Note: Descriptions are shown in the official language in which they were submitted.
CA 02856253 2014-07-08
A SPARGER SYSTEM
FIELD OF THE INVENTION
This invention pertains to the field of fluid processing systems, which
benefit from the
inclusion of a fluid delivery system and more particularly to a flexible
sparger sytem built
in and made of the same flexible material that contains the sparger system.
BACKGROUND TO THE INVENTION
The current energy crisis has prompted interest in alternative energy,
bringing a great
deal of attention to the production of algae biofuels. Beyond biofuels,
commercial algae
farming is also important to medicine, food, chemicals, aquaculture and
production of
feedstocks. One major obstacle to the production of biofuels is the commercial
scale-up
for mass culture, temperature control of algae and the high cost associated
with such a
culture.
The vast number of bioreactor concepts is testimony that the best algal
farming
bioreactors are still to be found. Most bioreactor designs are not suitable
for commercial
use due to cost and scale-up problems. In contrast with bioreactors, pond
technologies
are commercially viable today, but have well-established problems of their
own.
Integrated technologies might provide the control offered through closed
bioreactors and
the scalability afforded by open ponds.
To appreciate the value of attempts made and of associated prior art, a short
review of
recent studies and related publications is presented:
Dimanshteyn taught in US Pat. 7,824,904 that photobioreactors generally
consist of a
container containing a liquid growth medium that is exposed to a light source.
However,
the configuration of the photobioreactor often prevents the light from
penetrating more
than a few centimeters from the surface of the liquid. This problem reduces
the
efficiency of the photobioreactor, and was recognized in "Solar Lightning for
Growth of
Algae in a Photobioreactor" published by the Oak Ridge National Lab and Ohio
CA 02856253 2014-07-08
University. Light delivery and distribution is the principle obstacle to using
commercial-
scale photobioreactors for algae production. In horizontal cultivator systems,
light
penetrates the suspension only to 5 cm leaving most of the algae in darkness.
As described in Healthy Algae, Fraunhofer Magazine, January 2002, algae are a
very
undemanding life form-they only need water, 002, nutrients and sunlight.
However,
providing sufficient sunlight can be a problem in large scale facilities. As
the algae at the
surface absorb the light, it does not penetrate to a depth of more than a few
millimeters.
The organism inside the unit gets no light and cannot grow, explains Walter
Troesch,
who has been cultivating algae for years. One of the problems with growing
algae in any
kind of pond is that only in the top 1/4 inch or so of the pond receives
sufficient solar
radiation for the algae to grow. In effect, this means that the ability of a
pond to grow
algae is limited by its surface area, not by its volume.
In summary, the ability of a pond to grow algae is limited by its surface
area, not by its
volume. Therefore limitations in prior documents are examined in consideration
of the
above findings.
Traditional procedures employed for culturing autotrophic organisms have
involved the
use of shallow open ponds or open channels exposed to sunlight. Not
surprisingly this
comparatively crude method has proved impracticable for production of pure
high grade
products because of such problems as invasion by hostile species (sometimes
producing dangerous toxins), other pollution (such as dust), difficulty in the
control of
such variables as nutrient ratios, temperature and pH, intrinsically low yield
because of
escape of carbon dioxide to the atmosphere and inefficient use of light to
illuminate only
the top portion of the biomass.
Somewhat more sophisticated attempts have involved the use of horizontally
disposed
large diameter transparent plastics tubes for biomass production. The problems
of such
a system include the low density of biomass in the liquid within the tubes,
coating of the
pipes by algae due to low velocity flow passing through, thus reducing
transparency,
overheating in summer weather, high land usage and high energy input to
displace large
amount of over diluted water.
CA 02856253 2014-07-08
Now, looking closely at receptacles disclosed in prior documents and more
particularly
for potential use as low-cost raceway-type pond or photo bioreactor, a number
of
inventions are examined.
US 7,069,875 to Warecki ("Warecki") discloses a large and low cost portable
raceway or
vessel for holding flowable materials. The vessel has a body formed of an
elongate
rollable sheet of buoyant material that, when assembled into an upwardly
concave
vessel has bulkheads at its ends to give it its half-rounded shape. The large
vessel is
self-supporting in both water and land. The Warecki vessel suffers from a
number of
limitations. Joining of parts such as bulkheads to the body of the vessel
requires
welding, chemical bonding, and-or mechanical fastening. Also, to maintain the
shape of
the pond, bulkhead bow frames must be positioned inside the vessel, dividing
the space
into closed compartments that are fastened mechanically or chemically to the
body,
although some unsecured movable compartments are used. Also, no provision of
thermal control is provided.
US 5,846,816 to Forth ("Forth") discloses a biomass production apparatus
including a
transparent chamber which has an inverted, triangular cross-section. Although
tlie
"Forth" bioreactor promotes the growth of biological matter, it contradicts
the principles
extensively tested by Tredici, Fraunhofer and National Labs that assert the
need to
maximize exposed surface area to sunlight relative to the volume displaced.
Furthermore, the disclosed chamber is expensive to manufacture. Finally, the
constant
circulation of the liquid required by "Forth" interferes with the growth of
some types of
biological matter. For instance, fully differentiated aquatic plants from the
lemnaceae or
"duckweed" family are fresh-water plants that grow best on the surface of the
water.
Such surface growing plants typically prefer relatively still water to support
and promote
optimal growth.
Often, the importance of the surface area directly exposed to sunlight and
which can
benefit from the photosynthesis process has been overlooked in prior art.
Consequently,
many inventions have paid more attention to the volume of water and of the
over diluted
algal suspension being displaced than the actual available amount of photon
per square
meter available to that algal solution. This resulting low-efficiencies have
lead to the
CA 02856253 2014-07-08
necessity of oversizing algae farming facilities and consequently to high
costs in
investment, operations and energy.
PCT/CA2012/050750 to the undersigned Mottahedeh describes a gas sparger tube
made of the same material as a sleeve which is inserted into a semi-rigid
bioreactor by
tucking a small part of the sleeve into it's own edge, thus forming a sparger
tube at the
same time as the sleeve is being shaped. Similar to the shaping of a gusseted
tubing,
which has a triangular shaped pleat on one side of a layflat tube, there is
provided a lay
flat tube or sleeve that includes a triangular shaped pleat first punched with
pin holes
and then, having the base of the triangle sealed so as to create an internal
gas sparger
tube within the sleeve. This arrangement is shown in Figure 1 herein (same as
Figure 6
in PCT/CA2012/050750). In this sparger tube, gas exits in a single forward
direction
causing shear and a dead zone around its root.
Abandoned before its publication, CA2801768 to Mottahedeh taught a
photobioreactor
bag with built-in sparger tube, agitator and water jacket. Teachings of the
apparatus and
methods are transferred to the present application without prior disclosure.
SUMMARY OF THE INVENTION
The invention teaches a sparger system for use within fluid processing systems
and
more particularly to systems where delivery of a fluid medium (gas or liquid)
within a
containment system is beneficial to mixing of fluids such as chemicals or
growth of
biological organisms. Traditionally, sparger tubes are made of rigid or semi-
rigid
materials such as sponge stones, ceramics, plastics, rubber and porous metal
pipes.
Sparger tubes made of lighter materials tend to float and defeat the very
purpose of
sparging. Insertion of external sparger tubes into a processing system often
introduces
contamination, requires peripheral accessories to keep them in place or
demands
specialized cleaning when contaminated. Often, traditional spargers produce
localized
mixing and unwanted shear forces due to the high pressure is needed to
overcome the
water column above them. Many produce dead zones where, for example, dead
cells
accumulate and contaminate the medium. In the present invention, sparger tubes
are
created by shaping and sealing a tube formed from a very portion of the
flexible material
that contains them. Inherently, they become anchored to the material that
contains the
CA 02856253 2014-07-08
medium to be sparged and therefore do not require additional support to keep
them
down. Being integrated into the walls of a bioreactor, they are virtually free
of cost; they
can be rolled or disposed along the disposable bioreactor that contains them.
In
embodiments comprising more than one sparger tube, displacing fluids
alternatingly in
various tubes creates a controlled agitation within a liquid medium. They have
a wide
range of applications. They are an essential component of algae culture, of
fish and
shrimp farming and aqua farming of the like. They have applications in
flexible
fermenters for brewing yeasts, wine and beer; they may be used to sparge
leachate in
bioreactor landfills, to mix and breed microbial bio-insecticides in
agriculture or to
produce antibodies and vaccines in bioreactors. They can also be used in
chemical
reactors for injection and mixing of gases and fluids. In one embodiment of
the
invention, having one or multiple non-perforated tubes inside a larger tube
creates a
jacket for heating or cooling, for agitating by inflating or deflating the
smaller tubes. It
also enables the displacement of liquids within a container by inflating or
deflating
anchored tubes present in the container.
FIGURES
Figure 1 is a cross-sectional view of a sleeve with a gas sparger tube from
the prior art.
Figure 2 is a close-up, cross-sectional view of a gas sparger tube projecting
gases in
two directions
Figure 3 is a cross-sectional view of a tubular bioreactor enclosing two
sparger tubes
Figure 4 is a cross-sectional view of a hump-shape bioreactor shell housing a
bottom
inflated tube and an upper tube enclosing two sparger tubes
Figure 5 is the hump-shape bioreactor of Fig. 4 with a deflated bottom tube
Figure 6 is a perspective view of a method for shaping a sparger tube within a
closed
larger tube
CA 02856253 2014-07-08
Figure 7 is a perspective view of a method of shaping two sparger tubes in a
flat base
sealed to a cover to become a tube
THE DETAILED DESCRIPTION OF THE INVENTION
As described in the background, there are a number of designs of bioreactor
systems
known in the art. The sparger system 20 of this invention can be incorporated
into
bioreactor systems where the possibility of forming the tube 20 from the
material 12 of
the wall is possible. Furthermore, as shown in Figures 2 and 3, built-in
sparger tubes 20
of the invention are inherently anchored to the material containing a medium
and act as
mixers and wave generators when fluids pressured alternatingly in the tubes
inflate
while creating bubbles and deflate.
Flexible Bioreactors
Flexible bioreactor systems 10 or 50 have a wide range of applications.
Transparent
bioreactors known as photobioreactors or PBRs are rapidly gaining recognition
among
algae farmers for producing biofuels, bio-chemicals and a very wide range of
nutraceuticals and pharmacueticals. PBRs are often used in hatcheries for
growing
larvae, rotifers and for producing algae-based feed for aquaculture and animal
husbandary.
Bioreactors 10 may also be used as flexible yeast fermenters for hydrolyzing
sugars or
for brewing alcohols such as wine and beer.
Bioreactor landfills 10 may be used for sparging leachate of municipal wastes.
More recently, a new generation of bioreactors 10 is emerging for breeding
microbial
bio-insecticides to protect grains and agriculture feedstock against pests.
The same
types of bioreactors 10 may be used for developing antibodies, vaccines and
enzymes.
Chemical reactors 10 use sparger tubes 20 for injection and mixing of gases
and fluids.
CA 02856253 2014-07-08
Flexible bioreactors are known in the art. These are generally constructed
from a
translucent flexible material that is impermeable to liquid medium.
Materials Comprising Bioreactors
Materials used in flexible bioreactors 10 include low density polyethylene,
high-density
polyethylene, polyvinyl chloride and a combination thereof. These materials
are produced in the
form films or membranes.
Materials used in flexible bioreactors 10 may be preferably recyclable or
compostable.
In some cases, they may be bio-degradable when used for short term processing
or in
short term growth cycles often to reduce cross-contamination.
The strength of the plastic is also an important consideration. Different
thicknesses of
plastic may be used, according to end purposes and standard practice. For
example,
for single-use bioreactor bags 10 with sparger tubes 20 thicknesses may vary
between
50 microns (0.05mm) to 100 microns (0.01mm). For multiple-use bioreactor bags
10,
thicknesses may vary from 100 micron to 300 microns.
Liquid mediums in photobioreactors 10, 50 may vary from sterilized mediums
used for
growth of monoculture algae species often cultured for the nutraceutical and
pharmaceutical industries to algal mediums dealing with extremely toxic
wastewaters
present in the mining or oil and gas industries.
Sparger Fluid
The sparger system 20 can deliver a number of different fluids, including but
not limited
to gases such as air, carbon dioxide, ammonia, argon, chlorine and the like.
Vapours
and liquids containing micro-nutrients and chemicals can also be injected
along other
liquids or gases. As an example, a bioreactor 10 may contain a gas with
sparger tubes
20 delivering one or multiple liquids.
The Sparger Tube
Commercial algae farmers are facing two important challenges - sparging
without
causing too much shear or dead zones and the agitating large masses of water
without
CA 02856253 2014-07-08
using too much energy. The present invention overcomes these limitations by
disclosing
a sparger tube 20 that prevents dead zone and reduces substantially the amount
of
energy required for agitation.
Figure 1 illustrates a prior art flexible sparger tube 20' that has a single
pinholes 22' for
sparging gases frontward. Such a system suffers from the limitation that the
sparger
tube 20' creates a dead zone around sparger system 20'. Dead zones are one of
the
sources of contamination where dead cells accumulate causing sometimes growth
crashes in large-scale algae monoculture facilities. In one embodiment of the
invention,
sparger tube 20 overcomes this limitation by providing a sparger tube 20 that
sparges
fluids, such as gases, vapours or liquids, from two oppositely-oriented
pinholes 22 that
sparging fluids in two opposite directions, perpendicular to tube 20 and
slightly
downwards. In this sparger system 20, flow exit is located close to the tube's
sealing line
14 in contact with the plastic bottom floor 12.
In one embodiment of the invention, number of pinholes 22 per surface area is
the
same along the full length of sparger tube 20. In another embodiment, the said
number
is intermittently variable along the tube. In yet another embodiment, two,
three or more
pinholes are punctured concurrently along a perforation line. In an
embodiment, the
radial position of pinholes 22 is the same, while in another embodiment said
position is
varied along the length of sparger tube 20. In one embodiment, the diameter of
sparger
tube 20 is varied along the length of the sparger tube 20.
Pinholes 22 are perforated or punctured by a single puncturing action that
concurrently
punctures the two adjacent walls present in each fold. Diameter sizes for
sparger tubes
20 are generally limited to 16mm and 20mm. The sparger tube 20 of the present
invention does not suffer from any diameter size limitation. In one
embodiment, the
diameter size of sparger tube 20 varies along the length of the sparger tube
20
according to a pre-determined pattern.
Figures 6 and 7 describe how a perforator 60 such as, but not limited to, a
needled
wheel, a laser cutter, a waterjet cutter, a pneumatic punch or any other
perforator means
of the like may perforate from any one side of a folded, flexible, puncturable
plastic
sheet 12 two pinholes 22 in a single step.
CA 02856253 2014-07-08
Figure 6 illustrates how the perforated portion of a closed plastic sleeve or
tube 12 is
tucked into the same sleeve 12 to create a gusset 72 using the gusseting
roller 70. To
seal external edges of the gusseted portion 14, a band sealer 80 or any heat
sealer of
the like may be used.
The Sparger System Incorporating Agitation
It is known that in any photosynthetically-driven algae farming system, proper
agitation
of algal medium is critical to expose all algae cells to light, no matter
medium depth.
Traditionally, substantial amount of energy is allocated to agitation of the
algal medium.
This challenge is addressed by the present invention by providing a sparger
system that
generates aeration and mechanical agitation in a single process.
Figure 3 shows a bioreactor having two sparger tubes 20 in operation. As
shown, the
shape and size of a fully blown sparger tube 20 as shown in Detail A of Figure
2 varies
from the shape of a more contracted sparger tube 20 shown at the right side of
bioreactor 10. Therefore, in addition to the agitation created by the sparging
and
bubbling effect, this shape variation of the sparger tube 20 increases the
amount of
mechanical agitation and mixing provided by the sparger tube 20.
In one embodiment of the invention, displacing alternatingly fluids under
slight pressure
between at least two of the sparger tubes 20 placed apart creates an agitation
that when
harmonically controlled generates major waves. The fact that sparging must be
done
anyway, using the same air, gas or liquid generated by pumps and switching
flow
alternatingly between two sparger tubes 20 does not increases the energy
demand on
the pump. In fact, very little energy is required to operate micro-electronics
and solenoid
valves to achieve switching. In an example where traditionally 4000 Watt of
energy was
needed to agitate a mass of 4000 liters of water using a mechanical agitator,
the same
agitation was achieved using only 50 Watt to switch gas flow alternatingly
between two
sparger tubes 20 placed apart, using microelectronics and solenoids.
CA 02856253 2014-07-08
In one embodiment of the agitation system, physical vibration of air exiting
from sparger
tube 20 is used as a source of agitation using pressure pulsation or variation
similar to
"water-hammer" in liquids.
Volume and pressure fluctuation of gases generated in sparger tubes 22, 24 is
created
by adding to an air or carbon dioxide gas delivery system a means such as, but
not
limited to, modified diaphragm, a floating tongue, an unbalanced or balanced
rotor, an
unbalanced or balanced propeller, an electrically-driven modulator or pulsator
or a
combination thereof.
Inflatable Tubes
As shown in Figures 4 and 5, in anundulated-shape bioreactor 50, inflatable
tube 42
positioned under liner 12 causes level of liquid medium 30 to rise and to
fluidingly
communicate with other liquid portions of bioreactor 50. Deflating air 32 from
tube 42
causes liquid to recess in separate chambers of the ondulated-shape bioreactor
50. As
a result of this separation, portions of liquid medium 30 may be processed
locally ,
isolated from the remaining portions. For example localized processing such as
filtering,
intense illumination, generation of electromagnetic fields, treatments with
special
nutrients or chemicals may become possible on only a portion of a liquid.
Moreover, if a
dedicated portions of the undulated bioreactor 50 contains special processors
such as
gels or special catalysts, then localized treatment of only that portion of a
liquid medium
becomes possible. Such a localized treatment is required when using gels and
sponges
to collect elements generated from various organisms such when milking
cyanobacteria.
Methods of Forming Soarger Tubes
(Method 1)
Figure 6 shows one method of creating a sparger tube 20 in a thin film plastic
12. This
method is a one-sheet method. After proceeding with a blown film extrusion
process,
one border of plastic tube or sleeve 12 is drawn over a perforating equipment
60, such
as a punch, a needle wheel or a laser cutter. The perforated portion is then
drawn into
gusseting wheel 70 that tucks in the perforated portion in sleeve 12 before a
sealing
machine 80 bonds the newly formed edge. Sealing may be performed using
ultrasonic,
heat or radiowave welding 80. The same method applies for shaping two sparger
tubes
CA 02856253 2014-07-08
20 in the same thin film plastic 12. To achieve this, additional equipment 60,
70 and 80
are positioned in a mirror position than for building one sparger tube 20. To
shape three
or more sparger tubes 20 in a same sleeve 12, the method requires to re-fold
sleeve 12
in a manner where new fold edges are created and re-apply the same tube-
shaping
method.
In an embodiment of sparger tube-making one-sheet method, external edges of
sheet
12 are sealed together for form the sealing line 18 as shown in Figure 3.
(Method 2)
Figure 7 shows one method of creating a sparger tube 20 in a two-sheet method.
The
method consists in forming one or two sparger tubes 20 along the lateral sides
of an
elongate sheet 12 that originally may have been a closed sleeve 12 or a sheet
12 folded
on both sides as shown in Figure 7. Sleeve 12 longitudinal edges are each
perforated
by a perforator 60. Bottom wall of sleeve 12 is then cut open by a knife 40
and edges of
sleeve 12 are drawn upward to meet an upper sheet 16. In a final step,
opposite edges
of both sheets 12 and 16 are sealed together to form a new sleeve 10 that
encloses the
two sparger tubes 20.
The scope of the claims should not be limited by the preferred embodiments set
forth in
the examples, but should be given the broadest interpretation consistent with
the
description as a whole.
