Challenge

Week 8 - Simulating Cyclone separator with Discrete Phase Modelling

AArpit Hardiya11 Jan 2023

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]

What is Cyclone separator ?

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 precleans 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 multicyclone

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. This spiral formation and the separation is shown in Figure 2. 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.

Geometry

Import the cyclone separator geometry in space claim.
Extract the volume
Suppress the Sheetmetal model for physics
Close the space claim.

Meshing

Generate the mesh.
Change the method to Cartesian method and reduce the mesh size to 5mm

Setup

Enable the gravity and set the value as -9.81m/s
Energy equation
Chose k -epselon model and use RNG under RNG option chose swirl dominated flow
Open discrete phase model and chose interaction type as continuous phase
Select injection to for particle size setting.
Use the particle size as 5 micron and velocity as 3m/s
- Inlet Boundary conditions fluid domain velocity as 3 m/s and change the DPM to reflect from escape.
- For outlet 1 DPM is set to escape and for outlet 2 DPM is set to Trap.
Initialize the model using standard model
Results

Case 1
1. particle size 5 micron with velocity of 3m/s, and inlet boundary condition of 3 m/s
Residual
Area weighted pressure at inlet
Area weighted pressure at outlet-1 (escape)
Particle Tracking:
  Separation Efficiency in % = (185 / 378) * 100

  Separation Efficiency = 48.9 %
2. particle size 3 micron with velocity of 3m/s, and inlet boundary condition of 3 m/s