US20140199639A1 - Process for Managing Photobioreactor Exhaust - Google Patents

Abstract

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.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS
• This application claims priority to U.S. Provisional Application No. 61/753,711 filed Jan. 17, 2013, and U.S. Provisional Application No. 61/759,656 filed Feb. 1, 2013. The entire contents of each of the above—referenced disclosures is specifically incorporated herein by reference without disclaimer.
FIELD
• The present disclosure relates to a process for growing biomass.
BACKGROUND
• The cultivation of phototrophic organisms has been widely practised for purposes of producing a fuel source. Exhaust gases from industrial processes have also been used to promote the growth of phototrophic organisms by supplying carbon dioxide for consumption by phototrophic organisms during photosynthesis. By providing exhaust gases for such purpose, environmental impact is reduced and, in parallel a potentially useful fuel source is produced. Challenges remain, however, to render this approach more economically attractive for incorporation within existing facilities.
SUMMARY
• In one aspect, 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.
• In another aspect, 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, discharging a gaseous exhaust from the reaction zone, separating at least an oxygen-rich product from the gaseous exhaust that is discharged from the reaction zone, and contacting the oxygen-rich product with a fuel to effect combustion.
• In another aspect, 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, discharging gaseous exhaust from the reaction zone, separating at least an oxygen-depleted product from the gaseous exhaust that is discharged from the reaction zone, and supplying the oxygen-depleted product to the reaction zone.
• In another aspect, 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, discharging gaseous exhaust from the reaction zone, and recycling at least a fraction of the discharging gaseous exhaust to the reaction zone.
BRIEF DESCRIPTION OF DRAWINGS
• The process of the preferred embodiments of the invention will now be described with the following accompanying drawing:
• FIG. 1 is a process flow diagram of an embodiment of a system embodying the process;
• FIG. 2A is a process flow diagram of an embodiment of a subsystem embodying the gas treatment process of the process, illustrating at least a portion of the unit operations of the subsystem.
• FIG. 2B is a process flow diagram of another embodiment of a subsystem embodying the gas treatment process of the process, illustrating at least a portion of the unit operations of the subsystem.
• FIG. 3 is a process flow diagram of another embodiment of a system embodying the process; and
• FIG. 4 is a process flow diagram of another embodiment of a system embodying the process.
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 areaction zone10 of a photobioreactor12.
• Thereaction zone10 includes 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 thereaction 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 photobioreactor12 by 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 photobioreactor12 is 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 photobioreactor12 is 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 photobioreactor12 includes thereaction zone10 which includes the reaction mixture. In some embodiments, the photobioreactor12 is 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 thereaction zone10. In this respect, in some embodiments, the photobioreactor12 includes 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 thereaction 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 photobioreactor12 is configured to contain the reaction mixture which is operative for effecting photosynthesis upon exposure to photosynthetically active light radiation. The photobioreactor12 is 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 photobioreactor12 for 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 anartificial light source14 disposed 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 anatural light source16 which has been transmitted from externally of the photobioreactor12 and through a transmission component. In some embodiments, for example, the transmission component is a portion of a containment structure of the photobioreactor12 which is at least partially transparent to the photosynthetically active light radiation, and which is configured to provide for transmission of such light to thereaction zone10 for 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 thereaction zone10 with 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, NO_Xand SO_X. 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 photobioreactor12 that is above the aqueous medium within the photobioreactor12.
• Carbon dioxide is supplied to thereaction zone10 of the photobioreactor12 for 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-comprisingexhaust material14 being discharged by a carbon dioxide-comprising gaseous exhaustmaterial producing process16. The at least a fraction of the carbon dioxide-comprisingexhaust material14, that is being supplied to the photobioreactor12, defines the photobioreactor supply122.
• In some embodiments, for example, the carbon dioxide-comprisinggaseous exhaust material14 includes a carbon dioxide concentration of at least two (2) volume % based on the total volume of the carbon dioxide-comprisinggaseous exhaust material14. In some embodiments, for example, the carbon dioxide-comprisinggaseous exhaust material14 includes a carbon dioxide concentration of at least four (4) volume % based on the total volume of the carbon dioxide-comprisinggaseous exhaust material14. In some embodiments, for example, the gaseousexhaust material reaction14 also includes one or more of N₂, CO₂, H₂O, O₂, NO_x, S0_x, CO, volatile organic compounds (such as those from unconsumed fuels) heavy metals, particulate matter, and ash. In some embodiments, for example, the carbon dioxide-comprisinggaseous exhaust material14 includes 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-comprisinggaseous 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-comprisinggaseous exhaust material14 includes one or more other materials, other than carbon dioxide, that are beneficial to the growth of the phototrophic biomass within thereaction zone10. Materials within the gaseous exhaust material which are beneficial to the growth of the phototrophic biomass within thereaction zone10 include SO_X, NO_X, and NH₃.
• The carbon dioxide-comprising gaseous exhaustmaterial producing process16 includes any process which effects production and discharge of the carbon dioxide-comprisinggaseous exhaust material14. In some embodiments, for example, the carbon dioxide-comprising gaseous exhaustmaterial producing process16 is 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, asupplemental nutrient supply18 is supplied to thereaction zone10 of the photobioreactor12. In some embodiments, for example, thesupplemental nutrient supply18 is effected by a pump, such as a dosing pump. In other embodiments, for example, thesupplemental nutrient supply18 is supplied manually to thereaction zone10. Nutrients within thereaction zone10 are 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). Thesupplemental nutrient supply18 is 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, thesupplemental nutrient supply18 includes “Bold's Basal Medium”. In some embodiments for example, thesupplemental nutrient supply18 includes 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 thesupplemental nutrient supply18 to thereaction zone10 is controlled to align with a desired rate of growth of the phototrophic biomass in thereaction zone10. In some embodiments, for example, regulation of nutrient addition is monitored by measuring any combination of pH, NO₃concentration, and conductivity in thereaction zone10.
• In some embodiments, for example, a supply of the supplemental aqueous material supply20 is effected to thereaction zone10 of the photobioreactor12, so as to replenish water within thereaction zone10 of the photobioreactor12. In some embodiments, for example, and as further described below, the supplemental aqueous material supply20 effects the discharge of product from the photobioreactor12 by displacement. For example, the supplemental aqueous material supply20 effects the discharge of product from the photobioreactor12 as 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 supply20 includes aqueous material that has been separated from a discharged phototrophic biomass-comprisingproduct32 by a separator50 (such as a centrifugal separator). In some embodiments, for example, the supplemental aqueous material supply20 is 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 supply20 is 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, thesupplemental nutrient supply18 is mixed with the supplemental aqueous material20 in amixing tank24 to provide a nutrient-enriched supplemental aqueous material supply22, and the nutrient-enriched supplemental aqueous material supply22 is supplied to thereaction zone10. In some embodiments, for example, thesupplemental nutrient supply18 is mixed with the supplemental aqueous material20 within the container which has collected the discharged aqueous material. In some embodiments, for example, the supply of the nutrient-enriched supplementalaqueous material supply18 is effected by a pump.
• The reaction mixture disposed in thereaction zone10 is 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 thereaction zone10 for 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 thereaction 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 thereaction 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 thereaction 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 thereaction zone10 even 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 artificiallight source14 include 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 thereaction zone10 is disposed in a photobioreactor12 which 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 thereaction 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 thereaction zone10. In some embodiments, in addition to solar light, the light tubes in the photobioreactor12 contains 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 thereaction zone10 during 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 photobioreactor12 so 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 thereaction 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-comprisinggaseous 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 thereaction zone10 is being effected.
• In some embodiments, for example, the growth rate of the phototrophic biomass is dictated by the available carbon dioxide within thereaction 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 product30 is discharged from thereaction zone10. Thereaction zone product30 includes phototrophic biomass-comprisingproduct32. In some embodiments, for example, the phototrophic biomass-comprisingproduct32 includes at least a fraction of the contents of thereaction zone10. In this respect, the discharge of thereaction zone product30 effects harvesting of thephototrophic biomass40.
• In some embodiments, for example, the harvesting of the phototrophic biomass is effected by discharging thephototrophic biomass32 from thereaction zone10.
• In some embodiments, for example, the discharging of thephototrophic biomass32 from thereaction zone10 is effected by displacement. In some of these embodiments, for example, the displacement is effected by supplying supplemental aqueous material supply20 to thereaction zone10. In some of these embodiments, for example, the displacement is an overflow. In some embodiments, for example, the discharging of thephototrophic biomass32 from thereaction zone10 is effected by gravity. In some embodiments, for example, the discharging of thephototrophic biomass32 from thereaction zone10 is effected by a prime mover that is fluidly coupled to thereaction zone10.
• In some embodiments, for example, the at least a fraction of carbon dioxide-comprisinggaseous exhaust material14 is passed through thereaction zone10 for effecting the photosynthesis such that the carbon dioxide-comprisinggaseous exhaust material14 becomes depleted in carbon dioxide, and such that production of agaseous photobioreactor exhaust60, including photobioreactor-exhausted carbon dioxide, is effected and exhausted into theheadspace13. In some embodiments, for example, the carbon dioxide concentration within thegaseous photobioreactor exhaust60 is less than the carbon dioxide concentration within the carbon dioxide-comprisinggaseous exhaust material14.
• In some embodiments, for example, at least a fraction of the carbon dioxide-comprisinggaseous exhaust material14 is supplied to agas treatment process100, as pre-treatedgaseous exhaust material141 to generate a treated gaseous exhaust material142. Thegas treatment process100 includes one or more separate unit operations for effecting separation of at least a fraction of the pre-treatedgaseous exhaust material141 to yield treated gaseous exhaust material142. Exemplary unit operations include bag houses, NO_Xfilters, SO_Xfilters, 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 material142 is supplied as the photobioreactor supply122.
• In some embodiments, for example, at least a fraction of the treated material142 is supplied to thesmokestack200. In some embodiments, for example, a fraction of the treated material142 is supplied to thesmokestack200 as asmokestack supply201, while another fraction of the treated material142 is supplied to the photobioreactor12 as the photobioreactor supply122. In some embodiments, for example, the fraction supplied as thesmokestack supply201, and the fraction supplied as the photobioreactor supply122, is determined by a damper orstack cap202 within the smokestack. The damper orstack cap202 is biased (such as by spring forces) to seal fluid communication between the treated material142 and the smokestack such that all of the treated material142 is supplied to thereaction zone10 of the photobioreactor12. The damper orstack cap202 is 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 thesmokestack200
• In some embodiments, for example, there is nogas treatment process100, and at least a fraction of theexhaust material14 is supplied directly to thesmokestack200 as a smokestack supply. In some of these embodiments, for example, a fraction of theexhaust material14 is supplied to thesmokestack200 as thesmokestack supply201, while another fraction of theexhaust material14 is supplied to the photobioreactor12 as the photobioreactor supply122. In some embodiments, for example, the fraction supplied as thesmokestack supply201, and the fraction supplied as the photobioreactor supply122, is determined by a damper orstack cap202 within the smokestack, as described above.
• Thephotobioreactor exhaust60 is discharged from the photobioreactor12.
• The rate of discharging of theexhaust60 is modulated as between a local discharge61 and a further processing discharge62 by avalve1200, based on sensed concentrations of various gases, such as carbon dioxide, diatomic oxygen, NO_X, and SO_X. It is desirable forexhaust60 having excessive carbon dioxide, NO_X, or SO_Xconcentrations not to be exhausted, locally, at ground level, and to directsuch exhaust60 for recycling within the process, or to thesmokestack200, or to acold 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 ofexhaust60 to 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, thegas treatment process100 includes 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 thestream601 deriving from theexhaust60, and delivery of a gas, of a sufficient gaseous diatomic oxygen concentration to effect combustion of a fuel, to theindustrial process16, for effecting the combustion of a fuel. In some embodiments, for example, thestream601 is indirectly heated by at least a fraction of thegaseous exhaust material14. The heating of thestream601 increases the internal energy of thestream601, including that of the oxygen-rich stream that is separated from thestream601, 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-comprisinggaseous 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 aheat exchanger900 be effecting disposition of thestream601 in indirect heat transfer communication with the at least a fraction of thegaseous exhaust material14.
• Referring toFIG. 2A, in some embodiments, for example, thegas treatment process100 includes a single membrane separation unit operation.101 for effecting enrichment of gaseous diatomic oxygen. Theunit operation101 receives astream601 of the exhaust60 (or a post-treatment stream that is derived from thestream601, after thestream601 has been subjected to pre-treatment by another unit operation within process100) to effect separation of an oxygen-rich stream612 and an oxygen-depletedstream614 from thestream601. Relative to the oxygen-depletedstream614, the oxygen-rich stream612 is rich in oxygen and nitrogen and any other relatively smaller molecules (e.g. mercury). Relative to the oxygen-rich stream612, the oxygen-depletedstream614 is rich in carbon dioxide, NO_X, SO_X, volatile organic compounds, and other relatively larger molecules. The supply of the oxygen-rich stream612, as between theprocess16 and thesmokestack200, 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 astream622, to theprocess16 is initiated, or the molar rate of supply of the stream612, as thestream622, to theprocess16 increased. 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 astream624, to thesmokestack200 is initiated, or the molar rate of supply of the stream612, as thestream624, to thesmokestack200 is increased. The oxygen-depletedstream614, which is rich in carbon dioxide, NO_X, SO_X, 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 material142 is supplied to thereaction zone10. In this respect, at least a fraction of the oxygen-depletedstream614, 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 thereaction zone10. The removal of material (including gaseous diatomic oxygen) from thestream601 also eliminates the need for larger gas handling equipment, which would have been required if the material is not removed from thesteam614 before it is recycled to thereaction zone10 of the photobioreactor12.
• Referring toFIG. 2B, in some embodiments, for example, thegas treatment process100 includes two membraneseparation unit operations101,102, disposed in series for effecting a two-stage enrichment of gaseous diatomic oxygen. Theunit operation101 receives the stream601 (or a post-treatment stream that is derived from thestream601, after thestream601 has been subjected to pre-treatment by another unit operation within process100) to effect separation of an oxygen-rich stream612 and an oxygen-depletedstream614 from the stream611. Relative to the oxygen-depletedstream614, the oxygen-rich stream612 is rich in oxygen and nitrogen and any other relatively smaller molecules (e.g. mercury). Relative to the oxygen-rich stream612, the /oxygen-depletedstream614 is rich in carbon dioxide, NO_X, SO_X, volatile organic compounds, and other relatively larger molecules. The oxygen-rich stream612 is supplied to the membraneseparation unit operation201 and is separated into a further oxygen-enrichedstream622 and a nitrogen-enrichedstream624. The further oxygen-enrichedstream622 is supplied to theindustrial process16, and the nitrogen-rich stream624 is supplied to thesmokestack200. The oxygen-depletedstream614, which is rich in carbon dioxide, NO_X, SO_X, 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 material142 is supplied to thereaction zone10 of the photobioreactor12. In this respect, at least a fraction of the oxygen-depletedstream614, 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 thereaction zone10. The removal of material (including gaseous diatomic oxygen) from thestream601 also eliminates the need for larger gas handling equipment, which would have been required if the material is not removed from thesteam614 before it is recycled to thereaction zone10 of the photobioreactor12.
• Referring toFIG. 3, in some embodiments, for example, thegas treatment process100 is not configured for effecting enrichment of gaseous diatomic oxygen, such that at least a fraction of theexhaust60 is supplied to theprocess16 in 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 valve6005 is provided to modulate supply of thestream601, as between theprocess16 and as a recycle stream to thephotobioreactor10. 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 thestream601, as astream632, to theprocess16, is initiated, or a molar rate of supply of thestream601, as astream632, to theprocess16, is increased. In parallel, the supply of thestream601, as astream634, to the treated exhaust142, is suspended, or the molar rate of supply of thestream601, as astream634, 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 thestream601, as astream632, to theprocess16, is suspended, or the molar rate of supply of thestream601, as astream632, to theprocess16, is decreased. In parallel, the supply of thestream601, as astream634, to the treated exhaust142, is initiated, or the molar rate of supply of thestream601, as astream634, 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 theexhaust60 is conducted to thesmokestack200, or to acold stack300, so as to effect its discharge into the environment at an elevation above ground level. Thesmokestack200 may be a pre-existing smokestack that had been previously receiving at least a fraction of theexhaust14 from theprocess16 prior to commissioning of the photobioreactor12, or which is currently receiving a fraction of theexhaust14 from theprocess16, such as while a fraction of theexhaust14 is being supplied to the photobioreactor12 as the photobioreactor supply122. If, however, thesmokestack200 is remote from the photobioreactor12, acold stack300, local to the photobioreactor12, may be provided to provide the same functionality as thesmokestack200, without the added infrastructure and expense of having to conduct theexhaust60, over long distances, to aremote smokestack200. Under normal operating conditions, theexhaust60 is not discharged to asmokestack200 or acold 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 thevalve1200. 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 theexhaust60 as the further processing discharge62 for further downstream processing, as described above. In this situation, avalve6007 is provided for modulating the rate of supply of at least a fraction of the discharge62, as astream642, to thesmokestack200, and may become disposed to effect fluid communication between thereaction zone10 and thesmokestack200, when . upset conditions are sensed and a sensed gas concentration (for example, carbon dioxide concentration) exceeds a predetermined threshold. Similarly, avalve6009 is provided for modulating the rate of supply of the discharge62, as astream652 to thecoldstack300, and may become disposed to effect fluid communication between thereaction zone10 and thesmokestack300, 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 asmokestack200 and at least another point ofdischarge800. The at least another point of discharge can include a point of discharge for supplying the exhausted carbon dioxide62 as part of thephotobioreactor exhaust60 to any one of the reprocessing operations described above. The at least another point ofdischarge800 can 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 thesmokestack200, (b) suspending the supply of the photobioreactor-exhausted carbon dioxide to thesmokestack200, (c) increasing the molar rate of supply of the photobioreactor-exhausted carbon dioxide to thesmokestack200, or (d) decreasing the molar rate of supply of the photobioreactor-exhausted carbon dioxide to thesmokestack200. By initiating the supply of the photobioreactor-exhausted carbon dioxide to thesmokestack200, or increasing the molar rate of supply of the photobioreactor-exhausted carbon dioxide to thesmokestack200, 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 thesmokestack200, or increasing the molar rate of supply of the photobioreactor-exhausted carbon dioxide to thesmokestack200, 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-comprisingexhaust material14, being discharged by a carbon dioxide-comprising gaseous exhaustmaterial producing process16, is being supplied to thesmokestack200 while another fraction of the carbon dioxide-comprisingexhaust material14 is being supplied to thereaction zone10. In this respect, the at least a fraction of carbon dioxide-comprisinggaseous exhaust material14 being supplied to thereaction zone10 is less than the entirety, or the substantial entirety, of the carbon dioxidegaseous exhaust material14 being discharged by the carbon dioxide-comprising gaseous exhaustmaterial 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-comprisinggaseous exhaust material14, or a sensed carbon dioxide concentration of thegaseous 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 photobioreactor12 can 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 thesmokestack200, and the modulating is effected in response to the sensing of either one of (i) an indication of a carbon dioxide concentration of thegaseous photobioreactor exhaust60 that exceeds a predetermined concentration, or (ii) an indication of a carbon dioxide concentration of thegaseous exhaust material14 that 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 thesmokestack200 for 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 aflow control device1200, disposed between the photobioreactor12 and thesmokestack200 for selectively interfering with fluid communication between the photobioreactor12 and thesmokestack100, to effect initiation of supply of, or an increase in the molar rate of supply of, the photobioreactor-exhausted carbon dioxide to thesmokestack200.
• 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 thesmokestack200, and the modulating is effected in response to the sensing of a molar rate of discharge of carbon dioxide from the photobioreactor12 that 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 thesmokestack200 for purposes of environmental abatement. In this respect, a carbon dioxide sensor senses the carbon dioxide concentration of the dischargedphotobioreactor exhaust60 and 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 ofphotobioreactor exhaust60 being 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 photobioreactor12 and 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 photobioreactor12 exceeds the predetermined molar flow rate, and transmits a signal to aflow control device1200, disposed between the photobioreactor12 and thesmokestack200 for selectively interfering with fluid communication between the photobioreactor12 and thesmokestack200, to effect initiation of supply of, or an increase in the molar rate of supply of, the photobioreactor-exhausted carbon dioxide to thesmokestack200.
• In some embodiments, for example, the photobioreactor-exhausted carbon dioxide62 is indirectly heated by at least a fraction of the carbon dioxide-comprisinggaseous exhaust material14 being supplied to thereaction zone10, such that an increase in temperature to the exhausted carbon dioxide62 is 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-comprisinggaseous 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 aheat exchanger901 be effecting disposition of the exhausted carbon dioxide62 in indirect heat transfer communication with the at least a fraction of thegaseous exhaust material14.
• In some embodiments, for example, the photobioreactor-exhausted carbon dioxide62 is 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 dioxide62 such 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,3 and4 may 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.

Claims (16)

1. 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, comprising:

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 (or a cold stack) and at least another point of discharge.

2. The process ofclaim 1, wherein the modulating is based on an indication of the molar rate at which carbon dioxide is being exhausted from the reaction zone.

3. The process ofclaim 1, further comprising supplying another fraction of the gaseous exhaust material, being discharged by the industrial process, to the smokestack.

4. 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, comprising:

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;

discharging a gaseous exhaust from the reaction zone;

separating at least an oxygen-rich product from the gaseous exhaust that is discharged from the reaction zone; and

contacting the oxygen-rich product with a fuel to effect combustion.

5. The process ofclaim 4, wherein the contacting of the oxygen-rich product with a fuel is effected within a combustor of the industrial process.

6. The process ofclaim 5, further comprising, prior to the contacting, supplying the oxygen-rich product to the combustor.

7. The processclaim 4,

wherein the separating includes separating an oxygen-depleted product from the gaseous exhaust that is discharged from the reaction zone;

and further comprising supplying the oxygen-depleted product to the reaction zone.

8. 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, comprising:

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;

discharging gaseous exhaust from the reaction zone;

separating at least an oxygen-depleted product from the gaseous exhaust that is discharged from the reaction zone; and

supplying the oxygen-depleted product to the reaction zone.

9. 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, comprising:

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;

discharging a gaseous exhaust from the reaction zone; and

heating the discharging gaseous exhaust with at least a fraction of the gaseous exhaust material to generate a heated gaseous exhaust.

10. The process ofclaim 9, wherein the heating is effected by disposing the discharging gaseous exhaust in heat transfer communication with the at least a fraction of the gaseous exhaust material.

11. The process ofclaim 10, wherein the heat transfer communication is indirect.

12. The process ofclaim 8, further comprising contacting at least a fraction of the heated gaseous exhaust with a fuel to effect combustion of the fuel.

13. The process ofclaim 8, further comprising supplying at least a fraction of the heated gaseous exhaust to a combustor, and effecting contacting of the at least a fraction of the heated gaseous exhaust with a fuel to effect combustion of the fuel.

14. The process ofclaim 12, wherein, prior to the contacting, the gaseous exhaust is treated to effect generation of an oxygen-enriched product, wherein the at least a fraction of the heated gaseous exhaust includes the oxygen-enriched product.

15. 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, comprising:

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;

discharging gaseous exhaust from the reaction zone; and

recycling at least a fraction of the discharging gaseous exhaust to the reaction zone.

16. 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, comprising:

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 the molar rate of supply of carbon dioxide, being exhausted from the reaction zone, to a smokestack or a cold stack.

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