Numerical simulation of demister equipment for application in gravitational separators
MIST-ELIMINATOR = DEMISTER
- Internal devices designed to collect liquid droplets from gaseous streams:
- Used in separators, columns, etc;
- Avoids losses of liquid material;
- Protects the gas stream equipment from hydraulic damage.
- Usually designed using manufacturers tables/formulas:
- These tables/formulas work with averaged and ideal conditions;
- Average velocities, droplets diameters, gas flow homogeneously distributed, etc.
- Vane Pack and wire-mesh models:
- Different ranges of liquid loads, velocities and (mainly) droplets diameter.
VANE-PACK MIST ELIMINATOR
- Vanes forming tortuous "paths"
- Particles collide against walls (inertia)
- Good efficiency for large droplets
- Can be used in series with the wire-mesh model
WIRE-MESH MIST ELIMINATOR
- Wires forming a meshwith high void fraction and high surface (contact) area
- Small particles collide against the wires and are collected
- Good efficiencies for small droplets
Create a methodology to simulate such equipment:
- Preview the actual efficiency of the device;
- Acquire detailed information on the gas/liquid distribution over the demister surface;
- Compare with manufacturers data.
Simulate the equipment for a given separator geometry:
- Horizontal and vertical separators;
- Horizontal and vertical demister configurations.
Wire-mesh demister only!
Demister modeled as a thin surface using the "porous jump" condition:
- Behavior similar to a porous media;
- Good approximation for thin porous equipment.
Efficiency calculated locally (per control volume) via UDF!
- Using local conditions (gas velocity, droplet diameter, etc.);
- "Raffles" the particles collected based on local calculated efficiency!
- Stores on demister volumes information of number and mass of droplets collected and the averaged collected diameter.
Petrobras - Brazil