The present invention relates to air purification. In particular, the present invention relates to a system for reducing carbon dioxide concentration in air using freshwater or marine photosynthetic microalgae. The present invention is particularly suitable for use in places of sub-tropical and temperate climates, with average temperature between 15-30° C.
Emission of greenhouse gases from vehicles and industries is one of the major causative factors for global warming and leads to temperature increase on Earth. Carbon dioxide (CO2) accounts for about 68% of the greenhouse gas emissions from human activities. CO2 sequestration by various methods has been widely studied, which aims to reduce the emission of CO2 to the atmosphere. Conventionally, CO2 in air is captured by chemical and physical technologies, such as scrubbing with aqueous amine solutions together with solvent regeneration at high temperature and physical solvent separation using high pressure. The captured CO2 is then transported to offshore geological storage (Gibbins et al., 2008).
Biological method for air purification is now being considered as a better alternative as compared to the conventional chemical and physical methods. Biological method requires milder conditions. High temperature and pressure, and environmental harmful solvents used in conventional methods are excluded in biological method. Biological method is also more sustainable. Biological method relies on photosynthesis to convert unwanted CO2 to oxygen, thus physical storage space for storing CO2 is not needed. Additional to oxygen, valuable biomass which can be used for biodiesel production, fish feed, fertilizer and chemicals which are used for health care and food products are produced during removal of CO2 by biological methods (Chisti, 2007).
However, local climate affects performance of the photobioreactor in removing carbon dioxide. Therefore, it is desired to provide a photobioreactor system which is adapted to the local climate and environment factors for efficient removal of carbon dioxide in air.
Among photosynthetic biomass organisms, freshwater microalgae are regarded to be the most suitable photosynthetic organisms for the application of air purification photobioreactor system, due to its high photosynthetic efficiency (Perrin et al., 2012).
Accordingly, the present invention provides a system for air purification specific for locations with sub-tropical to temperate climate using microalgae.
A first aspect of the present invention provides a photobioreactor system for reducing carbon dioxide in air in a location with sub-tropical to temperate climate comprises:
a reactor tank for housing a microalgae culture medium comprising Chlorella species at an initial concentration of 1,000,000-1,500,000 cells/ml at a temperature of 15-30° C.;
a gas inlet where the air enters into the system;
a gas pump, a gas pressure controller and a sparger for feeding the air to the microalgae culture medium at a flow rate of 0.1-20 L/min as small bubbles;
a temperature controller to regulate the temperature of the microalgae culture medium to the desired temperature for the operation;
a light source for providing light to the microalgae culture medium with an intensity of 50-500 μmolm−2s−1PPFD; and
a gas outlet where purified gas having a reduced carbon dioxide concentration exits the system.
In accordance with an embodiment of the presently claimed invention, the location with sub-tropical to temperate climate is Southeast Asia.
In accordance with another embodiment of the presently claimed invention, the location is Hong Kong.
In accordance with yet another embodiment of the presently claimed invention, the temperature of the microalgae culture medium is controlled at 15-30° C.
In accordance with another embodiment of the presently claimed invention, the culture medium is maintained at pH 7-9.
In accordance with another embodiment of the presently claimed invention, said light source comprises light emitting diode, fluorescence tube, sunlight or all.
A second aspect of the presently claimed invention is to provide a method for reducing carbon dioxide in air in a location with sub-tropical to temperate climate comprises:
Unlike any existing photobioreactor, the present photobioreactor system and method of air purification are adapted to sub-tropical to temperate climates for high efficient removal of carbon dioxide.
Embodiments of the present invention are described in more detail hereinafter with reference to the drawings, in which:
To illustrate the structure and advantages of the present invention, below is the detailed description of the present invention in combination with the figures and embodiments.
As shown in
The photobioreactor system further comprises a gas outlet 140 where purified air with reduced carbon dioxide exits the reactor tank. In one embodiment, the gas outlet is positioned at upper portion of the photobioreactor. The gas being treated are bubbled into the microalgae culture medium at the bottom of the reactor tank and are purified by the microalgae culture such that purified air with reduced carbon dioxide rises to the top of the reactor tank and exits through the gas outlet. The Chlorella species of the microalgae culture medium carries out photosynthesis consuming carbon dioxide in the air being treated. The microalgae culture medium converts carbon dioxide into oxygen. Thus, the air after treatment with the microalgae culture medium is purified with reduced carbon dioxide.
The photobioreactor system of the present invention further comprises a light source for providing light to the microalgae culture medium for photosynthesis. In one embodiment, the light source is in a form of a light chamber 120 of array of LEI) lights situated around the outside of the reactor tank 110. Fluorescent lamps, high-pressure sodium map, fluorescent mercury lamp, sunlamp, or sunlight may be used. In one embodiment, a light intensity of 50-500 μmolm−2s−1PPFD is supplied to the microalgae culture medium for efficient removal of carbon dioxide. In an exemplary embodiment, the array of LED lights or other light source may be situated in a position perpendicular to the orientation of the plurality of the partitions 111 such that the photosynthetic rate can be increased by maximizing the light source reaching to the microalgae culture medium inside the reactor tank 110.
The presently claimed invention also provides a method for reducing carbon dioxide in air in a location with sub-tropical to temperate climate comprises providing a photobioreactor system in accordance with the present invention, which comprises of, feeding the air into the bioreactor system, temperature controller system. The method of reducing carbon dioxide for purification of the present invention comprises maintaining the microalgae culture medium at 1,000,000-1,500,000 cells/mL at 15-30° C., adjusting the temperature of the microalgae culture medium to be the same as the desired operation temperature, feeding the incoming gas being treated into the microalgae culture medium at 0.1 to 2.0 L/min, enabling purified gas having reduced concentration of carbon dioxide than the incoming gas to exit the photobioreactor system and optionally collecting any biomass produced during photosynthesis of the microalgae culture medium.
The presently claimed invention also provides a method for reducing carbon dioxide in air in a location with sub-tropical to temperate climate comprises providing a photobioreactor system in accordance with the present invention, which comprises of, feeding the air into the bioreactor system, dispersing the air evenly into the bioreactor system. The method of reducing carbon dioxide for purification of the present invention comprises maintaining the microalgae culture medium at 1,000,000-1,500,000 cells/mL, feeding the incoming gas being treated into the microalgae culture medium at 1 to 20 L/min, enabling purified gas having reduced concentration of carbon dioxide than the incoming gas to exit the photobioreactor system and optionally collecting any biomass produced during photosynthesis of the microalgae culture medium.
The present photobioreactor system demonstrates highly efficient carbon dioxide purification in locations with sub-tropical to temperate climate. The microalgae species, culture density, temperature, flow rate and light intensity are selected for high efficiency carbon dioxide purification in locations with sub-tropical to temperate climates. The locations have hot, humid summers and generally mild winters. In particular, the location has a mean monthly temperature between 15° C. and 30° C. The present photobioreactor system is designed for high efficiency carbon dioxide purification in Southeast Asia. The present photobioreactor system is designed for high efficiency carbon dioxide purification in Hong Kong or location with similar climate.
Three examples are given below to demonstrate the operation of the present invention for air purification in Hong Kong using microalgae which can significantly reduce the CO2 concentration in air.
Purification of CO2 polluted air using the present invention as shown in
Purification of CO2 polluted air using the present invention as shown in
Purification of CO2 polluted air using the present invention as shown in
The foregoing description of the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations will be apparent to the practitioner skilled in the art.
The embodiments were chosen and described in order to best explain the principles of the invention and its practical application, thereby enabling others skilled in the art to understand the invention for various embodiments and with various modifications that are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalence.
Bristol A, Bristol B, Bristol C solution is diluted 100 fold to working volume
Trace 1, Trace 2, Trace 3, Trace 4 solution is diluted 1000 fold, to working volume
Pursuant to 35 U.S.C. §119(e), this is a non-provisional patent application claiming benefit from U.S. provisional patent application Ser. No. 62/124,348 filed Dec. 16, 2014 and titled “Photobioreactor design for indoor and outdoor air purifications in Hong Kong using microalgae”, and the disclosure of which is incorporated herein by reference in its entirety.
Number | Date | Country | |
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62124348 | Dec 2014 | US |