527 Q7 Ch4 Adsorption 3-7

Which of the following statements is true for micro- and mesopores?

(check all that applies; no partial credit)

• Thermodynamically, as temperature increases, the sorbent capacity decreases.

• From a diffusion perspective, higher temperatures result in greater diffusion rates, leading to enhanced sorbent capacity.

• None of them

• Sorbent capacity is not a function of temperature.

Thermodynamic and diffusional limitations show opposite dependences on temperature, with an optimum temperature that maximizes sorbent capacity.

• True

• False

Sorbent pore size is classified (micro, meso, or macro) based on the mean free path of the fluid particles.

• True

• False

Capillary condensation occurs in mesopores because fluid surface tension decreases the fluid vapor pressure in a pore beyond its bulk-phase value, resulting in condensation within the pore.

• True

• False

Typically, a sorbent particle is modelled isothermally, i.e., all heat-transfer resistance takes place in the external film, and all mass-transfer resistance takes place within the particle itself.

• True

• False

The mass-transfer zone of a sorbent bed is defined as

• the region where the majority of the mass-transfer takes place, with local CO₂ concentration dropping from 0.95 to 0.05.

• the fluid film surrounding the pellet particle.

• the macropores inside the pellet, where 95% of the CO₂ is adsorbed.

• the micropores deep inside the pellet, where 95% of the CO₂ is adsorbed.

The sorbent-bed breakthrough time is defined as the time at which the exit CO₂ concentration is _____% of the inlet-feed concentration.

• 10
• 90

• 50

• 0

Sorbents are always fully regenerated.

• True

• False

The goal is to widen the mass-transfer zone within a sorbent bed for greater capture capacity.

• True

• False

What are the advantages of moving-bed adsorbers over fixed-bed ones?

(check all that applies; no partial credit)

• Lower pressure drop

• Larger scale of CO₂ capture

• Extended sorbent lifetime

• Less mechanical complexity

• More compact bed size