Specialized drying equipment MCQs With Answer

Introduction: Specialized drying equipment MCQs With Answer is designed for M.Pharm students preparing for advanced topics in Pharmaceutical Manufacturing Technology. This set focuses on the theory, operation, process parameters, scale-up considerations and product quality implications of specialized dryers used in pharmaceutical production — including tray, tray vacuum, fluidized bed, spray, freeze (lyophilization), drum, belt and heat-pump dryers. Questions emphasize mechanisms of heat and mass transfer, critical process parameters (temperature, pressure, gas velocity, atomization), product stability issues, and safety concerns such as dust explosions and solvent handling. Use these MCQs to reinforce concepts, identify knowledge gaps and prepare for exams or practical process design tasks.

Q1. Which mechanism is the primary mode of heat transfer to the product in a conventional tray dryer?

• Conduction through the tray
• Convection from hot air to the product surface
• Radiation from heating elements
• Direct steam injection into the product

Correct Answer: Convection from hot air to the product surface

Q2. What is the defining feature of a fluidized bed dryer that enhances drying efficiency?

• Use of rotating trays for mixing
• Formation of a moving thin film on heated cylinders
• Suspension of particles by an upward gas flow creating high convective transfer
• Direct contact between superheated steam and product

Correct Answer: Suspension of particles by an upward gas flow creating high convective transfer

Q3. In spray drying, which process parameter most directly determines the primary particle (final) size?

• Inlet air temperature
• Atomization (nozzle) droplet size
• Drying gas humidity
• Residence time in the cyclone

Correct Answer: Atomization (nozzle) droplet size

Q4. During lyophilization (freeze-drying), what occurs during the primary drying stage?

• Removal of bound water by desorption
• Sublimation of frozen solvent (ice) to vapor
• Heating to melt the product before drying
• Final moisture adjustment to target residual moisture

Correct Answer: Sublimation of frozen solvent (ice) to vapor

Q5. What does the ‘collapse temperature’ (Tc) refer to in freeze-drying of pharmaceuticals?

• The temperature at which ice sublimates rapidly
• The maximum shelf temperature safe during secondary drying
• The product temperature above which the porous cake structure collapses
• The glass transition temperature of the frozen solvent

Correct Answer: The product temperature above which the porous cake structure collapses

Q6. What is a primary advantage of a heat-pump dryer in pharmaceutical drying?

• It operates at atmospheric pressure only
• It recycles latent heat, improving energy efficiency and humidity control
• It guarantees sterile drying without additional filters
• It eliminates the need for exhaust systems

Correct Answer: It recycles latent heat, improving energy efficiency and humidity control

Q7. For drying a heat-sensitive active pharmaceutical ingredient (API), which drying method is generally most suitable?

• Conventional hot air tray drying at high temperature
• Vacuum drying / vacuum tray dryer
• Direct drum drying with steam contact
• Open sun or ambient air drying

Correct Answer: Vacuum drying / vacuum tray dryer

Q8. Which spray dryer operating parameter most strongly affects drying time for individual droplets?

• Nozzle material
• Feed solid content only
• Initial droplet diameter produced by atomization
• Cyclone geometry

Correct Answer: Initial droplet diameter produced by atomization

Q9. What is the objective of secondary drying in lyophilization?

• To remove uncrystallized solute
• To sublimate remaining bulk ice
• To desorb bound water and reduce residual moisture to target levels
• To cool the product to storage temperature

Correct Answer: To desorb bound water and reduce residual moisture to target levels

Q10. Which specialized dryer is most appropriate for processing sticky, heat-sensitive pharmaceutical pastes into sheets or ribbons?

• Rotary spray dryer
• Vacuum belt dryer
• Fluidized bed granulator/dryer
• Tray dryer at atmospheric pressure

Correct Answer: Vacuum belt dryer

Q11. What is the most common root cause of industrial dryer explosions in pharmaceutical plants?

• Overheating of non-flammable solids
• Combustible dust clouds or flammable solvent vapors ignited by an ignition source
• Excessive vacuum causing implosion
• Excess moisture causing microbial growth

Correct Answer: Combustible dust clouds or flammable solvent vapors ignited by an ignition source

Q12. In spray drying, which temperature measurement is most commonly used as an indicator of product outlet dryness?

• Dry-bulb inlet temperature
• Wet-bulb temperature at the feed pump
• Outlet (exit) air temperature
• Surface temperature of the cyclone

Correct Answer: Outlet (exit) air temperature

Q13. During scale-up of a spray drying process, which dimensionless or operational parameter is critical to maintain for similar drying kinetics?

• Total plant footprint
• Feed pump brand
• F/M ratio (mass feed rate to mass flow rate of drying gas)
• Number of operator shifts

Correct Answer: F/M ratio (mass feed rate to mass flow rate of drying gas)

Q14. What immediate risk arises if product temperature exceeds the collapse temperature during primary drying of a lyophilization cycle?

• Increased crystallinity of excipients
• Cake collapse leading to loss of structure and compromised reconstitution
• Sterility failure due to high temperature
• Excessive loss of volatile active ingredient only

Correct Answer: Cake collapse leading to loss of structure and compromised reconstitution

Q15. Which statement is a principal advantage of vacuum drying compared to atmospheric hot-air drying for pharmaceuticals?

• Vacuum drying always dries faster irrespective of material
• Vacuum drying decreases the boiling point of solvents allowing lower temperature drying of heat-sensitive materials
• Vacuum drying eliminates the need to control moisture content
• Vacuum drying prevents any oxidation reactions

Correct Answer: Vacuum drying decreases the boiling point of solvents allowing lower temperature drying of heat-sensitive materials

Q16. Which drying technique most commonly produces spherical, porous particles with relatively high surface area suitable for inhalation products?

• Drum drying
• Spray drying
• Tray drying
• Belt drying

Correct Answer: Spray drying

Q17. What is the primary function of the atomizer in a spray dryer?

• To separate particles from air in the cyclone
• To generate small droplets, increasing surface area for rapid drying
• To cool the drying air before it contacts the feed
• To filter inlet air for sterility

Correct Answer: To generate small droplets, increasing surface area for rapid drying

Q18. Which dryer is typically used to dry highly viscous slurries into thin films or flakes on a heated rotating surface?

• Fluidized bed dryer
• Drum (roller) dryer
• Lyophilizer
• Spray dryer with rotary atomizer

Correct Answer: Drum (roller) dryer

Q19. In a fluidized bed dryer, what is the role of the air distribution (plenum) plate?

• To heat the air uniformly using electrical coils
• To ensure uniform gas distribution and avoid channeling for stable fluidization
• To separate fines from product by filtration
• To atomize liquid binders during granulation

Correct Answer: To ensure uniform gas distribution and avoid channeling for stable fluidization

Q20. Which drying technique explicitly uses sublimation as the principal mechanism for removing solvent?

• Azeotropic distillation-assisted drying
• Vacuum tray drying at elevated temperatures
• Freeze-drying (lyophilization)
• Spray drying with superheated air

Correct Answer: Freeze-drying (lyophilization)

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