Apparatus and method for applying oscillatory motion

Technical Field

The present invention relates to an apparatus and method for applying oscillatory motion. In particular, the present invention relates to an apparatus and method for providing efficient mixing.

Oscillatory motion is of particular importance in processes that are dependant on mixing. For example, the oscillatory motion produced and applied when using mixing in the chemical, petroleum, process, pharmaceutical, cosmetic, bioscience, bioengineering, food and associated industries can be critical on mass/heat transfer processes, reactions taking place, and the final product obtained. In particular, the use of oscillatory baffled apparatus can be beneficial for carrying out mixing processes in these industries.

Background Art

1 In oscillatory baffled reactors, oscillatory motion and

2 the incorporation of baffles ensure that there is uniform

3 mixing of liquid-liquid, gas-liquid and solid-liquid

4 mixtures, as used in the aforementioned industries. At

5 present, the common methods used to generate oscillatory

6 motion are: pulsing the contents of an oscillatory

7 baffled reactor containing stationary baffles; and

8 oscillating a set of baffles within an oscillatory

9 baffled reactor. In the first case, the oscillatory

10 motion is generated using a piston or bellows or

11 diaphragm arrangement. In the latter case the

12 oscillatory motion is generated using a flywheel assembly

13 to convert rotary motion into linear oscillatory motion,

14 or by using linear motors. 15

16 Present apparatus available for imparting oscillations in

17 oscillatory baffled reactors suffer from several

18 drawbacks and disadvantages. In particular, in the

19 majority of the aforementioned industries, the processes

20 that are carried out require the vessel being used to be

21 sealed. This can be problematic as it involves placing a

22 seal around a moving object, i.e. a piston or the like,

23 that provides linear motion to the contents of the

24 vessel. Seals used for this purpose are known as

25 "dynamic" seals. Sealing a moving object is difficult as 26 there must be a degree of freedom to allow said object to 27. move, whilst the seal must be sufficiently tight to

28 withstand, for example, elevated or reduced pressures or

29 a corrosive environment. 30

31 Therefore, when performing an operation that involves

^■ 32 elevated or reduced pressures, multiphases, or a

33 corrosive environment, dynamic seals are often inadequate

and, in many cases, have to be changed daily due to severe wear and erosion. For some processes, no suitable dynamic seals exist, and oscillatory baffled reactors cannot be used for these processes. Furthermore, existing apparatus that uses dynamic seals cannot generally withstand pressure greater than 50 Bar.

Therefore it is an object of the present invention to overcome at least some of the drawbacks associated with the prior art.

A further object of the present invention is to provide an apparatus and method for oscillating or mixing the contents of a vessel without the use of a dynamic seal.

Disclosure of Invention

According to a first aspect of the present invention there is provided an apparatus for applying oscillatory motion to at least one substance in a vessel, the apparatus comprising: reciprocating means for applying motion to the at least one substance; and drive means for applying linear motion to the reciprocating means; wherein the reciprocating means and the drive means are magnetically coupled.

The substance can be a mixture of miscible or immiscible fluids; a reaction mixture of a chemical reaction; a dispersion, suspension, emulsion or micro-emulsion; or any other suitable material with at least some fluid properties.

The apparatus of the present invention facilitates the use of (for example) linear oscillators in reaction or mixing apparatus without the need for a seal around any moving parts (i.e. a dynamic seal). In particular, no moving parts pass from inside the vessel area to outside the vessel area or vice versa. Therefore, the internal vessel area may be completely sealed from the external environment, and the use of a dynamic seal is avoided. This allows the apparatus to be used effectively for high and low pressure reactions, or corrosive fluids, which is not always feasible using the apparatus of the prior art.

In addition, as no moving parts pass through the seals used in the present apparatus, said seals do not require changing as regularly as those in known devices. Therefore the apparatus of the present invention circumvents the inconvenience, time and cost implications associated with regularly changing dynamic seals.

Preferably the reciprocating means is hermetically sealed in a vessel.

Preferably the drive means comprises at least one magnet.

Optionally the reciprocating means comprises at least one magnet.

Preferably the reciprocating means is located substantially coaxially with the vessel.

Preferably the reciprocating means is located substantially coaxially with the drive means.

Preferably the reciprocating means comprises an actuator. The actuator may comprise a reciprocating shaft.

Optionally the reciprocating shaft is connected to a piston to form the actuator. The apparatus may further comprise a plurality of annular baffles, which are joined together by rails in a substantially equidistant manner, and arranged substantially in parallel, such that they extend radially inwards from the side of the vessel.

Alternatively the reciprocating shaft is connected to a baffle set to form the actuator. The baffle set has a number of annular baffles, which are joined together by rails in a substantially equidistant manner, and arranged substantially in parallel, such that they extend radially inwards from the side of the vessel.

The apparatus may further comprise a housing adapted to attach to the vessel. In particular, the housing and the vessel may be operatively connected to form a hermetically sealed unit. The apparatus may further comprise a static seal adapted to form a hermetic seal between the housing and the vessel.

The housing may have a recess adapted to receive the reciprocating means.

The housing may be a top hat flange located coaxially with at least part of the reciprocating means.

Optionally the drive means forms at least part of the housing.

Alternatively, the drive means has a recess adapted to receive the housing.

The drive means may be operatively attached to the vessel. For example, the drive means may form part of a detachable housing.

Alternatively, the drive means may be detached from the vessel. For example, the drive means may be a magnet which is physically detached (i.e., not in physical contact) with the vessel.

In a further alternative, the drive means is integral to the vessel. For example, the drive means may form part of the sidewall, top or base of the vessel.

Optionally the drive means has a recess adapted to receive the reciprocating means.

The apparatus may further comprise an oscillator adapted to impart oscillatory motion on the drive means.

Optionally the oscillator is a flexible linear oscillator.

The flexible linear oscillator may be adapted to alter the phase of the at least one magnet such that the at least one magnet will cause alternation between attraction and repulsion of the reciprocating means.

Optionally the apparatus further comprises biasing means which act to bias the actuator in the opposite direction

to that in which it is moved by the magnetic forces acting upon it.

Optionally the biasing means is attached to a suitable internal surface of the vessel.

Alternatively the biasing means is attached to a suitable area of the actuator.

^' A method for applying oscillatory motion to at least one substance in a vessel, the method comprising the steps of: imparting linear motion on a reciprocating means using a drive means; and imparting reciprocating motion to the at least one substance using the reciprocating means, wherein at least part of the linear motion is imparted by magnetic coupling of the reciprocating means and the drive means.

Optionally the method comprises the further step of changing the pressure within a defined reaction or mixing zone in a vessel.

The pressure can be altered such that it is either above or below atmospheric pressure. That is, the method facilitates reactions and or mixing under positive or negative pressure.

Preferably at least one of the reciprocating means and the drive means comprises at least one magnet.

Optionally the method comprises the further step of altering the phase of the at least one magnet such that the reciprocating means oscillates.

Alternatively the method comprises the further step of reciprocating the drive means such that the reciprocating means oscillates.

Brief Description of Drawings

The present invention will now be described by way of example only, with reference to the accompanying drawings in which:

Figure 1 shows a schematic representation of a batch oscillatory baffled apparatus of the present invention;

Figure 2 shows a cut-away view of a batch oscillatory baffled apparatus of the present invention; and

Figure 3 shows a plan view of a continuous oscillatory baffled apparatus of the present invention.

Modes for Carrying Out the Invention

Referring to Figure 1, in this embodiment of the invention there is generally depicted at 101 a batch oscillatory baffled apparatus. The oscillatory baffled apparatus 101 comprises a vessel 102 on top of which is located a top hat flange 103. Located externally to the vessel 102 and coaxially to the top hat flange 103 is a permanent magnet 104. Between the top hat flange 103 and the vessel 102 there is positioned a seal (not shown) .

The seal is positioned between two static components of the apparatus. Inside the vessel 102 there is positioned a part magnetic rod 105, coaxial to both the top hat flange 103 and the permanent magnet 104. The part magnetic rod has a magnetic area and a non-magnetic area.

Also inside the vessel 102, attached to the part magnetic rod 105, is a baffle set 106 which comprises annular baffles 107 that extend radially inwards from the sides of the vessel 102. The baffles 107 are held in a substantially parallel position by rails 108.

The permanent magnet can be attached to an external actuator, which mechanically imparts movement on the magnet. The part magnetic rod inside the vessel will move in accordance with movement of the permanent magnet. In this example the external actuator is connected to a flexible linear oscillator and a control box, which control the movement of the permanent magnet. The external actuator can also be connected to a conventional flywheel arrangement which controls the movement of the permanent magnet. Alternatively, the magnet is an electromagnet which is connected to a control box, the oscillations being controlled by the control box.

Referring now to Figure 2, there is shown a cut-away illustration of an embodiment of the invention, similar to that in Figure 1. Generally depicted at 201 is a batch oscillatory baffled apparatus. The oscillatory baffled apparatus 201 comprises a vessel 202 on top of which is located a top hat flange 203. Located externally to the vessel 202 and coaxially to the top hat flange 203 is a permanent magnet 204. Between the top '

hat flange 203 and the vessel 202 there is positioned a seal 209, and as such the seal 209 is positioned between two static components of the apparatus. Holding together the top hat flange 203, seal 209 and vessel arrangement 202 are connecting pins 210. Inside the vessel 202 there is positioned a part magnetic rod 205, coaxial to both the top hat flange 203 and the permanent magnet 204. In this example the part magnetic rod 205 has a clearance of approximately 1 to 2 mm relative to the top hat flange 203. The part magnetic rod 205 has a magnetic area 211 and a non-magnetic area 212.

Also inside the vessel 202, attached to the part magnetic rod 205, is a baffle set 206 which comprises annular baffles 207 that extend radially inwards from the sides of the vessel 201. The baffles 207 are held in a substantially parallel position by rails 208.

The connecting pins normally consist of nuts and bolts. As an alternative, the top hat flange can thread onto the vessel, creating a closed system without the use of connecting pins. The top hat flange and the vessel are connected to form a hermetically sealed unit.

Referring now to Figure 3, there is shown at 301 a plan view of a continuous oscillatory baffled reactor (COBR) embodiment of the present invention. The COBR 301 comprises a vessel 302, fluidly connected to a feed tank 313. Between the feed tank 313 and the vessel 302 there . is located pump 314, a control valve 315, and a rotameter 316. The pump 314, control valve 315 and rotameter 316 fluidly connect the feed tank 313 to the vessel 302. An

access port 317 is provided to allow the addition of a second reactant.

At a proximal end of the vessel 302 there is positioned an oscillator unit 318. The oscillator unit 318 consists of a magnetically susceptible actuator 305 comprising a reciprocating shaft and a piston, magnetically coupled to reciprocating magnets 304. Oscillatory motion is achieved by moving the magnets 304 up and down outside the oscillator unit 318. The oscillator unit 318 is sealed using a standard static seal (not shown) . Products are collected in a product tank 319, at a distal end of the vessel 302.

The COBR 301 also comprises a series of orificed plates or annular baffles 307 that extend radially inwards from the sides of the vessel 302. The baffles 307 are held in a substantially parallel position by rails 308.

For exothermic or endothermic as well as adiabatic operations, jackets 320 along the COBR are utilised to heat or cool a reaction mixture within the COBR 301.

The embodiments depicted in Figures 2 and 3 can be controlled in a similar manner as described for the embodiment of Figure 1.

Use of the apparatus of Figures 1 and 2 will now be described with reference to the mixing of two liquids under positive pressure. In this operation, a first fluid and second fluid are charged into the batch oscillatory baffled apparatus, and mixing takes place by reciprocating the baffle set using the internal part

magnetic rod and the external magnet. The internal part magnetic rod and the external magnet are attracted to each other. The external magnet is physically moved up and down and the internal part magnetic rod moves up and down in unison. This imparts motion on the contents of the vessel via the baffle set, to which the internal part magnetic rod is attached. The pressure inside the vessel is then raised to any positive value and can be greater than 50 Bar using a type of fluid, including a gas, and the oscillation is continued.

Use of the apparatus of Figure 3 will now be described with reference to the mixing of two fluids under positive pressure. A first reactant is fed to the vessel from the feed tank via the pump, the control valve and the rotameter. A second reactant is then added into the vessel via an access port. For reactions carried out under pressure, a fluid is used to pressurise the COBR apparatus so that a given pressure is achieved within the COBR apparatus (inclusive of the oscillator unit) .

Mixing takes place by reciprocating the oscillator unit, which comprises a magnetically susceptible material, and the external magnet. The internal oscillator unit and the external magnet are attracted to each other. The external magnet is physically moved up and down and the internal oscillator unit moves up and down in unison. This imparts motion on the contents of the vessel. The contents are mixed efficiently via the baffles that are fixed to the inside of the vessel.

In the apparatus of the prior art it is extremely difficult to set the pressure inside an oscillatory

baffled reactor to greater than 50 Bar as a dynamic seal will not withstand such high pressure for a sufficient time period. In contrast, the apparatus of the present invention is able to withstand both reduced and elevated pressures, or corrosive fluids, for any length of time.

The internal part magnetic rod acts as a reciprocating means and forms part of an actuator. In particular, the internal part magnetic rod acts as a reciprocating shaft which is connected to a baffle set. The actuator applies linear motion to the substance contained in the vessel. In this embodiment the external magnet is physically separated from the vessel. However, it will be appreciated that the magnet need not be limited to this embodiment and could in fact be in contact, or partial contact, or integral to the vessel.

In one embodiment the reciprocating means is a magnetic rod where substantially the entire rod is a magnet. Alternatively, a half, a quarter, or some other incremental section of the reciprocating means is a magnet.

In an alternative embodiment, the apparatus is a continuous oscillatory baffled reactor with static baffles, and the actuator comprises a reciprocating shaft connected to a piston-type arrangement.

In a further embodiment, the external magnet is a component part of the apparatus and may, for example, be located in the top hat flange. Alternatively the flange itself may be magnetic; either electric or permanent magnetic form.

In a yet further embodiment, the internal part magnetic rod is not required. In this embodiment the magnet acts on the baffle set itself. The baffle set may also comprise magnets of either electric or permanent magnetic form.

Further magnets may be incorporated into the vessel to repel and/or attract at least part of the reciprocating means.

In one embodiment, the external magnet remains static .and attracts the internal magnetic rod which is biased away from the external magnet by virtue of a biasing means, for example a spring. Alternatively, the external magnet remains static and repels the internal magnetic rod which is biased towards the external magnet by the biasing means. In these embodiments one of the external and internal magnets can be replaced by a ferromagnetic material, for example iron. A ferromagnetic material may also be added in addition to the magnets to increase the field strength. The biasing means may be attached to a suitable internal surface of the vessel - such as an upper or lower internal surface. Also, the biasing means may be attached to a suitable area of the actuator - such as an area that comes into close proximity to the upper or lower surfaces of the vessel when in use.

In the examples described, the external magnet or ferromagnetic material acts as a drive unit or drive means, and is magnetically coupled to the actuator, imparting motion thereto. Therefore, it will be understood that the drive unit or drive means can be a

material which interacts with a magnet or ferromagnetic material that forms part of the actuator.

In a further embodiment, the magnet or ferromagnetic material is integral to the vessel, forming part of the sidewall, top or base of the vessel, and is magnetically coupled with the actuator (for example, part of a piston or baffle set) located inside the vessel. In this embodiment the magnet or ferromagnetic material integral to the vessel acts as the drive means.

In a still further embodiment, the magnet (acting as a drive unit or drive means) is physically detached from the vessel and is magnetically coupled with the actuator (for example, part of a piston or baffle set) located inside the vessel. The drive unit is located around the main body of the vessel, and controls oscillation inside the vessel by being switched on and off, or by switching the phase of the magnet. In an alternative embodiment the magnet is located inside the vessel as part of the actuator (for example, part of a piston or baffle set) . In a further alternative, the drive unit is located around the main body of the vessel, and controls oscillation inside the vessel by being mechanically reciprocated using a conventional or a linear oscillator.

In a further embodiment the drive unit is part of the top hat flange, and so forms an integral component part of the vessel (i.e. it is not physically separated from the vessel when in use) . In this embodiment the drive unit comprises a magnet, in which case the reciprocating means comprises either a magnet or a magnetically susceptible material. Alternatively, the drive unit comprises a

magnetically susceptible material, in which case the reciprocating means comprises a magnet.

The magnets used can be permanent magnets or electromagnets. In one embodiment, the drive unit is an electromagnet and the reciprocating means is an actuator that comprises a magnetically susceptible material. The electromagnet can be oscillated between "on" and "off". When switched "on" the electromagnet attracts the actuator, and when switched "off" the electromagnet does not attract the oscillator. Alternatively, the electromagnet can repel the actuator when it is switched "on". In a further alternative, the electromagnet can repel the actuator when switched to a first polarisation and attract the actuator when switched to a second polarisation. The "on" and "off" periods and the wave formats can precisely be controlled.

The apparatus of the present invention can be used to impart linear motion and mixing on a substance. The substance can be a mixture of miscible or immiscible fluids; a reaction mixture of a chemical reaction; a dispersion, suspension, emulsion or micro-emulsion; or any other suitable material with at least some fluid properties including gaseous mixtures.

Neither the reciprocating means, nor any of its moving attachments, pass from inside the vessel to the external environment or vice versa. Therefore, the use of a dynamic seal is avoided.

In a further embodiment, the apparatus of the present invention may be constructed without a vessel. The

apparatus may then be applied to an existing vessel, being sealed to the existing vessel in accordance with standard practices. For example, the apparatus of the present invention may be fitted to a standard laboratory beaker, round-bottomed flask, Schlenk flask, or tank. The apparatus of the present invention lends itself to miniaturisation and therefore can be used with ^' standard small scale laboratory equipment. This is in contrast to known oscillatory baffled apparatus which has proved difficult to miniaturise due to the engineering challenges presented in producing a suitable dynamic seal, and producing effective oscillation, on a small scale.

The apparatus of the present invention facilitates the use of linear oscillators in reaction or mixing apparatus without the need for a seal around any moving parts (i.e. a dynamic seal) . In particular, no moving parts pass from inside the vessel area to outside the vessel area or vice versa. Therefore, the internal vessel area may be completely sealed from the external environment. This allows the apparatus to be used effectively for high and low pressure operations and operations involving multi- phases, corrosive fluids, processes which are not always feasible using the apparatus of the prior art.

In addition, as no moving parts pass through the seals used in the present apparatus, said seals do not require changing as regularly as those in known devices. Therefore the apparatus of the present invention circumvents the inconvenience, time and cost implications associated with regularly changing dynamic seals.

Industrial Applicability

The apparatus of the present invention can be used in the chemical, petroleum, process, pharmaceutical, cosmetic, bioscience, bioengineering, and food and associated industries. In particular, the use of present invention can be used to promote and maintain efficient mixing in a controlled environment in the aforementioned industrial or technical fields.

Improvements and modifications may be incorporated herein without deviating from the scope of the invention.