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Tray Design How to use the Baretti® design software
Your Worldwide Partner
2015 Web Tray Design Software Rev 1 Page 2 19/02/16
Tray Design Basics
q Column Diameter Sizing
q If the tower diameter is unknown
q Diam (m)=( (V * (Dv/(Dl-Dv))^0.5 * 15 )/3.14)^0.5*2
q Where V= vapor load in m3 / sec q Dv = Vapor density in kg/m3
q Dl = Liquid density in kg/m3
2015 Web Tray Design Software Rev 1 Page 3 19/02/16
Use of BARETTI® Software
q Open Baretti Trays Hydraulic Calculation Software q Input general project data q Fluids input
q Enter all lines of Liquid and Vapor loads q Enter also
q The System Factor ( Foaming tendency) q The multipliers ( make a calculation at increased or decreased
loads from the design rate) q Each data has controlling limits. If the input exceed these
limits an alert is given, but if correct the data can be confirmed can
q Store each line of fluids input
2015 Web Tray Design Software Rev 1 Page 4 19/02/16
Use of BARETTI® Software q Geometry Input
q Open the windows of the geometry and enter all data for each group of identical trays
q For units selection, following are main points: q Valves : Type and number
Floating : The leg length (11.1 is std.) is the total length .The net rise is this number reduced by the tray thickness
Fix : The valve rise is net above the tray (Std. 11.1 Baretti SVG and 8 BV-0)
q Sieve trays : Hole size and number q DC Slope:
q 100% means straight DC and automatically all Dcs are sized based on the given Side DC area
q X% Mean that the Dcs are sloped and the % is the ratio between the bottom and the top areas
q 0% Means that the DC inputs will not be modified ( Specified geometry)
2015 Web Tray Design Software Rev 1 Page 5 19/02/16
Use of BARETTI® Software
q Geometry Input (continue)
q DC Clearance q Select a clearance that allows correct outlet velocities ( see later points)
q Swept back weirs q In case of swept back weirs input the needed total length of the side weir
q Picket fence q Input the % of the weir length to be blocked
q For 4 pass trays, you can select q AA= (1) if Active areas are equal q AA = (0) if Flow paths are equal
2015 Web Tray Design Software Rev 1 Page 6 19/02/16
BARETTI® Valves
q Floating Valves :
q Baretti BDH : standard valve q Baretti BV-1 : round valve
q Fix Valves:
q Baretti SVG : standard valve q Baretti BV-0 : high performance micro valve
2015 Web Tray Design Software Rev 1 Page 7 19/02/16
Downcomer Design
q Number of passes q Depending on the size of the column and the specific liquid load
one or more passes can be used q As rule of thumb the specific liquid load on the weir should not
exceed 1.5 m3/min/m. This value can be reduced by q Making a longer outlet weir q Increase the number of passes ( 1,2 and 4)
q The liquid inlet velocity into the top downcomer (Vin) area should be limited as follows:
q Dl/Dv >500 Vin< 0.17 q Dl/Dv >100 and Dv/Dl <500 Vin< 0.12 q Dl/Dv >10 and Dv/Dl <100 Vin< 0.1 q Dl/Dv <10 and Vin< 0.08
2015 Web Tray Design Software Rev 1 Page 8 19/02/16
Tray Spacing selection
q Tray spacing q The standard tray spacing are:
q 250-300 mm for column to be installed under roof
q 350-450 for superfractionators in order to reduce column height
q 610mm for traditional applications
q 760 – 900 mm for very large columns and very high liquid trays
q Effects of tray spacing selection
q The column capacity is function of the tray spacing. In fact the higher is the tray spacing the higher can be the vapor/liquid mix layer on the tray or the spray
q To obtain a short column a low tray spacing can be used. As a result the column becomes larger
q For foaming systems is suggested to use standard or higher tray spacing, since the stable layer of foam can touch the next tray and reduce the tray efficiency
2015 Web Tray Design Software Rev 1 Page 9 19/02/16
Downcomer Clearance
q DC clearance q The DC clearance has to be
calculated based on the liquid exiting velocity
q The limit velocity through the DC clearance is 0.45 - 0.50 m/sec. This to reduce the discharge pressure drop
q For mechanical reasons the DC clearance should be limited to 20 mm for towers up to 3 m diameter and 25 mm for bigger columns
q In case of low liquid rates the above limits can be still applied , but an inlet weir should be used to keep the seal
q Recessed sump q If the liquid load is very high
2015 Web Tray Design Software Rev 1 Page 10 19/02/16
Outlet Weir
q Outlet weir height q The standard weir height is 50
mm q For absorbers and all systems
where the contact time is basic use 65mm
q For low pressure systems use 30-40 mm weir. A low weir can effect the tray efficiency
q For low liquid trays: q Use Notched or picket fence
design q If liquid crest is lower than 5 mm
use a splash baffle positioned before the outlet weir (250mm High)
q Adjustable weirs q Unless differently specified use
adjustable outlet weir if the liquid crest at design is lower than
q 20 mm for columns < 3000 mm q 30 mm for columns > 3000 mm
q Swept Back weirs q SBW can be used in following
cases: q When a lower crest can help
reducing the tray pressure drop q To reduce the side dead areas
and improve the efficiency of the tray
2015 Web Tray Design Software Rev 1 Page 11 19/02/16
General Design Points
q Valve density q Baretti BDH max 130 / m2
q Baretti SVG max 130 / m2
q Baretti BV-0 max 300 / m2
q Sieve Max 14% open area
q Tray thickness (C.A. Included) q Baretti BDH 2 - 5 mm q Baretti SVG 2 - 5 mm q Baretti BV-0 2 - 3mm q Sieve 2 - 5 mm
q Bubble promotors q Consult Baretti if needed
q Dual weight valves q Use this feature to maximize the tray
turndown
q Flow path length q Minimum 400mm
q Baffles q Anti jump baffles, normally not
needed q Splash Baffle , as in previous page q Parallel Baffles: to used only when
tower is oversized.(Run parallel to flow , 300 mm high)
q Split Flow baffles. To be used to increase the DC capacity. Consult Baretti
q Seal pan q To be used always to seal DC of
lower tray. Depth =TS+150mm
Recommended