2.1

DISTILLATION & TOWER INTERNALS

SECTION 2

2.2

DISTILLATION

• Basic Concepts

• Fractionator Simulation

• Contacting Devices

• Tray Hydraulics

• Tower and Internals Sizing

• Debottlenecking

2.3

Distillation (or Fractionation) is the oldest butstill the largest and most important single

refining process

• Prepares feed for other refining processes

• Separates products from other refining processes

• Largest energy consumer in the refinery

2.4

BASIC CONCEPTS

CONVENTIONAL DISTILLATION COLUMN

2.5

DISTILLATION COLUMN TERMS

• Rectifying section: Section of tower above the feed point. Heavy components are condensed out of the vapor

in this section

• Stripping section: Section of tower below the feed point. Light components are stripped out of the liquid in this section

• Reflux: Liquid from the overhead condenser that is

returned to the top of the tower. The reflux ratio is the reflux rate divided by the overhead product rate

2.6

COMPONENT DEFINITIONS

• Key Components: Major feed components between which a desired split is to be made.

– Light Key: Least volatile major component whose concentration increases up the

tower– Heavy Key: Most volatile major component whose

concentration increases down the tower

• Other Components:– Light Non-Key: Components more volatile than the light key

component which end up almost exclusively in the overhead product

– Heavy Non-Key: Components less volatile than the heavy key component which end up almost exclusively

in the bottoms product– Intermediate Key: Components whose relative volatility are

intermediate between the light and heavy keys and distribute between the top and bottom products

2.7

RELATIVE VOLATILITY

• Separation by distillation takes place by virtue of inequalities in volatilities. Relative volatily is used to express this inequality.

Component Ki = Ki /KC

A KA KA /KC

B KB KB /KC

Key Component C KC 1.0

D KD KD /KC

KA PA/ Vapour Pressure Component A

AC = KC PC/ PA/PC Vapour Pressure Component C

2.8

McCABE - THIELE DIAGRAM

Slo

pe = L

’/ V ‘

Slope = L

/ V

y = x

2.9

McCABE - THIELE DIAGRAM LINES

Line What the line Slope Point through describes which line passes

Equilibrium curve Focus of all equilibrium -- -- points

Rectifying section Rectifying section L/V (xD) if total condensercomponent balance component balances (<1) (yD) if partial condenser(operating) line

Stripping section Stripping section L’/V’ (xB)component balance component balances (>1)(operating) line

q-line Focus of points of q Horizontal line when feed is intersection of rectifying all vapor. and stripping q - 1 Vertical line when feed is all component balance lines liquid.

45º diagonal line 1. Focus of points 1.0 (0,0) and (1.0,1.0)

where x=y 2. At total reflux it

represents thecomponent balance lines

2.10

EFFECT OF REFLUX ON REQUIRED STAGES

2.11

MINIMUM REFLUX - INFINITE STAGES

2.12

TOTAL REFLUX - MINIMUM STAGES

2.13

STAGES VERSUS REFLUX

2.14

LOCATION OF OPTIMUM REFLUX RATIO

2.15

C3-nC4 SEPERATION: EFFECT OF REFLUX

C3=71.4%

68.2%

65.9%

62.0%

53.3%

49.8%

47.3%

43.3%

9

10

11

12

RR = 2.3 : 1

C3=76.0%

66.4%

57.5%

46.1%

58.8%

47.7%

39.0%

29.3%

9

10

11

12

RR = 5.2 : 1

2.16

Fractionation as a concept is simple - only 3 basic laws

1. More reflux -------------------> more separation

2. More trays -------------------> more separation

3. Lower pressure -----------> more separation

2.17

FRACTIONATOR SIMULATION

• Basis for design needs to be defined:

– Feed rate and composition

– Desired separation e.g. recovery and purity

– Conditions for Feed, Products, and Utilities

2.18

BASIC STEPS IN FRACTIONATOR SIMULATION

• Select operating conditions for tower

• Determine key components which represent the desired separation

• Calculate minimum stages and minimum reflux ratio (using short cut distillation techniques)

• Specify operating reflux ratio and the number of theoretical stages (using Gilliland or similar correlation)

• Perform “tray to tray” tower calculation using computer simulation program (PROVision)

• Optimize reflux, stages, feed preheat and feed location with additional computer runs

2.19

TOWER OPERATING PRESSURE

• Select pressure with due consideration to:

– Disposition of vapour distillate– If the overhead is to be totally condensed, temperature of

available cooling medium. If cooling water at 35°C is used, the minimum pressure for bubble point distillate would be that corresponding to the pressure at a bubble point of about 45°C.

– Bottoms temperature for selected pressure:+ Too high a bottoms temperature could result in cracking and

discoloration of product

+ Temperature of heating medium for reboiler

+ Too close an approach to critical temperature will give poor separation (should be at least 28°C below TC)

2.20

TOWER OPERATING TEMPERATURE

• Temperatures are fixed by virtue of specifying the tower operating pressure

• Estimate temperatures to assist tower simulation:

– Bubble point calculation on distillate at separator pressure gives reflux temperature for total condenser. If not a total condenser, flash calculation on distillate will give separator temperature for required vapour product

– Bubble point calculation on bottoms gives bottoms temperature

2.21

TOWER FEED TEMPERATURE

Consider feed temperature:

– If not specified, start design with feed at bubble point temperature and then optimize

– Aim to balance tower loadings above and below feed to take advantage of available column diameter

– Minimise cost of column refluxing (overhead condenser may represent a water or refrigeration consumer) and cost of column reboiling by exchanging feed with overhead vapour or bottoms product

2.22

ESTIMATING ACTUAL REFLUX RATIO AND ACTUAL NUMBER OF STAGES

General “Rule of Thumb”

R ACTUAL = (1.15 to 1.35) x R MIN

Use Gilliland correlation to calculate actual theoretical stages

for selected reflux ratio. Use safety factor of 10% or 3 trays,

whichever is larger.

2.23

TOWER SIMULATION BY PROVISION

Input data to be specified: • Tower feed rate and feed composition

• Vapor-liquid equilibrium data method

• Theoretical model of tower

• Fractionation specifications

• Variables to achieve specifications

• Tower pressure and initial estimates

2.24

FEED COMPOSITION

Real components• C1 to C6

Representation of hydrocarbons by pseudo-components

• C6+ hydrocarbons defined by pseudo-components

• Pseudo-components are narrow fractions characterised by VABP and gravity

• Pseudo-components are generated by Quest/Distex from plant data (feed distillation curve and feed gravity)

2.25

THEORETICAL MODEL OF TOWER

• Number of Stages

– Light ends fractionation : DPM Section III - I Table 2– Heavy hydrocarbon fractionation : Fluidity curve, DPM

Section III - I Figure 8

• Type of Condenser

• Feed Location

2.26

CONTACTING DEVICESCROSS-FLOW vs COUNTERCURRENT

2.27

AVAILABLE CONTACTING DEVICES

• Crossflow - Trays– Sieve– Valve– Jet

– Bubble Cap

• Counterflow - Packing and Sheds– Random Packing - Pall rings, IMTP, etc.– Structured Packing - Gempak, Flexipac, etc.– Grid– Sheds/Baffle Trays

2.28

CONTACTING DEVICE SELECTION

• Reduce investment cost

• Debottleneck throughput or improve product specification

• Save energy via lower pressure drop or higher efficiency

• Improve flexibility or turndown

• Provide reliable construction/easy maintenance

2.29

TYPES OF TRAYS

2.30

SIEVE TRAYS

• Most widely used fractionation internal

• Low cost

• Excellent data backup via FRI and commercial experience

• 2 - 3 to 1 turndown

• Non-proprietary

2.31

VALVE TRAYS

• Greater turndown than sieve trays, up to 5 to 1, due to self-adjusting open area for vapor flow

• Marginally higher cost

• Proprietary designs for valve trays from vendors. Nutter and Koch (Glitsch) offer valve trays nearly equivalent in performance

• Nutter also offers a fixed open valve type (V-Grid). Less flexible than valve tray, but no moving parts (like sieve tray)

2.32

TYPES OF VALVE

LIQUID FLOW

2.33

VAPOUR AND LIQUID FLOW PATTERNS THROUGH SIEVE AND V-GRID TRAYS

Vapour Flow Liquid Flow

(Side View) (Top View)

2.34

JET TRAYS

• Directional tabs punched at 20 degree incline from tray deck. Vapour flow helps propel liquid across tray

• Developed in-house in the 1950’s

• High liquid load capacity

• Tray efficiency generally about 20% lower than sieve tray

• Used mainly for pumparounds in pipestills, FCC fractionators, etc., so that these sections do not govern tower diameter

2.35

BUBBLE CAP TRAYS

• Standard tray device until 1950’s, now nearly obsolete. Still found in a few older vacuum pipestills

• High investment cost, otherwise performance characteristics similar to sieve trays (better turndown)

• Maintenance and installation difficult

2.36

BUBBLE CAP TRAYS

2.37

Tray Type Capacity Efficiency Cost Per Unit Area Flexibility* Remarks

Sieve Medium tohigh.

High. Equal toor better thanother traytypes.

Lowest of all trayswith downcomers.

Medium. 3/1can usually beachieved.

First choice for mostapplications; extensivedesign data available

Valve Medium tohigh; as goodas sieve trays.

High. As goodas sieve trays.

Medium. About 10%greater than sievetrays.

High. Possiblyup to 5/1.

Not recommended formoderate to severefouling services.

NutterV-Grid

Medium tohigh; as goodas sieve trays.

High. As goodas sieve trays

About the same assieve trays.

Medium.Slightly higherthan sievetrays.

Good alternative tosieve trays. Increasesrun lengths in foulingservices.

Jet Highest at lowpressure andhigh liquidrates

Low tomedium.

Low to medium.About 5 % higherthan sieve trays.

Low. 1.5 or 2/1. Consider only whenliquid rate exceeds 4.0gpm/in. of diameter perpass.

Bubble Cap Medium tohigh, exceptlow to mediumat high liquidrate.

Medium tohigh.

High. At least twicethe cost of sievetrays.

Medium tohigh 5/1 orslightly higher.

Use for high flexibilitywhere fouling of valvetrays may be a problem.

UOP MD,ECMD

Very High. Low to Medium High. Paying forproprietary know-how.

Low. (<2/1) Can be installed on verylow tray spacings.Consider for revampswhere no other device isacceptable. Notrecommended forfouling services.

*Ratio of maximum to minimum vapor loads at which tray efficiency remains above about 90% of its design value.

TRAYS - SUMMARY OF CHARACTERISTICS

2.38

PACKING

• Pall rings most popular packing since late 1960’s.

• Newer random packings, i.e. IMTP, Nutter rings, and CMR, now provide higher capacity than pall rings.

• More recently available structured packings provide significantly higher capacity and efficiency.

• Packing costs are usually higher than trays.

• Low pressure drop is an important advantage, especially in vacuum distillations.

2.39

RANDOM PACKING

2.40

CMR PACKING

2.41

STRUCTURED PACKING

2.42

PACKING SELECTION DIAGRAM FOR IMPROVING TOWER PERFORMANCE

Pt. Packing TypesNo.

Pt. Packing TypesNo.

Pt. Packing TypesNo.

RANDOM PACKINGS STRUCTURED PACKINGS

1. 1” Pall Ring #25 IMTP #1.5 CMR

2. 1.5” Pall Ring #40 IMTP #1 Nutter Ring #2 CMR

3. #1.5 Nutter Ring #2.5 CMR

4. 2” Pall Ring #50 IMTP #2 Nutter Ring Base #3 CMR

5. #2.5 Nutter Ring

6. #70 IMTP #3 Nutter Ring #4 CMR

1. FLEXIPAC 1Y GEMPAK #4A(3)

MELLPAK 500Y

2. GEMPAK #3A(3)

MELLPAK 350Y MONTZ B1-300 FLEXIPAC 1.4Y FLEXIPAC 1.6Y INTALOX Structured 1T

3. FLEXIPAC 2Y GEMPAK #2A (3) MELLAPAK 250Y MONTZ B1-250

4. GEMPAK #1.5A (3) INTALOX Structured 2T MONTZ B1-200

4.5 FLEXIPAC 2.5Y 5. GEMPAK #1A (3)

INTALOX Structured 3T MONTZ B1-125 INTALOX Structured 4T

6. FLEXIPAC 3Y MELLAPAK 125Y INTALOX Structured 5T MONTZ B1-100

7. FLEXIPAC 4Y GEMPAK #0.75 AT

2.43

WHEN TO USE PACKING

• In Existing Towers

– To Increase Throughput– To Improve Product Yield or Purity

• In New Towers

– Vacuum Distillation– Low Pressure Towers (Not Moderate to High

Pressure Towers)

2.44

PACKING IMPROVES PERFORMANCE TWO WAYS

2.45

ANCILLARY TOWER INTERNALS NEEDED IN PACKING INSTALLATIONS

2.46

TYPICAL LIQUID DISTRIBUTORSNarrow Channel

Distributor

2.47

OTHER PACKED TOWER INTERNALS

2.48

GRID

• High open type of stacked packing, used mainly for deentrainment in wash zones.

• High resistance/tolerance to fouling.

• Glitsch Grid only type of grid available from 1965 to mid - 80’s. Now Nutter and Koch provide competitive devices.

2.49

GRIDS

• High Capacity, Low Efficiency

• Fouling, Coking, Heat Transfer Services

2.50

TYPICAL VACUUM PIPESTILL

2.51

SHEDS

• Two configurations available– Baffles extending from wall to wall.– Disc & Donuts.

• Provide highest resistance to fouling of any device.

• Offer high capacity, but very poor efficiency.

• Used extensively in FCC fractionator slurry pumparounds, asphalt strippers, condensibles blowdown drums.

2.52

SHEDS/DISC AND DONUTS

2.53

COUNTERCURRENT DEVICES - SUMMARY OF CHARACTERISTICS

Device Capacity Efficiency Cost Per UnitArea

Flexibility Remarks

Packing (PallRings, MetalIntalox, NutterRings.)

Medium. Medium to High. Medium to low,depending onmaterial ofconstruction.

> 3/1 Good for PService. Mainlyused in vacuumpipestills and invarious high liquidrate absorbers.

StructuredPackingFlexipac; Montz,Gempak;Mellapak,Intalox –Structured.

Medium tovery highdepending onsize

Medium to veryhigh depending onsize used.

High – at least twotimes dumpedpacking cost.

>3/1 Best efficiency perunit of P.

Glitsch GridFlexigridSnapgrid

Very high Poor asfractionationdevice. Good forentrainmentremoval and heattransfer

Medium to high. Low: less than 2/1 Good for highvapor-low liquidservice to minimizeeffect ofentrainment. Usedin wash zones ofheavy hydrocarbonfractionators wheremoderate cokingoccurs.

Sheds and Discand Donuts

Very high. Poor asfractionationdevice.

Medium Low >1.5/1 Used in severefouling service; e.g.slurry pumparoundin cat fractionator.

2.54

TRAY HYDRAULICS

• Pressure Drop– Dry Tray Pressure Drop– Clear Liquid Height

• Downcomer Filling

• Downcomer Sealing

• Downcomer Velocity

• Downcomer Choking

• Entrainment

• Jet Flooding

• Froth/Spray Transition

• Weeping

2.55

FRACTIONATION TRAY HYDRAULICS

• Total vapor handling limitations– Governed PRIMARILY by vapour and liquid rates and overall

tower geometry (e.g. tower diameter, tray spacing, free area)– High tower loadings can result in excessive entrainment

from one tray to the tray above (jet flooding).– Tower geometry should be set to limit jet flooding to less

than about 90% to maintain tray efficiency.– Several flow regimes also possible depending on L/V ratio +

geometry.+ Froth--continuous liquid phase with discrete vapor bubbles is

the desired regime.+ Spray--high vapour rate (usually coupled with low liquid rate)

results in continuous vapour phase, excessive liquid entrainment and poor efficiency.

2.56

VAPOR HANDLING LIMITATIONS: ENTRAINMENT, JET FLOODING

• Entrainment: Liquid Carried to Tray Above

• Jet Flooding:

– Excessive Entrainment Overloads Downcomers

– Dense Froth Fills Inter-tray Space

– Efficiency Deteriorates

2.57

GENERATING ENTRAINMENT

2.58

JET FLOODING: IMPACT ON ENTRAINMENT AND TRAY EFFICIENCY

2.59

VAPOR HANDLING LIMITATIONS: FLOW REGIMES

• Froth: Discrete bubbles, continuous liquid phase

• Spray: high vapour rate, continuous vapour phase

– Liquid broken in droplets, “blowing”– Reduced vapour-liquid contact, low efficiency– Suppress the spray by larger open area, smaller holes, valves.

2.60

FROTH VERSUS SPRAY REGIME

2.61

LIQUID HANDLING LIMITATIONS

• Two downcomer (D.C.) functions:– Transfer the liquid to tray below– Disengage vapor from liquid

• Downcomer limitations:– Inlet velocity– Residence time– %Filling

2.62

VAPOUR RECYCLE INCREASES TRAY VAPOUR LOAD

2.63

DOWNCOMER INLET CHOKING

2.64

DOWNCOMER FILLING

2.65

PRESSURE BALANCE FOR A TWO PASS SIEVE TRAY

2.66

WEEPING, DUMPING

• Weeping

– Liquid flow through vapour openings– Low dry tray pressure drop

+ Low vapor rates, large hole area

– Sharp efficiency decline at high rates, when weeping exceeds 20% of liquid

• Dumping

– All liquid through vapour openings– Very low efficiency

2.67

EFFECT OF WEEPING ON EFFICIENCY

2.68

PERFORMANCE DIAGRAMS

• Boundary conditions that limit tower throughput.

• Each internal device (trays, packing) has a calculable Performance Diagram.

– Design Practices Manual can be used for most cases

– EMRE has access to FRI correlations and other data to assist for any internals not covered by DPM.

2.69

TYPICAL TRAY PERFORMANCE DIAGRAM

2.70

EFFECT OF TOWER LOADING ON TRAY EFFICIENCY VALVE TRAY VERSUS SIEVE TRAY

2.71

TOWER AND INTERNALS SIZING

• See procedures in DPM Section III

• For sieve trays: See DPM Section III - B

1. Calculate a trial tower diameter with assumed tray spacing

2. Size downcomers and set other tray details

3. Calculate % of jet flood

4. Calculate tray hydraulics

5. Repeat steps 1 - 4 if first trial unsatisfactory

6. Calculate flexibility

7. Balance the tray design

8. Calculate efficiency

2.72

MAIN TRAY DESIGN VARIABLES

• Tray diameter, spacing

• Number of tray passes

• Downcomer area, type

• Active area, open (hole) area

• Weir height, D.C. clearance

2.73

SINGLE PASS TRAY

2.74

TWO PASS TRAY

2.75

TRAY NOMENCLATURE - SINGLE PASS TRAYS

2.76

TRAY NOMENCLATURE - TWO PASS TRAYS

2.77

PASS ARRANGEMENT ON MULTIPASS TRAYS

2.78

STEPPED VERSUS SLOPED DOWNCOMERS

2.79

STRAIGHT, MODIFIED ARC, AND ARC-TYPE DOWNCOMERS

2.80

SIEVE TRAY DESIGN PARAMETERS

TYPICAL ALLOWABLE RANGETray Spacing, mm 300-750 200-900

Number of Passes 1 or 2 1-4

Outlet Weir Height, mm 50 0-100

Downcomer Clearance, mm 38 25+

38+(Fouling Service)

Hole Size, mm 13 3-25

19-25 (Fouling Service)

Hole/Bubble Area Ratio, % 6-10 3.5-15

Bubble/Tower Area Ratio, % 40-90 40-90

Outboard Downcomer Rise -- Chord Length at Least 65% of

Tower Diameter

Inboard Downcomer Width -- Inlet Width: 200 mm min.

Outlet Width: 150 mm min.

2.81

KEY TRAY PERFORMANCE PARAMETERS

• Jet Flooding

• Downcomer Filling (D.C. Flooding)

• Downcomer Inlet Velocity (Inlet Flood)

• Dry and Total Tray Pressure Drop

• Pressure Drop Under the Downcomer

• gpm/in. Weir or gph/ft Diameter

• Tray Flexibility

2.82

TURNDOWN

• Primary problem is weeping.

• Causes loss of efficiency resulting in poor fractionation.

• Fractional weepage up to 20% can usually be tolerated. If efficiency not critical, can be estimated to see if higher weeping percentage is okay.

• If weeping is severe, can cause loss of drawoff or pumparound.

• Simplest cure is blanking, but may result in spray regime at maximum loading.

• Operational cure is to over-reboil, but operating cost per unit throughput also increases.

2.83

EFFECT OF LIQUID RATE ON SIEVE TRAY TURNDOWN

2.84

DOWNCOMER SEALING TECHNIQUES

2.85

DESIGN CONTINGENCY

• Design strategy is to apply contingency to insure 90% chance of successful operation.

• Examples– Tray flooding – 90% of predicted– Packing flooding – 85% of predicted for Hydrocarbons

– 80% of predicted for Aqueous– Tray efficiency – Point efficiency debited 10%– Packing HETP – Predicted divided by 0.85

2.86

TRAY PROGRAMS

PRO/II PEGASYS

Sieve X X

Valve X X

Jet X X

Bubble Cap X X

Multi-pass X

Packing X X

THESE PROGRAMS PROVIDE:

- Designs- Ratings for existing internals- Hydraulic limitations- Efficiency calcs- Direct contact heat transfer calcs

2.87

OTHER TOWER INTERNALS

• Tray pass transitions

• Wire mesh deentrainment screens

• Tower inlets

• Tower drawoffs

• Reboiler drawoffs/returns

2.88

DEBOTTLENECKING

• Purpose– To increase throughput capacity.– To adapt an existing tower to a new service requiring

increased loadings.

• Always consider process alternatives first.

• When coupled with scheduled turnarounds, incremental cost of improvements is minimized.

• Extent of debottleneck often guided by amount of investment.

2.89

SIEVE TRAY DEBOTTLENECKING STRATEGY

2.90

CHEAP WAYS TO DEBOTTLENECK

• Reduce weir height to lower downcomer filling.

• Increase downcomer clearance or add shaped lip to lower downcomer filling if D.C. head loss is high.

• Change tray decks if more hole area or larger holes are needed.

2.91

MORE EXPENSIVE DEBOTTLENECKING BUT ALSO MORE EFFECTIVE

• Change downcomers to sloped or modified arc.

• Increase number of passes.

• Convert to higher capacity trays (MVG, NYE).

• Higher cost items:– Increase tray spacing and add straight side if needed.– Convert to packing or grid.– Use UOP’s MD tray if heavily liquid loaded.

2.92

APPLICATION GUIDELINES FOR DEBOTTLENECKING FRACTIONATION TOWERS

• Multipass trays

• MVG trays

• Nye tray inserts

• MD trays

• Random/structured packing

2.93

ENHANCED CAPACITY TRAY OPTIONS Vendor Tray Type Comments

Glitsch Mini-Valve • Limited ExxonMobil experience.

Nye • Enhanced downcomer.• Liquid rates >4 GPM / inch of weir• Best suited for high pressure applications

Superfrac • Enhanced downcomer (chordal to modified-arc)• Developing first ExxonMobil applications

Koch Engineering Bi-Frac • Fixed mini-valve.• Best suited for low pressure applications.• No ExxonMobil experience.

Max-Frac • Enhanced downcomer with valve tray decks and louvers at downcomer outlet.

• Limited ExxonMobil experience.

Norton Triton • Enhanced downcomer (chordal to modified-arc having slotted outlet at bottom).• No ExxonMobil experience

Nutter Engineering Mini V-Grid (MVG) • Fixed mini valve.• Best suited for low pressure applications• ExxonMobil experience

UOP Multiple Downcomer (MD)• 1960’s technology• ExxonMobil experience

Enhanced Capacity Multiple • MD with slotted sieve decks and other Downcomer (ECMD) improvements

• Limited ExxonMobil experience

2.94

ENHANCED CAPACITY TRAY OPTIONS

2.95

ESSENTIAL FEATURES OF UOP MD TRAY

2.96

SCHEMATIC OF MD TRAY OPERATION

2.97

MD AND ECMD TRAY UNIT CELLS

2.98

DEBOTTLENECKING PACKED TOWERS

• Increase size of packing if lower efficiency can be tolerated.

• Convert to structured packing if efficiency is to be maintained.

• Check liquid distributor hydraulics and modify if needed.

2.99

APPLICATION GUIDELINES FOR DEBOTTLENECKING FRACTIONATION TOWERS (1,2)

Relative Capacity Increase @ Constant Separation EfficiencyPressurePsia

0 - 20% 20 - 30% 30 - 40% 40 - 60%

LOW

Under50

See Note (3)

2-Pass Tray, MVG4-Pass Tray

Nye TrayRandom Packing

Structured Packing

4-Pass Tray

Random PackingStructured Packing

StructuredPacking

StructuredPacking

MODERATE

50

to

165

2-Pass Tray4-Pass Tray

Nye TrayMD Tray

Random PackingStructured Packing

4-Pass Tray

MD Tray

Random Packing

StructuredPacking

MD Tray

RandomPacking

StructuredPacking

StructuredPacking

HIGH

Above165

2-Pass Tray4-Pass Tray

Nye TrayMD Tray

Random Packing

4–Pass Tray

MD Tray

Random Packing

MD Tray

RandomPacking

MD Tray

NOTES:

1. Internals are listed in order of increasing approximate total erected cost (TEC). Carbon steel is assumed for all trays and stainless steel for packing.The cost of MD trays and random packing are generally very close. However, if stainless steel MD trays are required, random packing will generally beless expensive.

2. Structured packing is not recommended for pressures greater than 165 psia or liquid loading greater than 20 gpm/ft 2 (in distillation).

3. Multipass trays and Nye trays are not recommended for applications in the spray regime, which is typical of many systems operation below 50 psia.Contact your Fractionation Specialist for alternative trays for this regime.

Reference: ER&E Report EE.76E.91

2.100

DISTILLATION - VENDOR INFORMATIONKOCH-GLITSCH

Ceramic

RandomHigh Capacity

StructuredGauze

StructuredCascade

Mini-Rings

Flexigrid Flexmax Structured

2.101

DISTILLATION - VENDOR INFORMATIONGLITSCH / NUTTER

Glitsch Ballast Tray

Glitsch

Nutter Cartridge Trays

Nutter Random Packing

Nutter Internals

Nutter Snap-Grid

2.102

DISTILLATION - VENDOR INFORMATIONNORTON / NORPRO

NortonInternals

NortonInternals

Norton Random Packing

Norton CeramicPacking

Norton Trays

Norton PlasticPacking

Norton RandomPacking

2.103

DISTILLATION - VENDOR INFORMATIONSULZER

SulzerAbsorption

Sulzer Distillation

SulzerTowers

Sulzer Tower Internals

SulzerMellapak

SulzerMellaring

Graham Vacuum Ejectors

2.104

http://www.nortoncppc.com

http://www.koch-glitsch.com

DISTILLATION - USEFUL WEB SITES

http://www.sulzerchemtech.comSulzer Chemtech (Nutter)

Norton (Norpro)

Koch-Glitsch

Montz

UOP

Graham Ejectors http://www.graham-mfg.com

http://www.uop.com

http://www.montz.de

2.105

GLOSSARYActive area The tray deck area where the liquid-vapour contacts take

place.

Antijump baffle Tower internal device placed over the inlet of an inboard downcomer in order to prevent liquid from one side from jumping to the other side. See figure in the text.

Arc downcomer A type of downcomer. See figure in downcomer configuration section.

Baffle sections Horizontal or low-angle contacting devices creating cascades of liquid for contact with rising vapour. There are two basic types of baffle sections: sheds, and disks and donuts. See the figures in the text.

Blank tray Tray used to collect liquid from higher trays or packing. Blank trays do not provide vapour-liquid contact. A synonymous term is chimney tray.

Bubble cap tray A type of tray. The vapour goes through risers and inverted caps making contact with the liquid when leaving the caps. See the figures in the text.

Cartridge tray Prefabricated tray and downcomer assembly. See figure in text.

2.106

GLOSSARY (CONTINUED)Chimney tray Tray used to collect liquid from higher trays or packing.

Chimney trays do not provide vapour-liquid contact. A synonymous term is blank tray.

Choking Accumulation of froth bridged over the inlet of a downcomer, slowing down the transfer of liquid to the trays below.

Chordal downcomer Vertical straight downcomer across a chord of the tower cross section. Synonymous with straight downcomer. See Figure Downcomer Configuration section

Column A vertical vessel containing contacting devices such as trays or packing, used to perform separations such as distillation or extraction. A synonymous term is tower.

Counter-current Devices in which the liquid flow is truly countercurrent to the devices vapor flow.

Cross-flow devices Devices in which liquid flows horizontally across a flat plate.

Debottlenecking Removal of a process or equipment constraint.

Demisting Elimination of entrained liquid droplets at the top of a packed bed or a trayed tower.

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Disc & donuts A type of baffle section. See the figures in the text.

Downcomer area The cross-sectional area of downcomers.

Downcomer clearance The vertical distance between the bottom of the downcomer and the tray deck.

Downcomer contraction Pressure drop of the liquid passing under the downcomer. pressure drop

Downcomer filling Height of liquid in the downcomer. It is often expressed in inches of clear liquid or a percent (clear liquid) of the tray spacing.

Downcomer flooding Overloading of the tray interspace with liquid, caused by high downcomer filling.

Downcomer rise The horizontal radial distance between the center of the chord of a straight outboard downcomer and the vessel wall.

Downcomer seal Hydraulic seal of the downcomer outlet. See figures in the text.

GLOSSARY (CONTINUED)

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Downcomers Tower internals that allow the tray liquid to pass to the tray below.

Dry tray pressure drop Part of the pressure drop that is not related to the presence of the liquid on the tray, that is, the pressure of the vapor through the contacting device.

Dumped Packing Packing type, consisting of small (2-in. is typical) devices with large open space, placed in the tower (dumped) in random orientation. A synonymous term is random packing.

Dumping Weeping of all the liquid, so that no liquid flows over the weir.

Entrainment Liquid carryover by the vapour to the tray above.

Flexibility Refers to capacity related flexibility. See Turndown.

Flooding Overloading of the tray interspace with liquid. Frequently, the term refers to jet flooding.

Flow regimes The movement of liquid and vapour on a tray.

GLOSSARY (CONTINUED)

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GLOSSARY (CONTINUED)

Free area The tray cross-sectional area available for vapour flow.

Froth A flow regime in which vapor passes through a liquid on the tray as discrete bubbles of irregular shape.

Grids Countercurrent contacting devices fabricated in panels and installed in an ordered manner. In contrast to structuredpacking, grids provide wide clearances. See the figures in the text.

Hole area The open area provided within the bubble area to permit vapour to enter, contact and pass through the liquid on the tray.

Inboard downcomer Downcomer positioned by the vessel wall.

Jet Flooding Overloading of the tray interspace with liquid, cause by excessive entrainment.

Modified arc downcomer A type of downcomer. See Figure in Downcomer Configuration section.

Multiple downcomer tray Proprietary type of tray. See Figure in Downcomer Configuration section.

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Outboard downcomer Downcomer positioned by the vessel wall.

Packing Devices that provide countercurrent vapor-liquid contact in distillation columns.

Percent jet flood The ratio, expressed as a percent, of the vapor velocity (%flood) between the trays. V, divided by the maximum vapor

velocity that will not cause flooding.

Plates Contact points of all the vapour and liquid in a column, such as it occurs on column trays. The term

theoretical plates is used to indicate that equilibrium is reached at the contact point between all the vapor and all the liquid. The actual plates reflect the obtained tray efficiency. A synonymous term is stages.

Pumparound Heat removal from a stream pumped from a tray to a higher tray.

Random packing Packing type, consisting of small (2-in. is typical) devices with large open space, placed in the tower (dumped) in random orientation. A synonymous term is dumped packing.

GLOSSARY (CONTINUED)

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GLOSSARY (CONTINUED)

Seal pan Tower internal device placed over the inlet of an inboard downcomer in order to prevent liquid from one side from jumping to the other side. See figure in the text.

Sheds A type of baffle section. See Figure in the text.

Sieve tray A perforated plate type of tray.

Sloped downcomer A type of downcomer. See Figure in Downcomer Configuration section.

Spray A flow regime in which a gas get issuing from the orifice shatters some liquid into droplets.

Stages Contact points of all the vapour and liquid in a column, such as occurs on column trays. The term

theoretical stages is used to indicate that equilibrium is reached at the contact point between. The actual stages reflect the obtained tray efficiency. A synonymous term is plates.

Stepped downcomer A type of downcomer. See Figure in Downcomer Configuration section.

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GLOSSARY (CONTINUED)Straight downcomer Vertical straight downcomer across a chord of the tower

cross section. Synonymous with chordal downcomer. See Figure in Downcomer Configuration Section.

Structured packing Countercurrent contacting devices fabricated from thin crimped sheets of metal and installed in layers having a fixed orientation. See the figures in the text.

Superficial velocity Velocity based on the tower diameter rather than thecross-sectional area available for flow.

Support ring Horizontal ring welded to the tower walls that are used to support a tray.

Tower See column.

Tray loadings Tray vapour and liquid rates.

Tray pass number The number of individual paths of liquid on a tray.

Tray spacing The vertical distance between two trays.

Tray turndown The ration of maximum to minimum tray loadings in a range over which acceptable performance is achieved.

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GLOSSARY (CONTINUED)

Truss Tray support beam.

Turndown Operation at reduced capacity.

Ultimate capacity The largest vapour load a tower can handle, as predicted by the Stokes law on droplet entrainment.

Valve tray A type of tray with contacting devices that can be openedand closed. See the figures in text.

Waste area Any area in the active area that is farther than 3 in. from the edge of a contacting device.

Weeping Liquid flow through the tray openings.

Weir A vertical strip at the inlet or outlet of a tray used to maintain liquid height on the tray or a liquid seal at the outlet of the downcomer. See figure in text.