Separations Technology in Petroleum Refining - Pall Corporation

Refineries receive high return on investment after installing Pall backwash filters to protect catalyst beds and to remove catalyst fines from FCC slurry oil.
Gas-Assist Backwash Method
The gas-assist method is used when
process flow rates are high, or, continuous,
uninterrupted flow is required. For
backwash, one vessel is isolated and the
downstream side of the vessel is pressurized
with a controlled quantity of filtered
air or other suitable gas. The vessel drain
port is rapidly opened, resulting in a
hydraulic pulse that “bumps” the collected
solids from the filter surface. Forward
flow is restored to this vessel, and the
remaining filter vessels are backwashed
sequentially.
During gas-assist backwash, the
expanding gas bubble forces the liquid
through the elements in the reverse
direction (inside-out) at a velocity as high
as seven times the normal forward flow
velocity. This effectively dislodges the
accumulated cake from the elements,
while significantly reducing the volume
of liquid required. Thus, the concentration
of the solids discharge is high.
Combining the gas-assist backwash
with the high dirt-holding capacity of
Pall’s backwash media results in long
cycle times between backwashing.
Benefits of Pall
Backwash Systems and
Gas-Assist Backwash
•Longer Catalyst Life
•Reduced Incidence of “Off-Spec”
Product
•Low Reprocessing and/or Disposal
Costs Due to Low Volume of
Backwash Fluid
•Low Maintenance Cost for Valves and
Control Equipment
•Infrequent “Out-of-Vessel” Element
Cleaning
Pall Backwash System
Process
Out
Process
In
Backwash
Gas In
Solids Recovery
•One or More Vessels
•Isolate One Vessel for Backwash
•A Compressed Volume of Gas Provides
a High-Velocity Reverse Flow of
Liquid Remaining in Vessel
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