Reactor for algae culture

Abstract

A reactor for dissolving carbon dioxide in algae, comprising: means for introducing carbon dioxide into a reaction chamber; an inlet nozzle configured to inject a growth medium containing algae into the reaction chamber; and a valve configured to control the outflow of algae. Within the reaction chamber, carbon dioxide is dissolved in the growth medium, causing algae to grow, which accumulates at the bottom of the reaction chamber, forming an algae column that substantially prevents release of carbon dioxide to the environment.

Description

Technical Field

[0001] The present invention relates to a reactor for dissolving carbon dioxide in a growth medium containing algae. Background Art

[0002] Algae cultivation farms or bioreactors that grow algae products for fuel, biochemicals, and biomass food are considered carbon-negative industries. The carbon dioxide absorbed by the algae typically comes from the surrounding terrestrial air, where it is converted into carbohydrates and lipids, making the algae cultivation part of a carbon dioxide sequestration cycle. Literature and industry journals report on the importance of increasing carbon dioxide levels in photobioreactors or cultivation raceways to accelerate the growth of algal biomass.

[0003] Conventional methods for dissolving carbon dioxide from algae culture media use sparger systems or bubbling chambers. Unfortunately, due to inefficiencies in gas-liquid mixing, over 90% of the carbon dioxide is lost to the environment. This release of carbon dioxide into the environment negatively impacts the carbon footprint of a particular algae cultivation project.

[0004] It is therefore an object of the present invention to provide a reactor suitable for dissolving carbon dioxide in algae, which overcomes the problem of carbon dioxide release into the environment. Summary of the Invention

[0005] In one aspect of the present invention, there is provided a reactor for culturing algae, comprising:

[0006] means for introducing carbon dioxide into a reaction chamber within said reactor;

[0007] an inlet nozzle positioned at a top of the reactor and configured to spray a growth medium containing algae into the reaction chamber; and

[0008] a valve positioned at the bottom of the reactor and configured to control the outflow of algae;

[0009] Characterized in that carbon dioxide dissolves in the growth medium, causing algae to grow, and the algae accumulates at the bottom of the reaction chamber to form an algae column that substantially prevents the release of carbon dioxide to the environment.

[0010] In one embodiment, the reaction chamber is pre-filled with carbon dioxide at a pressure of up to 2 bar before the growth medium containing the algae is introduced into the reaction chamber.

[0011] In one embodiment, the reactor further comprises at least one optical sensor to regulate the height of the algae column within the reaction chamber.

[0012] In one embodiment, the reactor further comprises a pressure regulator positioned at the means for introducing carbon dioxide to regulate the pressure of carbon dioxide in the reaction chamber.

[0013] In one embodiment, the reactor further comprises a pump attached downstream of the inlet nozzle to pump the growth medium containing the algae at a minimum flow rate to form pressurized pellets of growth medium entering the reaction chamber.

[0014] Advantageously, the small particles of the growth medium provide additional surface area for carbon dioxide to dissolve to form bicarbonate ions. The bicarbonate ions dissolved in the medium are consumed by the algae as carbon building blocks.

[0015] Preferably, the growth medium also contains saline.

[0016] In one embodiment, the dissolution rate of carbon dioxide into bicarbonate ions is variable by adjusting the pressure of carbon dioxide in the reaction chamber.

[0017] Advantageously, the algae removed from the reactor can be used in algae cultivation farms or bioreactors for the production of fuels, biochemicals, and biomass foods.

[0018] Advantageously, the reactor consumes 39% to 53% of the carbon dioxide and is able to substantially prevent carbon dioxide from escaping to the environment (<0.02% loss) compared to conventional sparger and bubbling systems.

[0019] In one aspect of the present invention, there is provided use of a reactor for dissolving carbon dioxide in a growth medium containing algae to cultivate the algae. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] It will be convenient to further describe the invention with reference to the accompanying drawings which illustrate possible arrangements of the invention. The invention may also adopt other arrangements and therefore the particularity of the accompanying drawings should not be understood as superseding the generality of the preceding description of the invention.

[0021] Figure 1 The reactor of the present invention is shown.

[0022] Figure 2a The carbon dioxide consumption rates of the reactor of the present invention and a conventional bubbling system were compared when utilizing fresh water.

[0023] Figure 2b The production of bicarbonate ions and pH levels of the reactor of the present invention and a conventional bubbling system were compared when utilizing fresh water.

[0024] Figure 3aThe carbon dioxide consumption rates of the reactor of the present invention and a conventional bubbling system were compared when using brine.

[0025] Figure 3b The production of bicarbonate ions and pH levels of the reactor of the present invention and a conventional bubbling system were compared when using brine. DETAILED DESCRIPTION

[0026] refer to Figure 1 The reactor (100) is a long column comprising: a means for introducing carbon dioxide (102) into a reaction chamber (104); an inlet nozzle (106) positioned at the top of the reactor for injecting a growth medium containing algae into the reaction chamber; and a valve (108) positioned at the bottom of the reactor to control the outflow of algae from the reaction chamber. Preferably, the reactor is a polymer-based column in a vertical position with a height in the range of 1-2 meters. Prior to introducing the growth medium into the reaction chamber, the reaction chamber is pre-filled with a pressure of up to 2 bar.

[0027] A pump attached downstream of the inlet nozzle continuously pumps the growth medium containing the algae into the inlet nozzle at a minimum flow rate, thereby forming a mist-like particle of the growth medium that trickles down and collects in the reaction chamber where it mixes with the high-pressure carbon dioxide. Preferably, the flow rate of the growth medium into the reaction chamber is 0.85 lpm.

[0028] Mixing within the reaction chamber initially occurs at the inlet nozzle, where the gaseous CO2 uses pressure as a driving force to dissolve vigorously into the particles of the growth medium. Mixing then continues based on the contact area between the collected growth medium and the pressurized CO2 within the reaction chamber. The small particles of growth medium provide additional surface area for the carbon dioxide to dissolve to form bicarbonate ions. The bicarbonate ions dissolved in the medium are consumed by the algae as carbon building blocks.

[0029] Algae accumulates at the bottom of the reaction chamber, forming algae columns. To ensure adequate mixing with the carbon dioxide, the algae columns need to fill 20% to 50% of the reaction chamber. Furthermore, the algae columns essentially prevent the carbon dioxide from escaping the valve and entering the environment. The valve opens and closes based on the pressure and level of the algae column within the reaction chamber. Algae removed from the reactor can be used in algae cultivation farms or bioreactors for the production of fuels, biochemicals, and biomass foods.

[0030] The reactor also includes at least one optical sensor to adjust the height of the algae column within the reaction chamber. In addition, a pressure regulator is positioned at the device for introducing carbon dioxide to adjust the pressure of carbon dioxide within the reaction chamber, which in turn affects the dissolution rate of carbon dioxide.

[0031] Figure 2a and 2b Experimental results are presented on the efficiency of the reactor (fed with fresh water) when carbon dioxide is dissolved into bicarbonate ions when compared to a conventional bubbling system. At carbon dioxide feed pressures below 0.25 bar, the reactor is inefficient in consuming carbon dioxide (consuming 44% more than the bubbling system). At carbon dioxide feed pressures between 0.5 and 0.7 bar, the reactor is more efficient compared to the bubbling system, consuming only 36% of the carbon dioxide to produce a similar concentration of bicarbonate ions ( Figure 2b At a CO2 feed pressure of 1 bar, the reactor was more efficient than the bubbling system, consuming only 44% of the CO2 to produce a similar concentration of bicarbonate ions.

[0032] Figure 3a and 3b Experimental results are presented on the efficiency of the reactor (with brine feed) when carbon dioxide is dissolved as bicarbonate ions when compared to a conventional bubbling system. At a carbon dioxide feed pressure of 0.5-0.7 bar, the reactor is more efficient, consuming only 39% of the carbon dioxide and producing 76% more bicarbonate ions ( Figure 3b At a CO2 feed pressure of 1 bar, the reactor was more efficient compared to the bubbling system, consuming only 53% of the CO2 to produce a similar concentration of bicarbonate ions ( Figure 3b ).

[0033] Since the algae strains were selected for freshwater, saltwater was primarily used as the growth medium, with freshwater serving as a benchmark for comparison purposes.

[0034] Compared to conventional sparger and bubbler systems, the reactor of the present invention consumes 39% to 53% of carbon dioxide and is able to substantially prevent carbon dioxide from escaping to the environment (loss < 0.02%).

Claims

1. A reactor (100) for culturing algae, comprising: means for introducing carbon dioxide (102) into a reaction chamber (104) within the reactor; an inlet nozzle (106) positioned at the top of the reactor and configured to spray a growth medium containing algae into the reaction chamber; and a valve (108) positioned at the bottom of the reactor and configured to control the outflow of algae; Characterized in that carbon dioxide dissolves in the growth medium, causing algae to grow, and the algae accumulates at the bottom of the reaction chamber to form an algae column that substantially prevents the release of carbon dioxide into the environment.

2. The reactor according to claim 1, wherein The reaction chamber is pre-filled with carbon dioxide at a pressure of at most 2 bar.

3. The reactor of claim 1, further comprising at least one optical sensor to adjust the height of the algae column within the reaction chamber.

4. The reactor according to claim 1, further comprising a pressure regulator positioned at the device for introducing carbon dioxide to adjust the pressure of carbon dioxide in the reaction chamber.

5. The reactor of claim 1 , further comprising a pump attached downstream of the inlet nozzle to pump the growth medium containing algae at a minimum flow rate to form pressurized pellets of growth medium entering the reaction chamber.

6. The reactor according to claim 1, wherein The growth medium also contains saline.

7. The reactor according to claim 1, wherein The dissolution rate of carbon dioxide into bicarbonate ions can be varied by adjusting the pressure of carbon dioxide in the reaction chamber.

8. Use of the reactor according to claim 1 for dissolving carbon dioxide in a growth medium containing algae to cultivate the algae.

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