Exam Question
Explain the following:
(a) Control air dryer - working principle with diagram, of any one type of dryer of your choice. (8)
(b) Any two types of Ballast water treatment system. (8)
Class 4 (4th Engineer)
MEKG
📅 Feb 2025
Reference Answer
### (a) Control Air Dryer - Heatless Regenerative Adsorption Type
**1. Principle of Operation:**
The fundamental principle of a heatless regenerative adsorption dryer is the physical process of **adsorption**. It utilizes a desiccant material, typically activated alumina or silica gel, which has a high affinity for water vapor. The desiccant consists of a porous structure with a vast internal surface area. Water vapor molecules from the compressed air are attracted to and held on this surface by weak intermolecular forces (van der Waals forces), effectively removing moisture from the air stream.
The process is reversible. The desiccant can be 'regenerated' or dried out by passing a very dry, low-pressure gas over it. This purge gas has a lower vapor pressure than the saturated desiccant, creating a partial pressure differential that causes the adsorbed water molecules to be released from the desiccant surface and carried away.
**1. Principle of Operation:**
The fundamental principle of a heatless regenerative adsorption dryer is the physical process of **adsorption**. It utilizes a desiccant material, typically activated alumina or silica gel, which has a high affinity for water vapor. The desiccant consists of a porous structure with a vast internal surface area. Water vapor molecules from the compressed air are attracted to and held on this surface by weak intermolecular forces (van der Waals forces), effectively removing moisture from the air stream.
The process is reversible. The desiccant can be 'regenerated' or dried out by passing a very dry, low-pressure gas over it. This purge gas has a lower vapor pressure than the saturated desiccant, creating a partial pressure differential that causes the adsorbed water molecules to be released from the desiccant surface and carried away.
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