VALVES AND FLOWS IN FERMENTOR

The heart of the fermentation system is the fermentor, where the crucial biotransformations occur. It is within this vessel where substrates, microorganisms and the fermentation products intermixed. Everything, be it gases, liquids and solids enter and leave the fermentor vessel at one time or other. Thus we see under a steady state conditions solids, gases and liquids will be spending a period of time in the fermentor. There is always a dynamic flux of the various phases in the fermentor

This flux of solids, liquids and gases in the fermentor occur under full regulation or control and efficiently executed by the use of pipes, tubings, pumps and valves. We could picture this controlled flux by the four components as the ' circulatory system' of the fermentor

The circulatory system ensures:
1 Heating and cooling of the fermentor
2 Supply input of nutrients
3 Supply of inocula
4 Removal of samples
5 Removal of broth
6 Controlling input of micronutrients, acids, alkalis, antifoams
7 Removal of exhaust air and other gases


When we talk about the valves it must be discussed in terms of pipes and tubings and the pumps. The three components form the complete system of flow control for gases and fluids.
In such situations we can see that valves will control:

1 Volume of fluids going through the pipes
2 Rate of flow
3 Direction of flow for the fluids

In most cases when the valves are involved in controlling the flow of fluids through the fermentor system, the driving force of the fluid through the valves will be carried out by the pumps that will provide the pressure or drive to move the fluid. In pressure or safety valve, the pressure is attributed to the positive pressure created in the fermentor by the air pumped into the fermentor and through the exhaist gas outlet.

There are many types of valves to choose from. A right valve is needed for a particular function in the fermentor. The choice of valves used depends on factors such as:

1 Do you need a fine control of the flow?
2 Do you need a rapid large volume flow of fluid?
3 Do you need a one way flow and avoid backflow of gases and liquids?
4 Do you need to divert flows of fluids?
5 Is the valves to be used needed in aseptic conditions?
6 Will the valve be of sanitary quality requirements?
7 Will it be easily cleaned by CIP or SIP?
8 Is the valve for safety pressure release?

The characteristics of commonly used valves in the fermentation plant, industries or in the fermentor system are as shown.

FUNCTION VALVE TYPE
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1 On and off control Ball valve,Gate valve
2 Large pipes Butterfly valve
3 One way flow Check valve
4 Sanitary flow Diaphragm valve
5 Flow regulation Globe valve
6 Slow pressure release Needle valve


Try to look at your whole fermentor system and note where all the valves are. (Note: Some of the valves are "hidden" by not being in the fermentor itself!!!)