WO1992004114A1

WO1992004114A1 - Apparatus for creating intensive contact between a liquid and a particulate solid

Info

Publication number: WO1992004114A1
Application number: PCT/HU1991/000042
Authority: WO
Inventors: Csaba Sisak; Béla SZAJANI; Péter KOMAROMY; Péter NEMES
Original assignee: Reanal Finomvegyszergyár
Priority date: 1990-09-04
Filing date: 1991-09-04
Publication date: 1992-03-19
Also published as: HU905771D0

Abstract

The invention relates to an apparatus for creating intensive contact between a liquid and a particulate solid. Said apparatus is a standing cylindrical one with a truncated cone-shaped lower part (12), a screw mixer (5) with a pitch of 15-25°, mounted on a shaft (4), is inserted along the vertical axis of the apparatus, said screw mixer (5) is surrounded by a cylindrical internal tube (1) with an internal diameter not exceeding 50% of the internal diameter of the cylindrical part of the apparatus, the distance between the lower end of said cylindrical internal tube (1) and the bottom point of the apparatus does not exceed the internal diameter of said cylindrical internal tube (1), a perforated disc (6) is mounted on said shaft (4) above the upper end of said cylindrical internal tube (1), the apparatus is equipped at its upper part with means (7) for introducing liquid, at its top part (3) with means (8) for introducing solid, at its truncated cone-shaped lower part (12) with means (9) for taking off liquid and with a filter insert (11) covering at least said means (9), and at its bottom part (2) with means (10) for emptying the apparatus.

Description

APPARATUS FOR CREATING INTENSIVE CONTACT BETWEEN A LIQUID AND A PARTICULATE SOLID

The invention relates to an apparatus for creating intensive contact between a liquid and a particulate solid. The apparatus according to the invention is particularly suitable for creating intensive contact between a viscous liquid and a particulate solid of low den-.i'-^. A requirement for creating intensive contact between a viscous liquid, such as a concentrated solution or oil and a particulate solid of low density, such as an adsorbent, a catalyst, etc., frequently appears in various fields of technology, such as in pharmaceutics1 and food industry, at waste water purification and the like. Of the particulate solids with low density solids 0.1 to 2 mm in particle size having highly porous surface and bearing reactive groups on their surfaces or in the pores (such as gels, macroporous polymers, etc.) gain increasingly wide utilization. The density of such solids exceeds the density of the liquid present maximum by some per cents.

No apparatus enabling a highly effective contact between these solids and a liquid, particularly a viscous one, is available now. The known fixed bed apparatuses, widely utilized in fluid/solid material transport processes, are inapplicable for this purpose owing to the

SUBSTITUTESHEET great pressure drop and to the risk of plugging. Fluidised bed apparatuses are inapplicable, too, since the viscous liquid transports away the light particles from the apparatus. Although in apparatuses equipped with mechanic or pneumatic means for mixing an intensive contact can be created between light solids and viscous liquids, the existing apparatuses have the disadvantage that the ratio of solid substance must not exceed 20 % by volume, since otherwise flow would be highly uneven and the appropriate stirring of the mixture would require great energy or would even be impossible.

Consequently, there is a need for an apparatus for creating intensive contact between a liquid, particularly a viscous one, and a particulate solid, particularly one with low density, which operates safely even at high volumetric capacities, ie. when the ratio of the solid substance is much more than 20 % by volume.

The invention aims at providing such an apparatus.

It has been found that when a liquid is contacted with a particulate solid in an apparatus equipped with a combined means for mixing comprising a screw mixer surrounded with a cylindrical internal tube and at least one additional mixing element, a very intensive contact can be created between the liquid and the solid even when the solid content of the mixture is high, e.g. 40-50 % by volume of the mixture as a whole.

Screw mixers are generally known and are generally applied to mix various solids with one another, frequently with the simultaneous comminution of the solids. Hungarian patent no. 174,030 discloses a drier for effective drying of heat sensitive granular materials. The drier disclosed therein comprises a conveyor screw installed along the vertical axis of the drier, which may optionally be surrounded by a cylindrical internal tube to promote the circulation of the particles. The wet granular material is dried by introducing hot air into the apparatus at its bottom. Air is introduced tangentially through

SUBSTITUTE SHEET specially formed whirling rings, which maintains the particles in an intensive circular movement at the bottom of the drier. The conveyor screw serves to convey the upper wet material to the bottom of the apparatus where drying is the most intensive, and the cylindrical internal tube, if present, promotes the circulation of the particles. Thus, in the apparatus according to the cited reference the intensive contact between air and the particulate solid is created primarily by the approriate selection of the means for introducing air and of the direction of air intro¬ duction; the further elements of the apparatus only assist in maintaining or improving this contact. The apparatus according to the present invention operates, however, without air introduction, and the intensive contact between liquid and fluid is created in the apparatus according to the invention by utilizing a specific combination of mixers and by the appropriate arrangement of certain structural elements.

Thus, the invention relates to an apparatus for creating intensive contact between a liquid and a particulate solid. The apparatus according to the invention has a standing cylindrical part with a truncated cone- shaped lower part, a screw mixer with a pitch of 15-25°, mounted on a shaft, is inserted along the vertical axis of the apparatus, said screw mixer is surrounded by a cylindrical internal tube with an internal diameter not exceeding 50% of the internal diameter of the cylindrical part of the apparatus, the distance between the lower end of said cylindrical internal tube and the bottom of the apparatus does not exceed the internal diameter of said cylindrical internal tube, a perforated disc mixer is mounted on said shaft above said internal tube, and the apparatus is equipped at its top part with means for introducing liquid, at its truncated cone-shaped lower part with means for taking off liquid and with a filter insert covering at least said means for taking off liquid, and at its bottom part wit means for emptying the apparatus.

SUBSTITU The apparatus according to the invention is illustrated by the aid of the accompanying drawings, which serve only as examples without limiting the invention thereto. Of the drawings - Fig. 1 is a sectional view of an apparatus according to the invention;

- Fig. 2 is a sectional view of a horizontal cascade built up from three apparatuses shown in Fig. 1; and

- Fig. 3 is a sectional view of a vertical cascade built up from two apparatuses according to the invention. The apparatus shown in Fig. 1 comprises a standing cylindrical part 21 provided with a truncated cone-shaped lower part 12. Top part 3 of the apparatus is equipped with means 8 for introducing particulate solid, and the upper part of the apparatus is equipped with means 7 for introducing liquid. Bottom part 2 of the apparatus is equipped with means 10 for emptying the apparatus. The truncated cone-shaped lower part 12 of the apparatus is equipped with means 9 for taking of liquid. Means 7., 3, 9 and 10 may be e.g. pipe ends. Filter insert 11, covering at least means 9, is placed into the truncated cone-shaped lower part 12. Filter insert 11 covers preferably the complete truncated cone-shaped lower part 12 of the apparatus, and is made preferably of sieve cloth. Along the vertical axis of the apparatus is screw mixer 5 mounted onto shaft 4. The pitch of screw mixer 5 is critical; it is 15-25°, preferably 17-20°. Screw mixer 5 is surrounded with a cylindrical internal tube 1, the internal diameter of which does not exceed 50% of the internal diameter of cylindrical part of the apparatus. The internal diameter of cylindrical tube 1 is preferably 30-45% of that of the cylindrical part of the apparatus. The gap between screw mixer 5 and cylindrical internal tube 1 is selected in harmony with the particle size- of the particulate solid to be contacted with the liquid, taking into account that no disintegration of the particulate solid should take place when contacting it with the liquid. The difference between the internal diameter of the cylindrical internal tube and the diameter of the screw mixer is preferably at least the fourfold of the greatest particle size. Further¬ more, in order to avoid disintegration or deformation of the particulate solid, it is preferred to use a screw mixer with rounded profile rather than with a sharp one.

The distance between the bottom point of the apparatus and the lower end of the cylindrical internal tube is critical; it must not exceed the diameter of the cylindrical internal tube 1. It is preferred that this distance is about 30-60% of the diameter of the cylindrical internal tube.

The distance between the highest point of the apparatus and the upper end of the cylindrical internal tube 1 is not critical; it should be taken into account, however, that the level of the suspension filled into the apparatus must reach perforated disc mixer 6, mounted on shaft 4 above the upper end of the cylindrical internal tube 1, since other¬ wise an intensive contact between the liquid and the particulate solid cannot be maintained. The length of the cylindrical internal tube 1 is preferably about 2/3 of the length of the apparatus itself.

Perforated disc 6 is mounted on shaft 4 above the upper end of the cylindrical internal tube 1. The perforated disc 6 rotates together with the screw mixer 5 and serves to ensure a homogeneous distribution of the paricles of the solid in the liquid. In the absence of such a perforated disc the particles tend to accumulate along the outer wall of the* cylindrical internal tube 1, which would impair the contact between the solid and the liquid. The diameter of the perforated disc 6 should exceed that of the cylindrical internal tube 1, but must be smaller than the diameter of the cylinαrical part of the apparatus. It is preferred that the diameter of the perforated disc 6 is the arithmetic means of the diameters of the cylindrical internal tube and of the diameter of the cylindrical part of the apparatus. It is preferred to insert propeller mixer 13 into the apparatus below the lower end of the cylindrical internal tube l. The diameter of the propeller mixer 13 may e.g. 80 % of the diameter of the bottom part 2 of the apparatus. It is mounted onto shaft 4 in such a position that it should not reach the walls of the apparatus. Propeller mixer 13 assists to avoid sedimentation at the bottom part of the apparatus.

As it has already been mentioned above, filter insert 11 is placed into the truncated cone-shaped lower part 12 of the apparatus according to the invention. Filter insert 11 must cover at least means 9 for taking off liquid; it is more preferred, however, when filter insert 11 covers the whole truncated cone-shaped lower part 12 of the apparatus. Filter insert 11 may be made e.g. of sieve cloth or of a net; the hole diameter of filter insert 11 must be smaller than the diameter of the smallest particles of the particulate solid to be treated in the apparatus according to the invention.

During operation, shaft 4 is rotated by rotating means 14 mounted onto shaft 4. Rotating means 14 may be e.g. a rotor of adjustable speed of rotation.

Fig. 2 is a sectional view of a horizontal cascade built up from three apparatuses shown in Fig. 1 which form the individual stages of the cascade. The stages are connected with one another through pipe 17 connecting means 9 of the first stage with means 7 of the second stage, etc. Valves 15 and 16 are inserted into pipe 17; by opening valve 16 and closing valve 15 the two stages are brought into operational contact with one another, and by closing valve 16 and opening valve 15 the first cascade operates as a single apparatus. The stages of the cascade can be multiplied at will, depending on the operation to be performed in the apparatus.

Fig. 3 is a sectional view of a vertical cascade built up from two apparatuses according to the invention which form the individual stages of the cascade. In this instance the bottom part of the upper stage forms the upper part of

SUBSTITUTESHEET the lower stage. Truncated cone-shaped filter insert 11 of the upper stage is in direct contact with the liquid compartment of the lower stage. In the upper stage screw 18, with a diameter smaller than that of screw mixer 5, inserted into the cylindric internal tube is adjusted to screw mixer 5. Transition tube 19, enclosing a section of screw 18, is adjusted to the lower end of the truncated cone-shaped filter insert 11 of the upper stage. The upper stage may comprise means 20 for sampling and monitoring the process proceeding in the apparatus.

The apparatus according to the invention can be utilized to advantage in any method where an intensive contact between a liquid and a particulate solid is to be maintained. The apparatus according to the invention can be applied most preferably to create an intensive contact between a viscous liquid (e.g. a liquid with a viscosity of 100 cP or more) with a particulate solid the density of which is almost equal to that of the liquid.

The following examples serve to demonstrate how the apparatus according to the invention is operated.

Example 1

The apparatus shown in Fig. 1 is utilized in an adsorption process whrein an impure liquid is decolourized with a particulate solid adsorbent consisting of spherical or nearly spherical particles. The density of the liquid to be decolourized and that of the adsorbent are nearly the same.

Means 7, 9 and 10 of the apparatus are closed, and the apparatus is filled up through means 8 with a suspension of the solid adsorbent in the liquid to be decolourized. During this operation screw mixer 5 is rotated with a speed of 10-30 r.p.m. in order to ensure that the cylindrical internal tube 1 is also homogeneously filled up with the suspension. When the level of the suspension reaches perforated disc 6, means 8 is closed, and the speed of rotation is adjusted to a level at which the average sedimentation rate of the particles in the annular section between the inner wall of the apparatus and the outer wall of the cylindrical internal tube 1 is 1-5 cm/sec. The progress of the adsorption process is monitored by regularly sampling the liquid through means 9.

When the purity of the liquid reaches the desired value, the speed of rotation is decreased to the initial, and the liquid is removed from the apparatus through means 9. Thereafter a fresh liquid to be decolourized is filled into the apparatus through means 7, and the operation is repeated.

When the adsorbent is inactivated, it can be reactivated in the apparatus itself by filling a reactivating liquid into the apparatus through means 7 and stirring the mixture until reactivation is complete.

Exam le 2

A viscous liquid also comprising colloidal particles is treated with an ion exchange resin in a continuous , operation in the cascade system shown in Fig. 2.

The stages of the cascade are filled up with a 40 % by volume suspension of the ion exchange resin formed with the liquid to be treated as described in Example 1. Thereafter means 8 of the individual stages are closed, valves 16 are opened, valves 15 are closed, and fresh liquid is fed into the first stage through means 7. Screw mixers 5 of the individual stages are rotated during the operation with a speed enabling an even sedimentation rate of 1-5 cm/sec in the annular sections of the individual stages. If desired, the liquid is sampled through valve 15.

When the ion exchange resin is inactivated, it can be reactivated in the cascade itself as described in Example 1, with the difference that a reactivating liquid is passed through the stages.

Example 3

Hydrolysed starch is saccharified with immobilized glucoamylase enzyms in a continuous operation in an apparatus as shown in Fig. 3.

Means 7, 9, 10 and 20 are closed, and the individual stages oi the apparatus are filled up with a suspension of immobilized glucoamylase enzyme formed with hydrolysed starch solution through means 8. Means 8 are closed, and fresh hydrolysed starch solution is fed into the apparatus through means 7. Glucose, formed in the process, is continuously removed in solution through means 9. The liquid flow enters the lower stage through filter insert 11 of the upper stage; some reaction also takes place in transition tube 19. However, owing to the upward movement of screw mixer 5, no particulate solid can enter the lower stage. During the enzymatic reaction screw mixer 5 is rotated, and the mixture is regularly sampled at means 20. When the immobilized enzyme preparation is inactivated, the particulate solid is removed from the lower stage of the apparatus through means 10. Upon changing the direction of rotation, screw mixer 5 removes the particulate εolid from the upper stage of the apparatus.

Claims

What we claim is :

1. An apparatus for creating intensive contact between a liquid and a particulate solid, characterised in that said apparatus comprising a standing cylindrical part (21) provided with a truncated cone-shaped lower part 12, a screw mixer 5 with a pitch of 15-25°, mounted on a shaft 4, is inserted along the vertical axis of the apparatus, said screw mixer 5 is surrounded by a cylindrical internal tube 1 with an internal diameter not exceeding 50 % of the internal diameter of the cylindrical part of the apparatus, the distance between the lower end of said cylindrical internal tube 1 and the bottom point of the apparatus does not exceed the internal diameter of said cylindrical internal tube 1, a perforated disc 6 is mounted on said shaft 4 above the upper end of said cylindrical internal tube l, the apparatus is equipped at its upper part with means 7 for introducing liquid, at its top part 3 with means 8 for introducing solid, at its truncated cone-shaped lower part 12 with means 9 for taking off liquid and at its bottom part 2 with means 10 for emptying the apparatus, and at its truncated cone-shaped lower part 12 with a filter insert 11 covering at least said means 9.

2. An apparatus as claimed in claim 1, characterised in that the internal diameter of the cylindrical internal tube 1 is 30-45 % of that of the cylindrical part (21) of the apparatus.

3. An apparatus as claimed in claim 1 or 2, characterised in that the distance between the bottom point of the apparatus and the lower end of the cylindrical internal tube 1 is 30-60 % of the diameter of the cylindrical internal tube 1.

4. An apparatus as claimed in any of claims 1 to 3, characterised in that the pitch of screw mixer 5 is 17-20°.

5. An apparatus as claimed in any of claims 1 to 4, characterised in that the filter insert 11 covers the whole truncated cone-shaped lower part 12 of the apparatus.

6. An apparatus as claimed in any of claims 1 to 5,

SUBSTITUTESHEET characterised in that a propeller mixer 13, mounted onto the shaft 4, is situated below the lower end of the cylindrical internal tube 1.

7. A vertical or horizontal cascade series of the apparatuses as claimed in any of claims 1 to 6.

SUBSTITUTESHEET