Week 8 - Simulating Cyclone separator with Discrete Phase Modelling
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]
Boundary Conditions:-
Inlet and wall:- Reflect
Outlet(Top):- Escape
Outlet(Bottom/dustbin) - Trap
Cyclone seperators:
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 device 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. In addition, several cyclone separators can operate in parallel, and this system is known as a multi-cyclone.
It is important to note that cyclones can vary drastically in their size. The size of the cyclone depends largely on how much fluid gas must be filtered, thus larger operations tend to need larger cyclones. For example, several different models of one cyclon type can exist, and the sizes can range from a relatively small 1.2-1.5 meters tall (about 4-5 feet) to around 9 meters (30 feet)— which is about as tall as a three-story building!.
Cyclone separators work much like a centrifuge, but with a continuous feed of dirty air. In a cyclone separator, dirty flue gas is feed into a chamber. The inside of the chamber creates a spiral vortex, similar to a tornado. This spiral formation and the separation 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.
Out of all of the particulate-control devices, cyclone separators are among the least expensive. They are often used as a pre-treatment before the flue gas enters more effective pollution control devices. Therefore, cyclone separators can be seen as "rough separators" before the flue gas reaches the fine filtration stages.
Effectiveness:
Cyclone separators are generally able to remove somewhere between 50-99% of all particulate matter in the flue gas. How well the cyclone separators are actually able to remove this matter depends largely on particle size. If there is a large amount of lighter particulate matter, less of these particles are able to be separated out. Because of this, cyclone separators work best on fluid gases that contain large amounts of big particulate matter.
There are several advantages and disadvantages to using cyclone separators. First, cyclone separators are beneficial because they are not expensive to install or maintain, and they have no moving parts. This keeps maintenance and operating costs low. Second, the removed particulate matter is collected when dry, which makes it easier to dispose of. Finally, these units take place. Although effective, there are also disadvantages to using cyclone separators. Mainly because the standard models are no able to collect particulate matter that is smaller than 10 micrometers effectively and the machines are unable to handle sticky or tacky materials well.
Separation efficiency is the ratio of trapped particles to the total number of particles tracked.
Pressure drop is defined as the difference in total pressure between two points of the fluid carrying network.
pressure drop = Total inlet pressure - total outlet pressure(top).
Geometry:
Meshing:
Elements size- 10mm.
Nodes- 37953.
Elements-156969.
Named selections are given below:
Inlet
Outlet 1
Outlet 2
Setup:
After meshing select inlets and outlets using face selector and named them using the named selection tool as shown in the above figure.
Solver steps enable gravity in '-ve' Y direction and put the value of 9.81m/s^2
Select steady-state pressure-based solver
Then select a turbulent model
Enable RNG and swirl dominated options also
Then enable discrete phase modeling to track particle flow
Then create injection with anthracite material and select injection type surface
Then choose an inlet face from reference surfaces
As per conditions and case, change the velocity of anthracites and diameter of anthracite particles.
Influent solver apply the following boundary conditions
Inlet and wall:- Reflect
Outlet(Top):- Escape
Outlet(Bottom/dustbin) - Trap
Here,
1. Reflect defines particles that should rebound (reflect) from a given surface.
2. Trap defines trajectory calculation to be stopped after touching the surface.
3. Escape defines calculation stops as soon as particles escape from the boundary.
Then vary the inlet velocity from 1m/s to 5m/s as per required cases.
And then use standard initialization where take reference values from the inlet
case 1: for 1 Micrometer: with velocity 3m/sec
Boundary Conditions:-
Inlet and wall:- Reflect
Outlet(Top):- Escape
Outlet(Bottom/dustbin) - Trap
Results:
Residuals:
case 1.2: for 2 Micrometer:
Results:
Residuals
case 1.3: for 3 Micrometer
Results:
residuals plots
case 1.4: for 4 Micrometer
Results:
residuals plots
case 1.5: for 5 Micrometer
Results:
residuals plots
Case 2: for velocity 1m/sec:5 micrometer
Results:
residuals plots
Case 2: for velocity 2 m/sec for 5 micrometer
Results:
case 2.3: for velocity 3 m/sec for 5 micrometer
Results:
residuals plots
case 2.3: for velocity 4 m/sec for 5 micrometer
Results:
residuals plots
case 2.3: for velocity 4 m/sec for 5 micrometer
Results:
residuals plots
Conclusion:
1.Separation Efficiency depends on both the diameter and velocity of particles.
2.Increase in diameter and velocity increases separation efficiency.
3.Velocity has a greater impact as compared to the diameter of particles.
4.Pressure drop is dependant on velocity. for constant velocity with varying diameter sizes, the pressure drop remains almost constant.
5.Increase in velocity causes the pressure drop to rise exponentially.