Mechanical Mixing in Stirred Tanks
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Questions and Answers

What is the recommended detention time range for a completely mixed flow reactor (CMFR) performing sweep coagulation?

  • 7 to 14 minutes
  • 1 to 7 seconds (correct)
  • 1 to 7 minutes
  • 7 to 14 seconds
  • Which type of impeller provides more turbulence and is preferred for rapid mixing in stirred tanks?

  • Radial-flow impeller (correct)
  • Jet impeller
  • Axial-flow impeller
  • Magnetic impeller
  • Why should tanks be horizontally baffled into compartments for mechanical mixing in stirred tanks?

  • To minimize short circuiting (correct)
  • To maximize vortexing
  • To increase short circuiting
  • To decrease residence time
  • What is the purpose of using dual impellers in a tank?

    <p>To increase the efficiency of power transfer from the motor to water</p> Signup and view all the answers

    Where should chemicals be added for effective rapid mixing in stirred tanks?

    <p>Below the impeller</p> Signup and view all the answers

    What is the geometric ratio range for H/D (either) in tank and impeller geometries?

    <p>2–4</p> Signup and view all the answers

    According to Rushton (1952), how is the power imparted to the liquid in a baffled tank by an impeller typically described?

    <p>Fully turbulent flow</p> Signup and view all the answers

    Why does the volume of a rapid-mix tank seldom exceed 8 m3?

    <p>Limitation by mixing equipment and geometry</p> Signup and view all the answers

    What is the purpose of using both axial-flow and radial-flow impellers when dual impellers are employed?

    <p>Optimizing mixing efficiency</p> Signup and view all the answers

    What G value range is recommended for sweep coagulation in a continuous-flow stirred tank reactor (CSTR)?

    <p>600 to 1,000 s^-1</p> Signup and view all the answers

    How does the use of two impellers on the shaft impact mixing efficiency?

    <p>Enhances mixing efficiency</p> Signup and view all the answers

    What does D represent in the equation for power imparted to liquid by an impeller?

    <p>Impeller diameter</p> Signup and view all the answers

    What is the term used to specify the element size in an in-line static mixer?

    <p>Aspect ratio</p> Signup and view all the answers

    What is a disadvantage of in-line static mixers?

    <p>The mixing uniformity varies with flow rate</p> Signup and view all the answers

    What does the coefficient of variation with time (COV) measure in the context of selecting static mixers?

    <p>Chemical-water blend uniformity</p> Signup and view all the answers

    What is a key advantage of in-line static mixers compared to other mixers?

    <p>External energy source required</p> Signup and view all the answers

    Why are in-line static mixers suitable for applications where no external energy source can be used?

    <p>&quot;They rely on helical vanes for rotation&quot;</p> Signup and view all the answers

    What parameter specifies the element size in an in-line static mixer?

    <p>&quot;Length of element&quot;</p> Signup and view all the answers

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