24(lecture - vessels, drums & tanks).ppt

8/10/2019 24(Lecture - Vessels, Drums & Tanks).ppt

1/39

Drums, Vessels,& Storage Tanks

Design Considerations


2/39

The Equipment ListVessels, including Reactors

Towers

Storage Tanks

See User Added Equipment

Equip # Type Tray Dia Tray Spacing Ideal TraysReal Trays Op. Pressure Max Op. Pressure

mm m ft mm number number m ft KPA bar (guage)

TOWERS

Tower Dia Length or Height

VESSELS

Equip # Name Type Op. Press Max Op. Press OrientationMat'ls of Construction CAPCOSTBase

m ft m ft KPA bar (guage) horiz/vert vessel demister Equip# Cost

Diameter Length or Height
http://www.chemeng.ca/maine.htmlhttp://www.chemeng.ca/mainf.htmlhttp://www.chemeng.ca/maine.html


3/39

Vessels - GeneralWall 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


4/39

Design Pressure Excessive design pressure causes equipment

to be more expensive than is required

t = metal thickness, P = Design Pressure

Cc= Corrosion Allowance, Ej= JointEfficienc 5

for cylindrical shells

tP ri

S EJ PC

c


5/39

Vessels - General


6/39

General - Design

TemperaturesAllowable Stress Values are dependant on

Temperature

Temperature at Design Pressure must bestated

Materials become brittle below certaintemperatures - minimum design metaltemperature


7/39

Reflux Drums


8/39

Reflux Drum SizingAssume a length to diameter Ratio of 3

Therefore:

Solve for diameter

vol dia

2

2

3 dia( )

diavol

4

3

1

3


9/39

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 fullTRAY NET VAPOR RATES AND DENSITIES

--------------- RATES ------

TRAY MW ACTUAL DENS Z FROM NORMAL

KG/M3 DENSITY K*KG/HR K*M3/HR

---- -------- ------------ -------- ----------- ----------- --

1 43.543 4.23300 0.95990 5.097E-02 2.624E-02 .

2 42.180 4.05470 0.95259 4.412 2.345

3 40.722 3.91766 0.95369 4.302 2.368


10/39

General - Tanks/Vessels Method 2 - Hold Up Time (at half full)

2 to 32 minutes depending on quality of controlfor each outgoing stream

5 to 10 minutes is sufficient with modern controlsystems to handle minor upsets

30 minutes provides a 99% probability that anoperator can determine cause of failure

Engineering Judgement !

11


11/39

Vessels - SafetyVessel that can be isolated require

Relief Valves


12/39

Vessels - Relief Valves


13/39

Vessels (Reactor) Sized on processing

requirements

Agitated vessels usuallyhave L/D ~ 1

Non agitated L/D ~ 3

Superficial velocitiesimportant?

Fluidization of contents?

Internal coils, external

jackets


14/39


15/39

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


16/39

General - Tanks/Vessels

Mesh

EntrainmentSeparator

36 + 1/2

feed nozzleOD (48

min)

12 + 1/2

feed nozzle

OD (18min)

Vertical Separator13


17/39

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 EconomicalDesign - but not a necessity

Vallowable k L vv

Vdesign 75 %( ) Vallowable

13


18/39

Mesh Separator


19/39

Codes Stds - ASMEASME - American Society of Mechanical

Engineers

Section I - Fired HeatersSection VIII - Pressure Vessels

Other Sections (Plastic / Fiberglass /

nuclear)

14


20/39

AuxiliariesManholes / inspection ports

ASME Code has minimum requirements for

these based on vessel size - See Section 8UG-46

Nozzles - velocities

max v=100/ , ft/secmin v= 60/ , ft/sec

Non-tangential inlet for easier level control

14


21/39

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


22/39

Towers Diameter - Pro II

Tray Section Height

Number of Real Trays

Ideal Trays / 0.6 * 1.1

Height = 24 x # trays

Remember - subtract condenser & ReboilerAdditional Height for Reboiler

Additional Height for V/L Separation at top

Double Tray Spacing at Feed


23/39

Towers

6 ft

4 ft

Double Tray

Space


24/39

Towers - Diag


25/39

Valve Trays


26/39


27/39

Towers Packing

Random

Structured


28/39

Field Fabricated Vessels/Tanks Fabricate in field if shipping is impractical

Typically large atmospheric tanks

Tank TypesCone,

floating roof,

sphere,hemispheroid

Codes & Stds API, ASME


29/39

Storage TanksDesign Pressures < 15 psig


30/39

Tank Farm


31/39

Tanks - Cone Roof Typically Design Pressure < 2 psig, but

usually 2.5 Inches Water gauge

Ensure Vapour Pressure of Liquid issufficiently low (suggest < half D.P.)


32/39

Storage Tanks - Cone RoofConservation Vent


33/39

Tanks - Floating Roof Suitable for fluids with vapour pressures up

to about 8 psig

pontoonsEdge Seal

Floating Roof


34/39

Tanks - Spheres Suitable for Design Pressures of

2 to 15 psig

30 to 220 psig (Ludwig)


35/39

Tanks - Bullet TanksAny Pressure


36/39

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 feednozzle OD (48

min)

12 + 1/2

feed

nozzle OD

(18 min)


37/39

end


38/39

questions types of trays

horiz vs vertical reactors

lifter roof?Margin of error on flows


39/39

Reflux Drums (HYSYS) The Volume

Liquid Rate Into the Drum - Careful of your

simulator flows

Give 20% excess for start-up

24(lecture - vessels, drums & tanks).ppt

Documents