types of fermenter

TYPES OF FERMENTER

BYM.Vharshini

2ND YEARB.Sc. BMS

SYNOPSIS1. Waldhof fermenter2. Acetators and cavitators3. Tower fermenter4. Cylindro-conical vessels5. Air lift fermenter6. Deep jet fermenter7. The cyclone column8. Rotating disc fermenter

WALDHOF FERMENTER Yeast growth in sulphite waste liquor led to

the development of Waldhof fermenter. The fermenter was Carbon steel, clad in

stainless steel Diameter – 7.9m High-4.3m Central draught tube -1.2m in diameter Draught tube was held by tie rods attached

to the fermenter walls Operating volume—225,000dm3 of

emulsion(broth & air) and broth without air—100,000dm3

Non sterile air was introduced into the fermenter using the rotating – pin wheel type of aerator composed of open ended tubes rotating at 300 rpm.

The broth passed down the draught tube from the outer compartment which reduced the foaming.

ACETATORS AND CAVITATORS Fundamental studies on vinegar production

showed that: Acetobacter cells remain active in stirred

aerated fermenter , distribution of air had to be almost perfect within the entire contents of the vessel

The full-scale problem was solved by the use of self aspirating rotor— the turning rotor sucked air and broth and dispersed the mixture through out the rotating stator.

The aerator also worked without a compressor and was self-priming.

In Vinegar fermentation—foam & chemical antifoams are not feasible because they decrease aeration efficiency and quality of vinegar.

Therefore Mechanical defoamer was incorporated into vessels and as foam builds up it is forced into a chamber in which the rotor runs at 1,000 to 1,450 rpm.

Centrifugal force breaks the foam & separates it into gas & liquid.

The liquid is pumped back into the fermenter & gas escapes by a venting mechanism.

Uniform distribution of air bubbles was obtained by means of the circulation pattern created by the centrally located draught tube.

SELF –PRIMING AERATOR A- hollow body of

turbine B-openings radially

arranged C-verticle sheets D-stator E & F-upper and

lower ring on the turbine

G & H-upper and lower ring of stator

TOWER FERMENTOR An elongated non mechanically stirred

fermenter having the aspect ratio 6:1 for tubular sections and 10:1 for overall, through which there is a unidirectional flow of gases.

Simple tower fermenter are those with air sparger at the base ;used for citric acid production

This batch fermenter is in the form of glass column having a ht:diameter ratio of 16:1 and with a volume of 3dm3.

Humid sterile air was supplied through the base.

TYPES Single staged: e.g. Hall and howard’s

beer fermentor: water jacketed tubes of various dimensions inclined at an angles of 9ºto90º.

Intermediate staged: settling zones of various designs e.g. Shore et al’s beer fermentor. It has sectioned perforated plates for max. beer production

Multi staged: number of perforated vessels are used. e.g.Owen (1948) and victorero(1948) et al for brewing beer.

CYLINDRO-CONICAL VESSELS Used in Brewing of lager. First proposed by Nathan. The vessel consists of stainless steel

vertical tube with a hemispherical top & conical base with an included angle of approx 70 degree.

Aspect ratio—3:1 Fermenter Height—10 to 20m Operating volumes—150,000to

200,000dm3

Vessels are not normally agitated unless particularly flocculant yeast is used

Small impeller may be used to ensure the homogeneity when filling with wort.

In the vessel ,wort is inoculated with yeast and fermentation proceeds for 40 to 48hrs.

Mixing is achieved by the addition of carbon dioxide bubbles—rise rapidly in the vessel.

Temperature control is monitored by probes positioned at suitable points within the vessel.

A no. of cooling jackets are fitted to the wall to regulate & cause flocculation & settling of yeast.

The fermentation is terminated by the circulation of chilled water via cooling jackets which results in yeast flocculation.

Thus it is necessary to select yeast stains which will flocculate readily in the period of chilling.

ADVANTAGES OF THIS VESSEL IN BREWING:o Reduces process times —increased

movement within the vessels.o Primary fermentation and conditioning

carried out in same vessel.o The sedimented yeast—easily removed

since yeast separation is good.o Maturing time may be reduced by gas

washing with carbon dioxide.

THE CYCLONE COLUMN Dawson developed cyclone column

fermenter for the growth of filamentous cultures

Culture liquid—pumped from bottom to top of the cyclone column through a closed loop

Descending liquid ran down the walls of the column in a relatively thin film

Nutrients & air—fed near the base, exhaust gases are left at the top

Advantages: Good gas exchange, lack of foaming, limited wall growth

PARTS OF CYCLONE – COLUMN FERMENTERI – cyclone columnII – circulating pumpIII – recirculating limb

AIR LIFT FERMENTER It is essentially a gas tight baffled riser tube

connected to the downcomer tube. Air or gas mixture—introduced into the base of the

riser by a sparger during normal operating conditions.

The driving force for circulation of medium in vessel is produced by the differences in density between the liquid column in the riser and in the down comer.

This type of vessel can be used for continuous culture.

It would be uneconomical to use a mechanically stirred fermenter to produce SCP from methanol as a carbon substrate ;as heat removal would be needed in external cooling loops because of high rate of aeration and agitation required to operate this process.

To overcome these(Use of mechanical stirrers,cooling) problems air lift fermenters with outer or inner loops were chosen.

ICI plc initially used an outer loop system in their pilot plant—all other companies preferred an inner loop design for large scale operation.

In ICI plc continuous process air and gaseous ammonia were introduced at the base of the fermenter.

Sterilized methanol, other nutrients and recycled spent medium were also introduced into the down comer.

Heat from exothermic fermentation—removed by surrounding part of the downcomer with cooling jacket in pilot plant.

At full scale it was found necessary to insert cooling coils at the base of the riser.

Unfortunately the production of SCP for animal feed was unprofittable because of the price of methanol etc.

TYPES OF ALR:1- INTERNAL LOOP ALR2-EXTERNAL LOOP ALR

DEEP JET FERMENTER Design of continuous culture fermenter—

necessary mechanical power input with a pump to circulate the liquid medium –gas entrainer

Two construction—gas entrainer nozzles Injector Ejector

Injector—jet of medium—surrounded by a jet compressed air

Gas from outlet enters the large tube with the nozzle velocity 5 to 100m/s

Expands in tube—form large air bubbles—dispersed by the shear of water jet

Ejector—liquid jet enters into a large converging-diverging nozzle—entrains the gas around the jet

Gas is sucked into the converging-diverging jet is dispersed in that zone

Aerated medium is pumped by a multiphase pump through a broth cooler to an air entrainer above the fermenter

Air medium mixture falls down—conical shaft at high velocity—creates a turbulence in the fermenter

2/3rd of the exhaust gas is vented from the fermenter head space—reminder via multiphase pump

Oxygen transfer rate 4.5g/dm3 h with an energy consumption of 1kW/hkg

DEEP JET FERMENTER

PACKED TOWER Application for the immobilized cells A vertical cylindrical column is packed

with pieces of some relatively inert material(woodshavings, twigs, coke, polythene)

Both medium and cells are fed into the top of the packed bed

Once cells get adhersed to support(thin film)—fresh medium added at the top of the column—fermented medium removed from the bottom of the column

Vinegar generator—ethanol is oxidised to acetic acid by strains of acetobacter

Mainly used for sewage and effluent treatment

In treatment with gas liquor a column was packed with the height—7.9m with Dowpac—polystrene derivatives

ROTATING DISC FERMENTER Effluent treatment Utilize a growing microbial film on slow

rotating discs to oxidizes the effluent ANDERSON and BLAIN—construct small

fermenter(40dm3) Range of filamentous fungi—Aspergillus,

Rhizopus, Mucor, Penicillium—grow on polypropylene discs

Obtain yield—80g/dm3—production of citric acid using A.niger

REFERENCE

Principles of fermentation technologyPeter F. Stanbury, Allan Whitaker

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