EE202000016A - Modular photobioreactor - Google Patents

Abstract

Modular photobioreactor consist of modular frame into which a closed growing vessel with inlet for the algal culture and outlet for the biomass harvesting, inlet and outlet for the gases, mixing system with motor, control system for the growing medium is fitted. The growing vessel is composed of two concentric cylinders, inner and outer, of different diameters that are situated inside one another, and caps that connect the two cylinders. There are mixing blades attached to the rotating inner cylinder in order to make mixing of the algal biomass more efficient. The modular frame of the modular photobioreactor is equipped with connecting elements, which allows for stacking of several reactors on top of each other.

Description

 MODULAR PHOTOBIOREATOR

TECHNICAL FIELD

The present invention belongs to the field of microbiology, more specifically, a device for mass cultivation of photosynthetic microorganisms is used for biomass production.

STATE OF THE ART

Microalgae are suitable organisms for several biotechnological applications and for growing valuable biomass. For example, microalgae can be used to clean smoke and chimney gases from carbon dioxide, which is in the order of 10-20% in smoke gases, and to remove nitrogen and phosphorus compounds from wastewater. Depending on the production method, biomass can be used to produce valuable compounds (e.g. pigments, omega-fatty acids, proteins, etc.), to produce fuels (bioethanol, biodiesel and biomethane) or to use biomass as fertilizer or feed. The advantages of growing microalgae biomass are as follows:

1) rapid growth and high photosynthetic efficiency compared to cultivated plants,

2) does not require fertile surface for growth - aquaculture can be grown in various conditions, including indoors,

3) do not require large amounts of plant protection products, including pesticides, to grow, which makes their production cheaper than cultivated plants,

4) does not require specific fertilizers - can be grown in either filtered or sterilized natural water or in domestic or industrial wastewater.

To effectively exploit the biotechnological potential of microalgae, their cultivation is necessary. Microalgae cultivation can be carried out both in open pool-type reactors and in closed photobioreactors. In all known reactors, the most important tasks are to ensure uniform and correct spectrum of illumination, to allow alternating light and dark cycles, to ensure and maintain the nutrient, environmental temperature, acidity (pH), salinity ranges, to mix the culture and to ensure effective

ensuring gas exchange. The most effective cultivation occurs when the most effective cultivation conditions are ensured by the technological system.

Light regime. Light is one of the most important inputs for photosynthetic organisms. Photosynthesis occurs with light with a wavelength of 380 to 760 nm, or photosynthetically active radiation. In addition, algae have two absorption maxima in the blue part of the light spectrum, with a wavelength between 450 and 475 nm, and in the red part, with a wavelength between 630 and 675 nm. For the most efficient photosynthesis, light must be suitable in terms of both its spectrum and intensity. Too strong light damages the photosynthetic apparatus of microalgae and thereby inhibits photosynthesis, while under conditions of too weak light, the proportion of cellular respiration increases, which means that no more biomass is produced. The density of the algae culture is also an important factor in ensuring lighting. In the case of dense biomass, cells shade each other, where cells located closer to the light source absorb most of the light, while the more distant layers remain limited by light. Simply increasing the light intensity is not enough to solve the problem - in this case, cells closer to the light source will be damaged, but cells further away will still not receive enough light. To ensure uniform illumination, it is important to:

1) optimize the optical path length of light depending on the reactor diameter,

2) optimize the density of the solution containing the algae culture depending on the amount of biomass, removing it from time to time,

3) stir the solution containing the algae culture to avoid the formation of dark zones and to ensure that all culture cells are exposed to light.

Availability of nutrients. Microalgae require micro and macro elements for metabolism. The most important nutrients are nitrogen, phosphorus and, in the case of heterotrophic species, carbon. Algae can be grown on synthetic media as well as in filtered and sterilized natural water or domestic wastewater.

Temperature and acidity (pH). Different algae species have different optimal temperature and acidity (pH) ranges. Among algae, there are both cold-loving and warm-loving species, and species that prefer both alkaline and acidic environments. Temperature and

The presence of oxygen (O2) and carbon dioxide (CO2) in the solution environment and the availability of several nutrients depend on acidity (pH).

Agitation mode. To ensure uniform distribution of nutrients and to avoid the formation of blind zones, the solution containing the algae culture must be continuously agitated. The agitation speed must be sufficient to ensure effective agitation, but not such that it damages or breaks the cells. The agitation speed is determined individually for each algae species during the experiments.

Known reactors used for mass cultivation of algae have both advantages and disadvantages. In the case of open pool type reactors, cultures can be grown outdoors, using sunlight to illuminate the culture. In order to better control the temperature and thus evaporation, it is advisable to install such reactors in greenhouses. The disadvantages are the risk of contamination with foreign organisms and lower biomass yield compared to closed reactors. The advantages of closed reactors, or photobioreactors, are a larger specific surface area, better control over growth conditions, a lower risk of contamination and a higher biomass yield. The most common type of photobioreactor is a tubular reactor made of transparent material and illuminated from the outside, in which the tubes have a small diameter (up to 10 cm) to ensure maximum light transmission.

According to patent document CN102250756 B, a cylindrical photobioreactor made of transparent material is known, inside of which a movable spherical light source is located. The bottom of the known photobioreactor is covered with a light-reflecting material, which scatters and reflects the light of the light source, thereby ensuring uniform illumination in the reactor. The disadvantage of the known photobioreactor is the lack of a gas exchange system, temperature control and the possibility of biomass separation.

According to patent document US7824904 B1, a closed photobioreactor with internal lighting is known, which is made of glass, plastic or stainless steel. The known photobioreactor has a rotating mixing system and the light source is attached to the mixing blades. Fluorescent or phosphorescent lamps, LED lamps or an optical cable are used as the light source. The amount of light provided by the light source depends on the size of the reactor, the type of algae and the density of the culture to be grown. The power source is located outside the photobioreactor and it is possible to use a solar panel and batteries for this. Known

The technical solution describes two mixing systems: first, a shaft connected to a motor, to which blades are attached, and second, an oscillation system consisting of fixed and movable frames, which are driven by a motor. The mixing blades attached to the frames can move up, down, forward and backward, and the mixing speed is variable. To add carbon dioxide (CO2), the reactor is equipped with a device that produces it, which includes a fuel burner with a system for conducting carbon dioxide (CO2) into the photobioreactor. Glucose or cellulosic material is used as fuel. The possibility of utilizing residual heat for drying biomass is described. The known photobioreactor is equipped with a harvesting system, which can be a filter system, an ultrasonic device or a centrifuge. The disadvantage is that uniform light distribution in the reactor is not ensured.

According to patent document KR20030018196 A, a cylindrical closed photobioreactor with internal lighting is known. The light source is LED plates or fluorescent lamps, which are attached to stirring blades made of transparent material and surrounded by a transparent waterproof material. The light intensity is adjustable from 200 to 3000 μmol/m2s and external lighting can also be used if necessary. The disadvantage of the known bioreactor is that it does not have the ability to measure and regulate temperature. The stirring blades are located perpendicular to the bioreactor and are made of transparent material, either glass or polycarbonate plastic.

According to patent document GB2469198 A, a closed photobioreactor is known, in which two cylinders are located inside each other so that the inner cylinder contains a light source, the outer cylinder contains a solution containing an algal culture. The light source is a fluorescent lamp with a blue and red light spectrum, which is connected to a timer. The timer can be used to regulate the alternation of light and darkness in the photobioreactor. For mixing, pipes connected to pumps are used, which are located in a circle around the light source and with which the algal culture at the bottom of the reactor is pumped into the upper layers of the solution. A disadvantage of the known technical solution is that there is no possibility of temperature regulation and no gas addition system.

According to patent document US20100028977 A1, there is a known technical solution consisting of one or more tubular closed photobioreactors connected to each other by a common bottom. Each tube contains a strip of light-emitting and/or transmitting material, the latter carrying light from a solar panel or battery located outside the reactor to the interior of the photobioreactor. The light strips are moved by a rotating rotor, which ensures uniform light distribution.

distribution. The solution containing the algae culture is stirred by means of carbon dioxide bubbled through the bottom of the photobioreactor. Each tube is equipped with an inlet and outlet for the nutrient solution and a gas inlet. By adjusting the amount of CO2 bubbled through, the pH of the solution is also adjusted. There is a separate sensor in the reactor to measure the pH level. In addition, there are sensors for temperature, viscosity, turbidity, stirring speed and dissolved oxygen. Turbidity is measured with an optical sensor, which allows the concentration of algae biomass to be calculated and thereby biomass to be removed and fresh nutrient solution to be added, if necessary. The disadvantage is that the temperature of the solution containing the algae culture is not regulated.

The closest solution technically is the technical solution known from patent document EE05801 B1, which includes closed vessels for accommodating the algae culture with a nutrient solution inlet and biomass outlet and a gas inlet, a light source, a viscosity, pH, turbidity, dissolved oxygen and temperature sensor, wherein the closed vessel is two horizontal, rotating double-walled cylinders located on one axis of rotation, with the outer walls and inner walls and ends of which and a fixed part connecting the rotating double-walled cylinders forming a limited closed space filled with a solution containing the algae culture, an internal light source located in the middle of the rotating double-walled cylinders of the photobioreactor, and a fan for blowing away the excess heat generated by it. The disadvantage of the known technical solution is that the non-rotating fixed part makes the design of the photobioreactor complex and cumbersome, the self-cleaning ability of this light source and the specific yield per unit area are low.

Based on the prior art, a disadvantage of the known technical solution is that the light sources are located directly inside the solution containing the algae culture, which is why algae cells can attach to the light source, thereby reducing the intensity of light reaching the cells in the solution. The operation of the known apparatus is also complex, it is difficult to further develop the capability of measuring and controlling the mode parameters, and it is economically inefficient.

The aim of the present invention is to ensure efficient growth and mass cultivation of photosynthetic microorganisms by increasing the specific yield per unit area of the photobioreactor, while reducing the cost of biomass production and thereby improving the economic efficiency of microalgae production.

ESSENCE OF THE INVENTION

The essence of the present invention is to create a photobioreactor different from existing solutions, which improves the aforementioned disadvantages and allows for more efficient and economically profitable cultivation of microalgae in rooms or places where there is no natural light or the amount of natural light is low.

The modular photobioreactor includes a modular frame, inside which is placed a closed growing vessel for accommodating the algae culture with an algal culture inlet and an outlet for biomass and a gas inlet and outlet, a mixing system with a drive, a lighting system, a system for controlling environmental factors, whereby the growing space includes two horizontal outer cylinders of different diameters, located inside each other and on the same axis, an inner cylinder, and ends between the cylinders. To increase the efficiency of mixing the algae mass, mixing blades are attached to the rotating inner cylinder of the growing vessel by means of spokes and fastening elements, and it is equipped with a controller control system designed to ensure synchronized operation of the mixing speed controller, the light change controller, and the environmental factor monitoring and change controller, data recording, and remote control of the modular photoreactor operating process. The modular frame of the modular photobioreactor is equipped with connecting elements for connecting modular photoreactors into microalgae production units by placing modular photoreactors on top of each other, with the aim of increasing the efficiency of microalgae cultivation per unit area. The inclination angle and torque of the mixing blades of the modular photobioreactor are variable to ensure more effective mixing of the algae culture in the growth vessel in all directions, both longitudinally and transversely. The modular photobioreactor is equipped with a controller control system, the task of which is to ensure the automation of the inputs of the modular photobioreactor - nutrient solutions, gases, light - according to the data received from the lighting system and the environmental factors control system; remote monitoring and control of the working process of the modular photobioreactor, which allows the use of modular photobioreactors in difficult-to-access places.

LIST OF DRAWINGS

The present technical solution of the invention is described in more detail in Figures 1, 2, 3, 4 and 5, which are attached to the exemplary embodiment.

Figure 1 shows a complete microalgae production unit consisting of several modular photobioreactors.

Figure 2 shows a view and partial section of a modular photobioreactor.

Figure 3 shows an axonometric view of a modular photobireactor.

Figure 4 shows an end view A of the modular photobioreactor in Figure 2.

Figure 5 shows an end view B of the modular photobioreactor in Figure 2.

EXAMPLE

Figure 1 shows a complete microalgae production unit 2 consisting of modular photobioreactors 1. It includes a multi-storey structure assembled from modular photobioreactors 1 mounted on top of each other, which makes it possible to concentrate a larger number of independently functioning devices for growing microalgae on a smaller production area. Each individual modular photobioreactor 1 includes a module frame 3 and a growth vessel 4. The module frame 3 holds the growth vessels 4 located in the production unit 2 one above the other, thereby ensuring sufficient access for biomass separation, nutrient addition, gas exchange, and also allows for fixing the attachment of the drives performing the mixing. The module frame 3 is equipped with connecting elements 5, thanks to which it is possible to place them on top of each other, which makes it possible to fill high production spaces with such microalgae production units 2, increasing the mass of growing microalgae per unit area. The culture vessels 4 are placed on supports 6 of the modular frame 3, which are arranged in such a way as to ensure uniform support throughout the culture vessel 4. All culture vessels 4 are placed at a slight slope to enable more efficient removal of biomass. The microalgae production units 2 can be stationary (they do not have wheels and are fixed to a flat surface) or mobile if an adjustable support leg 8 or wheel is placed under the modular frame 3 on the leg attachment 7. The stationarity of the production unit 2 of the photobioreactor modules 1 is important when it comes to higher shelves.

Figures 2 and 3 show a modular photobioreactor 1, which includes a closed growth vessel 4 for accommodating the algae culture with a solution inlet 9 and a biomass outlet 10 and a gas inlet 11 and outlet 12, a modular frame 3, a mixing system 13,

lighting system 14, environmental factors control system 15 and controller control system 16. A closed vessel containing a solution containing the algae culture is created between two different diameters, horizontally located inside each other and on the same axis, an outer cylinder 17 and an inner cylinder 18, and hermetically sealed ends 19 connecting the cylinders. The hermeticity of the space is ensured by seals 20. Access to the liquids necessary for growing the algae culture is ensured through solution inlets 9, which pass through the top of the outer cylinder 17. Removal of the grown biomass is ensured through a biomass outlet tap 10, which is located at the bottom of the outer cylinder 17. The biomass outlet tap 10 is equipped with a pipe 21 for directing the biomass away from the growth vessel 4. Enrichment of the algae culture with CO2 and air is ensured through the gas inlet 11, which is a horizontal pipe equipped with downward openings located at the bottom of the outer cylinder 17. The separation of residual gases is carried out through the gas outlets 12, which pass through the top of the outer cylinder 17, above the limit of filling with algae mass and are equipped with filters to reduce the risk of contamination.

The inner cylinder 18 is transparent to light and is used as a shaft for the mixing blades 22. The movement of the mixing blades 22, which are attached to the inner cylinder 18 by means of spokes 23 and fastening elements 24 and whose angle of inclination and torque can be changed to ensure a more uniform distribution of the algae mass in the growing cylinder, is ensured by the mixing system 13. The mixing system 13 includes a drive, the components of which are an electric motor 25 to ensure the rotation of the inner cylinder 18 around its longitudinal axis and a transmission, a reducer 26 to reduce the rotation frequency of the shaft of the electric motor 25 to a level that does not break the structure of the microalgae, but allows for more uniform mixing of nutrients and reduces the risk of microalgae adhering to the walls of the outer cylinder 17, a clutch 27 to reduce the stresses of the motor transmission, the mixing blades 22 and a controller for changing the mixing speed, more specifically the speed of rotation of the mixing blades 22, i.e. the mixing speed controller 28. The drive rests on a drive support frame rigidly attached to the module frame 3 29 sides.

The lighting system 14 includes a light source 30 (Figure 5) located in the center of the inner cylinder 18 and is adjustable by a light change controller 31. The environmental control system 15 consists of a sensor housing 32 containing various sensors and is attached to the end of the growing cylinder 19 and connected to an environmental monitoring and change controller 33. The controller control system 16 is responsible for ensuring the operation of all controllers - the mixing speed controller 28, the light change controller 31 and

33-synchronized action of the controller for monitoring and changing environmental factors, data recording and remote control.

Based on independently functioning model photobioreactors 1, a microalgae production unit 2 is assembled by connecting modular frames 3, forming a multi-story structure according to the parameters of the existing production space.

The modular photobioreactor operates as follows. A solution containing an algal culture is introduced into the growth vessel 4 of the modular photobioreactor 1. The growth vessel is filled with the solution containing the algal culture to approximately 60 to 90% of its total volume.

The light sources 30 located inside the inner cylinder are switched on and off to obtain a technologically suitable lighting cycle using a light change controller 31. The light sources are switched on with a predetermined rhythm, for example 16 hours and switched off for 8 hours. Inside the outer cylinder is a solution containing the algae culture.

The solution containing the algae culture is continuously stirred by the rotation of the mixing blades 22 located in the culture vessel 4. By changing the rotation frequency of the mixing blades 22 using a drive, the intensity of the stirring is changed, which can be combined with adjusting the angle of inclination of the mixing blades 22, whereby increasing the angle of inclination intensifies longitudinal stirring and decreasing it intensifies transverse stirring.

The inner cylinder 18 is set to rotate, ensuring continuous mixing of the solution containing the algae culture. The flow of gas, including carbon dioxide (CO2), is accompanied by bubbling through the solution containing the algae culture, which also helps to intensify the mixing of the solution, as well as the adhesion of the algae culture to the inner cylinder 18.

The modular photobioreactor 1 has filter-equipped outlets through which the air in the reactor, and especially excess oxygen, exits, without letting outside air in, which is important to reduce or prevent the risk of contamination with other microorganisms. The concentration of dissolved oxygen and carbon dioxide (CO2) is controlled and regulated by an environmental control system located in the modular photoreactor.

Biomass samples are taken through a tube 21 connected to a biomass outlet 10 tap located below the growth vessel 4 of the modular photobioreactor 1. The biomass density is determined

based on a corresponding calibration chart, with a particle counter, by determining the optical density or visually by the density and color of the culture. When a certain density is reached, part of the culture is removed and replaced with fresh nutrient solution or, for example, wastewater. The extracted biomass is further processed to obtain the desired production.

Environmental parameters - pH, solution operating temperature, viscosity, CO2, nitrogen and phosphorus content, optical density - are monitored by the environmental process control system. The microalgae production process is controlled by the controller control system 16 based on input and output parameters, data from the mixing system, lighting system and environmental control system.

The invention allows to increase the efficiency of mass cultivation of photoactive microorganisms and thereby reduce the cost of the production process.

Claims (1)

1. The modular photobioreactor (1) comprises a modular frame (3) in which a closed growing vessel (4) is placed for accommodating the algae culture together with an algae culture inlet (9) and a biomass outlet (10) and a gas inlet (11) and outlet (12), a mixing system (13) with a drive, a lighting system (14), an environmental factors control system (15), wherein the growing space comprises two horizontal outer cylinders (17) and inner cylinders (18) of different diameters, located inside each other and on the same axis, and hermetically sealed ends (19) connecting the cylinders, characterized in that mixing blades (22) are attached to the rotating inner cylinder (18) of the growing vessel (4) by means of spokes (23) and fastening elements (24) for the purpose of making the algae mass mixing more efficient, and is equipped with a controller control system (16), wherein the modular frame (3) is equipped with connecting elements (5) for the modular photoreactors (1) for combining into microalgae production units (2) by placing the modular photoreactors (1) on top of each other, with the aim of increasing the efficiency of microalgae cultivation per unit area, and the angle of inclination of the mixing blades (22) is variable to ensure more effective mixing of the algae culture in the growth vessel (4) in all directions, both longitudinally and transversely