FI65799C - FERMENTOR I STOR SCALE - Google Patents

Description

1 65799

The present invention relates to a multi-block fermentor comprising a tank, means inside the tank for dividing the tank into several blocks, means at the top of the tank for feeding the fermentable substance to the tank, a plurality of agitator shafts each having a plurality of mixing means for mixing the fermentable medium without to the substance, means for removing liquid and mass from the bottom of the tank and means for removing gas from the top of the tank.

The aerobic fermentation process can only be performed in a two- or three-phase reactor. The main problems of the prior art have been e.g. scale up difficulties and especially the risk of dead space formation at high broth viscosity values. Likewise, continuous mixing of gas and liquid and maintenance of dispersion are difficult to implement.

Many technical problems have led to numerous different fermenter solutions. An extensive summary of the prior art is given in Schtigerl, K .: "Neue Bioreaktoren fiir Aerobe Prozesse", Chem.-Ing.-Tech., 52 (1980) 12, 951.

Known fermenters can be divided into three basic types according to the mixing method: - pneumatically mixed fermenters (mixing with compressed gas discharged into the liquid) - hydrodynamically mixed fermentors (mixing with a liquid flow provided by a separate pump) - mechanically mixed fermenters (mixing with a rotary mixer in the tank).

Pneumatically agitated fermenters have the disadvantage of foam problems because the escaping gas can rise through the liquid in large bubbles without being dispersed in the liquid, forming 2,65799 of foam.

A dead space is easily formed in the tank if the viscosity of the fermentable liquid is high. Mixing of the liquid can occur poorly because the gas may be channeled and thus flow rapidly through the liquid. The efficiency of oxygen use with this structure is low. Pneumatically stirred fermentor. operating costs are also high.

In their hydrodynamically stirred fermenters, dead space can easily form in the tank if the viscosity is high. In this case, only a part of the liquid flows under the action of the pump when the part is almost stationary. During pumping, the liquid has to flow through the pump, which can easily break the fermentable cell.

In mechanically stirred fermenters, it is generally difficult to implement scale up, i.e. increasing the volume of the tank. This same problem also applies to the other types mentioned.

The division of the fermenter into blocks on a uniform horizontal flat plate is known per se (Schiigerl, see above), but the structure of these known fermenters is very complex and / or they have the above-mentioned scale up difficulties.

It is also known that scaling the mixing tank while maintaining geometric uniformity is technically impossible and that it is advantageous for large mixing tanks to use a multi-axis mixing system (Laine, J .: "Fluid Flow and Gas Dispersion in Stirred Tank Reactors", Dissertation, Helsinki University of Technology, Espoo -Finland, 1981).

The invention is characterized by what is set forth in the characterizing part of claim 1.

3,65799

According to the invention, the above disadvantages are avoided by dividing a large fermenter tank into several blocks by cell-like flow control levels, so that successive blocks are formed in the tank, the levels between which control the flow of liquid and gas from one block to another, and each block is equipped with several mixing axes.

The invention is described in more detail below with reference to the accompanying drawings, in which: Figure 1 shows a vertical section of a preferred embodiment of the invention, Figure 2 shows a cross-section of the same embodiment, and Figures 3a-3c show perspective views of some embodiments of flow control levels.

Figure 1 shows a cylindrical tank forming the main body of the fermenter, indicated by the reference number 1. The tank 1 has several agitator shafts 2. At their ends are drive motors 3 and each shaft 2 has several agitator members 4. The air distribution ring 5 is located at the bottom of the fermentor and its air nozzles 6 is mounted so that one nozzle is below each agitator member 2. If necessary, the lower part 7 of the fermenter 1 can be a so-called unmixed separation space. The fermenter has one or more flow control levels 8 mounted in such a way that the liquid space 9 above the uppermost level is substantially larger than the other liquid spaces. The intersections 10 of the planes 8 and the agitator shafts 2 can be used as bearing points for the shafts 4. In the tank 1 there is a broth inlet 11 in the upper mixing block 9 and broth outlet and / or return connections 12 and 14 in the lower block 7. The air is supplied by a pneumatic ring 5 and the gas is removed from the uppermost block 9 of the fermenter 1 via a pipe 13.

The flow control levels 8 (Fig. 2) have holes or openings evenly distributed over the entire area of the plane. The area of the holes or openings 4 65799 is substantially larger than the cross-sectional area of the broth inlet tube. The holes or openings in the plane 8 can be either vertical or oblique, but not so inclined (max. 45) that gas locks could be formed.

The function of the levels is to act as controllers of gas and liquid flows. Gas enters through the holes or openings in the levels and liquid and biomass down. Due to the mixing and leveling solution of the fermenter, the flows above and below the levels are almost horizontal. The planes are therefore thick (deep) so that these upstream and downstream flows do not mix with each other. The thickness of the planes can be, for example, about 50-200 mm and the diameter of the holes or openings can be, for example, about 10-50 mm.

The preferred structure of the planes has been described above, but may also have a different shape. For example, instead of the round holes shown in Figure 2, other shapes, such as oval or angular holes, can be used.

Figures 3a and 3b show schematically in perspective some of the flow control planes using 6-angled and rectangular cells, respectively, to form the plane.

Figure 3c is a perspective view of a section of a flow control plane in which the flow openings are round holes and in which the area of the openings is smaller than the area of the closed part of the plane.

The holes may also be asymmetrically distributed over the plane area, but the even distribution shown in Figure 2 is most preferred. By using intermediate levels, the flows of the system can be controlled so that an amount of gas and liquid approximately equal to their total supply passes through the holes or openings in the levels. With this procedure, the fermentor tank is divided into several mixing blocks connected in series, whereby the reactor volume required for a certain conversion is reduced compared to a single-stage mixing reactor. In this case, it is preferred that the block into which the new liquid is fed has a volume of more than half of the total liquid volume. In this case, the first reaction step is sufficient to raise the conversion of the system so high that the so-called fermentor leach flow is not exceeded.

By using multiple vertical agitator shafts, the scale up technology of the system can be controlled substantially better than if the geometric uniformity of the tanks were maintained. By appropriately selecting the directions of rotation of the shafts, the horizontal mixing of the liquid and the gas can be enhanced. A multi-axis system also has a substantially better elimination of the risk of dead states in the system than a single-axis mixer system.

The multi-axis system can also eliminate the possibility of gas penetration.

As such, it is known that in a gas-liquid reactor, the shape of the gas distribution ring has no significant effect on the mass transfer properties of the mixing reactor. However, if the air supply port of a large fermentor is too large, the dynamic forces in the pneumatic ring and the lower agitator member may become unreasonable. Therefore, a multi-axis agitator system is also advantageous in terms of vane distribution, since in this case the air can be divided into a few different points - preferably one air supply point for each agitator axis below the axis.

Placing the unmixed space below the lowest level causes this to act as a separation space in which the microbial mass and the carrier broth are rapidly deposited. In this case, it is possible to return the carrier to the beginning of the process without separate separation equipment, if necessary. In this case, in some special cases, a significant improvement in the quality and / or quantity of the product to be fermented can be achieved.

Claims (5)

65799 A multi-block fermentor comprising a tank (1), means inside the tank for dividing the tank into a plurality of blocks, means (11) at the top of the tank (1) for feeding the fermentable substance to the tank, a plurality of agitator shafts (2) each means (4) for mixing the substance to be fermented, means (5) for supplying air to the substance to be fermented, means (12) for removing liquid and pulp from the lower part of the tank (1) and means (13) for removing gas from the upper part of the tank (1) the blocks have cellular levels (8) which allow the flow of fermentation liquid and gas and act as flow controllers between the blocks. Fermenter according to Claim 1, characterized in that the tank (1) is divided into successive blocks in the height direction, the liquid space of the uppermost block (9) being substantially larger, preferably more than half the total liquid volume of the tank. Fermenter according to Claim 2, characterized in that the agitator shafts (2) are substantially vertical and in that each agitating shaft (2) has at least one agitating element (4) in each agitating block. Fermenter according to claim 3, characterized in that the means for supplying air to the tank (1) comprise an air distribution ring (5) provided with nozzles (6) and in that there is a nozzle (6) below each agitator shaft (2). Fermenter according to Claim 1, characterized in that the holes or openings in the honeycomb planes are evenly distributed over the entire area of the plane.