WO2012099508A1

WO2012099508A1 - Method and arrangement for admixing powdered substance to liquid

Info

Publication number: WO2012099508A1
Application number: PCT/SE2011/050040
Authority: WO
Inventors: Teuvo FRÖDEVALL
Original assignee: JERN, Lars
Priority date: 2011-01-17
Filing date: 2011-01-17
Publication date: 2012-07-26

Abstract

The invention relates to a method and an arrangement for admixing powdered substance to heated liquid in a mixing vessel (11). The powdered substance is fed into the mixing vessel via a powder inlet (16) provided in the upper part of the mixing vessel and is made to fall down into heated liquid in the mixing vessel in order to be mixed with this liquid. Dry heated air or other dry gas is blown into the upper part of the mixing vessel above the surface of the heated liquid via one or more gas inlets (25) provided in the mixing vessel in order to form a volume of dry hot air or other dry gas in upper part of the mixing vessel in the area of the powder inlet and thereby prevent vapour from the heated liquid in the mixing vessel from rising to the powder inlet.

Description

Method and arrangement for admixing powdered substance to liquid

TECHN ICAL FIELD OF THE INVENTION AND BACKGROUND ART

The present invention relates to a method according to the preamble of claim 1 and an arrangement according to the preamble of claim 4 for admixing powdered substance to heated liquid.

For example in connection with manufacturing of sweets, food or drugs, it is common to admix a powdered substance to a heated liquid. This often takes place by, using a feeding device, feeding the powdered substance into a mixing vessel via a powder inlet provided in the upper part of the mixing vessel and making it fall down into heated liquid in the mixing vessel in order to be mixed with this liquid. Figure 1 schematically shows an example of a conventional, previously known arrangement 1 for admixing a powdered substance to heated liquid. In the arrangement ac- cording to figure 1 , powdered substance is fed from a feed hopper 3 to a feed sluice 4 using a feed screw 2 and is then, via the feed sluice and a powder inlet 5 of a mixing vessel 6, made to fall down into and mix with heated liquid 7 in the mixing vessel. In the mixing vessel 6, the liquid is kept heated to a desired temperature using vapour or hot water which is made to circulate through a heating element 8 which is provided in the bottom and the side wall of the mixing vessel. In the mixing vessel 6, the powdered substance is mixed with the liquid 7 by stirring using a stirring device 9 provided in the mixing vessel to be either homogeneously dispersed in the liquid or dissolved therein. A commonly occurring problem in this kind of mixing method is that the liquid in the mixing vessel 6 as a consequence of the heating emits vapour which rises upwards in the mixing vessel. This vapour can escape via the feed sluice 4 and come into con- tact with powdered substance in the feed sluice 4 and the feed screw 2 and cause clogging of these, which in turn leads to im- paired production conditions and a need for regular stops of the arrangement for time consuming cleaning operations with costly production losses as a consequence. OBJ ECT OF THE I NVENTION

The object of the present invention is to provide a solution to the above-mentioned problem . SUMMARY OF THE INVENTION

According to the present invention, said object is achieved by means of method having the features defined in claim 1 and an arrangement having the features defined in claim 4.

According to the present invention, dry heated air or other dry gas is blown into the upper part of the mixing vessel above the surface of the heated liquid via one or more gas inlets provided in the mixing vessel in order to form a volume of hot dry air or other dry gas in the upper part of the mixing vessel in the area of the powder inlet and thereby prevent vapour from the heated liquid in the mixing vessel from rising to the powder inlet. The volume of dry hot air or other dry gas formed in the upper part of the mixing vessel will also allow the powdered substance that is fed into the mixing vessel via the powder inlet to disperse in the upper part of the mixing vessel before it comes into contact with the vapour, leading to an effective dispersal of the powdered substance and a decreased risk of forming lumps. According to one embodiment of the invention , the internal space of the mixing vessel is connected to the surroundings via a pressure equalizing duct, whose inlet opening is provided in the mixing vessel at a lower height level than said gas inlet. Hereby, a pressure equalization of the internal space of the mix- ing vessel is achieved while maintaining said volume of air/gas in the upper part of the mixing vessel. The pressure equalizing duct is preferably formed by a pressure equalizing tube which extends into the mixing vessel, said inlet opening being provided at the end of the pressure equalizing tube received in the mixing vessel.

According to another embodiments of the invention, said pressure equalizing tube is displaceably attached to the mixing vessel and adjustable into different displacement positions in relation to the mixing vessel to thereby allow an adjustment of the height position of said inlet opening. Adjusting the height position of the inlet opening of the pressure equalizing duct allows for a size adjustment of said volume of air/gas which is to be maintained in the upper part of the mixing vessel. Hereby, it is thus possible to adapt the size of said volume depending on the present working conditions and the amount of liquid in the mixing vessel.

According to another embodiment of the invention, the arrangement comprises a feed sluice, which is provided in or above the powder inlet and via which powdered substance is introducible into the mixing vessel. The feed sluice forms a flow obstruction for the air/gas blown into the upper part of the mixing vessel and makes it more difficult for this air/gas to escape from the mixing vessel via the powder inlet.

Other favourable features of the arrangement and the method according to the invention will appear from the dependent claims and the description following below.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will in the following be more closely described by means of embodiment examples, with reference to the appended drawings. It is shown in: a schematic, cut lateral view of an arrangement of previously known type for admixing powdered substance to heated liquid, Fig 2 a schematic, cut lateral view of an arrangement according to a first embodiment of the present invention ,

Fig 3 a schematic, cut lateral view of an arrangement according to a second embodiment of the invention , and

Fig 4 a schematic, cut lateral view of an arrangement according to a third embodiment of the invention.

DETAI LED DESCRIPTION OF PREFERRED EMBODIMENTS

In figures 2-4 different embodiments of an arrangement 10 according to the present invention for admixing powdered substance to heated liquid are schematically illustrated . In all embodiments, the arrangement 10 comprises a mixing vessel 1 1 for receiving liquid . The mixing vessel 1 1 is provided with an inlet 12 for feeding of liquid into the mixing vessel and an outlet 1 3 for feeding of liquid out from the mixing vessel . A stop valve 14 is provided in connection to the inlet 12 and a stop valve 15 is provided in connection to the outlet 1 3. Using the first- mentioned stop valve 14, the feeding of liquid into the mixing vessel 1 1 can be regulated, and using the last-mentioned stop valve 1 5, the emptying of liquid from the mixing vessel can be regulated. In the upper part of the mixing vessel 1 1 , there is a powder inlet 16 for introducing powdered substance into the mixing vessel . A feeding device 40 is connected to the powder inlet 16 and using this feeding device powdered substance is feedable into the mixing vessel 1 1 via the powder inlet 16. The arrangement 10 is further provided with heating means 17 for heating of the liquid introduced into the mixing vessel 1 1 . This heating means can comprise one or more heating elements 18 provided in or on the outside of a wall of the mixing vessel or in the internal space in the mixing vessel . In the embodiments here shown , the mixing vessel 1 1 is double-cased and the heating means 1 7 in this case comprises a heating element 18 which is arranged in the bottom 20 and the side wall 21 of the mixing vessel and through which a heat carrying medium , for example in the form of steam or hot water, is made to circulate to give off heat to the liquid 22 presently comprised in the mixing vessel 1 1 in order to heat the liquid to the desired temperature level and keep this temperature level of the liquid during the mixing proc- ess. The heating means 17 may alternatively comprise one or more electric heating elements provided in or on the outside of a wall of the mixing vessel or in the internal space in the mixing vessel. The arrangement 10 further comprises a heating device 23 for heating dry air or other dry gas, and a blowing device 24 for feeding of air/gas heated by the heating device 23 into the upper part of the mixing vessel 1 1 via one or more gas inlets 25 provided in the mixing vessel. The respective gas inlet 25 is ver- tically to be positioned between the powder inlet 16 and the surface 26 of the liquid 22 which is currently comprised in the mixing vessel 1 1 and should be provided in the upper part of the mixing vessel at a suitable vertical distance below the powder inlet 16, as illustrated in figures 2-4. By means of the blowing device 24, dry heated air or other dry gas is blown via said gas inlet 25 into the upper part of the mixing vessel 1 1 above the surface 26 of the heated liquid 22 in order to form a volume 27 or dry hot air or other dry gas in the upper part of the mixing vessel in the area of the powder inlet 16. This air/gas forms an air cushion/gas cushion in upper part of the mixing vessel 1 1 between the vapour and the powder inlet 16 and prevents vapour from the heated liquid 22 from rising up to the powder inlet and further into the feeding device 40, whereby clogging of the feeding device is prevented. This air/gas thus forms a dry sepa- ration zone between the humid vapour-filled space 1 9 in the mixing vessel 1 1 and the powder inlet 16. The boarder line be- tween vapour and dry hot air or other dry gas in the mixing vessel 1 1 is illustrated by a dashed line in figures 2-4.

The blowing device 24 may for example consist of a fan which via a gas conduit 28 is connected to the gas inlet 25 of the mixing vessel. By regulation of the rotational speed of the fan the inflow of air/gas into the mixing vessel 1 1 can be regulated.

The heating device 23 is arranged in the conduit 28 between the blowing device 24 and the gas inlet 25 of the mixing vessel and may for example comprise a heat exchanger through which a heat carrying medium , for example in the form of steam or hot water, is made to circulate to give off heat to the air/gas passing through the conduit 28. The heating device 23 could alterna- tively comprise one or more electrical heating elements provided in or on the outside of the conduit 28. By regulating the effect of the heating device the temperature of the air/gas blown into the mixing vessel can be regulated . In the case where the blown-in gas consists of air, this air is to have a temperature which is higher, for example 5-25°C higher, than the temperature of the vapour emitted from the liquid 22 in the mixing vessel.

The temperature of the air/gas blown into the mixing vessel 1 1 can be regulated depending on the temperature of the vapour emitted from the liquid 22 in the mixing vessel. For this purpose, the heating device 23 and the blowing device 24 can be controlled by means of an electronic control unit 35 (see Fig 2). The control unit 35 is connected to a first temperature sensor 36 provided in the mixing vessel 1 1 in order to obtain readings from the sensor regarding the temperature of the heated liquid 22 in the mixing vessel . The control unit 35 is further connected to a second temperature sensor 37 provided in the mixing vessel 1 1 in order to receive readings from this sensor regarding the temperature in the upper space in the mixing vessel which is in- tended to be filled with dry hot air or other dry gas. When the blown in gas consists of another gas than air, which can be the case for example when the admixing of the powdered substance to the heated liquid has to take place in the absence of contact with air, this gas should be lighter than the vapour which is emitted from the heated liquid. The required temperature of this gas depends on the type of gas that is used and for certain types of gas it is possible that no heating of the gas needs to take place before it is blown into the mixing vessel 1 1 .

The internal space in the mixing vessel is in connection with the surroundings via a pressure equalizing duct 29, whose inlet opening 30 is provided in the mixing vessel at a lower height level than the gas inlet 25 of the mixing vessel and above the surface 26 of the liquid 22 received in the mixing vessel . By means of this pressure equalizing duct 29 the internal pressure in the mixing vessel 1 1 is limited. In the embodiments illustrated in figures 2 and 4, the pressure equalizing duct 29 is formed of a pressure equalizing tube 31 which extends through a wall of the mixing vessel and into the internal space of the mixing vessel. The inlet opening 30 of the pressure equalizing duct is in this case provided at that end of the pressure equalizing tube 31 received in the internal space of the mixing vessel . The pressure equalizing tube 31 is suitably displaceably attached to the mixing vessel 1 1 and adjustable into different displacement positions in relation to the mixing vessel to thereby allow an adjustment of the height position of the inlet opening 30. In the embodiment illustrated in figure 3, the pressure equalizing duct 29 consists of a hole which extends through a wall of the mixing vessel 1 1 .

In the embodiments illustrated in figures 2-4, a stirring member 32 is provided in the lower part of the mixing vessel 1 1 in order to effect a stirring of the liquid 22 which is currently comprised in the mixing vessel and thereby facilitate the mixing of this liquid and the powdered substance which is introduced into the mixing vessel via the powder inlet 16. This stirring member 32 may for example be rotated by means of a driving motor 33.

In the embodiments illustrated in figures 2-4, the feeding device 40 comprises a powder container 41 for receiving the powdered substance 34 intended for feeding into the mixing vessel 1 1 via the powder inlet 16. This powder container 41 may for example be in the form of a feed hopper. In the embodiments illustrated in figures 2 and 4, the feeding device 40 further comprises a feed member constituted by a feed screw 42 for feeding powdered substance from the powder container 41 to the powder inlet 16 of the mixing vessel.

In the embodiments illustrated in figures 2 and 3, the feeding device 40 also comprises a feed sluice 43, which is provided in or above the powder inlet 16 of the mixing vessel and via which powdered substance is introducible into the mixing vessel . This feed sluice 43 forms a flow obstruction for the air/gas blown into the upper part of the mixing vessel 1 1 and contributes to keep- ing this air/gas in the mixing vessel. In the embodiment illustrated in figure 2, the feed sluice 43 comprises a rotatable sluice feeder 44, which is arranged to receive powdered substance from the feed screw 42 and subsequently let this powdered substance fall down into the mixing vessel 1 1 . In the embodiment illustrated in figure 3, the feed sluice 43 comprises a feed opening 45 which can be opened and closed by means of a closing member 46, which in the illustrated example consists of a sliding damper. The closing member 46 may alternatively consist of a tiltable cover or the like. In the embodiment illustrated in figure 3, the feed sluice 43 is provided directly under the powder container 41 and configured to receive powdered substance directly therefrom .

In the embodiment illustrated in figure 4, no feed sluice is pro- vided between the feed screw 42 and the powder inlet 16 and dry hot air or other dry gas will in this case flow along into the upper part of the feed screw. Since the feed screw 42 inclines obliquely downwards from its outlet opening 47 and has its inlet opening 48 positioned at a lower height level than the gas inlet 25 of the mixing vessel, said air/gas is prevented from flowing further out from the feed screw via the inlet opening 48 of the feed screw. Hereby, a volume 27 of dry hot air or other dry gas can be maintained in the upper part of the mixing vessel 1 1 in the area of the powder inlet 16. The invention is of course not in any way limited to the embodiments described above. On the contrary, several possibilities to modifications thereof should be apparent to a person skilled in the art, without thereby deviating from the basic idea of the invention as defined in the appended claims.

Claims

A method for admixing powdered substance to heated liquid in a mixing vessel (1 1 ), the powdered substance being fed into the mixing vessel (1 1 ) via a powder inlet (16) provided in the upper part of the mixing vessel and made to fall down into heated liquid in the mixing vessel in order to be mixed with this liquid, characterized in, that dry heated air or other dry gas is blown into the upper part of the mixing vessel (1 1 ) above the surface of the heated liquid via one or more gas inlets (25) provided in the mixing vessel in order to form a volume of dry hot air or other dry gas in the upper part of the mixing vessel ( ) in the area of the powder inlet (16) and thereby prevent vapour from the heated liquid in the mixing vessel (1 1 ) from rising to the powder inlet.

A method according to claim 1 , characterized in , that said air/gas is heated using a heating device (23) before it is blown into the mixing vessel (1 1 ) using a blowing device (24).

A method according to claim 1 or 2, characterized in , that the powdered substance is introduced into the mixing vessel (1 1 ) via a feed sluice (43), which is provided in or above the powder inlet (16).

An arrangement for admixing powdered substance to heated liquid, comprising :

a mixing vessel (1 1 ) for receiving liquid,

heating means (1 7) for heating of said liquid, and a powder inlet (16) provided in the upper part of the mixing vessel (1 1 ) for introducing powdered substance into the mixing vessel ,

characterized in, that the arrangement ( 1 0) further comprises: a heating device (23) for heating of air or other gas, and

a blowing device (24) for feeding of dry air/gas heated by the heating device (23) into the upper part of the mixing vessel ( 1 1 ) via one or more gas inlets (25) provided in the mixing vessel.

An arrangement according to claim 4, characterized in, that the internal space of the mixing vessel (1 1 ) is connected to the surroundings via a pressure equalizing duct (29), whose inlet opening (30) is provided in the mixing vessel at a lower height level than said gas inlet (25).

An arrangement according to claim 5, characterized in, that the pressure equalizing duct (29) is formed by a pressure equalizing tube (31 ) which extends into the mixing vessel (1 1 ), said inlet opening (30) being provided at the end of the pressure equalizing tube (31 ) received in the mixing vessel (1 1 ).

An arrangement according to claim 6, characterized in, that the pressure equalizing tube (31 ) is displaceably attached to the mixing vessel (1 1 ) and adjustable into different displacement positions in relation to the mixing vessel to thereby allow an adjustment of the height position of said inlet opening (30).

An arrangement according to claim 5, characterized in, that the pressure equalizing duct (29) is formed by a hole which extends through a wall of the mixing vessel ( 1 1 ).

An arrangement according to any of claims 4-8, characterized in , that the arrangement (1 0) comprises a feed sluice (43) which is provided in or above the powder inlet (16) and via which powdered substance is introducible into the mixing vessel . An arrangement according to claim 9, characterized in , that the feed sluice (43) comprises a rotatable sluice feeder (44) or a feeding opening (45) closeable by a closing mem- ber(46).