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# Equipment Design and Costs for Separating Homogeneous Mixtures - PowerPoint PPT Presentation

Equipment Design and Costs for Separating Homogeneous Mixtures. 1. Distillation. Design Procedures for Columns with Sieve Trays. Designation of design bases Composition and physical properties of feed and product

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Equipment Design and Costs for Separating Homogeneous Mixtures

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## Equipment Design and Costs for Separating Homogeneous Mixtures

1. Distillation

### 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

### Design Procedures for Columns with Sieve Trays (cont’d)

• Determination of number of equilibrium stages

• Underwoodequation for minimum reflux

• Minimum number of stages from Fenske equation

• Number of equilibrium stages, N as a function of and (Gilliand equation)

### Design Procedures for Columns with Sieve Trays (cont’d)

• Selection of column internals

### Design Procedures for Columns with Sieve Trays(cont’d)

• Determination of column diameter

### Design Procedures for Columns with Sieve Trays (cont’d)

• Efficiency:

• Tray Spacing: 0.46 to 0.61 m (0.3 and 0.91 m are also used)

• Column height

### Design Procedures for Columns with Sieve Trays (cont’d)

• 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

### 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

### Design Procedures for Columns with Random Packing (cont’d)

• Heights of columns

• HTU method

• HETP method

### Design Procedures for Columns with Structured Packing (cont’d)

• Diameter

• Height

• HETP: Rule of thumb

### Other Distillation Processes

• Batch distillation:

• Food, pharmaceuticals and biotechnolgy industries

• Rayleigh equation

### Other Distillation Processes (cont’d)

• Azeotropic distillation

### Cost Estimation (cont’d)

• Costs of distillation column

25 trays

50 trays

### Cost Estimation (cont’d)

• Costs of sieve tray

### Cost Estimation (cont’d)

2. Absorption and Stripping

### 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

### Design Procedures (cont’d)

• Stage efficiency and column height

• Overall efficiency

• Column height: Tray spacing/HTU/HETP

3. Membrane Separation

### 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)

### Design Parameter

• Permeance: porosity, solubility or partition coefficient

• Separation factor/selectivity

• Purity and yield

### Flow Patterns

• Activated Carbon

• Molecular Sieve Zeolites

• Silica gel

• Activated Alumina

• Temperature Swing cycle

• Cycle time: few hours

• Capacity: 1 kg per 100 kg

• 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