Liquid purification or separation – Serially connected distinct treating with or without storage... – Diverse
Reexamination Certificate
2000-12-18
2003-07-08
Drodge, Joseph (Department: 1723)
Liquid purification or separation
Serially connected distinct treating with or without storage...
Diverse
C202S168000, C210S179000, C210S180000, C210S182000, C210S511000, C210S634000, C210S195100, C422S258000, C554S008000, C554S012000
Reexamination Certificate
active
06589422
ABSTRACT:
This invention concerns apparatuses and a method for “extraction” of biomass. This is the extraction of flavours, fragrances or pharmaceutically active ingredients from materials of natural origin (these materials being referred to as “biomass” herein).
Examples of biomass materials include but are not limited to flavoursome or aromatic substances such as coriander, cloves, star anise, coffee, orange juice, fennel seeds, cumin, ginger and other kinds of bark, leaves, flowers, fruit, roots, rhizomes and seeds. Biomass may also be extracted in the form of biologically active substances such as pesticides and pharmaceutically active substances or precursors thereto, obtainable e.g. from plant material, a cell culture or a fermentation broth.
There is growing technical and commercial interest in using near-critical solvents in such extraction processes. Examples of such solvents include liquefied carbon dioxide or, of particular interest, a family of chlorine-free solvents based on organic hydrofluorocarbon (“HFC”) species.
By the term “hydrofluorocarbon” we are referring to materials which contain carbon, hydrogen and fluorine atoms only and which are thus chlorine-free.
Preferred hydrofluorocarbons are the hydrofluoroalkanes and particularly the C
1-4
hydrofluoroalkanes. Suitable examples of C
1-4
hydrofluoroalkanes which may be used as solvents include, inter alia, trifluoromethane (R-23), fluoromethane (R-41), difluoromethane (R-32), pentafluoroethane (R-125), 1,1,1-trifluoroethane (R-143a), 1,1,2,2-tetrafluoroethane (R-134), 1,1,1,2-tetrafluoroethane (R-134a), 1,1-difluoroethane (R-152a), 1,1,1,2,3,3-hexafluoropropane (R-236ca), 1,1,1,2,2,3-hexafluoropropane (R-236cb), 1,1,1,3,3,3-hexafluoropropane (R-236fa), 1,1,1,3,3-pentafluoropropane (R-245fa), 1,1,2,2,3-pentafluoropropane (R-245ca), 1,1,1,2,3-pentafluoropropane (R-245cb), 1,1,2,3,3-pentafluoropropane (R-245ea) and 1,1,1,3,3-pentafluorobutane (R-365mfc). Mixtures of two or more hydrofluorocarbons may be used if desired.
An especially preferred hydrofluorocarbon for use in the present invention is 1,1,1,2-tetrafluoroethane (R-134a).
It is possible to carry out biomass extraction using other solvents, such as chlorofluorocarbon (“CFC's”) or hydrochlorofluorocarbons (“HCFC's”) and/or mixtures of solvents.
Known extraction processes using these solvents are normally carried out in closed-loop extraction equipment. A typical example 10 of such a system is shown schematically in FIG.
1
.
In this typical system, liquefied solvent is allowed to percolate by gravity in downflow through a bed of biomass held in vessel
11
. Thence it flows to evaporator
12
where the volatile solvent vapour is vaporised by heat exchange with a hot fluid. The vapour from evaporator
12
is then compressed by compressor
13
: the compressed vapour is next fed to a condenser
14
where it is liquefied by heat exchange with a cold fluid. The liquefied solvent is then optionally collected in intermediate storage vessel (receiver)
15
or returned directly to the extraction vessel
1
to complete the circuit.
There are particular problems when the biomass is a liquid (typically aqueous) form. Examples of liquid biomasses include, but are not limited to, coffee and orange juice. Liquids containing solid biomass particles present similar difficulties. We refer to such biomasses herein as “liquid entrained” biomasses.
Hydrofluorocarbon (HFC) solvents have been found to be effective in extracting such biomasses. An example of a suitable HFC solvent is 1,1,1,2-tetrafluoroethane, sold as “R-134a” by the KLEA division of Imperial Chemical Industries plc. It would be desirable to provide an apparatus and method capable of continuous extraction of liquid or liquid entrained biomass using e.g. 1,1,1,2-tetrafluoroethane in liquid form.
According to a first aspect of the invention there is provided apparatus for extracting biomass from a liquid biomass supply. The apparatus comprises a hollow vessel containing a liquid, liquid or liquid-entrained biomass being supplied at or near a first side of the vessel and a liquid solvent being supplied at or near a second, opposite side of the vessel such that a stream of solvent passes in one direction through the vessel and a stream of biomass passes as a countercurrent through the vessel, so that biomass extract becomes entrained with the solvent. An outlet for biomass is at or near the second side of the vessel, and an outlet for solvent/extract mixture is at or near the first side of the vessel. A separator is connected to the solvent/extract outlet for separating solvent and extract from one another.
This apparatus advantageously allows intimate mingling of the biomass and the solvent so that the solvent efficiently strips the desirable components from the biomass and entrains them to a further location for separation of the solvent and biomass from one another.
The use of countercurrent flows makes the apparatus suitable for the continuous processing of liquid or liquid-entrained biomass. Conveniently in the apparatus the separator includes a rectifier for rectifying the solvent and separating therefrom the extract, a compressor, and a condenser connected in series, whereby the separator generates substantially uncontaminated solvent in liquid form. These features advantageously separate the desired biomass extract from the solvent whereby the extract is available for further use.
In the apparatus the separator includes a rectifier for rectifying the solvent and separating therefrom the extract, a compressor, and a condenser connected in series, whereby the separator generates substantially uncontaminated solvent in liquid form. The apparatus also includes pipework for supplying at least some of the substantially uncontaminated solvent from the condenser to the hollow vessel in a substantially closed loop circuit that includes the said vessel. This advantageously allows recycling of recovered solvent for contact with further biomass.
In preferred embodiments the separator includes a rectifier for rectifying the solvent and separating therefrom the extract, a compressor, and a condenser connected in series, whereby the separator generates substantially uncontaminated solvent in liquid and wherein the condenser includes first and second condenser ages connected in series, the second condenser stage operating at a lower temperature than the first stage and both condenser stages supplying substantially uncontaminated solvent to the hollow vessel. This is because there are sometimes residual inerts (air, carbon, dioxide, etc) in the aqueous feed stream of biomass. The solvent entrains some of these inert compounds to the condenser. Condensation in the presence of inerts is sometimes difficult. The second condenser stage advantageously separates inerts from the solvent.
The second condenser stage preferably operates at a lower temperature than the first stage. This removes heat from the solvent/inert compound mixture.
Even using a two-stage condenser, some uncondensed vapours may remain. Therefore the second condenser stage advantageously includes a vent for venting uncondensed vapours therefrom.
Preferably the vent is connected to an adsorbent filter that adsorbs solvent in the vented vapour. This advantageously recovers yet more of the solvent.
An example of a suitable adsorbent filter is a bed of activated carbon.
The separator as earlier defined may advantageously have a rectifier (still) for rectifying the solvent and separating therefrom the extract, a compressor, and a condenser connected in series. The separator generates substantially uncontaminated solvent in liquid form and the rectifier includes a still connected to the solvent/extract outlet of the hollow vessel. This still includes a heater for heating any solvent/extract mixture therein to a higher temperature than the solvent dewpoint. An outlet for solvent in vapour form is connected to supply such solvent to the suction side of the compressor, and a drain is provided for extract in liquid form.
Conveniently the still includes a vent and a refl
Cook Alex McFarron Manzo Cummings & Mehler, Ltd.
Drodge Joseph
Ineos Fluor Holdings Limited
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