Cyclone Separator Challenge
AIM: To perform analysis on cyclone separator and calculate the separation efficiency and pressure drop.
INTRODUCTION: Cyclone separators or simply cyclones are separation devices (dry scrubbers) that use the principle of inertia to remove particulate matter from flue gases. Cyclone separators is one of many air pollution control devices known as precleaners since they generally remove larger pieces of particulate matter.
Cyclone separator empirical models:
IOZIA AND LEITH MODEL:
lozia and Leith (1990) logistic model is a modified version of Barth (1956) model which is developed based on force balance. The model assumes that a particle carried by the vortex endures the influence of two forces: a centrifugal force, Z, and a flow resistance,
The addition made by lozia and Leith on the original Barth (1956) model are the core length zc and slope parameter f3 expression which is derived based on the statistical analysis of experimental data of cyclone with D = 0.25 m.
LI AND WANG MODEL:
The Li and Wang (1989) model includes particle bounce or re-entrainment and turbulent diffusion at the cyclone wall. A two-dimensional analytical expression of particle distribution in the cyclone is obtained. Li and Wang model was developed based on the following assumptions:
The radial particle velocity and the radial concentration profile are not constant, for uncollected particles within the cyclones. Boundary conditions with the consideration of turbulent diffusion coefficient and particle bounce re-entrainment on the cyclone wall.
KOCH AND LICHT MODEL:
Koch and Licht (1977) collection theory recognized the inherently turbulent nature of cyclones and the distribution of gas residence times within the cyclone. Koch and Licht describe particle motion in the entry and collection regions with the additional following assumptions:
The tangential velocity of a particle is equal to the tangential velocity of the gas flow, i.e. there is no slip in the tangential direction between the particle and the gas. The tangential velocity is related to the radius of cyclone by: uRn = constant.
LAPPLE MODEL:
Lapple (1951) model was developed based on force balance without considering the flow resistance. Lapple assumed that a particle entering the cyclone is evenly distributed across the inlet opening. The particle that travels from inlet half width to the wall in the cyclone is collected with 50% efficiency. The semi empirical relationship developed by Lapple (1951) to calculate a 50% cut diameter.
PROCEDURE:
Geometry setup:
- The model is imported to spaceclaim and the fluid volume is extracted from it.
Meshing:
- Then the model is meshed with appropriate mesh size,here 0.001m is taken.
- The cyclone separator model is given the names inlet,outlet_1 and outlet_2 by selecting the respective parts.
Solving:
- Now the model is taken to fluent for solving.
- Gravity value Y=-9.81 is given
- K-epsilon model with RNG and swirl dominated flow is chosen.
- Since this simulation is related to discrete phase model hence the following parameters are set.
- Boundary conditions - Inlet velocity is given for the inlet and DPM conditions are also given as follows:
Inlet and wall:- Reflect
Outlet(Top):- Escape
Outlet(Bottom/dustbin) - Trap
- Since the inlet and outlet are being mentioned hence standard initialization is done and the simulation is ran for 600 iterations.
Separation Efficiency = Ratio of trapped particles to total no.of particles tracked
Pressure drop = Total inlet pressure - Total outlet pressure
CASE-I: Separation efficiency by vaying the particle diameter from 1micrometer to 5 micrometer.
CASE-II: Pressure drop and separation efficiency by vaying the particle velocity from 1 m/s to 5 m/s.
Post Processing:
Conclusion: From the above table we can infer that
- increase in diameter increases the separation efficiency.
- increase in velocity increases the pressure drop.