DD140204A5 - GAS FLUID CONTACT TOWER AND THAT WITH CONTACT - Google Patents

Abstract

The invention will be applied to a liquid containing the sedimenting solid and the volatile matter, starting from the object of increasing the economy without major technical and economic effort The task is to facilitate a very effective gas-liquid contact with low pressure drop and to prevent settling and depositing of sedimenting solid to facilitate cleaning options and to allow a thermally quality-sparing treatment, As a solution, a contact tower and the associated method is proposed. The slurry is poured from above into a padded contact tower and the scrubbing gas is blown into the bottom as it makes an acute angle through the slanting slits At least a portion of the slurry flowing on the slanted areas of the slabs becomes dispersive and so on A mixed gas-liquid or gas-solid-liquid phase forms. The gas directed in the new direction accelerates the slurry and connects a standstill. - Fig. 4 - ••• SS 24 pages ISi triggers IKT ^ Ie. (δßß) A «141 / 78-79 3.

Description

-A-

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Gas-liquid contact tower and the method practicable with the contact tower.

field of use

The invention relates to a gas-liquid contact tower for removing a volatile substance from a liquid containing it or a slurry containing sedimenting solid and the volatile substance, in particular a contact tower for removing monomeric vinyl chloride from a monomeric vinyl chloride-containing PVC slurry. Further, the invention relates to the process of removing a volatile substance from a liquid or slurry containing it, the sedimenting solid and the volatile matter.

Characteristic of the known technical solutions

There are already known gas-liquid contact towers. The floors used in these contact towers, each of which consists of several floor slabs and one fall plate, establish the contact between the gas and the liquid. For application reach z. Bubble trays, trays, and valve trays. "When a slurry contains the substantial amount of solid matter with a gas in it

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a tower in contact with these floors, the plague body tends to settle or precipitate on the floors or elsewhere in the tower.

The method of gas-liquid contact is effected in that the gas rises upward by a sedimenting liquid which is dammed by an overflow.

These towers and the associated method have the disadvantage that a time-consuming / difficult and difficult cleaning process is required by the deposition of the solid on the floors. Therefore, it is not easy to change the feed stream of one slurry of a stock system by a feed stream of a slurry of another stock system in a short time without concomitant loss of solid and thermal degradation of the deposited solid. It is therefore not only difficult, but also very uneconomical, a slurry containing a sedimenting solid (such a liquid or slurry will hereinafter be referred to simply as "sediment liquid") using a gas-liquid contact tower with the usual trays. In addition, the settling of the solid on the trays reduces the fluidity of the slurry.

Object of the invention

The aim of the invention is to increase the economics without major technical and economic effort

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To facilitate cleaning options and to enable a thermally quality-saving treatment.

Statement of the invention

The object of the invention is to provide a gas-liquid contact tower and the method practicable with this contact, which works self-cleaning and in which a very effective gas-liquid contact with low pressure drop arises and thereby a volatile substance from a liquid containing them or is removed from a slurry containing the volatile and sedimenting solids without settling and settling of the sedimenting solid.

According to the invention the object is achieved in that each bottom plate is formed so that it has many inclined slots and inclined portions, wherein the inclined slots serve, one up through the. inclined slits blown stripping gas to give an acute angle with respect to the bottom plates, thereby to disperse at least a portion of the liquid or the slurry flowing on the inclined portions of the bottom plates and a mixed gas-liquid or gas-solid-liquid phase thereon while the gas with the new direction accelerates the drainage of the liquid or slurry, thereby preventing the liquid or slurry from resting on any part of the soil, and that it manages to stop the liquid or slurry without overflow.

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The plurality of bottom plates constituting the bottom are arranged so that the gas blown through the slits of a plate in a lateral direction at an angle of about 45 ° to the flow direction of the liquid or slurry on the bottom and in a side direction at an angle of is directed about 90 ° to the direction of the blown through the slots of the adjacent bottom plate gas. The floor panels are made of expanded metal. The floor area forms just below the fall plate of the next higher floor a cover plate which is inclined to the ground and thereby prevents a jam or standstill of the liquid or slurry in this area. The gas-liquid contact urine contains a perforated support ring that supports the floor.

The slurry flowing on the bottom is a polyvinyl chloride slurry containing residual vinyl chloride monomer, the gas being heated to maintain the slurry at a temperature of 60 to 100 ^° C.

The process of the invention consists of placing the liquid or slurry on the head of a gas-liquid contact tower while blowing off stripping gas at the bottom. The ascending stripping gas is successively passed over the trays through their slots in countercurrent with the descending liquid or slurry, dispersing at least a portion of the liquid or slurry flowing on the inclined portions of the tray plates and thereupon a mixed gas-liquid or slurry Gas-solid-liquid phase, while that into the new cattle

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Directed gas accelerates the flow of the liquid or slurry while accelerating the stagnation of the liquid or slurry, thereby preventing the liquid or slurry from stopping at any part of the soil and obviating overflow weirs to hold the liquids or slurry out of the volatiles strip the heated liquid or slurry and then remove the volatile at the top of the tower and the liquid or slurry stripped of the fugitive from the bottom of the tower.

According to the method, the bottom plates constituting the bottom are arranged so that the gas blown through the slits of a plate in a lateral direction at an angle of about 45 to the liquid or slurry flow direction on the bottom and in a side direction at an angle is directed from about 90 ° to the direction of the blown through the slots of the adjacent bottom plate gas.

embodiment

The invention will be explained in more detail below with reference to an exemplary embodiment *

In the accompanying drawing show:.

Figure 1 is a partial view of an embodiment of a bottom plate with inclined or oblique slots.

FIG. 2 (A) is an illustration of a bottom used in the gas-liquid contact tower according to the invention and the slanted bottom

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'Contains arranged so r · · · plates according to Fig. 1,

that a gas can be blown through the slots in the direction of the small arrows;

Pig. 2 (B) is a partial longitudinal section of the gas-liquid contact door ms taken along the line L-L of Fig. 2 (A)

Fig. 3 is an illustration of the mixed gas-solid-liquid phase formed on and over a soil used in the invention;

4 is a schematic representation of an embodiment

"Guided liquid contact tower used in tests with a PVC slurry for flowability and sedimentation tendency;

Fig. 5 is a schematic representation of the deposition of PVC on a bottom of a tower made of a PVC Aufsehlämmung that was given to the tower of FIG. 4, but the execution of (D) the absence of a PVC deposit on the slotted floor panels of a soil according to the invention shows;

Fig. 6 '(A) is a schematic illustration when using different types of soil;

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Fig. 6 (B) is a schematic representation when using a fall sheet according to detail (B) in Fig. 6 (A).

FIG. 6 (C) is a schematic illustration of the combined use of a fall sheet and a cover sheet. FIG.

Fig. 7 (A) is a plan view of a support ring, the

i'n a gas-liquid contact tower is used according to the invention;

7 (B) shows an enlarged detail B of the support ring according to FIG. 7 (A) and FIG.

Fig. 8 is a schematic representation of the operation of a gas-liquid Kontäktturmes having floors according to the invention with a bottom number of "25.

In Figures 1 and 2, a bottom plate 1 is shown having inclined openings 2 and inclined portions 3. The bottom plate 1 is made of so-called expanded metal. The width of the openings 2 formed as slots is z, B. preferably about 2 to 5 mm.

As shown in Fig. 2 (A), the bottom plates 1 are arranged in a gas-liquid contact tower so that a stripping gas blown off through the inclined slits 2 in a direction at an angle of ζ, B. about 45 ° to the flow direction of a sediment

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In addition, a bottom plate 1 provided with slits 2 is arranged in relation to the adjacent slotted bottom plate 1 so that the direction of the discharge gas blown off through the slits 2 of the former plate 1 makes an angle of e.g. , B. 90 with the direction of the gas blown through the slots 2 of the latter plate 1 vdrd forms. When the amount of liquid on the ground is small, the total amount is dispersed by the gas into minute liquid particles. When the amount of liquid on the bottom is large, the gas is dispersed in the liquid in the form of bubbles, at the same time dispersing a part of the liquid, thereby producing an effective gas-liquid contact. 'Gas. And liquid, which are in the mixed phase on the ground, move to the inclined fall plate and the pulse of the liquid flow is increased by the direction of flow of the gas. According to the invention, this gas-liquid contact mechanism can be used to stop the liquid without overflowing. the flow of the liquid is promoted by means of the gas flow and thereby the. Effectiveness of the gas-liquid contact improved. This vdrd of Fig. 3 clearly. ....

According to Fig. 3, the gas has a pointed flow direction against the bottom plates 1 and is through the inclined slots 2 of the bottom plates 1 via the bottom plates · 1 in the direction X at a predetermined angle with direction Y, in which the liquid along the inclined portions 3 of Plate 1 flows, blows and disperses the liquid to form a mixed gas-solid-liquid phase 7. As shown in Fig. 2 (B) -in

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represented in this Pall, the mixed gas-solid liquid phase 7 is allowed to bounce against gas-liquid separator plates 6, which may be provided if necessary, thus substantially preventing entrainment or tearing. Plates of the same type as used as floor panels 1 can usually be used to manufacture the gas-liquid separator panels 6.

As shown in Figs. 6 (B) and 6 (C), the sedimenting liquid tends to come to a standstill and cause the solid to settle in the area of the bottom near the inner wall of the contact tower; therefore, care must be taken to direct the liquid in this bottom area to the inside of the contact tower. The material from which the slanted bottom plates 1 are made may be selected according to the use case; both metals and plastics may be used therefor.

Commercially available expanded metal floor plates 1 ("Expand Metal") can also be used for the same purposes as above. So far, gas-liquid contact towers equipped with special trays have been described which are used in particular for contact of a gas with a slurry containing sedimenting solids. , ·

In the following, the gas-liquid contact method according to the invention for stripping monomeric vinyl chloride (VCM from a residual monomeric vinyl chloride-containing polyvinyl chloride slurry for the preparation of

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ί.

Polyvinyl chlorides using the gas-liquid contact tower according to the invention described. In the polyvinylchloride (PVC) degradation process, VOM-induced environmental pollution must be avoided by removing VOM from a YCM-containing PVC slurry by means of a distillation tower and also reducing the wastewater amount of dehydrators and the amount of VCM in the exhaust gases from dryers becomes. However, because PVC contained in the VCM-containing PVC slurry tends to settle out and undergo thermal degradation, it is not easy to remove the VCM from such slurries by steam stripping. So z. Bubble tray, sieve tray, etc. previously used for distillation is disadvantageous because the residual VCM-containing PVC slurry tends to stall on the floors as the PVC settles and deposits, because the floors have bells or are flat and thus make the floor cleaning with simultaneous loss of time very difficult. ,

In the operation of the gas-liquid contact tower or scraper tower according to the invention, on the other hand, the PVC slurry containing a considerable amount of VCM is deposited on top of the tower and flows down one after the other over the floors having slotted bottom slabs 1 a very effective stripping of the VCM from the PVC slurry without settling of the PVC from the slurry and without thermal degradation.

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The said method will be explained in more detail below.

As shown in Fig. 3, the VCM-containing PVC slurry flows on the inclined portion 3 of the bottom plate 1 while steam for stripping flows upward through the inclined or slanted slits 2, thereby getting a direction indicated by the arrows X. is hinted at. At this point, the steam flowing in the new direction accelerates the flow of the liquid or slurry indicated by Y and disperses the slurry to form a mixed gas-solid-liquid phase without jam or standstill of the slurry on the bottom. Thus, not only the heat input location between the slurry and the steam blown off through the slits 2 but also the mass transport is accelerated. In this way, the inclined slots 2 serve to direct the blown steam, impart fluidity and heat to the PVC slurry, and provide improved gas-solid-liquid contact. Further, the solid tends to precipitate out of the slurry on both the support ring 11 that holds the floor in the tower and on the area of the floor just below the fall plate of the next higher floor and deposit. In order to avoid this laugh part ₉ , the support ring is perforated so that the steam can flow through the obtained holes 17 while moving the slurry on a support ring 11; and the fall plate 4 and the bottom area just below the next upper floor have a certain inclination.

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  c.

When the operation of the tower is stopped, the PVC slurry flows through the slots 2 of the floor panels 1 and. Perforations or holes 17. of the support ring 11 down without pests settle anywhere in the tower. This makes it possible to easily clean the interior of the tower. It should also be noted that the floors used here are also self-cleaning. Conventional distillation towers which can be commonly used herein are the same as the gas-liquid contact tower of the present invention except for the described base plates of the invention, the support ring, etc. The operating conditions of the tower are dependent on the liquid or slurry to be treated on contained solid, the properties required in the product, etc. variable; z. For example, stripping of VCM from a VCM-containing PVC slurry in the production of PVC may preferably be carried out at 60 to 100 ^° C.

The gas-liquid contact tower of the present invention and the process practicable therewith have the following advantages in terms of stripping VCM from a residual VCM-containing PVC slurry

- The tower can be operated continuously, without the PVC product undergoes thermal degradation, since PVC does not precipitate or settle on the floors}

- The tower can be operated easily and the number of operators need not be increased for the operation;

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at least 90 % of the residual VCM contained in a PVC slurry can be removed for recovery;

the amount of residual YCM in dried PVC can be reduced to not more than 10 ppm;

the amount of VCM contained in waste water from dehydrators can be reduced;

The amount of VCM contained in gas for drying PVC is reduced to an extreme degree

• become;

- The inside of the tower is easy to clean because PVC does not stay in the tower. It is therefore easy to replace a PVC slurry of one kind by a PVC slurry of another kind in a short time;

the VCM obtained by stripping can then be treated using ordinary recovery systems;

- The tower has a compact shape;

the manufacturing costs for a stripping unit according to the invention are lower than for conventional stripping units.

The experimental results obtained with the contact tower according to the invention and the associated method are described in more detail below.

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Example r

(1) A gas-liquid contact tower as shown in Fig. 4 was used. A PVC slurry 20 containing 30% by weight of PYC (the slurry was similar to that actually produced by adding water to PYC as product) was charged to the distillation tower to find out how the bottom affected the flow of the PYC Slurry eases and prevents settling of PVC. ,

The method described above was carried out, but each type was used on conventional trays to compare the performance between the new trays and the conventional trays instead of the new trays.

The contact tower used (distillation tower) was made of a transparent resin to visually observe the performance of the floors from the outside.

The comparative tests were carried out by placing the slurry 20 on the top of the tower by means of a pump 10, while at the bottom, air or gas G was blown into the tower by the gas pump 9. In the following, the behavior of soils was observed with respect to the flowability of the slurry thereon and the tendency for sedimentation, the results being shown in FIG. It is obvious that when using bell bottoms, the PVC settled on the bells and weir weirs, reducing the fluidity of the slurry (A); both

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The valve bottom and trays used did not appear to have different behavior during operation, however, the PVC settled on the valve trays and trays after operation was stopped ((B) and (C)); In contrast, the PVC was neither deposited nor deposited on the floors (D) according to the invention.

(2) Then, the flowability of the PVC slurry was observed in the bottom area just below the down pipe of the next highest floor and on the support ring using the various types of piles as shown in Fig. 6 (A). The fall plate or the drain plate 4 may be vertical or inclined. As indicated in Fig. 6 (B), by the presence of the drop sheet 4, only deposition of a portion of the PVC on the bottom portion 5 occurred just below the drop sheet 4 (see Fig. 2 (A), reference numeral 5)> while combined use of the fall plate 4 and a cover plate 8 did not settle PVC, as indicated in Fig. 6 (C). The cover plate 8 is inclined at an angle of preferably about 10 to about 30 ° to the ground as shown in Fig. 6 (C). Further, as shown in FIGS. 7 (A) and 7 (B), because of the perforation on the perforated support ring 11 and / or in the area where the support ring 11 and the floor panels 1 overlap each other, because of small holes 17 deposited in the overlapping area no PVC. Regardless of the shape of the holes 17, it is desirable that the small holes 17 be provided quite close to the inner wall of the tower. A suitable gap 18 (eg, 2 mm) is provided between the support ring 11 and the inner wall of the tower. The reference numeral 19 designates areas in which the support ring 11 is welded to the inner wall of the tower.

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Said cover plate 8 can be formed by bending part of the bottom plates 1 of the bottom so that the bent portion forms a predetermined angle with the remaining portion of the bottom plates 1, as shown in Pig, Fig. 6 (C).

(3) Stripping was also carried out as described in Pig. 8 is shown. When stripping a distillation tower of 300 mm diameter was used, which was equipped with 25 floor plates in the ground clearance of 300 in, each floor of a slanted floor slab according to the invention 1 consisted. A PVC slurry containing 30 wt% PVC and residual VCM was placed on top of the tower and flowed successively over all trays 13 while being contacted with steam blown into the bottom 13 of the tower. The inside of the tower was brought to about 60 to about 100 ⁰ C, since it was heated by the injected steam, and maintained at about 500 to 600 Torr using a vacuum pump 15. In this way, the PVC slurry was stripped of residual VCM as it moved from the head 12 of the tower to the bottom 13. The ratios of VCM removal are given in the following table; however, they varied depending on the average degree of polymerization of the PVC. The VCM produced at the head 12 of the tower and the steam were passed to a recovery system and the steam was condensed in a condenser to return it to the distillation tower via recycle 14. The VCM-stripped PVC slurry 16 stripped from the bottom 13 of the tower was dried in a dry system to give product PVC. The resulting PVC

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Product had a quality that was not degraded by thermal degradation.

table

average amount of VCM in PVC slurry Polymerization on dry basis (ppm)

degree of -

PVC before loading

act action (%)

7200 .350 95.1

1050 5100 260 94.9

3300 220 .93.3

5300 480 90.9 ⁸⁰⁰ 3900 350 91.0

Claims (8)

198 25 © 17.2.1978  'APBOIj / 198 258 50 839 24 Erfindungsanspru.cn 1, gas-liquid contact tower for removing a volatile substance from a liquid containing it or a slurry containing sedimenting pesticide and the volatile matter, comprising a plurality of trays, each consisting of a plurality of bottom plates and a fall plate, characterized by in that the floor panels (1) are formed to have many inclined slots (2) and inclined areas (3), wherein the inclined slots (2) serve to give an upwardly through the inclined slots (2) stripping gas an acute angle sighting to the bottom plates (1) and thereby at least a portion of the liquid or slurry on the inclined portions (3) of the bottom plates (1) flows to disperse and form thereon a mixed gas-liquid or gas-solid liquid phase (7), while the gas directed in the new direction is the flow of liquid or liquid Slurry accelerates while stopping the liquid or slurry at any. Part of the floor prevents, without overflow weirs for stopping the liquid or slurry. 2. Gas-liquid contact tower according to item 1, characterized in that the plurality of bottom plates (1) forming the bottom, are arranged so that through the slots (2) of a plate (1) blown gas in a lateral Direction at an angle of about 45 ° to the direction of flow of the liquid or slurry on the ground and into a side 198 2 .17.2.1978 APBO13 / 198 50 839 24 directed at an angle of about 90 ° to the direction of the through the slots (2) of the adjacent bottom plate (1) blown gas. 3. Gas-liquid contact tower according to item 1 and / or 2, characterized in that the bottom plates (1) made of expanded metal (Ecpand metal) are made. 4. Gas-liquid contact tower after one of the points 1 to 3 »characterized in that the bottom area just below the fall plate (4) of the next higher floor (1) forms a cover plate (8) which is inclined to the ground and thereby prevents a jam or standstill of the liquid or slurry in this area. 5. gas-liquid contact tower according to one of the items 1 to 4, characterized in that it contains a perforated support ring (11) which carries the ground. 6. The gas-liquid contact tower according to any of items 1 to 5 »characterized _s that the current flowing on the ground slurry, a polyvinyl chloride to be slurry, the residual monomeric vinyl chloride enthälts, and that the gas is heated so that the slurry at a temperature of 60 to 100 ⁰ C stops. A method of removing a volatile matter from a liquid containing it or a slurry containing sedimenting solid and the volatile with a device 2ZFE & 1978 * til) li (Jyi " according to at least one of the items 1 to β, characterized in that the liquid or slurry is placed on the head of a gas-liquid contact tower while blowing off stripping gas at the bottom, the ascending stripping gas successively over the trays through their slots (2) in the Passing countercurrent with the descending liquid or slurry, dispersing at least a portion of the liquid or slurry flowing on the inclined portions (3) of the bottom plates (1), and thereafter mixing a mixed gas-liquid or gas-solid liquid phase ( 7), while the gas directed in the new direction accelerates the flow of liquid or slurry, thereby preventing the liquid or slurry from stopping at any part of the bottom and obviating overflow weirs, to keep the liquids or slurry from becoming trapped heated liquid or slurry stri and then remove the volatile at the top of the tower and the liquid or slurry stripped of the fugitive material from the bottom of the tower. 8. The method according to item 7, characterized in that the bottom plates forming the bottom (1) are arranged so that the gas blown through the slots (2) of a plate in a lateral direction at an angle of about 45 ° to the flow direction of the liquid or slurry is directed to the bottom and in a lateral direction at an angle of about 90 ° to the direction of the gas blown through the slots (2) of the adjacent bottom plate (1). For this 3 pages drawings