Standard Dimensions

The standard dimensions of a fermentor are shown in Figure 3.10. The standard geometric configurations in practice are:

1. H/T ratio: The geometric configuration of the fermentor is more commonly denoted by the H/T ratio. The height (H) and diameter (T) actually refers to the height and diameter of the fermentor. The H/T ratios of most stirred tank fermentors range from 3:1 to 4:1 while the ratio can be as high as 10:1 in the case of an air lift fermentor.

2. D/T ratio: The geometric configuration of the impeller is more commonly represented by D/T ratio, i.e., the impeller diameter (D) to tank diameter (T). Impellers with small D/T ratio must be operated at a higher speed in comparison with impellers of large D/T ratio to provide the same power requirement. D/T ratios of 0.3 to 0.5 are commonly used in fermentors. It should be noted that operation at higher impeller speed could result in increased shear rates and consequently may be detrimental for the microorganisms in the fermented broth.

3. Baffle ratio: Baffles play a vital role in improving the aeration efficiency and prevent vortex formation. Baffles should be installed so that there is a gap between the baffle and the vessel wall to minimize the microbial growth on the baffles and walls. The baffle ratio (BR) is given by (190)

where nB is the number of baffles installed, wB is the width of the baffles and T is the diameter of the fermentor.

Organic Gardeners Composting

Organic Gardeners Composting

Have you always wanted to grow your own vegetables but didn't know what to do? Here are the best tips on how to become a true and envied organic gardner.

Get My Free Ebook


Post a comment