Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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ACCESS VALVE DEVICES, THEIR USE IPd SEPARATION-APPARATUS,
AND CORRESPONDING METHODS
FIELD OF THE INVENTION
This specification relates to methods and apparatus
for_ the control of fluid flow, e.g in chromatography, i.e.
apparatus and methods for separating substances by passing
a mobile phase through a stationary or retained phase to
cause separation of mobile phase components.
BACKGROUND
Chromatography is a well-established and valuable
technique in both preparative and analytical work as well
as i.n purification generally. Typical industrial
chromatography apparatus has an upright housing in which a
bed of packing material, usually particulate, rests
against a permeable retaining layer. Fluid mobile phase
enters through an inlet e.g at the top of the column,
usually through a porous, perforated, mesh or other
restricted-permeability layer, moves through the packing
bed and is taken out at an outlet, typically below a
restricted-permeability layer.
Changing the bed of packing material, because it is
spent or in order to run a different process, is an
arduous task particularly with big industrial columns
which can be hundreds of litres in volume. The existing
bed has usually become compacted and difficult to remove.
2S The housing must be dismantled, the compacted packing mass
disrupted and then removed. Furthermore, the new bed must
be very evenly packed if the column is to be effective:
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the fresh material must be added carefully while maintain-
ing a flow of liquid. Usually the apparatus must be kept
clean, particularly with biological products where high
system sterility may be needed for weeks or even months.
One small contamination can be disastrous.
Conventionally, many hours have been needed to
change the spent packing in a big column.
GB-A-2258415 describes a column which can be
packed and unpacked without taking it apart, using special
supply and discharge valves in the top and bottom plates of
the housing. The packing supply valve has a spray nozzle
which can be retracted into the top plate, with the spray
openings closed by a seal on the plate, or advanced to
project into the column bed space, freeing the openings for
a slurry of packing material to be pumped in. The discharge
valve has an advanceable nozzle with radially-directed
spray openings at its enlarged head, positioned coaxially
within a wider bore of the bottom plate. When retracted
the head fits in the bore to seal itself and the bore. To
empty the column, the nozzle is advanced and buffer liquid
pumped through it. The advanced nozzle head breaks up the
packed medium and the pumped-in buffer carries it out
through the larger bore, now opened.
There are difficulties in maintaining long-term
sanitary conditions with these valve assemblies.
THE INVENTION
We now propose further developments.
According to the present invention, there is
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provided a chromatography apparatus comprising a column
housing with a housing wall defining an enclosed bed space
which in use contains a bed of packing material, and an
access valve installed in the housing wall through which
such packing material is packed into the bed space, said
access valve controlling first and second fluid flow
conduits which communicate into the bed space through it,
said conduits having respective exterior connections
outside the column housing and respective interior openings
which open into the bed space in an open condition of the
access valve;
the valve being adjustable to a closed condition
in which it isolates both the first and second conduits
from the bed space but puts the first and second conduits
into fluid communication with one another creating a
continuous cleaning path isolated from the bed space.
An access valve of this type offers a number of
possible operational advantages. Some are described later.
One feature it can offer is packing and unpacking a bed
space through a single housing wall installation. The
relevant processes may be as follows.
To unpack, the valve is moved to the third
condition in which both the first and second conduits are
open to the bed space. Fluid is forced in through the first
conduit to disrupt and disperse the packed bed, the
flowable dispersion of the packing material then flowing
out through the second conduit. Preferred features for
these purpose include the following.
The opening of the first conduit may have a spray
nozzle or other restriction, fixed or adjustable, to help
disrupt the bed by flow velocity. Having plural outlet
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openings also helps to reach a larger region of the bed
space and clear it more effectively.
According to another aspect of the present
invention, there is also provided a chromatography process
carried out in chromatography apparatus comprising a column
housing with a housing wall defining an enclosed bed space,
a valve communicating with the bed space through the
housing wall, and first and second fluid flow conduits each
having a respective exterior connection outside the column
housing and a respective interior opening to the bed space
through the valve;
said process comprising:
adjusting the valve to open the first conduit to
the bed space;
a packing step of supplying a dispersion of
packing material particles in a carrier liquid along said
first fluid flow conduit and into the bed space through the
valve, forming a bed of said packing material particles in
the bed space;
adjusting said valve to close off both the first
and second fluid flow conduits from the bed space and to
put the first and second fluid flow conduits into fluid
communication with one another in the valve to form a
continuous flow path isolated from the bed space, and
a cleaning step comprising passing fluid along
the continuous flow path formed by the first and second
fluid flow conduits.
The access valve device preferably comprises a
probe which, from a retracted condition recessed into the
housing wall, can be advanced into the bed space to disrupt
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material therein. The disrupting probe is preferably a
movable valve element defining one or both of the conduits,
preferably the first conduit at its outlet (which may be at
or through the head of the probe e.g. as in GB-A-2258415).
The opening of the second conduit may form an
outlet from the bed space. Desirably it is a single
aperture. Desirably it has cross-sectional area at least a
substantial proportion of the cross-sectional flow area
within the second conduit itself. Desirably the cross
sectional area of the second conduit through the valve
device is generally larger than that of the first conduit.
To pack, the access valve device can be adjusted
to
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the second, partially-open condition and packing material
forced in through the first conduit, typically as a
dispersion of particles in carrier fluid. Carrier fluid
escapes from the bed space through an outlet remote from
the valve device, while packing material is retained.
5 Thus, a bed of new packing material can be packed
against a permeable end retainer at a housing wall
location spaced from and preferably opposed to that of the
valve device, by maintaining a flow of carrier fluid
through the accumulating bed and out through the end
retainer. This flow of carrier fluid can accompany the
injection of bed material through the first conduit.
The valve device preferably has relatively movable
valve parts or elements which are movable in or into face-
to-face sealing contact with one another, and defining the
first and second conduits. A pair of such elements may be
sufficient to define the first and second conduits and
also sealing portions or lands sufficient for shutting off
their inward openings for the three conditions mentioned
above. Respective spaced sealing portions on one part or
element can sealingly engage a single sealing portion, or
plural differently-spaced sealing portions, on the other
relatively movable part or element to provide the first
and second conditions.
The relative movement between the valve elements
passing between the three conditions may be linear
(typically in the direction through the housing wall,
preferably perpendicularly), rotational (typically around
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a direction axis as specified above) or a combination of
these e.g. moved linearly by a screw thread action. The
three conditions desirably correspond to three spaced
stations along a predetermined single rotational, linear
or combination (e. g. helical) path or track for such
relative movement.
For simplicity one such valve element may have a
single sealing land which in the closed condition isolates
the first conduit from the bed space and in the partially-
open condition isolates the second conduit from the bed
space. This land may be on a said valve element fixed
relative to the housing wall, provided at or adjacent a
mouth of the valve device. The openings of the first and
second conduits can then be defined by one or more further
valve elements which is/are slidably moveable relative to
that sealing land.
Valves as proposed above are also usable to govern
flow into/out of any vessel or conduit; not only .'
separation apparatus housings.
It is a particularly desirable feature for a
component of a separator apparatus, and also in other
contexts, that it be cleanable in place ("CIP") i.e.
without removing it from the apparatus and most preferably
without interfering with the bed space e.g. while
separation is in progress.
In a further aspect we propose that this be
achievable, in an access valve device governing the
communication of first and second conduits through the
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housing wall of a separator apparatus bed space as
described, or through the well of any vessel or conduit
into a space, by arranging that in a closed condition of
the valve in which both first and second conduits are
isolated from the space a continuous cleaning path is
defined along the first conduit, through e.g. a cleaning
recess in the valve device connecting between the first
and second conduits, and along the second conduit. The
valve device components are shaped such that, for cleaning
fluid flow in at least one direction along the cleaning
path, all regions thereof are swept i.e. there are no dead
spaces. In particular, for at least one said flow
direction at no point in the valve device does the surface
of the first conduit, second conduit or the connecting
recess diverge from or converge towards the central flow
axis (or layer, according to the flow path shape) at a
right-angle or greater, and preferably not at an angle
greater than 70°.
One particular proposal provides the possibility of
such a flow path in a three-condition valve device as
proposed above, having relatively movable valve elements,
one of the elements having an isolating seal which seals
in the first condition against a first opposed sealing
surface of the other element and in the second condition
seals against a second opposed sealing surface of the
other element, isolating the first and second conduits
respectively from the bed space. According to our
proposal the one valve element defines a recess behind its
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isolating seal which, in the closed condition, provides
clearance around the second sealing surface of the other
element to put the first and second fluid conduits in
communication with one another.
In separation apparatus, a preferred location for an
access valve in any of the aspects described above is in
an end wall construction of the housing. This end wall is
typically fluid-permeable but impermeable to the relevant
packing material, e.g. by virtue of a porous, perforated
or mesh layer - a filter layer. The access valve openings
open to the bed space side of this layer. Generally
further openings are provided for introducing fluid
material, e.g. a sample or mobile phase generally, behind
that filter layer e.g. along a third conduit which extends
through the end wall alongside the valve device.
Another aspect provides uses of an access valve
device as described for removing material from a column
bed space, and in an additional version this may be part
of a separation process_
The additional version relates to a separation
process in which a liquid incorporating components to be
separated is caused to flow upwardly through a bed of
particulate stationary phase (packing medium) enclosed in
a bed space of a column housing, for example at a rate
which expands or fluidises the bed. After passing through
the bed the liquid passes a restricted-permeability
element (typically a mesh, or a porous or other perforated
layer which will retain the packing medium particles) and
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out of the column housing through a process outlet.
The liquid may incorporate particulate or cohesive
matter which will not pass, or not freely pass, the
restricted-permeability element. biological culture
products are an important example of this. For instance,
expanded bed separation is used to remove a target
protein, by adsorption onto the bed particles, from an
unclarified or partially-clarified culture broth
containing cells, cell debris, lipid particles and/or the
like.
As separation proceeds, such materials accumulate
against the restricted-permeability element used to
prevent escape of packing material through the process
outlet. In time, the accumulated matter prevents
effective operation. Processing must be stopped, the
column housing opened and the accumulated matter cleared
before restarting.
Our proposal is to remove such accumulated matter
from the bed space, e.g. from time to time as the process
proceeds, and optionally without cutting off the input of
feed stock liquid, by
opening a clearing outlet for accumulated matter at a
location at or adjacent the restricted-permeability
element and communicating directly with the bed space, and
forcing a clearing flow of fluid at, across and/or
back through the restricted-permeability element to
disturb the accumulated matter so that it passes out
through the clearing outlet.
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So, the separation process may continue with reduced
or eliminated interruptions for clearance of accumulated
matter from the bed space.
The clearing flow may be provided by forcing a
reverse flow through the restricted-permeability element,
5 e.g. back through the process outlet, or through other
conduits penetrating the impermeable wall behind the
restricted-permeability element. Additionally or
alternatively the clearing flow may come through one or
more nozzles on the bed space side of the element by
10 pumping fluid out of them e.g. at the centre of the
element, and desirably with a clearing flow radiating from
a conduit penetrating the housing wall.
These functions may be served by an access valve
device as disclosed in the previous aspects above.
Another proposal in the context of such a process
involves the introduction of a mobile phase into the
column bed space through a direct input opening, .'
preferably valve-governed, rather than through a
restricted-permeability element which is provided to
retain the inlet side of the packing bed. For example,
introduction is through an access valve device opening
through the restricted-permeability element.
In this way a mobile phase incorporating particulate
matter, or other matter which might clog the restricted-
permeability element, can be introduced conveniently into
the bed for processing. The access valve device used for
the introduction may be e.g. any as described above.
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Py combining this proposal with the previous one, the
introduced particulate or other matter can then
conveniently be cleared from the bed space.
A further aspect provided herein is a valve device
for governing flow through a housing or conduit wall into
a space, e.g for a chromatography column housing wall. The
valve device has an outer barrel element defining an axial
direction. The barrel has an internal bore extending
axially from an outer end to an inner end of the barrel,
with axially-directed openings at both ends. The opening
at the inner end constitutes a valve mouth, and provides a
radially-inwardly directed mouth sealing surface of the
bore. -
An elongate spool element extends axially through the
barrel bore and is axially movable relative to it. A
central fluid conduit extends axially through the spool
element, and opens adjacent the barrel mouth preferably by
plural radially-directed openings, preferably as a'spray
nozzle. The spool element has a first, inner radially-
outwardly directed sealing land disposed axially inwardly
of the central conduit opening and adapted to seal against
the barrel s mouth sealing surface in a first relative
longitudinal position of the spool element relative to the
barrel, thereby isolating the central conduit opening from
the valve mouth.
2~ The spool element also has a second, outer radially-
outwardly directed sealing land disposed axially outwardly
of the central conduit opening and adapted to seal against
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the barrel's mouth sealing surface in a second,
intermediate longitudinal position of the spool element
relative to the barrel in which the central conduit
opening is exposed to the interior space. Outwardly of
the second sealing land is a spacing, preferably annular,
between the spool element and the barrel bore_ This
spacing constitutes an outer axially-extending fluid
conduit which in a second, intermediate position is
isolated from the valve mouth by the sealing of the second
land.
In a third, inward position of the spool element
relative to the barrel the second sealing land is clear of
the mouth sealing surface and both the inner and outer
conduits are open to the interior.
This valve device is suitable for use in all of the
above aspects.
The barrel bore may have a recess disposed outwardly
of the mouth sealing surface and connecting the inkier
conduit opening to the outer conduit in the fully-closed
position.
The valve may be installed in the wall with the valve
mouth at the wall interior and at the wall exterior a
connecting manifold providing a fixed communicating
connection to the outer conduit at the outer end of the
barrel and a movable communicating connection to the inner
conduit of the spool element. Means for driving
controllable movement of the spool element is also
provided. This may take various forms which a skilled
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person can provide without difficulty. For example, as
disclosed in GB-A-2258415 the spool element may be thread-
mounted into the manifold or another fixed component, the
drive means functioning to rotate it to a controlled
extent to give the desired axial shift.
In separation apparatus the valve may be installed in
an end wall having an inner restricted-permeability layer
and an outer impermeable wall layer, the valve mouth
communicating through the restricted-permeability layer.
The outside of the barrel at the mouth may overlap the
restricted-permeability layer to trap it. To introduce
process fluids into the bed space, one or more process
conduits lead through the impermeable wall layer to behind
the restricted-permeability layer, e.g. alongside the
valve barrel as one or more clearances between the valve
IS barrel and the surrounding impermeable layer of the end
wall.
BRIEF DESCRIPTION OF THE DRAWINGS .'
Embodiments of our proposal are now described in
detail, with reference to the accompanying drawings in
which
Figure 1 is a cross-sectional schematic side view of
a chromatography column showing the basic features
thereof;
Figure 2 is an axial cross-section showing an end
plate construction in more detail;
Figure 3 shows enlarged, in axial cross-section, the
construction of an access valve;
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Figure 4 is an axial cross-section corresponding to
Fig. 2 with the access valve in a part-open position;
Figure S is an axial cross-section corresponding to
Fig. 2 but with the access valve in a fully-open position;
Figure 6 is an axial cross-section of the end plate
illustrating a medium packing operation;
Figure 7 is a view corresponding to Fig. 6, with the
column in operation and the access valve being cleaned;
Figure 8 is an axial cross-section corresponding to
Fig. 6 illustrating the process of unpacking a packing
medium from the column;
Figure 9 is an axial cross-section of the top end
plate of a chromatography column undergoing expanded-bed
chromatography, illustrating a clearing operation;
Figure 10 is an axial cross-section of a column end
which is a variant of that in Figs 2 to 8; and
Figure 11 is a schematic view of a second version of
the access valve.
DETAILED DESCRIPTION OF EMBODIMENTS
Figure 1 shows schematically the general components
of a chromatography column The column has a
cylindrical fluid-impermeable side wall 11, e.g. of
stainless steel or a high-strength/reinforced polymeric
material which may be translucent. The open top and
bottom ends of the side wall 11 are closed by top and
bottom end assemblies 12,13. Each end assembly has a
fluid-impermeable end plate 3 fitting sealingly to plug
th2 opening of the cylindrical wall 11, and preferably of
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stainless steel or high-strength engineering plastics
material, e.g polypropylene. The end plates are backed up
by metal retaining plates 2 bearing against their outer
surfaces and projecting radially beyond the side wall as
retaining flanges 22 through which adjustable tension rods
5 14 are secured_ These link the top and end assemblies
12,13 and help the construction to withstand high fluid
pressures.
Each end plate 3 has a central through-opening 31 for
communication between the exterior of the column and the
10 packing bed space 9 defined by the side wall 11 and end
assemblies 12, 13. Access through the opening 31 is sub-
divided into separate conduits, connected externally
through a connection manifold 8_
A filter layer 4, typically of filtered or woven
IS plastics or steel, extends across the area of the bed
space 9 at the inner surface of the end plate 3. The
inner surface 35 of the end plate 3 is recessed behind the
filter layer 4, e.g. conically as illustrated, and
preferably with the use of support ribs (not indicated)
supporting the filter layer 4 from behind, to define
between them a filtration space 34. One of the
conununication conduits, a mobile phase conduit 33, opens
inwardly into this filtration space 34, as well as
outwardly to a mobile phase connector 81 of the manifold
8.
Frorn the manifold 8, an access valve device 5
projects inwardly through the end plate opening 31 and
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sealingly through a central orifice 41 of the filter layer
4. The access valve 5, embodiments of which are described
in more detail below, governs the communication of one or
more conduits from the manifold 8 directly to the bed
space 9, i.e. bypassing the filter layer 4. Indicated
S here are first and second valued conduits 51, 61 governed
by the valve 5, and connected externally through
connectors 82 of the manifold 8.
In a typical operation of the column, a packed bed of
particulate stationary phase material fills the bed space
9 between the top and bottom filter layers 4. The valve
devices 5 being closed, a mobile phase is fed in through
mobile phase connector 81 (arrow ~~A"), passes through
conduit 33 into the filtration space 34 and through the
filter layer 4 to elute down through the packed bed,
effecting separation of its components. Liquid eluate
passes thought the filter layer 4 of the bottom end
assembly 13 and out through the mobile phase connector 81
thereof (arrow "B") for collection as appropriate.
Figure 1 and the above explanation are to illustrate
general relationships of components and a typical mode of
operation. The skilled person knows, and it will also
appear from the following description, that other specific
constructions and modes of operation may be appropriate
for different kinds of process.
A more detailed embodiment of an end plate and valve
construction is now described with reference to Figures 2
and 3.
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A manifold 8 is provided as a machined metal or
plastics block fixed sealingly over the central opening 31
of the end plate 3 by threaded connectors 88, and recessed
into a central aperture 23 of an outer metal retaining
plate 2 which is fixed to the end plate 3 by bolts 21 or '
other suitable fasteners. The periphery of the end plate
3 seals against the column side wall 11 with an annular
polymeric seal member 32 which also overlaps the filter
layer 4 to retain its periphery. This seal member may
have an internal rigid reinforcement. Unlike a
conventional O-ring it eliminates dead space by sealing
with a cylindrical surface and mounting in a shape-fitting
groove of the end plate.
The manifold 8 has a central bore 91 coaxial with the
plate opening 31 and having inwardly and outwardly
l5 directed threaded connection openings 83, 89. The
cylindrical barrel 6 of a spool valve 5 is screwed into
the inward connection 83, to extend coaxially inwardly
through the central plate opening 31 and out through a
central circular orifice 41 of the filter layer 4,
terminating in an outward flange 65 which overlaps the
filter layer 4. A cylindrical outer sleeve 66 fits snugly
around the barrel 6, its outward edge resting against the
inward face of the manifold block through a polymeric
sealing ring 662 and its inner edge resting against the
2_5 outer surface of the filter layer 4 through another
polymeric sealing ring 661, trapping the layer 4 between
the sleeve 66 and barrel flange 65. Since the barrel's
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outer diameter corresponds to that of the layer orifice
41, it is possible in the illustrated condition to remove
the barrel by unscrewing it and withdrawing it inwardly,
without disturbing the filter layer 4. This is an
advantage for column maintenance.
S One or more flow conduits 33 are created by clearance
between the barrel assembly (barrel and sleeve) and the
plate opening 31. Thus, the plate opening 31 may have a
plurality of axially-extending channels distributed around
it to form the conduits 33, intervening surfaces of the
opening 31 fitting against the barrel assembly. Or, a
full annular clearance may be provided. Or, these
conduits may be provided away from the barrel assembly,
defined only through the material of the plate 3. The
inner ends of the conduits 33 communicate into the
filtration space 34. Their outer ends align sealingly (by
virtue of polymeric sealing rings 662,663) with connection
conduits 811 of the manifold block, connected in common to
a threaded or otherwise connectable port 81. This
establishes direct fluid communication between filtration
space 34 and the port 81, while communication between the
bed space 9 and port 81 is necessarily through the filter
layer 4. Ribs provided on the inner plate surface 35 (in
known manner) assist even distribution or collection of
fluid to or from the space 34.
A bore 61 extends axially through the barrel 6 from
one end to the other. The bore's outward end merges
sealingly (by polymeric sealing ring 664) and without
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change of diameter into the central manifold bore 91. The
inward end of the bore 6 is on the bed space side of the
filter layer 4, and constitutes a mouth opening 611. The
bore 61 has a uniform cylindrical cross-section except for
a radially-enlarged portion near but outward of the mouth
611. The enlarged portion 612 has a central cylindrical
part bordered on either side by tapering surfaces 613.
These are angled at not more than 45° from axial.
A central probe element acts in the bore 61, to
give the function of a spool valve. The probe element
has an elongate tube 72 with an open internal bore 73.
extending axially from adjacent the barrel mouth 611 out
through the outward end of the barrel 6 and the coaxial
ball 91 of the manifold 8. Outwardly of the outer barrel
end, a tapered sealing ring 665 seals between the tube 72
and surrounding manifold bore 91: a plug collar 87 is
screwed into the outer connection 89 of the manifold to
hold the tapered seal 665 effectively in place.
At its inward end, the probe has a solid head 71
with a pointed tip 74, terminating the bore 73. The head
71 has a cylindrical sealing surface 711, of the same
diameter as the barrel bore 61, and which as shown can
seal against an inward sealing surface 64 at the mouth 611
of the barrel bore 61, assisted by a flush-recessed
polymeric sealing ring 641.
The probe bore 73 opens at a set (Fig. 4) of spray
openings 75 opening through and distributed
circumferentially around the tube 72. The tip sealing
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surface 711 stands radially proud of these openings 75.
Immediately outwardly of the openings the probe head 71
has another radially-enlarged portion or land 76 which
presents a cylindrical sealing surface 761 bordered by
tapering portions 762 angled at not more than 45" from the
5 axial.
Outwardly of this second enlargement 76 the tube
exterior 72 is a plain cylinder.
The diameter of the sealing surface 761 on the second
enlargement 76 is the same as that 711 on the first
10 enlargement 71.
The tube 72 being narrower than the barrel ball 61,
an annular-section clearance 51 is defined between them.
This constitutes an outer valve conduit extending out
through the outer end of the barrel 6 into the manifold
15 bore 91 up to the seal 665, where it diverts to a threaded
or otherwise connectable manifold port 82.
Beyond the manifold 8, the outer end of the probe
tube 72 is connected to means for advancing or retracting
it axially relative to the barrel 6, with sliding through
20 the seal 665. These means may be motor or servo
activated, e.g. advancing the probe by rotating a fixed
drive member which engages the tube 72 via a screw thread,
e.g. as proposed in GB-A-2258415. Additionally or
alternatively, a manual control is provided for the axial
adjustment.
The spool valve effect of the valve 5 is as follows.
Figs 2 and 3 show a first, closed condition in which
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the head sealing land 711 seals with the mouth sealing
surface 64 of the barrel, isolating both the valve
conduits 51, 73 from the bed space 9. The filtration
conduits 33 are not affected by the valve. The nozzle
openings 75 and the second sealing land 76 register
axially with the radially-enlarged portion 612 of the
barrel bore 61. This puts the nozzle openings 75 into
communication with the outer valve conduit 51, creating a
continuous sealingly-enclosed flow path between the probe
tube bore 73 and the manifold port 82. This path has no
unswept areas or dead spaces. within the valve device 5,
none of its boundary surfaces deviates from the local
central flow axis/layer by more than 45°, assisting
effective sweeping. In the manifold the path likewise has
no dead ends.
l5 Consequently, when the chromatography column is
running (see also Fig. 7) the valve device and its
associated connections can be cleaned in place by.feeding
a cleaning solution (e. g. aqueous alkali, or other
suitable cleaning medium known to the art) through that
fully-sweepable cleaning path. It is particularly
envisaged to feed the cleaning solution in through the
probe tube 72.
Figure 4 illustrates a second, partially-open
condition of the valve 5. The probe tube 72 is advanced
sufficiently to bring the second sealing land 76 into
register with the bore mouth 611, where their respective
sealing surfaces 761, 64 effect a sliding seal. This also
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brings the nozzle openings 75 to outside the mouth 611,
conanunicating with the bed space 9. Accordingly the inner
valve conduit constituted by the bore 73 is put into
direct communication with the bed space, bypassing the
filter layer 4, while the outer valve conduit 51 remains
isolated from the bed space 9.
Figure 6 illustrates an application of this in
creating a new bed of packing material. The packing
itself can be as described in GB-A-2258415. Specifically
a flowable flurry of packing material particles in carrier
liquid is pumped in through the tube 72 and sprays out
radially in circumferentially-distributed directions from
the openings 75. As packing material accumulates in the
bed space 9 excess carrier fluid escapes through the
filter layer 4 and away through the filtration conduits 33
and manifold port 81, to which a connecting tube is
fastened. This is continued until sufficient packing
material has been introduced. .'
Figure 5 illustrates a third condition of the valve.
Here the probe tube 72 has been advanced further inwardly
to bring the second sealing land 76 clear of the mouth
seal 64, which now opposes the smaller-diameter outer
surface of the tube 72 to create a clearance, opening the
outer valve conduit 51 to the bed space 9 through the
mouth 611.
Figure 8 shows how to exploit this third condition to
unpack material from a column bed. It should be noted
that, as disclosed in GB-A-2258415, the advanced pointed
CA 02305039 2000-OS-O1
23
head 71 of the probe is apt to disrupt existing bed
material, which is often a hard compacted mass, and
thereby help to initiate unpacking. A carrier liquid such
as a buffer is pumped in through the probe bore 73 and out
through the nozzle openings 75; its high nozzle velocity
helps to disrupt and entrain the packed material. The
particulate packing material cannot pass the filter layer
4, but it can respond to the pumping in of liquid by
escaping as a slurry through the mouth 611 of the valve
and along the outer valve conduit 51 to the manifold port
82 for discharge along a connected tube.
So, for the first time a single column wall
installation enables both packing and unpacking of a
column. This can give much greater flexibility in column
operation. Note that the packing and unpacking operations
can be effected entirely from outside the column housing,
without needing to dismantle or remove the end assemblies.
Furthermore the valve which can do this can itself~be
cleaned in place, even when the column is running by
introducing a mobile phase onto the bed through the
filtration conduits 33 as shown in Fig. 7. So, even this
relatively sophisticated wall installation does not
introduce a risk of contaminants accumulating and
leaching into a long-running process perhaps with
disastrous results. In the terminology of the skilled
person in this field, this valve device is a "sanitary"
installation.
Furthermore the valve is easily dismantled for
CA 02305039 2000-OS-O1
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24
maintenance because the probe can be entirely withdrawn
inwardly from the barrel bore 61.
Further modes of use, in relation to expanded-bed
separation processes, are explained with reference to
Figs. 9 and 10. Expanded bed adsorption is a recently-
developed separation technique, particularly for reducing
or eliminating the need to clarify biological cultures
before eluting them through a packing to separate out a
desired component. The packing bed is expanded by an
upflow of liquid medium so that even particulate material
l0 in the sample can work its way through the bed to the
outlet above the bed. For expansion the bed must rest on
a permeable layer through which the liquid up-flow is
established. Introduction of the sample must therefore
generally be done as a single pass, which sample batch
then elutes through the bed. Usually desired materials
are adsorbed onto the bed particles, and in a subsequent
step are recovered by stopping the liquid up-flowr
compressing the bed by moving down the upper plate and
then percolating through the bed a liquid that desorbs the
target substance from the bed particles.
A column for this can have top and bottom retaining
assemblies which each have an impermeable plate interior
filter layer and a central valve device as shown in the
previous Figures. The normal filtration conduits and
means for establishing up-flow of a mobile phase are also
provided.
A first feature here is that a sample e.g.
CA 02305039 2000-OS-O1
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unclarified broth, can conveniently be introduced into the
expanded bed, bypassing the lower filter mesh, by
injecting it though the inner valve conduit 73 of_ the
lower valve in its second, partially open condition.
where sample is injected intermittently the lower valve is
5 returned to its fully-closed first condition in between.
Our new valve construction therefore provides a convenient
way of introducing such a sample past a mesh required for
maintaining an up-flow.
A second and very significant feature is explained in
l0 relation to Fig. 9, which shows in more detail a top end
assembly for the expanded-bed process.
During normal running of the process the mobile phase
passes through the filter layer 4~, through the filtration
conduits 33' and out. There is a gradual accumulation of
15 particulate debris and other matter reluctant to pass the
filter 4', e.g. lipids. This therefore accumulates in an
upper bed space region 91 adjacent to filter layer 4~. In
time it hinders the maintenance of proper flow.
By moving the upper valve device 5' to its third,
20 fully-open condition for a short period of time, while
creating a clearing flow of liquid adjacent the filter
layer 4~ to disturb the accumulated matter, this matter
can be caused to follow the clearing flow out of the bed
space via the outer valve conduit 51. One method of
25 achieving a clearing flow is to provide a short blast of
suitable liquid, e.g. a buffer, through the probe bore 73'
and out through the nozzle openings 75' which are near the
n...
CA 02305039 2000-OS-O1
2G
filter layer 4'. Alternatively or additionally, the
normal flow direction (arrow "Y,") of buffer out of the
system can temporarily be reversed and buffer pumped back
in through the filtration conduits 33' (arrow "Y"),
thereby creating a temporarily downward flow through the
filter layer 4' (arrow "Z"), disrupting the accumulated
material so that it can accompany the escape of the
temporary liquid pressure wave out through the valve
conduit 51. This may be done either with or without cut-
off of the supply of sample at the bottom of the column.
Thus, the process can be run as long as the
absorption proceeds efficiently, without needing to stop
for other reasons. This is a highly advantageous
procedure.
Fig 10 shows a variant end plate construction for a
chromatography column. The differences from the previous
embodiment include the following.
The filter layer 4 is formed integrally with.inner
and outer annuli 41,42, in one piece in plastics material.
The inner annulus 41 forms a flush termination for the
barrel 6 of the central valve 5, and has an inwardly-
facing surface to form the seal with the valve's central
probe. This flush one-piece construction further reduces
the risk of contamination at the point of access. It also
enables the filter layer's inner periphery to self-trap in
2~ a groove of the valve barrel 6, enabling that barrel 6 to
be one component rather than two. The end cell and valve
components may be of polypropylene.
CA 02305039 2000-OS-O1
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77
The filter layer's outer annulus 42 is used to hold
the filter layer in place by trapping between the wall 11
of the column and the end plate 3 of the cell, which in
this version is a one-piece polypropylene construction.
The connection manifold 8 has the mobile phase
inlet/outlet port 81 and the waste slurry outlet port 82
inclined outwardly, rather than perpendicularly as in the
previous embodiment, to improve flow. A further
significant feature in this embodiment is that the filter
layer 4 is concave, by virtue of the support ribs on the
end plate 3 being formed with inclined rather than
slightly radial edges. we find that this slight conicity
improves drainage from the column during clearing.
Fig 11 shows schematically a different embodiment
valve which however embodies similar concepts. Here the
l5 central movable probe is a simple armature rather than a
fluid-carrying nozzle. Its enlarged head 171 is carried
on actuating rod 272 and has a flat end surface 1712, a
first outer sealing land 1711, a conical convergence 1613
to a narrow recess or waist 1612, and a smaller
enlargement 176 with a second sealing surface 1761.
The mobile phase conduit 33 is provide outside the
valve barrel 6 as before. Inside the valve barrel the
central fluid conduit 173 is defined not through the probe
272,171 but rather by an inner conduit wall 172
surrounding the probe shaft 272 and having an opening with
an inwardly-directed seal 174, recessed back from the main
opening through the filter layer 4, which has its own
CA 02305039 2000-OS-O1
28
inwardly-directed seal 141 at the mouth of the outer
conduit defined between the outer barrel wall 6 and the
inner conduit wall 172.
Fig 11 shows the valve fully open, with the central
probe fully advanced to open both conduits e.g for
unpacking and column. Unpacking liquid is pumped in
through the inner conduit 173 and squirts out around the
armature head 171; waste slurry flows back and out through
the outer conduit.
In the partially open position, e.g for packing a
column, the armature is partially retracted so that second
sealing surface 1761 seals off the inner conduit, the
outer conduit remaining open. Slurry can be pumped in
through the outer conduit. This shears the slurry less
than the spray nozzle of the first embodiment.
Full retraction of the armature brings its front
surface 1712 flush with the filter layer 4 and its first
head sealing surface 1711 into sealing engagement~with the
central filter opening seal 141, closing off the outer
conduit. At the same time the second sealing land 176
drops below the inner conduit seal 174 which then opposes
the recess 1612 to permit a circulating, clean-in-place
flow through the inner and outer conduits.
Note that in the open conditions the conical portion
1613 of the head 171 can be axially adjusted to alter the
direction of liquid pumped in. This embodiment
illustrates how two separate seals on the fixed part of
the valve can provide the same effect as previously if
' CA 02305039 2000-OS-O1
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29
their spacing is different from that of the corresponding
sealing portions of the movable part.
