#Question id: 14332
#Section 5: Bioprocess Engineering and Process Biotechnology
To ensure turbulent conditions and minimum mixing time during agitation with a turbine impeller, the Reynolds number must be at least 104. A stirred laboratory-scale fermenter with a turbine impeller 5 cm in diameter is operated at 800 rpm. If the density of broth being stirred is close to that of water. The mixing system is scaled up so the tank and impeller are 15 times the diameter of the laboratory equipment. The stirrer in the large vessel is operated so that the stirrer tip speed (tip speed = π N i D i) is the same as in the laboratory apparatus. How does scale-up affect the maximum viscosity.
#Question id: 14333
#Section 5: Bioprocess Engineering and Process Biotechnology
A cylindrical bioreactor of diameter 3 m has four baffles. A Rushton turbine mounted in the reactor has a diameter one third the tank diameter and is operated at a speed of 90 rpm. The density of the fluid is approximately I g cm-3. The reactor is used to culture an anaerobic organism that does not require gas sparging. The broth can be assumed Newtonian. As the cells grow, the viscosity of the broth increases. when the viscosity is 1000 times greater than water, estimate the power required to achieve turbulence.
#Question id: 14334
#Section 5: Bioprocess Engineering and Process Biotechnology
Laboratory-scale fermenters are usually mixed using small stirrers with electric motors rated between 100 and 500 W. One such motor is used to drive a 7cm turbine impeller in a small reactor containing fluid with the properties of water. The stirrer speed is 900 rpm. Estimate the power requirements for this process.
#Question id: 14335
#Section 5: Bioprocess Engineering and Process Biotechnology
A cylindrical stirred bioreactor of diameter and height 2 m has a Rushton turbine one-third the tank diameter in size. The bioreactor contains Newtonian culture broth with the same density as water and with viscosity 4 cP. If the specific power consumption must not exceed 1.5 kW m-3, determine the maximum allowable stirrer speed. What is the mixing time under these conditions? __________
#Question id: 14336
#Section 5: Bioprocess Engineering and Process Biotechnology
A cylindrical stirred bioreactor of diameter and height 2 m has a Rushton turbine one-third the tank diameter in size. The bioreactor contains Newtonian culture broth with the same density as water and with viscosity 4 cP. The tank is now aerated. In the presence of gas bubbles, the approximate relationship between ungassed power number (NP)0 and gassed power number (NP)g is: (NP)g =0.5 (NP)0. What maximum stirrer speed is now possible in the sparged reactor? Estimate the mixing time.
#Question id: 14337
#Section 5: Bioprocess Engineering and Process Biotechnology