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    • 专利摘要:
    A tubular photobioreactor for production of photosynthetic microorganisms is devised. The reactor comprises a growth module, consisting of vertical, transparent tubes, mounted between two circular manifolds. Flow direction is in all transparent tubes is vertically ascending. Flow is recirculated in a closed loop to the lower manifold with a pump. Oxygen is removed in an additional loop in a central degasser column that also functions as structural support of the reactor. The degasser applies a falling-film degassing principle. Advantages of the photobioreactor is low mixing- and mass transfer energy costs; all tube and manifold connections assembled in a single factory supplied growth module, which makes the reactor economic; the vertical orientation of the tubes furthermore provides a more photosynthetically efficient use of the absorbed daily solar irradiation.
    公开号:DK201700570A1
    申请号:DKP201700570
    申请日:2017-10-11
    公开日:2019-04-24
    发明作者:Javier Navas Martos Francisco；Norsker Niels-Henrik；Ángel Moya Muriana José
    申请人:Biotopic；
    IPC主号:
    专利说明:

    Description
    Priority claim
    This invention claims priority from the DK patent application filed 11.10.2017
    Field of invention
    The invention is a tubular photobioreactor, a vessel for the production of photosynthetic microorganisms, including microalgae, photosynthetic bacteria and submerse plant cells.
    General presentation of the problems that the invention aims to solve:
    Note: In the remainder of the description, the target organisms (photosynthetic microorganisms: microalgae, photosynthetic bacteria and submerse plant cells) are for clarity reasons referred to only as microalgae.
    Microalgae require an environment characterized by certain ranges of several physical parameters, including light intensity, temperature, acidity, salinity, dissolved oxygen, inorganic carbon source and concentration and certain inorganic and organic nutrients. Some microalgal species are able to grow under conditions that exclude most other algal species, such as extreme salinity or alkalinity levels or during a short growth cycle and will therefore compete favorably with these organisms in open tanks, but most species need to be produced as monocultures in closed and specially designed bioreactors. As the reactors are optimized for light absorption, they are referred to as photobioreactors.
    With outdoor microalgal production, light and therefore also photosynthesis vary diurnally and with changing weather conditions. Other critical parameters are affected as a consequence, including oxygen concentration, inorganic carbon requirement, pH and nutrient concentrations. Photobioreactor design and operation must therefore able to compensate this.
    Oxygen is a byproduct of photosynthesis and affects growth and photosynthesis negatively and must be disposed of and regulated. Oxygen produced during photosynthesis accumulates as dissolved oxygen and the algal growth medium can reach supersaturation levels up to 500 % before oxygen spontaneously bubbles off as pure O2 gas. Supersaturated oxygen levels in a microalgal culture are difficult and in practice energy requiring to reduce. Transferring dissolved oxygen to gas form in order to strip it off the medium is referred to as mass transfer.
    Mass transfer is normally done in a two-phase system by injection of gas bubbles either directly in the culture or by recirculating the culture through a specialized compartment: a degasser in which the mass transfer takes place. In both cases, the dissolved oxygen will diffuse into the gas bubbles towards an equilibrium concentration, according to Henry’s law.
    The injection of gas bubbles (spargeing) is associated with the problem that an extended contact period with the liquid phase is required to achieve the mass transfer. Injecting atmospheric air at the bottom of a tall degassing column is the normal way of achieving sufficient mass transfer. Producing compressed air for injection at a pressure sufficient for injection at the bottom of a tall liquid filled column is energetically costly and producing compressed air for spargeing is a significant cost factor. The use of solid media such as Raschi rings in a two-phase
    DK 2017 00570 A1 vessel for gas transfer is not used in photobioreactors because of unwanted biofilm growth on the surfaces. The falling-film method is a mass transfer method frequently used in some fields of chemical engineering, for instance as evaporator devices, wherein a liquid film is drifting down the inner side of a tube that transfers heat to the liquid while a spectrum of turbulence movements in the liquid film is driving the mass transfer. This method has so-far also not found widespread use in microalgal oxygen transfer.
    Accomplishing mass transfer in an algal culture is energy demanding; therefore, the aim in degassing is not to reduce oxygen supersaturation completely but reduce the saturation to acceptable levels. It is generally considered that an oxygen saturation of up to 300 percent is acceptable.
    Mixing of the culture is required to manage (break or diminish) local nutrient and light gradients. A certain mixing level with respect to irradiation (light administration) is required or beneficial for the algal growth. It works through shifting the algae between dark and light zones. Mixing with a high frequency (short light periods, from milliseconds to hundreds of milliseconds) has been shown to increase the efficiency of light utilization but is associated with turbulent flow at high Reynolds numbers or induced by insertion of swirl elements in the reactors or creating waves in a two-phase system. In all cases, it is energy requiring. Mixing at lower frequencies, such as tens of seconds, is energetically optimal.
    Furthermore, the photobioreactor normally has a large surface to volume ratio and surface adhesion of the algal cells (resulting in biofilm formation) can be a serious problem, requiring stopping, cleaning and restarting the reactor. Direct causes for biofilm formation are stagnant fluid zones, both because of the possibility of sedimentation/flotation and because the cessation of convective nutrient transport between cells and medium can increase the adhesive properties of the cells.
    To conclude: to reduce the auxiliary energy use with a photobioreactor, mass transfer and mixing must be optimized separately and with respect to mixing, the reactor should be designed to work with a low turbulence level.
    Prior art and reactor specific design issues.
    Tubular reactors are photobioreactors where the irradiation of the algal biomass is taking place in transparent tubes with a suitable diameter; tubular reactors are frequently chosen for the convenience of construction under craftsmanship conditions and availability of transparent construction materials of suitable dimensions, (diameter 2-10cm, but also larger diameters, 20 cm. or more are sometimes used). Tubular reactors are furthermore convenient in terms of operation and cleaning as they exhibit a simple and homogeneous flow pattern. Furthermore, they can be designed to allow biofilm control (inclusion of scouring pellets during operation or use of pig”) or efficient off-line cleaning.
    Current art includes two main types of tubular reactors: reactors with horizontal tubes (from hereof called horizontal tubular reactors) and reactors with vertical tubes (from hereof called vertical tubular reactors). Horizontal tubular reactors are known with either a single layer or stacks of horizontal tubes, connected as serpentine loops or with manifolds. The tube sections distance between degassing in the case of separate degassing) are generally long (up to 100 m). The algal culture is recirculated through the tubes by means of a mechanical or
    DK 2017 00570 A1 air lift pump and mass transfer takes place in a dedicated degasser device. Such reactors are known from: WO2012107544A1, CN106754290, MX2015010637 and US2017037348. Horizontal tubular reactors are characterized by requiring rather large hydraulic flow to press air bubbles that form in the tubes by spontaneous degassing through the tubes and prevent settling of biomass in the tubes. Horizontal tubes experience a high peak noon solar radiation which is poorly utilized by the algal culture.
    Vertical reactors have a more flat diurnal direct sunlight absorption pattern than horizontal reactors (not peaking pronouncedly at noon). This is biologically preferable. Vertical tubular reactors are known from US2009137031A1, WO2011035356, US2014242681, US2011027875 and US2017130181. Except for US2009137031, these reactors are in principle coupled bubble columns with tubes alternating between being air-lifts and downcomers. US2009137031 describes a single-tube reactor with separate degassing taking place in sparged, recirculation tubes.
    An industrial plant with 8 m tall bubble columns has been constructed in the Canarias (http://www.buggypower.eu/es/). A 5 meter tall, vertical air-lift reactor system based on US2017130181 is currently being installed in Austria (https://ec.europa.eu/eipp/desktop/es/projects/project-8.html).
    State of development of the prior art:
    The prior art describes reactors troubled by various combinations of high mixing- and mass transfer energy requirements, complex and not easily cleanable designs and costly craftsmanship dominated reactor manufacturing.
    Improvements of prior art to be achieved:
    Depreciation costs of the photobioreactor, cost of maintenance and operating man-power and use of auxiliary operating energy are, more than anything else important determinants in a commercially successful reactor design. A relatively small, septically isolated stand-alone unit is preferable. Mass transfer and mixing mechanism should be separate. Falling-film degassing is preferable.
    With the present invention, ideal design criteria were determined to be:
    • a tubular reactor with vertically placed tubes of short length (< 5meter) • a separate degassing stage, based on falling-film mass transfer • a mass production facilitated tube-manifold assembly • a relatively small (< 1 m3 culture volume) septically isolated unit.
    Detailled description of the current invention
    List of figures.
    1. Distributor manifold, showing ring-shaped conduit with one inlet port and 40 exit ports,
    2. Collector manifold, showing ring-shaped conduit with one exit port and 40 inlet ports.
    3. A tubular photobioreactor growth unit.
    4. A tubular photobioreactor growth unit mounted on the degasser column.
    DK 2017 00570 A1
    5. Pump assembly.
    The invention is a vertical tubular photobioreactor, wherein light absorption and the light reactions of photosynthesis take place in vertical tubes and oxygen removal in a connected degasser. The transparent tubes are factory mounted between 2 circular, ring-shaped manifolds [figures 1 and 2] and constitute a tubular photobioreactor growth module [fig 3]. The ring-shaped manifolds are designed to be manufactured by rotational molding technology, including all ports. The two manifolds are mounted with all transparent tubes as a single module. During assembly, the inlet to the lower manifold is placed 180 degrees opposite the outlet from the upper manifold in the horizontal plane, providing under operation opposite pressure gradients along the periphery in the circular manifolds, thereby ensuring an even flow ascending in all the vertical tubes. In a pipe descending from the outlet port of the upper manifold to the inlet of the lower manifold, a circulation pump is inserted and provides sufficient flow to ensure the necessary upwards directed fluid velocity in the vertical transparent tubes. The circuit through the vertical transparent tubes and down to the recirculation pump is full-flowing; consequently, the required head of the circulation pump corresponds to the dynamic pressure drop in the tubes and manifold. A preferred embodiment of the photobioreactor has 40 transparent tubes of a length of 5 meter and external diameter of 63 mm and the peripheral diameter of the manifolds is 2 meter. In the preferred embodiment of the reactor, a commercially available axial pump can provide a velocity of 0.3 m sec-1 in the transparent tubes at a power consumption of less than 200 W. At a velocity of 0.3 m sec-1, the hydraulic turnover time in the tubes is 20 seconds and the oxygen concentration at the maximum photosynthetic rate may increase up to 10 % saturation during the ascent, which is counteracted by the degasser column.
    The centrally placed degasser column is functioning also as the support structure element of the reactor [fig.4].
    The flow for to the degasser is drawn from the outlet of the upper circular manifold into a centrally placed gas-filled degasser tube. In one embodiment of the photobioreactor, it is dropped as a free-falling film (not flowing over a surface) to the bottom of a partially gas-filled, ventilated and pressurized degasser vessel from where it is drained and injected into the lower manifold by a second pump, (the degasser pump). In another embodiment, the degasser flow flows down the inner surface of the degasser cylinder. This allows good heat transfer to the cooling jacket, that surrounds the degasser vessel. The static head that the degasser pump needs to provide, is equivalent with the distance from the liquid level in the degasser vessel to the top level of the ejector disc. In a preferred embodiment of the degasser, the said distance can be selected between 1 and 3 meter by adjusting the fluid volume of the reactor, and the power for the degasser pump hence may vary between 20 and 50 W depending on oxygen transfer requirements. The dissolved oxygen concentration in the reactor power can be used to control the power of both the degasser pump and the recirculation and hence reduce the auxiliary energy consumption the reactor to a minimum. The mixing energy consumption is the sum of the energy consumption of the recirculation and degassing pump and is for a standard size reactor (600 liter) < 3 kWhr day-1 or 5 kWhr m-3 day-1. It is interesting to note
    DK 2017 00570 A1 that the auxiliary energy requirement is largely proportional to solar irradiation, which means that photovoltaic panels therefore are ideal to supply the reactors. The reactor is fitted with the following ports:
    • a dosing pump, dosing concentrated nutrient solution from a local reservoir into the reactor (concentrated up to 1000 times in comparison with the final medium) • water inlet port, fitted with a solenoid valve and a guard filter that feeds the reactor process water (fresh- or salt water) from a central water supply • a CO2 addition port on the entry side of the circulation pump, • a gas outlet port in the top cover of the degasser vessel, fitted with a pressostat valve • a gas-bleed valve in the top-point of the outlet of the collector manifold • a harvest port at the bottom of the degasser • a drain port at the lowest point of the reactor (the inlet to the distributor manifold).
    Integration
    The reactor thus described is a septically isolated stand-alone device, characterized by producing microalgal biomass with local or central process control requiring supply of pressurized water, mounted outdoors pressurized CO2, pressurized air. The septic isolation means that a potential contamination cannot pass from one reactor to another.
    Placing reactors in a cluster, there is wide freedom in the choice of distance between reactors and topographical elevation due to the only communications being pressurized supply lines. Mounting a reactor on-site implies mounting and fixing the degasser column and pump assembly [figure 5], placing and fixing the photobioreactor growth unit around the degasser column and mounting a small number of process control items.
    权利要求:
    Claims (13)
    [1] Claims
    What is claimed:
    1. A ring-shaped distributor manifold, comprising:
    a ring-shaped distributor conduit with one or more exit ports, placed in a plane, parallel to the plane, defined by the ring of the said ring-shaped distributor conduit, further, with one or more entry ports.
    [2] 2. A ring-shaped distributor manifold, according to claim 1, in which the ringshaped distributor conduits are circular or polygonal in the plane described by the ring.
    [3] 3. A ring-shaped distributor manifold, according to claim 2, in which the ringshaped distributor conduits are circular or polygonal in the cross-section of the conduit.
    [4] 4. A ring-shaped distributor manifold, according to claim 3, in which the ringshaped distributor conduit may be continuously open over the entire path of the or may be closed by a septum.
    [5] 5. A ring-shaped collector manifold, comprising:
    a ring-shaped collector conduit with one or more entry ports, placed in a plane, parallel to the plane, defined by the ring of the said ring-shaped collector conduit, further, with one or more exit ports.
    [6] 6. A ring-shaped collector manifold, according to claim 5, in which the ringshaped distributor conduits are circular or polygonal in the plane described by the ring.
    [7] 7. A ring-shaped distributor manifold, according to claim 6, in which the said ring-shaped distributor conduit is circular or polygonal in the cross-section of the conduit.
    [8] 8. A ring-shaped distributor manifold, according to claim 7, in which the ringshaped distributor conduit may inside be continuously open over the entire path of the or may be closed by a septum.
    [9] 9. A tubular photobioreactor growth unit, consisting of:
    a distributor manifold, according to claim 4;
    a collector manifold, according to claim 8;
    a set of two or more translucent tubes connecting exit ports of the distributor manifold with entry ports of the collector conduit.
    [10] 10.
    A tubular growth unit, comprising a tubular photobioreactor photosynthesis unit, according to claim 9; further, a recirculation conduit, intersected between
    DK 2017 00570 A1 the exit ports of the said collector manifold and the entry ports of the said distributor manifold and further comprises a circulation pump.
    [11] 11. A degasser, comprising:
    a vertically extended degasser vessel;
    a fluid inlet tube to the said vessel, that may conduct said fluid in a largely vertical, ascending direction inside the said cylinder and eject the said fluid over a circular, horizontally extended flange, mounted at the end of the said inlet tube; an outlet port, draining fluid from the said degasser vessel;
    a gas inlet-port providing gas at a pressure equal to or higher than that of the gas phase of the degasser vessel;
    a gas outlet port, providing gas outlet from the degasser vessel;
    a valve with a pressure regulator, connected to the gas outlet port, controlling the pressure in the said degasser vessel.
    [12] 12. A tubular photobioreactor, comprising a tubular photobioreactor unit, according to claim 10; further, a degassing loop, comprising a degasser, according to claim 11, intersected between an outlet port of the said collector manifold and an entry port of the said distributor manifold, further a pump the function of which is to drain the said chamber and inject the fluid in an entry port of the distributor manifold.
    [13] 13. A tubular photobioreactor according to claim 12, further comprising: a fluid inlet port, mounted preferably at the top of the degasser vessel;
    a fluid drain port, mounted preferably at the bottom of the degasser vessel.
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    同族专利:
    公开号 | 公开日
    DK180369B1|2021-02-10|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    法律状态:
    2019-04-24| PAT| Application published|Effective date: 20190412 |
    2021-02-10| PME| Patent granted|Effective date: 20210210 |
    优先权:
    申请号 | 申请日 | 专利标题
    DKPA201700570A|DK180369B1|2017-10-11|2017-10-11|Column photobioreactor|DKPA201700570A| DK180369B1|2017-10-11|2017-10-11|Column photobioreactor|
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