AECH2111 Principles of Chemical Engineering-I

Process Units: Basic Functions

• Unit operations are essential in chemical engineering processes, primarily focusing on mass transfer through physical or chemical means.

Divider (Splitter)

• Divides flow rate of a stream into multiple streams with varied rates.
• Composition remains unchanged among outgoing streams.

Mixer (Blender)

• Involves two or more incoming streams that blend into a single exit stream.
• Applicable for gas, liquid, or solid phases.

Dryer (Direct Heating)

• A mass transfer process that removes moisture via evaporation.
• Utilizes heat to produce vapor; dried products may retain some solvent.
• Can handle feed in solid, slurry, or solution forms.

Filter

• Technique for impurity removal from liquids or solid isolation from fluids.
• Operates mechanically or physically to separate solids via a permeable medium.

Distillation Column

• Separates substances based on volatility differences.
• Produces distillate from more volatile components and bottoms from less volatile ones.
• Separation achieved through boiling.

Dehumidification

• Reduces humidity levels in air or gas streams.
• Condensate is a liquid containing only the condensable component (e.g., water).

Humidifier

• Increases moisture in air, usually via evaporation or air circulation through a wet surface.
• Feed gas is unsaturated; the exit product may or may not be saturated.

Flash Separator

• Splits liquid feed into vapor and liquid phases.
• Operates similarly to a partial condenser; involves pressure reduction or heating for vaporization.

Absorption Column

• Absorbs soluble components from a gas stream using a liquid solvent.
• Liquid flows downward, while the gas stream moves upward through the absorbent.

Reactors

• Facilitate chemical reactions, altering molecular species from input to output.
• Various reactor types include batch, plug flow, packed bed, continuous stirred tank, and fluidized bed reactors.

Batch Reactor

• A tank with an agitator and heating/cooling system, suitable for small-scale or varied product processes.
• Varying sizes up to over 15,000 liters; liquid and gas discharge through overhead connections.

Continuous Stirred Tank Reactor (CSTR)

• An open system operating at steady-state with continuous reactant input and product removal.
• Provides uniform conditions inside the reactor and exit stream.

Packed Bed Reactor (PBR)

• Comprises a filled vessel that enhances phase contact during reactions.
• May contain catalysts or absorbents; applicable in reactors, distillation, and scrubbing processes.

Fluidized Bed Reactor (FBR)

• Conducts multiphase reactions where a fluid suspends solid granular materials, acting as a fluid.
• Suitable for high-velocity gas or liquid introduction, promoting uniform mixing and contact.