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Creating Value Through Chemistry
MERTC 2017, Bahrain
Presentation by: Petar Pribic Senior Process Engineer, Separations SME Sadara Chemical Company
Low versus High Pressure C2 Splitter
Separation requirements (yield/purity)
Process simulation using appropriate thermo model
About 75% of the trays are in enriching section for high ethylene purity
Inter-reboiler design and location
Most responsive temperature location, etc.
Conceptual Process Design
1.5
2
2.5
3
3.5
4
20 70 120
REF
LUX/
FEED
RAT
IO
NUMBER OF THEORETICAL STAGES (NTS)
NUMBER OF THEORETICAL STAGES VS REFLUX FOR GIVEN PRODUCT PURITY AND FEED STAGE LOCATION
Top Pressure 12 bar
Top Pressure 7 bar
Process Modelling/ Simulation
Process Optimization
Process Control
Conceptual Process Design
Choice of Column Internals
Trays are always the preferred choice
Minimum number of liquid passes is two, but could go up to four and even more
More than two passes makes design more complicated
Typical tray spacing is between 380-600mm
Column efficiency varies with operating pressure
Efficiency prediction should be based on industrial plant data for same type of internals to be used
Choice of Column Internals
4-Pass High Capacity Tray Multi Downcomer High Capacity Tray
Column Internals
Hydraulic Design Generate internal loadings and physical properties from simulation
package Always choose loading points above and below feed inlets and
draw-offs Do not rely only on built-in sizing/rating features of commercial
simulators, use vendor’s programs for final rating calculation Evaluation must include an evaluation of all internals, including all
distributors, draw-offs, chimney trays and nozzles, not only trays and packing
Upon receiving vendor’s technical proposal, carefully evaluate tray predicted performance
After receiving drawings for approval, be sure that the internal detail drawings match process and mechanical requirements
Hydraulic Design
Column Operating Range
Hydraulic Design
Liquid Rate
Vapo
r Rat
e
Dump point
OPERATING REGION
Tray Stability Diagram
Hydraulic Design
4-Pass Tray L/V balance Any maldistribution on multipass tray will create localized L/V ratios on tray panel and affect overall tray efficiencies
Internals Installation and Inspection
C2 Splitters require stringent levelness criteria. If the tower, trays or weld-ins attachments are out of level, tower will not perform acc. to expectations, due to high required purities and formation of localized L/V ratios.
Weld quality
Distributor/re-distributor hole number and sizes
Do a mock up of each type of tray
Verify that all parts have some provision for draining
Check mechanical strength of trays and internals and assure that they can sustain excessive force
Internals Installation and Inspection
Ensure that there is no fouling, plugging or obvious damage to trays or internals
Make sure there no trash is in the tower from installation Welded chimney trays and draw-offs should be subjected to a
leakage test Dimensional check for tray features, like:
1. Levelness 2. Deck thickness, valve thickness, valve lift and orientation 3. Number of valves per tray (check for missing/damaged valves) 4. Tray spacing 5. Downcomer width, clearance and outlet weir height 6. Clamp tightness and tray structural stability
Feed piping should have the same tolerance on levelness as trays
Internals Installation and Inspection
Sadara Experience
Design Temperature Profile
Measured Temperature Profile
SADARA C2 SPLITTER OPERATES ACCORDING TO DESIGN WITH PRODUCTS ON REQUIRED SPEC.
Column Top
Column Bottom
Tem
pera
ture
Thank you
Questions?
