Equipment Design and Costs for Separating Homogeneous Mixtures

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Equipment Design and Costs for Separating
Homogeneous Mixtures
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• 1. Distillation

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Design Procedures for Columns with Sieve Trays

• Designation of design bases
• Composition and physical properties of feed and
  product
• Special limitations maximum temperature and
  pressure drop restrictions, presence of reactive
  materials or toxic components etc
• Selection of design variables operating
  pressure, reflux ratio, feed condition
• Establishment of physical equilibria data
• data for binary pairs are combined with a model
  (Wilson, NRTL and UNIQUAC) to predict
  multi-component behavior UNIFAC model is used
  for prediction based on functional group

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Design Procedures for Columns with Sieve Trays
(contd)

• Determination of number of equilibrium stages
• Underwood equation for minimum reflux
• Minimum number of stages from Fenske equation
• Number of equilibrium stages, N as a function of
  and (Gilliand equation)

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Design Procedures for Columns with Sieve Trays
(contd)

• Selection of column internals

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Design Procedures for Columns with Sieve Trays
(contd)

• Determination of column diameter

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Design Procedures for Columns with Sieve Trays
(contd)

• Efficiency
• Tray Spacing 0.46 to 0.61 m (0.3 and 0.91
  m are also used)
• Column height

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Design Procedures for Columns with Sieve Trays
(contd)

• Sieve Tray Geometry
• Hole dia 0.005-0.025 m
• Fractional free area 0.06-0.16 m2
• Fractional downcomer area 0.05-0.3 m2
• Pitch/hole dia ratio 2.5-4.0
• Tray spacing 0.305-0.915 m
• Weir height 0.025-0.075 m

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Design Procedures for Columns with Random Packing

• Determination of diameter
• Vapor velocity is 70 to 90 of flooding velocity
• Recommended pressure drop
• 400 to 600 Pa/m for atmospheric and high-pressure
  separation
• 4 to 50 Pa/m for vacuum operations
• 200 to 400 Pa/m for absorption and stripping
  column

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Design Procedures for Columns with Random Packing
(contd)

• Heights of columns
• HTU method

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Design Procedures for Columns with Random Packing
(contd)

• HETP method

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Design Procedures for Columns with Structured
Packing
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Design Procedures for Columns with Structured
Packing (contd)

• Diameter
• Height
• HETP Rule of thumb

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Other Distillation Processes

• Batch distillation
• Food, pharmaceuticals and biotechnolgy industries
• Rayleigh equation

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Other Distillation Processes (contd)

• Azeotropic distillation

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Cost Estimation
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Cost Estimation (contd)

• Costs of distillation column

25 trays
50 trays
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Cost Estimation (contd)

• Costs of sieve tray

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Cost Estimation (contd)
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Cost Estimation (contd)
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Cost Estimation (contd)
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Cost Estimation (contd)
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• 2. Absorption and Stripping

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Gas Treatment with Solvent Recovery
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Design Procedures

• Column diameter 70 to 90 of the flooding
  velocity, Larger of the top or bottom diameter is
  used
• Number of equilibrium stages Modified Kremser
  equation

Solute fraction absorbed
Solute fraction stripped
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Design Procedures (contd)

• Stage efficiency and column height
• Overall efficiency
• Column height Tray spacing/HTU/HETP

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• 3. Membrane Separation

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Selection of Membranes

• Fabricated from natural and synthetic polymers
• Membrane modules
• Plate and Frame (250-400/m2)
• Spiral-wound (25-100/m2)
• Hollow fiber (10-20/m2)
• Tubular (250-400/m2)
• Capillary (25-100/m2)
• Ceramic (1000-1600/m2)

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Concentration Profile across Membranes
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Design Parameter

• Permeance porosity, solubility or partition
  coefficient
• Separation factor/selectivity
• Purity and yield

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Flow Patterns
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• 4. Adsorption

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Selection of Adsorbent

• Activated Carbon
• Molecular Sieve Zeolites
• Silica gel
• Activated Alumina

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Basic Adsorption Cycles

• Temperature Swing cycle
• Cycle time few hours
• Capacity 1 kg per 100 kg
• of adsorbent

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Basic Adsorption Cycles (contd)

• Inert Purge cycle
• Regeneration is done by purging inert gas and
  lowering the partial pressure of the adsorbate
• Cycle times are only a few minutes
• Capacity 1 to 2 kg adsorbate per 100 kg adsorbent

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Basic Adsorption Cycles (contd)

• Pressure Swing cycle
• Cycle time few minutes
• Capacity 1 to 2 kg per
• 100 kg adsorbent