# Biochemical Engineering - Downstream Processing

### Exercise :: Downstream Processing - Section 1

• Downstream Processing - Section 1
6.

Maintenance cost varies from

 A. 0-4% of the capital cost B. 12-16% of the capital cost C. 4-8% of the capital cost D. 8-12% of the capital cost

Explanation:

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7.

The optimum wet solid content for the cell suspension for a bead mill is typically somewhere between

 A. 5-15% by volume B. 15-30% by volume C. 30-60% by volume D. 60-90% by volume

Explanation:

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8.

Assuming the laminar flow across the filter, the rate of filtration (dVf/dt) can be expressed as a function of pressure drop Dp by the modified D'Arcy's equation as (where A is the area of filtering surface, K is the D'Arcy's filter cake permeability and L is the thickness of the filter cake)

 A. (1/A) dVf/dt = Δp/μ(L/K) B. dVf/dt = (1/A)Δp/μ(L/K) C. (1/A) dVf/dt = Δp/μ LK D. dVf/dt = (1/A)Δp/μ LK

Explanation:

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9.

Filtration leaf test results indicate that the filtration rate of a protein product is 100 dry lbs/(ft2 hr). What size production filter would be required to obtain 100 dry lbs of filter cake/hr?

 A. 1.54 ft2 B. 3.08 ft2 C. 65 ft2 D. 65 lbs/ ft2.hr

Explanation:

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10.

Selectivity can be expressed as

 A. ratio of the distribution coefficients in different solute B. mass fraction of the solute in the extract phase at equilibrium C. mass fraction of the solute in the raffinate phase D. ratio of the mass fraction of the solute in the extract phase to the raffinate phase