GB2205581A

GB2205581A - Photobioreactor

Info

Publication number: GB2205581A
Application number: GB08713345A
Authority: GB
Inventors: Lee Fisher Robinson; Angus William Morrison; Mark Robert Bamforth
Original assignee: Biotechna Ltd
Current assignee: Biotechna Ltd
Priority date: 1987-06-08
Filing date: 1987-06-08
Publication date: 1988-12-14
Anticipated expiration: 2007-06-08
Also published as: GB2205581B; AU1744188A; GB8713345D0

Abstract

In a photobioreactor, a synthesis mixture is caused to flow through a pair (5), (7) of substantially transparent tubes supported on support surfaces provided by an upstanding core structure (1). The support surfaces and the core are such that natural light can fall upon both tubes and a biomass synthesis product is withdrawn. <IMAGE>

Description

PHOTOBIOREACTORS This invention relates to photobioreactors which are employed in biomass production. The present invention seeks to provide an improved photobioreactor and a biomass production process which can be carried out on a substantial commercial scale with reduced land usage and improved operating efficiency.

According to the present invention, a photobioreactor comprises an upstanding core structure providing a first support surface, a substantially transparent tube wound on and supported from the first support surface, a second support surface provided by the structure outside the first support surface and a substantially transparent second tube wound on and supported from the second support surface, the core structure and support surfaces being such that, in use, both tubes are exposed to natural light, means for causing a synthesis mixture to flow through the wound tubes and means for withdrawing a biomass synthesis product stream.

By employing first and second tubes supported from the core structure, the capacity of the reactor is significantly increased. This means that, for a particular ground surface area, the capacity of the' reactor is higher than when only a single tube is employed.

In one embodiment of the invention the core structure comprises a plurality of vertical columns which have a sleeve of generally cylindrical form surrounding the columns and supported from them. The sleeve provides a support surface. Additional vertical columns are provided outside the first sleeve and these columns support on their outside a generally cylindrical sleeve of open-work construction. The first tube may be supported on the outside of the first cv3nnorlcal sleeve and the second tube is supported on the outside surface of the second sleeve.

In an alternative arrangement, one set of vertically extending columns is provided and the columns support inner and outer sleeves of generally clinsr-^al form. The first substan.tially transparent tube is ported on the inside support surface of the inner sleeve and the second substantially transparent tube is supported on the outside surface of the outer sleeve.

In use, substantial amounts of natural light can pass through the outer substantially transparent tube and the second support surface on to the first substantially transparent tube. Furthermore, in the case of high reactors of, say, four metres diameter and five metres high, direct light reaches the interior of the reactor through the open top. This light then passes through the inner tube and reaches the outer tube which results in greater light utilisation for a given photosynthetic reaction.

To increase the light which falls upon the tubes it is proposed to locate artificial light sources between the inner and outer sleeves. When the light sources are energised, they allow production to proceed during the hours of darkness or when the natural daylight is insufficient, as may be the cesse during the winter months. The wavelength of the light emitted from the artificial sources is preferably from 350 to 750 nms.

Preferably, the support surfaces provided by the core structure are substantially cylindrical and the tubes are wound helically on the cylindrical surfaces. However, it will be appreciated that the core need not be cylindrical and may, for example, be in the form of a truncated cone. Such a shape can be efficient for light utilisation in tropical countries where the sun shines vertically downwards, the conical structure minimising a shadow formation.

The synthesis mixture may be pumped to the top of the core structure and allowed to flow downwardly through both the wound tubes under turbulent conditions or, alternatively, the mixture may be pumped up one of the tubes and allowed to flow down the other.

A particularly preferred tube material is polyvinyl chloride, especially food grade polyvinyl chloride which has excellent light transmission properties and low cost. It also has the valuable advantage of being resistant to attack by the biomass medium. However, tubes of polyethylene or other transparent flexible tubing; even shaped rigid transparent tubing suitably formed in an arc shape may be used; and curved glass or glass/resin tubing bent into suitable arc shapes can be used. It has been found that transparent polyvinyl tubing re-inforced with nylon or other suitable filaments by winding on the outer surface will withstand the pressures and tem.peratures encountered in pumping the photosynthetic media through the tube.

The lines feeding liquid to the several ractors and the off-take lines can all be built to allow separate sections of tubing in the reactors to have individual attachments in order to minimize pressure drop.

In order that the invention may be more readily understood, it will now be described, by way of example only, with reference to the accompanying drawings, in which Figure 1 is a diagrammatic side view of a photobioreactor; and Figure 2 is a plan.

The photobioreactor comprises a core structure consisting of a plurality of vertical columns 1 located with inner and outer cylindrical sleeves 2, 3, respectively, which are supported by the columns 1.

The inner sleeve 2 provides a support surface 4 on which a first substantially transparent tube 5 of plastics material is wound in helical form. The tube is supported on the support surface. The sleeve 3 provides a generally cylindrical support surface 6 and a second tube 7 of substantially transparent material is wound on the support surfac in a helical manner and supported from the sleeve. The two tubes 5, 7 may be connected together at the upper end of the reactor so that the two tubes are effectively in series.

Alternatively, a header tank (not shown) is mounted on top of the columns 1 and the two tubes are connected at their uper ends to the header tank so that effectively the two tubes are in parallel. The sleeve 6 is made of of open-work construction and, as the tube 7 is of substantially transparent material, light can pass through the tube 7 and the sleeve 3 on to the tube 5 mounted on the sleeve 2.

If desired, sources of artificial light, such as fluorescent tubes, 8 may be positioned between the sleeves 2, 3 so that the process can continue under artificial lighting conditions during the hours of darkness or when natural daylight is insufficient for efficient operation of the process.

In use, a synthesis mixture is pumped along the tubes either in series or parallel and they are exposed to natural light. The product may be collected from a header tank at the top of the columns when such a tank is provided or, alternatively, it may be collected from the lower end of the downward section of the serielly connected tubes.

In an alternative arrangement, the inner and outer sleeves 2, 3 may be secured to separate column structures, the sleeve 2 being mounted on the outside of an inner set of columns and the sleeve 3 being mounted on the outside of a second set of columns which in themselves are positioned outside the sleeve 2.

In a further embodiment of the invention, an additional sleeve is located inwardly of the sleeve 2 and this sleeve is supported by additional columns. A further tube of opaque material is wound on the outside surface of the additional sleeve. The synthesis mixture pumped through this tube does not experience wight falling upon it and, consequently, it is possible for a photophobic and a photosynthetic reactor to be contained within a single reactor.

Claims

Claims:

1. A photobioreactor comprising an upstanding core structure providing a first support surface, a substantially transparent tube wound on and supported from the first support surface, a second support surface provided by the core structure outside the first support surface and a substantially transparent second tube wound on and supported from the second support surface, the core structure and the support surfaces being such that, in use, both tubes are exposed to natural light, means for causing a synthesis mixture to flow through the wound tubes and means for withdrawing a biomass synthesis product.

2. A photobioreactor as claimed in claim 1, in which the core structure comprises a plurality of spaced apart vertical columns having a hollow vertical cylindrical sleeve supported on the inside of the columns and a hollow vertical cylindrical sleeve supported on the outside of the columns.

3. A photobioreactor as claimed in claim 2, in which the first support surface is the inner surface of the inner sleeve and the second support surface is the outer surface of the outer sleeve, said sleeves being such as to permit natural light to pass therethrough.

4. A photobioreactor as claimed in claim 3, in which the sleeves are of open mesh construction.

5. A photobioreactor as claimed in claim 1, in which the core structure comprises a first group of spaced apart vertical cloumns having a hollow vertical cylindrical sleeve supported on the outside of the columns, and a second group of spaced apart vertical columns outside the first group, said second group of columns having a hollow vertical cylindrical sleeve supported on the outside of the columns.

6. A photobioreactor as claimed in claim 5, in which the first and second support surfaces are provided by the outer surface of the inner and outer cylindrical sleeves, respectively, said outer sleeve being such as to permit natural light to pass therethrough.

7. A photobioreactor as claimed in claim 6, in which the outer cylindrical sleeve is of open mesh construction.

8. A photobioreactor as claimed in claim 6 or 7, in which artificial light sources are positioned between the inner and outer sleeves.

9. A photobioreactor as claimed in claim 1, in which the first and second support surfaces are provided by sleeves of frusto-conical form.

10. A photobioreactor as claimed in any preceding claim, in which the tubes are of plastics material.

11. A photobioreactor as claimed in claim 10, in which the tube material is polyvinyl chloride.

12. A photobioreactor as claimed in any of the claims 1 to 9, in which the tubes are of glass or glass/resin.

13. A photobioreactor as claimed in any preceding claim, in which the tubes are connected in series.

14. A photobioreactor as claimed in any preceding claim, in which a tube of opaque material is supported inwardly of the first support surface, said tube forming part of a photophobic reactor.

15. A photobioreactor substantially as hereinbefore described with reference to the accompanying drawing.