GB2086249A

GB2086249A - Mixing apparatus

Info

Publication number: GB2086249A
Application number: GB8130699A
Authority: GB
Original assignee: Mitsui Toatsu Chemicals Inc; Toyo Engineering Corp
Current assignee: Mitsui Toatsu Chemicals Inc; Toyo Engineering Corp
Priority date: 1980-10-13
Filing date: 1981-10-12
Publication date: 1982-05-12
Also published as: JPS602899B2; KR880001059B1; IT8124450A0; KR830007127A; IT1139216B; JPS5768125A; GB2086249B

Abstract

An apparatus for mixing a highly viscous fluid with a low viscous fluid by use of a pipe (4) containing static type fluid mixer elements (3), and one or more perforated plates (2), the perforations amounting to less than 0.55 of the area of the plate, and any individual perforation being less than 0.1 of the total area of perforations in the plate, at least one static type mixer element facing the outlet (6) of the pipe. <IMAGE>

Description

SPECIFICATION Mixing apparatus This invention relates to an improvement in apparatus for mixing a highly viscous fluid such as thermoplastic resin with a low viscous fluid such as a mineral oil by using mainly static type fluid mixer elements.

The mixing apparatus widely used on an industrial scale in the art includes a dynamic type mixer such as a stirrer, extruder, pump, and the like, or a static type mixer having no driving portions, or a combination thereof. These mixing apparatuses are arbitrarily selected for use depending on the physical and chemical properties of materials to be mixed as well as on the purpose of mixing. The purpose of mixing fluids ranges widely among mass transfer such as fluid uniformalization, dispersion, chemical reaction, extraction, absorption, dissolution, and the like, or promotion of heat transfer, and the like. Consequently various types of mixing apparatus have been in use.

In order to accomplish these purposes of mixing, the dynamic type mixer has been built to meet the required mixing conditions with the structure of the mixer apparatus and the rotational speed thereof suitably arranged. On the other hand, the static type mixer is generally considered to encounter difficulties in mixing materials with considerable difference in viscosity, and the only method to solve such difficulties at present is either to increase the number of the static type fluid mixer elements or to combine a static type mixer with a dynamic type mixer. Attainment of the purposes of mixing as required necessitates an unduly large apparatus, and unduly high construction cost; a great obstacle to the satisfactory application of the static type mixer.Particularly, increase in the number of the static type fluid mixer elements, in the cases where highly viscous substances are mixed, remarkably increases the pressure loss within the mixing apparatus and results in limitations to the strength of the apparatus and to the operation thereof, no effective and improved method of mixing having been provided.

It is desirable to provide an apparatus for uniformly mixing a highly viscous fluid such as thermoplastic resin having a viscosity of from 10 to 300,000 poise under the conditions of a temperature at which mixing is effected and of a shear rate of 1 such', with a low viscous fluid such as mineral oil having a viscosity of from 0.2 to 500 centipoise measured at 200C or measured at a temperature 50C higher than the melting point of such a fluid as is solid at 200C.

It is also desirable to provide an apparatus in which the number of the static type fluid mixer elements is decreased, and limitations to the apparatus and to the operation thereof such as the pressure loss within the apparatus due to increase in the number of the static type fluid mixer elements is avoided beforehand in the case where a highly viscous fluid is uniformly mixed with a low viscous fluid by solely using a static type mixer as described above.

The present invention uses apparatus that is provided with static type fluid mixer elements and one or more perforated plates, having a ratio of the total cross-sectional area of all openings to the crosssectional area of the plate (hereinafter simply referred to as an opening ratio) less than 0.55 and a ratio of the cross-sectional area of one opening to the total cross-sectional area of all openings (hereinafter referred to simply as a distribution ratio) less than 0.1, in a pipe through which the mixture of a highly viscous fluid and a low viscous fluid passes, wherein at least one of the static type fluid mixer elements faces the outlet of the pipe of the mixed fluid.The effect of the application of such apparatus according to the indicated purposes is so remarkable as ot be unanticipated in the prior art and remarkably increases uses of the static type mixer which contributes to energy saving.

In the drawings: Fig. 1 shows a perforated plate provided in the mixing apparatus of the present invention, and Fig. 2 is a schematic illustration showing a longitudinal cross-section through the mixing apparatus provided with a plurality of static type fluid mixer elements and a perforated plate.

The static type mixer element used in the present invention is a mixer element free of any driving portions. Examples of the mixer element include Static Mixer (marketed by Kenics Co., Ltd., Trade Name), Static Mixing Element (marketed by Sulzer Co., Ltd., Trade Name), Los lSG Mixer 8 Los LPD Mixer (marketed by Charles Los Co., Ltd., Trade Name), Square Mixer (marketed by Sakura Seisakujo Ltd., Trade Name), Honeycomb Mixer 8 Imustad Mixer (marketed by Tatsumi Engineering Co., Ltd., Trade Name), Shimazaki Pipe Mixer (marketed by Koritsu Kogyo Co., Ltd., Trade Name), Hi-mixer (marketed by Toray Industries Inc., Trade Name), and the like as listed in "CHEMICAL APPARATUS" 21 (3) 20 (1979). These mixer elements noted above are fitted for use singly or pluraly in the direction of the mixed fluid flow in the pipe.

The perforated plate used in the present invention is a plate which has small openings as well as an arbitrary inserting it therein, or fitted integrally with the pipe or with a static type fluid mixer element.

The aforesaid small openings give a flow channel through which the fluid passes regardless of the process by which it is manufactured and the shape of the perforated plate may be such that the surface thereof is uneven.

The aforesaid perforated plate may be used singly or in combination, or a plurality of perforated plates may be connected wtih each other through respective small pipes between respective small openings of one perforated plate and those of other perforated plates. In the case where a plurality of perforated plates are used and a static type mixer element is fitted between perforated plates, the static type mixer elements may be fitted arbitrarily when the number thereof is less than 20, but in the case where the number of the static type mixer elements to be fitted between perforated plates is more than 20, the synergistic effect of the aforesaid apparatus is not increased in proportion to the increase in pressure loss therein.A shell and tube type heat exchanger is a typical example of a modification of such a type in that the perforated plates are connected with each other through respective small pipes between respective small openings of one perforated plate and those of other perforated plates.

In the arrangement of the static type fluid mixer element and the perforated plate in the mixing apparatus of the present invention, arrangement of at least one of the static type mixer elements in the down-stream side of the mixed fluid in the pipe is essential; if required, respective functional elements may be arbitrarily arranged for use depending on the object to be mixed or the purpose of mixing, for example, as perforated plate -- static type fluid mixer element -- perforated plate -- static type fluid mixer element or static type fluid mixer element -- perforated plate -- static type fluid mixer element.

With a mixing apparatus in which a perforated plate is solely arranged on the down-stream side of a static type mixer differently from that having the aforesaid arrangement of the static type fluid mixer element and the perforated plate, the mixture effect of the present invention can not be obtained, but the arrangement of at least one of the static type fluid mixer elements in the downstream side of the mixed fluid is essential. The shape of the small openings in the perforated plate is arbitrary, but it is essential that a ratio of the total sectional area of all small openings to the sectional area of the plate be less than 0.55 and that a ratio of the sectional area of one small openings be less than 0.1. The opening ratio is most preferably in the range of from 0.1 to 0.35.When the opening ratio is greater than 0.55, the space distance between small openings on the perforated plate is reduced to such an extent that, in the case where a highly viscous fluid is mixed with a low viscous fluid which is incompatible therewith, dispersion takes place in the small openings of the perforated plate, but recoalescence takes place at the outlet of the perforated plate, resulting in no mixing effect of the present invention.

The distribution ratio is preferably less than 0.05, more preferably less than 0.001. When the distribution ratio is greater than 0.1 , the improvement in the mixing effect remains at a low level.

The perforated plate may be fitted at any arbitrary position as described above, and may also be inserted in a combined apparatus of a static type mixer with a dynamic mixer such as a screw pump.

The suitably highly viscous fluid used in the apparatus of the present invention has a viscosity normally greater than 10 poise, preferably greater than 500 poise, measured under the conditions of a temperature at which mixing is effected and of a shear rate of 1 sex~'. Examples of the aforesaid highly viscous fluid include thermoplastic resin such as polypropylene, polyethylene, polystyrene, high-impact polystyrene, AS resin, polyvinyl chloride, polyester, polyimide, polyamide, polyether-sulfone, and the like, a thick malt syrup, water-glass, and the like, and solutions thereof. In the case of such a highly viscous fluid as to have a viscosity less than 10 poise, no noticeable effect results by providing a perforated plate therewith.On the other hand, mixing of such a fluid as to have a viscosity exceeding 300,000 poise has not substantially been carried out on an industrial scale.

Examples of the suitable low viscous fluid for use in the mixing apparatus of the present invention include mineral oil, higher alcohols, higher fatty acids, and solutions thereof; water, organic solvents such as methyl ethyl ketone, acetone, methanol, styrene, ethylbenzene, acrylonitrile, and the like; organic peroxides such as lauroyl peroxide, benzoyl peroxide and the like, and solutions thereof; antioxidants, antistatic agents, dyes, plasticizers, and solutions thereof; and the like.

Except for gas, any fluid having a viscosity less than 0.2 centipoise at 200C or at a temperature 50C higher than the melting point of a substance which is solid at 200C has no possibility of being mixed with the aforesaid highly viscous fluid on an industrial scale. Mixing of gas with the highly viscous fluid is generally carried out in a dynamic mixer, or in a combined mixing apparatus of a dynamic mixer with a static type mixer, in which no noticeable effect is obtained by providing the perforated plate therewith.When the viscosity of the low viscous fluid exceeds 500 centipoise, the mixing performance resulting from providing the perforated plate therewith is the same as in the case where the number of the static type mixer element is increased to such an extent that the pressure loss in the mixing apparatus due to an increase in the number of the static type mixer elements to be provided therewith instead of the perforated plate may be the same as in the case where the perforated plate is provided therewith, with the result that no particular mixing effect is obtained by providing the perforated plate therewith.

The perforated plate suitable for the practice of the present invention and arrangement of the static type fluid mixer element and the perforated plate are explained in reference to Fig. 1 and Fig. 2.

Fig. 1 shows an example of a perforated plate 1 having small openings 2, arranged on the perforated plate 1 at a suitable distance from each other, the fluids to be mixed passing through the small openings 2.

Fig. 2 is a schematic illustration showing an example of the mixing apparatus of the present invention, in which the perforated plate 1 is fitted between the static type fluid mixer elements 3.

The static type mixer elements 3 and the perforated plate 1 are fitted in a pipe 4 in a suitable manner, fluids to be mixed are introduced from an inlet 5, subjected to mixing while passing through respective static type fluid mixer elements 3 and the perforated plate 1, and reach an outlet 6.

The present invention will be explained in greater detail by the following examples.

The viscosity of the highly viscous fluid used in the experiment was measured by Instron capillary rheometer, the capillary of which had a length of 2 inches and a diameter of 0.05041 inch. A sample was secured in the rheometer maintained at a measuring temperature, and 5 minutes later measurement was started. Measurement of the viscosity of the low viscous fluid was made by use of a Brookfield viscometer (marketed by Tokyo Keiki Co., Ltd.).

Example 1 Mixing for dissolution of acrylonitrile-styrene copolymer resin (hereinafter referred to simply as AS resin) with mineral oil was carried out by use of such a mixing apparatus that a circular perforated plate (opening ratio: 0.24; distribution ratio: 0.007) having a diameter of 50 mm and a thickness of 5 mm and having 1 50 2-mm circular small openings, arranged therein 3 mm distance from the center of each other, is inserted between the second and the third mixer elements from the up-stream side of the fluid to be mixed in a mixing apparatus having 14 elements, marketed by Sulzer Co., Ltd., under a trade mark of Static Mixing Element (SMX-type), and fitted in a pipe having an inner diameter of 52 mm. The mixing apparatus was provided with a cover and maintained at 2200C with a heating medium.The AS resin had a viscosity of 100,000 poise under the conditions of 2200C and a shear rate of 1 sex~', and was passed through the mixing apparatus at a flow rate of 10 gk/hr by a gear pump at 2200C. The mineral oil had a viscosity of 100 centipoise at 200C and was introduced into the mixing apparatus at flow rates shown in Table 1, respectively, by a metering pump through a small pipe leading to the inlet of the mixing apparatus. The degree of mixing for dissolution was evaluated by determining the number of undissolved mineral oil droplets contained in a plate of 1 mm in thickness prepared by extending 5 kg of the mixture of the AS resin and mineral oil withdrawn from the outlet of the mixing apparatus and are observed by use of a light microscope of 1 00x magnification.Difference between values indicated on the gauge pressures mounted at both the inlet and the outlet of the mixing apparatus, respectively, is directly determined as the pressure loss in the mixing apparatus.

The results are shown in Table 1.

Example 2 A solution consisting of 30 parts by weight of polystyrene, 60 parts by weight of styrene, and 10 parts by weight of ethylbenzene (hereinafter referred to simply as PS solution) was mixed for dissolving with water at 1 500C by use of such a mixing apparatus that a 35 mm square perforated plate (opening ratio: 0.37; distribution ratio: 0.067) having a thickness of 3 mm, and having 15 rectangular small openings of 1 mm in width and 30 mm in length arranged therein in parallel with each other at a distance of 1 mm from each other is fitted between the eighth and ninth mixer elements from the upstream side of the fluid to be mixed in a mixing apparatus having 30 elements, marketed by Kenics Co., Ltd., under the trade mark of Static Mixer, and fitted in a 1/2 inch pipe.The PS solution had a viscosity of 1 5 poise under the conditions of 1 500C and a shear rate of 1 sex~', and was passed through the mixing apparatus at a flow rate of 18 kg/hr by a gear pump. Water was introduced into the mixing apparatus through a small pipe leading to the inlet of the mixing apparatus at the respective flow rates shown in Table 1 by a metering pump. The degree of mixing for dispersion was evaluated by observing a mixture of the PS solution and water withdrawn from the outlet of the mixing apparatus by use of a 1 Ox magnifier and by determining the mean particle size of the water droplet dispersed. The pressure loss in the mixing apparatus is shown as the difference between values indicated on the pressure gauges mounted at both the inlet and outlet of the mixing apparatus.

The results are shown in Table 1.

Comparative Example 1 The procedure of Example 1 was repeated except that no perforated plate was used to effect mixing for dissolution.

The result is shown in Table 1.

Comparative Example 2 The procedure of Example 1 was repeated except that the perforated plate was removed and the number of the static mixing element is increased to 24 to effect mixing for dissolution. The result is shown in Table 1.

Comparative Example 3 The procedure of Example 2 was repeated except that the perforated plate was removed to effect mixing for dispersion. The result is shown in Table 1.

Comparative Example 4 The procedure of Example 2 was repeated except that the perforated plate was removed and the number of the static mixer element was increased to 50 to effect mixing for dispersion. The result is shown in Table 1.

TABLE 1

Example Comparative Example 1 2 1 2 3 4 5 Mixing Element Brand Name Sulzer Kenics Sulzer Sulzer Kenics Kenics Sulzer Number of Elements 14 30 14 24 30 50 14 Perforated Plate 1 1 None None None None 1 Opening Ratio 0.24 0.37 - - - - 0.49 Distribution Ratio 0.007 0.067 - - - - 0.5 Flow Rate of Mineral Oil 0.15 - 0.15 0.15 - - 0.15 (kg/hr) Flow Rate of - 0.10 - - 0.10 0.10 Water (kg/hr) Degree of Mixing for Dissolution (Number of mineral 0 - 1572 12 - - 1381 oil droplets per kg) Degree of Mixing for Dispersion (mean particle - 0.08 - - 0.48 0.31 - size of water droplets (mm) Pressure Loss 60 103 56 96 10 17 57 (kg /cm2) Comparative Example 5 The procedure of Example 1 was repeated except that the perforated plate was replaced by a circular perforated plate having a diameter of 50 mm, a thickness of 5 mm and 2 35 mm-diameter semicircular openings arranged therein (opening ratio: 0.49; distribution ratio: 0.5) with the result that the number of mineral oil droplets was 1,381 and the pressure loss was 57 kg/cm2.

Comparative Example 6 A thick malt syrup having a viscosity of 5 poise under the conditions of 200C and a shear rate of 1 sex~' and styrene having a viscosity of 0.78 centipoise at 200C were subjected to mixing for dispersion at 200C by use of the mixing apparatuses employed in Example 2 and Comparative Example 5, respectively. The thick malt syrup was passed through the apparatuses at a flow rate of 7 kg/hr by a gear pump, and the styrene was passed through the apparatuses at a flow rate of 0.1 kg/hr by a metering pump, respectively. The mean particle size of the dispersed styrene, determined by observing the fluid withdrawn from the outlet of the apparatus by use of a lOx magnifier, was 0.07 mm in the case where the apparatus in Example 2 was used, and 0.09 mm in the case where the apparatus in Comparative Example 5 was used.

Comparative Example 7 A thick malt syrup having a viscosity of 3,000 poise under the conditions of 200C and a shear rate of 1 sec1 and a polybutadiene solution in styrene having a viscosity of 1000 centipoise at 200C were subjected to mixing for dispersion. The apparatuses employed in Example 2 and in Comparative Example 5 were used in mixing for dispersion. The thick malt syrup was introduced into the apparatus at a flow rate of 1 5 kg/hr by a gear pump, and the polybutadiene solution was introduced into the apparatus at a flow rate of 2 kg/hr by a metering pump. The fluid withdrawn from the outlet of the apparatus was observed by a lOx magnifier to determine the mean particle size of the polybutadiene solution thus dispersed with the result that the mean particle size was 0.45 mm in the case where the apparatus in Example 2 was employed, and was 0.52 mm in the case where the apparatus in Comparative Example 5 was employed.

Claims

1. An apparatus suitable for mixing a highly viscous fluid with a low viscous fluid comprising in a pipe through which said fluid passes, static type fluid mixer elements and one or more perforated plates having a ratio of the total cross-sectional area of all openings in a said plate to the cross-sectional area of the plate of less than 0.55, and a ratio of the cross-sectional area of one said opening to the total cross-sectional area of all said openings of less than 0.1 , at least one said static type fluid mixer element being provided facing the fluid outlet of the pipe.

2. An apparatus according to claim 1, wherein the ratio of the total cross-sectional area of all openings in a said plate to the cross-sectional area of the plate is in the range of from 0.1 to 0.35.

3. An apparatus according to claim 1 or claim 2, wherein the ratio of the cross-sectional area of one said opening in a plate to the total cross-sectional area of all the openings in the plate is less than 0.05.

4. An apparatus according to claim 3, wherein the ratio of the cross-sectional area of one said opening to the said total cross-sectional area is less than 0.001.

5. Mixing apparatus substantially as described with reference to the drawings.

6. A method of mixing fluids of different viscosity, wherein a highly viscous fluid, having a viscosity of from 1 O to 30,000 poise under the conditions of a temperature at which mixing is carried out and of a shear rate of 1 sex~', is mixed wtih a fluid of low viscosity, having a viscosity of from 0.2 to 500 centipoise measured at 200 C, or at a temperature 50C higher than the melting point of the low viscous fluid if the low viscous fluid is solid at 200 C, by passing the fluids through a mixer according to any one of claims 1 to 5.

7. A method according to claim 6, wherein said highly viscous fluid is a thermoplastic resin or a solution thereof.

8. A method according to claim 7, wherein said highly viscous fluid is a styrene based thermoplastic resin, or a solution thereof.

9. A mixing method according to claim 6, substantially as described herein.