JP2000312839A - Method for unloading fibrous cake from upright centrifugal separator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To smoothly unload a fibrous cake by making the fibrous cake residing on the inner peripheral face of a porous basket flow out of a discharging aperture through blowing a specific cleaning solution to the fibrous cake at a specific range of flow velocity, while the porous basket is rotated. SOLUTION: A stock fibrous solution is supplied into a porous basket 1 from a supply nozzle 12 in such a state that a bottom lid 5 is closed, and a liquid component contained in the stock fibrous solution is separated to the outside of the porous basket 1 by rotating the porous basket 1 at a high velocity. Thus a fibrous cake 9 is made to stick to and reside on the inner peripheral face of the porous basket 1. Further, 0.2-5.0 m3/hr cleaning solution per 1 kg (dry weight) fibrous cake 9 residing on the inner peripheral face of the porous basket 1, are blown at a flow velocity of 7-50 m/sec to the sticking fibrous cake 9 from a basket cleaning nozzle 7, while the porous basket 1 is rotated. Consequently, the residing fibrous cake 9 is made to flow out of a discharging aperture 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing fibrous cake remaining in a vertical centrifuge equipped with a perforated basket having an outlet at the bottom.

[0002]

2. Description of the Related Art Conventionally, a vertical centrifuge equipped with a perforated basket has been widely used as a method for separating and recovering, for example, a liquid and / or a solid content (cake) from a slurry. The cake remaining on the inner peripheral surface of the perforated basket of this vertical centrifuge is generally removed by a scraping knife.

[0003] Further, instead of using a scraping knife (scraper) alone, an air nozzle is provided on the scraping knife, and the cake is scraped off with the scraping knife until a predetermined thickness is reached. It is also known to exfoliate (U.S. Patent No. 3002090).

[0004]

However, when the cake is taken out by a general scraping knife, the cake is easily damaged by frictional heat generated by rubbing with the scraping knife and mechanical external force, and the cake to be taken out is disassembled. There is a problem of causing quality deterioration including the above. Further, in order to avoid contact between the scraping knife and the perforated basket, there is a problem that some clearance must be provided between the scraping knife and the perforated basket, and cake remains.

[0005] On the other hand, even when an air nozzle is used in combination, the same effect as described above exerts adverse effects on the cake due to frictional heat and mechanical external force when scraping with a scraping knife. There is a problem that the recovery is not complete and the cake tends to dry.

[0006] The above-mentioned problem occurs even when the solid content is particulate, but it is particularly significant in the case of a fibrous cake containing a fibrous solid content. In other words, in the case of a fibrous cake, the solid content has a greater resistance to the scraping knife than the particulate cake and the amount of heat generated by friction tends to increase, and the fibrous solid content is increased by rubbing with the scraping knife. Is easily entangled in a pill shape, and the quality is likely to be greatly deteriorated. For example, if the fibrous cake is a nitrocellulose cake, an increase in the amount of frictional heat and drying of the cake will increase the risk of operation. In addition, the entanglement of the fibrous solids hinders smooth removal and degrades the quality, and the cake residue may lead to an accident if left unattended.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has been described in connection with the removal of a fibrous cake remaining in a vertical centrifuge having a perforated basket having a discharge port at the bottom thereof. It is an object of the present invention to be able to take out a fibrous cake smoothly without causing entanglement of fibrous solids.

[0008]

That is, the present invention provides a method for removing a fibrous cake remaining in a vertical centrifuge having a perforated basket having a discharge port at the bottom.
For the fibrous cake remaining on the inner peripheral surface of the perforated basket, a cleaning liquid of 0.2 to 5.0 m ³ / hour per 1 kg of the dry weight of the fibrous cake remaining on the inner peripheral surface of the perforated basket, A method for removing a fibrous cake from a vertical centrifugal separator, characterized in that the perforated basket is rotated and sprayed at a flow rate of 7 to 50 m / sec to flow out from an outlet.

[0009] The present invention also relates to a method of moving a cleaning liquid spraying position from a lower part to an upper part of a perforated basket, spraying the cleaning liquid separately on the bottom of the perforated basket, and using a nitrocellulose fibrous cake. Is included as a preferred embodiment thereof.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a vertical centrifuge used in the method of the present invention will be described with reference to FIG.

In the figure, reference numeral 1 denotes a perforated basket housed in a casing 2, which is connected to a drive shaft 3 located at the center by a rib 4, and is rotated with the rotation of the drive shaft 3. It has become. In the center of the bottom of the perforated basket 1, a discharge port 6 that can be opened and closed by a bottom cover 5 is provided. The drive shaft 3 extends upward from the inside of the outlet 6, and the rib 4 is located in the outlet 6 so as to straddle between the drive shaft 3 and the bottom of the perforated basket 1.

Above the perforated basket 1, there is provided an elevating device 8 for moving the basket washing nozzle 7 up and down. The basket washing nozzle 7 is used for the perforated basket 1
When the fibrous cake 9 remaining on the inner peripheral surface of the basket 1 is taken out, the cleaning liquid is sprayed on the fibrous cake 9 to separate the fibrous cake 9, and the tip is bent toward the inner peripheral surface of the perforated basket 1. It is composed of tubing. When removing the fibrous cake 9, an auxiliary cake discharge nozzle 10 for spraying a cleaning liquid onto the bottom surface of the perforated basket 1 and a rib cleaning nozzle 11 for spraying the cleaning liquid to the rib 4 are provided with the basket cleaning nozzle 7. Similarly, it is provided so as to be able to move up and down.

Reference numeral 12 denotes a supply nozzle for supplying the raw fibrous solution to be processed into the perforated basket 1. In the illustrated vertical centrifuge, the drive shaft 3 is connected to the discharge port 6.
A drive motor (not shown) for rotationally driving the drive shaft 3 is of an upper type in which the drive shaft 3 extends upward from the inside. It can also be of the underside type, extending and with the drive motor located below.

Next, a method of removing the fibrous cake 9 from the vertical centrifuge will be described.

With the basket washing nozzle 7, the cake discharge auxiliary nozzle 10 and the rib washing nozzle 11 in the raised position, and with the bottom cover 5 closed, the fibrous stock solution (for example, nitrocellulose slurry) is supplied from the supply nozzle 12. Is supplied into the perforated basket 1 and the perforated basket 1 is rotated at a high speed, the liquid component contained in the undiluted fibrous liquid is separated out of the perforated basket 1, and the inner surface of the perforated basket 1 has a fibrous cake. 9 adheres and remains.

During the centrifugal drainage, the bottom lid 5 is closed, and the bottom lid 5 is opened when the fibrous cake 9 is taken out by spraying a cleaning liquid from the basket washing nozzle 7 described later. Considering only the efficiency, the bottom lid 5
Alternatively, centrifugal dewatering can be performed without providing the bottom lid or with the bottom cover 5 open.

According to the present invention, the removal of the fibrous cake 9 is not carried out by a conventional scraping knife, but the bottom cover 5 is opened and at least the basket washing nozzle 7 is inserted into the perforated basket 1. Lower it,
The cleaning is performed by spraying the cleaning liquid on the fibrous cake 9 to peel the fibrous cake 9 and to flow out from the outlet 6 at the bottom.

The cleaning liquid blown from the basket washing nozzle 7 to the fibrous cake 9 is a liquid different from the liquid contained in the undiluted fibrous liquid before centrifugation, and the centrifuged fibrous cake can stably exist. Things are used.
Specifically, it is selected according to the fibrous stock solution, but for example, water or alcohol can be used.

The cleaning liquid is sprayed from the basket washing nozzle 7 to the fibrous cake 9 at a flow rate of 0.2 per kg of the dry weight of the remaining fibrous cake 9.
It is necessary that the flow rate is 7 to 50 m / sec at 〜5.0 m ³ / hour. If the flow rate is too small or the flow rate is too small, the fibrous cake 9 is difficult to peel without loosening and remaining, and if the flow rate is too large or the flow rate is too large,
It easily peels and falls at once with a large lump. The spraying of the cleaning liquid promotes smooth outflow of the fibrous cake 9 at a flow rate of 0.4 to 3.0 m ³ / hour per 1 kg of the dry weight of the remaining fibrous cake 9, and 13 to 3
It is preferable to carry out at a flow rate of 0 m / sec.

The cross-sectional shape of the basket washing nozzle 7 for spraying the cleaning liquid is preferably such that the cleaning liquid can be ejected in a circular or elliptical rod shape in cross section. The direction in which the cleaning liquid is sprayed from the basket washing nozzle 7 is such that the fibrous cake 9 adhering to the inner peripheral surface of the perforated basket 1 is easily peeled off by loosening an appropriate amount. The angle is preferably perpendicular (90 °) to downward 45 ° with respect to the vertical direction, and is preferably 0 ° to 45 ° opposite to the rotation direction of the perforated basket 1.

The removal of the fibrous cake 9 is carried out by moving the basket washing nozzle 7 in the vertical direction while slowly rotating the perforated basket 1, thereby changing the spraying position of the cleaning liquid. The moving direction of the basket washing nozzle 7 (moving direction of the spraying position) may be any of a top-to-bottom direction and a bottom-to-top direction. However, the attached fibrous cake 9 is scraped off little by little and smoothly discharged. It is preferable to perform the process from below to above. The raising and lowering of the basket washing nozzle 7 is preferably performed using an air pressure or hydraulic cylinder, but may be performed by other means.

When removing the fibrous cake 9, one or both of the cake discharge auxiliary nozzle 10 and the rib cleaning nozzle 11 are lowered into the perforated basket 1, and are also sprayed from the basket cleaning nozzle 7. It is preferable to spray the same cleaning liquid as the cleaning liquid to be obtained. The cake discharge auxiliary nozzle 10 sprays a cleaning liquid onto the bottom surface of the perforated basket 1.
Of the fibrous cake that has been peeled off from the inner peripheral surface and dropped onto the bottom surface can be promoted to the discharge port 6. The rib cleaning nozzle 11 sprays a cleaning liquid to the rib 4 located in the discharge port 6. By spraying the cleaning liquid from the rib cleaning nozzle 11 to the rib 4, the fibrous cake 9 is sprayed. Can be prevented from remaining on the ribs 4.

Further, the bottom surface of the perforated basket 1 is inclined in the direction of the discharge port 6 to promote the movement of the fibrous cake 9 to the discharge port 6 or to protrude to the inner peripheral edge of the perforated basket 1. It is also preferable to provide a spray nozzle (not shown) for spraying a cleaning liquid on the top plate so that the residue of the fibrous cake attached to the top plate can be removed by washing.

The present invention is used in a batch type vertical centrifuge equipped with a perforated basket having a discharge port at the bottom. In the non-porous basket type, the product cake is only settled and separated, and the undiluted solution is not subjected to defiltration filtration. Therefore, a step of separately removing the undiluted solution is required, which is inefficient. In the case of the vertical type, in which the stock slurry is supplied and the product cake is discharged from the upper part of the basket, both the supply of the stock slurry and the discharge of the product cake are performed from the upper part of the basket. The slurry needs to be overflowed from the top or to be separately discharged by a suction pump or the like, which is extremely inefficient.

The present invention is applied to the removal of a fibrous cake containing a fibrous material such as cellulose, and is particularly effective for separating and recovering nitrocellulose, which is highly dangerous.

[0026]

Next, the present invention will be described more specifically with reference to examples and comparative examples.

Example 1 A perforated basket having an outlet at the bottom (inner diameter 485 m)
1.7 kg of nitrocellulose (NC) in a dry state using a vertical centrifuge equipped with
Supply the slurry, rotate the perforated basket at 1500 rpm, and shake off the stock solution consisting of nitric acid and sulfuric acid.
35-50 NC cakes with a liquid content of about 1 kg / dry NC
It was attached to the inner peripheral surface of a perforated basket with a thickness of mm.

6 m installed at 35 ° downward with respect to the vertical direction of the inner peripheral surface of the perforated basket, and at 0 ° facing the rotation direction.
Using a basket washing nozzle having a circular cross section of mφ, the nozzle was moved upward from below with the bottom cover opened, and the NC cake was taken out using water as a cleaning liquid under the following conditions.

-Basket washing nozzle flow rate: 1.7 m ³
/ H (1.0 m ³ / h per kg of dried NC cake) ・ Basket washing nozzle flow rate: 17 m / sec ・ Basket washing nozzle rising speed: 2 mm / sec ・ Auxiliary nozzle for discharging cake: circular cross section, 25 mmφ, direction vertically downward , Flow rate 4.2m ³ / hour ・ Rotation speed of perforated basket at removal: 25 rotations / minute

The NC cake adhering to the inner peripheral surface of the perforated basket was loosened little by little by the water jet spouted from the basket washing nozzle, dropped to the bottom, and discharged as a water slurry from the discharge port. There was no residual residue in the perforated basket.

Comparative Example 1 Using the same centrifuge as in Example 1, N
C cake was deposited.

Clearance 5 with inner peripheral surface of perforated basket
mm, a scraping knife with a flat plate edge having a contact width of 45 mm with the NC cake was installed, and the scraping knife was moved upward from below with the bottom cover opened.
The C cake was scraped off.

· Raising speed of scraping knife: 1.8 mm /
Seconds • Basket rotation speed during scraping: 75 rotations / minute

[0034] The scraping knife scraped the NC cake while loosening it, but the scraped NC cake became a ball of ball. In addition, it peeled off at a stretch, and the ball-shaped NC cakes became entangled with each other to form a lump, and a part thereof could not be discharged. A small amount of cake remains on the inner wall of the perforated basket,
The ball-like cake was also entangled on the shaft of the scraping knife and remained.

Comparative Example 2 Using the same centrifuge as in Example 1, N
C cake was deposited.

The basket was washed with the bottom cover opened using a 2 mmφ circular basket washing nozzle installed at 0 ° perpendicular to the vertical direction of the inner peripheral surface of the perforated basket and in the direction of rotation. The nozzle was moved upward from below, and the cake was scraped off using water as a cleaning liquid under the following conditions.

・ Basket washing nozzle flow rate: 0.2 m ³
/ H (0.12m ³ / h / kg of dried NC cake) ・ Basket washing nozzle flow rate: 18m / sec ・ Basket washing nozzle descending speed: 2mm / sec ・ Auxiliary nozzle for discharging cake: circular section, 25mmφ, direction vertically downward , Flow rate 4.2m ³ / hour ・ Rotation speed of perforated basket at removal: 25 rotations / minute

The NC cake adhering to the inner peripheral surface of the perforated basket was loosened by the water flow spouting from the basket washing nozzle, but it was difficult to completely isolate the NC cake from the inner wall of the perforated basket, and some residual was generated. did. Although the safety effect was enormous as compared with the scraping knife method, it was slightly insufficient in preventing residual cake.

Example 2 The same centrifugal separator as in Example 1 was used.
7 kg of NC slurry is supplied, and the stock solution composed of nitric acid and sulfuric acid is shaken off at 1500 rpm to obtain a liquid content of about 1 kg /.
An NC cake of dry NC was attached to the inner peripheral surface of the perforated basket at a thickness of 35 to 50 mm.

The basket washing nozzle having a circular cross section of 6 mmφ and having a circular cross section of 6 mm and installed at 15 ° perpendicular to the vertical direction of the inner circumferential surface of the perforated basket and in the direction of rotation and opposed to the rotating direction, with the bottom lid open, is used for washing the basket. The nozzle was moved downward from above, and the NC cake was taken out using water as a cleaning liquid under the following conditions.

-Basket washing nozzle flow rate: 1.7 m ³
/ H (1.0 m ³ / h per kg of dried NC cake) ・ Basket washing nozzle flow rate: 17 m / sec ・ Basket washing nozzle descending speed: 1 mm / sec ・ Auxiliary nozzle for discharging cake: circular cross section, 25 mmφ, direction vertically downward , Flow rate 4.2m ³ / hour ・ Rotation speed of perforated basket at discharge: 25 rotations / minute

The NC cake adhering to the inner peripheral surface of the perforated basket was loosened by the water jet spouted from the basket washing nozzle, but swelled and peeled off to the NC cake adhering to the lower part, sometimes dropped in a lump and temporarily moved to the bottom. Stayed. The NC cake temporarily staying at the bottom was also discharged from the discharge port by water sprayed from the discharge auxiliary nozzle,
It was found that the movement of the basket washing nozzle was more likely to prevent the NC cake from staying from below to above than from above to below.

Comparative Example 3 Using the same centrifuge as in Example 1, an NC cake was adhered under the same conditions as in Example 2.

Clearance 5 with inner peripheral surface of perforated basket
mm, a scraping knife with a flat plate edge having a contact width of 45 mm with the NC cake was installed, and with the bottom cover opened, the scraping knife was moved from top to bottom under the following conditions.
The C cake was scraped off.

· Raising speed of scraping knife: 1.8 mm seconds · Rotation speed of perforated basket during scraping: 75 rotations / minute

The scraping knife scraped off the NC cake while loosening it, but the scraped NC cake turned into a thread ball. In addition, the ball-like cakes became entangled with each other to form a lump, and it was difficult to partially discharge the cake. A small amount of NC cake remained on the inner peripheral surface of the perforated basket, and a thread ball-shaped NC cake was also entangled on the shaft of the scraping knife and remained.

Example 3 A perforated basket having an outlet at the bottom (inner diameter 1060 m)
m, depth 570 mm), 24 kg of NC slurry was supplied in a dry state using a vertical centrifuge having
The stock solution consisting of nitric acid and sulfuric acid is shaken off at 0 revolutions / minute, and the NC cake having a liquid content of about 1 kg / dry NC is 35 to 70 mm.
And attached to the inner peripheral surface of the perforated basket.

16 mmφ which is set at 45 ° perpendicular to the vertical direction of the inner peripheral surface of the perforated basket and in the direction of rotation.
Using a basket washing nozzle having a circular cross section, the basket washing nozzle was moved upward from below with the bottom cover opened, and the cake was taken out using water as a cleaning liquid under the following conditions.

· Basket washing nozzle flow rate: 12 m ³ /
Hour (0.5 m ³ / h per kg of dried NC cake) ・ Basket washing nozzle flow rate: 17 m / sec ・ Basket washing nozzle ascending speed: 5 mm / sec ・ Auxiliary nozzle for discharging cake: circular cross section, 40 mmφ, direction vertically downward, Flow rate 18m ³ / h ・ Rib washing nozzle: circular cross section, 25mmφ, direction is vertically downward, flow rate 5m ³ / h ・ Perforated basket rotation speed at removal: 10 rotations / min

The NC cake adhering to the inner peripheral surface of the perforated basket was loosened little by little by the water jet ejected from the basket washing nozzle and dropped to the bottom, and was discharged as a water slurry from the discharge port. There was no residual residue in the perforated basket.

Example 4 A perforated basket having an outlet at the bottom (1220 m inside diameter)
m, 600 mm deep) on the bottom plate toward the outlet.
Using a vertical centrifuge with a gradient of ゜, supply 21 kg of purified cotton linter (CL) slurry in a dry state and shake off the acidic water at 800 rpm to obtain a liquid content of about 1 kg / dry CL. Was attached to the inner peripheral surface of the perforated basket in a thickness of 35 to 50 mm.

A 16 mmφ set at 45 ° perpendicular to the vertical direction of the inner peripheral surface of the perforated basket and in the direction of rotation.
Using a basket washing nozzle having a circular cross section, the basket washing nozzle was moved upward from below with the bottom lid opened, and the CL cake was taken out using water as a cleaning liquid under the following conditions.

· Basket washing nozzle flow rate: 10 m ³ /
Hour (0.48 m ³ / h per kg of dried CL cake) ・ Basket washing nozzle flow rate: 14 m / sec ・ Basket washing nozzle ascending speed: 8 mm / sec ・ Auxiliary nozzle for discharging cake: circular cross section, 45 mmφ, direction vertically downward, Flow rate 24m ³ / h ・ Rotation speed of perforated basket at removal: 11 rotations / min

The CL cake adhering to the inner peripheral surface of the perforated basket was loosened little by little by the water jet ejected from the basket washing nozzle, dropped to the bottom, and discharged as a water slurry from the discharge port. There was no residual residue in the perforated basket.

Example 5 The same centrifugal separator as in Example 4 was used.
kg of NC slurry is supplied at 800 rpm.
The stock solution composed of sulfuric acid was shaken off, and an NC cake having a liquid content of about 1 kg / dry NC was attached to the inner peripheral surface of the perforated basket in a thickness of 35 to 50 mm.

The bottom of the perforated basket was opened with the bottom lid opened by using a basket washing nozzle with a circular cross section of 16 mmφ, which was installed at 0 ° and perpendicular to the vertical direction of the inner peripheral surface of the perforated basket and in the direction of rotation. And the washing nozzle were moved upward from below, and the NC cake was taken out using water as a cleaning liquid under the following conditions.

-Basket washing nozzle flow rate: 6.0 m ³
/ H (0.25m ³ / h per kg of dried NC cake) ・ Basket washing nozzle flow rate: 8m / sec ・ Basket washing nozzle descending speed: 8mm / sec ・ Auxiliary nozzle for discharging cake: circular cross section, 45mmφ, direction vertically downward , Flow rate 24m ³ / hour Perforated basket rotation speed at removal: 11 rotations / min

The NC cake adhering to the inner peripheral surface of the perforated basket was loosened by the water jet spouted from the basket washing nozzle, but the peeling from the perforated basket was somewhat delayed. The peeled NC cake is smoothly moved to the discharge port by water from the cake discharge auxiliary nozzle,
There was no residual residue in the perforated basket.

[0059]

The centrifugal separator according to the present invention uses a method of scraping off the liquid from the basket washing nozzle, so that there is no frictional heating or damage of the cake and no cake remains in the basket tank. It is a centrifuge. In particular, a fibrous cake was difficult to discharge by a scraping knife method, but has been made possible by the present invention.

[Brief description of the drawings]

FIG. 1 is a schematic vertical sectional view of a vertical centrifuge used in the method of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 perforated basket 2 casing 3 drive shaft 4 rib 5 bottom lid 6 outlet 7 basket washing nozzle 8 elevating device 9 fibrous cake 10 cake discharge auxiliary nozzle 11 rib washing nozzle 12 supply nozzle

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Tatsuo Yamashita 6-4100 Asahicho, Nobeoka-shi, Miyazaki F-term (reference) in Asahi Kasei Kogyo Co., Ltd. 4D057 AA00 AB01 AC02 AC05 AD01 AE02 AF01 BA36 BC11

Claims (4)

[Claims] When removing the fibrous cake remaining in a vertical centrifuge provided with a perforated basket having a discharge port at the bottom, the fibrous cake remaining on the inner peripheral surface of the perforated basket is removed. 0.2 to 5.0 m ³ / kg of dry weight of fibrous cake remaining on the inner peripheral surface of the hole basket
The cleaning liquid at the time is rotated 7 to 50 while rotating the perforated basket.
A method for removing a fibrous cake from a vertical centrifuge, wherein the fibrous cake is blown out at a flow rate of m / sec and discharged from an outlet. 2. The method for removing a fibrous cake from a vertical centrifuge according to claim 1, wherein the spraying position of the cleaning liquid is moved from a lower portion to an upper portion of the perforated basket. 3. The method for removing a fibrous cake from a vertical centrifuge according to claim 1, wherein the cleaning liquid is sprayed separately also on the bottom of the perforated basket. 4. The method for removing a fibrous cake from a vertical centrifuge according to claim 1, wherein the fibrous cake is a nitrocellulose cake.