Cyclone SeparatorPresented By:

Rahil Goel (13112070)Rajat Verma (13112071)Rakesh Lahre (13112072)Ramlal (13112073)Ranjan Tak (13112074)

Group No. 28

Overview

• Basic Definition

• Objectives

• Working Principle

• Design Procedure

• Types

• Advantages/Disadvantages

• Industrial Usage

A centrifugal separator

stationary mechanical device that utilizes centrifugal force to separatesolid or liquid particles from a carrier gas

What it is…

Cyclones have no moving parts and available in many shapes and sizes, for example from the small 1 and 2 cm diameter source

sampling cyclones which are used for particle size analysis to the large 5 m diameter cyclone separators used after wet scrubbers.

Classification of the dust collectors…

The flow enters near the topthrough the tangential inlet, which gives rise to an axially descending

spiralof gas and a centrifugal force field that causes the incoming particlesto concentrate along, and spiral down, the inner walls of the cyclone

separator.

Working principle

The collected particulates are allowed to exit out an underflow pipe while the gas phase reverses its axial

direction of flow and exits outthrough the vortex finder (gas outlet tube) .

Lets make things a bit

clear… Vortex Finder

Tangential inlet duct

Barrel

Cone

Dust Collector

Design procedures

Vertical cyclone separator

Horizontal cyclone separator

Multiple cyclone separator Single cyclone separator

TYPES

Design Parametersa = inlet heightb = inlet width Dx = vortex finder diameter Ht = total height of cyclone h = cylinder height S = Vortex finder diameter Bc = cone tip diameter

Design of experiment (DOE)

The statistical analysis is performed through three main steps.1) Construct a table of runs with combination of values of the independent variables via

the commercial statistical software STATGRAPHICS centurion XV by giving the minimum and maximum values of the seven geometrical factors under investigation as input. 

Table depicts the parameters ranges selected for the seven geometrical parameters. The study was planned using Box–Behnken design, with 64 combinations. A significant level of P<0.05 (95% confidence) was used in all tests. Analysis of variance (ANOVA) was followed by an F-test of the individual factors and interactions

http://www.sciencedirect.com/science/article/pii/S0009250910005245

Analysis of variance (ANOVA) showed that the resultant quadric polynomial models adequately represented the experimental data with the coefficient of multiple

determination R2 being 0.92848. This indicates that the quadric polynomial model obtained was adequate to describe the influence of the independent variables

studied . Analysis of variance (ANOVA) was used to evaluate the significance of the coefficients of the quadric polynomial models .For any of the terms in the models, a

large F-value (small P-value) would indicate a more significant effect on the respective response variables.

2)Perform the runs by estimating the pressure drop (Euler number).

Based on the ANOVA results presented in above table , the variable with the largest effect on the pressure drop (Euler number) was the linear term of vortex finder diameter, followed by the linear term of inlet width and inlet height (P<0.05); the other four linear terms (barrel height, vortex finder

length, cyclone total height and cone tip diameter) did not show a significant effect (P>0.05). The quadric term of vortex finder diameter also had a

significant effect (P<0.05) on the pressure drop; however, the effect of the other six quadric terms was insignificant (P>0.05). Furthermore, the

interaction between the inlet dimensions and vortex finder diameters (P<0.05) also had a significant effect on the pressure drop, while

the effect of the remaining terms was insignificant (P>0.05).

Most significant factor on the Euler number are The vortex finder diameter, with a second-order curve with a wide range of inverse

relation and a narrow range of direct relation, Direct relation with inlet dimensions, Inverse relation with cyclone total height and insignificant effects for the other factors.

3)   fill in the values of pressure drop in the STATGRAPHICS worksheet and obtain the response surface equation with main effect plot, interaction plots, Pareto chart and response surface plots beside the optimum settings for the new cyclone design.

Cyclone collector design consideration

• Particle size ( particles with larger mass being subjected to greater force),

• Force exerted on the dust particles • Time that the force is exerted on the particles

Mathematical models and equations

fluid mechanics and particle transport equation air into the cyclone with an inlet velocity Vin. Assuming that the particle is spherical, a simple analysis to calculate critical separation

particle sizes. considers an isolated particle circling in the upper cylindrical component of the cyclone

at a rotational radius of r from the cyclone's central axis, the particle is therefore subjected to drag, centrifugal, and buoyant forces. The fluid velocity is moving in a spiral the gas velocity. Velocity can be broken into two component velocities: a tangential component, Vt, and an outward radial velocity component Vr

Assuming Stokes' law, the drag force in the outward radial direction that is opposing the outward velocity on any particle in the inlet stream is:

Using ρp as the particles density, the centrifugal component in the outward radial direction is:

. Using ρf for the density of the fluid, the buoyant force is:

• Optimization of the cyclone separator geometry for minimum pressure drop using mathematical

• Models and CFD simulations, Vrije Universiteit Brussel, Department of Mechanical Engineering, Research Group Fluid Mechanics and Thermodynamics, Pleinlaan 2, B-1050 Brussels, Belgium

Source

Vp is equal to the volume of the particle (as opposed to the velocity). Outward radial motion of each particle is found by setting Newton's second

law of motion equal to the sum of these forces:

To simplify this, we can assume the particle under consideration has reached "terminal velocity", i.e., that its acceleration dVr/dt is zero.

This occurs when the radial velocity has caused enough drag force to counter the centrifugal and buoyancy forces. This simplification changes our equation to:

Which expands to:

Solving for Vr we have

density of the fluid > the density of the particle, the motion is (-), toward the center of rotation

density of the fluid <the density of the particle, the motion is (+), away from the center.

In non-equilibrium conditions when radial acceleration is not zero, the general equation from above rearrange to

• Since Vr is distance per time, this is a 2nd order differential equation of the form :

Experimentally it is found that the velocity component of rotational flow is proportional to r2 ,

Limitations and Alternate models

the geometry of the separator is not considered, the particles are assumed to achieve a steady state.

A major limitation of any fluid mechanics model for cyclone separators is the inability to predict the agglomeration of fine particles with larger particles, which has a great impact on cyclone collection efficiency.

computational fluid dynamics (CFD) is a conventional method of predicting the flow field and the collection efficiency of a cyclone .

Three models in cyclone simulation: k–ε model, algebraic stress model (ASM) and RSM.

The k–ε model adopts the assumption of isotropic turbulence, so it is not suitable for the flow in a cyclone which has anisotropic turbulence.

ASM cannot predict the recirculation zone and Rankine vortex in strongly swirling flow.

RSM forgoes the assumption of isotropic turbulence and solves a transport equation for each component of the Reynolds stress. It is regarded as the most applicable turbulent model for cyclone flow.

To predict the mean particle diffusion in turbulent flow, both Lagrangian and Eulerian techniques can be used. 

Advantages of cyclones are

• the collected product remains dry and, normally useful.

• low capital investment and maintenance costs in most applications.

• very compact in most applications.

• can be used under extreme processing conditions

• can be fabricated from plate metal or, in the case of smaller units,

• can, in some processes, handle sticky or tacky solids with proper liquid irrigation.

• can separate either solids or liquid particulates; sometimes both.

• no moving parts.

• very robust.

Some disadvantages of cyclones are low efficiency for particle sizes below their ‘cut-off diameter when operated

under low solids-loading conditions. usually higher pressure loss than other separator types, including bag filters

and low pressure drop scrubbers. subject to erosive wear and fouling if solids being processed are abrasive or

‘sticky.

• ship unloading installations• power stations• spray dryers• fluidized bed and reactor riser systems (such as catalytic crackers\and cockers)• synthetic detergent production units• food processing plants• crushing, separation, grinding and calcining operations in the mineral and chemical industries• fossil and wood-waste fired combustion units• vacuum cleaning machines• dust sampling equipment

Industrial usage

Cyclone efficiencyThe efficiency of a cyclone has direct effect on the pressure drop. Higher efficiency cyclones have highest pressure drops

Different levels of collection efficiency and operation are achieved by varying the standard cyclone dimensions.

The collection efficiency of cyclones varies as a function of density, particle size and cyclone design. Cyclone efficiency will generally increase with increases in particle size and/or density; inlet duct velocity; cyclone body length; number of gas revolutions in the cyclone; ratio of cyclone body diameter to gas exit diameter; inlet dust loading; smoothness of the cyclone inner wall.Similarly, cyclone efficiency will decrease with increases in the parameters such as gas viscosity; cyclone body diameter; gas exit diameter; gas inlet duct area; gas density; leakage of air into the dust outlet.

What we plan to do in the coming month

We know that a smaller and compact cyclone has more efficiency than a bigger cyclone.

A lot of industries would be functioning on larger cyclones and therefore would have a large scope of cost reduction as the efficiency of the system could be increased.

We will take up full data from the industry of the TAC and the efficiency of the cyclone and will try to provide a better modelwith greater efficiency in the same cost.

We plan to do this…

Increasing Efficiency on the way

In final presentation we will use computational fluid dynamics, response surface methodology and Reynolds stress model for determining the behavior

of cyclone separator.

According to patent:

“The separating efficiency of a cyclone separator can be increased by retarding the partices before they arrive at the cyclone and then accelerating them over the short distance before they enter the cyclone.

In this way the larger particles will have lower speed than small particles when entering the cyclone and hence the separation of the fine particles is improved.”

An Example…

Avg. Particle size in range Wt percentage1 03

5 20

10 15

20 20

30 16

40 10

50 0660 03

>60 07

Estimating cut diameter and the overall efficiency of the cycloneGiven data:

Gas viscosity = 0.02 Cp

Specific Gravity of the particle = 3.0 Inlet gas velocity of cyclone = 48 ft/sec

Effective number of turns within cyclone = 5

Cyclone diameter = 8 ft

Cyclone inlet width = 2 ft

Cut Diameter

First We will calculate ρp –ρ = 3(62.4)=187.2 lb/ft3

Then we will calculate the cut diameter:

Collector efficiency can be calculated as:

Dp.(um) wi Dp/Dpc Ei,% WiEi.%1 .03 .11 0 0.0

5 .20 .55 23 4.6

10 .15 1.11 55 8.25

20 .20 2.22 83 16.6

30 .16 3.33 91 14.56

40 .10 4.44 95 9.5

50 .06 5.55 96 5.7

60 .03 6.66 98 2.94

>60 .07 - 100 7.0

References• PhD_thesis_Khairy_Elsayed

• Nptel

• http://www.sciencedirect.com/science/article/pii/S0009250910005245

• https://en.wikipedia.org/wiki/Cyclonic_separation

• Optimization of the cyclone separator geometry for minimum pressure drop using mathematical models and CFD simulations, Vrije Universiteit Brussel, Department of Mechanical Engineering, Research Group Fluid Mechanics and Thermodynamics, Pleinlaan 2, B-1050 Brussels, Belgium

• Numerical study of gas–solid flow in a cyclone separator, Center for Simulation and Modelling of Particulate Systems and School of Materials Science and Engineering, University of New South Wales, Sydney, NSW 2052, Australia

Thank You…