduced. (5) The dry pulp is mixed with the NMMO solution, and the concentration of the NMMO solution is low, so that the pre-dissolving degree can be reduced, and the full contact swelling of the NMMO and cellulose is facilitated.

However, in the dry preparation technique, the cellulose/NMMO/H is prepared by mechanical external force provided by a hydrapulper₂In the production of O mixtures, it was found that in the spinning dope prepared by this method, still significant white core particles could be observed, which also indicates that there are certain disadvantages in the direct mixing of dry pulp with NMMO solvent, and that the swelling and dissolving effects need to be improved compared to the wet process. In addition, the mixed material has certain viscosity, strong shearing is generated by mechanical stirring, and the spinning quality can be seriously influenced by destroying the shape of part of fibers.

SUMMERY OF THE UTILITY MODEL

In view of this, the application provides a preparation system of lyocell spinning solution, and the preparation system that the application provided can produce lyocell spinning solution by the continuous type, and swelling is abundant to the quality is better, improves output, reduces the manufacturing cost of unit silk bundle, does benefit to popularization and application.

The application provides a preparation system of lyocell spinning solution, including swelling device and dissolving device, the swelling device is used for dry pulp of NMMO solution swelling, wherein, the swelling device is the rotary drum, feed inlet and discharge gate are seted up respectively at rotary drum length direction both ends, the rotary drum makes its inside material take the position that is close to the top from the bottom and then free fall returns the bottom, carries the material after the swelling towards the discharge gate simultaneously.

In some preferred embodiments, the drum is embodied in the form of, by rotation: the shell of the rotary drum is fixed, a rotatable material shifting part is arranged in the shell of the rotary drum, and the material shifting part drives the material to freely fall back to the bottom from the bottom of the rotary drum to a position close to the top.

In other preferred embodiments, the drum is configured to rotate by: the shell of the rotary drum rotates, a material shifting part rotating along with the shell is arranged in the shell of the rotary drum, and the material shifting part drives the material to freely fall back to the bottom from the bottom of the rotary drum to a position close to the top.

Preferably, a spraying belt is arranged between the feeding port and the discharging port and at the top of the outer shell of the rotary drum or close to the top of the outer shell of the rotary drum, the spraying belt extends along the axial direction of the outer shell of the rotary drum, and the NMMO solution is sprayed into the rotary drum from the spraying belt.

Preferably, two ends of the spraying belt extend to two ends of the outer shell of the rotary drum respectively.

Preferably, the rotary drum has an adjustable inclination angle of 0-10 degrees.

The embodiment of the present application provides a method for preparing a lyocell spinning solution using the preparation system described above, comprising the steps of:

adding dry pulp and NMMO solution into a rotary drum; rotating the rotary drum to repeatedly beat a material formed by mixing the dry pulp and the NMMO solution in the rotary drum to obtain a swelled material;

the swollen mass is discharged from the drum and sent to a dissolving apparatus for dissolution, e.g. by evaporation, to obtain a lyocell spinning solution.

Preferably, the NMMO solution is added into the rotary drum through a spraying assembly, the spraying assembly forms a spraying zone extending along the axial direction of the rotary drum, the spraying zone comprises at least two spraying sections for spraying NMMO solution with different concentrations, and in the adjacent spraying sections, the NMMO concentration sprayed by the front spraying section is lower than that sprayed by the rear spraying section.

Preferably, the spray zone comprises two spray sections, a first spray section in front and a second spray section in back; further, the mass concentration of the NMMO in the first spraying section is preferably 72-78%, and the spraying temperature is preferably 75-82 ℃.

Furthermore, the mass concentration of the second spraying section NMMO is preferably 78-84%; the spraying temperature is preferably 72-77 ℃.

Preferably, the time for spraying and mixing the materials in the first spraying section is longer than the time for spraying and mixing the materials in the second spraying section.

The embodiment of the application also provides the application of the lyocell spinning solution prepared by the method in the production of lyocell fibers.

Compared with the prior art, the dry pulp and NMMO mixing and swelling device has the advantages that the rotary drum is used as main equipment for mixing and swelling dry pulp and NMMO, the rotary drum drives internal materials to be brought to a position close to the top from the bottom of the rotary drum in a rotating mode, and then the materials fall freely and are beaten at the bottom of the rotary drum under the action of gravity; because the rotary drum has a certain inclination angle, the material after swelling can be conveyed to the discharge hole in the rotating process. Practice has shown that this natural beating process is beneficial for the swelling effect of the dry pulp compared to the mechanical agitation process of hydropulper. Because the mixed material is subjected to the process of weightlessness and beating at the bottom of the rotary drum, solvent molecules can be promoted to enter between cellulose molecular chains. The reason for this is that, in the weightless state, the molecular chains of cellulose are in an extended state, and the gaps between the molecular chains are relatively uniform, which is favorable for solvent molecules to enter between the molecular chains. The material impacts the bottom instantly, so that the opportunity of NMMO molecules permeating into the gaps of cellulose molecular chains is provided, NMMO solvent molecules smoothly enter between the cellulose molecular chains, and the NMMO solvent molecules and cellulose are fully swelled. This significantly increases the swelling ratio of the dry pulp, and is sufficient to fully and uniformly swell the solvent and cellulose, especially after repeated beating for a long period of time. In the embodiment of the application, the swelled material is directly sent to a dissolving device for dissolving to obtain the lyocell spinning solution. The application can treat the mixing of the whole pulp and the solvent, and the pulp and the solvent are mixed more fully in the beating process, thereby being beneficial to improving the product quality. In addition, the number of the white cores is further reduced by adopting a sectional type spraying swelling technical means subversively.

In addition, the obvious defect of the existing hydrapulper in dry swelling is that the discharging is difficult, and the discharging of the hydrapulper can only be discharged through a pipeline. But after the swelling is finished, the state of the material is viscous, the fluidity is poor, and the material cannot be gathered together due to stirring, so that the discharging difficulty of the existing swelling implementation mode is higher. Compared with the prior art, because the viscidity of material self in this application rotary drum, beat the in-process material and can gather together gradually, when finally reaching the discharge gate, the material can present similar "dough" state, and the ejection of compact is easy.

Drawings

FIG. 1 is a schematic diagram of the structure of a swelling apparatus according to some embodiments of the present disclosure;

FIG. 2 is a schematic view A-A of FIG. 1;

FIG. 3 is a schematic view of B-B of FIG. 1;

FIG. 4 is a schematic diagram of a swelling apparatus according to further embodiments of the present disclosure;

FIG. 5 is a schematic view A-A of FIG. 4;

FIG. 6 is a graph showing the effect of the swelling process of example 1 on the dope;

FIG. 7 is a graph showing the effect of the swelling process of example 2 on the dope obtained.

Detailed Description

The technical solutions in the embodiments of the present application are clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

The application provides a preparation system of lyocell spinning solution, including swelling device and dissolving device, the swelling device is used for dry pulp of NMMO solution swelling, wherein, the swelling device is the rotary drum, feed inlet and discharge gate are seted up respectively to rotary drum length direction both ends, the rotary drum makes its inside material take the position that is close to the top from the bottom and then free fall returns the bottom again through pivoted form, carries the material after the swelling towards the discharge gate simultaneously.

The preparation system provided by the application can be used for continuously producing the lyocell spinning solution, has good quality and low energy consumption, and is beneficial to popularization and application.

Referring to fig. 1-3, fig. 1 is a schematic diagram of a swelling apparatus according to some embodiments of the present disclosure, and fig. 2 and 3 are schematic diagrams a-A, B-B, respectively. Wherein, 10 is the rotary drum shell, 101 is the setting beam, 102 is the beater, 103 is the landing leg, 20 is the solvent spray zone, 30 is the transmission shaft, 301 is the spoke, 302 is the entry runner, 303 is the export runner, 40 is the hydro-cylinder, 50 is the feed inlet, 60 is the discharge gate, 70 is the pulse high-pressure gas entry.

The preparation system of the lyocell spinning solution according to some embodiments of the present application includes a swelling apparatus shown in fig. 1, the swelling apparatus is a drum with a stationary outer shell and a rotating inner shell, and the specific structure includes: the stationary drum housing 10 and the internally arranged rotatable kick-off bar 101 are preferably also provided with a number of beaters 102. The housing 10 is the exterior of the drum and can support the bottom by legs 103 fixed to the ground; the inner space of the rotary drum shell is used for mixing and swelling materials, the material shifting beam 101 is used as a material shifting part, and the material is driven by the beater 102 to freely fall back to the bottom from the bottom of the rotary drum to a position close to the top.

In an embodiment of the present application, the interior of the housing 10 may form a volume and structure suitable for spraying the NMMO solution into the interior of the drum. A long cylindrical mixing cavity is formed inside the shell 10; the length and the caliber of the shell are customized according to the actual process requirements, for example, the length can be 10 meters, actually, the length of the shell can reach tens of meters, even longer, and the diameter can be 1m or 2 m. One end of the rotary drum in the length direction is a feeding end (one end of the feeding hole), and the other end of the rotary drum is a discharging end (one end of the discharging hole).

And, the top of the drum shell 10 or a position close to the top is provided with a plurality of solvent spraying ports in the transverse direction (i.e. the length direction), and the solvent spraying ports extend and are arranged along the axial direction of the drum shell to form a solvent spraying belt 20 for spraying the solvent between the feeding end and the discharging end, i.e. the NMMO solvent is sprayed into the drum from the spraying belt. Preferably, two ends of the spraying belt extend to two ends of the rotary drum shell respectively. When the solvent is sprayed, the spraying zone can be divided into a plurality of spraying sections according to different concentrations of the solvent, namely, a spraying area for spraying the solvent with the same concentration is regarded as one spraying section. The spraying belt can form at least two spraying sections for spraying solvents with different concentrations.

The swelling device is used for swelling dry pulp with the NMMO solution, and the application has no special limitation on the feeding form of the materials such as the NMMO solution and the dry pulp, and the materials can enter the swelling device from the feeding hole. Wherein the NMMO solution can be added into the rotary drum through a spraying assembly. In the embodiment of the present application, the spray assembly has various forms, and there is no particular limitation on the specification, the sectional distance, and the like of each solvent spray port. Exemplarily, a row of long and narrow spray holes can be arranged at the top of the rotary drum shell along the head and the tail of the rotary drum, and the first spray section and the second spray section are divided by sectional spraying according to solvents with different concentrations; or, a row of nozzles are arranged at the top of the rotary drum corresponding to the spraying openings, the nozzle at the feeding end sprays one concentration solvent, and the nozzle at the discharging end sprays the other concentration solvent.

In addition, the outside of the drum may be provided with a temperature adjusting jacket or an electric tracing device (not shown in fig. 1) for independently controlling the temperature in stages. Lifting equipment can be arranged below one end of the feeding hole of the rotary drum, one end of the feeding hole of the rotary drum is controlled to lift relative to one end of the discharging hole of the rotary drum, and the lifting equipment is necessary to adjust the conveying speed of materials in the rotary drum and control the mixing swelling time by adjusting the inclination angle.

In the above-mentioned embodiment of this application, drum shell 10 is motionless, transmission shaft 30 (outside motor drive) drives spoke 301 and rotates, spoke 301 drives export runner 303 and rotates, runner 303 drives dials material crossbeam 101 and rotates, dial the left end of material crossbeam 101 and fix on entry runner 302, guarantee to dial material crossbeam 101 and hug closely reliable the revolving of drum shell inner wall, dial material crossbeam 101 and drive the material and rise along the shell inner wall, material whereabouts under the action of gravity, so beat repeatedly and realize that the material mixes, the swelling, and slowly carry backward. Because the suspended matter materials have certain viscosity, the materials are converged together in the rotating process, and the materials are continuously beaten like dough and are gathered after being crushed. During this beating process, the pulp and solvent are more thoroughly mixed. If the materials are stirred and mixed only by the components such as the stirring blades, the material mixing uniformity is poor, and the swelling effect is poor due to the existence of a plurality of stirring dead angles. The pulp and the solvent are fully mixed and swelled by using a beating mode, and the effect is better than that of stirring by using the blades; dead angles do not exist in the rotary drum, so that uniform swelling is realized.

The embodiment of the application has no special limitation on structural designs such as the rotary drum shell, the material poking component and the like, and the material poking and beating functions can be realized. Specifically, a plurality of short rod-shaped protruding components (i.e. the beater 102) are arranged inside the rotary drum; the beater 102 is directly fixed on the rotary drum material stirring beam 101, the material stirring beam 101 drives the beater 102, materials can be stirred to a higher height smoothly, and the beating effect is improved. Further, the cylinder 40 drives the housing 10 to ascend and descend. The two ends of the length direction of the rotary drum are respectively provided with a feeding hole 50 and a discharging hole 60, pulp is fed into the rotary drum from the feeding hole 50 and discharged from the discharging hole 60, one end of the discharging hole is also provided with a pulse high-pressure gas inlet 70, and when the discharging hole is blocked by materials, high-pressure gas sprayed by the gas inlet 70 breaks up the blocked material mass, so that the materials are smoothly output.

In the embodiment of the application, the inclination angle of the rotary drum is adjustable, and is used for adjusting the material conveying speed, for example, the inclination angle is adjusted between more than 0 and less than 10 degrees. In this application, the inside hired roughneck that sets up of rotary drum not only does benefit to and mixes, swells, can make the material carry backward moreover under the slope situation. The beater is provided with a plurality of short rod-shaped bulges which are spaced from each other, and the overall shape is preferably consistent; the end of the rotary drum far away from the rotary drum can be any shape such as a square head, a round head, a pointed end and the like, and the number of the end is not particularly limited. Wherein the use of a wedge-shaped tip beater is preferred, reducing the risk of the material being squeezed between the protrusions and the inner wall of the drum housing. In the preferred embodiment of the present application, the plurality of raised members (the beaters 102) are fixed to respective kick-off beams 101. In addition, the application has no special limitation on the transmission structures such as the spoke and the rotating wheel, and the specific structure shown in fig. 3 can be adopted, and other designs can also be adopted.

In the preparation system of the embodiment of the application, the drum of the swelling device rotates at a certain inclination angle, so that the material in the swelling device is brought from the bottom to a position close to the top and then freely falls back to the bottom, meanwhile, the solvent is sprayed in sections, the swelling is finished, and the swollen material is conveyed to the dissolving device. The dissolving device is a reaction kettle communicated with a discharge port of the swelling device; the dissolving device is not particularly limited in the present application, and is exemplified by a thin film evaporator well known to those skilled in the art. And dissolving the swelled material in a reaction kettle, and sending the obtained spinning solution to a spinning machine for spinning, thereby producing the Lyocell fiber.

The preparation system provided by the application can be used for continuously producing the lyocell spinning solution, the swelling is sufficient, the quality is good, the yield is improved, and the production cost of unit tows is reduced.

In other embodiments of the present application, the swelling means is schematically illustrated in FIGS. 4-5. Wherein 11 is a rotary drum shell, 111 is a kick-off beam, 112 is a beater, 31 is a driving assembly, 51 is a feed inlet, and 61 is a discharge outlet.

The lyocell spinning solution preparation system according to other embodiments of the present application includes a swelling apparatus shown in fig. 4, the swelling apparatus is a drum having a housing rotating structure, and the specific structure includes: the rotatable drum housing 11 and the material-ejecting beam 111 disposed therein and rotating therewith are preferably further provided with a plurality of beaters 112. The drum shell 11 rotates, and the material stirring beam 111 fixed on the inner wall of the shell drives the material to beat in the cavity, namely the material is driven to freely fall back to the bottom from the bottom of the drum to a position close to the top and is slowly conveyed backwards.

In the embodiment of the application, a mixing cavity is arranged inside the shell 11; the length and the caliber of the shell are customized according to the actual process requirements, for example, the length can be 10 meters, actually, the length of the shell can reach tens of meters, even longer, and the diameter can be 1m or 2 m. One end of the rotary drum in the length direction is a feeding end (one end of the feeding hole), and the other end of the rotary drum is a discharging end (one end of the discharging hole). A spray pipe can extend into the mixing cavity of the rotary drum between the feed inlet and the discharge outlet, the spray pipe is provided with a row of spray nozzles, the spray nozzles form a spray belt, and the spray belt extends along the axial direction of the shell of the rotary drum and can extend to two ends; from the spraying zone, the NMMO solution is sprayed into the rotating drum. Alternatively, both solvent and pulp enter the swelling apparatus at the feed inlet (as shown in FIG. 4).

In the embodiments of the present application, the drum housing 11 is driven to rotate by the driving assembly 31 (the driving assembly 31 is a conventional transmission mechanism composed of a motor and gears), and the material-stirring beam 111 fixed on the housing drives the material to beat in the cavity, so that the material is mixed, swelled, and slowly conveyed backwards by repeated beating. Preferably, a plurality of short rod-shaped protruding components (i.e. the beater 112) are arranged inside the rotary drum; the beater 112 is directly fixed on the rotary drum material stirring beam 111, and the material stirring beam 111 and the beater 112 rotate along with the shell, so that the stirring effect is enhanced. A feed inlet 51 and a discharge outlet 61 are respectively arranged at two ends of the drum in the length direction, pulp and NMMO solution are fed into the drum from the feed inlet 51, and the swelled material is discharged from the discharge outlet 61.

The inclination angle of the drum in the above embodiments of the present application can also be adjusted, for example, between more than 0 and less than 10 °. In this application, the inside hired roughneck that sets up of rotary drum not only does benefit to and mixes, swells, can make the material carry backward moreover under the slope situation. The beater is provided with a plurality of short rod-shaped bulges which are spaced from each other, and the overall shape is preferably consistent; the end of the rotary drum far away from the rotary drum can be any shape such as a square head, a round head, a pointed end and the like, and the number of the end is not particularly limited. In the preferred embodiment of the present application, the plurality of protruding members (beaters 112) are fixed on the corresponding material-stirring beam 111, and are uniformly distributed along the circumferential direction of the drum, such as 6 sets of beaters shown in fig. 5; and are arranged in rows and at regular intervals longitudinally. In addition, the present application is not limited to the drive assembly described.

The dry pulp enters a dissolving device after being swelled by a swelling device; the dissolving device is a reaction kettle communicated with a discharge port of the swelling device. The dissolving device is not particularly limited in the present application, and is exemplified by a thin film evaporator well known to those skilled in the art. And dissolving the swelled material in a reaction kettle, and sending the obtained spinning solution to a spinning machine for spinning, thereby producing the Lyocell fiber.

The main equipment that dry pulp and NMMO mix, swell is adopted as to the rotary drum in this application, the rotary drum drives inside material rotation through pivoted working process, can take to the position that is close to the top from the bottom, free fall beat in the bottom under the action of gravity. The application can treat the mixing of the whole pulp and the solvent, and the pulp and the solvent are mixed more fully in the beating process, so that the spinning solution and the fiber with better quality can be obtained.

The embodiment of the present application provides a method for preparing a lyocell spinning solution using the preparation system as described above, comprising the steps of:

and discharging the swelled material from the rotary drum, and feeding the swelled material into a dissolving device for dissolving to obtain the lyocell spinning solution.

The method can be used for continuously producing the lyocell spinning solution, improves the quality, reduces the energy consumption, and is suitable for large-scale production.

The embodiment of the application adopts a dry preparation process, takes cellulose dry pulp as a raw material, and the water content of the dry pulp is about 6-7%. The amount of water brought by the dry pulp is low, so that the energy consumption of film steam can be reduced, and the productivity can be improved. Some embodiments of the present application feed dry pulp from the feed inlet at a feed rate of 1.0 to 1.5 t/min. In addition, in the embodiment of the application, preferably, the NMMO solution is added into the drum through the spraying assembly, and the spraying assembly forms a spraying belt extending along the axial direction of the drum, that is, the pulp and the NMMO solution are added into the swelling device to be mixed and swelled, so as to obtain the swelled material.

Wherein the structure of the swelling device and the like are as described above. For example, the inclination angle of the swelling device is adjustable between more than 0 and less than 10 degrees, and the rotation frequency of the rotary drum is determined according to the actual process requirements, and can be 3-5rpm, for example. The pulp feed and the sprayed NMMO solvent should be maintained at a ratio which can be determined according to the actual process requirements. For example, the mass ratio of NMMO/cellulose in the formed swollen mass can be determined to be 6.4 (the ratio can be changed according to the process requirements); the pulp feed rate and solvent spray rate can then be determined from this ratio.

This application embodiment stir the crossbeam in the rotary drum and can stir the material and rise, when the material is close to the rotary drum top, because self gravity, fall back to the rotary drum bottom again, keep this state, last repetitive motion. Preferably, when spraying the NMMO solvent, at least two spraying sections for spraying different concentrations are formed on the spraying belt, and in the adjacent spraying sections, the concentration of the NMMO sprayed by the previous spraying section is lower than that of the spraying section located behind the previous spraying section. Namely, the solvent is preferably sprayed in sections, for example, two sections, or three or more sections can be sprayed; the control of the mixing time proportion of each section can be determined by the length proportion of each section, namely the spraying time and the length of each section are in proportional relation.

In some embodiments of the present application, the spray zone includes two spray sections, a first spray section in front and a second spray section in back. The mass concentration of the NMMO in the first spraying section is preferably 72-78%, and the spraying temperature is preferably 75-82 ℃. The mass concentration of the second spraying section NMMO is preferably 78-84%; the spraying temperature is preferably 72-77 ℃. In other embodiments of the present application, the spray zone spray concentration is uniform.

NMMO is very easy to dissolve in water, is easy to dissolve in polar organic solvents such as ethanol, methanol and the like, has higher solubility in hot acetone and benzene, and is insoluble in general organic solvents; it can be combined with 1-4 water molecules, and has stable chemical property at room temperature. The NMMO aqueous solution is a high-quality solvent for cellulose, but the cellulose has the characteristics of high crystallinity and many hydrogen bonds, so that the cellulose is difficult to be successfully dissolved in the concentrated NMMO aqueous solution. In the dry process, the mass concentration of the NMMO solution required for mixing the dry pulp is generally between 75% and 80%. The NMMO solution is recycled in the production process, the low-concentration NMMO solution is evaporated to obtain the high-concentration NMMO solution, and in the process, the evaporation concentration of the final NMMO solution is reduced, so that the steam consumption can be reduced.

For the sectional spraying NMMO solution, solvents with different concentrations can be sequentially added in a sectional manner, namely a front-end nozzle sprays one concentration solvent, and a rear-end nozzle sprays the other concentration solvent; the present application prefers that the former spray concentration is lower than the latter spray concentration, which also has a positive effect on swelling. The method has the advantages that after the solution with low NMMO concentration is added, the pulp is already in the NMMO solution environment, partial swelling occurs inside the pulp, and under the buffering action condition, the solution with high NMMO concentration is added, so that the degree of partial dissolving of the NMMO solvent to the pulp to form gel is weakened, and the gel can prevent cellulose from fully swelling and is not expected.

Preferably, the time for spraying and mixing the materials in the first spraying section is longer than the time for spraying and mixing the materials in the second spraying section. The time for controlling the pulp to be conveyed in the rotary drum is also a key parameter in the embodiment of the application, and too fast conveying speed means that the swelling time of the pulp is too short, the swelling is difficult to reach a sufficient degree, and too long conveying time increases the cost and reduces the production efficiency.

For example, some examples herein control the swelling time to 150min (i.e., the time from pulp entering the drum to pulp exiting the drum). This time is related to the length, inner diameter, rotation speed and inclination angle of the drum, because the length and inner diameter are fixed parameters (the drum can be changed and adjusted, of course), the swelling time can be controlled by adjusting the inclination angle and rotation speed.

After the swelling is finished, the swollen material is directly sent to a dissolving device such as a reaction kettle and the like for dissolving, so as to prepare the Lyocell spinning solution.

The device for dissolving, such as a thin film evaporator, process conditions and the like, is not particularly limited, and the evaporation and dissolution process commonly used in the field can be adopted. In the examples of the present application, the mass ratio of NMMO/cellulose in the obtained cellulose suspension is 6-7, for example 6.4.

The application also provides the application of the lyocell spinning solution obtained by the preparation method in the production of lyocell fibers; and conveying the obtained Lyocell spinning solution to a spinning machine for conventional spinning to produce the Lyocell fiber.

The method has the advantages of good swelling effect and low white core quantity. Moreover, the method is simple in process flow, low in energy consumption and suitable for large-scale production.

For further understanding of the present application, the system for preparing a lyocell spinning solution provided herein will be described in detail with reference to examples below. It should be understood, however, that these examples are for illustrative purposes only and are not intended to limit the scope of the present application, which is defined by the following examples.

Example 1

First, the main raw materials

1. Aqueous NMMO as solvent, at concentrations of 75% and 83%, respectively;

2. pulp raw materials: wood pulp (Sappi pulp in south africa, 6% water, degree of polymerization 520).

II, main equipment:

1. a rotary drum with the structure shown in figures 1-3 is adopted, namely, a shell is fixed, and a material shifting component such as a material shifting beam and the like moves around along the inner wall of the shell, so that the purpose of scraping materials on the inner wall of the shell is achieved. The drum has a length of 20 m and a diameter of 2 m.

A spraying belt is arranged at the top of the shell of the rotary drum, and a first spraying section (namely the front half part) sprays a solvent with the concentration of 75 percent; the second spraying section (i.e. the latter half) sprays 83% of solvent, and the length ratio of the two spraying sections is 1: 1.

2. The test equipment model for swelling ratio was a DD5M low speed centrifuge.

Third, description of the embodiments

Continuously conveying pulp to a feeding hole of the rotary drum, and conveying the pulp entering the rotary drum backwards along the rotary drum under the stirring of a stirring part of the rotary drum; the material shifting beam has the orbiting speed of 3-5 rpm;

a spraying belt at the top of the rotary drum sprays a solvent into the rotary drum according to a preset concentration (namely, the first half part sprays the solvent with the concentration of 75%, and the second half part sprays the solvent with the concentration of 83%); spraying in the whole course without stop.

In production, the pulp is continuously put into the rotary drum at the feeding speed of 1.06t/min, and the rotary drum keeps normal and stable operation. Thus, a pulp feed rate of 1.06t/min corresponds to a pure NMMO injection rate of 6.4t/min (satisfying the NMMO/cellulose relationship of 6.4). In the operation, the first half part of the spraying belt is uniformly sprayed for 3.2t/min, and the second half part of the spraying belt is uniformly sprayed for 3.2 t/min. According to the spraying concentration of each part, the spraying speed of spraying the solvent with the concentration of 75% on the front half part of the spraying belt is 4.27 t/min; the spraying speed of spraying the solvent with the concentration of 83 percent in the latter half part of the spraying belt is 3.86 t/min. The spraying temperature of the front half part is 75-82 ℃; the spraying temperature of the latter half part is 72-77 ℃. As mentioned above, it is necessary that the solvent is sprayed in the form of a spray belt, which is effective in preventing the problem that the solvent is not mixed with the pulp in a local area due to a concentrated spray. When the solvent is sprayed a little bit, the mixed solvent can quickly flow backwards, so that the swelling process of the cellulose can not be completed.

In this operation, the swelling time (i.e., the time from the entry of the pulp into the drum to the exit of the pulp from the drum) was controlled to 150 min.

Through the operation, the finally swelled material can directly enter a reaction kettle to be evaporated and dissolved.

3 parts of the material swelled by the operation, 2kg each, were taken for swelling rate test.

The first centrifuged material weighed 1.93kg, the second centrifuged material weighed 1.92kg, and the third centrifuged material weighed 1.94 kg. Thus, the corresponding swelling ratios were 96.5%, 96.0% and 97.0%, respectively, and the average swelling ratio was 96.65%.

The swelling rate of the existing process is generally 88-92%, such as swelling materials (suspension) prepared by a wet method. In comparison, the cellulose suspension prepared using the technique of the present application has excellent swelling effect.

In addition, materials with poor swelling effect still have more white cores in the solution after being prepared into spinning solution by evaporation and dissolution. Based on this, in order to further demonstrate the above swelling effect, in the dope obtained in this example, 1 part of a small sample of the dope was taken out and placed under an excellent sunlight environment and observed with a magnifying glass of magnification 5 times, and substantially no white core particles were found except for a small amount of bubbles (see fig. 6). This is almost impossible with conventional dissolution processes.

Example 2

First, the main raw materials

1. Aqueous NMMO at a concentration of 80%;

Second, main equipment

1. A rotary drum (material stirring components such as a stirring beam and the like are directly fixed on the inner wall of a shell of the rotary drum, the shell of the rotary drum rotates under the drive of an external bearing and a power assembly) as shown in figures 4-5 is adopted, and NMMO solvent and pulp are conveyed into the rotary drum from a pulp inlet. The drum has a length of 20 m and a diameter of 2 m.

2. The test equipment model for swelling ratio was a DD5M low speed centrifuge.

Third, description of the embodiments

In production, the pulp is continuously put into the rotary drum at the feeding speed of 1.06t/min, the rotary drum keeps normal and stable operation, and the rotating speed of the rotary drum is 3-5 rpm. Thus, a pulp feed rate of 1.06t/min corresponds to a pure NMMO injection rate of 6.4t/min (satisfying the NMMO/cellulose relationship of 6.4). In this operation, the NMMO concentration used was 80% and the rate of spraying the aqueous NMMO solution was 8.0 t/min. The solvent NMMO was added at a rate of 8t/min from the feed inlet at a temperature of 78 ℃.

2kg of the materials swelled by the operation were taken 3 parts each, and swelling ratio was measured.

The first centrifuged material weighed 1.89kg, the second centrifuged material weighed 1.90kg, and the third centrifuged material weighed 1.89 kg. Thus, the corresponding swelling ratios were 94.7%, 95.0% and 94.7%, respectively, and the average swelling ratio was 94.80%.

The swelling rate of the existing process is generally 88-92%, and the comparison shows that the swollen material obtained by the operation has an excellent swelling effect.

In addition, materials with poor swelling effect still have more white cores in the solution after being prepared into spinning solution by evaporation and dissolution. Based on this, in order to further prove the above swelling effect, 1 part of a stock solution was taken out from the solution dissolved by the present procedure, and observed under an environment excellent in sunlight with a magnifying glass having a magnification of 5 times, substantially no white core particles were found (see fig. 7). This is almost impossible with conventional dissolution processes.

The test is strongly proven: through the preparation system of this application, pulp and solvent form the mixture, under self gravity, beat repeatedly, can impel solvent and pulp abundant swelling, probably because such beating process can make the solvent try to get into the molecular clearance of pulp from different angles repeatedly, even and soft in addition, avoid external force to tear, influence the materialization performance of cellulose.

In addition, the rotary drum type swelling equipment has the great advantage that the single-line production capacity of the cellulose fibers is greatly improved. In the prior art, both dry production as mentioned in the background and other wet processes, it is necessary to use a hydropulper or a pulper device like a pulper in water, which not only has a small volume but also directly stirs the material by the rotation of the blades, which determines the limited weight of the pulp to be added. At present, the annual single line capacity is difficult to break through 2 ten thousand tons. By adopting the technology, the single-line capacity has qualitative leap, and can reach the annual capacity of hundreds of thousands or even more. The method is unexpected for the prior art, the production cost of the single line is undoubtedly reduced due to the improvement of the single line capacity, and a wide prospect is created for the popularization of the product.

The foregoing is only a preferred embodiment of the present application, and it should be noted that various modifications of the embodiments can be implemented by those skilled in the art without departing from the technical principle of the present application, and these modifications should be considered as the scope of the present application.

Claims

1. A preparation system of a lyocell spinning solution comprises a swelling device and a dissolving device, wherein dry pulp enters the dissolving device to be dissolved into a spinning stock solution after being swelled by the swelling device, the swelling device swells the dry pulp by NMMO solution, and the preparation system is characterized in that the swelling device is a rotary drum, a feed inlet and a discharge outlet are respectively formed in two ends of the rotary drum in the length direction, the rotary drum enables materials in the rotary drum to freely fall back to the bottom from the bottom to a position close to the top in a rotating mode, and meanwhile, the swelled materials are conveyed towards the discharge outlet.

2. The system for preparing as claimed in claim 1, characterized in that said drum is in particular in the form of, by rotation: the shell of the rotary drum is fixed, a rotatable material shifting part is arranged in the shell of the rotary drum, and the material shifting part drives the material to freely fall back to the bottom from the bottom of the rotary drum to a position close to the top.

3. The system for preparing as claimed in claim 1, characterized in that said drum is in particular in the form of, by rotation: the shell of the rotary drum rotates, a material shifting part rotating along with the shell is arranged in the shell of the rotary drum, and the material shifting part drives the material to freely fall back to the bottom from the bottom of the rotary drum to a position close to the top.

4. A production system according to claim 2 or 3, characterized in that a spray belt is arranged between the inlet and the outlet, at or near the top of the housing of the drum, the spray belt extending in the axial direction of the housing of the drum, from which spray belt the NMMO solution is sprayed into the drum.

5. The manufacturing system of claim 4, wherein both ends of the spray belt extend to both ends of the outer shell of the drum, respectively.

6. The manufacturing system of claim 5, wherein the drum has an adjustable inclination angle of 0-10 °.