JPS5825486B2 - Isolation method for microscopic algae - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for separating microalgae, and more particularly to a method for separating microalgae from a dilute suspension in which microalgae have grown, particularly from a nutrient medium.

The separation method according to the invention is particularly suitable for concentrating suspensions of solid particles with a density close to that of the liquid phase and which has filter-clogging properties and/or semi-dough-like consistency). It is also suitable for concentrating suspensions of particles with

It also gives particularly satisfactory results when used to concentrate suspensions of fibrous or spiral microscopic algae, such as Spirulina or Oscillatoria species of algae.

In fact, some microalgae, and especially those of cyanophycs, such as Spirulina and C.
It is well known that certain species of the EEs) constitute an important source of protein and therefore have great advantages as a source of nutrition for humans and animals.

These microalgae are usually obtained in the form of a relatively dilute suspension in the natural or synthetic liquid nutrient medium in which they are grown.

These suspensions have, for example, an algae concentration of approximately 0.1 to 5 g/l (by weight of dry matter).

In order to make it possible to utilize these algae, they must first be separated from the obtained liquid medium, then their inorganic and/or organic components must be removed, and then they must be dried.

Taking into account the relatively low concentration of this algae, and taking into account the hardness of the algae contained, which tends to clog filters, these suspensions can be directly filtered using conventional filtration equipment. It cannot be filtered.

Therefore, when using devices such as vacuum drum lacrimers or pressure filters, a filtration surface that is too large for use on an industrial scale is required.

One solution to make it possible to carry out filtration of these suspensions under satisfactory conditions is to
There is a method of subjecting these suspensions to a preconcentration operation.

At the end of this operation, a more concentrated suspension can be obtained which can be filtered by conventional techniques.

Regarding this point, the present applicant has issued Patent No. 1066022 (
In Japanese Patent Publication No. 56-5513), it was shown that it is possible to preconcentrate a dilute suspension of microscopic algae by filtration.

However, in this case it is sufficient to prevent the suspension to be concentrated from coming into contact with the filter surfaces used and to prevent sticking or even formation of a filter cake on these filter surfaces, which could make it impossible to continue the operation. Provided that this operation is carried out in such a way that the suspension has a certain kinetic energy.

In the above-mentioned patent, the applicant has also proposed several preconcentrators which satisfy the above-mentioned conditions in their principle of operation.

The object of the invention is to provide a method for the separation of dilute suspensions, which allows the treated suspension to be concentrated to a large extent and with a high yield.

The present invention is a method for separating microalgae having a size of 10 to 1000 microns from an aqueous suspension having an algae concentration of 0.1 to 5 g/l on a dry weight basis. The first step is to concentrate the cloudy liquid and form a muddy cake.
process and the slurry cake obtained in this first step
a second step of forming an algae cake by filtration with a filter surface having numerous pores of 0.00 micron in size;
In a method for separating microscopic algae, which comprises a third step of washing the algae cake obtained in the step with water, and a fourth step of drying the cake obtained in the third step, the aqueous suspension is removed in the first step. The dry weight of the suspension is 5-60jj/l! A cylindrical drum that rotates around an axis and is arranged at an angle of, for example, 0.3 to 5 degrees with the axis slightly inclined to the horizontal direction, in order to concentrate the algae to a concentration of A cylindrical drum with a rigid cylindrical wall supporting a p-cloth held in the concave wall and having uniformly sized holes throughout in the range of 20 to 100 microns; The use of a rotating drum type filtration device consisting essentially of a supply pipe for the suspension to be concentrated running close to one end and two separate collecting tanks for collecting the filtrate and concentrate. and the flow rate of the suspension to be introduced into the cylindrical drum and concentrated;
The concentration reaching the filtration surface is set at 1 to 25 m3 of suspension per hour per m' of filtration surface, and the rotation speed of the same drum is set at a linear velocity of 0.05 to 3 m/s of the cylindrical wall. The slurry to be filtered is prevented from forming or adhering to a cake that would cause clogging on the same surface, and then the filtrate and the concentrated slurry introduced to the lower end of the drum are respectively collected into a collecting tank that receives them. This is the method to do so.

First, the apparatus used in the separation method according to the present invention will be explained.

Generally speaking, the apparatus used in the method of this invention includes:
It consists of a rotating drum-type filter, into which the suspension to be concentrated is continuously introduced, the rotation of which moves the suspension preventing the filter cake from sticking to the filter surface or In order to prevent the formation of such cakes, and in particular when processing suspensions of microalgae, it is possible to easily recover the condensed slurry resulting from the operation and to e.g. It is considered that the data can be sent to other processing bands such as

FIG. 1 is a front view showing an apparatus used in the method of the present invention.

2 is a cross-sectional view through the axis of the cylinder shown in FIG. 1; FIG.

FIG. 2A is a sectional view taken along line A-A in FIG. 2.

In the apparatus used in the method of the present invention, the main body of the so-called filter is composed of a hard cylindrical wall 1 with small holes made of a hard grid or a steel plate perforated with a high aperture ratio. It is a cylindrical drum.

One bottom side of this cylindrical drum is closed by a disk 2, in the center of which there is a circular hole through which a shaft 3 is passed, and the drum is firmly fixed to the shaft 3, for example by means of a arm 4 and a ring 5. has been done.

The other bottom side of the drum is partially closed by an annular drain 6 which is firmly attached to the edge of the cylindrical wall 1.

The end of this drum also comprises two frustoconical baffles 7.8 fixed to the edge of the cylindrical wall 1, one of the baffles 7, 8 in the forward direction and the other in the rearward direction. They are expanding in opposite directions.

The cylindrical wall 1 of the drum supports a furnace cloth 9 which is attached to the solid wall 1 in any suitable manner, for example by cords 10.

The cord 10 is wound helically around the drum and is secured to the drum at each end.

Also, a fine grid may be used instead of the code.

The opening size of the furnace cloth depends on the shape and size of the particles present in the suspension concentrated using this device, but it is between 20 and 10 mm.
It may be 0 micron.

The furnace cloth may be made of synthetic fiber cloth, such as nylon or polyester fibers, among others, and may also be made of stainless steel.

The drum-type filter, which rotates around the coaxial shaft 3 via the shaft 3, is configured as described above, and is tilted slightly with respect to the horizontal plane, for example, by an angle α of 0.3 to 5°. , and is inclined upwardly on the side of the bottom of the drum where the shaft 3 is closed by the disk 2 (in order to clearly represent the inclination, the inclination of the drum is not shown in Figs. 1 and 2). I exaggerated it).

The apparatus used in the method of the present invention also has a thin tube 11 for supplying the suspension to be concentrated.
1 leads into the interior of the drum, preferably close to the disk 2.

This thin tube 11 may be fixedly provided, for example parallel to the axis 3 of the drum.

The apparatus used in the method of the invention also comprises a collection tank 12 located below the drum for receiving the filtrate, and a concentrate recovery tank 13 located below the baffle plate 7.

The apparatus used in the method of the invention has a pressurized liquid supply pipe 14 disposed along the cylindrical wall 1 for cleaning the furnace cloth 9, which supplies the cleaning liquid through the furnace cloth 9. It can be placed inside the cylindrical wall 1 or outside the solid wall 1 and above the solid wall 1, depending on whether it is passed in the direction in which the filtrate passes or in the opposite direction. Good too.

Furthermore, the apparatus used in the method of the invention is equipped with all the apparatus necessary for its operation, in particular a motor for ensuring the rotation of the drum, a support for holding the shaft 3 and rotating it, and a bearing stand. Needless to say, there are.

A pump that ensures the supply of the suspension to be concentrated to the capillary tube 11 and the supply of cleaning liquid to the pipe 14, as well as a gate valve that interrupts the various supply streams and closes the discharge conduit of the collection tank 12 and the recovery tank 13. equipped in the same way.

Of course, various modifications of the above-mentioned device can also be considered.

Next, a method for separating microscopic algae according to the present invention will be explained.

The suspension for concentration to which the device with the above configuration is applied is generally a dilute suspension of solid particles with a density close to that of the liquid phase, or
or suspensions with filter-clogging properties and/or semi-dough-like consistency).

This is, for example, wastewater from purification plants, wastewater from the chemical industry or the paper industry.

This also applies to suspensions of microorganisms such as plankton or microscopic algae.

The particles present in these suspensions are e.g.
000 microns in size, with many ranging from 50 to 400 microns.

In this invention, the case of dilute suspensions of microscopic algae, e.g. Especially mentioned.

Spirulina algae generally have helices of about 200-400 microns in length made up of helices of about 20 microns in diameter.

The algae are elongated fibrils about 200-400 microns long.

Hormidium, some species of the order Hormidales, such as Ulothrix.
Mention may also be made of other filamentous algae such as Stigeoclonium (Ulotorichales) or Steigeoclonium (
Mention may also be made of certain Chactophoracees such as Stigeoclonium.

Generally, the suspension concentrated by the method of this invention is
Approximately 0.1 to 40 g of dry matter per 11, preferably 0.4
(may have a particle concentration of ~10 g).

In the case of microalgae, the suspension to be concentrated removed from the culture tank generally has a concentration of 0.1 to 5 g dry matter per 11.

The opening size of the oven cloth is selected depending on the size and shape of the particles contained in the suspension to be concentrated.

By way of example, for treating suspensions of Spirulina algae or Eureka algae, it is advantageous to use oven cloths with a mesh size of 20 to 100 microns.

The suspension to be concentrated is passed through the capillary 11 under a flow rate of usually 1 to 25 m3 per hour per filtering surface d, depending on the nature of the particles, their shape, size and their initial concentration in the suspension.
is introduced into the drum through.

The drum rotates around its axis 3 at a speed that is not excessive.

This is to avoid centrifugal forces acting on the suspension forming a thickened cake that sticks to the oven cloth.

A suitable rotational speed is preferably such that the filter wall is moved at a speed of about 0.05 to 3 m/s, more preferably 0.3 to 1.5 m/s.

The suspension thus introduced into the drum is subject to an upward force due to the rotation of the drum, and a downward force due to gravity, which prevents the suspension from being carried at the same speed as the drum. I can escape.

It is because of the velocity difference between the oven cloth 9 and the suspension contacting it that sticking of the filter cake on the oven cloth or even its formation can be avoided.

Moreover, because the drum is slanted, the concentrated suspension that collects along the bottom of the drum passes through the annular outlet 6 and into the baffle plate 7.
It flows into the recovery tank 13 along the line.

The furnace liquid passing through the furnace cloth 9 flows into the collection tank 12 , the baffle plate 7 directs the flow of the concentrated slurry toward the recovery tank 13 , and the baffle plate 8 directs the flow of the filtrate toward the collection tank 12 . It is designed to encourage people to

The deposition of particles on the oven cloth is prevented by the swirling movement of the suspension when it comes into contact with the oven cloth 9, but it is necessary to wash the oven cloth 9 by injecting pressurized liquid.

This injection is applied to the cylindrical wall 1 of the drum, whether inside or outside the drum.
This is done using a cleaning pipe 14 located along the top of the cleaning pipe.

The cleaning liquid may be water, but it may also consist of a portion of the filtrate that is collected in the collection tank 12, pumped again, and sent to the cleaning line 14.

The latter case constitutes an advantageous variant of the method according to the invention.

Whatever the nature of the cleaning liquid used, the cleaning of the oven cloth 9 can be intermittent or continuous and can also be carried out at least partially during the concentration operation. can.

Also, when cleaning the furnace cloth is carried out in the opposite direction to the way the filtrate passes, i.e. from the outside to the inside of the drum, less of the cleaning liquid mixes with the suspension being processed after it traverses the cloth. In some cases, it is possible to try to partially avoid both.

This may be the case, for example, if the cleaning liquid is different from the suspension;
Or, more generally, if one wishes to avoid supplementary dilution of the suspension.

In this case, as an advantageous second variant of the method according to the invention, it is also possible to arrange a fixed channel-shaped collector 15 inside the drum opposite the cleaning line 14 to collect a portion of the cleaning liquid. good.

This fixed collector 15 allows the washing liquid to be discharged separately from the suspension liquid.

In addition, if it is desired to increase the turbulence of the suspension to be concentrated by contacting the furnace cloth 9, a plurality of baffle plates 16 connected to the cylindrical wall 1 of the drum may be arranged in the length direction inside the drum. may be considered, which constitutes an advantageous third variant of the method according to the invention.

As described above, according to the method of the present invention, a large amount of suspension,
For example, 1 to 25 m per 1 d of filtration surface per hour.
3 to form a concentrated suspension in high proportions, e.g.
It is possible to obtain 25 times or more.

In particular, from a dilute suspension of microalgae having a density of about 0.1 to 5 grams of dry matter per 11, a concentrated surach having a density of about 5 to 60 grams of dry matter per 11 can be obtained.

Moreover, the concentrated slurry can then be filtered using conventional equipment.

One of the advantages of the method according to the invention is that a large amount of suspension can be processed with a relatively small space requirement.

Thus, for example, in an industrial facility where it is desired to process suspensions at flow rates of up to about 5 CJrrt/hour, the filtration surface may, for example, be about IO? It is preferable to use a 7I'' device.

Such a surface can be obtained, for example, with a drum having a length of 2 to 377 L and a diameter of about 1 to 1.5 m.

Example 1 A rotary drum-type filter is used, equipped with a nylon fiber cloth with a mesh size of 40 microns and a surface area of 8 m'.

The rotational speed of the drum, which is inclined at an angle of 3° to the horizontal plane, corresponds to a linear velocity of 0.4 m/s of its cylindrical wall.

The suspension to be concentrated consisting of a suspension of Spirulina algae with a dry matter concentration of 2 Vl was fed at a flow rate of 24 m'/h (i.e. 3
m°/h/m' furnace cloth) into the drum.

At the outlet of the filter, a concentrate with a dry matter content of 20 g/l is collected in a collection tank.

Example 2 A rotary drum concentrator equipped with a nylon fiber oven cloth with a mesh size of 40 microns and a surface area of 1 d was heated to a dry matter concentration of 4.
Suspension of Spirulina algae with Vl in culture medium at 4 m°
Introduce at a flow rate of /hour.

The drum, inclined at an angle of 3° to the horizontal plane, rotates at such a speed that its cylindrical wall has a linear velocity of 0.6 m/s.

The concentrate collected has an algae content of 19 g/l by weight of dry matter.

Example 3 Example 2 is repeated, but with a dry matter concentration of 3 g/l
3.5. A flow rate of t7 hours is introduced into the filter.

The concentrate collected has an algae content of 21.5 g/IJ by dry weight.

Example 4 Example 2 is repeated, but with a dry matter concentration of 0.8 g
The initial suspension having a volume of 1/73 is introduced at a flow rate of 16.5 m3/h.

The concentrate obtained has an algae content of 16 g/l by weight of dry matter.

Example 5 Example 2 is repeated again, but with a dry matter concentration of 0.3
The suspension to be concentrated with 9/l is introduced at 2077+"/h.

The linear velocity of the tear wall of the drum is 0.5 m/sec.

The concentrate obtained has an algae content of 4.8 g/l by weight of dry matter.

EXAMPLES In this example, a slurry suspension from an industrial wastewater treatment plant is concentrated.

The suspension to be treated has a dry matter concentration of 5 g//l.

At a flow rate of 577 I''/hour, this suspension is introduced into a rotary concentrator with a diameter of 0.50 m equipped with a 1 m2 oven cloth made of 60 micron nylon fibers.

A drum tilted at an angle of 3° to the horizontal plane has its p
Rotate at such a speed that the retreating wall has a linear velocity of 0.6 m/s.

The concentrate obtained has a dry matter content of 25 g/l.

This can be introduced into a vacuum drum type filter.

Example 7 When Example 6 is repeated with a flow rate of 3 m/hour, 43 g/hour is obtained.
A concentrate with a dry matter content of 1 is obtained.

This can be used to feed pressure filters.

The embodiments of this invention are listed as follows.

(1) The main body is a cylindrical drum that rotates around an axis and has a hard cylindrical wall with small holes that supports a furnace cloth that is attached to the wall and has openings of appropriate size, leading to the inside of the drum. In a concentration device including a thin tube for supplying a suspension to be concentrated, a cylindrical drum is arranged with its axis slightly inclined with respect to the horizontal plane, and the thin tube for feeding is arranged at an angle above the drum. A method for separating microscopic algae using a dilute suspension concentrator characterized in that the device passes close to the edge of the suspension.

(2) The method according to (1) above, characterized in that the axis is inclined with respect to the horizontal plane at an angle of 0.3 to 5 degrees.

(3) Any one of (1) to (2) above, wherein the furnace cloth has openings with a size of 20 to 100 microns.
One method.

(4) an annular drain opening in which the lower end of said cylindrical drum connects to the edge of the cylindrical wall of the drum, one in front and the other in said cylindrical drum;
(1) to (3) above, characterized in that one is provided with two baffle plates in the shape of a truncated cone, which open in opposite directions at the rear and are connected to the edge of the cylindrical wall; Method according to any one of the following.

(5) The method according to any one of (1) to (4) above, characterized in that it also contains a collection tank for concentrated suspension located below the lower end of said drum.

(6) The above (1) to (5) is characterized in that it also includes a cleaning pipe located along the cylindrical wall of the drum.
).

(7) The method according to (6) above, characterized in that the cleaning pipe is located outside the drum and above it.

(8) The above-mentioned (
7) method.

(9) Any of the above (1) to (8), characterized in that the drum also has at least one baffle plate located inside the drum and vertically attached to its cylindrical wall. 1
One method.

(10) feeding the suspension to be concentrated into a device according to one of the above (1) to (9), in order to obtain a concentrated suspension and, separately, to obtain a lachrymal fluid; Method for concentrating dilute suspensions.

(11) 1 to 25 rI per hour per 1i of filtration surface
introducing said suspension to be concentrated at a flow rate of L' and rotating the drum at such a speed that its cylindrical wall moves with a linear velocity of 0.05 to 3 m/s. The method according to (10) above.

(12) The drum has a cylindrical wall of 0.3 to 1.
A method according to said side, characterized in that it rotates at a speed such that it moves at a linear velocity of 5 m/s.

(13) The above (1) characterized in that the furnace cloth is washed by passing the liquid in the direction opposite to the direction in which the filtrate passes.
A method according to any one of 0) to 02).

(14) The above (10) to (12) characterized in that the furnace cloth is passed through the liquid in the direction of the filtrate to wash it.
Method according to any one of the following.

(15) The method according to any one of (13) to (14) above, wherein the cleaning liquid is water.

(16) Any one of (13) to (14) above, characterized in that the cleaning liquid consists of a part of the obtained offshore filtrate.
One method.

α-Force The above-described (
10) The method according to any one of (16).

(18) Substances that clog filters or have a consistency similar to semi-dough.
The method according to any one of (10) to (6) above, characterized in that a dilute suspension of particles with a size of 1000 microns is treated.

Process according to any one of the above-mentioned α-forces (18), characterized in that the treated suspension has a dry matter concentration of 0.1 to 40 g/l.

(20) The above-mentioned method based on α-copper, which is characterized in that a dilute suspension of microscopic algae having a size of 10 to 1000 microns is treated.

01) The method according to (20) above, characterized in that a dilute suspension of blue-green algae of Spirulina species or Yuremo species is treated.

(22) The method according to (20) above, characterized in that the algae suspension has a dry matter concentration of 0.1 to 5 gA.

Additional Relationship This invention is disclosed in Japanese Patent No. 1066022 (Japanese Patent Publication No. 56-5
No. 513), which is the first invention, "Method for isolating microalgae," shall be the main part of the essential matters for the constitution of this invention, and the same as the first invention above. The invention is an invention that achieves the purpose of the invention, and meets the requirements for an additional patent as stipulated in Article 31, Item 1 of the Patent Law.

[Brief explanation of the drawing]

FIG. 1 is a front view of the separation device used in the separation method according to the present invention, FIG. 2 is a sectional view passing through the axis of FIG. 1, and FIG. 2A is a sectional view taken along line A-A in FIG. 1. be. 1...Cylindrical wall, 2...Disc, 3...
...Axis, 6...Annular drainage port, 7, 8...
...Baffle plate, 9...Heart cloth, 10...
Code, 11... Thin tube for supplying suspension, 12...
...Filtrate collecting tank, 13...Concentrate recovery tank, 14...Washing piping, 15...Collector, 16...Baffle board .

Claims (1)

[Claims] 1. 0.1 to 5 g/l in dry weight! A method for separating microscopic algae having a size of 10 to 1000 microns from an aqueous suspension having an algal concentration of and a second step in which the slurry cake obtained in the first step is filtered through a filtering surface having numerous pores with a size of 10 to 100 microns to form a cake of algae. The third step is washing the algae cake with water, and this third step.
In a method for separating microscopic algae comprising a fourth step of drying the cake obtained in the step, the dry weight of the aqueous suspension is 5 to 60 g in the first step.
In order to concentrate the algae to a concentration of /11, it is rotated around the axis and the axis is slightly inclined with respect to the horizontal direction, for example, 0.3.
A cylindrical drum arranged at an angle of ~5°,
The rigid cylindrical wall is held in the enclosure and
A cylindrical drum supporting a furnace cloth with holes uniformly sized throughout in the range of 0.00 microns, and a cylindrical drum supporting a furnace cloth with openings of uniform size throughout, in the range of 0.00 microns, and a suspension to be concentrated running inside the drum close to its high end. Using a rotating drum type filtration device consisting essentially of a feed pipe and two separate collecting tanks for collecting filtrate and concentrate, into which the suspension to be concentrated is introduced. The flow rate of
The suspension is set at 1 to 25 m' per hour per m' of the filtration surface, and the rotational speed of the same drum is set at a linear velocity of 0.05 to 3 m/s of the cylindrical wall to reach the filtration surface. The suspension to be concentrated is prevented from forming or adhering to a cake that would cause clogging on the same surface, and then the filtrate and the concentrated slurry led to the lower end of the drum are respectively collected in collecting tanks that receive them. A method characterized by: