where k = reaction rate coefficient
A = some constant
e = basis of Napierian logarithms
E = activation energy
R = universal gas constant
T = absolute temperature
The following is a table of typical activation energies:
|Material||Activation Energy, cal/mol|
|Putrefactive anaerobe NCA 3679||72,400|
We can take advantage of these differences in activation energy to minimize overcooking of the medium and destruction of its nutrient value. Temperature and exposure time are the variables, and the game calculates the number of organism remaining and the concentration of labile nutrients (heat-labile substances are called vitamins for convenience). This is translated to profit for an entire factory operated with these specifications. One living organism is assumed to be enough to cause contamination. A number of less than 1 organism is converted to a percentage of contaminated fermenters, e.g., 0.1 organism/fermenter = 10 per cent lost to contamination.
The game considers not only the time at the sterilization temperature but the heat up and cool down periods. Heat transfer is quite good for small vessels, but the fraction of available heat transfer surface is less for large vessels, so it is difficult to heat up or cool down rapidly. Venting the vessel would give a precipitous drop in temperature as some of the contents evaporate, but this is accompanied by too much foaming to be practical. One way to get rapid heat transfer is to sterilize, not in the vessel, but in a heat exchanger. The fluid is pumped continuously, and there is excellent energy economy by letting the hot sterilized medium exchange with the incoming medium.
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