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Drums, Vessels, & Storage Tanks
Design Considerations
The Equipment List Vessels, including Reactors
Towers
Storage Tanks See User Added Equipment
Equip # Type Tray Dia Tray Spacing Ideal TraysReal Trays Op. Pressure Max Op. Pressuremm m ft mm number number m ft KPA bar (guage)
TOWERS
Tower Dia Length or Height
VESSELS
Equip # Name Type Op. PressureMax Op. PressureOrientationMat'ls of Construction CAPCOSTBasem ft m ft KPA bar (guage) horiz/vert vessel demister Equip# Cost
Diameter Length or Height
Vessels - General Wall Thickness
determined by required pressure Process Engineer Determines Design
Pressure See Web Notes
Normal Op. Pressure (Pro II)Maximum Op. Pressure (Controls, S/U , S/D ...)
Design Pressure (Relief Valve Set Pressures, Minimum Required Metal Thickness)Process Engineer
Maximum Allowable Working Pressure (MAWP)- Actual Metal Thickness UsedFab Shop
Design Pressure Excessive design pressure causes equipment
to be more expensive than is required
t = metal thickness, P = Design PressureCc = Corrosion Allowance, Ej = Joint Efficiency
5
for cylindrical shells
tP ri
S EJ PCc
Vessels - General
General - Design Temperatures Allowable Stress Values are dependant
on Temperature Temperature at Design Pressure must
be stated Materials become brittle below certain
temperatures - minimum design metal temperature
Reflux Drums
Reflux Drum Sizing Assume a length to diameter Ratio of 3 Therefore:
Solve for diameter
vol dia
2
2
3 dia( )
diavol
4
3
1
3
Reflux Drums (PRO II)
The Volume - Method 1 Determine Liquid Rate Into the Drum -
Careful of your simulator flows Give 20% excess for start-up Size for 5 to 10 min @ half full
General - Tanks/Vessels Method 2 - Hold Up Time (at half full)
2 to 32 minutes depending on quality of control for each outgoing stream
5 to 10 minutes is sufficient with modern control systems to handle minor upsets
30 minutes provides a 99% probability that an operator can determine cause of failure
Engineering Judgement !
11
Vessels - Safety Vessel that can be isolated
require Relief Valves
Vessels - Relief Valves
Vessels (Reactor) Sized on processing
requirements Agitated vessels usually
have L/D ~ 1 Non agitated L/D ~ 3 Superficial velocities
important? Fluidization of contents? Internal coils, external
jackets
Vessels (Reactor) Plug Flow Reactor Issues
Residence Time / Volume - Pro II Pressure Drop - packed beds - ergun
eqt. (Perry’s) Back Mixing - Testing, CFD - L/D > 5
General - Tanks/Vessels Horizontal vs. Vertical
Vertical preferred when: small liquid load limited plot space ease of level control is desired
12
Horizontal preferred when:large liquid loads are involved, consequently hold-up will set the sizethree phases are present
General - Tanks/Vessels
MeshEntrainmentSeparator
36” + 1/2 feed nozzle OD (48” min)
12” + 1/2 feed nozzle OD (18” min)
Vertical Separator13
General - Tanks/Vessels Liquid levels
norm liq level at 50% show low liq level at 25% provide low, low liq level for pump shut offs
Vapour Disengagement (vertical flash vessel) Diameter Calcs; v = ft/ sec; density = lb/ft3
No Mesh k=0.16; Mesh Separators k = 0.35 Length to Diameter Ratio - 3 to 5 for Economical
Design - but not a necessity
Vallowable kL v
v Vdesign 75 %( ) Vallowable
13
Mesh Separator
Codes Stds’ - ASME ASME - American Society of
Mechanical Engineers Section I - Fired Heaters Section VIII - Pressure Vessels Other Sections (Plastic / Fiberglass /
nuclear)
14
Auxiliaries Manholes / inspection ports
ASME Code has minimum requirements for these based on vessel size - See Section 8 UG-46
Nozzles - velocities max v=100/ , ft/sec min v= 60/ , ft/sec
Non-tangential inlet for easier level control
14
Auxiliaries Thermowells Steamouts Maintenance blinds Drains Level Gauges
12 ft
36 inLow Liq Level= 6”
Norm Liq Level = 12”
High Liq Level = 18”
M
V
X
Y U
R
D
Towers
Diameter - Pro II Tray Section Height
Number of Real Trays Ideal Trays / 0.6 * 1.1
Height = 24” x # trays Remember - subtract condenser &
Reboiler Additional Height for Reboiler Additional Height for V/L Separation at top Double Tray Spacing at Feed
Towers
6 ft
4 ft
Double TraySpace
Towers - Diag
Valve Trays
Towers Tray Flows
VIDEO
Towers Packing
Random Structured
Field Fabricated Vessels/Tanks Fabricate in field if shipping is impractical Typically large atmospheric tanks Tank Types
Cone, floating roof, sphere, hemispheroid
Codes & Std’s – API, ASME
Storage TanksDesign Pressures < 15 psig
Tank Farm
Tanks - Cone Roof Typically Design Pressure < 2 psig, but
usually 2.5 Inches Water gauge Ensure Vapour Pressure of Liquid is
sufficiently low (suggest < half D.P.)
Storage Tanks - Cone RoofConservation Vent
Tanks - Floating Roof Suitable for fluids with vapour pressures
up to about 8 psig
pontoonsEdge Seal
Floating Roof
Tanks - Spheres Suitable for Design Pressures of
2 to 15 psig 30 to 220 psig (Ludwig)
Tanks - Bullet Tanks Any Pressure
Workshop
vol dia
2
2
3 dia( )
diavol
4
3
1
3
Vallowable kL v
v
Vdesign 75 %( ) Vallowable
Size the Flasher
Vap Rate: Liq Rate: Vap Density:Liq Density:
Size 50% Liq Hold-up for 10 min
36” + 1/2 feed nozzle OD (48” min)
12” + 1/2 feed nozzle OD (18” min)
end
questions types of trays horiz vs vertical reactors lifter roof? Margin of error on flows
Reflux Drums (HYSYS)
The Volume Liquid Rate Into the Drum - Careful of
your simulator flows Give 20% excess for start-up
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