CA2856253A1 - Sparger system - Google Patents

Abstract

A sparger system is built-in, shaped and sealed from the same flexible material that supports it. Pressurizing alternatingly multiple sparger tubes causes agitation and waves. The system's demand for energy is very low.

Description

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 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.

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 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 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 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.

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 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 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.

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.

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 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.

Claims

SPARGER SYSTEM
I Claim:
1) A flexible sparger system for delivery of a fluid in two opposite directions, said sparger system comprising:
- a flexible, foldable, puncturable and sealable plastic base;
- said base provided with one or multiple tube-size folds;
- a pattern of pinholes perforated at the edges of each folded wall;
- a sealing line joining said folded walls at a position slightly behind pinholes and further away from the folded edges; said arrangement creating one or multiple sparger tubes shaped over a base and able to sparge a fluid in two opposite directions along the full length of each tube.
2. The sparger system of claim 1 wherein distance between pinholes is the same.
3. The sparger system of claim 1 wherein the number pinholes per surface area varies along the tube length following a determined pattern.
4. The sparger system of claim 1 wherein said pattern includes two or three pinholes perforated at the same time.
5. The sparger system of claim 1 wherein the diameter of the sparger tube varies along the length of the sparger tube.
6. The sparger system of claim 1 wherein the radial position of the pinholes varies along the length of the tube.
7. The sparger system of claim 1 wherein pinholes are perforated along one, two or more perforation lines on each side of the sparger tube.

8. The sparger system of claim 1 wherein pinholes are perforated along perforation lines that vary relative to each other according to a pre-determined pattern.
9. The sparger system of claim 1 wherein edges of the plastic base that supports one or more sparger tubes are removably sealable for creating an openable and closable plastic sleeve enclosing said sparger tubes.
10. The sparger system of claim 1 wherein the borders of said base are joined and sealed together creating a closed tube enclosing said built-in sparger tubes.
11. The sparger system of claim 2 creating a stand-along bioreactor tube.
12. The sparger system of claims 2 and 3 wherein the sheet-like base is light transmissible for creating a stand-alone photobioreactor tube for growth of micro-organisms.
13. The sparger system of claims 1 to 4 wherein applications for a flexible sheet-like base with a built-in sparger system include, but are not limited to, a liner sheet laid under a liquid surface, a liner tube inserted inside other containment systems, a liner tube sealed at one end and inserted inside other containment systems, a stand-alone horizontal bioreactor chamber, a vertical bioreactor bag with bottom and/or side sparger tubes, a stand-alone horizontal bioreactor chamber made of a bottom flexible sheet including sparger tubes and an upper sheet made of a different permeable or non-permeable material, and a combination therof.
14. The sparger system of claim 1 wherein displacing alternatingly a pressurized fluid into two or more of said gas sparger tubes creates a controlled agitation in a liquid medium placed above said two sparger tubes.

15. The sparger system of claim 1 wherein multiple sparger tubes generate aeration and mechanical agitation in a single process.
16. The sparger system of claim 1 wherein pressurizing alternatingly multiple sparger tubes generates, in addition to the agitation created by the sparging and bubbling effect, a shape variation of the sparger tube that increases the amount of agitation and mixing provided by the sparger tubes.
17. The sparger system of claim 1 wherein pressure variation or pulsation of fluids exiting from a sparger tube becomes a source of agitation, similar to "water-hammer" in liquids.
18. A stand-alone, one-piece photobioreactor system comprising:
- a flexible, light transmissible bioreactor chamber adapted for biomass growth;
- a sparger system including multiple sparger tubes shaped from folding, perforating and sealing portions of said bioreactor chamber;
- an agitation system created by displacing alternatingly pressurized fluids into said sparger tubes.
19. A flexible tubular system enclosing one or multiple built-in tubes, said tubular system comprising:
- an open flexible, foldable and sealable plastic base;
- said base provided with one or multiple folds;
- a sealing line sealing together the opposite walls in each fold at a tube-size distance away from each of said fold edges;
- a sealing line sealing distant edges of said base for creating an external tubular system incorporating one or multiple internal tubes.
20. The built-in tubes inside a tubular system of claim 15 wherein said internal tubes contain similar or dissimilar fluids or gases at different phases.

21. The built-in tubes inside a tubular system of claim 15 wherein said internal tubes are inflatable.
22. A method for creating one or more sparger tubes in a plastic sheet; said method comprising:
- providing a plastic sheet with one or multiple folds;
- perforating a pattern of pin holes concurrently in the two adjacent walls from each fold, said holes being positioned near and along said edges;
- sealing together the two adjacent walls from each fold at a position slightly away from the edges for creating a perforated sparger tube along each of said folded edges.
23. A method for creating one or two sparger tubes inside a closed plastic sleeve;
said method comprising:
- providing a layflat plastic sleeve;
- inserting pin holes along one or the two longitudinal edges of said layflat sleeve;
- tucking and gusseting the perforated sleeve edge into a small portion of the layflat sleeve edge;
- heat sealing togther newly created V-shaped edges of each newly created gusset, thereby forming an internal sparger tube inside a layflat sleeve.
24. The method of claim 22, wherein opposite external edges of the said straightened sheet are sealed to edges of a second layer of plastic sheet of substantially same width to form collectively a closed bioreactor sleeve having internal sparger tubes.
26. A bioreactor for processing separately a portion of a medium comprising:
- an undulated-shape bioreactor shell;
- an inflatable plastic tube in at least one of the bottom cavities of said bioreactor shell;

- a flexible plastic liner positioned in said bioreactor shell and above said inflatable plastic tube;
- wherein inflating said plastic tube causes fluid communication between all liquid medium portions and deflating said tube causes fluid recess in separate chambers of the undulated¨shape bioreactor.