Hello artificial student,
Although I have some opinions with answers to your questions, they remain as opinions and are 'good guesses'
Our senior students asked us about some theories and practical situations about this equipment the "Packed Absorption Column"
the questionsa sked was these:
a.)What causes the difeerence between the dry and the wet column pressure drop at fixed flow condition (the fluid used to wet the column was water)?
my answer to this was:the causes of the differences are due to the water fluid film that is coating the packed beddings. in the dry column the pressure was lower since there is no friction between the water and the gas (air) while when the packings are wetted the pressure increses due to the friction that is due to the prescence of the fluid.
I agree with your comments, although (yes, I am being a bit picky, sorry), is that the dry column will have a lower differential pressure due to
lower friction with the absense of water. When the packings are water-wet, there is a gravitational force of the water (wanting to move in a downward motion due to gravity) and the opposite force of the gas moving in an upward direction. There may also be a factor involving the pore space cross-sectional area. For example: a dry pore opening may have a cross-sectional area of 1 darcy. When water is added, this available cross-sectional area may be decreased to 0.75 (these are only example numbers). Attempting to push a gas through a smaller area will also cause an increase in differential pressure... just a thought
b.)in case the column is operated at the maximum loading, what will be the effect of a decrease in L/G ratio during the operation?
im sorry but i have no answer to this but my hypothesis would be that the flooding point will decrease (i dont know)
To lower the Liquid/gas ratio, either: 1) the liquid concentration decreases or, 2) the gas rate increases.
When we explore possibilities of answer 1, here are some thoughts: If there is a decrease in the liquid (example: water) concentration, then there should be an increased throughput of gas because: a) there is an increased cross-sectional area available for the gas to pass through the column, and b) there is less gravitational weight of water being pulled down on the free column gas spaces.
Answer 2, has these possibilities: The increased gas rate may: a) cause the bottom of the column to have water particles 'blown' to the top of the column, thereby allowing more gas to flow due to an increase in cross-sectional area, and/or b) There may be an increased differential pressure with the net-amount of gas flow (when comparing 'before' an increase in gas flow rate and the 'after' the increased flow rate) should increase because a net increase in overall pressure compresses the gas allowing more gas to flow in the same cross sectional area.
c.) what will be the effect of an increase in liquid viscosity?
my answer to this is that: it will depend on the viscosity of the fluid...
ver viscous fluid tend to channel down the column and thusa great amount of air flow is needed for any mass mehanics or mass transport to occur...(i guess)
I agree
An increase in fluid viscosity (again, assuming that there is a constant influx of fluid from the bottom of the column that eventually proceeds to the top of the column), due to a) a decrease in cross-sectional area (greater so with a more viscous fluid), b) and the amount of fluid which can be passed through the column will be decreased, again, more energy needed to move a viscous fluid by mechanical force than a thinner fluid.
d.)how can these trends (in realtion to b. and c. ) be explained?
i cannot realte to this question so i gave no answers...
I believe that I answered 'b' and 'c' fairly completely :0
I hope this helps.. and makes sense
Sincerely,
Eugene
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Topic: Packed Absorption Column (Read 10701 times)