Week 8 - Simulating Cyclone separator with Discrete Phase Modelling
SIMULATION OF CYCLONE SEPARATOR
Aim:- To perform analysis on cyclone separator and calculate the separation efficiency and pressure drop.
Objective:-
- To write a few words about any four empirical models used to calculate the cyclone separator efficiency.
- To perform an analysis on a given cyclone separator model by varying the particle diameter from 1 μm to 5 μm and calculate the separation efficiency in each case. Discuss the results. [Use both the velocity's as 3m/sec.]
- To perform an analysis on a given cyclone separator model by varying the particle velocity from 1 m/sec to 5 m/sec and calculate the separation efficiency and pressure drop in each case. Discuss the results. [Use particle diameter size as 5 μm for all cases & keep flow velocity same as particle velocity].
THEORY
Cyclone Separator
Cyclone separators are separation devices 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 pre-cleaners since they generally remove larger pieces of particulate matter. This prevents finer filtration methods from having to deal with large, more abrasive particles later on.
The size of the cyclone depends largely on how much flue gas must be filtered, thus larger operations tend to need larger cyclones. For example, several different models of one cyclone type can exist, and the sizes can range from a relatively small 1.2-1.5 m tall (about 4-5 feet) to around 9 meters (30 feet)—which is about as tall as a three-story building.
Working of Cyclone Separator
cyclone separators work much like a centrifuge, but with a continuous feed of dirty air. In a cyclone separator, dirty flue gas is fed into a chamber. The inside of the chamber creates a spiral vortex, similar to a tornado. The lighter components of this gas have less inertia, so it is easier for them to be influenced by the vortex and travel up it. Contrarily, larger components of particulate matter have more inertia and are not as easily influenced by the vortex.
Since these larger particles have difficulty following the high-speed spiral motion of the gas and the vortex, the particles hit the inside walls of the container and drop down into a collection hopper. These chambers are shaped like an upside-down cone to promote the collection of these particles at the bottom of the container. The cleaned flue gas escapes out the top of the chamber. Most cyclones are built to control and remove particulate matter that is larger than 10 micrometers in diameter. However, there do exist high-efficiency cyclones that are designed to be effective on particles as small as 2.5 micrometers. As well, these separators are not effective on extremely large particulate matter. For particulates around 200 micrometers in size, gravity settling chambers or momentum separators are a better option.
To write a few words about any four empirical models used to calculate the cyclone separator efficiency.
1. Iozia and Leith model
This model assumes that the particle carried by the vortex is controlled by centrifugal force and flow resistance. The collection efficiency is calculated from the below formula,
DPC is the 50% cut size given by the barth model
2. Li and Wong model
This model includes particle re-entrainment and turbulent diffusion at the cyclone wall. This model was developed based on the assumption that the radial particle velocity and radial concentration profile are not constant for uncollected particles within cyclones. Boundary conditions with turbulent diffusion coefficient and particle re-entrainment on the cyclone wall are given below,
The concentration distribution in a cyclone is given,
The collection efficiency for any given particle size is,
3. Kocht and Licht model
This model describes the particle motion in the entry and collection regions with assumptions that the tangential velocity of the particle is equal to the tangential velocity of the gas flow and the tangential velocity and radius of the cyclone are related.
The collection efficiency is given by,
4. Lapple model
This model was developed based on the force balance without considering flow resistance. It was assumed that the particle entering the cyclone is evenly distributed across the inlet. Lappel developed an empirical relationship to calculate 50% cut diameter and it is given by,
The number of revolutions is given by,
The collection efficiency of any given size of the particle is given by,
SIMULATION AND SOLUTION:
In this Project we have 2 cases where:
CASE 1:To perform an analysis on a given cyclone separator model by varying the particle diameter from 1 μm to 5 μm and calculate the separation efficiency in each case. Discuss the results. [Use both the velocity's as 3m/sec.]
CASE 2: To perform an analysis on a given cyclone separator model by varying the particle velocity from 1 m/sec to 5 m/sec and calculate the separation efficiency and pressure drop in each case. Discuss the results. [Use particle diameter size as 5 μm for all cases & keep flow velocity same as particle velocity]
NOTE: In both cases, the geometry and the mesh remain the same.
So in case 1, we have one given velocity with 5 varying particle diameters.
And in case 2, we have one particle diameter and 5 varying velocities.
STEP 1: GEOMETRY:
For the given geometry we have to extract the volume using the edge option.
Given geometry
Extracted Geometry:
STEP 2: MESHING
In this project, we use ceatran body method with an element size of 0.0055m and a max size of 0.01m
Naming the sections
STEP 3: SETUP
CASE 1:
In this, we keep the velocity constant with 5 varying particle diameters.
Part 1:
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SETUP |
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Gravity |
-9.81 in the Y direction | |
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Solver Type |
Pressure-Based |
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Velocity Formulation |
Absolute |
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Time |
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Models |
Viscous model: K-epsilon, RNG, Swirl Dominated flow. Energy model: OFF Discrete Phase model: on* Particle dia: 1μm Velocity magnitude: 3 m/s |
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Material |
Fluid type: Air Solid-type: Aluminium |
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Cell zones |
Fluid type: Air Solid: Al |
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Boundaries |
Inlet velocity : 3m/s DPM: reflect Wall:- DPM: Reflect Outlet(Top):-DPM: Escape Outlet(Bottom/dustbin) -DPM: Trap |
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Reference values |
Standard |
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Initialization |
Standard Starting from inlet |
* Note*: Discrete Phase Model: Interaction with continuous phase, update DPM sources every flow iteration, Max no of steps -> Create Injections Through surfaces by Inlet
Running up to 1000 iterations.
RESIDUAL PLOT:
ANTHRACITE PARTICLE TIME:
Separation Efficiency = (Trapped/Tracked)*100= 38.359%
PRESSURE COUNTER:
Part 2:
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SETUP |
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Gravity |
-9.81 in the Y direction | |
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Solver Type |
Pressure-Based |
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Velocity Formulation |
Absolute |
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Time |
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Models |
Viscous model: K-epsilon, RNG, Swirl Dominated flow. Energy model: OFF Discrete Phase model: on* Particle dia: 2μm Velocity magnitude: 3 m/s |
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Material |
Fluid type: Air Solid-type: Aluminium |
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Cell zones |
Fluid type: Air Solid: Al |
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Boundaries |
Inlet velocity : 3m/s DPM: reflect Wall:- DPM: Reflect Outlet(Top):-DPM: Escape Outlet(Bottom/dustbin) -DPM: Trap |
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|
Reference values |
Standard |
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|
Initialization |
Standard Starting from inlet |
* Note*: Discrete Phase Model: Interaction with continuous phase, update DPM sources every flow iteration, Max no of steps -> Create Injections Through surfaces by Inlet
RESIDUAL PLOT:
ANTHRACITE PARTICLE TIME:
Separation Efficiency = (147/378)*100 = 38.888%
PRESSURE COUNTER:
Part 3:
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SETUP |
||
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Gravity |
-9.81 in the Y direction | |
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Solver Type |
Pressure-Based |
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Velocity Formulation |
Absolute |
|
|
Time |
|
|
|
Models |
Viscous model: K-epsilon, RNG, Swirl Dominated flow. Energy model: OFF Discrete Phase model: on* Particle dia: 3μm Velocity magnitude: 3 m/s |
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Material |
Fluid type: Air Solid-type: Aluminium |
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Cell zones |
Fluid type: Air Solid: Al |
|
|
Boundaries |
Inlet velocity : 3m/s DPM: reflect Wall:- DPM: Reflect Outlet(Top):-DPM: Escape Outlet(Bottom/dustbin) -DPM: Trap |
|
|
Reference values |
Standard |
|
|
Initialization |
Standard Starting from inlet |
* Note*: Discrete Phase Model: Interaction with continuous phase, update DPM sources every flow iteration, Max no of steps -> Create Injections Through surfaces by Inlet
RESIDUAL PLOT:
ANTHRACITE PARTICLE TIME:
Separation Efficiency = (168/378)*100 = 44.44%
PRESSURE COUNTER:
Part 4:
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SETUP |
||
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Gravity |
-9.81 in the Y direction | |
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Solver Type |
Pressure-Based |
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Velocity Formulation |
Absolute |
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|
Time |
|
|
|
Models |
Viscous model: K-epsilon, RNG, Swirl Dominated flow. Energy model: OFF Discrete Phase model: on* Particle dia: 4μm Velocity magnitude: 3 m/s |
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Material |
Fluid type: Air Solid-type: Aluminium |
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Cell zones |
Fluid type: Air Solid: Al |
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|
Boundaries |
Inlet velocity : 3m/s DPM: reflect Wall:- DPM: Reflect Outlet(Top):-DPM: Escape Outlet(Bottom/dustbin) -DPM: Trap |
|
|
Reference values |
Standard |
|
|
Initialization |
Standard Starting from inlet |
* Note*: Discrete Phase Model: Interaction with continuous phase, update DPM sources every flow iteration, Max no of steps -> Create Injections Through surfaces by Inlet
RESIDUAL PLOT:
ANTHRACITE PARTICLE TIME:
Separation Efficiency = (171/378)*100 = 45.23%
PRESSURE COUNTER:
Part 5:
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SETUP |
||
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Gravity |
-9.81 in the Y direction | |
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Solver Type |
Pressure-Based |
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|
Velocity Formulation |
Absolute |
|
|
Time |
|
|
|
Models |
Viscous model: K-epsilon, RNG, Swirl Dominated flow. Energy model: OFF Discrete Phase model: on* Particle dia: 5μm Velocity magnitude: 3 m/s |
|
|
Material |
Fluid type: Air Solid-type: Aluminium |
|
|
Cell zones |
Fluid type: Air Solid: Al |
|
|
Boundaries |
Inlet velocity : 3m/s DPM: reflect Wall:- DPM: Reflect Outlet(Top):-DPM: Escape Outlet(Bottom/dustbin) -DPM: Trap |
|
|
Reference values |
Standard |
|
|
Initialization |
Standard Starting from inlet |
* Note*: Discrete Phase Model: Interaction with continuous phase, update DPM sources every flow iteration, Max no of steps -> Create Injections Through surfaces by Inlet
RESIDUAL PLOT:
ANTHRACITE PARTICLE TIME:
Separation Efficiency = (201/378)*100 = 53.17%
PRESSURE COUNTER:
| Case 1 | Size of Particles (m) | The velocity of particles (m/s | No of the particles tracked | No of the particles escaped | No of the particle trapped | No of the particles incomplete | separation efficiency (%) | Mass flow on inlet (kgs^1) |
| 1 | 1e5 | 3 | 378 | 177 | 145 | 56 | 38.359 | 0.0183815 |
| 2 | 2e5 | 3 | 378 | 148 | 147 | 83 | 38.888 | 0.0183815 |
| 3 | 3e5 | 3 | 378 | 129 | 168 | 81 | 44.44 | 0.0183815 |
| 4 | 4e5 | 3 | 378 | 118 | 171 | 89 | 45.23 | 0.0183815 |
| 5 | 5e5 | 3 | 378 | 105 | 201 | 72 | 53.17 | 0.0183815 |
CASE 2:
In this, we keep the particle diameters constant with 5 varying velocities.
Part 1:
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SETUP |
||
|
Gravity |
-9.81 in the Y direction | |
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Solver Type |
Pressure-Based |
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|
Velocity Formulation |
Absolute |
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|
Time |
|
|
|
Models |
Viscous model: K-epsilon, RNG, Swirl Dominated flow. Energy model: OFF Discrete Phase model: on* Particle dia: 5μm Velocity magnitude: 1 m/s |
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Material |
Fluid type: Air Solid-type: Aluminium |
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Cell zones |
Fluid type: Air Solid: Al |
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Boundaries |
Inlet velocity : 1 m/s DPM: reflect Wall:- DPM: Reflect Outlet(Top):-DPM: Escape Outlet(Bottom/dustbin) -DPM: Trap |
|
|
Reference values |
Standard |
|
|
Initialization |
Standard Starting from inlet |
* Note*: Discrete Phase Model: Interaction with continuous phase, update DPM sources every flow iteration, Max no of steps -> Create Injections Through surfaces by Inlet
Running up to 1000 iterations.
RESIDUAL PLOT:
ANTHRACITE PARTICLE TIME:
Separation Efficiency = (8/378)*100 = 2.11%
PRESSURE COUNTER:
Part 2:
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SETUP |
||
|
Gravity |
-9.81 in the Y direction | |
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Solver Type |
Pressure-Based |
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|
Velocity Formulation |
Absolute |
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|
Time |
|
|
|
Models |
Viscous model: K-epsilon, RNG, Swirl Dominated flow. Energy model: OFF Discrete Phase model: on* Particle dia: 5μm Velocity magnitude: 2 m/s |
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Material |
Fluid type: Air Solid-type: Aluminium |
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Cell zones |
Fluid type: Air Solid: Al |
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Boundaries |
Inlet velocity : 2 m/s DPM: reflect Wall:- DPM: Reflect Outlet(Top):-DPM: Escape Outlet(Bottom/dustbin) -DPM: Trap |
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|
Reference values |
Standard |
|
|
Initialization |
Standard Starting from inlet |
* Note*: Discrete Phase Model: Interaction with continuous phase, update DPM sources every flow iteration, Max no of steps -> Create Injections Through surfaces by Inlet
RESIDUAL PLOT:
ANTHRACITE PARTICLE TIME:
Separation Efficiency = (9/378)*100 = 2.380
PRESSURE COUNTER:
Part 3:
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SETUP |
||
|
Gravity |
-9.81 in the Y direction | |
|
Solver Type |
Pressure-Based |
|
|
Velocity Formulation |
Absolute |
|
|
Time |
|
|
|
Models |
Viscous model: K-epsilon, RNG, Swirl Dominated flow. Energy model: OFF Discrete Phase model: on* Particle dia: 5μm Velocity magnitude: 3 m/s |
|
|
Material |
Fluid type: Air Solid-type: Aluminium |
|
|
Cell zones |
Fluid type: Air Solid: Al |
|
|
Boundaries |
Inlet velocity : 3m/s DPM: reflect Wall:- DPM: Reflect Outlet(Top):-DPM: Escape Outlet(Bottom/dustbin) -DPM: Trap |
|
|
Reference values |
Standard |
|
|
Initialization |
Standard Starting from inlet |
* Note*: Discrete Phase Model: Interaction with continuous phase, update DPM sources every flow iteration, Max no of steps -> Create Injections Through surfaces by Inlet
This is already discussed as CASE 1 Part 5.
Part 4:
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SETUP |
||
|
Gravity |
-9.81 in the Y direction | |
|
Solver Type |
Pressure-Based |
|
|
Velocity Formulation |
Absolute |
|
|
Time |
|
|
|
Models |
Viscous model: K-epsilon, RNG, Swirl Dominated flow. Energy model: OFF Discrete Phase model: on* Particle dia: 5μm Velocity magnitude: 4 m/s |
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|
Material |
Fluid type: Air Solid-type: Aluminium |
|
|
Cell zones |
Fluid type: Air Solid: Al |
|
|
Boundaries |
Inlet velocity : 4m/s DPM: reflect Wall:- DPM: Reflect Outlet(Top):-DPM: Escape Outlet(Bottom/dustbin) -DPM: Trap |
|
|
Reference values |
Standard |
|
|
Initialization |
Standard Starting from inlet |
* Note*: Discrete Phase Model: Interaction with continuous phase, update DPM sources every flow iteration, Max no of steps -> Create Injections Through surfaces by Inlet
RESIDUAL PLOT:
ANTHRACITE PARTICLE TIME:
Separation Efficiency = (281/378)*100= 74.33
PRESSURE COUNTER:
Part 5:
|
SETUP |
||
|
Gravity |
-9.81 in the Y direction | |
|
Solver Type |
Pressure-Based |
|
|
Velocity Formulation |
Absolute |
|
|
Time |
|
|
|
Models |
Viscous model: K-epsilon, RNG, Swirl Dominated flow. Energy model: OFF Discrete Phase model: on* Particle dia: 5μm Velocity magnitude: 5 m/s |
|
|
Material |
Fluid type: Air Solid-type: Aluminium |
|
|
Cell zones |
Fluid type: Air Solid: Al |
|
|
Boundaries |
Inlet velocity : 5m/s DPM: reflect Wall:- DPM: Reflect Outlet(Top):-DPM: Escape Outlet(Bottom/dustbin) -DPM: Trap |
|
|
Reference values |
Standard |
|
|
Initialization |
Standard Starting from inlet |
* Note*: Discrete Phase Model: Interaction with continuous phase, update DPM sources every flow iteration, Max no of steps -> Create Injections Through surfaces by Inlet
RESIDUAL PLOT:
ANTHRACITE PARTICLE TIME:
Separation Efficiency = (274/378)*100 = 72.48
PRESSURE COUNTER:
| Case 1 | Size of Particles (m) | The velocity of particles (m/s | No of the particles tracked | No of the particles escaped | No of the particle trapped | No of the particles incomplete | separation efficiency (%) | Mass flow of inlet(kgs^1) |
| 1 | 5e5 | 1 | 378 | 104 | 8 | 266 | 2.11 | 0.0061217 |
| 2 | 5e5 | 2 | 378 | 99 | 9 | 270 | 2.30 | 0.0122543 |
| 3 | 5e5 | 3 | 378 | 201 | 105 | 72 | 53.17 | 0.0183815 |
| 4 | 5e5 | 4 | 378 | 94 | 281 | 3 | 74.33 | 0.0024508 |
| 5 | 5e5 | 5 | 378 | 102 | 274 | 2 | 72.48 | 0.0306359 |
CONCLUSION:
- From the observations of Part_1 & Part_2 cases, we can conclude that the Separation efficiency of the Cyclone Separator depends on both Diameter of the Particles and also on the Velocity of the Particles.
- Also, we can conclude that in cases of Part_2, there are more efficient results. So the Velocity is a more effective variable for higher efficiency.
- The efficiency of a Cyclone Separator is directly proportional to the Pressure Drop.
- Higher efficiency Cyclones has higher Pressure Drops.
- Higher the Velocity, the higher the Pressure Drop, and the highest the Efficiency.
- Also, with an increase in Diameter and Velocity, Particle Resident time decreases.
- Therefore, when less resident time is taken by the Particles, higher can be the efficiency of the Cyclone Separator.