CH636640A5 - Gas exchanger for fermenters - Google Patents

Description

The invention relates to a mechanical gas exchanger for fermenters, which has a rotor with a hollow shaft and which is arranged in a fermenter tank filled with fermenter content.

Carrying out aerobic fermentations, e.g. the production of feed yeast from the whey substrate is accompanied by intensive foaming. This is so pronounced that the fermenter tanks can only be filled to 30-40% with liquid. Process engineering conditions have to be created in order to establish a balance between foam formation and foam breakdown, the cell multiplication taking place essentially in the foam phase.

If the foam formation becomes too intense, either chemical foam damping agents or mechanical foam separators must be provided. Since chemical anti-foaming agents can cause undesirable and uncontrollable changes in the biological system, mechanical foam separators are mostly used, although they require considerable equipment.

With known foam separators, which are arranged on the lid of the fermenter tank, the foam created by the fermentation process is liquefied by rotating disks and flung against the wall of the fermenter tank (Kieler Milchwirtschaftliche Forschungsberichte, 27/1975 / p.12). The liquid then sinks to the bottom of the fermenter tank, where it is brought into contact with the air taken in. This speeds up the fermentation process and the fermenter content rises again with the formation of foam. The foam separator therefore sets the fermenter contents in a circular motion.

The gas generated during fermentation is released when the foam is destroyed by the rotating disks of the foam separator and exits through the hollow shaft carrying the disks.

In many fermentation processes, intensive foam formation should occur on the one hand, because then the (inner) gas exchange of the cells in the extended boundary layers is facilitated and the production of the desired biomass is thus maximized. On the other hand, the residence time of the foam in the fermenter should not be too long because the gas exchange is getting worse due to changes in the interfaces. It is therefore desirable to conduct gas formation and gas exchange in the fermentation process in such a way that foam formation is optimal.

With regard to this optimization task, the gas exchanger according to the invention is characterized in that the rotor is enclosed by a tube system which has bores for introducing oxygen.

This arrangement has the advantage that the “external” gas exchange, that is the inflow of oxygen-containing air and the outflow of carbonic acid into the atmosphere, can take place within a short distance of the entire cycle path of the fermenter content in the fermenter tank. Such an arrangement, referred to as a “gas exchanger”, can simultaneously minimize the size of the fermenter tank and maximize the yield of biomass. In addition, only a single rotating system is required instead of an additional rotary aerator.

The distance of the tube system from the rotor is preferably so great that the fermenter content thrown off the rotor has a liquid state at the operating speed of the rotor when the tube system is reached.

The hydrodynamic principles apply to this design case, and the gas exchanger then also has the smallest possible dimensions.

In another preferred embodiment, the bores of the tube system are arranged at the location of the narrowest passage for the fermenter content in the tube system. As a result, the speed of the fermenter content passing through the tube system, which preferably has again assumed the properties of a real liquid at this point, can be very high, so that the resulting negative pressure can also become very large at this point. This supports the entry of oxygen in the fermenter content. Depending on the consistency of the fermenter content, this can even lead to the fact that a separate unit is unnecessary for the oxygenation.

A further improvement of the arrangement can be achieved if the speed of the rotor can be changed. As a result, the gas exchanger can be adapted to the respective consistency of the fermenter content and its dimensions such that the fermenter content thrown off by the rotor is just liquid when it reaches the tube system. This means that even with fermenter contents with a consistency that changes over time, optimum operating conditions of the fermenter can be achieved by regulating the speed.

A change in the relative arrangement of the rotor and the tube system with respect to one another can also serve the same goal, since this can achieve special circulation effects.

In a further improvement, nozzles for discharging fermenter content can be provided in the vicinity of the tube system, because in this way the circuit of the fermenter content can be freed from unnecessary ballast.

An embodiment of the invention is explained below with reference to the drawing. The drawing shows:

Fig. 1 shows a longitudinal section through a fermenter tank and

Fig. 2 shows a cross section through a gas exchanger.

In Fig. 1, a hollow shaft 2 is provided which is driven by a motor 1 and on which conical rotor disks 2 are arranged with the tip pointing upwards. A tube system 4 with bores 10 surrounds the rotor 2-3 and is at the top

2nd

s

10th

15

20th

25th

30th

35

40

45

50

55

60

65

3rd

636640

with a baffle 6, closed at the bottom with a baffle 5.

The tube system 4 can, as shown, consist of vertical tubes or instead of a helical tube. The system 4 is charged with oxygen via a distributor 9 and a feed line 8. The exhaust gas is discharged from the hollow shaft 2 via a pipe connection 7. The gas exchanger thus constructed is arranged on a lid 11 which is connected to the fermenter tank 12.

In Fig. 2, which shows a section through the gas exchanger according to Fig. 1 at the level of section line A-B, the tube system 4 is shown with its bores 10 at the narrowest point of the passage for the fermenter content removed by conical discs 3. The tube system 4 is fed through the distributor 9. The bores 20 of the hollow shaft 2 absorb the exhaust gas from the foam bubbles destroyed by the rotor disks 3 and discharge it to the outside through the hollow core of the hollow shaft 2.

B

2 sheets of drawings

Claims (6)

636 640 PATENT CLAIMS 1. Mechanical gas exchanger for fermenters, having a rotor (2, 3) with a hollow shaft (2), which is in a fermenter tank (12) filled with fermenter content is arranged, characterized in that the rotor (2, 3) is enclosed by a tube system (4) which has bores (10) for introducing oxygen. 2. Gas exchanger according to claim 1, characterized in that the bores (10) of the tube system (4) are arranged at the location of the narrowest passage for the fermenter content in the tube system (4). 3. Gas exchanger according to claim 1, characterized in that the speed of the rotor (2,3) is variable. 4. Gas exchanger according to claim 1, characterized in that the relative arrangement of the rotor 2), 3 and tube system (4) to one another can be changed. 5. Gas exchanger according to claim 1, characterized in that it has nozzles for discharging the fermenter content. 6. The method for operating the gas exchanger according to claim 1, characterized in that the speed of the rotor (2, 3) is chosen so high that the fermenter content thrown off by the rotor reaches a liquid when the tube system (4) arranged at a distance from the rotor is reached Condition.