2/28/2014 Distillation Column Tray Selection & Sizing – 1 - Separation Technologies

http://seperationtechnology.com/distillation-column-tray-selection-1/ 1/30

Separation Technologies Site Dedicated to Separation Process Industry

Search

Home

About Us

Privacy Policy

Contact Us

Site Map

Distillation Column Tray Selection & Sizing – 1

Introduction:

Once the process design stage ends, the equipment design begins. This stage of design converts process requirements into actual hardware.

One of the most prominent hardwares used for mass transfer is tray. Tray columns are widely used in various types of mass transfer operations. All the

simulation results, which predict a certain number of theoretical stages, can be converted to actual trays depending upon tray efficiency for a particular

service.

In any conventional tray vapour rises through the liquid pool on the tray deck and then disengages from the liquid in the space above the deck. Liquid

enters the tray from a downcomer above and leaves via a downcomer below.

Conventional Tray has three functional zones:

1. Active area for mixing vapour and liquid: This is the zone where mass transfer occurs.

2. Vapour space above the active area: This is the zone in which liquid is separated from vapour.

3. Downcomer between trays. This zone has two functions, first moving liquid from one contacting tray to another and second disengaging vapour

from liquid.

Each of these zones takes up vertical and horizontal space in the tower.

Selection Guide for Tray Column:

► Tower Packing ► Packing Trays ► Liquid Packing ► Pump Selection

2/28/2014 Distillation Column Tray Selection & Sizing – 1 - Separation Technologies

http://seperationtechnology.com/distillation-column-tray-selection-1/ 2/30

The factors discussed below influence the choice between trays & packings. As these are guidelines for selection of trays or packings for a particular

service, it is recommended to analyze each design case on its own merit for selection.

Sr. No.System Favouring Tray

Column System Favouring Packed Column

1Solid handling Vaccum system

2High liquid rate Low pressure drop application

Feed

composition

andtemperature

Revamps- The pressure dropreduction3

can be

translated into

capacitygain,

an

variable

energy gain or separation improvement.

4Large diameter columns Small diameter columns< 900 mm

5Performance prediction is easy Corrosive system

6Less weight saving in cost

ofFoaming system

foundations and supports

7Interboilers, intercondensers, coolingLow liquid holdup for

reducingcolils, & side draw

polymerisation and degradation.

8High turn downrequirements Batch Distillation

9Chemical reactions

The industry, based on its experience, has standardised the type to be used in certain services. If this reference is not available the guideline as perAppendix 1 are to be used

Types of Tray

2/28/2014 Distillation Column Tray Selection & Sizing – 1 - Separation Technologies

http://seperationtechnology.com/distillation-column-tray-selection-1/ 3/30

The particular tray selection and its design can materially affect the performance of a given distillation, absorption, or stripping system. Each tray shouldbe designed so as to give as efficient a contact between the vapour and liquid as possible, within reasonable economic limits.

Valve tray:

Valve trays are perforated sheet metal decks on which round, liftable valves are mounted. The vapour flows through valves which are installed parallelto the outlet weir. Valve trays combine high capacity and excellent efficiency with a wide operating range.

Advantages: Excellent liquid/ vapour contacting. Higher capacity.

Higher flexibility than sieve trays. Can handle higher loadings. Low-pressure drop than bubble cap.

Sieve tray:

Sieve trays are flat perforated plate in which vapour rises through small holes in tray floor, & bubbles through liquid in fairly uniform manner. They havecomparable capacity as valve trays.

2/28/2014 Distillation Column Tray Selection & Sizing – 1 - Separation Technologies

http://seperationtechnology.com/distillation-column-tray-selection-1/ 4/30

Advantages:

Simple construction Low entrainment,

low cost Low maintenance cost Low fouling tendency

Disadvantages:

Less-flexible to varying loads than other two types

Bubble cap tray:

Vapour rises through risers or uptakes into bubble cap, out through slots as bubbles into surrounding liquid on tray. It is mainly used in special

applications.

Advantages:

Moderate capacityMost flexible (high & low vap. & liquid rates)Can provide excellent turndown.

Disadvantages:

High entrainment, High fouling tendency High cost, High pressure drop

2/28/2014 Distillation Column Tray Selection & Sizing – 1 - Separation Technologies

http://seperationtechnology.com/distillation-column-tray-selection-1/ 5/30

Dual flow trays:

A dual flow tray is a sieve tray with no downcomers. This tray operates with liquid continuously weeping through the holes. Due to the absence ofdowncomers, dual flow tray gives more tray area hence a greater capacity than any of the common tray types. They are ideal for revamp where ifsome efficiency can be sacrificed for more capacity. They are least expensive to make and easiest to install and maintain.

Dual Flow Tray Baffle Tray

Baffle trays:

For a baffle tray column the gas flows upwards through the baffle openings and in doing so contacts the liquid showering down from one baffle to thenext. Baffle tray columns have almost same flooding capacity as cross flow trays. Types of baffles used are disc & donut and segmental baffles forvarious column diameters.

Dual flow and baffle trays are used for fouling applications, solid / slurry handling services, corrosive services.

Proprietary types of trays:

MD Trays – Linde / UOP,Ripple Trays – Stone & Webster Engg. Corp.Rectangular Valve (BDH),ValveGrid (MVG/SVG),SHELL HIFI, ConSep Trays – SulzerBallast Tray,

2/28/2014 Distillation Column Tray Selection & Sizing – 1 - Separation Technologies

http://seperationtechnology.com/distillation-column-tray-selection-1/ 6/30

Flexitray, Bi-FRAC, SUPERFRAC and ULTRAFRAC Trays – Koch-Glitsch Engg.Co., Tunnel Trays- Montz,Nye trays- Nye Engg Co,

Comparison between Common Conventional Trays.

Sr. Factors Sieve Tray Valve Tray Bubble-Cap Tray Dual-Flow TrayNo.

1 Capacity High HighModerately High Very High

2 Efficiency High HighModerately High Least

3 Turndown ~50% ~25-30%10% Least

4 Entrainment Moderate ModerateHigh

Low to moderate

5 Pressure Drop Moderate ModerateHigh

Low to Moderate

6 Cost Low ~1.2 times~ 2-3 times of sieve Least

sieve traystrays

7 Maintenance Low Low toRelatively High Low

Moderate8 Fouling Low Low to High: Tends to collectExtremely LowTendency Moderate Solids9 Effects of Low Low to High Very LowCorrosion moderate

Proprietary, Some informationDesign Available.Instability10 Well Known but readily Well Knowninformation can occur in largeavailable dia. (>8 feet)Often used Where high Extremely low Liquid Capacity revamps,Main flow & Where11 when turndown turndown is Highly fouling andApplication leakage must beis not critical required corrosive servicesminimized

Tray Parameters

a) No. of passes (Np):

The numbers of flowpaths of liquid on tray are 1, 2, 3 or 4 as per liquid capacity requirement of column. From a capacity viewpoint, a liquid rategreater than 6 gpm / inch of weir (weir loading), is the rate at which a higher number of flow paths should be considered. The maximum allowable weir

2/28/2014 Distillation Column Tray Selection & Sizing – 1 - Separation Technologies

http://seperationtechnology.com/distillation-column-tray-selection-1/ 7/30

loading is 13 gpm/in of weir length. If the weir loading exceeds this the tray needs redesign with higher number of passes.

b) Tray Spacing (S):

Tray spacing is the distance between two trays. Generally tray spacing ranges from 8 to 36 inches (200 mm to 900 mm). Prime factor in setting tray

spacing is the economic trade-off between column height and column diameter. Most columns have 600 mm tray spacing. Cryogenic columns havetray spacing of 200-300 mm.

c) Outlet Weirs (hw):

An outlet weir maintains a desired liquid level on the tray. As the liquid leaves the contacting area of the tray, it flows over the tray weir to enter intothe downcomer.

d) Downcomer Clearance (hcl):

This is the vertical distance between the tray floor and the bottom edge of the downcomer apron. The Normalpractice is to use a downcomerclearance of 1/2 inch less than the overflow weir height to provide a static liquid seal

e) Inlet Weirs & Recessed Seal Pans:

Inlet weirs and recessed seal pans are primarily used for achieving a downcomer seal in cases where a potential positive sealing problem exists andclearance under downcomer is limited

f) Downcomers:

Passage of liquid from the top tray to the bottom of tray occurs via downcomers. Downcomers are conduits having circular, segmental, or rectangular

cross sections that convey liquid from upper tray to a lower tray in a distillation column.

g) Downcomer width (Chord height, WDC):

It is maximum horizontal distance between tower wall and weir.

h) Flow path length (FPL):

2/28/2014 Distillation Column Tray Selection & Sizing – 1 - Separation Technologies

http://seperationtechnology.com/distillation-column-tray-selection-1/ 8/30

Flow path length is the distance between the inlet downcomer & outlet downcomer. The minimum limit for flow path length is 400 mm in order toprovide good contacting between vapour and liquid. This is also necessary for the mechanical reason of providing tray manway.

i) Tray deck thickness (t):

Trays normally used in commercial service need a minimum material thickness to provide structural strength (personnel walk on them duringinstallation) and corrosion allowance. A thickness of 10 to 12 gauge (2.5 to 3.5 mm) is customary for carbon steel, while 12 to 14 gauge (1.9 to 2.5

mm) is used for stainless steel trays (in general no C.A. for SS)

j) Hole pitch (P):

Centre to centre distance between holes is called pitch. Normal practice is to use a hole pitch to hole diameter ratio between 2.2 to 3.8.

k) System (Derating) factors:

Derating factors are often closely related to the foaming tendency of the system. Higher the foaming tendency, the lower is the Derating factor. System

factors are used in three of the rating correlations (jet flood, down comer backup flood, down comer choke) to account for system effects onhydraulic capacity limits. It includes both foaming effects and high vapour density.

l) Bubbling (Active) Area (AB):

Bubbling area is the column area, which is actually available for vapour bubbling through liquid. It can be defined as column area minus downcomer

areas, downcomer seal & large calming zones.

m) % Hole Area:

This is the ratio of hole area to bubbling area. The default practice is to target a hole area of 8 to 10 % of bubbling area for pressure services. Theacceptable range for percentage hole area is 5 % to 15 %. However for some critical services, we can go % hole area up to 17-17.5% provided that

weeping is under control. Hole areas below 5 % are not used.

2/28/2014 Distillation Column Tray Selection & Sizing – 1 - Separation Technologies

http://seperationtechnology.com/distillation-column-tray-selection-1/ 9/30

n) Anti jump baffles:

Anti jump baffles plates suspended vertically above centre or off centre downcomers, which stops liquid jumping from one deck onto the oppositedeck, flow path

Tray Hydraulic Parameters

Following are the some important output parameters of tray hydraulics.

a) Flood:

Jet Flood:

In spray regime operation flooding is brought about by excessive vapour flow, causing excessive liquid to be entrained in the vapour up the column. In

froth and emulsion flows regimes operation excessive froth entrainment in the vapour up the column causes jet flooding.

Down-comer Back-up Flood:

Occurs when the pressure available for a given height of liquid and froth in the downcomer cannot overcome the total pressure drop across the tray

This pressure imbalance causes the froth in the downcomer to start backing-up until it reaches the tray above, causing an increased accumulation ofliquid on it. It requires high liquid and vapour loads.

Downcomer Choke Flood:

The mechanism by which this type of flooding occurs is one related to frictional pressure losses in the downcomer becoming excessive. In addition, the

vapour carried into the downcomer must separate from the liquid and then flow counter-current to the liquid entering the downcomer. When the

combination of vapour exiting and the liquid entering becomes excessive, the downcomer entrance is choked causing the liquid to backup on the tray.It requires relatively high liquid rates, surpassing a velocity limitation on the downcomer.

b) Weeping/Dumping

The pressure exerted by the vapour is insufficient to hold up the liquid on the tray. Therefore, liquid starts to leak through perforations.

2/28/2014 Distillation Column Tray Selection & Sizing – 1 - Separation Technologies

http://seperationtechnology.com/distillation-column-tray-selection-1/ 10/30

c) Pressure Drop:

Pressure drop is an important consideration while designing a tray. It becomes more critical for the vacuum systems than the high-pressure systems.The tray pressure drop is viewed as the sum of the pressure drop through the valves or sieves and pressure drop through the aerated liquid on the tray

deck.

d) Turndown ratio:

Turndown ratio defines the range of vapour load between which the column can operate without substantially affecting its’ primary separation

objective (i.e. fractionation efficiency) or over which acceptable tray performance is achieved. The tray efficiency stays at or above the design valuethroughout the turndown range.

Tray Sizing

The sizing procedure is an iterative calculation. A preliminary design is set, and then refined by checking against the performance correlations until anadequate design is achieved. The sizing calculations are performed at the point where column loading is expected to be highest and lowest for each

section, i.e.,

i) The top tray

ii) Above every feed, product drawoff, or point of heat addition or removal.

iii) Below every feed, product drawoff, or point of heat addition or removal.

iv) The bottom tray.

v) At any point in the column where the calculated vapour or liquid loading peaks

The sizing is done at all above load points and also detailed sizing is checked at all above load points. All design parameters given in the designprocedure below are calculated at all above load points at turndown and turn-up loads so that the feasibility of design for varied loads is tested.

a) Preliminary determination of tower area:

The methods used for determining tower diameter are:

“C” Factor Method

2/28/2014 Distillation Column Tray Selection & Sizing – 1 - Separation Technologies

http://seperationtechnology.com/distillation-column-tray-selection-1/ 11/30

Nomograph Method

FRI Tray design handbook

However in this technical guideline we are describing method using C-Factor Method.

C-Factor Method:

The following calculations are done at all the loading points mentioned above and diameters are found separately. If the difference in calculated

diameter at different sections exceeds 20 percent, different diameters for the sections are likely to be economical. The section having different diameter

should be at least 20ft in length else same diameter can be maintained.

i. Tray Area

Assume appropriate values for following parameters (based on system requirements) for preliminary diameter calculation.

dH = Hole diameter, inches (¼ to ½ inch) S = Tray spacing, inches (18 – 24″)

hct = Clear Liquid height at the transition from the froth to spray regime, in of liquid.

Assumption: The starting values for these can be dH=1/4″, S=24″, h ct=2″

Calculate C-Factor (CSB) using following Kister and Haas Correlation:

ii. Flood Velocity Calculation

This is the velocity of upward vapour at which liquid droplets are suspended. Calculate Flood Velocity (uN) using following equation:

2/28/2014 Distillation Column Tray Selection & Sizing – 1 - Separation Technologies

http://seperationtechnology.com/distillation-column-tray-selection-1/ 12/30

iii. Net Area Calculation

The net area represents smallest area available for vapour flow in the inter-tray spacing. Calculate Net Area (AN) from the flood velocity using

following equation: Assume the column is to be designed for 80% of flood.

iv. Downcomer Area Calculation Calculate downcomer area (AD) from clear liquid velocity in downcomer using following formula:

Where,

QL = Liquid Flow Rate, ft3/s

VCL = Clear Liquid Velocity in Downcomer

Value of VCL obtained from table below. No derating factor is required for this calculation, as VCL values have taken care of foaming

Table: Recommended VCL values for different foaming tendencies

Foaming ExampleVCL in downcomer, ft/s18-in 24-in 30-in

TendencySpacing Spacing Spacing

Low pressure (<100-psia) light 0.5-0.6

med. pressure (100-300 psia)

2/28/2014 Distillation Column Tray Selection & Sizing – 1 - Separation Technologies

http://seperationtechnology.com/distillation-column-tray-selection-1/ 13/30

Low hydrocarbon, 0.4-0.5 0.5-0.6

stabilizers, air-water simulators

Medium

Oil systems, crude oil distillation,absorbers,

0.3-0.4 0.4-0.50.4-0.5

hydrocarbon

High Amine, glycerine, glycols, high-pressure 0.2-0.250.2-0.2-0.3

(>300-psi) light hydrocarbons 0.25

v. Tower Diameter Calculation

TotalTowerArea (AT) = AD + AN

b) Preliminary tray layout:

A Preliminary layout is needed as layout influences the column size.

Downcomer Layout:

Check the % of Downcomer area with respect to tower area:

2/28/2014 Distillation Column Tray Selection & Sizing – 1 - Separation Technologies

http://seperationtechnology.com/distillation-column-tray-selection-1/ 14/30

The Fractional area should around 10% but avoid less than 8% in normal circumstances. Note that AD should in no circumstance be less that 5% of

AT

Net Area (AN):

The total tower cross-section area AT less the area at the top of the downcomer (sometime refer to as free area, the term free area.)

The net area represents the smallest area available for vapour flow in the inter-tray spacing.

AN = AT - AD

Bubbling (Active) area (AB):

The total cross-section area AT less the area at the inlet & outlet downcomer is called as bubbling area.

AB = AT - ADT - ADB

Below figure shows the Typical Tray Layout.

Weir Length and Downcomer Width: SinglePass Tray:

2/28/2014 Distillation Column Tray Selection & Sizing – 1 - Separation Technologies

http://seperationtechnology.com/distillation-column-tray-selection-1/ 15/30

The calculation of Weir Length and Downcomer Width involves geometrical relationship between downcomer area, downcomer width, anddowncomer length.

Following Figure shows downcomer geometry:

Calculate downcomer width and weir length using following method

? = sin-1(h/R)

w = 2*R COS (?) or w = 2*(R2 – h2)0.5

?/2 = ?/2 - ?

2/28/2014 Distillation Column Tray Selection & Sizing – 1 - Separation Technologies

http://seperationtechnology.com/distillation-column-tray-selection-1/ 16/30

Sector area = ASECT = ? R2 * ? / (2 * ?)

Area of triangle (ABC) = ATRI. = w*h/2

Where,

Lw = Weir Length = w* (1-fractional weir blockage)

wdc = Downcomer Width = R -h

AD = Adc = Downcomer Area

Fractional weir blockage is the fraction of total weir length that is available for liquid flow by using picket and fence type of weir. Blocked (Picket

fence) weirs are used for handling low liquid loading.

Down-comer area

AD = ASECT- ATRI

Two Pass Tray:

Two pass trays have alternating arrangements of one center-downcomer and two side-downcomers.

2/28/2014 Distillation Column Tray Selection & Sizing – 1 - Separation Technologies

http://seperationtechnology.com/distillation-column-tray-selection-1/ 17/30

The side downcomer area can be calculated as that for single pass tray. It should be noted that side down-comers are on both sides.

Center downcomer calculations can be done as follows in similar manner as side down-comer:

? = sin-1 (h/R)

w = 2*R COS (?1) or w = 2*(R2 – h2)0.5

? = 2*(?/2- ?)

Sector area = ASECT = ? R2 * ? / (2 * ?)

Area of center downcomer = Area of circle -2*area of sector + 2*Area of Triangle Area of downcomer = ?*R2 – 2* ASECT + h1*w1

In case of more than two pass trays we have to define one more parameter, i.e. off-center downcomer location from centerline. This needs to be doneon a case-by-case basis.

2/28/2014 Distillation Column Tray Selection & Sizing – 1 - Separation Technologies

http://seperationtechnology.com/distillation-column-tray-selection-1/ 18/30

Liquid Flow Path Length (FPL):

ForSinglePassTray:

FPL= (tray diameter) minus (side DC width of the tray) minus (bottom width of DC of tray above)

Where,

w1dc

=Downcomer width (Centre downcomer, Bottom ofDowncomer)

w2dc

=Downcomer width (Side downcomer, Top of Downcomer)

w3dc

=Downcomer width (Centre downcomer, Top ofDowncomer)

=Downcomer width (Side downcomer, Bottom of

2/28/2014 Distillation Column Tray Selection & Sizing – 1 - Separation Technologies

http://seperationtechnology.com/distillation-column-tray-selection-1/ 19/30

w4dc Downcomer)

C) Detailed Design

Flooding Check:

The flooding check is performed using following Correlations:

1. Kister and Haas correlation.2. Downcomer choke-Koch correlation3. Fair’s correlation

4. Smith et al. correlation

1. Jet Flood: Kister and Haas correlation

This correlation possess following advantage:

- It gives a close approximation to the effects of physical properties, operating variable, and tray geometry on the flood point.

- It describes spray regime entrainment.

- It was derived from a much wider database of commercial and pilot-scale column data.

- It can predict sieve and valve tray entrainment flooding within ± 15 and ± 20 percent respectively.

This correlation possess following restriction:

Sr.no. Factors Applicability1 Flooding Mechanism Entrainment (Jet) flood only

2 Tray Type Sieve or Valve trays only3 Pressure 1.5-500 psia4 Gas Velocity 1.5-13 ft/s

5 Liquid Load 0.5-12 gpm/in of outlet weir6 Gas Density 0.03-10 lb/ft37 Liquid Density 20-75 lb/ft38 Surface Tension 5-80 dyne/cm

2/28/2014 Distillation Column Tray Selection & Sizing – 1 - Separation Technologies

http://seperationtechnology.com/distillation-column-tray-selection-1/ 20/30

9 Liquid Viscosity 0.05-2.0 cP

10 Tray Spacing 14-36 in

11 Hole Diameter 1/8-1 in12 Fractional Hole Area 0.06-0.2013 Weir Height 0-3 in

Steps to calculate % Flooding using Kister and Haas correlation:

i. Calculate Weir Load (QL):

Liquid Load describes the flux of liquid across the tray.

ii. Clear Liquid height at the transition from the froth to spray ((hct)

2/28/2014 Distillation Column Tray Selection & Sizing – 1 - Separation Technologies

http://seperationtechnology.com/distillation-column-tray-selection-1/ 21/30

2. Jet Flood: Fair’s correlation

The Fair correlation has been standard of the industry for entrainment flood prediction. Fair’s correlation tends to be conservative, especially at highpressure and liquid rate.

This correlation possess following restriction:

2/28/2014 Distillation Column Tray Selection & Sizing – 1 - Separation Technologies

http://seperationtechnology.com/distillation-column-tray-selection-1/ 22/30

Sr.NoFactors Applicability

1Flooding Mechanism Entrainment (Jet) flood only

2Tray Type Sieve Tray, Valve and Bubble-cap Tray

3Hole size Hole£ ½ in (sieve tray)Weir height < 15% Tray Spacing

Steps to calculate % Flood using Fair’s correlation:

i. Calculate flow parameter

2/28/2014 Distillation Column Tray Selection & Sizing – 1 - Separation Technologies

http://seperationtechnology.com/distillation-column-tray-selection-1/ 23/30

3. Down-comer choke-Koch correlation:

This is the more conservative correlation for checking Down-comer Design. Steps to calculate % Load Utilization using Kister and Haas correlation:

2/28/2014 Distillation Column Tray Selection & Sizing – 1 - Separation Technologies

http://seperationtechnology.com/distillation-column-tray-selection-1/ 24/30

4. Hydraulic checks

Hydraulic check involves checking following parameters:

- Flow Regime

- Entrainment

- Downcomer residence time

- Pressure Drop

- Downcomer backup

ii.Determination of Flow Regime

Froth Regime

This is the most commonly encountered flow regime in operating columns. The froth formed under this regime is described as one where the size andshape of bubbles is non-uniform and with rather large size distribution, as well as travelling at varying velocities. The liquid surface is either wavy or it

2/28/2014 Distillation Column Tray Selection & Sizing – 1 - Separation Technologies

http://seperationtechnology.com/distillation-column-tray-selection-1/ 25/30

presents oscillations. This is a liquid continuous flow regime.

Spray Regime

This regimes occurs at relatively high vapour velocities (i.e. large vapour flow rates) and low liquid loads, characteristics which are typical of vacuumsystems. The vapour velocity is so large, that the liquid phase is completely disrupted and is no longer a continuous phase on top of the tray; liquid is adispersed phase present only in the form of drops, and therefore the continuous phase is the vapour.

Emulsion Regime

This flow regime is typically encountered in high-pressure systems and relatively high liquid loads. The shearing action of the high velocity liquid “tearsoff” the vapour bubbles leaving the orifices on the tray. Most of the gas is emulsified in small bubbles within the liquid, with the mixture behaving as a

uniform two-phase fluid, obeying the Francis weir formula. This is a liquid continuous flow regime.

The determination of regime on tray given below is only for information and has no use in sizing.

ii. Froth-Emulsion Transition Check

This correlation is applicable for Sieve trays only.

The value of actual flow parameter is calculated as below:

2/28/2014 Distillation Column Tray Selection & Sizing – 1 - Separation Technologies

http://seperationtechnology.com/distillation-column-tray-selection-1/ 26/30

If the value of actual flow parameter exceeds 0.0208 then the regime of operation is emulsion.

iii. Froth-Spray Transition Check:

Porter and Jenkins correlation for the froth to spray transition.

Where,

Lw – weir length in inches, AB – Active area ft2

p – pitch in inches

hc – clear liquid height, inches

5. Entrainment:

2/28/2014 Distillation Column Tray Selection & Sizing – 1 - Separation Technologies

http://seperationtechnology.com/distillation-column-tray-selection-1/ 27/30

If entrainment is excessive, column diameter or tray spacing are usually increased. As recommended value, the entrainment from the tray should notexceed about 0.10 lb liquid entrained per pound of liquid flow.

Methods to determine Entrainment:

Fair’s entrainment correlation

This method holds good for froth and emulsion regime. However it is less accurate for spray regime. For a trays operating at a high liquid to vapourratio, 0.1 lb of liquid entrained per pound of liquid is an excessive quantity of entrained liquid.

2/28/2014 Distillation Column Tray Selection & Sizing – 1 - Separation Technologies

http://seperationtechnology.com/distillation-column-tray-selection-1/ 28/30

Kister and Haas Correlation

This method is used for Spray Regime; Es is entrainment lb of liquid / lb of vapour.

2/28/2014 Distillation Column Tray Selection & Sizing – 1 - Separation Technologies

http://seperationtechnology.com/distillation-column-tray-selection-1/ 29/30

May 7th, 2012 in Design Distillation SystemCategories

Adsorption

Crystallization ProcessDesign Distillation SystemDistillation TechnologyExperimental Setups

Membrane SeparationOperations of Distillation SystemOther Unit Operations

Process Simulation

2/28/2014 Distillation Column Tray Selection & Sizing – 1 - Separation Technologies

http://seperationtechnology.com/distillation-column-tray-selection-1/ 30/30

Vapor Liquid EquilibriaWinery – Edible Alcohol

Recent Posts

DISTILLATION COLUMNS (or TOWERS)SIMPLE CONTINUOUS DISTILLATION PROCESS

DISTILLATION COLUMN CONTROLFILTERS & STRAINERSLOW TEMPERATURE SEPARATION

Copyright © 2012-2014 SEPERATIONTECHNOLOGY.COM. All right reserved. XHTML 1.0 | CSS 3.0