(SEM III) THEORY EXAMINATION 2023-24 PHARMACEUTICAL ENGINEERING

SECTION A – Short Answer Section

This section contains brief conceptual questions related to filtration, drying, evaporation, fluid flow, and basic engineering principles used in pharmaceutical industries. These questions test fundamental understanding of pharmaceutical engineering processes.

Question 1: What is Darcy’s Law?

Answer:
Darcy’s law describes the flow of fluid through a porous medium during filtration.

Formula:

dVdt=KA(P1−P2)μL\frac{dV}{dt} = \frac{KA(P_1-P_2)}{\mu L}dtdV​=μLKA(P1​−P2​)​

Where:

VVV = volume of filtrate

KKK = permeability constant

AAA = filtration area

μ\muμ = viscosity of liquid

LLL = thickness of filter cake

It helps determine the rate of filtration.

Question 2: What is Critical Moisture Content?

Answer:
Critical moisture content is the moisture level at which the drying rate begins to decrease.

Above this level → drying occurs at constant rate.
Below this level → drying occurs at a falling rate.

It is important for designing drying processes in pharmaceutical industries.

Question 3: What is Molecular Distillation?

Answer:
Molecular distillation is a vacuum distillation process used to separate heat-sensitive substances at very low pressure.

Features:

Very short distance between evaporator and condenser

Operates at very low pressure

Used for purification of vitamins, oils, and pharmaceuticals.

SECTION B – Long Answer Section

This section requires detailed explanations of pharmaceutical engineering equipment and heat transfer systems used in drug manufacturing.

Question 1: Explain Ball Mill with Principle and Working.

Answer:

Principle:
Ball mill works on the principle of impact and attrition.

Construction:

Hollow cylindrical shell

Steel or porcelain balls inside

Rotates on its axis

Working:
When the cylinder rotates, the balls fall on the material and crush it into smaller particles.

Advantages:

Suitable for fine grinding

Large capacity

Disadvantages:

High energy consumption

Wear of balls

Application:
Used for size reduction of drugs and chemicals.

Question 2: Explain Rate of Drying Curve.

Answer:

The drying process consists of three stages:

Initial Period:
Surface moisture begins to evaporate.

Constant Rate Period:
Drying occurs at constant speed because surface remains wet.

Falling Rate Period:
Moisture inside the material moves slowly to the surface.

This curve helps determine drying efficiency and drying time.

Question 3: Explain Film and Overall Heat Transfer.

Answer:

Heat transfer occurs through thin layers called films on the surface of fluids.

Two types of heat transfer resistance occur:

Inside film resistance

Outside film resistance

The overall heat transfer coefficient combines these resistances and determines total heat transfer rate in heat exchangers.

SECTION C – Descriptive Section

This section tests deeper knowledge of engineering equipment, drying systems, corrosion prevention, and industrial pharmaceutical plant design.

Question 1: Explain Cyclone Separator.

Answer:

A cyclone separator is used to separate solid particles from gas using centrifugal force.

Working:

Dust-laden air enters the cyclone tangentially.

Centrifugal force pushes particles toward the wall.

Particles fall down and clean air exits from the top.

Applications:

Dust removal in pharmaceutical plants

Air pollution control.

Question 2: Explain Fluidized Bed Dryer.

Answer:

Fluidized bed dryer is used for drying powders and granules.

Principle:
Hot air passes through particles causing them to behave like fluid.

Advantages:

Uniform drying

Faster drying rate

Disadvantages:

High equipment cost

Not suitable for sticky materials.

Question 3: Types of Corrosion and Prevention.

Answer:

Types of corrosion:

Uniform corrosion

Galvanic corrosion

Pitting corrosion

Prevention methods:

Protective coatings

Use of corrosion-resistant materials

Cathodic protection.