KR100497261B1 - Method and apparatus for simultaneously grinding and drying the material to be milled containing the moist cellulose ether - Google Patents

Abstract

The present invention relates to a method and apparatus for simultaneously grinding and drying a material to be ground comprising a moist cellulose ether, wherein the gas stream is divided into three partial gas streams. . The first partial gas stream transports the material to be crushed into the grinding and friction space of the mill 26, while the second partial gas stream flows around the friction space in the mill. The third partial gas stream is connected to the output side of the grinder, takes the decomposed and dried comminuted material, and is conveyed out of the grinder by the first and second partial gas streams to convey the material to the separator 30. do.

Description

Method and apparatus for simultaneously grinding and drying the material to be ground comprising wet cellulose ether

The present invention relates to a method for simultaneously pulverizing and drying a material to be pulverized comprising a damp cellulose ether and to an apparatus for carrying out the method.

In principle, all cellulose ethers must be ground and dried in order to be suitable for use. After the reaction and after washing of the by-products produced during the reaction, the cellulose ethers are crumbly, clumpy, fibrous, in the form of wool or cotton structures. In this form, they are not suitable for use in products which are soluble in organic and / or aqueous media, for example. In general, it is necessary to establish specific particle size distributions, dryness, and viscosity for different fields of use of cellulose ethers. Thus, ethers in finely divided or very finely divided forms need to be able to produce solutions without lumps quickly in water. For rapidly swelling ethers, for example required in oil drilling or construction industry, for example, the viscosity distribution and / or particle size distribution of the products are of decisive importance for their effect.

As such, EP-B 0 370 447 discloses cellulose ethers having an initial moisture of 20 to 70% by weight are introduced into a circular space by a conveying gas, impinge-crushed during circulation, and the product is reversed against impingement decomposition. Flowing and friction-decomposed at the same time, the circumferential velocity in counter-working reduction stages is adjusted such that this value is produced to produce grinding energy that dries the final product to a predetermined residual moisture of 1 to 10% by weight. A method for simultaneously grinding and drying wet cellulose ethers is disclosed. In the case of this method, the ground material is further conveyed by the gas stream introduced into the cracking spaces, which is then separated from the gas stream and optionally optionally sorted. This single-stage method, in which grinding and drying are simultaneously performed, can produce excess sized materials that exceed a predetermined particle size or particle size distribution and are thus returned to feedstock with the aid of a device known per se. . Before returning to the circulator, the oversized material must be moistened again to prevent the reduction of hornification or viscosity caused by these product debris.

DE-C 952 264 discloses a three stage process for transferring moist, fibrous methyl celluloses to high dissolving rate powders. Here, the product containing 50 to 70% by weight of water is first cooled to 10 to 20 ° C by employing a screw extruder homogenized into a cake-like mass and cooled and milled in a caged hammner mill. It is dried in a circulating-air dryer.

DE-C 24 10 789 (= US-A 4,044,198) discloses a process for producing cellulose derivatives, preferably cellulose ethers, having a high proportion of purity. Here, the moist cellulose derivatives are brittle by liquid nitrogen and then comminuted.

DE-B 24 58 998 (= US-A 4,076,935) and related further application DE-B 25 58 821 relates to a method for finely grinding cellulose or its derivatives, more particularly ether. Grinding is carried out with a water content of 5 to 14% by weight as long as the particle size is almost 100 µm and the residual water is almost 2 to 10% by weight. Vibratory mills are used for this purpose.

EP-A 0 049 815 (= US-A 4,415,124) discloses a two-stage method for producing fine powders from cellulose ethers or cellulose, in which products having structures such as fine fibers or wool are first broken up. The material is easily converted to a solidified form and pretreated in this way until the particle size distribution reaches at least 90% below 125 μm. Preferably, the cooling design, or at the stage where the vibration mills or ball mills of pellet presses are brittle, pinned disk mills or impact disk mills (impact disk mills) are used in the grinding stage.

DE-A 14 54 824 discloses a process for producing granules or powders from fibrous dry cellulose ethers by friction between two rolls at different rotational speeds and subsequent milling. .

DE-A 30 32 778 relates to a two stage process for the continuous homogenization of moist cellulose ethers, wherein the moist cellulose ether is obtained by rotating rotary elements with various side profiles. It is subjected to beating and shearing, and optionally, water is added to simultaneously pellet the decomposed cellulose ethers and the resulting pellets are subsequently dried.

Known methods according to the prior art are many stage methods which are mostly pre-drying or pre-friable or pre-compact and require a high cost for the device, for example due to intensive cooling. Moreover, in the case of all methods, the chemical and / or thermal stress of the particulates is still too high, especially when treating highly substituted, highly viscous products, especially in viscosity compared to the products in which the particulates during grinding are used. It is destroyed in terms of chain reduction, which is manifested by larger or smaller decompositions. In addition, the surfaces of the treated products are cured due to pre-fragmentation or pre-drying steps that indicate undesirable for the rapid and complete decomposition properties required by the customer.

It is an object of the present invention that, by the optimal setting of grinding and drying parameters, ranges of larger grinding degrees can be set, the apparent density of the ground material can be further increased, and the proportion of excessively large materials is significantly reduced. It is possible to further improve the process known from EP-B 0 370 447 so that the viscosity of the decomposed pulverized material compared to the original material to be pulverized is only small or no reduction. The present invention is also intended to have the effect of reducing the energy introduced and increasing the overall processing efficiency.

The purpose is

a) the gas stream is divided into three partial gas streams,

b) a first partial gas stream carrying material to be crushed is introduced into the milling and friction space of the mill to decompose the material to be crushed,

c) a second partial gas stream is introduced tangentially into the space between the mill housing and the friction space,

d) the third partial gas stream takes and further conveys the decomposed and dried ground pulverized material exiting the mill by the first and second partial gas streams,

e) the milled material is separated from the three partial gas streams that come together to form a complete gas stream,

f) Complete gas flow is achieved according to the invention, which is filtered and optionally returned and reused.

In an improvement of the method, the first partial gas flow constitutes 20 to 35 volume percent of the gas flow, the second partial gas flow constitutes 15 to 20 volume percent and the third partial gas flow comprises 50 to 65 volume percent Configure

The process is carried out so that the initial moisture of the cellulose ether is 20 to 70% by weight and the final or residual moisture is 1 to 10% by weight.

The method introduces a material into which the first partial gas stream is to be crushed into a pulverization space for impingement decomposition, circulates the material to be pulverized, and simultaneously simultaneously frictions into a friction space in a direction in which the impulse crushed material is moved against the circulation direction. It is designed to pulverize, to flow around the outside of the friction space in the direction in which the second partial gas stream moves in reverse, and to contribute to moisture-controlled pulverized material with temperature-controlled and / or desired residual moisture.

Another procedure following the method is characterized by the features of claims 5-10.

An apparatus for carrying out the method includes a main gas line connected to a gas flow source connected to the outlet line and separator of the mill through a heating and temperature control register, the first gas line branching from the main gas line and metering for the material to be ground. It is distinguished by the fact that a second gas line, connected to a metering line, to a mill on the input side, and equally connected to a mill on the input side, diverges from the first gas line.

In an improvement of the apparatus, a reducing damper for adjusting the gas pressure in the main gas line is arranged in the main gas line between the branch of the first gas line and the output of the mill. Likewise, the reducing damper in the second gas line regulates the gas pressure.

In the refinement of the apparatus, in the separator, the decomposed pulverized material can be separated from the complete gas flow and an outlet line for complete gas flow from the separator is connected to a gas flow source and a return line is connected to the condenser and the Gas flow is circulated.

The grinder has, for convenience, a beater wheel equipped with a plurality of beater bars and a screening cage arranged concentrically with and surrounding the beater wheel, the screen cage being partitioned in circumference. Tooth pieces arranged adjacent to each other and friction plates attached to the support screens, wherein the support screens are provided with holes and the distance between the screen cage and the inner wall of the grinder housing is 12-30 mm.

Another refinement of the device is characterized by the features of claims 16-23.

The present invention provides that the complete gas stream is divided into three partial gas streams, and the complete gas stream has a particle diameter of the pulverized, dried and pulverized material by the simple means of controlling the flow rate and the amount of partial flows to desired values. It realizes the advantage that it can be set very accurately.

The invention is explained in detail below with reference to the drawings.

As shown in FIG. 1, the gas flow source 32 operated at the suction side supplies a gas flow which is divided into three gas streams, behind the heating resistor, through the heating resistor 22. For this purpose, the first gas line 24 branches from the main gas line 23 and is connected to a metering line 36 for the material to be ground. From the first gas line 24 also branches a second gas line 25 which is connected to the mill 26 on the input side. The material to be ground is fed to a metering bunker 27 and passed through a metering line 36 through which a rotary feeder 28 is located via a speed adjusting screw conveyor. As described above, in order for the material to be crushed in the mill 26, the first gas line 24 for the first partial gas flow is connected to the metering line 36 on the rotary feeder 28. The second gas line 25 for the second partial gas flow is connected in a tangential direction to the mill housing 26 and to regulate the gas pressure of the second partial gas flow, which does not carry any material to be polished. And a reducing damper (29).

In the main gas line 23 which carries the third partial gas flow, the reducing damper 34 for adjusting the gas pressure in the main gas line 23 is via the outlet line 37 and the main gas line 23. Disposed between the output of the mill 26 connected to the branch of the first gas line 24. The milled material to be decomposed and dried in the mill 26 is brought by the first and second partial gas streams which flow through the outlet line 37 to the main gas line 23, where the three sections The gas streams are brought back together to form a complete gas stream which, in turn, transfers the dried and cracked ground material in the main gas line 23 to the separator 30. In the separator 30, the decomposed crushed material is separated from the complete gas stream and discharged through the rotary feeder 31 at the output of the separator 30 for further use. Separator 30 also has an outlet line for complete gas flow to which gas flow source 32 is connected. The return line 35, shown in broken line in FIG. 1, connects the gas flow source 32 to the condenser 33, and the moisture introduced into the condenser can be removed from the clean gas stream and the complete gas flow is Can be returned to the circuit. Of course, it is also possible for the return to be omitted in order to be able to omit the return line 35 and the condenser 33. In this case, the cleaned gas stream, which is generally an air stream, exits into the atmosphere.

In the schematic cross-sectional view of the mill 26 of FIG. 2, a metering line 36 is shown for the material to be milled, which line is the drive shafts 7, 8 for the screen cage 4 and the beater wheel 2, respectively. Is approximately centered with respect to the housing 1 at a height of. In this schematic view, the material to be crushed brought to the mill 26 is circled in the metering line 36 and introduced into the screen cage 4. The decomposed and crushed material leaving the screen cage 4 is represented by circles of smaller dimensions than the material to be crushed brought inside. Decomposed and crushed material is discharged through an outlet 10 located at the bottom of the crusher 26. The grinder 26 has devices 17 for controlling the temperature of the grinder and the screen cage 4. The direction of rotation of the beater wheel and screen cage is indicated by arrows.

3 shows a schematic cross-sectional side view of a grinder 26 for impingement-frictional decomposition of a material to be ground. In the housing 1 is arranged a beater wheel with radial beating arms at the end which is rotated by the drive shaft 8 and on which the beater bar 3 is arranged. The screen cage 4 is arranged concentrically with respect to the beater wheel 2, and the screen cage is attached on the drive shaft 7 which drives the screen cage in a direction moving in opposition to the beater wheel. The two drive shafts 7, 8 are driven by a motor (not shown), for example via a toothed belt. The screen cage is prefabricated from the toothed pieces 5 and the friction plates 6 provided with inlet holes. As already described with respect to FIG. 2, the material to be comminuted and the first partial gas stream are brought to the screen cage 4 centrally through the metering line 36, while the second partial gas stream is passed through the inlet 9. It flows tangentially into the space between the inner wall of the housing 1 and the screen cage 4. The second partial gas stream does not convey any material to be ground to the mill.

The material to be crushed introduced into the screen cage 4 by the first partial gas flow is circulated and decomposed by the beater bars 3 of the beater wheel 2. In the opposite direction to the circulation direction, the impact-decomposed crushed material is also decomposed by the teeth of the tooth piece 5 and the friction plates 6. The second partial gas flow flows around the screen cage 4 in a direction that moves in opposition to the rotational movement of the beater wheel 2 and controls the ground material to the desired residual moisture of temperature control and / or 1 to 10% by weight. It contributes to moisture and cleans product particles that adhere to the housing. The initial moisture of the cellulose ether is in the range of 20 to 70% by weight when the cellulose ether enters the mill 26.

The three partial flows of the complete gas stream comprise the first partial gas stream of 20 to 35 volume percent, the second partial gas stream of 15 to 20 volume percent, and the third partial gas flow of 50 to 65 volume percent. Split to make up%. Before being divided into three partial gas streams, the gas stream is heated or temperature controlled by heating or temperature control register 22 from 14 to 25 ° C. to 60 to 200 ° C., as described above, the second and third parts. The gas pressure of the gas streams is regulated by reducing dampers 29 and 34, respectively. In order to set the desired final or residual moisture of the decomposed ground material, the water content of the ground material is added to the temperature control of the three partial gas flows by the device 17 of the mill 26 (see FIG. 2). Can be adjusted. For this purpose, the devices 17 are arranged in the screen cage 4 and the housing 1, but the parts of the screen cage 4, for example the toothed pieces 5 or the friction plates 6, are directly heated. Alternatively, a temperature controlled solution can be envisioned. Similarly, it is conceivable to control or heat the temperature of the parts of the beater wheel 2, for example the beater bars 3.

The apparatus is preferred for grinding cellulose ethers from the group of methyl, hydroxyethyl, hydroxypropyl and carboxymethyl celluloses and mixtures thereof, but likewise other materials can be dried simultaneously with grinding. The cellulose ethers that are ground and dried have a viscosity of 5000 to 500,000 mPas measured in a 1.9% aqueous solution (measured by the Hoplen method).

4 shows that the metering line 36 is connected to the side inlet hole 13 on the housing of the grinder 26, the inlet hole 13 being located at the height of the drive shafts 7, 8 shown in FIG. 3, That is, the side view arrange | positioned coaxially with respect to these drive shafts is shown.

The second gas line 25 is connected to the upper inlet, or inlet connecting piece 9, on the housing 1, and the second partial gas flow passes through this second gas line 25 to the inner side of the housing 1. Flows into the space between and the screen cage (4). First part gas flow with disintegrated pulverized material, second part, through outlet 10 (see FIGS. 2 and 3) and outlet line 37 (see FIG. 1) provided at the bottom of housing 1. Gas flows to the main gas line 23, where they are sent to the separator 30.

The beater wheel 2 rotates at a circumferential speed of 50 to 93 m / s, and the rotating screen cage 4, which moves in reverse, rotates at a circumferential speed of 20 to 52 m / s.

5 shows a part of the screen cage 4 shown in an enlarged view. The screen cage 4 consists of toothed pieces 5 arranged in the circumferential direction and friction plates 6 attached to the support screen 12, and, like the friction plates 6, the teeth of the toothed piece 5. Is pointing towards the inside of the screen cage. Holes 11 are formed in the support screen 12. The friction plates 6 have a thickness of 0.75 to 2.0 mm and have a length of 0.12 to 0.8 mm and an entrance hole of the same width as that length. In the case of another embodiment of the friction plates 6, the width is 0.15 to 0.5 mm, while the length is 0.12 to 2 mm. The support screens 12 have outwardly bent ends 14 supporting the inclined surfaces 15 of the toothed pieces 5. The clamping parts: 16 surround the ends 14 and the tooth pieces 5 and are bolted to the tooth pieces. The tooth length is 1 to 10 mm.

The thickness of the support screens 12 is in the range of 4 to 8 mm and the holes 11 have a diameter of 15 to 20 mm. The areas between the holes have a width of at least 4-5 mm.

The method and apparatus according to the invention provide, with respect to the method and apparatus according to EP-B 0 370 447, faster drying of the ground material and consequently increased throughput of the ground material through the device without a decrease in viscosity. throughput).

1 is a block diagram of an apparatus according to the invention.

FIG. 2 is a side sectional view of a grinder which is a component of the device according to FIG.

3 is a schematic cross-sectional view of the grinder according to FIG. 2;

4 shows line sections for the mill and partial gas flow;

5 shows in section, the screen cage part of the grinder, seen from the side;

* Description of the symbols for the main parts of the drawings *

1 housing 2 beater wheel

4 screen cage 7, 8 drive shaft

22: heating resistor 23: main gas line

24: first gas line 25: second gas line

26: grinder 28: rotary feeder

30: separator

Claims (23)

A method for simultaneously pulverizing and drying a material to be ground comprising wet cellulose ether, a) the gas stream is divided into three partial gas streams, b) a first partial gas stream conveying the material to be crushed is introduced into the milling and friction space of the mill to decompose the material to be crushed, c) a second partial gas stream is introduced tangentially into the space between the mill housing and the friction space, d) a third partial gas stream takes and further conveys the decomposed and dried ground material discharged out of the mill by the first and second partial gas streams, e) the milled material is separated from the three partial gas streams coming together to form a complete gas stream, f) The complete gas stream is filtered and optionally returned and reused. The method of claim 1, wherein the first partial gas flow constitutes 20 to 35 volume percent of the gas flow, the second partial gas flow constitutes 15 to 20 volume percent and the third partial gas flow is 50 to Pulverization and drying method comprising 65% by volume. The method of claim 1, wherein the initial moisture of the cellulose ether is 20 to 70% by weight and the final or residual moisture is 1 to 10% by weight. The method of claim 1, wherein the first partial gas flow introduces the material to be crushed into a pulverization space for impact reduction, the material to be pulverized and the impact-pulverized material with respect to the circulation direction. Simultaneously friction-pulverized in the frictional space in the opposite direction of movement, the second partial gas flow flows around the outside of the frictional space in the opposite direction of movement and is subject to temperature control or to the moistureization of the ground material with the desired residual moisture. A method of grinding and drying, which contributes to, or contributes to, both and cleans the product particles that adhere to the housing. The gas stream of claim 1, wherein before being divided into the three partial gas streams, the gas stream is heated or temperature controlled from 14 to 25 ° C. to a temperature of 60 to 200 ° C. Pressure controlled, grinding and drying method. The grinding and drying method according to claim 4, wherein the rotation speed in the grinding space is 50 to 93 m / s and the rotation speed moving in the friction space is 20 to 52 m / s. 6. The method of claim 5 wherein the moisture content is adjusted in addition to the temperature control of the three partial gas streams to set the degraded ground material to the desired residual moisture. The method of claim 1, wherein the grinding space and the friction space or portions of these spaces can be heated or their temperature controlled. The method of claim 1 wherein the cellulose ether having a viscosity of 5000 to 500,000 mPas, as measured in a 1.9% aqueous solution, is ground and dried. 10. The method of claim 9, wherein the cellulose ether is selected from the group of methyl, hydroxyethyl, hydroxypropyl, and carboxymethyl celluloses and mixtures thereof. In an apparatus for carrying out the method of any one of the preceding claims, the main gas line (23) connected to the gas flow source (32) is the outlet of the mill (26) through a heating and temperature control register (22). A line 37 and a separator 30, a first gas line 24 is connected to a metering line 36 for the material to be branched and comminuted from the main gas line and A second gas line (25) connected to the input side, the second gas line (25) equally connected to the input side of the grinder (26) branches from the first gas line (24). A reducing damper (34) for regulating the gas pressure in the main gas line (23) is provided with a branch of said first gas line (24) and said discharge line (37). The main gas line (23) between the connection with the main gas line (23). 12. The apparatus of claim 11, wherein a reducing damper (29) in the second gas line (25) regulates the gas pressure. 12. The process according to claim 11, wherein in the separator (30), the decomposed crushed material can be separated from the complete gas stream, and an outlet line for the complete gas flow discharged from the separator (30) is provided for the gas flow source (32). And a return line (35) is connected to a condenser (33), and the gas stream is circulated. 12. The beater wheel (2) according to claim 11, wherein the grinder (26) has a beater wheel (2) having a plurality of beater bars (3) and is arranged concentrically with respect to the beater wheel (2). Has a screening cage (4), which screen cage (4) is partitioned circumferentially and the friction plates (6) attached to the support pieces (12) and the supporting screens (12) arranged adjacent to each other. The support screens 12 are provided with holes 11 and the distance between the screen cage 4 and the inner wall of the housing 1 of the grinder 26 is 12-30 mm, Device. The screen cage (4) and the beater wheel (2) according to claim 15, wherein the metering line (36) is adapted to introduce the first partial gas stream which transfers the material to be crushed to the screen cage (4). Device connected to a side inlet hole (13) disposed in the housing (1) coaxially with respect to the drive shafts (7, 8). The method of claim 15, wherein the second gas line 25 is in the housing 1 to introduce the second partial gas flow into the space between the inside of the housing 1 and the screen cage 4. Device connected to the upper inlet hole (9). The first partial gas stream and the second partial gas stream together with the disintegrated pulverized material form an outlet hole (10) and an outlet line (37) provided in the bottom of the housing (1). Device through the main gas line (23). Device according to claim 15, wherein the beater wheel (2) rotates at a circumferential speed of 50 to 93 m / s and the screen cage (4) rotates at a circumferential speed of 20 to 52 m / s. 16. The clamping parts (10) according to claim 15, wherein the support screens (12) have inclined outwardly bent ends (14) for supporting the inclined surfaces (15) of the tooth pieces (5). 16 includes the ends 14 of the support screens 12 supporting them, surrounds the tooth pieces 5, is bolted to the tooth pieces 5, and A tooth having a length of 1 to 10 mm. The device according to claim 15, wherein the friction plates 6 have a thickness of 0.75 to 2.0 mm and have inlet holes having a length of 0.12 to 2.0 mm and a width of 0.12 to 2.0 mm or a width of 0.15 to 0.5 mm. . 16. The support screen (12) according to claim 15, wherein the support screens (12) have a thickness of 4 to 8 mm, the holes (11) have a diameter of 15 to 20 mm, and the areas between the holes have a minimum of 4 mm. A device having a width. Device according to claim 15, wherein in the mill (26) there are devices (17) for controlling the temperature of the housing (1), the beater wheel (2) or the screen cage (4).

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