AU2019280943B2

AU2019280943B2 - Device for residual-monomer removal

Info

Publication number: AU2019280943B2
Application number: AU2019280943A
Authority: AU
Inventors: Takahiro Chiyoda; Hiromasa MIZUTA; Norihisa SANO
Original assignee: JNC Corp
Current assignee: JNC Corp
Priority date: 2018-06-07
Filing date: 2019-06-05
Publication date: 2024-06-13
Anticipated expiration: 2039-06-05
Also published as: AU2019280943A1; KR102772933B1; TW202012461A; CN111918884A; JPWO2019235504A1; WO2019235504A1; CN111918884B; KR20210018991A

Abstract

A device for residual-monomer removal by which residual monomers can be efficiently removed from a slurry containing a vinyl-chloride-based resin, while preventing the residual monomers from being discharged from the process. The device for residual-monomer removal comprises: a column body 4; a plurality of perforated plates 34 disposed along the vertical direction within the column body; a plurality of chambers 16-21 formed respectively over the perforated plates serving as bottom surfaces; slurry introduction pipes 22 and 23; flow pipes 36 for causing the slurry to flow downward successively from the perforated plate beneath an upper chamber; a steam introduction pipe 10 disposed in the bottom part of the column body; a condenser 6 disposed over the upper part of the column body, with a gas discharge port 11 disposed therebetween; a slurry discharge port 24 provided to the lowermost perforated plate; and warm-water ejectors disposed just beneath the perforated plates and each including a warm-water ejection ring 38. Each warm-water ejector is provided with: a pressure gauge 40 for monitoring the ejection pressure to effectively conduct the ejection; a device for adjusting the pressure (a pressure control valve 32 or a warm-water pump 8 with inverter control); and a sight-glass-washing nozzle 37 connected to the upper part of the warm-water ejection ring 38 of the warm-water ejector or inserted into the ring.

Description

DEVICE FOR RESIDUAL-MONOMER REMOVAL

Technical Field

[0001] The present invention is related to a device and a method for residual-monomer

removal from a slurry containing a vinyl chloride resin (hereinafter, abbreviated as PVC),

which can efficiently remove residual monomers mainly including a vinyl chloride

monomer (hereinafter, abbreviated as VCM) or the like contained in a mixture of PVC

and an aqueous medium (hereinafter, abbreviated as PVC slurry) during the manufacture

of PVC.

Related Art

[0002] Because PVC is a resin having excellent chemical and physical properties, it is

used in a wide range of fields. Generally, PVC is produced by a suspension

polymerization method, an emulsion polymerization method, a bulk polymerization

method or the like. Due to an advantage that a reaction heat can be easily removed and

a product with a small amount of impurities can be obtained, the suspension

polymerization method and the emulsion polymerization method are widely used

particularly.

[0003] The suspension polymerization method and the emulsion polymerization

method are usually performed by adding VCM together with an aqueous medium, a

dispersant or an emulsifier, a polymerization initiator and the like into a polymerization

vessel equipped with a stirrer, and polymerizing while stirring at a predetermined

temperature. Normally, the polymerization reaction is not carried out up to 100%

conversion of VCM to PVC, and is stopped at the stage of good production efficiency,

that is, the stage of polymerization conversion of 80 to 95%. After the completion of

the polymerization reaction, the residual monomer in the polymerization vessel is separated from the PVC slurry (mainly a mixed dispersion of PVC particles and the aqueous medium) and recovered, but it is normal that there is several percent of residual monomers in the PVC slurry.

[0004] Thus, the PVC slurry containing the residual monomer is mechanically removed

of the aqueous medium, and is dried by hot air drying and other various methods to be

PVC powder. At this time, the separated aqueous medium, the exhaust caused by hot

air drying and the obtained PVC powder contain VCM which is a problem for

environmental hygiene reasons or is apparently harmful.

[0005] Various methods have been proposed in order to completely remove the VCM

in production effluents and in PVC powder or to reduce the content of the VCM to an

environmentally harmless level. For example, patent literature 1 and patent literature 2

disclose methods that remove and recover the residual monomer from the PVC slurry by

using a processing column provided with a plurality of perforated plate shelves inside and

a steam injection port at the bottom.

[0006] In the methods above, the perforated plate shelves are used, each of which has

a bottom surface consisted of a perforated plate and is provided with dam plates so as to

form a processing path in a zigzag pattern on the perforated plate, and the PVC slurry is

caused to successively flow downward along the processing path on the perforated plate

shelves; in the meantime, the PVC slurry is exposed to the steam injected from below

through pores of the perforated plate to evaporate and separate the residual monomer

contained in the PVC slurry.

[0007] In general, the method of removing and recovering the residual monomer is

called a monomer removal method, and the monomer removal method occupies the

mainstream at present.

A device for residual-monomer removal based on the monomer removal method

has hot water ejection devices respectively disposed directly below the perforated plate

of each chamber or at least disposed toward the undersurface of the perforated plate.

While the PVC slurry is successively flowing downward along the processing path on the

perforated plate, due to a decrease in system temperature or a change in steam flow, the

slurry may drop from holes of the perforated plate to the chamber below and the PVC

may be clogged in the holes, or the slurry may scatter and adhere to wall surfaces because

of pressure fluctuations in the chamber. When left as it is, the holes of the perforated

plate are blocked and the blowing of the steam becomes non-uniform, resulting in

unstable operation and insufficient removal of the residual-monomer in the PVC slurry.

Further, the PVC adhered to the wall surface is discolored by heat and has a bad influence

on the quality as foreign matter contamination. The hot water ejection by the hot water

ejection device can wash away the slurry adhere to the holes and the wall surfaces of the

perforated plate, and thus the problems above are prevented.

[0008] As described above, the hot water ejection device of the device for residual

monomer removal is an important device, and the hot water ejection device and the

method have been proposed in, for example, patent literature 2.

[0009] Furthermore, in recent years, a device for residual-monomer removal as in

patent literature 3 to 5 has been proposed which includes: a column body that is

cylindrical; a plurality of perforated plates disposed along the vertical direction of the

column body; a plurality of chambers formed respectively above the perforated plates

serving as bottom surfaces; slurry introduction ports disposed above the uppermost

perforated plate among the plurality of perforated plates; flow-down parts disposed

between the perforated plates so as to cause the slurry to flow downward successively from the perforated plate of the upper chamber to the perforated plate of the lower chamber; a steam introduction port disposed at the bottom of the column body; a condensation device disposed outside the column body through a gas transfer pipe in the top chamber of the column body; a slurry discharge port disposed on the lowermost perforated plate among the plurality of perforated plates; and hot water ejection devices disposed directly below the perforated plates or at least disposed toward the undersurfaces of the perforated plates.

[0010] Among the above, it is necessary to maintain the hot water ejection pressure of

each chamber in order to ensure an appropriate amount of hot water ejection during hot

water ejection cleansing. As for the pressure, an opening degree is adjusted with a

manual valve in order that an indicated value of a pressure gauge connected to a hot water

ejection nozzle disposed at the inlet of each chamber become a predetermined pressure.

However, the predetermined pressure may not be ensured due to fluctuations in the outlet

pressure of a hot water pump.

[0011] In addition, when the operation state of the device for residual-monomer

removal is regularly checked or the operation becomes unstable, in order to visually check

the slurry level and bubbling state in each chamber, sight glass is disposed on the side

surface of each chamber and the interior can be observed. However, the scattered slurry

may adhere to the sight glass, making it difficult to see the interior of each chamber.

Thus, a cleansing nozzle for cleansing the sight glass is connected from a hot water

ejection ring. However, the cleansing nozzle is connected from the lower side of the

hot water ejection ring, therefore, even the hot water ejection cleansing is completed, the

hot water drips from the sight glass cleansing nozzle and hits the sight glass until the hot

water in the hot water ejection ring is drained, and thus the interior of each chamber cannot be observed until the hot water in the hot water ejection ring is drained.

[0012] Furthermore, when the temperature difference between the temperature inside

the chamber and the temperature of the hot water is large, the temperature inside the

chamber fluctuates and the pressure also fluctuates during cleansing, so that liquid

leakage may occur at the perforated plate above or below the chamber.

[Literature of related art]

[Patent literature]

[0013] Patent literature 1: Japanese Patent Laid-Open No. 54-8693

Patent literature 2 Japanese Patent Laid-Open No. 56-22305

Patent literature 3 Japanese Patent Laid-Open No. 6-107723

Patent literature 4 Japanese Patent Laid-Open No. 10-338708

Patent literature 5 Japanese Patent Laid-Open No. 9-48815

SUMMARY

[Problems to be Solved]

[0014] A device for residual-monomer removal is required which can prevent residual

monomers from being discharged from the process and efficiently remove the residual

monomers from a slurry containing a vinyl chloride resin.

[Means to Solve the Problems]

[0015] The configuration of the device for residual-monomer removal of the present

invention is as follows. The device for residual-monomer removal includes: a column

body 4 that is cylindrical; a plurality of perforated plates 34 disposed along the vertical

direction within the column body; a plurality of chambers 16 to 21 formed respectively

above the perforated plates serving as bottom surfaces; slurry introduction pipes 22, 23; flow-down pipes 36 for causing the slurry to flow downward successively from the perforated plate of the upper chamber; a steam introduction pipe 10 disposed at the bottom of the column body; a condenser 6 disposed over the upper part of the column body through a gas discharge port 11; a slurry discharge port 24 disposed on the lowermost perforated plate; and hot water ejection rings 38 directly below the perforated plates.

Hot water ejection devices each including a warm water ejection ring is each provided

with a pressure gauge 40 for monitoring the ejection pressure to effectively perform the

ejection, a device for adjusting the pressure (a pressure control valve 32 or a hot water

pump 8 with inverter control function), and a sight glass cleansing pipe 37 connected

from the upper part of the hot water ejection ring 38 of the hot water ejection device or

inserted into the ring.

[0016] To solve the above problem, the present invention includes the following items.

[1] A device for residual-monomer removal, which efficiently removes residual

monomers from a slurry containing a polyvinyl chloride that includes the residual

monomers after completion of polymerization, including:

a column body that is cylindrical;

a plurality of perforated plates disposed along the vertical direction of the

column body;

a plurality of chambers formed respectively above the perforated plates serving

as bottom surfaces;

slurry introduction ports disposed above the uppermost perforated plate among

the plurality of perforated plates;

flow-down parts disposed between the perforated plates so as to cause the slurry

to flow downward successively from the perforated plate of the upper chamber to the perforated plate of the lower chamber; a steam introduction port disposed at the bottom of the column body; a condensation device disposed outside the column body through a gas transfer pipe in the top chamber of the column body; a slurry discharge port disposed on the lowermost perforated plate among the plurality of perforated plates; and hot water ejection devices disposed directly below the perforated plates or at least disposed toward the undersurfaces of the perforated plates; wherein each hot water ejection device is provided with a pressure gauge for monitoring the ejection pressure and a device for controlling the ejection pressure to eject the hot water at an appropriate ejection amount.

[0017] [2] The device for residual-monomer removal according to [1], wherein the

device for controlling the ejection pressure is a device which controls a pressure control

valve or a hot water supplying pump output with an inverter to adjust the hot water

ejection pressure.

[0018] [3] The device for residual-monomer removal according to [1] or [2], wherein

the hot water ejection ring provided in the hot water ejection device has a cleansing nozzle

for cleansing sight glasses disposed at one or more places in each chamber.

[0019] [4] The device for residual-monomer removal according to [3], wherein the

cleansing nozzle of the hot water ejection ring for cleansing the sight glasses is connected

from the upper side of the hot water ejection ring.

[0020] [5] The device for residual-monomer removal according to [3], wherein the

in a manner of being inserted into the hot water ejection ring.

[Effect]

[0021] According to the invention described in [1] or [2], the device for removing

residual monomers from a slurry containing a polyvinyl chloride and including the

residual monomers after completion of polymerization is provided. In order to set the

ejection pressure in the hot water ejection device to a predetermined pressure, the hot

water ejection pressure can be adjusted by installing a pressure control valve or

controlling the output of a hot water pump with an inverter. In addition, it also leads to

energy saving by using the inverter.

[0022] According to the invention described in [3], by disposing the cleansing nozzle

for cleansing the sight glass of each chamber in the hot water ejection ring provided in

the hot water ejection device, the internal condition of each chamber can be observed.

[0023] According to the invention described in [4] or [5], the cleansing nozzle of the

hot water ejection ring for cleansing the sight glass is a nozzle inserted from the lower

side or is connected from the upper side of the hot water ejection ring, so that it is possible

to observe the internal condition of each chamber without waiting for the hot water

accumulated in the hot water ejection ring to be drained from the cleansing nozzle.

Further, by storing the hot water in the hot water ejection ring, the difference between the

temperature inside the chamber and the temperature of hot water in the hot water ejection

ring becomes smaller, so that the pressure fluctuation inside the chamber is relaxed, which

leads to the prevention of liquid leakage from the perforated plate.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] FIG. 1 is a schematic diagram of a device for residual-monomer removal.

FIG. 2 is a detailed diagram showing the interior of a chamber of a processing column for residual-monomer removal.

FIG. 3 is an enlarged vertical sectional view of a hot water ejection ring.

FIG. 4 is an overall view of the hot water ejection ring seen from above.

FIG. 5 is a vertical sectional view of a sight glass cleansing pipe connected from

the upper part of the hot water ejection ring.

FIG. 6 a vertical sectional view of the sight glass cleansing pipe inserted and

connected from the lower part of the hot water ejection ring.

DESCRIPTION OF THE EMBODIMENTS

[0025] A method for removing residual monomers from a PVC slurry in a device for

residual-monomer removal of the present invention is described based on FIG. 1 to 6, but

the present invention is not limited thereto.

[0026] 1. Configuration of the device for residual-monomer removal

The device includes: a column body 4 that is cylindrical; a plurality of perforated

plates 34 disposed along the vertical direction of the column body 4 and having a large

number of pores respectively; a plurality of chambers 16 to 21 formed respectively above

the perforated plates serving as bottom surfaces; slurry introduction ports 22, 23 serving

as slurry introduction parts, disposed above the perforated plate below the column-top

chamber 21 or the perforated plate below the chamber 19 among the plurality of

perforated plates; flow-down pipes 36 disposed between the perforated plates so as to

cause the slurry to flow downward successively from the perforated plate of the upper

chamber to the perforated plate of the lower chamber; a steam introduction pipe 10

disposed at the bottom of the column body; a condenser 6 disposed at the top of the

column body through a gas discharge port 11; a residual monomer gas transfer pipe 12 disposed at the outlet of the condenser; a PVC slurry discharge port 24 disposed on the lowermost perforated plate among the plurality of perforated plates; and hot water ejection rings 38 serving as hot water ejection units, disposed directly below each perforated plate and disposed toward directly below of the perforated plate.

[0027] 1-1. Column body

The inner diameter of the column body 4 is 200 to 10000 mm, and the height of

the column is 2 to 20 times, more preferably 5 to 15 times with respect to the inner

diameter. Further, if necessary, the inner diameter of each chamber in the column may

be different. In the processing column for residual-monomer removal 4, the space

delimited by the bottom of the column and the perforated plate, by the perforated plate

and the perforated plate located directly above it, or by the perforated plate and the top of

the column is called a chamber. The number of the chamber required for processing the

residual monomer is determined by the residence time which is required during the

removal of the residual monomer from the PVC slurry.

[0028] 1-2. Perforated plate

The perforated plates 34 having a large number of pores are provided with

several dam plates 35 vertically on the surface of each of the perforated plates 34, and the

chamber (space) is formed between the perforated plate 34 and the undersurface of the

upper perforated plate. The pores of the perforated plate are opened so that when the

PVC slurry flows on the perforated plate, the monomer removal processing is performed

by the steam injected from the pores. The size of the pores is set in consideration of the

steam pressure and the steam introduction amount in order that the PVC slurry does not

flow down through the pores and does not obstruct the pores, and the steam injected from

below passes through the pores constantly and uniformly.

[0029] The pores opened in the perforated plate have a diameter of 5 mm or less,

preferably 0.5 to 2 mm, more preferably 0.7 to 1.5 mm. In addition, the aperture ratio

(total area of pores/area of perforated plate) of the perforated plate is 0.001 to 10%,

preferably 0.04 to 4%, more preferably 0.2 to 2%.

When the aperture ratio is within the range above, PVC particles existing in the

PVC slurry flowing on a perforated plate shelf are sufficiently stirred, so that it is possible

to prevent the deterioration of the efficiency of the residual-monomer removal from the

PVC particles and the deterioration of the fluidity of the PVC slurry caused by the

precipitation of the PVC particles. Further, when the aperture ratio is within the range

above, the phenomenon of the PCV slurry flowing down from the pores (hereinafter

referred to as liquid leakage) does not occur, and because the liquid leakage can be

prevented, there is no waste of a large amount of steam for liquid leakage prevention.

The dam plates 35 serve to ensure a processing path through which the PVC

slurry can flow on the perforated plates. The dam plates are alternately disposed on the

upper surface of the perforated plates 34, and the PVC slurry flows on the perforated shelf

for a certain period of time through the processing path formed by the dam plates, and

during that time, the PVC slurry is subjected to the monomer removal processing

performed by the steam supplied from below.

[0030] 1-3. Hot water ejection device

In addition, hot water ejection devices are disposed in the column body 4 of the

device for residual-monomer removal of the present invention. Each of the hot water

ejection rings 38 serving as the hot water ejection devices forms a pipe into a

predetermined shape (FIG. 4) and is disposed directly below the perforated plate 34.

The hot water ejection ring 38 ejects hot water from an ejection nozzle at a predetermined time interval to wash the undersurface of the perforated plate and the inner wall of the column. The number of the ejection nozzle and the position of nozzle holes 39 are not particularly limited, and it is preferable that intersection angles a, b (FIG. 3) of the ejection nozzles with respect to a vertical line are set within the range of 10 to 60 degrees.

In order to give a sufficient ejection speed and cleansing power to the hot water,

it is appropriate that the pressure difference between the pressure in the hot water ejection

ring during the ejection of the hot water and the pressure in the chamber for ejecting the

hot water is 0.02 MPaG or more, preferably 0.05 MPaG or more. When the pressure

difference is within the range, the pressure control of the hot water ejection in which a

sufficient cleansing effect is obtained with no increase of the hot water consumption is

realized by converting a hot water pump 8 into an inverter to automatically control the

hot water circulation line pressure or to automatically control a pressure control valve 32.

[0031] 1-4. Sight glass cleansing pipe

It is appropriate that a cleansing pipe 37 of a sight glass 33 is connected from

the upper part of the hot water ejection ring 38 as shown in FIG. 5 or is inserted and

connected from the lower part of the hot water ejection ring 38 as shown in FIG. 6.

When the cleansing pipe is connected from the lower side of the hot water ejection ring,

because the hot water remaining in the hot water cleansing ring drips from a sight glass

cleansing nozzle and hits the sight glass even the cleansing is completed, the inside of the

chamber cannot be observed. Further, when the temperature difference between the

temperature inside the chamber and the temperature of the hot water is large, the

temperature inside the chamber fluctuates and the pressure also fluctuates during the

cleansing, so that liquid leakage may occur at the perforated plate above or below the

chamber. When the hot water is stored in the hot water ejection ring by connecting the sight glass cleansing pipe from the upper part of the hot water ejection ring or inserting and connecting the sight glass cleansing pipe from the lower part of the hot water ejection ring, the temperature difference between the temperature inside the chamber and the temperature of the hot water in the ring becomes smaller, so that the liquid leakage of the perforated plate is prevented.

[0032] 1-5. Hot water ejection ring

The planar shape of the pipe of the hot water ejection ring 38 serving as the hot

water ejection device is usually like a Greek letter Q or (D of, a spiral shape, a star shape

or a sheep intestine type (zigzag), and the shape may be a multiple ring shape (FIG. 4) in

which the centers are alternately set to be the same. The hot water ejection ring 38 may

be disposed parallel to the perforated plate 34 and stored inside the column. However,

when the hot water ejection ring 38 is too close to the inner wall of the column body, PVC

particles washed away or the like may block the gap. Therefore, the hot water ejection

ring 38 may be disposed in a position where the outer diameter of the hot water ejection

ring is at a distance of 20 mm or more inward from the inner wall of the column. The

outer diameter of the hot water ejection ring 38 is preferably 150 to 8000 mm.

[0033] 2. Method for removing residual-monomer from PVC slurry

The PVC slurry obtained by suspension polymerization or emulsion

polymerization and temporarily stored in a PVC slurry tank 1 is introduced into a heat

exchanger 3 by a PVC slurry feed pump 2 and heated to a predetermined temperature in

the heat exchanger 3, and then is introduced into the processing column for residual

monomer removal 4 from a PVC slurry introduction pipe 22 or 23.

[0034] The flow rate of the PVC slurry introduced into the column is preferably

adjusted to 0.1 to 300 m3 /h (more preferably 1 to 100 m3 /h) per square meter of the perforated plate 34. It is desirable that the PVC slurry introduced into the column is preheated to 50 to 100C by the heat exchanger 3. The efficiency of the residual monomer removal is improved by the preheating.

The difficulty degree of removing the monomer from the PVC slurry is

determined by the structure of the PVC particles in the PVC slurry. When the pore

volume ratio of the PVC particles is large, the contact between the PVC particles and the

steam is good and it is easy to remove the monomer. When the pore volume ratio is

small, it is difficult to remove the monomer. The residence time of the PVC slurry in

the column is determined by the described difficulty degree of the monomer removal from

the PVC slurry, the concentration of unreacted monomer contained in the PVC slurry

introduced into the column, and the set value of the concentration of the processed

residual monomer at the PVC slurry discharge port 24.

[0035] When the residence time of the PVC slurry in the column is long, the residual

monomer can be highly removed from the PVC particles existing in the PVC slurry.

However, when the residence time is too long, the coloration is caused in the PVC

particles due to thermal degradation. Therefore, it is not preferable that the contact of

the PVC slurry and the steam is more than necessary. Thus, it is necessary to adjust the

residence time in accordance with the difficulty degree of the monomer removal from the

PVC slurry.

[0036] The PVC slurry introduced into the column body from the slurry introduction

pipe 22 or 23 serving as the slurry introduction part passes through the processing path

defined by the dam plates 35 on the perforated plate 34, and is introduced into the

perforated plate 34 of the lower chamber through the flow-down pipe 36. Then, the

slurry introduced onto the perforated plate 34 passes through the processing path on the perforated plate 34 and further flows through the flow-down pipe 36 to flow onto the perforated plate 34 below. After passing through the processing path to the lowermost perforated plate 34, the PVC slurry is discharged to the outside of the column from the

PVC slurry discharge port 24 disposed on the lowermost perforated plate 34.

[0037] In the perforated plate 34 of the present invention, the number of the dam plate

35 and the width of the processing path are not particularly limited. However, because

the liquid height of the flowing PVC increases and exceeds the dam plate, the PVC

slurries having different residence times are mixed. Therefore, in order to prevent the

quality of the product from being deteriorated, it is necessary to appropriately set the

number of the dam plate and the width of the processing path.

In the device of the present invention, the steam introduction pipe 10 is

connected to the column-bottom chamber 15, and the steam ejected from the steam

introduction pipe 10 is blown through the pores of the perforated plate into the PVC slurry

flowing on the perforated shelf. The amount of steam introduction at the time is 1 to

100 Kg/h, preferably 5 to 50 Kg/h per cubic meter of the PVC slurry. Whentheamount

of steam introduction is within the range above, the residual monomer in the PCV slurry

can be efficiently removed without the precipitation of the PVC particles in the PVC

slurry. Further, when the amount of steam introduction is within the range above, the

occurrence of splashing of the PVC slurry is suppressed and no flooding occurs.

Further, when the amount of steam introduction is within the range above, the amount of

steam introduction and the effect of removing the residual monomer in the PVC slurry

are well balanced.

[0038] In addition, adjusting the temperature of the PVC slurry leads to obtaining of

high quality PVC. In general, it is desirable to adjust the temperature of the steam, the amount of steam introduction, and the internal pressure of the column, in order that the temperature of the slurry flowing on the perforated plate becomes 50 to 150°C, preferably

70 to 120°C, and more preferably 80 to 110°C. When the temperature of the PVC slurry

is within the range above, the removal efficiency of the residual monomer can be

maintained and the coloration or the like of the PVC particles caused by thermal

degradation can be prevented and a high quality can be maintained.

[0039] A mixed gas of the monomer gas removed in the device for residual-monomer

removal and the steam flows into the condenser 6 through the gas transfer pipe connected

to the column-top chamber 21, most of the steam is condensed in the condenser, and the

condensed water is dropped back into the processing column for residual-monomer

removal. At that time, the mixed gas of the monomer gas and the steam rising from the

column-top chamber comes into countercurrent contact with the condensed water flowing

down, and the condensed water is heated. Further, energy loss can be prevented by

introducing cooling water 13, which has been introduced into the condenser 6, from the

condenser 6 to a hot water tank 7 through a cooling water outlet and hot water supplying

pipe 14, then using the water as the hot water for hot water cleansing. The PVC slurry

from which the residual monomer has been removed by the processing column for

residual-monomer removal 4 is discharged from the slurry discharge port 24 and fed into

a pump 9. Then, the PVC slurry is stored in the PVC slurry tank through the heat

exchanger3.

Example

[0040] Next, the present invention is specifically described with reference to examples

below, but the present invention is not limited thereto.

[0041] The hot water ejection process using the hot water ejection device in the processing column for residual-monomer removal is carried out during the PVC slurry feed and during the cleansing water feed after the completion of the PVC slurry feed.

In addition, the hot water ejection cleansing is performed in order from the lower

chamber 16 to the upper chamber. When the cleansing of the column-top chamber is

completed, the cleansing is started again from the chamber 16. With regard to the

chamber 15, when a hot water ejection cleansing valve 31 of the column-bottom chamber

is opened to perform the hot water ejection cleansing during the PVC slurry feed, the

temperature inside the chamber 15 decreases and the pressure inside the chamber also

decreases, and the liquid leakage from the upper perforated plate is caused, so that the hot

water ejection cleansing is not performed during the PVC slurry feed.

[0042] [Example 1]

(Hot water ejection pressure control by inverter control of hot water pump output)

1. The hot water pump 8 is started, and the inverter output is set to a minimum

value of 100 m3 /h, which is a circulation amount at which the temperature distribution in

the hot water tank 7 is uniformly maintained.

2. One minute before the hot water ejection, the hot water circulation line

pressure is set in order that the pressure difference between the hot water ejection pressure

and the pressure inside the chamber is an appropriate value of 0.05 MPaG to 0.08 MPaG,

and the inverter output of the hot water pump is automatically controlled.

3. The inverter output control of the hot water pump 8 is switched to the manual

mode, and the output value is fixed at the output value at the time of switching. Then,

the hot water ejection cleansing valve 30 of the chamber 16 is opened for 8 seconds.

4. After the hot water ejection cleansing valve 30 is closed, the inverter output

of the hot water pump 8 is returned to the minimum value of 100 m3 /h, which is the circulation amount at which the temperature distribution in the hot water tank 7 is uniformly maintained, and the state is maintained for 2 to 10 minutes.

5. By the same operation as the above 2 to 4, the hot water ejection cleansing

valve 29 on one shelf is opened/closed to wash the lower side of the perforated plate under

the chamber 17 and the chamber 18.

6. By repeating the same operation as the above 2 to 5, the hot water ejection

cleansing is performed in order from the lower chamber to the upper chamber.

[0043] [Example 2]

(Hot water ejection pressure control by control of circulation pressure control valve)

1. The hot water pump 8 is started, and the opening degree output of the

circulation pressure control valve 32 is fully opened.

2. One minute before the hot water ejection, the hot water circulation line

and the pressure inside the chamber is an appropriate pressure, and the opening degree

output of the circulation pressure control valve 32 is automatically controlled.

3. The circulation pressure control valve 32 is switched to the manual mode, and

the opening degree output value is fixed. Then, the hot water ejection cleansing valve

30 of the chamber 16 is opened for 8 seconds.

4. After the hot water ejection cleansing valve 30 is closed, the opening degree

output of the circulation pressure control valve 32 is fully opened. The state is

maintained for 2 to 10 minutes.

5. By the same operation as the above 2 to 4, the hot water ejection cleansing

valve 29 on one shelf is opened/closed to cleanse the lower side of the perforated plate

under the chamber 17 and the chamber 18.

6. By repeating the same operation as the above 2 to 5, the hot water ejection

cleansing is performed in order from the lower chamber to the upper chamber.

[0044] [Example 3]

(Cleansing in sight glass cleansing pipe connected from the upper part of hot water

ejection ring)

The cleansing of the sight glass 33 in each chamber is performed at the same

time when the hot water ejection cleansing in each chamber is performed. Because the

sight glass cleansing pipe is connected from the upper part of the hot water ejection ring,

when the hot water ejection cleansing is completed, the hot water will never drip from the

sight glass cleansing nozzle. Further, because the hot water is stored in the hot water

ejection ring, the temperature difference between the temperature inside the chamber

during cleansing and the temperature of the hot water in the ring is reduced to 1°C or less,

and the liquid leakage of the perforated plate does not occur.

[0045] [Example 4]

(Cleansing in sight glass cleansing pipe inserted and connected from the lower part of hot

water ejection ring)

As in the example 3, when the hot water ejection cleansing is completed, the hot

water will never drip from the sight glass cleansing nozzle. Further, the liquid leakage

of the perforated plate does not occur.

[0046] [Comparison example 1]

In the conventional method, in order to ensure an appropriate hot water ejection

pressure during the hot water ejection cleansing, a pressure gauge and a manual valve are

disposed at the inlet of the hot water ejection ring disposed at each chamber inlet, and the

opening degree is adjusted with the manual valve in order that the indicated value of the pressure in each chamber becomes a predetermined pressure of 0.05 MPaG to 0.08

MPaG. However, due to fluctuations in the outlet pressure of the hot water pump, the

predetermined pressure may not be ensured. Furthermore, in the hot water circulation

line, in order to ensure the pressure of hot water circulation, an automatic valve for shutoff

is necessary for a circulation return line. When each chamber is cleansed, the hot water

ejection cleansing automatic valve in each chamber is opened and the hot water

circulation shutoff valve is closed. However, due to the timing of opening and closing

the valve, a pipe is hammered, which sometimes causes vibration of the pipe and the valve

and causes leakage of the hot water from the flange of the pipe or the valve.

[0047] [Comparison example 2]

As for conventional sight glass cleansing, the sight glass cleansing pipe was

connected to the lower side of the hot water ejection ring. Therefore, even the hot water

ejection cleansing was completed, the hot water dripped from the sight glass cleansing

nozzle and hit the sight glass and the interior of the chamber could not be observed, until

the hot water in the hot water ejection ring was completely drained. Further, depending

on the chamber, the temperature difference between the interior of the chamber and the

hot water in the ring is as large as 5°C or more, so that liquid leakage of the perforated

plate occurred during the hot water ejection cleansing.

[Industrial Applicability]

[0048] The device for residual-monomer removal of the present invention can be used

in a manufacture device of the vinyl chloride resin.

[Reference Signs List]

[0049] 1 PVC slurry tank

2 PVC slurry feed pump

3 heatexchanger

4 processing column for residual-monomer removal

5 PVC slurry tank

6 condenser

7 hot water tank

8 hot water pump

9 pump

10 steam introduction pipe

11 gas discharge port

12 residual monomer gas transfer pipe

13 cooling water

14 cooling water outlet and hot water supplying pipe

15 bottom chamber of column

16 to 20 chamber

21 column-top chamber

22,23 PVC slurry introduction pipe

24 PVC slurry discharge port

25 to 30 hot water ejection cleansing valve

31 hot water ejection cleansing valve of column-bottom chamber

32 hot water circulation pressure control valve

33 sight glass (same number for each chamber)

34 perforated plate (same number for each chamber)

35 dam plate (same number for each chamber)

36 flow-down pipe (same number for each chamber)

37 sight glass cleansing pipe (same number for each chamber)

38 hot water ejection ring (same number for each chamber)

39 nozzle hole

40 pressure gauge

Claims

WHAT IS CLAIMED IS:

1. A device for residual-monomer removal, which efficiently removes

residual monomers from a slurry containing a polyvinyl chloride that comprises the

residual monomers after completion of polymerization, comprising:

a column body that is cylindrical;

a plurality of perforated plates disposed along the vertical direction of the

column body;

a plurality of chambers formed respectively above the perforated plates

serving as bottom surfaces;

slurry introduction ports disposed above an uppermost perforated plate among

the plurality of perforated plates;

flow-down parts disposed between the perforated plates so as to cause the

slurry to flow downward successively from the perforated plate of an upper chamber to

the perforated plate of a lower chamber;

a steam introduction port disposed at the bottom of the column body;

a condensation device disposed outside the column body through a gas transfer

pipe in the top chamber of the column body;

a slurry discharge port disposed on a lowermost perforated plate among the

plurality of perforated plates; and

hot water ejection devices disposed directly below the perforated plates and at

least disposed toward undersurfaces of the perforated plates;

wherein each hot water ejection device is provided with a pressure gauge for

monitoring an ejection pressure and a device for controlling the ejection pressure to eject

the hot water in an appropriate ejection amount.

2. The device for residual-monomer removal according to claim 1, wherein

the device for controlling the ejection pressure is a device which controls a pressure

control valve or a hot water supplying pump output with an inverter to adjust the hot water

ejection pressure.

3. The device for residual-monomer removal according to claim 1 or 2,

wherein

a hot water ejection ring provided in the hot water ejection device has a

cleansing nozzle for cleansing sight glasses disposed at one or more places in each

chamber.

4. The device for residual-monomer removal according to claim 3, wherein

the cleansing nozzle of the hot water ejection ring for cleansing the sight glasses is

connected from the upper side of the hot water ejection ring.

5. The device for residual-monomer removal according to claim 3, wherein

connected in a manner of being inserted into the hot water ejection ring.