OPTIMIZATION OF THE DESIGN

OF A SKIMMER TANK

Paula Lucía Ismirlian

Astra Evangelista S.A.

AESA

Four Business Units:

• Engineering

• Manufacturing

• Construction

• Services

Presence in Argentina, Peru, Bolivia, Brazil, Uruguay.

Problem Description

• Location: Santa Cruz, Argentina.

• Secondary oil recovery by water injection

Water Treatment Plant for re-injection of water in oil well

Skimmer Tank:

– Flotation of oil droplets (discrete phase)

– Separation from water (continuous phase)

Goal: Achieve an acceptable residence time and

flow pattern

Problem Description (cont.)

Skimmer Tank: Simple / Low cost / Low maintenance

DESIGN OPTIMIZATION

Configuration of internals and inlet and outlet ducts

Inlet Outlet

Overflow Baffles

Methodology

• Initial geometry (Case 1)

• Alternative designs (Cases 2 - 3)

Comparation of these cases

Premise: Máx. ppm of oil in water outlet

Methodology

CFD:

• Flow patterns inside the tank

• Velocities

• Oil concentration in water outlet

• Oil particles and sand particles path

• Quantity of oil and sand escaping from each outlet

• Recirculation zones

Analysys

1. Geometry (basic case) ANSYS Space Claim

Analysys

2. Meshing ANSYS Meshing

• Prisms and

Tetrahedrons

Analysys

3. Set up ANSYS CFX

Two simulations:

• Resolution of tank fluid dynamics only with continuous

phase

– Single phase regime

– Turbulence model: Standard k-epsilon

– Stationary regime

– Incompressible fluid

– Isothermal

Analysys

• Resolution of the particles path (oil + sand) in the

continuous phase

– Transient regime

– Multiphase regime: Euler-Lagrange Model (particles and

water)

– One-way coupling

– Schiller-Neumann drag model

– No colision between particles

– No coalescence

– Indeformable particles

Analysys

Material properties (constant) :

– Water: temperature, density, viscosity.

– Oil and sand particles:

• 3 diameters (“Size 1” < “Size 2” < “Size 3”)

• Inlet concentrations

• Densities

• Oil viscosity.

Analysys

Boundary conditions:

– Inlet mass flow

– Outlet pressure

– Superior wall: overflow condition

• Continuous phase free slip

• Discrete phase absoption coefficient = 1

– Lateral walls/baffles: no roughness

• Continuous phase no slip

• Discrete phase perpendicular and parallel bounce

coefficients

Results and conclusions

Case 1: Basic geommetry

Water velocities:

INLET

OUTLET

Results and conclusions

Velocity in a plane:

INLET

OUTLET

Results and conclusions

Velocities in other planes:

Results and conclusions

Oil Particles:

size1 BLUE

size2 RED

size3 GREEN

Results and conclusions

Case 2: Jacketed in/out

Water velocity fields:

INLET

OUTLET

Results and conclusions

Water Streamlines

(velocities):

Size 1 Size 2 Size 3

Results and conclusions

Inlet

Outlet

Overflow

Inside

Oil concentrations:

Results and conclusions

Case 3: Vertical baffles

Inlets

Outlet

Vertical

baffles Horizontal

baffles

Results and conclusions

Water streamlines

Size 1 residence time:

Results and conclusions

Size 3 residence time:

Results and conclusions

Size 1 Size 2 Size 3

Inlet

Outlet

Overflow

Inside

Máx. ppm

Results and conclusions

Thank you!

Questions?