Read the passage below.
In large-scale cryogenic air separation units (ASUs), atmospheric air is first drawn through multi-stage filtration systems to remove particulate matter before entering the main compressor. Following compression, the air must undergo precooling and purification within molecular sieve beds to strip out residual water vapor and carbon dioxide. This purification step is crucial because at the extremely low temperatures required for subsequent fractional distillation, any remaining moisture or carbon dioxide would solidify, potentially obstructing the delicate heat exchange fins and causing severe mechanical blockages. Once purified, the air is expanded and cooled to approximately -196°C, at which point it liquefies and can be separated into constituent gases such as nitrogen, oxygen, and argon based on their distinct boiling points.
According to the passage, what is the primary reason for extracting water vapor and carbon dioxide before the distillation phase?
- Removing these compounds ensures they do not transition into a solid state and occlude the thermal regulation hardware when the system's temperature drops.Answer
- BThe extremely low temperatures required for fractional distillation cause the purified air to solidify, which can obstruct the delicate heat exchange fins.
- CThe solidification of carbon dioxide and moisture inside the molecular sieve beds generates the extreme cold needed for fractional distillation.
- DThe atmospheric air must be fully expanded and liquefied inside the main compressor prior to entering the molecular sieve beds.