EXPERIMENT 3 :

CYCLONE SEPARATOR

1.0 OBJECTIVES

1.1 To demonstrate the cyclone separation operation and measure the pressure drop

against input velocity.

1.2 To determine the cyclone separation efficiency on different air flow rate.

1.3 To evaluate the relationship between separation efficiency and flow rate.

2.0 INTRODUCTION

Cyclone separation is a typical solid-gas or liquid solid separation device. It consist of a

vertical cylinder with a conical bottom, a tangential inlet near the top and an outlet for dust at

the bottom of the cone. A cyclone separator is a mechanical device using geometry and

centrifugal acceleration to affect separation of suspended particles from a gaseous or liquid

stream. It can be designed for high temperature and pressure operation.

Collection efficiency

The collection efficiency typically depends on the movement of gas and particles and also

the particles sizes.

1. Cyclone fractional efficiency

Cyclone fractional efficiency is the weight of stated size of particles collected in the hopper

divided by the total weight of the same size particles entering the cyclone. Referring the

paper proposed previously, the collection efficiency increase as:

- The increase of particles size and density

- Increasing speed of cyclone rotation in the cyclone vortex.

- Decreasing cyclone diameter.

- Increasing cyclone length.

2. Cyclone grade’s efficiency

A cyclone grade efficiency curve related the particle size to the cyclone efficiency on particle

of that size going to the cyclone. The grade efficiency curve for Stairman’s high efficiency

cyclone (Figure 1) show that efficiency continuously increase with increasing the particle

diameter, and approach to 100% asymptomatically for a sufficient large particle. Efficiency is

generally good for dusts where particle diameters are larger than 5 µm.

Figure 1 : Cyclone grade efficiency, high efficiency standard design and optimized design

The efficiency of cyclone often related to its critical size or its cut size. A critical size is

defined as the size of particles calculated to be collected with 100% efficiency. Cut size

defined as the aerodynamics equivalent diameter of the particle collected with 50%

efficiency. Lapple (1951) related the cyclone’s efficiency with the particle cut size. From the

studies, the actual efficiency of cyclone increase gradually with increase in the ratio of dp/dpc

as shown in Figure 2. dpc represent the cut size of particle, which can be calculated by :

Where,

µG = gas viscosity, kg/ms

b = cyclone body diameter, m

ρp = particle density, kg/m3

Vg = Gas velocity, m/s

Ne = number of turn the gas makes in the cyclone. Friedlander et.al (1952) proposed

that,

this value can be a constant varying from 0.5 to 1, with typical value of 5.

Figure 2 : cyclone efficiency versus dp/dpc, from Lapple (1951)

Theodera and DePaola (1980) then fitted an algebraic equation into the curve proposed by

Lapple (1951) as below:

Where,

ƞj = collection efficiency of particle in the jth size range (0 < Ci < 1)

dpj = characteristic diameter of the particle size range (µm)

The overall cyclone efficiency defined as,

Where,

mj = mass of the particle in the j

M = total mass of particle

The performance of cyclone can be improved with drawing some gas from cyclone by the

exit duct or wetting the cyclone’s wall.

Pressure Drop

Pressure drop is an important parameter in order to evaluate the cyclone performance. The

pressure drop in a cylinder only considered at the inlet and outlet location. It contributed by :

1. Loss due to the expansion gas when it enters the cyclone chamber

2. Loss as kinetic energy of rotation in the cyclone chamber.

3. Losses due to wall friction in the cyclone chamber

4. Any additional friction losses in the exit duct, resulting from swirling flow above and

beyond those incurved by straight flow.

5. Any regain rotational kinetic energy as pressure energy

Many models have been developed to estimate the pressure drop in cyclone separator,

among them, Shepherd and Lapple (1939) and Stairmand (1949, 1951) are most common

used. However these model are either empirical or theoretical; none of them predicts the

pressure drop accurately. It is know that pressure drop is a function of the cyclone

dimensions, particles properties and its operating conditions such as inlet air velocity.

Shepherd and Lapple (1939, 1940) converted inlet velocity heads into pressure drop in term

of static pressure head, AP with the equation derived below :

Where,

Vg = gas velocity through cyclone inlet, m/s

ρG = gas density

ΔH = pressure drop in inlet velocity head

G = acceleration of gravity

ρL = Liquid density

C.J Stairmand assume that the total energy loss is due to losses in the cyclone vortex, plus

entrance and exit losses. The empirical pressure drop equation given by Stairmand (1949)

is,

Where,

Here, G is a friction factor approximately equal to 0.005 and A is the inside surface of the

cyclone exposed to the spinning gas. A value for A can be calculate from :

3.0 MATERIALS & APPARATUS

3.1 Cyclone separation trainer

3.2 Filter bag

3.3 Acrylic resins

3.3 Dust particle (or other test samples)

LEGEND

A Dust Tank F Air blower

B Cyclone A G Water tank

C Cyclone B H Control Panel

D Cyclone C I Pressure different meter for cyclone B and

Cyclone D

E Cyclone D J Duct

4.0 PROCEDURE

4.1 Measurement Of Pressure Drop Against Input Velocity

1. The cyclone separation chamber trainer apparatus was placed on the ground.

2. The 3 phase 5 pin plug was plugged to the main power supply. The power supply

was turned ON.

3. The power supply unit in front of the control panel was switched ON.

4. The entire cyclone inlet valve except cyclone B valve was closed.

5. The digital differential meter was tare zero by pressing the zero buttons.

6. The blower was switched ON by pressing the run button. The frequency was Set to

10 Hz. The reading from the differential pressure meter was recorded.

7. The blower speed was increased with 5 Hz increment until 30 Hz. The air blower was

off. The cyclone B valve was closed and the cyclone D valve was switched ON. The

step 6 to 8 was repeated.

8. The air speed in the cyclone for each different frequency was calculated.

9. The graph of air peed against blower frequency for both of the cyclones were plotted.

Note :

Relationship between the frequency of the motor and the velocity :

4.2 Measurement Of Cyclone Separation Efficiency on Different Air Flow Rate

1. The cyclone separation trainer apparatus was placed on ground.

2. The 3 phase 5 pin plug was plugged to the main power supply. The power supply

was turned ON.

3. The power supply unit in front of the control panel was switched ON.

4. The entire cyclone inlet valve except cyclone A valve was closed. The feed tank

valve was closed.

5. 50 g of acrylic resin (initial sample) was measured and pouted into tank A (feed tank).

6. The filter bag was fixed to the bottom outlet of the cyclone. The weight of the filter

bag was measured before fixed into the bottom outlet of the cyclone.

7. The blower was switched ON by pressing the run button. The frequency was set to

10 Hz. The air was allowed to circulate for about 2 minutes.

8. The feed tank valve was opened. The air flow pattern in the cyclone was

investigated.

9. The dust was ensured is all completely channel into the cyclone.

10. The blower was stopped by pressing the stop button.

11. The filter bag was removed and the weight of the filter paper was measured.

12. The experiment was repeated by varied the air flow rate.

13. The separation efficiency for each different flow rate was calculated.

14. The experiment was repeated by using different test sample.

15. The experiment was repeated by using the 200 mm cyclone.

16. The graph of separation efficiency against blower speed for both of the cyclones was

plotted.

Note:

Final sample weight = final filter bag weight – initial filter bag weight

Separation efficiency, n = (final sample weight – initial sample weight)

Initial sample weight

5.0 RESULTS

5.1 Measurement of Pressure Drop Against Input Velocity

Frequency (Hz)ΔP (Pa)

100 mm Cyclone 200 mm Cyclone10 350 4515 820 8420 1470 13825 2160 20030 2207 322

Frequency (Hz)Speed in Cyclone (m/s)

100 mm Cyclone 200 mm Cyclone10 24.512 8.78915 37.520 12.00920 50.235 15.39225 60.895 18.53030 61.554 23.511

v = √(2 [P stagnation - P static]) / ρ

5.2 Measurement of Cyclone Separation Efficiency on Different Air Flow Rate

100 mm CycloneBlower Initial Filter Final Filter Final Initial Separation speed Bag Weight Bag Weight Sample Sample Eficiency(Hz) (g) (g) Weight (g) Weight (g) (%)15 30.00 36.45 6.45 50.00 -0.8720 30.00 36.00 6.60 50.00 -0.8725 30.00 36.92 6.92 50.00 -0.8630 30.00 36.46 6.46 50.00 -0.87

200 mm CycloneBlower Initial Filter Final Filter Final Initial Separation speed Bag Weight Bag Weight Sample Sample Eficiency(Hz) (g) (g) Weight (g) Weight (g) (%)15 30.00 39.51 9.51 50.00 -0.8120 30.00 39.30 9.30 50.00 -0.8125 30.00 39.65 9.65 50.00 -0.8130 30.00 39.50 9.50 50.00 -0.81

Final sample weight = Final filter bag weight - Initial filter bag weightSeparation efficiency, n = (final sample weight - initial sample weight) /

initial sample weight

6.0 DISCUSSION

Based from the experiment, it is found that in the 100mm Cyclone, the separation efficiency is consistent throughout all four blower speeds. The exact same reading of -0.87 % was given out . A slight deflection of reading at 25 Hz was observed and yet it does not disrupt the consistency of the reading too much.

In the 200mm Cyclone experiment, the similar case was recorded and the separation efficiency was all at -0.81 %. The efficiency of cyclone often related to its critical size or its cut size.

The pressure reading in the 100mm Cyclone is higher as compared to the 200mm counterpart, where the highest reading exceeds 2000Pa (2207 Pa). This is due to the diameter size of the cyclone which generates higher pressure if it is small. However, lower pressured cyclones are much more efficient than higher pressured cyclones in terms of particle containing. In Table 5.2,it can be observed that the values given by the 200mm Cyclone are higher than the ones in 100mm.

Pressure also relates very well the speed of the cyclone, where the higher pressure and the smaller the diameter, the higher the velocity.

7.0 CONCLUSION

In a nutshell, the experiment was set to demonstrate the cyclone separation operation and measure the pressure drop against input velocity, to determine the cyclone separation efficiency on different air flow rate and also to evaluate the relationship between separation efficiency and flow rate.

From the post-experimental calculation done, the relationship between the pressure, cyclone speed and diameter was able to be determined. The mass of particles that was able to be determined and the relationship between the aforementioned parameters can be proven.

8.0 QUESTIONS

8.1 Discuss the finding from the graph obtained.

(refer 6.0 discussion)

8.2 Explained the working principle of cyclone separation unit. How does the particle can be

separated away from the air in the cyclone?

Cyclonic separation is a method of removing particulates from an air, gas or liquid

stream, without the use of filters, through vortex separation. Rotational effects

and gravity are used to separate mixtures of solids and fluids. The method can also be

used to separate fine droplets of liquid from a gaseous stream. A high speed rotating

(air) flow is established within a cylindrical or conical container called a cyclone. Air flows

in a helical pattern, beginning at the top (wide end) of the cyclone and ending at the

bottom (narrow) end before exiting the cyclone in a straight stream through the center of

the cyclone and out the top.

Larger (denser) particles in the rotating stream have too much inertia to follow the tight

curve of the stream, and strike the outside wall, then falling to the bottom of the cyclone

where they can be removed. In a conical system, as the rotating flow moves towards the

narrow end of the cyclone, the rotational radius of the stream is reduced, thus separating

smaller and smaller particles. The cyclone geometry, together with flow rate, defines

the cut point of the cyclone. This is the size of particle that will be removed from the

stream with a 50% efficiency. Particles larger than the cut point will be removed with a

greater efficiency, and smaller particles with a lower efficiency.

8.3 State two (2) methods / steps to increase the efficiency of the cyclone separator.

i) Increase the diameter, increase the pressure

ii) Decrease the velocity

8.4 State the application and where the cyclone separator in normally installed.

Factory, dust emittors