Process for Managing Photobioreactor Exhaust

There is provided a process for growing a phototrophic biomass in a reaction zone, wherein the reaction zone includes a reaction mixture that is operative for effecting photosynthesis upon exposure to photosynthetically active light radiation, wherein the reaction mixture includes phototrophic biomass that is operative for growth within the reaction zone. The process includes supplying at least a fraction of gaseous exhaust material, being discharged from an industrial process, to the reaction zone, exposing the reaction mixture to photosynthetically active light radiation and effecting growth of the phototrophic biomass in the reaction zone, wherein the effected growth includes growth effected by photosynthesis, and modulating distribution of a molar rate of supply of carbon dioxide, being exhausted from the reaction zone, as between a smokestack and at least another point of discharge.

DETAILED DESCRIPTION

Reference throughout the specification to “some embodiments” means that a particular feature, structure, or characteristic described in connection with some embodiments are not necessarily referring to the same embodiments. Furthermore, the particular features, structure, or characteristics may be combined in any suitable manner with one another.

Referring toFIG. 1, a system is provided for facilitating a process of growing a phototrophic biomass within a reaction zone10of a photobioreactor12.

The reaction zone10includes a reaction mixture that is operative for effecting photosynthesis upon exposure to photosynthetically active light radiation. The reaction mixture includes phototrophic biomass, carbon dioxide, and water. In some embodiments, the reaction zone includes phototrophic biomass and carbon dioxide disposed in an aqueous medium. Within the reaction zone10, the phototrophic biomass is disposed in mass transfer communication with both of carbon dioxide and water.

“Phototrophic organism” is an organism capable of phototrophic growth in the aqueous medium upon receiving light energy, such as plant cells and micro-organisms. The phototrophic organism is unicellular or multicellular. In some embodiments, for example, the phototrophic organism is an organism which has been modified artificially or by gene manipulation. In some embodiments, for example, the phototrophic organism is an algae. In some embodiments, for example, the algae is micro algae.

“Phototrophic biomass” is at least one phototrophic organism. In some embodiments, for example, the phototrophic biomass includes more than one species of phototrophic organisms.

“Reaction zone10” defines a space within which the growing of the phototrophic biomass is effected. In some embodiments, for example, pressure within the reaction zone is atmospheric pressure.

“Photobioreactor12” is any structure, arrangement, land formation or area that provides a suitable environment for the growth of phototrophic biomass. Examples of specific structures which can be used is a photobioreactor12by providing space for growth of phototrophic biomass using light energy include, without limitation, tanks, ponds, troughs, ditches, pools, pipes, tubes, canals, and channels. Such photobioreactors may be either open, closed, partially closed, covered, or partially covered. In some embodiments, for example, the photobioreactor12is a pond, and the pond is open, in which case the pond is susceptible to uncontrolled receiving of materials and light energy from the immediate environments. In other embodiments, for example, the photobioreactor12is a covered pond or a partially covered pond, in which case the receiving of materials from the immediate environment is at least partially interfered with. The photobioreactor12includes the reaction zone10which includes the reaction mixture. In some embodiments, the photobioreactor12is configured to receive a supply of phototrophic reagents (and, in some of these embodiments, optionally, supplemental nutrients), and is also configured to effect discharge of phototrophic biomass which is grown within the reaction zone10. In this respect, in some embodiments, the photobioreactor12includes one or more inlets for receiving the supply of phototrophic reagents and supplemental nutrients, and also includes one or more outlets for effecting the recovery or harvesting of biomass which is grown within the reaction zone10. In some embodiments, for example, one or more of the inlets are configured to be temporarily sealed for periodic or intermittent time intervals. In some embodiments, for example, one or more of the outlets are configured to be temporarily sealed or substantially sealed for periodic or intermittent time intervals. The photobioreactor12is configured to contain the reaction mixture which is operative for effecting photosynthesis upon exposure to photosynthetically active light radiation. The photobioreactor12is also configured so as to establish photosynthetically active light radiation (for example, a light of a wavelength between about 400-700 nm, which can be emitted by the sun or another light source) within the photobioreactor12for exposing the phototrophic biomass. The exposing of the reaction mixture to the photosynthetically active light radiation effects photosynthesis and growth of the phototrophic biomass. In some embodiments, for example, the established light radiation is provided by an artificial light source14disposed within the photobioreactor12. For example, suitable artificial lights sources include submersible fiber optics or light guides, light-emitting diodes (“LEDs”), LED strips and fluorescent lights. Any LED strips known in the art can be adapted for use in the photobioreactor12. In the case of the submersible LEDs, in some embodiments, for example, energy sources include alternative energy sources, such as wind, photovoltaic cells, fuel cells, etc. to supply electricity to the LEDs. Fluorescent lights, external or internal to the photobioreactor12, can be used as a back-up system. In some embodiments, for example, the established light is derived from a natural light source16which has been transmitted from externally of the photobioreactor12and through a transmission component. In some embodiments, for example, the transmission component is a portion of a containment structure of the photobioreactor12which is at least partially transparent to the photosynthetically active light radiation, and which is configured to provide for transmission of such light to the reaction zone10for receiving by the phototrophic biomass. In some embodiments, for example, natural light is received by a solar collector, filtered with selective wavelength filters, and then transmitted to the reaction zone10with fiber optic material or with a light guide. In some embodiments, for example, both natural and artificial lights sources are provided for effecting establishment of the photosyntetically active light radiation within the photobioreactor12.

“Aqueous medium” is an environment that includes water. In some embodiments, for example, the aqueous medium also includes sufficient nutrients to facilitate viability and growth of the phototrophic biomass. In some embodiments, for example, supplemental nutrients may be included such as one of, or both of, NOXand SOX. Suitable aqueous media are discussed in detail in: Rogers, L. J. and Gallon J. R. “Biochemistry of the Algae and Cyanobacteria,” Clarendon Press Oxford, 1988; Burlew, John S. “Algal Culture: From Laboratory to Pilot Plant.” Carnegie Institution of Washington Publication 600. Washington, D.C., 1961 (hereinafter “Burlew 1961”); and Round, F. E. The Biology of the Algae. St Martin's Press, New York, 1965; each of which is incorporated herein by reference). A suitable supplemental nutrient composition, known as “Bold's Basal Medium”, is described in Bold, H.C. 1949,The morphology of Chlamydomonas chlamydogama sp. nov. Bull. Torrey Bot. Club.76: 101-8 (see also Bischoff, W. and Bold, H.C. 1963,Phycological Studies IV. Some soil algae from Enchanted Rock and related algal species. Univ. Texas Publ. 6318: 1-95, and Stein, J. (ED.)Handbook of Phycological Process, Culture process and growth measurements, Cambridge University Press, pp. 7-24).

“Headspace” is that space within the photobioreactor12that is above the aqueous medium within the photobioreactor12.

Carbon dioxide is supplied to the reaction zone10of the photobioreactor12for effecting the growth of the phototrophic biomass. In some embodiments, for example, the carbon dioxide being supplied to the photobioreactor is supplied by at least a fraction of the carbon dioxide-comprising exhaust material14being discharged by a carbon dioxide-comprising gaseous exhaust material producing process16. The at least a fraction of the carbon dioxide-comprising exhaust material14, that is being supplied to the photobioreactor12, defines the photobioreactor supply122.

In some embodiments, for example, the carbon dioxide-comprising gaseous exhaust material14includes a carbon dioxide concentration of at least two (2) volume % based on the total volume of the carbon dioxide-comprising gaseous exhaust material14. In some embodiments, for example, the carbon dioxide-comprising gaseous exhaust material14includes a carbon dioxide concentration of at least four (4) volume % based on the total volume of the carbon dioxide-comprising gaseous exhaust material14. In some embodiments, for example, the gaseous exhaust material reaction14also includes one or more of N2, CO2, H2O, O2, NOx, S0x, CO, volatile organic compounds (such as those from unconsumed fuels) heavy metals, particulate matter, and ash. In some embodiments, for example, the carbon dioxide-comprising gaseous exhaust material14includes 30 to 60 volume % N2, 5 to 25 volume % O2, 2 to 50 volume % CO2, and 0 to 30 volume % H2O, based on the total volume of the carbon dioxide-comprising gaseous exhaust material14. Other compounds may also be present, but usually in trace amounts (cumulatively, usually less than five (5) volume % based on the total volume of the carbon dioxide-comprising gaseous exhaust material14).

In some embodiments, for example, the carbon dioxide-comprising gaseous exhaust material14includes one or more other materials, other than carbon dioxide, that are beneficial to the growth of the phototrophic biomass within the reaction zone10. Materials within the gaseous exhaust material which are beneficial to the growth of the phototrophic biomass within the reaction zone10include SOX, NOX, and NH3.

The carbon dioxide-comprising gaseous exhaust material producing process16includes any process which effects production and discharge of the carbon dioxide-comprising gaseous exhaust material14. In some embodiments, for example, the carbon dioxide-comprising gaseous exhaust material producing process16is a combustion process. In some embodiments, for example, the combustion process is effected in a combustion facility. In some of these embodiments, for example, the combustion process effects combustion of a fossil fuel, such as coal, oil, or natural gas. For example, the combustion facility is any one of a fossil fuel-fired power plant, an industrial incineration facility, an industrial furnace, an industrial heater, or an internal combustion engine. In some embodiments, for example, the combustion facility is a cement kiln.

In some embodiments, for example, a supplemental nutrient supply18is supplied to the reaction zone10of the photobioreactor12. In some embodiments, for example, the supplemental nutrient supply18is effected by a pump, such as a dosing pump. In other embodiments, for example, the supplemental nutrient supply18is supplied manually to the reaction zone10. Nutrients within the reaction zone10are processed or consumed by the phototrophic biomass, and it is desirable, in some circumstances, to replenish the processed or consumed nutrients. A suitable nutrient composition is “Bold's Basal Medium”, and this is described in Bold, H.C. 1949, The morphology of Chlamydomonas chlamydogama sp. nov. Bull. Torrey Bot. Club.76: 101-8 (see also Bischoff, H. W. and Bold, H. C. 1963,Phycological Studies IV. Some soil algae from Enchanted Rock and related algal species, Univ. Texas Publ. 6318: 1-95, and Stein, J. (ED.)Handbook of Phycological Processs, Culture process and growth measurements, Cambridge University Press, pp. 7-24). The supplemental nutrient supply18is supplied for supplementing the nutrients provided within the reaction zone, such as “Bold's Basal Medium”, or one or more dissolved components thereof. In this respect, in some embodiments, for example, the supplemental nutrient supply18includes “Bold's Basal Medium”. In some embodiments for example, the supplemental nutrient supply18includes one or more dissolved components of “Bold's Basal Medium”, such as NaNO3, CaCl2, MgSO4, KH2PO4, NaCl, or other ones of its constituent dissolved components.

In some embodiments, for example, the rate of supply of the supplemental nutrient supply18to the reaction zone10is controlled to align with a desired rate of growth of the phototrophic biomass in the reaction zone10. In some embodiments, for example, regulation of nutrient addition is monitored by measuring any combination of pH, NO3concentration, and conductivity in the reaction zone10.

In some embodiments, for example, a supply of the supplemental aqueous material supply20is effected to the reaction zone10of the photobioreactor12, so as to replenish water within the reaction zone10of the photobioreactor12. In some embodiments, for example, and as further described below, the supplemental aqueous material supply20effects the discharge of product from the photobioreactor12by displacement. For example, the supplemental aqueous material supply20effects the discharge of product from the photobioreactor12as an overflow.

In some embodiments, for example, the supplemental aqueous material is water or substantially water. In some embodiments, for example, the supplemental aqueous material supply20includes aqueous material that has been separated from a discharged phototrophic biomass-comprising product32by a separator50(such as a centrifugal separator). In some embodiments, for example, the supplemental aqueous material supply20is derived from an independent source (i.e. a source other than the process), such as a municipal water supply.

In some embodiments, for example, the supplemental aqueous material supply20is supplied from a container that has collected aqueous material recovered from discharges from the process, such as aqueous material that has been separated from a discharged phototrophic biomass-comprising product.

In some embodiments, for example, the supplemental nutrient supply18is mixed with the supplemental aqueous material20in a mixing tank24to provide a nutrient-enriched supplemental aqueous material supply22, and the nutrient-enriched supplemental aqueous material supply22is supplied to the reaction zone10. In some embodiments, for example, the supplemental nutrient supply18is mixed with the supplemental aqueous material20within the container which has collected the discharged aqueous material. In some embodiments, for example, the supply of the nutrient-enriched supplemental aqueous material supply18is effected by a pump.

The reaction mixture disposed in the reaction zone10is exposed to photosynthetically active light radiation so as to effect photosynthesis. The photosynthesis effects growth of the phototrophic biomass.

In some embodiments, for example, light radiation is supplied to the reaction zone10for effecting the photosynthesis.

In some embodiments, for example, the light radiation is characterized by a wavelength of between 400-700 nm. In some embodiments, for example, the light radiation is in the form of natural sunlight. In some embodiments, for example, the light radiation is provided by an artificial light source. In some embodiments, for example, light radiation includes natural sunlight and artificial light.

In some embodiments, for example, the intensity of the supplied light radiation is controlled so as to align with the desired growth rate of the phototrophic biomass in the reaction zone10. In some embodiments, regulation of the intensity of the provided light is based on measurements of the growth rate of the phototrophic biomass in the reaction zone10. In some embodiments, regulation of the intensity of the provided light is based on the molar rate of supply of carbon dioxide to the reaction zone feed material80.

In some embodiments, for example, the light radiation is supplied at pre-determined wavelengths, depending on the conditions of the reaction zone10. Having said that, generally, the light is provided in a blue light source to red light source ratio of 1:4. This ratio varies depending on the phototrophic organism being used. As well, this ratio may vary when attempting to simulate daily cycles. For example, to simulate dawn or dusk, more red light is provided, and to simulate mid-day condition, more blue light is provided. Further, this ratio may be varied to simulate artificial recovery cycles by providing more blue light.

It has been found that blue light stimulates algae cells to rebuild internal structures that may become damaged after a period of significant growth, while red light promotes algae growth. Also, it has been found that omitting green light from the spectrum allows algae to continue growing in the reaction zone10even beyond what has previously been identified as its “saturation point” in water, so long as sufficient carbon dioxide and, in some embodiments, other nutrients, are supplied.

With respect to artificial light sources, for example, suitable artificial light source14include submersible fiber optics, light-emitting diodes, LED strips and fluorescent lights. Any LED strips known in the art can be adapted for use in the process. In the case of the submersible LEDs, the design includes the use of solar powered batteries to supply the electricity. In the case of the submersible LEDs, in some embodiments, for example, energy sources include alternative energy sources, such as wind, photovoltaic cells, fuel cells, etc. to supply electricity to the LEDs.

With respect to those embodiments where the reaction zone10is disposed in a photobioreactor12which includes a tank, in some of these embodiments, for example, the light energy is provided from a combination of sources, as follows. Natural light source in the form of solar light is captured though solar collectors and filtered with custom mirrors that effect the provision of light of desired wavelengths to the reaction zone10. The filtered light from the solar collectors is then transmitted through light guides or fiber optic materials into the photobioreactor12, where it becomes dispersed within the reaction zone10. In some embodiments, in addition to solar light, the light tubes in the photobioreactor12contains high power LED arrays that can provide light at specific wavelengths to either complement solar light, as necessary, or to provide all of the necessary light to the reaction zone10during periods of darkness (for example, at night). In some embodiments, with respect to the light guides, for example, a transparent heat transfer medium (such as a glycol solution) is circulated through light guides within the photobioreactor12so as to regulate the temperature in the light guides and, in some circumstances, provide for the controlled dissipation of heat from the light guides and into the reaction zone10. In some embodiments, for example, the LED power requirements can be predicted and, therefore, controlled, based on trends observed with respect to the carbon dioxide-comprising gaseous exhaust material14, as these observed trends assist in predicting future growth rate of the phototrophic biomass.

In some embodiments, the exposing of the reaction mixture to photosynthetically active light radiation is effected while the supplying of the carbon dioxide to the reaction zone10is being effected.

In some embodiments, for example, the growth rate of the phototrophic biomass is dictated by the available carbon dioxide within the reaction zone10. In turn, this defines the nutrient, water, and light intensity requirements to maximize phototrophic biomass growth rate. In some embodiments, for example, a controller, e.g. a computer-implemented system, is provided to be used to monitor and control the operation of the various components of the process disclosed herein, including lights, valves, sensors, blowers, fans, dampers, pumps, etc.

In some embodiments, for example, reaction zone product30is discharged from the reaction zone10. The reaction zone product30includes phototrophic biomass-comprising product32. In some embodiments, for example, the phototrophic biomass-comprising product32includes at least a fraction of the contents of the reaction zone10. In this respect, the discharge of the reaction zone product30effects harvesting of the phototrophic biomass40.

In some embodiments, for example, the harvesting of the phototrophic biomass is effected by discharging the phototrophic biomass32from the reaction zone10.

In some embodiments, for example, the discharging of the phototrophic biomass32from the reaction zone10is effected by displacement. In some of these embodiments, for example, the displacement is effected by supplying supplemental aqueous material supply20to the reaction zone10. In some of these embodiments, for example, the displacement is an overflow. In some embodiments, for example, the discharging of the phototrophic biomass32from the reaction zone10is effected by gravity. In some embodiments, for example, the discharging of the phototrophic biomass32from the reaction zone10is effected by a prime mover that is fluidly coupled to the reaction zone10.

In some embodiments, for example, the at least a fraction of carbon dioxide-comprising gaseous exhaust material14is passed through the reaction zone10for effecting the photosynthesis such that the carbon dioxide-comprising gaseous exhaust material14becomes depleted in carbon dioxide, and such that production of a gaseous photobioreactor exhaust60, including photobioreactor-exhausted carbon dioxide, is effected and exhausted into the headspace13. In some embodiments, for example, the carbon dioxide concentration within the gaseous photobioreactor exhaust60is less than the carbon dioxide concentration within the carbon dioxide-comprising gaseous exhaust material14.

In some embodiments, for example, at least a fraction of the carbon dioxide-comprising gaseous exhaust material14is supplied to a gas treatment process100, as pre-treated gaseous exhaust material141to generate a treated gaseous exhaust material142. The gas treatment process100includes one or more separate unit operations for effecting separation of at least a fraction of the pre-treated gaseous exhaust material141to yield treated gaseous exhaust material142. Exemplary unit operations include bag houses, NOXfilters, SOXfilters, electrostatic fluidized beds, membrane separation unit operations (such as for effecting separation of gaseous diatomic oxygen from the pre-treated material141).

In some embodiments, for example, at least a fraction of the treated material142is supplied as the photobioreactor supply122.

In some embodiments, for example, at least a fraction of the treated material142is supplied to the smokestack200. In some embodiments, for example, a fraction of the treated material142is supplied to the smokestack200as a smokestack supply201, while another fraction of the treated material142is supplied to the photobioreactor12as the photobioreactor supply122. In some embodiments, for example, the fraction supplied as the smokestack supply201, and the fraction supplied as the photobioreactor supply122, is determined by a damper or stack cap202within the smokestack. The damper or stack cap202is biased (such as by spring forces) to seal fluid communication between the treated material142and the smokestack such that all of the treated material142is supplied to the reaction zone10of the photobioreactor12. The damper or stack cap202is configured to become disposed so as to effect fluid communication between the treated material and the smokestack when the fluid pressure of the treated material is sufficient to overcome the forces biasing the damper or stack cap to be disposed in a condition to effect the sealing of the fluid communication, and thereby effect opening of the fluid communication, thereby diverting a fraction of the treated material to the smokestack200

In some embodiments, for example, there is no gas treatment process100, and at least a fraction of the exhaust material14is supplied directly to the smokestack200as a smokestack supply. In some of these embodiments, for example, a fraction of the exhaust material14is supplied to the smokestack200as the smokestack supply201, while another fraction of the exhaust material14is supplied to the photobioreactor12as the photobioreactor supply122. In some embodiments, for example, the fraction supplied as the smokestack supply201, and the fraction supplied as the photobioreactor supply122, is determined by a damper or stack cap202within the smokestack, as described above.

The photobioreactor exhaust60is discharged from the photobioreactor12.

The rate of discharging of the exhaust60is modulated as between a local discharge61and a further processing discharge62by a valve1200, based on sensed concentrations of various gases, such as carbon dioxide, diatomic oxygen, NOX, and SOX. It is desirable for exhaust60having excessive carbon dioxide, NOX, or SOXconcentrations not to be exhausted, locally, at ground level, and to direct such exhaust60for recycling within the process, or to the smokestack200, or to a cold stack300. Depending on the configuration of the system, sensed gaseous diatomic oxygen may determine whether to recycle the exhaust (for example, if gaseous diatomic oxygen concentration is below a minimum threshold for effecting combustion of fuel) or to conduct the exhaust to the process16(for example, if gaseous diatomic oxygen concentration is sufficient for effecting combustion of fuel), or a combination of both. Sensing of excessive concentrations of one or more of these gases will initiate or increase the rate of supply of exhaust60to the further processing discharge62, and may, in some modes of operation, suspend the local discharge61.

Referring toFIGS. 1,2A and2B, in some embodiments, for example, the gas treatment process100includes one or more membrane separation unit operations (or other gas separation unit operations, such as one or more gas absorbers) for effecting separation of an oxygen-rich stream from the stream601deriving from the exhaust60, and delivery of a gas, of a sufficient gaseous diatomic oxygen concentration to effect combustion of a fuel, to the industrial process16, for effecting the combustion of a fuel. In some embodiments, for example, the stream601is indirectly heated by at least a fraction of the gaseous exhaust material14. The heating of the stream601increases the internal energy of the stream601, including that of the oxygen-rich stream that is separated from the stream601, such that the combustion of the fuel, effected by contacting of the oxygen-rich stream with a fuel, is enhanced by virtue of the heating of the oxygen-rich stream. As well, the indirect heating effects cooling of the carbon dioxide-comprising gaseous exhaust material14, such that the deleterious effect on the phototrophic biomass, effected by exposure of the phototrophic biomass to high temperatures, is mitigated. In some embodiments, for example, the indirect heating is effected within a heat exchanger900be effecting disposition of the stream601in indirect heat transfer communication with the at least a fraction of the gaseous exhaust material14.

Referring toFIG. 2A, in some embodiments, for example, the gas treatment process100includes a single membrane separation unit operation.101for effecting enrichment of gaseous diatomic oxygen. The unit operation101receives a stream601of the exhaust60(or a post-treatment stream that is derived from the stream601, after the stream601has been subjected to pre-treatment by another unit operation within process100) to effect separation of an oxygen-rich stream612and an oxygen-depleted stream614from the stream601. Relative to the oxygen-depleted stream614, the oxygen-rich stream612is rich in oxygen and nitrogen and any other relatively smaller molecules (e.g. mercury). Relative to the oxygen-rich stream612, the oxygen-depleted stream614is rich in carbon dioxide, NOX, SOX, volatile organic compounds, and other relatively larger molecules. The supply of the oxygen-rich stream612, as between the process16and the smokestack200, is modulated by a valve6003, in response to a sensed gaseous diatomic oxygen concentration within the stream612. For a sensed gaseous diatomic oxygen concentration that is sufficient to effect combustion of fuel, the supply of the stream612, as a stream622, to the process16is initiated, or the molar rate of supply of the stream612, as the stream622, to the process16increased. For a sensed gaseous diatomic oxygen concentration that is below that which is sufficient to effect combustion of fuel, the supply of the stream612, as a stream624, to the smokestack200is initiated, or the molar rate of supply of the stream612, as the stream624, to the smokestack200is increased. The oxygen-depleted stream614, which is rich in carbon dioxide, NOX, SOX, volatile organic compounds, and other relatively larger molecules, is conducted as at least a fraction of the treated material142, and at least a fraction of the treated material142is supplied to the reaction zone10. In this respect, at least a fraction of the oxygen-depleted stream614, being rich in nutrients for encouraging growth of phototropic biomass, is supplied to the photobioreactor12, and is depleted in gaseous diatomic oxygen, which is detrimental to growth of phototrophic biomass within the reaction zone10. The removal of material (including gaseous diatomic oxygen) from the stream601also eliminates the need for larger gas handling equipment, which would have been required if the material is not removed from the steam614before it is recycled to the reaction zone10of the photobioreactor12.

Referring toFIG. 2B, in some embodiments, for example, the gas treatment process100includes two membrane separation unit operations101,102, disposed in series for effecting a two-stage enrichment of gaseous diatomic oxygen. The unit operation101receives the stream601(or a post-treatment stream that is derived from the stream601, after the stream601has been subjected to pre-treatment by another unit operation within process100) to effect separation of an oxygen-rich stream612and an oxygen-depleted stream614from the stream611. Relative to the oxygen-depleted stream614, the oxygen-rich stream612is rich in oxygen and nitrogen and any other relatively smaller molecules (e.g. mercury). Relative to the oxygen-rich stream612, the /oxygen-depleted stream614is rich in carbon dioxide, NOX, SOX, volatile organic compounds, and other relatively larger molecules. The oxygen-rich stream612is supplied to the membrane separation unit operation201and is separated into a further oxygen-enriched stream622and a nitrogen-enriched stream624. The further oxygen-enriched stream622is supplied to the industrial process16, and the nitrogen-rich stream624is supplied to the smokestack200. The oxygen-depleted stream614, which is rich in carbon dioxide, NOX, SOX, volatile organic compounds, and other relatively larger molecules, is conducted as at least a fraction of the treated material142, and at least a fraction of the treated material142is supplied to the reaction zone10of the photobioreactor12. In this respect, at least a fraction of the oxygen-depleted stream614, being rich in nutrients for encouraging growth of phototropic biomass, is supplied to the photobioreactor12, and is depleted in gaseous diatomic oxygen, which is detrimental to growth of phototrophic biomass within the reaction zone10. The removal of material (including gaseous diatomic oxygen) from the stream601also eliminates the need for larger gas handling equipment, which would have been required if the material is not removed from the steam614before it is recycled to the reaction zone10of the photobioreactor12.

Referring toFIG. 3, in some embodiments, for example, the gas treatment process100is not configured for effecting enrichment of gaseous diatomic oxygen, such that at least a fraction of the exhaust60is supplied to the process16in response to sensing of a concentration of gaseous diatomic oxygen that is sufficient to effect combustion of a fuel. In this respect, in some embodiments, for example, a valve6005is provided to modulate supply of the stream601, as between the process16and as a recycle stream to the photobioreactor10. In this respect, in response to the sensing of a gaseous diatomic oxygen concentration that is sufficient to effect combustion of a fuel, supply of the stream601, as a stream632, to the process16, is initiated, or a molar rate of supply of the stream601, as a stream632, to the process16, is increased. In parallel, the supply of the stream601, as a stream634, to the treated exhaust142, is suspended, or the molar rate of supply of the stream601, as a stream634, to the treated exhaust142, is decreased. Conversely, in response to the sensing of a gaseous diatomic oxygen concentration that is lower than that sufficient to effect combustion of a fuel, the supply of the stream601, as a stream632, to the process16, is suspended, or the molar rate of supply of the stream601, as a stream632, to the process16, is decreased. In parallel, the supply of the stream601, as a stream634, to the treated exhaust142, is initiated, or the molar rate of supply of the stream601, as a stream634, to the treated exhaust142, is increased.

Referring toFIGS. 1 and 3, in some embodiments, for example, and during upset conditions, at least a fraction of the exhaust60is conducted to the smokestack200, or to a cold stack300, so as to effect its discharge into the environment at an elevation above ground level. The smokestack200may be a pre-existing smokestack that had been previously receiving at least a fraction of the exhaust14from the process16prior to commissioning of the photobioreactor12, or which is currently receiving a fraction of the exhaust14from the process16, such as while a fraction of the exhaust14is being supplied to the photobioreactor12as the photobioreactor supply122. If, however, the smokestack200is remote from the photobioreactor12, a cold stack300, local to the photobioreactor12, may be provided to provide the same functionality as the smokestack200, without the added infrastructure and expense of having to conduct the exhaust60, over long distances, to a remote smokestack200. Under normal operating conditions, the exhaust60is not discharged to a smokestack200or a cold stack300, but is substantially retained within the system, as described above, unless the sensed concentration of the gas components being sensed are sufficiently low such that local discharge is permissible and is effected through the valve1200. However, under upset conditions, such as when gas handling equipment fails, or when growth of the phototrophic biomass is suspended, it may not desirable to discharge at least a fraction of the exhaust60as the further processing discharge62for further downstream processing, as described above. In this situation, a valve6007is provided for modulating the rate of supply of at least a fraction of the discharge62, as a stream642, to the smokestack200, and may become disposed to effect fluid communication between the reaction zone10and the smokestack200, when . upset conditions are sensed and a sensed gas concentration (for example, carbon dioxide concentration) exceeds a predetermined threshold. Similarly, a valve6009is provided for modulating the rate of supply of the discharge62, as a stream652to the coldstack300, and may become disposed to effect fluid communication between the reaction zone10and the smokestack300, when upset conditions are sensed and a sensed gas concentration (for example, carbon dioxide concentration) exceeds a predetermined threshold.

Referring toFIG. 4, in some embodiments, for example, the process includes modulating distribution of a molar rate of supply of carbon dioxide, being exhausted from the photobioreactor (i.e. photobioreactor-exhausted carbon dioxide62), as between a smokestack200and at least another point of discharge800. The at least another point of discharge can include a point of discharge for supplying the exhausted carbon dioxide62as part of the photobioreactor exhaust60to any one of the reprocessing operations described above. The at least another point of discharge800can also be a discharge into the local environment, such as at ground level.

Modulating includes any one of: (a) initiating the supply of the photobioreactor-exhausted carbon dioxide to the smokestack200, (b) suspending the supply of the photobioreactor-exhausted carbon dioxide to the smokestack200, (c) increasing the molar rate of supply of the photobioreactor-exhausted carbon dioxide to the smokestack200, or (d) decreasing the molar rate of supply of the photobioreactor-exhausted carbon dioxide to the smokestack200. By initiating the supply of the photobioreactor-exhausted carbon dioxide to the smokestack200, or increasing the molar rate of supply of the photobioreactor-exhausted carbon dioxide to the smokestack200, either the supply of the photobioreactor-exhausted carbon dioxide to the at least another point of discharge is suspended, or the molar rate of supply of the photobioreactor-exhausted carbon dioxide to the at least another point of discharge is decreased. By suspending the supply of the photobioreactor-exhausted carbon dioxide to the smokestack200, or increasing the molar rate of supply of the photobioreactor-exhausted carbon dioxide to the smokestack200, either the supply of the photobioreactor-exhausted carbon dioxide to the at least another point of discharge is initiated, or the molar rate of supply of the photobioreactor-exhausted carbon dioxide to the at least another point of discharge is increased.

In some embodiments, for example, a fraction of the carbon dioxide-comprising exhaust material14, being discharged by a carbon dioxide-comprising gaseous exhaust material producing process16, is being supplied to the smokestack200while another fraction of the carbon dioxide-comprising exhaust material14is being supplied to the reaction zone10. In this respect, the at least a fraction of carbon dioxide-comprising gaseous exhaust material14being supplied to the reaction zone10is less than the entirety, or the substantial entirety, of the carbon dioxide gaseous exhaust material14being discharged by the carbon dioxide-comprising gaseous exhaust material producing process16.

In some embodiments, for example, the modulating is effected based on an indication of the molar rate at which carbon dioxide is being exhausted from the photobioreactor12. In some embodiments, for example, the indication is a sensed indication. In some of these embodiments, for example, the sensed indication includes a sensed carbon dioxide concentration of the carbon dioxide-comprising gaseous exhaust material14, or a sensed carbon dioxide concentration of the gaseous photobioreactor exhaust60, or a sensed molar rate of carbon dioxide being discharged from the photobioreactor12. The sensing of carbon dioxide concentration can be effected by a carbon dioxide sensor. The sensing of molar rate of carbon dioxide being exhausted from the photobioreactor12can be effected with the combination of a flow sensor and a carbon dioxide sensor.

In some embodiments, for example, the modulating is initiating the supply, or increasing the molar rate of supply, of the photobioreactor-exhausted carbon dioxide to the smokestack200, and the modulating is effected in response to the sensing of either one of (i) an indication of a carbon dioxide concentration of the gaseous photobioreactor exhaust60that exceeds a predetermined concentration, or (ii) an indication of a carbon dioxide concentration of the gaseous exhaust material14that exceeds a predetermined concentration. The predetermined concentration being one that represents a threshold carbon dioxide concentration, above which the photobioreactor-exhausted carbon dioxide should be supplied to the smokestack200for purposes of environmental abatement. In this respect, a carbon dioxide sensor senses the carbon dioxide concentration and sends a signal representative of the sensed carbon dioxide concentration to a controller, the controller compares the received signal to a set point representative of the predetermined concentration, determines that the sensed carbon dioxide concentration exceeds the predetermined concentration, and transmits a signal to a flow control device1200, disposed between the photobioreactor12and the smokestack200for selectively interfering with fluid communication between the photobioreactor12and the smokestack100, to effect initiation of supply of, or an increase in the molar rate of supply of, the photobioreactor-exhausted carbon dioxide to the smokestack200.

In some embodiments, for example the modulating is initiating the supply, or increasing the molar rate of supply, of the photobioreactor-exhausted carbon dioxide to the smokestack200, and the modulating is effected in response to the sensing of a molar rate of discharge of carbon dioxide from the photobioreactor12that exceeds a predetermined molar flow rate. The predetermined molar flow rate being one that represents a threshold molar flow rate, above which the photobioreactor-exhausted carbon dioxide should be supplied to the smokestack200for purposes of environmental abatement. In this respect, a carbon dioxide sensor senses the carbon dioxide concentration of the discharged photobioreactor exhaust60and sends a signal representative of the sensed carbon dioxide concentration to a controller, and, in parallel, a flow sensor sense the molar rate of flow of photobioreactor exhaust60being discharged from the photobioreactor and send a signal of the sensed molar flow rate to the controller. The controller receives the signals and generates a value representative of the molar rate of carbon dioxide being discharged from the photobioreactor12and compares the generated value to a set point representative of a predetermined molar flow rate, determines that the generated value representative of the molar rate of carbon dioxide being discharged from the photobioreactor12exceeds the predetermined molar flow rate, and transmits a signal to a flow control device1200, disposed between the photobioreactor12and the smokestack200for selectively interfering with fluid communication between the photobioreactor12and the smokestack200, to effect initiation of supply of, or an increase in the molar rate of supply of, the photobioreactor-exhausted carbon dioxide to the smokestack200.

In some embodiments, for example, the photobioreactor-exhausted carbon dioxide62is indirectly heated by at least a fraction of the carbon dioxide-comprising gaseous exhaust material14being supplied to the reaction zone10, such that an increase in temperature to the exhausted carbon dioxide62is effected such that the chimney effect is enhanced within the smokestack (or cold stack300) upon the receiving of the exhausted carbon dioxide62. As well, the indirect heating effects cooling of the carbon dioxide-comprising gaseous exhaust material14, such that the deleterious effect on the phototrophic biomass, effected by exposure of the phototrophic biomass to high temperatures, is mitigated. In some embodiments, for example, the indirect heating is effected within a heat exchanger901be effecting disposition of the exhausted carbon dioxide62in indirect heat transfer communication with the at least a fraction of the gaseous exhaust material14.

In some embodiments, for example, the photobioreactor-exhausted carbon dioxide62is indirectly heated using low grade heat from industrial processes, or with solar radiation (such as that portion of the solar radiation which is rejected and not used for effecting photosynthesis within the reaction zone10). This heating of the exhausted carbon dioxide effects an increase in temperature to the exhausted carbon dioxide62such that the chimney effect is enhanced within the smokestack (or cold stack300) upon the receiving of the exhausted carbon dioxide62.

The systems illustrated inFIGS. 1,2A,2B,3and4may include a controller and various sensors to effect desired control over the valves and, therefore, the transport or conduction of the materials. As well, various flowmetres may be provided to verify that desired fluid transport is occurring, and to identify upset conditions so as to enable execution of evasive action to prevent or mitigated inadvertent emission of gases into the local environment.

In the above description, for purposes of explanation, numerous details are set forth in order to provide a thorough understanding of the present disclosure. However, it will be apparent to one skilled in the art that these specific details are not required in order to practice the present disclosure. Although certain dimensions and materials are described for implementing the disclosed example embodiments, other suitable dimensions and/or materials may be used within the scope of this disclosure. All such modifications and variations, including all suitable current and future changes in technology, are believed to be within the sphere and scope of the present disclosure. All references mentioned are hereby incorporated by reference in their entirety.