kagadpencil
Mechanical
I am trying to read up some introductory stuff about trays used in refinery applications, Hydrotreater etc. Any suggestions?
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trays
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kagadpencil
Mechanical
can some one explain to me what the following terms mean? I have given my understanding. Please correct me if i am wrong.
Max Tray Pressure Drop across entire column (psi)
with the trays installedi in the tank, what is the max pressure drop? But I wonder what flow conditions this pressure drop is for? how do they decide this value? obviously they have to be simple turbulent flow calc. right? what is the use of this value? I guess it kind of represents the amount of resistance offered by the trays to the flow of vapor and liquid and what have you in the tower.
Max Dry Tray Pressure Drop (Inches of Water)
is that the same as the last one?
% Jet Flood
?????????????
% Downcomer Flood
?????????????
Downcomer Backup (Inches of Water)
?????????????
Turn down capability
I guess this is the percentage value. if it is 50%, then the trays wont function well when the flow comes below 50% of the full flow in the trays.
Foaming Factor i.e. system factor
?????????????
Max Tray Pressure Drop across entire column (psi)
with the trays installedi in the tank, what is the max pressure drop? But I wonder what flow conditions this pressure drop is for? how do they decide this value? obviously they have to be simple turbulent flow calc. right? what is the use of this value? I guess it kind of represents the amount of resistance offered by the trays to the flow of vapor and liquid and what have you in the tower.
Max Dry Tray Pressure Drop (Inches of Water)
is that the same as the last one?
% Jet Flood
?????????????
% Downcomer Flood
?????????????
Downcomer Backup (Inches of Water)
?????????????
Turn down capability
I guess this is the percentage value. if it is 50%, then the trays wont function well when the flow comes below 50% of the full flow in the trays.
Foaming Factor i.e. system factor
?????????????
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kagadpencil
Mechanical
Also can you please tell me what is:
% of System Limitation
Entrainment as % of liquid load
Tray Weeping (lb/hr)
% of System Limitation
Entrainment as % of liquid load
Tray Weeping (lb/hr)
The definition
System factor: most correlations are established for standart systems (hydrocarbons). Some systems can be foaming, ... and will call for some derating. The system factor is a coefficient applied for such cases. Is often equal to 1.
%Jet flood Jet flooding occurs when entrainement is so high that liquid reaches the next tray. The point at which this appears is the jet flood point. The %jet flood is just how close you are from this point. At 100% the column is flooded and cannot be operated.
%Downcomer flooding
When the liquid rate is so high that the downcomer cannot evacuate the liquids from the tray to the tray below, It floods. The %Downcomer flood tells you how close you are from this point
Jet Flooding is mostly related to vapor rate, Downcomer floodind is related to liquid rate. The higher the pressure, the more concerned you should be with downcomers, because the volumetric L/G increases.
Downcomer backup: more or less the level difference between the liquid level on the tray, and the liquid level in the downcomer. This is important to prevent vapors from going through the downcomer.
Turndown: Maximum rate/Minimum rate at which the column operates properly. Should be as high as possible, but be careful if you see figures greater than 2.5 (for trays). It's a ratio maximum to minimum
Maximum pressure drop: probably the total pressure drop at maximum rate. You are correct, this is a kind of measure of resistance of the colmun to the flows.
Maximum dry pressure drop: Probably the pressure drop at maximum vapor rate, when no liquid (or no reflux) if fed to the column. Not the same at the one above . In my own opinion, of little use.
System factor: most correlations are established for standart systems (hydrocarbons). Some systems can be foaming, ... and will call for some derating. The system factor is a coefficient applied for such cases. Is often equal to 1.
%Jet flood Jet flooding occurs when entrainement is so high that liquid reaches the next tray. The point at which this appears is the jet flood point. The %jet flood is just how close you are from this point. At 100% the column is flooded and cannot be operated.
%Downcomer flooding
When the liquid rate is so high that the downcomer cannot evacuate the liquids from the tray to the tray below, It floods. The %Downcomer flood tells you how close you are from this point
Jet Flooding is mostly related to vapor rate, Downcomer floodind is related to liquid rate. The higher the pressure, the more concerned you should be with downcomers, because the volumetric L/G increases.
Downcomer backup: more or less the level difference between the liquid level on the tray, and the liquid level in the downcomer. This is important to prevent vapors from going through the downcomer.
Turndown: Maximum rate/Minimum rate at which the column operates properly. Should be as high as possible, but be careful if you see figures greater than 2.5 (for trays). It's a ratio maximum to minimum
Maximum pressure drop: probably the total pressure drop at maximum rate. You are correct, this is a kind of measure of resistance of the colmun to the flows.
Maximum dry pressure drop: Probably the pressure drop at maximum vapor rate, when no liquid (or no reflux) if fed to the column. Not the same at the one above . In my own opinion, of little use.
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