Method and separator for concentrating algea biomass

Abstract

The invention relates to a separator (105) for separating a phase with floating solids from a liquid, wherein the separator (105) has a rotatably mounted drum (11) for a centrifugal separation of the suspension, the drum (11) has an inlet tube (1) which opens into a distributor (2), the drum (11) has a plate insert (3) which occupies a separating chamber (16) within the drum (11), and the drum (11) has a collecting chamber (15) for collecting a light phase, said collecting chamber being arranged between the distributor (2) and the separating chamber (16), wherein the volume of the collecting chamber (15) equals at least 17% of the volume of the separating chamber (16). The invention also relates to a method for concentrating an algae biomass.

Description

[0001] METHOD AND SEPARATOR FOR CONCENTRATING ALGAE BIOMASS

[0002] The present invention relates to a process for concentrating a fermentatively produced microalgal biomass, preferably in the context of obtaining an omega-3 fatty acid-rich liquid from a microalgal suspension, by means of a suitable centrifugal separator.

[0003] The fermentative production of microalgae holds great potential for feeding future generations. A typical algal species used for this purpose is Schizochytrium . This species can produce essential omega-3 fatty acids in large quantities. Furthermore, its production does not require any fertilizers or pesticides. Currently, individual valuable substances from algae are already being intensively used in the food industry. For example, binding agents in pudding, ice cream and yogurt and natural colorings originate from algae. Microalgae can also be used in the human diet as a source of omega-3 fatty acids. They therefore represent a resource-saving alternative to fish oil. Therefore, the concentration and automated processing of algae into algal oil is of interest to meet the growing global demand.However, due to their small density difference compared to the culture medium, algae are difficult to separate from it. Furthermore, microalgal cells have a small particle size and sometimes float on the culture medium, thus creating a risk of clogging during concentration, both in the case of centrifugal processing and filtration.

[0004] The common method involves cultivating microalgae in a fermenter until they have produced an oil content of approximately 20%. Since they would float above this level, and there is currently no suitable method for their industrial utilization as a light phase, current processes then interrupt growth and separate the algae from the culture medium in a separator, forming the heavy phase.

[0005] Based on the aforementioned prior art, the object of the present invention is to provide a centrifugal separator suitable for concentrating microalgae biomass, which is difficult to separate. Due to the ability of the separator described in the invention to separate microalgae as a light phase, the growth of the fermenter can be operated up to an algal oil content of approximately 40%. The present invention solves this problem by providing a separator having the features of claim 1 and a method for concentrating microalgae biomass having the features of claim 9.

[0006] A separator according to the invention serves to separate a phase with floating solids from an aqueous phase, wherein the centrifugal separator has, in a manner known per se, a rotatably mounted drum for centrifugal separation of the suspension.

[0007] The drum has an inlet pipe that opens into a distributor. The distributor can be arranged in sections as a hollow cone extension at the end of the inlet pipe.

[0008] The drum also features a separating disc insert, which occupies a separation space within the drum. This separating disc insert makes it possible to very efficiently remove even solids with a slight density difference compared to water. The separation space is defined by the size of the disc insert. It comprises the disc stack and the spaces between the discs.

[0009] The drum also has a collecting chamber for collecting a light phase, which is located between the distributor and the separation chamber. Such a collecting chamber is usually designed as a space as small as possible for draining the lighter liquid of a mixture that is directed radially inward. In the case of a three-phase separator, for example, this can be a near-axis drain for an oil phase.

[0010] In the special case of highly viscous solids with a lower density than the liquid, such as water, this space can become blocked. Therefore, the collection chamber must be designed with a larger volume, which actually contradicts the compact, conventional design of the separator, but prevents blockage of the discharge of the light phase in this type of mixture.

[0011] Accordingly, the volume of the collection chamber is at least 17% of the volume of the separation chamber and is therefore significantly more voluminous than conventional separators.

[0012] The separator is ideally suited for processing Aigen biomass, but can also be used for concentrating liquids and liquid mixtures with the special property of low-density solids, such as for separating kettle milk into whey and double cream cheese.

[0013] Further advantageous embodiments of the method according to the invention are the subject of the subclaims.

[0014] For efficient removal of a light phase with a particularly high solids content, the volume of the collection chamber can be more than 40%, and particularly preferably between 45% and 90%, of the volume of the separation chamber. This allows for particularly high clarification efficiency.

[0015] The separator plate insert typically comprises a plurality of separator plates, with the separator plates being spaced apart by tabs. The tab height for spacing two separator plates in the plate insert is 2.0 - 5.0 mm, preferably 4 mm + / - 0.2 mm. This comparatively large tab height prevents blocking within the plate stack.

[0016] The spacing can be achieved by elongated spacer bars or by point spacing. In particular, the plates are spaced by so-called longitudinal and / or point tabs. Typically, high-density solids collect in a radially outer sludge chamber beyond the plate stack. However, very low-density solids are passed through the plate stack into the collection chamber.

[0017] The average distance between the separation space and the distributor can advantageously be at least 5%, preferably 10%, particularly preferably 20-50% of the maximum extension of the drum, wherein the distance and the maximum extension lie on a common radial axis.

[0018] The separator can have a drum head with a regulating disc and a gripper chamber, so that the extracted light phase can be directed via the regulating disc into the gripper chamber located in the drum head, from where it can be further discharged. The regulating disc allows for adjustment of the flow rate in the outlet, so that the fill level of the collection chamber can preferably, but not necessarily, be adjusted independently of the backpressure in the discharge path of the light phase. Alternatively, the fill level can also be adjusted via the backpressure of the light and heavy phases of the system.The separator can be designed as a self-draining separator, as a self-draining nozzle separator or as a pure nozzle separator without self-draining function, which is preferably designed for continuous operation so that aigen biomass or other solid-liquid mixtures of the type described above can be processed on a large scale.

[0019] Alternatively or in addition to the gripper, the separator can have a fully hermetic or semi-hermetic product discharge, in particular as a liquid discharge.

[0020] In addition to a product supply line, which opens into the inlet pipe, for example, the separator can also have a gas supply line for introducing protective gas. The gas supply line can also open into the inlet pipe or be designed as a separate gas pipe located in the inlet pipe. A protective gas blanketing system introduced via the outlet is also possible, as is a protective gas blanketing system for the space surrounding the drum, formed by the concentrate catcher and hood.

[0021] Furthermore, the invention provides a method for concentrating an aigen biomass comprising the following steps:

[0022] A Providing floating algae suspended in an aqueous culture medium and

[0023] B Introducing this mixture into a separator according to the invention with centrifugal separation of a culture medium as a heavy phase from an aigen fraction as a light phase.

[0024] The aforementioned process can, in particular, be part of a process for extracting algal oil. Accordingly, the process according to the invention can be expanded by the following steps:

[0025] C Converting the algal fraction into a suspension with cell disruption and release of algal oil from the algae, preferably by means of a homogenizer; and

[0026] D Separating an algal oil-rich liquid phase from the algal suspension using a centrifugal separator, in particular a three-phase separator. At least in the aforementioned separation steps in steps A or D, a protective gas may be introduced into the drum of a separator. Particularly preferably, the entire sequence of steps AD can be carried out in a protective gas atmosphere. Since algae are sensitive to oxidation, a better result is achieved by introducing a protective gas.

[0027] After step B and / or after step C, preferably immediately after one or both of the two steps, the algal fraction or the algal suspension can be transferred to a cooled tank, preferably a tank equipped with a cooler and a stirrer. This reduces enzyme activity and also inhibits other degradation processes.

[0028] Following the separation of the algal oil-rich liquid phase in step D, further purification of the phase can be carried out to provide purified algal oil, in particular by oil polishing.

[0029] Preferably, the density of the acetic acid fraction separated in step A as a light phase is between 0.95 and 0.99 kg / dm3, preferably with a viscosity between 250 and 300 mPas at a temperature between 5 and 10 °C. These small density differences, especially when water is used as the culture medium, demonstrate the difficulty of the separation task. However, it has surprisingly been shown that this difficult separation task can be mastered using the aforementioned separator according to the invention.

[0030] The average particle size of the solids in the acetic acid fraction separated in step A is less than 100 pm, preferably between 6 and 18 pm. Nevertheless, a substantially particle-free culture medium can be separated in step A.

[0031] For optimal separation, the pH value of the algae fraction separated in step A is between pH 6-10.

[0032] Finally, the dry matter content of the acetic acid fraction separated in step A may be more than 25%, preferably 30-33%.

[0033] Further advantages, features, and details of the invention will become apparent from the following description, in which several embodiments of the invention are explained in more detail with reference to the accompanying figures. Those skilled in the art will conveniently consider the features disclosed in the figures, the description, and the claims individually and combine them into useful further combinations. They show:

[0034] Fig. 1 schematic representation of a process diagram of a method according to the invention using a separator for the centrifugal processing of an aigen suspension;

[0035] Fig. 2 schematic sectional view of a first variant of a separator for the centrifugal processing of an aigen suspension in the context of a method according to the invention.

[0036] In a first step 101, an algae suspension is prepared. A so-called photobioreactor or a fermenter 102 can be used to produce or prepare algae. Floating algae can be produced from high-cell-density fermentation. If necessary, additional enzymes can be added to the fermenter.

[0037] The species Schizoschytrium sp., Crypthecodinium sp. and / or Ulkenia sp. are particularly preferred as potential microalgae for processing.

[0038] Initially, a solid-liquid separation 104 takes place in a separator with an internal collection chamber for the purpose of concentrating the light solid phase in the form of an algae concentrate. This enables, among other things, better subsequent processing with less foaming and / or emulsion formation.

[0039] The starting product before processing can be a suspension with floating algal biomass with a dry matter content of preferably 10 - 15%.

[0040] After concentration 120, a suspension 103 is formed with cell disruption in the homogenizer. During concentration in 105, a clear phase 106 is simultaneously separated, which is subsequently referred to as the culture medium.

[0041] The culture medium can, for example, be a liquid of defined composition from the photobioreactor / fermenter. The solids 107, referred to below as algal concentrate, in the form of a slurry, are temporarily stored as algal biomass in a tank 108.

[0042] The product data of the concentrated algal biomass are as follows: Density: 0.95 - 0.99 kg / dm3 Particle size: 6 - 18 pm pH: 6 - 10 TS of the biomass: 30 - 33 % Temperature: 1 - 20°C, preferably 2 - 15°C, particularly preferably 5 - 10 °C Viscosity: 250 - 300 mPas

[0043] From there, the algae concentrate is transferred to a homogenizer 109 for further cell disruption, in which, among other things, algal oil is released 119 from the solids, particularly the cells. In the homogenizer 109, the solids / microalgal cells are crushed and transferred into a suspension 110, releasing the algal oil.

[0044] The phase 114 can be recirculated as a partial stream before the homogenizer 109 if it still contains too many intact algal cells.

[0045] The phase 106 can be filtered and returned or recirculated to the photobioreactor or fermenter 102.

[0046] Oxygen-free processing is very important as protection against oxidation. Various protective gas blanketing concepts are available for the individual process steps.

[0047] After the separator 105 and after the homogenizer 109, a tank 108, 118 with cooling to a temperature of 5-10°C and with a controlled agitator can be arranged.

[0048] In tank 118 downstream of homogenizer 109, the pH can be adjusted to a pH of 4-6. Alternatively or additionally, NaCl can be added, e.g., to reduce the tendency toward emulsion formation.

[0049] Subsequently, the suspension 110 is heated 111 to more than 40°C, preferably more than 45°C, particularly preferably to a temperature between 50-60°C. This can be done, as shown in Fig. 1, by a heat exchanger 112, preferably by a plate heat exchanger.

[0050] The suspension is then processed in a separator 113 into three phases: an aqueous liquid phase 114, an algal oil phase 115, and a slurry-like solid phase 116. Due to the sensitivity of the algal components to oxidation, blanketing with protective gas is advantageous for at least this step or, if necessary, starting from the homogenizer 109. The obtained algal oil phase can then be further purified by an optional oil polishing 117.

[0051] The separation separator 105 is shown in detail in Fig. 2. The algae suspended in liquid are fed via an inlet pipe 1 into a distributor 2 of a drum 11 mounted for rotation about a vertical axis of rotation D. Furthermore, the separation separator 105 has a separation plate insert 3. This separation plate insert 3 defines a separation chamber 16, which is filled by the separation plate insert 3 with conical separation plates. The separation plate insert 3 has a stack of a plurality of separation plates and the spaces between the separation plates. The algae-liquid mixture enters the separation chamber via riser channels 6.

[0052] The upper part of the drum 11 has a drum head. Arranged in the drum head are a regulating disc 5 and a peeling chamber 7, 8 each for a heavy liquid phase, the culture medium, and optionally a light liquid phase in the form of concentrated, floating algae and already separated algal oil. The light phase is drained off via the regulating disc 5 and the gripper chamber 8 via a liquid drain 9 for the light liquid phase. The heavy aqueous phase 106 is withdrawn from the separation chamber 16 or the sludge chamber 14 via a separating plate 4 and drained out of the drum 11 via the gripper chamber 7 and a liquid drain 10 for the heavy liquid phase.

[0053] Furthermore, the drum 11 has radial nozzles 12 for discharging the algae from the drum 11, for example into a sludge collection container of a hood which surrounds the rotatably mounted drum 11.

[0054] The nozzles 12 can be emptied automatically. In the variant shown in Fig. 2, the nozzles 12 are opened and closed via an axially movable piston valve 13.

[0055] Between the nozzles 12 and the separation chamber 16 there is a sludge chamber 14 in which the solid phase collects before emptying.

[0056] A collecting chamber 15 is arranged between the separation chamber 16 and the distributor 2. This plate-free collecting chamber 15 serves to concentrate the light phase, which may contain algae. The special feature of the process according to the invention is an unusually voluminous collecting chamber 15 for the use of highly viscous natural products. This advantageously prevents clogging or blocking of the drum 11.

[0057] The size of the collection space can be changed as required by design measures, such as enlarging or reducing the recesses in the plate package adjacent to the distributor 2.

[0058] Recesses in the plate stack can be created either in segments located between the distributor's struts, onto which the plates are threaded. Or they can be created as a completely free area across the entire inner radius, if the struts of the distributor 2 are extended to the beginning of the plate stack or the separating plate insert 3.

[0059] The volume of the collection chamber is at least 17% of the volume of the separation chamber, preferably more than 40%, and particularly preferably between 45% and 120%. At 100%, the volume of the collection chamber 15 and the volume of the separation chamber are equal.

[0060] The outer wall of the drum 11 also has a conical shape in some areas, particularly in the area of ​​the drum upper part. The average distance of the separation chamber 16 from the distributor 2 is preferably at least 10%, preferably 20-50% of the total extension of the drum 11, with the distance and the total extension being measured in a direction parallel to the conical outer wall.

[0061] The volume of the collection space can be determined, for example, by querying the object properties in the 3D software Inventor from Autodesk.

[0062] An empirical value can be chosen as the average diameter for the collection chamber. A rough calculation can be made by dividing the chambers into solid cylinders and truncated cones, calculating the individual volumes, and subtracting them from each other.

[0063] In all these considerations, the volume of the ribs on the outside of the distributor neck can be neglected.

[0064] The tab height in the disc insert can advantageously be 2.0 - 5.0 mm, preferably 4 mm + / - 0.2 mm. Such tab heights are very unusual for disc separators and also facilitate separation in this case. The collection chamber of the separation separator with a collection chamber during the separation of the clarification medium arises from the observation that algae with a high oil content have a lower density than water and thus float on the aqueous clarification medium, where they can now be separated from the aqueous phase in a light phase. However, this light phase is heavily loaded with solids, which complicates drainage.

[0065] Therefore, a collection chamber close to the rotation axis was dimensioned particularly large to facilitate the collection of the light algae-containing fraction and the subsequent centrifugation of the culture medium.

[0066] The process shown here allows floating algae with an increased oil content to be efficiently separated from the culture medium.

[0067] Until now, the algal biomass floating after fermentation was not separated from the culture medium, but was enzymatically digested directly in the fermenter and the phases were then separated by means of 3-phase separation.

[0068] The advantages of the process shown here are higher oil yields, lower tendency to emulsion formation, lower volume flows and no use of enzymes.

[0069] These advantages were achieved through a purely mechanical process.

[0070] The highly viscous oil obtained in this process contains high amounts of omega-3 fatty acids. This can be used to produce dietary supplements and functional foods for a healthy human diet. Dosage forms range from oil to gastro-resistant capsules, softgel capsules, and algae powder as an ingredient in food production.

[0071] As can be seen from Fig. 2, ribs are arranged radially in the concentration chamber. These serve to lock the plates and carry the product. Within the scope of the present invention, the contour of the distributor can be modified such that the ribs have a turbine blade-like shape for better product conveyance, and also that the plates receive an additional, more fluidically optimized, inclined arrangement of the tabs. Reference numerals

[0072] 1 inlet pipe

[0073] 2 distributors

[0074] 3 Separator plate insert

[0075] 4 cutting plates

[0076] 5 Regulating disc

[0077] 6 Riser channel

[0078] 7 Peeling chamber {heavy phase)

[0079] 8 Peeling chamber (light phase)

[0080] 9 Liquid drainage (light phase)

[0081] 10 Fluid drainage (heavy phase)

[0082] 11 drum

[0083] 12 nozzles

[0084] 13 piston valves

[0085] 14 Mud room

[0086] 15 Assembly room

[0087] 16 Separation space

[0088] D axis of rotation

[0089] 101 Providing algae

[0090] 102 Photobioreactor / Fermenter

[0091] 103 Suspension formation

[0092] 104 Solid-liquid separation

[0093] 105 Separator with inner collecting chamber

[0094] 106 Clear phase / culture medium

[0095] 107 Solids / Algae Concentrate

[0096] 108 tanks

[0097] 109 Homogenizer

[0098] 110 Suspension

[0099] 111 Heating

[0100] 112 heat exchangers

[0101] 113 Separator

[0102] 114 aqueous liquid phase

[0103] 115 Algal oil phase

[0104] 116 mushy solid phase

[0105] 117 Oil polishing

[0106] 118 tanks

[0107] 119 Release of algal oil

[0108] 120 Concentration of floating algae

Claims

Patent claims 1. Separator (105) for separating a phase with floating solids from a liquid, wherein the separator (105) has a rotatably mounted drum (11) for centrifugal separation of the suspension, wherein the drum (11) has an inlet pipe (1) which opens into a distributor (2), wherein the drum (11) has a plate insert (3) which occupies a separation space (16) within the drum (11), and the drum (11) has a collecting space (15) for collecting a light phase which is arranged between the distributor (2) and the separation space (16), characterized in that the volume of the collecting space (15) is at least 17% of the volume of the separation space (16).

2. Separator according to claim 1, characterized in that the volume of the collecting space (15) is more than 40%, and particularly preferably between 45%-90%, of the volume of the separation space (16).

3. Separator according to claim 1 or 2, characterized in that the plate insert (3) has a plurality of separating plates (4), wherein the separating plates (4) are spaced from one another via tabs and wherein the tab height for spacing two separating plates (4) in the plate insert (3) is 2.0 - 5.0 mm, preferably 4 mm + / - 0.2 mm.

4. Separator according to claim 1, 2 or 3, characterized in that the average distance between the separation space (16) and the distributor (2) is at least 5%, preferably 10%, particularly preferably 20-50% of the maximum extension of the drum (11), wherein the distance and the maximum extension lie on a common radial axis.

5. Separator according to one of the preceding claims, characterized in that the separator (105) has a drum head with a regulating disc (5) and a gripper chamber (7), so that the derived light phase can be guided via the regulating disc (5) into the gripper chamber (8) arranged in the drum head.

6. Separator according to one of the preceding claims, characterized in that the separator (105) is designed as a nozzle separator, preferably as a self-emptying nozzle separator, which is preferably designed for continuous operation.

7. Separator according to one of the preceding claims, characterized in that the separator (105) has, in addition to a product feed line which opens into the inlet pipe (1), a gas feed line for introducing protective gas.

8. Separator according to one of the preceding claims, characterized in that the separator has a fully hermetic or semi-hermetic product discharge, in particular as a liquid discharge (9, 10).

9. Process for the concentration of aigen biomass characterized by the following steps: A Providing algae (101) suspended in an aqueous culture medium (106) and B introducing this mixture into a separator (105) according to one of the preceding claims with centrifugal separation of a culture medium (106) as a heavy phase from an aigen fraction (107) as a light phase.

10. The method according to claim 9, wherein the method further comprises the following steps: C converting the algal fraction into a suspension (110) by cell disruption with release (119) of algal oil from the algae, preferably by a homogenizer, (109); and D Separating an algal oil-rich liquid phase (115) from the algal suspension by a centrifugal separator (113), in particular a three-phase separator.

11. Method according to claim 9 or 10, characterized in that at least in at least one of steps A or D, protective gas is introduced into the drum of a separator (105, 113).

12. Method according to one of the preceding steps, characterized in that steps AD are carried out in a protective gas atmosphere.

13. Method according to one of the preceding claims, characterized in that after step B and / or after step C, preferably immediately after one or after each of the two steps, the algae fraction (107) or the algae suspension (110) is fed into a cooled tank, preferably into a tank with a cooling system and an agitator.

14. Method according to one of the preceding claims, characterized in that following the separation of the algal oil-rich liquid phase (115) in step D, a further purification of the phase takes place to provide purified algal oil, in particular by oil polishing (117).

15. Process according to one of the preceding claims, characterized in that the density of the acetic acid fraction (107) separated in step A as a light phase is between 0.95 - 0.99 kg / dm3, preferably with a viscosity between 250-300 mPas at a temperature between 5-10 °C.

16. Process according to one of the preceding claims, characterized in that the average particle size of the solids in the aigen fraction (107) separated in step A is less than 100 pm, preferably between 6 - 18 pm.

17. Process according to one of the preceding claims, characterized in that the pH of the acid fraction (107) separated in step A is between pH 6-10.

18. Method according to one of the preceding claims, characterized in that the dry matter content of the algae fraction (107) separated in step A is more than 25%, preferably 30-33%.

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