6 replies to this topic

[T_bag]

Hi,

 

Why the adsorbers are regenerated counter-currently to the feed ? What will happen if we regenerate the absorbers in the same direction of the feed.   

[Bobby Strain]

Give it some thought and research. Then tell us why.

 

Bobby

[T_bag]

One of the reason I could think of is to have mass transfer zone on the bottom most part, so that feed does not take any impurity even in case of improper regeneration. I would love to know the expert views on it. 

[latexman]

Your question is very general.  Are you interested in specific adsorbers?  If so, attach the specific PFDs and/or P&IDs.  I think you might get better response.

[Bobby Strain]

You didn't spend much time in your search.

 

Bobby

[fallah]

Hi,

 

Why the adsorbers are regenerated counter-currently to the feed ? What will happen if we regenerate the absorbers in the same direction of the feed.   

 

Hi,

 

In an adsorber, say mole sieve dryer, if the regeneration would be performed in the same direction as the adsorption; the rgen gas should remove the huge water molecules from the mole sieves at the beginning of the operation and might not have adequate capacity to remove the lower adsorbed water molecules at the outlet section, hence to remove the adsorbed material uniformly and effectively; the regeneration operation is mostly performed at the opposite direction with respect to the adsorption.

[shvet1]

GPSA Engineering Databook page 20-44
Gas flow during adsorption is typically downflow. This allows higher gas velocities (thus smaller diameter towers) since bed fluidization is avoided. Regeneration gas flow is upflow during the heating period. In this way, any residual water left on the desiccant will be at the top of the bed and will not affect the effluent dewpoint when adsorption is resumed. In addition, upflow heating helps to strip any contaminants from the top of the bed extending desiccant life. Regeneration gas flow during the cooling period may be upflow if the gas is completely free of water, which saves two switching valves per tower. If the cooling gas contains water, cooling flow should be downflow to avoid preloading of the desiccant at the bottom of the bed with water.