PDVSA_2012_KGTOWER-97

CONFIDENTIAL 2012 Koch-Glitsch, LP. All rights reserved.

KG-TOWER

Hydraulic Design and Rating

Software


What is it?

It allows users to design and rate KG proprietary packings and conventional valve and sieve trays.

It will provide the estimated capacity and pressure drop of KG high performance trays.

It will estimate a tower diameter and provide some design details (downcomer widths, for example).

It gives an indication of the turndown expected.


What else?

The KG-TOWER software has a list of both sales and technical contacts.

It includes pictures of our packings, valves, and trays.

It uses the same models that we use in our internal version to design our equipment.

Built in unit conversions.

Relative efficiency given for our packings.

It can import up to 5 loadings from SimSci-Esscors PRO/II and Aspen Technologys simulators.


Design Information Hydraulic Loads

Vapor (flow to tray)

Mass flow rate [kg/h or lb/hr]

Density [kg/m3 or lb/ft3]

Viscosity [cP]

Liquid (flow from tray)

Mass flow rate [kg/h or lb/hr]

Density [kg/m3 or lb/ft3]

Viscosity [cP]

Surface tension [dyne/cm]


Design Information System Properties

Foaming tendency

Fouling

Application

Pressure and temperature


EXAMPLE PROBLEM - ACID GAS

ABSORBER


Current Operation

2000mm

20 trays on 600mm spacing

36,000 kg/h

18.2 mol% CO2 (451 kg-mol/h)

90 mol ppm CO2 (0.18 kg-mol/h)

260,000 kg/h

30 wt% MEA

279,800 kg/h

0.47 mol CO2/mol MEA


Revamp

Goal is to increase throughput by 35% Existing trays would be flooded

What is required to check packing capacity? Vapor rate

Vapor density

Liquid rate

Liquid density

Liquid viscosity

Liquid surface tension


Physical Properties

Absorber top V = 16,160 kg/h

v = 24.6 kg/m3

L = 260,000 kg/h

L = 991.1 kg/m3

L = 1.01 cP

L = 66.6 dyne/cm

Absorber bottom V = 36,000 kg/h

v = 23.8 kg/m3

L = 279,800 kg/h

L = 926.7 kg/m3

L = 0.83 cP

L = 61.5 dyne/cm


KG-TOWER Design Program


Loading Input Screen


Packing Design Screen Current Operation


Packing Design Screen Proposed Operation


Efficiency

How do we check the efficiency of our selected packing?

Highest accuracy achieved by using a rate based simulation program such as the RATEFRAC module in

PROII

Calculate transfer units and height of a transfer unit using experimental Kga data for this system

Estimate efficiency of proposed packing using efficiency data from existing trays


KG-TOWER

TRAY DESIGN


Liquid Flow

Downcomer

Active Area or

Bubbling Area

Outlet Weir

Inlet Area

Vapor Flow

Downcomer

Clearance

Flow Path Length

Tray Spacing

Crossflow Tray Terminology


Design Information Mechanical Information

Materials of construction

Tower manhole size

Existing tower attachments (revamp situation)

User Company Design Standards


Optimizing Features

Number of flow passes

Downcomer adapters (revamp)

Sloped / stepped downcomers (kick-back)

Sweptback weirs

Radius lip downcomers

Sumps

Anti-jump baffles

Weir blocks


Tray Design Rules of Thumb

Conventional Trays


Input Values

Tray Spacing

24 [610 mm] is the most common

Typically ranges from 12 to 30 [300 to 760 mm]

Number of Flow Paths vs. Tower Diameter

1 Pass > 2.5 [760 mm] (ring supported)

2 Pass > 5 [1500 mm]

3 Pass > 8 [2400 mm]

4 Pass > 10 [3000 mm]


Input Values

Downcomer Chord

4 [100 mm] or 1/12 tower diameter minimum

applies to both top and bottom

Kickback

3 [75 mm] typical for conventional trays or to provide top-to-bottom area ratios:

< 2:1 if vapor density < 1.0 lb/ft3 [16 kg/m3]

< 3:1 if vapor density < 1.0 - 3.0 lb/ft3 [16 - 48 kg/m3]

< 4:1 if vapor density > 3.0 lb/ft3 [48 kg/m3]

Center and Off-center Downcomer Width

6 [150 mm] minimum

Applies to both top and bottom unless boxed DC is used


Input Values

Off-center Downcomer Position

Typically located to provide equal flow path lengths

Sweptback weirs

Can lose active area

Sump Width

Same as top downcomer width

Sump Depth

as need to provide VUD of 1.0 ft/sec [0.3 m/s]

4 to 6 [100 to 150 mm] is typical

25% of tray spacing maximum


Input Values

Weir Height

Generally 1 to 3 [25 to 75 mm]

Default is 2 [50 mm]

Use less than 12% of tray spacing to avoid a loss of jet flood capacity

Downcomer Radius

1 [25 mm] is standard for conventional trays

Downcomer Clearance

typically weir height minus 0.5 [10 to 15 mm]

0.75 [20 mm] absolute minimum [1 or 25 mm preferred min]

1.5 [37 mm] minimum for refining applications


Calculated Values

Jet Flood 85% maximum (all trays)

Downcomer Choke Flood (all trays)

85% maximum for low and moderate pressure

65-80% for high pressure hydrocarbon fractionation

Downcomer Backup: Conventional trays

40% or 33% if DL- DV is < 30 lb/ft3 (of TS + HW)

clear liquid basis

Weir Loading

6 gpm/ft [4.5 m3/m/h] minimum

consider more passes above 120 gpm/ft [90 m3/m/h]

Crest Over Weir

0.25 [6 mm] minimum


Calculated Values

Downcomer Exit Velocity

Conventional: 1.6 ft/sec [0.49 m/s] maximum (clear)

Downcomer Head Loss

Conventional: 1.5 [38 mm] liquid maximum

not applicable if downcomer radius is used

Dry Tray Pressure Drop

15% of tray spacing is the design limit (all trays)

Flow Path Length

18 [460 mm] minimum without a special design

16 [400 mm] absolute minimum to have tray manways (special design required)

Consider using more passes above 120 [3.0 m]


Rule of Thumb

While not applicable to all systems, there is an old industry rule of thumb that states:

10% entrainment will result in a 10% loss of tray efficiency

20% weepage will result in a 10% loss of efficiency


Low Liquid Rate Tray Features

When the weir loading is very low, the momentum of the vapor can throw the entire liquid rate into the

downcomer (or to the tray above) and blow the tray

dry.

In the process, the downcomer can become unsealed, thus aggravating the process.

When the weir loading is less than 6 gpm/ft [4.5 m3/m/h], the weir height should be a minimum of 2 [50 mm] tall.

Use weir blocks (picketing).

PDVSA_2012_KGTOWER-97

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