GB2461740A

GB2461740A - Separation by evaporation

Info

Publication number: GB2461740A
Application number: GB0811455A
Authority: GB
Inventors: Alan Macdonald; Robert Van Toor
Original assignee: OPERATIONAL GROUP Ltd
Current assignee: OPERATIONAL GROUP Ltd
Priority date: 2008-06-23
Filing date: 2008-06-23
Publication date: 2010-01-20
Anticipated expiration: 2028-06-23
Also published as: GB2461740B; WO2009156755A1; GB0811455D0

Abstract

A method of separating a solvent and/or volatile component from a solution and/or suspension and/or mixture. The method comprises feeding said solution/suspension/mixture to a vessel 3 and agitating to promote evaporation of said solvent/volatile component from the solution/suspension/mixture and conveying solvent/volatile vapour from the vessel. Also provided is an apparatus for separating solvent and/or volatile component from a solution and/or suspension and/or mixture. Preferably the solvent is separated from an ink solution. The agitation may be provided by a sparger (31, Fig 6) and an impeller (23, Fig 5) and the amount of agitation of the solution is controlled so as to control the rate of evaporation of solvent from solution. Also disclosed is a method of increasing a component content of a gas stream feed to an abatement plant comprising promoting evaporation and conveying component vapour from a vessel into a gas stream feed. Also disclosed is a method of processing a dirty solvent produced when parts of a print machine are washed wherein the dirty solvent comprises an ink solution.

Description

IMPROVEMENTS IN AND RELATING TO SOLVENT PROCESSING

FIELD OF INVENTION

The present invention relates to methods for separating solvent arid/ar volatile component from a solutori arid/or suspension and/or mixture, particularly but not exclusively to separating solvent from an ink solution.

The invention further relates to apparatus for separating solvent and/or volatile component from a solution and/or suspension and/or mixture, to methods of increasing the VOC content of a gas stream feed to an abatement plant, to methods of processing dirty solvent and to processing plants.

BACKGROUND TO INVENTION

The printing process involves the printing of solvent based inks or colours and lacquers onto paper and plastic film substrates in high speed print machines with dryers emitting evaporated solvents and hot air.

In known printing plants dryer emissions are collected in a central exhaust duct and led to an abatement plant. The exhaust air flow rate from a typical printing site ranges from 10,000 to 200,000 m3 hour', depending on the number of printing machines installed. Solvent content is variable between 1 and 6 g m3, this being determined by the print speed and ink/colour/lacquer coverage.

The abatement plant may be a thermal abatement plant such as a regenerative thermal oxidiser but may also be a recovery plant or biological treatment plant. In the case of a thermal abatement plant it is necessary to use considerable quantities of fuel to cause thermal abatement of the solvent which can be costly and an inefficient use of energy resources.

On completion of a particular printing job, unused ink/colour/lacquer solution/mixture still in the liquid phase is collected. Some inks/colours/lacquers are reusable on other print jobs but some are not and are collected.

Non reusable ink/colour/lacquer solutions can be disposed of by licensed contractors or more commonly are fed to a batch still for treatment. The batch still recovers the solvent for use as a cleaning solvent or for occasional reuse on a print machine. Recovered solvent is not contaminated with ink but is cross contaminated with other solvent which limits its application. In addition the still uses considerable amounts of energy to recover the solvent.

Accordingly, the present invention aims to address at least one disadvantage associated with the prior art whether discussed herein or otherwise.

SUMMARY OF INVENTION

According to a first aspect of the invention there is provided a method of separating a solvent and/or volatile component from a solution and/or suspension and/or mixture, wherein the method comprises feeding said solution/suspension/mixture to a vessel and agitating the solution/suspension/mixture so as to promote evaporation of said solvent/volatile component from the solution/ suspension/mixture and conveying solvent/volatile component vapour from the vessel.

Suitably, the method comprises agitating the solution/suspension/mixture so as to minimise settling and sticking and promote evaporation of said solvent/volatile component from the solution/suspension/mixture.

Suitably, there is provided a method of separating solvent from a solution, wherein the method comprises feeding said solution to a vessel and agitating the solution so as to promote evaporation of solvent from the solution and conveying solvent vapour from the vessel.

Suitably, there is provided a method of separating solvent from an ink solution, wherein the method comprises feeding said ink solution to a vessel and agitating the solution so as to promote evaporation of solvent from the solution and conveying solvent vapour from the vessel.

Suitably, references herein to "ink solution" encompass ink, colour, lacquer, adhesive and other coating solutions and/or suspensions and/or mixtures used in print machines.

Suitably, references herein to "ink solution" encompass solutions, suspensions and mixtures comprising a solvent and/or volatile component as a carrier for an ink, colour lacquer, adhesive or other coating component.

A solution suitable for processing by the method of the present invention may comprise a liquid mixture comprising solvent(s) together with ink and/or colour and/or lacquer and/or adhesive in solution or suspension or both. The method may comprise a method of separating solvent from a solution and/or suspension comprising an ink and/or colour and/or lacquer and/or adhesive.

For convenience, the first aspect of the invention will be further described with reference to the term "solvent" but it will be understood that unless specifically stated otherwise such references are also applicable to "volatile component". Similarly, for convenience, the first aspect of the invention will be further described with reference to the term "solution" but it will be understood that unless specifically stated otherwise such references are also applicable to "suspension" or "mixture".

Suitably, solvent vapour is conveyed from the vessel as a gas stream.

Suitably, the method comprises combining gas with the solvent vapour. Suitably, the method comprises conveying a gas and solvent vapour combination from the vessel.

Suitably, the method comprises combining air with the solvent vapour and conveying said combination from the vessel. The method may comprise combining a gas stream comprising solvent and air with the solvent vapour and conveying said combination from the vessel. The method may comprise combining exhaust air from a production area with the solvent vapour and conveying said combination from the vessel.

Suitably, the method comprises feeding a gas, suitably air, stream into the vessel and removing the solvent vapour in a gas, suitably air, stream.

Suitably, the method comprises feeding a gas, suitably air, into the solution in the vessel. Suitably, the method comprises feeding a gas, suitably air, into an area of the vessel above the solution. Suitably, the method comprises feedirag a gas, suitably air irito the solutiora iri the vessel and also into an area of the vessel above the solution.

Suitably, the method comprises feeding a first gas, suitably air, stream into the solution. Suitably, said first gas stream agitates the solution so as to enhance evaporation of solvent from the solution.

Suitably, the rate of introduction of the first gas stream into the solution is controlled to control the rate of evaporation of solvent from the solution. Thus the concentration of solvent vapour in the vessel may also be controlled. Suitably, the greater the rate of introduction of air into the solution the greater the rate of evaporation of solvent.

Suitably, the method comprises feeding a second gas, suitably air, stream into an area of the vessel above the solution. Suitably, said second gas stream carries solvent vapour from the vessel. Suitably, said second gas stream combines with solvent vapour and also with gas from said first gas stream and the combination is removed from the vessel.

Suitably, the rate of introduction of the second gas stream into the solution is controlled to control the concentration of solvent vapour in the vessel and also in the gas stream exiting the vesse]. SuitabiLy, the greater the rate of introduction of air into the vessel above the solution the lower the concentration of solvent vapour in the vessel. Suitably, the second gas stream acts to dilute the solvent in air concentration of the gas stream exitirig the vessel arid may thus ensure it remairas below explosive limits.

Suitably, the method comprises controlling the amount of agitation of the solution to control the rate of evaporation of solvent from the solution. Thus the concentration of solvent vapour in the vessel may also be controlled. Suitably, the greater the amount of agitation of the solution the greater the rate of evaporation of solvent.

Suitably, the method comprises agitating the solution by passing gas through it. Suitably, the method comprises agitating the solution by passing air through it.

Suitably, the method comprises agitating the solution by causing the solution to move. Suitably, the method comprises agitating the solution by mixing the solution.

Suitably, the method comprises agitating the solution by stirring the solution.

Suitably, the method comprises agitating the solution with agitating means. The agitating means may comprise any feature as described in relation to the second aspect hereafter. Suitably, the agitating means comprises a combination of a sparger and an impeller.

Suitably, the solvent comprises a volatile organic compound (VOC) . The solvent may comprise one or more of ethyl acetate, ethanol, propyl acetate and propanol.

Suitably, the method comprises conveying solvent vapour from the vessel and feeding it to an abatement plant, for example a thermal abatement plant. Suitably, the method comprises conveying a gas, suitably air, stream comprising solvent vapour from the vessel and feeding it to an abatement plant, for example a thermal abatement plant.

Suitably, the method comprises conveying solvent vapour from the vessel and combining it with a gas stream feed for an abatement plant, for example a thermal abatement plant so as to increase the solvent concentration of said gas stream.

Suitably, the method comprises conveying solvent vapour from the vessel and combining it with an exhaust gas stream from a production area and feeding it to an abatement plant. Suitably, the abatement plant comprises a regenerative thermal oxidiser.

Suitably, the method comprises removing an ink solution from a lower region of the vessel once solvent has been evaporated from the solution Suitably, the method comprises conveying ink from the vessel. Suitably, the method comprises conveying a solution of ink from the vessel wherein the solution comprises a higher concentration of ink than that of the ink solution fed into the vessel. The solution conveyed from the vesse] suitabiLy has a higher solids content than that fed to it.

Suitably, the method comprises feeding a solution having a solids content of 30% or less to the vessel, the solution may for example have a solJds content of around 15%.

Suitably, the method comprises conveying a solution which has a solids content of 40% or more from the vessel.

Suitably, the solution conveyed from the vessel has a solids content of 50% or more, for example 60% or more, for example around 65%.

Suitably, the method comprises conveying a solution from the vessel and feeding it to a still to separate further solvent from the solution.

Suitably, the method comprises blowing a gas, suitably air stream into the vessel above and/or into the solution.

Suitably the method comprises drawing a gas, suitably air, stream comprising solvent vapour from the vessel.

Suitably, the method comprises controlling the concentration of solvent vapour in the vessel to below 50% of the LEL maximum. Suitably, the method comprises controlling the solvent in air concentration in the vessel to between 10% and 45% of the LEL maximum.

Suitably, the method comprises controlling the concentration of solvent vapour in the outlet gas stream to below 50% of the LEL maximum. Suitably, the method comprises controlling the solvent in air concentration in the outlet gas stream to between 10% and 45% of the LEL maximum.

Suitably, the method comprises evaporating solvent at a low temperature and the evaporated vapours may thus not contain any high boiling contaminants or inks.

The method may comprise any feature as described hereafter in relation to the apparatus of the second aspect. The method may employ an apparatus according to the second aspect.

The method may comprise any feature as described in relation to the third, fourth and/or fifth aspect.

Suitably, the method comprises a method of separating solvent from an ink solution which ink solution comprises unused ink left over solution from a printing process.

The method may comprise a method of separating solvent from non-reusable ink collected in an ink collection tank.

Suitably, the method comprises evaporating solvent from ink collected from a print machine and feeding that solvent into the exhaust duct of the print machine which feeds to an abatement plant.

The method may comprise a method of separating solvent from an ink solution which ink solution comprises the dirty solvent solution from a parts washer.

Where the method comprises separating solvent from an ink solution which ink solution comprises the dirty solvent solution from a parts washer the remaining ink solution having a lower solvent content may then be discharged into a still to be further processed in the same manner as the entirety of the dirty solvent solution would be in a known process According to a second aspect of the present invention there is provided an apparatus for separating solvent and/or volatile component from a solution and/or suspension and/or mixture, wherein the apparatus comprises a vessel for holding a quantity of solution/suspension/mixture and wherein the apparatus further comprises agitating means for agitating the solution/suspension/mixture in the vessel so as to promote evaporation of solvent/volatile component from the solution/suspension/mixture which can then be conveyed from the vessel via a gas stream outlet.

Suitably, the agitating means is arranged to agitate the solution/suspension/mixture so as to minimise settling and sticking and promote evaporation of said solvent/volatile component from the solution/suspension/mixture.

Suitably, there is provided an apparatus for separating solvent from a solution, wherein the apparatus comprises a vessel for holding a quantity of solution and wherein the apparatus further comprises agitating means for agitating solution in the vessel so as to promote evaporation of solvent from the solution which can then be conveyed from the vessel via a gas stream outlet.

A solution suitable for processing by the apparatus of the present invention may comprise a liquid mixture comprising solvent(s) together with ink and/or colour and/or lacquer and/or adhesive in solution or suspension or both.

For convenience, the second aspect of the invention will be further described with reference to the term "solvent" but it will be understood that unless specifically stated otherwise such references are also applicable to "volatile component". Similarly, for convenience, the second aspect of the invention will be further described with reference to the term "solution" but it will be understood that unless specifically stated otherwise such references are also applicable to "suspension" or "mixture".

Suitably, the solvent comprises a volatile organic compound (VOC) . Suitably, the solution comprises ink as a solute. The apparatus may be used to separate a VOC from an ink and VOC solution.

Suitably, the apparatus is arranged to provide a head space above the solution level for accommodating evaporated solvent. Suitably, the apparatus is provided with means for controlling the solution level to ensure that a working headspace is maintained.

Suitably, the agitating means comprises means for agitating the solution by passing gas through it.

Suitably, the agitating means comprises means for agitating the solution by passing air through it.

Suitably, the agitating means comprises a gas, suitably air, injector. Suitably, the agitating means comprises a sparger. Suitably, the agitating means comprises a sparger for bubbling air through the solution. The agitating means may comprise a diffuser.

Suitably, the agitating means comprises means for causing the solution to move. Suitably, the agitating means comprises means for mixing the solution. Suitably, the agitating means comprises means for stirring the solution.

Suitably, the agitating means comprises an impeller.

Suitably, the agitating means comprises a combination of a sparger and an impeller.

The agitating means may comprise a diffuser and/or stator together with an impeller. The impeller may comprise a head mounted on a rotatable shaft and having a plurality of blades. Suitably, the blades are arranged to extend radially relative to the impeller shaft. A diffuser may comprise a plurality of baffles arranged around the impeller head. Suitably, the baffles are arranged to extend radially relative to the impeller shaft.

Suitably, the apparatus comprises a solution inlet to the vessel. Suitably, the apparatus comprises a gas stream inlet to the vessel. Suitably, the apparatus comprises a gas stream outlet from the vessel. Suitably, the apparatus comprises a liquid outlet from the vessel.

Suitably, the apparatus comprises first and second gas stream inlets to the vessel. The first gas stream inlet suitably comprises an inlet into solution in the vessel.

The second gas stream inlet suitably comprises an inlet into the vessel above the solution.

Suitably, the apparatus comprises a solution inlet and a gas stream inlet to the vessel and a gas stream outlet and a liquid outlet from the vessel. Suitably, the apparatus comprises a solution inlet and first and second gas stream inlets to the vessel and a gas stream outlet and a liquid outlet from the vessel.

Suitably, a gas stream inlet comprises an air inlet.

Suitably, the first gas stream inlet comprises an air stream inlet. Suitably, the second gas stream inlet comprises an air stream inlet.

Suitably, a gas stream inlet to the vessel is provided by the agitating means, suitably by a sparger. Suitably, the first gas stream inlet to the vessel is provided by the agitating means, suitably by a sparger.

Suitably, the gas stream outlet from the vessel comprises an air and solvent outlet. Suitably, the gas stream outlet comprises an air and VOC outlet.

Suitably, the liquid outlet is located towards the base of the vessel. Suitably, the liquid outlet is arranged to provide an outlet for a liquid having a lower solvent content than that fed into the vessel via the solution inlet. The liquid outlet suitably provides an outlet for a solute rich stream.

Suitably, the vessel does not comprise a round sided vessel. Suitably, the vessel comprises a substantially rectangular sided vessel. Suitably, the vessel comprises a substantially square sided vessel.

Suitably, the vessel is arranged to substantially prevent rotational movement of the solution with an impeller.

Suitably, the vessel has substantially planar walls meeting at corners such that an impeller throws solution against the walls rather than causing solution to rotate with the impeller and move along a circular path to form a vortex.

Suitably, the vessel comprises a chamber housing an agitator and into which solution is introduced via a feed chamber. The feed chamber suitably has an inlet for solution and an opening into the vessel, which opening provides the solution inlet to the vessel. Solution in the feed chamber is suitably not subjected to the same turbulence as solution in the main chamber and so a solution level detector is provided in the feed chamber so as to control the level of solution in the vessel.

Suitably, the apparatus comprises an LEL detector.

Suitably, the apparatus is arranged to take action to control the solvent vapour concentration in the vessel to lie below 50% of the LEL maximum. Suitably, the apparatus is arranged to take action to control the solvent in air concentration in the vessel to lie between 10% and 45% of the LEL maximum.

Suitably, the apparatus is arranged to take action to control the solvent vapour concentration in the gas outlet stream to lie below 50% of the LEL maximum. Suitably, the apparatus is arranged to take action to control the solvent in air concentration in gas outlet stream to lie between 10% and 45% of the LEL maximum.

The vessel may comprise a jacketed vessel and the jacket may comprise heat exchange means for cooling a cooling medium, such as water, which may be circulated around parts of a plant, for example parts of a print machine.

The heat exchange means may help to prevent the contents of the vessel becoming overly cooled by the endothermic evaporation process and may also usefully allow other parts of a printing plant to be cooled.

During the solvent vaporisation process the liquid solution may cool to around 6°C. A heating/cooling jacket installed around the vessel may thus be used to cool circulated water down to around 8°C which can be used in place of water from a chilled water plant for web cooling of a print machine.

The apparatus may comprise any feature as described in relation to the first aspect. The apparatus may be employed in a method according to the first aspect.

The apparatus may comprise any feature as described in relation to the third, fourth and/or fifth aspect.

According to a third aspect of the present invention there is provided a method of increasing a solvent and/or volatile component content of a gas stream feed to an abatement plant, said method comprising feeding a solution and/or suspension an/or mixture to a vessel and promoting evaporation of solvent/volatile component from the solution/ suspension/mixture and conveying solvent/volatile component vapour from the vessel into said gas stream feed.

Suitably, said solvent and/or volatile component comprises a VOC. Suitably, the method comprises a method of increasing the VOC content of a gas stream feed to an abatement plant.

Suitably, the abatement plant comprises a thermal abatement plant. Alternatively, the abatement plant may comprise a recovery plant.

Suitably, said solution and/or suspension and/or mixture comprises an ink solution. Suitably, the method comprises feeding an ink solution to a vessel.

Suitably, there is provided a method of increasing the VOC content of a gas stream feed to an abatement plant, said method comprising feeding an ink solution to a vessel and promoting evaporation of solvent from the solution and conveying solvent vapour from the vessel into said gas stream feed.

Suitably, the method comprises any feature according to the first aspect. Suitably, the method comprises a method according to the first aspect.

Suitably, the method comprises any feature according to the second aspect. Suitably the method comprises an apparatus according to the second aspect.

According to a fourth aspect of the present invention there is provided a method of processing dirty solvent which comprises an ink solution and/or suspension and which dirty solvent is produced when parts of a print machine are washed, said method comprising feeding the dirty solvent comprising the ink solution/suspension to a vessel and promoting evaporation of solvent from the solution/suspension and conveying solvent vapour from the vessel and separately conveying an ink solution/suspension having a reduced solvent content from the vessel for further processing.

Suitably, there is provided a method of processing dirty solvent which comprises an ink solution and which dirty solvent is produced when parts of a print machine are washed, said method comprising feeding the dirty solvent comprising the ink solution to a vessel and promoting evaporation of solvent from the solution and conveying solvent vapour from the vessel and separately conveying an ink solution having a reduced solvent content from the vessel for further processing.

Suitably, said further processing of the ink solution having a reduced solvent content comprises using a still.

Suitably, said evaporated solvent is conveyed to an abatement plant, for example a thermal abatement plant.

Alternatively, said evaporated solvent may be recovered for re-use in a washing operation. The evaporated solvent may be passed to an adsorber or condenser to recover solvent from a gas stream such that the solvent can be re-used.

Suitably, the method comprises any feature according to the third aspect. Suitably the method comprises a method according to the third aspect.

According to a fifth aspect of the present invention there is provided a process plant comprising means for processing solutions wherein said plant comprises an apparatus and/or operates according to a method of any of the first, second, third or fourth aspects.

BRIEF DESCRIPTION OF DRAWINGS

The present invention will now be illustrated by way of example with reference to the accompanying drawings in which: Figure 1 is a front view showing hidden detail of an apparatus for separating solvent from a solution; Figure 2 is a left side view showing hidden detail of the apparatus of Figure 1; Figure 3 is a top view showing hidden detail of the apparatus of Figure 1; Figure 4 is a front view of an impeller of the apparatus of Figure 1; Figure 5 is an underside view of the impeller of Figure 4; Figure 6 is a front view of a sparger and diffuser of the apparatus of Figure 1; Figure 7 is an underside view of the sparger and diffuser of Figure 6; and Figure 8 is a schematic of an apparatus for separating solvent from an ink solution which incorporates the apparatus of Figure 1.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Figures 1 to 3 illustrate an apparatus 1 for separating solvent from a solution, for example for separating VOC's from an ink solution. The apparatus 1 comprises a vessel 3 for containing a solution 5 and is arranged to separate solvent from the solution.

Control means (not shown) ensure that a headspace 7 is maintained above the solution 5 SO that solvent vapour can occupy that head space. The apparatus 1 further comprises agitating means comprising an agitator 9 for agitating the solution 5 to promote evaporation of solvent from the solution 5.

The apparatus 1 comprises a first gas stream inlet 11 to the vessel 3 and a second gas stream inlet 13 to the vessel as well as a solution inlet 15 to the vessel, a gas stream outlet 17 from the vessel and a solution outlet 19 from the vessel.

The first gas stream inlet 11 is provided by the agitator 9 and feeds gas into the solution 5. The second gas stream inlet 13 is arranged above the solution 5 and introduces gas into the headspace 7.

In the illustrated embodiment the gas introduced through the first and second gas stream inlets 11, 13 is air. In an alternative embodiment (not illustrated) the gas introduced comprises exhaust gas from a production area which comprises air and solvent vapour.

As illustrated by Figure 1 the flow of air to the first gas stream inlet 11 is controlled by a control damper 21.

The damper 21 controls the flow of air into the solution 5. Since the flow of air through the solution 5 promotes evaporation of the solvent the damper 21 can control the rate of evaporation of the solvent and thus the concentration of solvent vapour in the head space 7 of the vessel 3. For example, if the concentration of solvent vapour in the headspace 7 is lower than desired the rate of air flow into the solution can be increased to increase the rate of solvent evaporation.

The flow of air to the second gas stream inlet 13 can also be controlled using the modulating air damper linked to the LEL detector control circuit which controls the flow of air into the headspace 7 and thus can also control the concentration of solvent in the headspace. The LEL sensor passes a control signal to the damper as indicated by dotted line LELC in order to control the LEL of vapour within the vessel within safe operating limits. For example, if the concentration of solvent vapour in the headspace 7 is too high the rate of air flow into the headspace can be increased to dilute the solvent vapour with air.

As best illustrated by Figure 4 to 7 the agitator 9 comprises an impeller 23. The impeller 23 comprises a head 25 having blades 27 and which is mounted on a shaft 29. The agitator also comprises a sparger 31 having an opening 33 arranged to lie below the level of the solution in use and to provide said first gas outlet 11. Mounted to the sparger 31 is a diffuser 35 having baffles 37.

The sparger 31 comprises a cylindrical wall which surrounds the shaft 29 of the impeller 23. The impeller 23 is driven by a motor 39.

The rate of operation of the impeller can be controlled and that in turn can control the rate of evaporation of solvent. The greater the speed of the impeller the greater the rate of solvent evaporation may be.

As shown by Figure 2 the vessel 3 comprises a chamber 41 housing the agitator 9 which is fed via a feed chamber 43 into which solution is introduced via inlet 45. The feed chamber 43 has an opening near the base and is protected from the dynamic forces in the agitated vessel by a steel distribution box from where issues the feed into the main chamber 41 which provides the solution inlet 15 to the vessel 3. Solution in the feed chamber 41 is not subjected to the same turbulence as solution in the main chamber 43 and so a solution level detector is provided in the feed chamber 41 50 as to indicate the level of solution in the vessel 3.

The apparatus 1 is controlled by a control cabinet 47 located in a safe area. The apparatus 1 further comprises a viewing port 49 to allow visual inspection of the inside of the vessel 3.

Figure 8 is a schematic illustrating an apparatus 101 for separating solvent from an ink solution which incorporates the apparatus of Figures 1 to 3. Like parts are labelled accordingly.

The apparatus 101 comprises an apparatus 1 for separating solvent from a solution which comprises a vessel 3. The vessel 3 defines a chamber 41 which holds a quantity of solution 5. The vessel is supplied with an input solution S of solvent and ink via a feed chamber 43. The feed chamber 43 has an inlet (not shown) 45 for receiving a solution stream 45a. The feed chamber 43 is in communication with the chamber 41 of the vessel 3 via a solution inlet (not shown) for receiving solution stream 15a.

Located in the vessel 3 is an agitator 9 which comprises an impeller and sparger (not shown in detail) . The impeller 23 is driven by a motor 39.

The sparger is fed with pressurised air from the air blower via first gas stream ha which exits the sparger into the vessel via a first gas inlet (not shown) which feeds air into the solution 5. Air is also fed into the headspace 7 of the vessel 3 via second gas stream 13a which enters the vessel via a second gas inlet (not shown) Solvent vapour and air are conveyed from the vessel 3 in a gas stream 17a which exits the vessel via a gas stream outlet (not shown) . An ink solution having a reduced solvent content exits the vessel via a solution outlet (not shown) which feeds solution stream 19a. This is taken away as residue R which is further processed to extract remaining solvent.

The first gas inlet stream ha comprises a driven air stream which is driven by blower 103 powered by motor 105.

The gas outlet stream comprises a driven air stream which is driven by extractor fan 107 powered by motor 109.

In the illustrated embodiment the first and second gas inlet streams ha and 13a are fed with fresh air FA. In an alternative embodiment as shown by dotted line OEA the first and second gas streams may optionally have some or all of their composition comprised of exhaust air EA taken from a production area. Such exhaust air EA comprises a combination of air and solvent vapour.

The outlet gas stream 17a is fed into an exhaust gas stream EA from a production area so as to form an exhaust gas stream SEA having an increased solvent concentration.

That exhaust gas stream SEA is then fed to a thermal abatement plant. The increased level of solvent increases the combustibility of the exhaust gas stream meaning less additional fuel must be fed to the abatement plant in order to combust the exhaust gas stream.

In an alternative embodiment (not shown) a solvent recovery type abatement plant is used instead of a thermal abatement plant and the final recovered solvent quantity is augmented by the vaporised solvents.

The apparatus 101 further comprises various control dampers, valves and sensors which are briefly identified as follows: 111 -isolation damper for second inlet gas stream 13a; 113 -isolation damper for outlet gas stream 17a; 115 -isolation and control valve for first inlet gas stream ha; 117 -L.E.L. measurement, this can be done by either of catalytic, infra red, FID or flame thermal technology together with the necessary control and alarm signals; 119 -level indicator; 121 -high level switch; 123 -low level switch; -input valve for solution stream 45a; 127 -outlet valve for solution outlet stream 19a; 129 -rotational speed sensor; and 131 -bearing temperature sensor.

As well as being used to separate solvent from a solution it will be understood that the apparatus of this embodiment is used to increase the VOC content of a gas stream being fed to a thermal abatement plant (not shown) which may increase the efficiency of that plant.

The operation of the apparatus 1 will be better understood with reference to the following example of its operation.

An operator presses a start button on the control panel 47.

A PLC (programmable linear controller) runs through status checks and if low level switch 123 signals a low liquid level in the vessel 3 then the inlet valve 125 will open and a feed pump (not shown) will start to fill the vessel with solution 5.

When the liquid level reaches the high level switch 121, the feed pump will stop and the inlet valve 125 will close.

In the event that the liquid level continues to rise, the high-high alarm 121 will close the supply valve 125 and the drain valve 127 will open. In an alternative embodiment (not shown) the contents will be allowed to overflow into a catch tank beneath. The safest option would be decided during site specific risk assessment.

When the operating liquid level is reached the PLC will check that the abatement plant (not shown) is ready and ready to accept solvent vapour.

When ready, air dampers 111 and 113 will open to admit dilution air to the vessel until the LEL sensor 117 determines a safe level has been reached.

Fan 107 will start up and draw air across the vessel and back into the central exhaust header CEA duct.

Blower 103 will start and valve 115 will open allowing air from FA or CEA to enter the agitator. The agitator will also be caused to rotate by operation of the motor.

In an alternative embodiment (not shown), rather than being motorised the agitator is driven by a compressed air turbine. Accordingly, at this stage an agitator air valve will open admitting compressed air to the turbine hence to rotate the shaft and agitator.

When in operation, the LEL sensor 117 will automatically ensure the LEL in the exhaust will not exceed 45% of the solvent LEL by modulating the air valve 115.

If the LEL exceeds 45% then an alarm will be given and the agitator stopped. If the LEL reaches 50% then the system will be shutdown in a controlled and safe manner.

There will also be an emergency stop button which will initiate the safe shutdown sequence.

When the contents have evaporated to low level switch 123 the feed pump (not shown) will start to refill the vessel and the process will start again.

When evaporation requirements are finished, or if the process needs to be stopped, the operator can press the stop button which will initiate the safe shutdown sequence.

When evaporation requirements are complete and are not anticipated to resume for more than 6 hours, then the contents can be drained by opening valve 127.

In an alternative embodiment (not shown) rather than being supplied with unused ink solution left over after a printing process the apparatus 1 may be fed with a dirty solvent solution comprising ink and solvent which is produced when print machine parts are washed. In a known method such dirty solvent would be fed to a batch still to separate off solvent. According to an embodiment of the invention (not illustrated) the dirty solvent can instead be fed to the apparatus 1. Solvent is evaporated from the solution in the apparatus 1 and in one embodiment the solvent gas stream is be fed to an abatement plant (not shown) . In an alternative embodiment the solvent gas stream is fed to a solvent recovery type abatement plant which could be an adsorber or a condenser (not shown) to allow it to be recovered for re-use in the printing process or for cleaning purposes. In both embodiments the solution from which solvent is evaporated is then further processed in a batch still to recover further solvent.

It will be appreciated that preferred embodiments of the present invention may have advantageous features.

The method and/or apparatus of preferred embodiments may allow an exhaust to the abatement system to be enriched with additional vaporised solvents which may reduce gas/support fuel usage by allowing the auto-thermal point to be reached more regularly. This feature may be provided on a continuous or as required basis.

The method and/or apparatus of preferred embodiments of the invention may reduce the volume of unused ink to be handled in a batch still which may save energy and increase safety.

For sites which do not use a batch still the method and apparatus of preferred embodiments of the invention may reduce the quantity of waste ink and solvent to be disposed of offsite by licensed collectors. The waste may contain more solids and a lot less liquid solvent.

The method and/or apparatus of preferred embodiments of the invention may utilise the cooling of liquid in a vessel during the vaporisation process to cool liquid passed through a cooling/heating jacket which may be used in place of water from the chilled water plant for cooling applications such as web cooling on a print machine.

Therefore there may be a saving of energy otherwise needed to run the chilled water plant.

The method and/or apparatus of preferred embodiments of the invention may encourage prompt collection of unused inks and reduces fugitive emissions which arise when ink drums are left around a factory or in ink stores.

The method and/or apparatus of preferred embodiments of the invention may reduce the use of fossil fuel in the abatement plant, hence reduced costs and CO2 profile.

The method and/or apparatus of preferred embodiments of the invention may reduce the use of electricity and energy in a batch still, hence reduced costs and CO2 profile.

The method and/or apparatus of preferred embodiments of the invention may reduce the potential for fugitive emissions of VOC and the environment effects of their uncontrolled conversion to greenhouse gases.

The method and/or apparatus of preferred embodiments of the invention may provide an on site solutions to reducing the volume of waste emanating from the site.

Attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s) . The invention extends to any novel one, or any novel combination, of the features

disclosed in this specification (including any

accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

Claims 1. A method of separating a solvent and/or volatile component from a solution and/or suspension and/or mixture, wherein the method comprises feeding said so1utori/susperisori/mixture to a vessel arid agitatrag the solution/suspension/mixture so as to promote evaporation of said solvent/volatile component from the solution/suspension/mixture and conveying solvent/volatile component vapour from the vessel.
2. A method according to claim 1, wherein the method comprises separating solvent from a solution and wherein the method comprises feeding said solution to a vessel and agitating the solution so as to promote evaporation of solvent from the solution and conveying Q solvent vapour from the vessel. C)

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3. A method according to claim 1 or 2, wherein the method comprises separating solvent from an ink solution and wherein the method comprises feeding said ink solution to a vessel and agitating the solution so as to promote evaporation of solvent from the solution and conveying solvent vapour from the vessel.
4. A method according to any preceding claim, wherein the method comprises feeding a gas stream into the vessel and removing the solvent vapour in a gas stream.
5. A method according to any preceding claim, wherein the method comprises feeding a first air stream into the so]ut ion.
6. A method accordingly to claim 5, wherein the rate of introduction of the first air stream into the solution is controlled to control the rate of evaporation of solvent from the solution.
7. A method according to any preceding claim, wherein the method comprises feeding a second air stream into an area of the vessel above the solution.
8. A method according to claim 7, wherein the rate ofintroduction of the second air stream into thesolution is controlled to control the concentration of solvent vapour in the vessel and also in the gas stream exiting the vessel. (0

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9. A method according to any preceding claim, wherein the (Y) method comprises controlling the amount of agitation (\,J of the solution to control the rate of evaporation of solvent from the solution.
10. A method according to any preceding claim, wherein the method comprises agitating the solution with agitating means.
11. A method according to claim 10, wherein the agitating means comprises a combination of a sparger and an impeller.
12. A method according to any preceding claim, wherein the method comprises conveying solvent vapour from the vessel and feeding it to an abatement plant.
13. A method according to any preceding claim, wherein the method comprises conveying solvent vapour from the vessel and combining it with an exhaust gas stream from a production area and feeding it to an abatement plant.
14. A method according to any preceding claim, wherein the method comprises conveying a solution of ink from the vessel wherein the solution comprises a higher concentration of ink than that of the ink solution fed into the vessel.
15. A method according to any preceding claim, wherein the method comprises conveying a solution from the vessel and feeding it to a still to separate further solvent (0 from the solution.

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16. A method according to any preceding claim, wherein the C\J method comprises controlling the concentration of solvent vapour in the vessel to below 50% of the LEL maximum and wherein the method comprises controlling the concentration of solvent vapour in the outlet gas stream to below 50% of the LEL maximum.
17. An apparatus for separating solvent and/or volatile component from a solution and/or suspension and/or mixture, wherein the apparatus comprises a vessel for holding a quantity of solution/suspension/mixture and wherein the apparatus further comprises agitating means for agitating the solution/suspension/mixture in the vessel so as to promote evaporation of solvent/volatile component from the solution/suspension/mixture which can then be conveyed from the vessel via a gas stream outlet.
18. An apparatus according to claim 17, wherein the apparatus is arranged to provide a head space above the solution level for accommodating evaporated solvent and wherein the apparatus is provided with means for controlling the solution level to ensure that a working headspace is maintained.
19. An apparatus according to claim 17 or 18, wherein the agitating means comprises a combination of a sparger and an impeller. a)
20. An apparatus according to any of claims 17 to 19, (0 wherein the apparatus comprises first and second gas Q stream inlets to the vessel wherein the first gas () stream inlet comprises an inlet into solution in the C\J vessel and the second gas stream inlet comprises an inlet into the vessel above the solution.
21. An apparatus according to any of claims 17 to 20, wherein the apparatus comprises a solution inlet and first and second gas stream inlets to the vessel and a gas stream outlet and a liquid outlet from the vessel.
22. An apparatus according to any of claims 17 to 21, wherein the vessel comprises a substantially rectangular sided vessel.
23. An apparatus according to any of claims 17 to 22, wherein the apparatus is arranged to take action to control the solvent vapour concentration in the vessel to lie below 50% of the LEL maximum and wherein the apparatus is arranged to take action to control the solvent vapour concentration in the gas outlet stream to lie below 50% of the LEL maximum.
24. A method of increasing a solvent and/or volatile component content of a gas stream feed to an abatement plant, said method comprising feeding a solution and/or suspension an/or mixture to a vessel and promoting evaporation of solvent/volatile component from the solution/suspension/mixture and conveying solvent/volatile component vapour from the vessel into said gas stream feed. a)
25. A method of processing dirty solvent which comprises an ink solution and/or suspension and which dirty Q solvent is produced when parts of a print machine are () washed, said method comprising feeding the dirty (\,J solvent comprising the ink solution/suspension to a vessel and promoting evaporation of solvent from the solution/suspension and conveying solvent vapour from the vessel and separately conveying an ink solution/suspension having a reduced solvent content from the vessel for further processing.
26. A process plant comprising means for processing solutions wherein said plant comprises an apparatus and/or operates according to a method of any of claims 1 to 25.
27. A method or apparatus substantially as described herein with reference to any of the accompanying drawings.