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Koch-Glitsch FLEXIGRID® structured packing is developed primarily for severe services which are susceptible to fouling, erosion, coking and high solids content. FLEXIGRID® packing is installed in rigid modules stacked in successive layers with a fixed orientation, which minimizes the overall pressure drop while simultaneously increasing tower capacity and/or efficiency.
The blades of the grid packing induce turbulent contact between the rising vapor and descending liquid. There are two distinct styles of FLEXIGRID® structured packing. Style 2 is optimized for maximum capacity, limited liquid holdup and minimum pressure drop. Style 3 is optimized for improved efficiency without limiting either capacity or fouling resistance. FLEXIGRID® Style 3 can be used as a direct replacement of KOCH-GLITSCH GRID® EF-25A. Style 4 has a 50% higher surface area than FLEXIGRD 2 or 3 and is used for higher mass or heat-transfer requirements by maintaining mechanical strength and fouling resistance.
FLEXIGRID® packing is particularly useful in many refinery services, as noted below, where random or other structured packing will coke or foul, potentially causing premature shutdowns. The all-welded construction provides a strong assembly that can withstand the rigorous conditions often found in both refinery and petrochemical services.
FLEXIGRID®
structured packings are constructed in modules. The vertical blades
of the packing are fixed in position with welded cross members.
During installation of either style, each successive layer of the
grid packing is rotated 45 degrees to the previous layer. This
specific orientation eliminates horizontal planes where liquid
and/or solids can collect. The Style 3 packing has a greater
projected area perpendicular to the gas flow causing higher
localized vapor velocities, effectively providing higher
efficiencies.
Support Structure
A full 360 degree support ring is required in the tower under the bottom layer of the grid. Support beams are required if the tower diameter exceeds five feet (1.5m). In this case, intermediate support beams are placed at intervals under the bottom layer of the grid. The bottom layer of FLEXIGRID® packing is clamped to the support structure.
Materials of Construction
FLEXIGRID® packing is available in carbon steel, aluminum, and stainless steel and alloy. It is manufactured in 14 or 16 gauge (2 and 1.5 mm) to provide excellent structural strengths.
Bed Retention
The top three layers of the grid are normally thru-bolted together. Because of the high open area and low pressure drop of FLEXIGRID® packing, no other retaining device is usually required. The structural strength and low pressure drop construction of FLEXIGRID packing enable it to withstand extreme upset conditions and large vapor surges without damages.
Where additional uplift protection is desired, the entire FLEXIGRID® packing bed can be held together with tie rods to form a continuous structure which is highly resistant to mechanical damage and upset. High strength hold-down and support grids can also be added for additional protection where column upset conditions are possible.
Liquid Distributors
Spray nozzle and fouling service trough distributors are normally used in conjunction with FLEXIGRID® packing. The specific type of distributor is selected based on Koch-Glitsch's extensive experience in refinery and chemical services.
In applications where solids in the feed will
plug spray nozzle or conventional trough distributors (FCCU slurry
pumparound sections or particulate-scrubbing operations), weir
trough-type distributors are
recommended.
Applications
FLEXIGRID® packing is adaptable to column revamps or new construction. The high capacity and low pressure drop of FLEXIGRID® packing expand capacity and increase yield. Maintenance costs are also reduced because of both the superior physical integrity and fouling resistance of FLEXIGRID® packing. Costly unplanned shutdowns are prevented by the reduced tendency to coke and/or plug. FLEXIGRID® packing has become a highly reliable
performer, with years of installed service in:
- Crude Atmospheric Towers
- Lube Vacuum Towers
- Crude Vacuum Towers
- Fluid or Thermal Cracking Fractionators
- Coker or Visbreaker Fractionators
- Coker Scrubbers
- Reactor Off-Gas Scrubber
- Gas Quench Towers
- Edible Oil Deodorizers
- Pollution Control Scrubbers
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