Fermentation vessels cooling jackets

Agttation. The purpose of agitation is to keep the microorganisms in suspension, to maintain uniformity to eliminate concentration gradients and hot spots, and to improve heat transfer to the cooling jacket. Rules for the design of agitation systems are covered in Chapter 10. In vessels of a 1000 gal or more, a power input of about 10 HP/1000 gal and impeller tip speeds of 15-20 ft/sec are adequate, but the standard fermenter described in Table 19.15 is supplied with about four times this power. 

Fig. 19.5 Large outdoor fermentation vessel (USP 3, 374, 726). 1. Tank 2. Cooling jacket 3. Foamed-synthetic resin 4. Manhole 5. Beer drainage cock 6. Beer feed pipe 7. Beer discharge pipe (pivoted) 8. Exhaust pipe 9. Siphon breaker 10. Pressure relief valve 11. Vacuum breaker 12. Thermometer and liquid depth senser 13. Water and detergent supply pipe 14. Water and detergent spray.

The production of benzylpenicillin is very sensitive to temperature. A lot of metabolic heat is generated and the fermentation temperature has to be reduced by controlled cooling. This heat transfer is achieved by circulating chilled water through banks of pipes inside the vessel (which also serve as baffles) or through external limpet coils on the jacket of the vessel. These coils consist of continuous lengths of pipe welded in a shallow spiral round the vessel. This cooling water system is also used to cool batched medium sterilized in the vessel prior to its inoculation. 

In many chemical and processing applications, fluids need to be heated or cooled and a wide range of equipment may be utilized. Examples include double pipe and shell and tube heat exchangers, and stirred vessels fitted with cooling coils or jackets. Sometimes, heat is generated in the process, as in extrusion which is extensively carried out in the polymer and food industry. It may also be necessary to reduce the rate at which heat is lost from a vessel or to ensure that heat is removed at a sufficient rate in equipment such as screw conveyors. In most applications, it is the rate of heat transfer within process equipment which is of principal interest. However, with thermally sensitive materials (such as foodstuffs, fermentation froths, pharmaceutical formulations), the temperature profiles must be known and maximum permissible temperatures must not be exceeded. 

Yeast removed from the fermenter by suction is usually collected in an enclosed cylindrical vessel called a yeast back. The yeast is usually pumped from the back to a sheet filter press where entrained beer (barm ale) is recovered and after pasteurizing it is blended with racked beer (Fig. 19.16). Sometimes the yeast is held in the filter which is cooled by water or brine circulating in a jacket around it. In other cases, the yeast is discharged from the filter into trays or trucks which are placed in a refrigerator until it is required for pitching. 

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