Plate and Frame vs Rotary Filters in Food Processing
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Questions and Answers

What is the primary driving force in rotary vacuum filters?

  • Centrifugal force
  • Hydrostatic pressure
  • Hydraulic pressure
  • Pressure or vacuum (correct)

    • What happens when the available space in a plate and frame filter press is filled with cake?

  • The filtration process speeds up
  • The liquid flow increases
  • The press needs to be dismantled (correct)
  • The cake is automatically removed

    • Which of the following is an advantage of using a plate and frame filter press?

  • Complex mechanization
  • Difficulty in maintenance
  • High flexibility for different foods (correct)
  • High capital costs

    • What is a key disadvantage of the plate and frame filter press?

    <p>It is time-consuming and labor-intensive</p> Signup and view all the answers

    What is continuously scraped from the rotary filter cloth?

    <p>Filter cake</p> Signup and view all the answers

    Which type of filter uses centrifugal force as its driving mechanism?

    <p>Centrifugal filters</p> Signup and view all the answers

    What is a common application of the plate and frame filter press?

    <p>Production of apple juice and cider</p> Signup and view all the answers

    What distinguishes rotary vacuum filters from other types of filters?

    <p>They provide a significant degree of mechanization</p> Signup and view all the answers

    What is the primary factor determining high selectivity in porous membranes?

    <p>The size of the solute relative to the pore size</p> Signup and view all the answers

    Which type of membrane uses carrier molecules to facilitate separation?

    <p>Carrier membranes</p> Signup and view all the answers

    What defines non-porous membranes?

    <p>They rely on diffusion mechanisms without macroscopic pores</p> Signup and view all the answers

    Which range of pore dimensions characterizes microporous membranes?

    <p>50 to 500 angstroms</p> Signup and view all the answers

    Why is high permeability important in membrane structures?

    <p>It enables selective passage of certain molecules</p> Signup and view all the answers

    In what applications are carrier membranes most commonly utilized?

    <p>Liquid and gas component separations</p> Signup and view all the answers

    What mechanism determines separation in non-porous membranes?

    <p>Diffusion after dissolution</p> Signup and view all the answers

    What is a key characteristic of porous membranes used in microfiltration?

    <p>Their pore dimensions range from 0.1 to 10 micrometers</p> Signup and view all the answers

    What is the main distinguishing feature of crystallization compared to other separation processes?

    <p>It produces a solid product.</p> Signup and view all the answers

    Which method is commonly used to achieve crystallization from a solution?

    <p>Lowering the temperature.</p> Signup and view all the answers

    In commercial crystallization, why is size uniformity of crystals important?

    <p>It minimizes caking in the package.</p> Signup and view all the answers

    What does membrane separation primarily rely on for separating components?

    <p>Differences in diffusion rates through a semi-permeable barrier.</p> Signup and view all the answers

    What type of membranes are used in microfiltration and ultrafiltration?

    <p>Porous membranes.</p> Signup and view all the answers

    What is the role of the sweep in membrane separation?

    <p>To help remove the permeate.</p> Signup and view all the answers

    Which component of membrane separation is retained and does not pass through the membrane?

    <p>Retentate.</p> Signup and view all the answers

    Which of the following is NOT an example of crystallization in food technology?

    <p>Creation of flavored syrups.</p> Signup and view all the answers

    What is the typical particle size range that microfiltration can separate?

    <p>0.1 to 10 micrometers</p> Signup and view all the answers

    Which type of membrane is primarily used for reverse osmosis?

    <p>Polyamide</p> Signup and view all the answers

    What is the hydrostatic force required for microfiltration?

    <p>About 1 bar</p> Signup and view all the answers

    What is the pore size range for ultrafiltration membranes?

    <p>10-3 to 10-2 micrometers</p> Signup and view all the answers

    Which material is used for gas separation processes?

    <p>Polyamide</p> Signup and view all the answers

    In nanofiltration, which type of ions are allowed to pass through the membrane?

    <p>Monovalent ions</p> Signup and view all the answers

    Which of the following applications is microfiltration least suitable for?

    <p>Water taste sensitive applications</p> Signup and view all the answers

    What is the molecular weight range for particles that ultrafiltration separates?

    <p>Greater than 1000 kDa</p> Signup and view all the answers

    What is one of the primary purposes of reverse osmosis?

    <p>Removing inorganic salts from water</p> Signup and view all the answers

    What is the size range of particles that reverse osmosis can effectively filter?

    <p>Approximately 0.001 micrometers and below</p> Signup and view all the answers

    What role does external pressure play in the reverse osmosis process?

    <p>It counteracts natural osmosis to drive water flow</p> Signup and view all the answers

    Which type of water is likely to utilize reverse osmosis?

    <p>Boiler feed water with high purity requirements</p> Signup and view all the answers

    What does the module in a reverse osmosis system primarily do?

    <p>Support large membrane areas in a compact space</p> Signup and view all the answers

    Which particle characteristic enhances separation in reverse osmosis?

    <p>Higher charge of the particles</p> Signup and view all the answers

    What is typically necessary to overcome osmotic pressures in reverse osmosis?

    <p>Considerably higher pressures</p> Signup and view all the answers

    Which substance can reverse osmosis effectively filter out?

    <p>Bacteria and some proteins</p> Signup and view all the answers

    Study Notes

    Plate and Frame Filter Press

    • Used for solid-liquid separation in food processing
    • Plates with filter cloths are hung vertically, operating in parallel
    • Feed liquor is pumped into the press, passing through filter cloths
    • Liquid flows down grooved plate surfaces and drains through outlet channels
    • Filter cake builds up on the cloth, increasing pressure drop
    • In the early stages, filtration is constant rate, later becomes constant pressure
    • When frame space fills with cake, the press is dismantled for cleaning
    • Advantages: Low capital costs, high flexibility, reliable, easy maintenance
    • Disadvantages: Difficult to mechanize, time-consuming, labor intensive

    Rotary Filters

    • In rotary filters, slurry flows through rotating cylindrical cloth
    • Filter cake is continuously scraped off
    • Pressure or vacuum can provide the driving force
    • Rotary vacuum filters are particularly useful
    • Cloth is supported on a horizontal drum that dips in slurry
    • Vacuum is applied where cake is building up
    • Vacuum is broken where cake is scraped off
    • Filtrate is removed through trunnion bearings
    • Advantages: Mechanized, convenient
    • Disadvantages: Expensive

    Centrifugal Filters

    • Use centrifugal force to separate solids from liquids
    • Centrifuges have perforated bowls with filter cloths
    • Driving force provided by centrifugal force

    Crystallization

    • Solid-liquid separation process that produces a solid product
    • Crystallization differs from other separation processes due to solid product
    • Achieved by lowering temperature or concentrating the solution
    • Forms a supersaturated solution, causing solutes to crystallize
    • Important in manufacturing sucrose, glucose, lactose, salt, and processing ice cream
    • Crystal size and shape are crucial for yield, purity, and handling

    Membrane Separation

    • Separates components in a feed using a semi-permeable membrane
    • Feed is separated into a retentate (retained) and a permeate (passes through)
    • Feed, retentate, and permeate can be liquid, gas, or solid
    • Sweep can be used to remove permeate

    Types of Membrane Separation Technologies

    • Non-porous membranes: Separate molecules of the same size, gases and liquids
    • Porous membranes: Used in microfiltration and ultrafiltration, pore size determines separation
    • Carrier membranes: Separation occurs by carrier molecules transporting desired components

    Membrane Structures

    • Porous membranes: Used in microfiltration and ultrafiltration, with pore sizes of 0.1 to 10 µm
    • Non-porous membranes: Separate molecules of the same size, gases and liquids, by diffusion
    • Carrier membranes: Separation based on carrier molecule affinity, for gases or liquids

    Membrane Materials

    • Various natural or synthetic polymers are used, such as polypropylene, polysulfone, polyamide, cellulose, polyacrylonitrile
    • Membrane materials are selected based on desired separation process and pressure

    Classification of Membrane Separation Processes

    • Microfiltration, ultrafiltration, nanofiltration, and reverse osmosis are classified by pore size
    • Pore size determines the particle size that can be separated
    • Separation systems are named based on the size range they operate in

    Microfiltration

    • Separates particles from 0.1 to 10 µm or molecular weight greater than 1000 kDa
    • Examples include yeast cells, red blood cells, coal dust, some bacteria
    • Used for sterile filtration, cell harvesting, fruit juice clarification
    • Least used due to finer membrane systems available

    Ultrafiltration

    • Separates colloidal or molecular particles using suction or pressure
    • Uses semi-permeable membranes

    Nanofiltration

    • Separates particles from 0.001 to 0.01 µm or molecular weight between 250 and 400 kDa
    • Allows some salts to pass, rejecting divalent and multivalent ions
    • Used for sugar concentration, dye desalting, water softening, color removal, bacteria removal

    Reverse Osmosis (RO)

    • Finest membrane size, separating particles smaller than 0.001 µm or molecular weight less than 125 kDa
    • Counters natural osmosis by applying external pressure
    • Removes inorganic salts, non-ionic organic compounds, and small organics
    • Used for potable water, boiler feed water, pharmaceutical water, beverage production

    Membrane Configuration

    • Membrane and support are called a module
    • Modules are assembled to form a filtration system
    • Modules must accommodate large membrane areas in small volume and withstand pressure
    • Designed to maintain a clean membrane surface

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    Description

    This quiz explores two important methods of solid-liquid separation in food processing: Plate and Frame Filter Press and Rotary Filters. It covers their operation principles, advantages, and disadvantages, helping you understand the practical applications of each system in the industry.

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