18 Questions
What is the recommended detention time range for a completely mixed flow reactor (CMFR) performing sweep coagulation?
1 to 7 seconds
Which type of impeller provides more turbulence and is preferred for rapid mixing in stirred tanks?
Radial-flow impeller
Why should tanks be horizontally baffled into compartments for mechanical mixing in stirred tanks?
To minimize short circuiting
What is the purpose of using dual impellers in a tank?
To increase the efficiency of power transfer from the motor to water
Where should chemicals be added for effective rapid mixing in stirred tanks?
Below the impeller
What is the geometric ratio range for H/D (either) in tank and impeller geometries?
2–4
According to Rushton (1952), how is the power imparted to the liquid in a baffled tank by an impeller typically described?
Fully turbulent flow
Why does the volume of a rapid-mix tank seldom exceed 8 m3?
Limitation by mixing equipment and geometry
What is the purpose of using both axial-flow and radial-flow impellers when dual impellers are employed?
Optimizing mixing efficiency
What G value range is recommended for sweep coagulation in a continuous-flow stirred tank reactor (CSTR)?
600 to 1,000 s^-1
How does the use of two impellers on the shaft impact mixing efficiency?
Enhances mixing efficiency
What does D represent in the equation for power imparted to liquid by an impeller?
Impeller diameter
What is the term used to specify the element size in an in-line static mixer?
Aspect ratio
What is a disadvantage of in-line static mixers?
The mixing uniformity varies with flow rate
What does the coefficient of variation with time (COV) measure in the context of selecting static mixers?
Chemical-water blend uniformity
What is a key advantage of in-line static mixers compared to other mixers?
External energy source required
Why are in-line static mixers suitable for applications where no external energy source can be used?
"They rely on helical vanes for rotation"
What parameter specifies the element size in an in-line static mixer?
"Length of element"
This quiz covers the principles and recommendations for mechanical mixing in stirred tanks, focusing on topics such as sweep coagulation, completely mixed flow reactors (CMFR/CSTR), detention times, and recommended G values. References to Letterman et al., 1973, and Amirtharajah, 1978 are included.
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