GB2423525A

GB2423525A - Photobioreactor solvent extraction process unit

Info

Publication number: GB2423525A
Application number: GB0504043A
Authority: GB
Inventors: Gareth King
Original assignee: Individual
Current assignee: Individual
Priority date: 2005-02-26
Filing date: 2005-02-26
Publication date: 2006-08-30
Also published as: GB0504043D0

Abstract

A photobioreactor solvent extraction process unit that promotes the growth of biolipid producing biological entities, and then removes said biolipids from the biological entities. It is constructed and operated in a direct hybrid plug flow reactor (PFR) and oscillatory flow reactor (OFR) configuration 4 and 7. The process unit has a side entry contacting pattern/delivery system for the extracting solvent 6 and 8. The extracting solvent is used to remove prized biolipids from the biological entities in the culture mixture. The biolipid and solvent then exit the process unit. The solvent/biolipid mix can then be further treated to ultimately yield biodiesel. The biological entity is exemplified as an algal species, Botryococcus braunii.

Description

Photobioreactor Solvent Extraction Process Unit This invention relates to

a process unit that cultivates phototroph biological entities on large scales; and extracts biolipids from the biomass to be further processed to yield Biodiesel fuel.

Background

Our society is highly dependent on carbon-based fuels.

Unfortunately our current source of these fuels, namely crude oil, is nonrenewable. Fuels derived from renewable sources pose an attractive solution to future energy demands.

Biodiesel is one such renewable carbon based fuel source.

Algae produce biolipids that can be extracted and processed to yield biodiesel. Botryococcus braunii - race A algae is one such biological entity that can be used in such a capacity.

Statement of Invention

This invention solves the problem of cultivating biological entities on a large scale whilst simultaneously extracting the biolipids they produce. These biolipids are used in the production of Biodiesel.

A Plug flow reactor - PFR Photobioreactor is fed with the biological entities and other essential raw materials to promote and encourage their growth. This liquid is essentially a cultivation mixture or soup'. It is bubbled with carbon dioxide gas via side entry contacting patterns. Oxygen gas (02) evolved by the biological entities during photosynthesis is displaced from the PFR via Nitrogen gas pumps that inject nitrogen directly into the PFR. The dimensions of the PFR and flow rates into/out of the PFR are designed so that a sufficient concentration of biomass has been generated within the PFR. This is called the residence time of the reactor. The residence time is designed so enough biological entities are present in the photobioreactor to be passed into the next section of the process unit - the solvent extraction stage.

The solvent extraction stage is essentially an Oscillatory flow reactor OFR in a plug flow reactor - PFR configuration. The solvent to be used to remove the biolipids is introduced via a side entry-contacting pattern. Many different means, such as diaphragm pumps or piston pumping mechanisms within the solvent extracting region of the process unit can produce the oscillatory flow. Baffles within this section will also enhance solvent contacting with the cultivation mixture.

The solvent - for example - hexane - strips' the lipids of f the cells. If the biolipids grow inside the cells; then cell disruption techniques can be employed within the reactor unit to liberate them. The solvent then dissolves the biolipids from the water rich cultivation mixture. The hexane, containing biolipids, is immiscible with water. Thus a two-liquid mixture should result; one composed of water and cells and one composed of hexane, biolipids and cells. Thus this process operates on the principles of solvent extraction.

Further down the length of the OFR, the flow becomes less oscillatory. The reactor is designed to promote laminar liquid flow. This will encourage the formation of a two-liquid mixture as described above.

The hexane, biolipids and cell liquid is then pumped out of the process unit, and ready to be treated further to yield Biodiesel.

Advantages This invention allows industrial scale production of biolipids derived from phototroph biological entities. The invention grows phototroph biological entities and simultaneously extracts the desired biolipids in one single unit operation.

This is advantageous because it reduces the number of process units that would normally be needed to facilitate this procedure.

Fewer units are needed. Each unit has many associated control systems, so fewer units implies fewer costly control systems.

Less control systems means the process is easier to control as well. This in turn reduces costs. This invention also allows high product quality. The cultivation and biolipid extraction operations are carried out insitu'. The chances of contamination are greatly reduced by combining both steps.

Additionally less piping is needed on the plant as well. Again fewer control systems are needed, and less pipe is needed, resulting in lower operating and start up costs.

An example of the invention shall now be described by referring to the accompanying drawings.

* Figure 1 illustrates the general structure and layout of the invention. It shows flow patterns within each of the three sections, which comprise the overall unit. It also highlights how side entry systems are used to deliver various chemicals into the reactor.

* Figure 2 shows an element of the photobioreactor Plug flow reactor (PFR) section, from the side. It illustrates a generic support structure to be used down the length of the invention.

* Figure 3 highlights the Oscillatory flow reactor (OFR) section of the invention. It also illustrates the generic support structure as shown in figure 2. Figure three also shows the side entry contacting mechanism for liquid-liquid extraction and the baffles used to promote turbulent flows.

Figure 1 shows the general structure of the invention.

A variable transparency Tubular/circular cross-section pipe 12 makes up the photobioreactor PFR section. This variable transparency is achieved by light reactive materials or by adjustable screening. It has variable transparency to ensure the incident sunlight 1 is not too intense and thus encourage a phenomenon known as photoinhibition within the phototrophs. The feed to the unit 2 primarily consists of biological entities, water, nutrients required by the biological entities and carbon dioxide gas; this forms a growth culture mixture. The culture mixture flows through the PFR 3, for a designated residence time to concentrate up the biomass. The biomass increases down the length of the invention because the phototrophs grow and divide as they mature. To encourage this growth carbon dioxide gas and nutrients are introduced via a side entry- contacting pattern 13 in strategic locations along the length of the invention. Oxygen gas evolved from photosynthetic activity is removed from the invention by injecting nitrogen gas directly in the culture mixture in a side entry fashion 16.

The whole process unit is supported via a metallic generic support system 14. Metal screws 15 fasten the collar around the process unit.

When the algal biomass has been increased to a commercially viable concentration the PFR section terminates & culture mixture passes directly in to the oscillatory flow reaction section as shown by 4. Oscillatory flow 5 is encouraged and promoted and solvent is introduced by side entry contacting pipes 6.

The solvent is injected into the OFR section.

This occurs along the length of the OFR section via injection pipes - 8 which are fed by the side pipes 6. Turbulent flow is promoted by the presence of Baffles 11. This increases contacting between the solvent 18 and the algae rich culture mixture.

The OFR section does not have to be made of partially transparent material and can be made of a suitable polymer or metal 17.

When sufficient contacting has taken place and the biolipids from the algae have been removed and enter the liquid solvent phase, the OFR section terminates 7 and enters a settling' section 10.

Laminar flow is encouraged within the settling section. The immiscible solvent, containing the biolipids, and culture mixture (water, nutrient and cells) forms two distinct layers that exit the process unit 9.

Claims

Claims 1. A photobioreactor solvent extraction process unit that

promotes/encourages growth of biological entities that produce biolipids, disrupts biological entities to liberate biolipids and then removes said biolipids via solvent extraction from the biological entities, after the biological entities have reached a desirable concentration.
2. A photobioreactor solvent extraction process unit according to claim 1 that is constructed and operated in a direct hybrid plug flow reactor (PFR) and oscillatory flow reactor (OFR) configuration.
3. A photobioreactor solvent extraction process unit according to claims 1 & 2 that has a side entry contacting pattern/delivery system for the extracting solvent.
4. A photobioreactor solvent extraction process unit as according to claim 1, 2, & 3 that has a variable transparency PFR section to negate the phenomenon of phototroph photoinhibition.
5. A photobioreactor solvent extraction process unit as according to claim 4 that incorporates baffles in the OFR section to promote turbulent flow and increase contacting efficiency and has a generic support structure.