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Introduction

Principle of process

Gas solid cyclone separators is a device invented to separate the particles from an air stream,

have been widely used in many industrial processes, such as air pollution control and

environmental cleaning processes due to their well adaptability to harsh conditions, simplicity todesign, and low costs to operate and maintain. The cyclone designs are generally classified into

straight-through, uni-flow, and reverse-flow cyclones according to the purpose in use. Among

them, it is known that the use of tangential inlet and reverse-flow is the most common way for

cyclone design.

As of the above mentioned many merits of cyclone, much attention have been paid on

predicting the flow fields in cyclones both by experimental and numerical methods for last few

decades. The performance of a cyclone separator is generally characterized by the collection

efficiency of particles and the pressure drop through the cyclone. According to the many

researches, the cyclone height, diameter, and shape (i.e., cylinder or rectangular), the shape

and diameter of vortex finder, and the inlet geometry can influence considerably the

performance of the cyclones.

The gas cyclone mechanism can be simplified as a device where inlet gas is brought

tangentially into a cylindrical body. A strong vortex is created inside the cyclone and any

particles in the flow, if they are denser than the carrier gas, are subjected to centrifugal forces.

These forces move the particles radially outwards, towards the inside cyclone surface onto

which the solids deposit.

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Schematic diagram of solid gas cyclone separator

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Basic design of solid gas cyclone separator

The gas flow is forced into a downward spiral simply because of the cyclones shape and the

tangential entry. Another type of cyclone employs an axial inlet with fixed turning vanes to

achieve a spiraling flow. Centrifugal force and inertia cause the particles to move outward,

collide with the outer wall, and then slide downward to the bottom of the device. Near the bottomof the cyclone, the gas reverses its downward spiral and moves upward in a smaller inner spiral.

The cleaned gas exits from the top through a vortex-finder tube, and the particles exit from the

bottom of the cyclone through a pipe sealed by a spring-loaded flapper valve or rotary valve.

The turbulence of gas flow is obtained by the use of the Reynolds stress model. The resulting

pressure and flow fields are verified by comparing with those measured and then used in the

determination of powder flow. The separation efficiency and trajectory of particles from

simulation are shown to be comparable to those observed experimentally. The effects of particle

size and gas velocity on separation efficiency are quantified and the results agree well with

experiments. Some factors which affect the performance of cyclone were identified. It is shown

that the collision between gas streams after running about a circle and that just entering

occurred around the junction of the inlet duct and the cylinder of the cyclone, resulting in a

short-circuiting flow. The combination of flow source and sink was distributed near the axis of

cyclone, forming a flow dipole at axial section. Particles entering at different positions gave

different separation efficiency. A particle with size exceeding a critical diameter, which was

condition-dependant, would stagnate on the wall of cyclone cone. This was regarded as one of

the main reasons for the deposition on the inner conical surface in such cyclones used in the

cement industry.

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Process and application of solid-gas cyclone separator

The processes in the design of the solid-gas cyclone separator are as follows. The gas flow is

forced into a downward spiral simply because of the cyclones shape and the tangential entry.

Centrifugal force and inertia cause the particles to move outward, collide with the outer wall, and

then slide downward to the bottom of the device. Near the bottom of the cyclone, the gasreverses its downward spiral and moves upward in a smaller inner spiral. The cleaned gas exits

from the top through a vortex-finder tube, and the particles exit from the bottom of the cyclone

through a pipe sealed by a spring-loaded flapper valve or rotary valve.

The physical phenomena involved in the separation of solids from gases are influenced by a

number of important factors such as the properties of the gas, and gas-particle and particle-

particle interactions. These factors are briefly reviewed here first before addressing the

principles of various types of gas-solids separators. Inertial Separators cover devices in which

the main property used in recovering particles is their density, so that they are removed by

centrifugal action. Deliberate changes in the direction of gas flow causes the particles

trajectories to deviate from the gas streamlines, thus concentrating and separating the particles

from the gas. Inertial separators are varied in design. Most separators in this category use

passive mechanical separation with induced centrifugal motion, such as cyclones. There are

however separators in which the centrifugal motion is induced by a rotating propeller. These

devices are often used for classification purposes.

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Background of company

The application of solid gas cyclone separator chosen was when applied in a cement industry,

specifically Cahya Mata Sarawak (CMS).

Literally translated, the Bahasa Melayu expression cahya mata means "the light of the eye" butit is far closer in meaning to the English expression "the apple of ones eye" i.e. a person or

group of people in whom you take great pleasure and for whom you feel great pride. Thats why

they have adopted "The Pride of Sarawak" as the rallying cry for even greater development and

progress, and the theme for their Annual Report 2003. Living up to the meaning of their name,

and meeting the expectations it creates, requires them to find opportunities and develop

strategies that will make all Sarawakians proud of CMSB proud of their achievements, proud

of their performance, and their commitment to accelerate the economic, infrastructure and social

development of Sarawak for the benefit of all.

Since our inception in 1974, CMSB has grown and developed from a humble manufacturer of a

single product, ordinary Portland cement, to become a highly diversified conglomerate playing a

key role in Malaysia s financial services and infrastructure development sectors. Our extensive

portfolio of businesses, products and services, has made us a leading conglomerate on Bursa

Malaysia with an annual turnover of more than RM1 billion. As the largest conglomerate in the

State, we play our part as a major contributor to Sarawaks remarkable economic and

infrastructure development. Our history is peppered with many noteworthy firsts - the first East

Malaysian company to produce Portland cement; the first bumiputra-owned bank in Sarawak;

the first Sarawak-based company to be listed on Bursa Malaysia; the first licensed stockbroker

of Sarawak; and many more.

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Processes of a solid-gas cyclone separator

In a solid-gas cyclone separator, particles are suspended in a moving gas stream possesses

inertia and momentum and acted upon by gravity. The gas stream is introduced tangentially into

a cylindrical vessel at the top. The particles are thrown outwards against the cylindrical wall of

the vessel, eventually carried by gravity towards the dust collector at the bottom of the unit. Theclean gas move spirally downwards, gradually approaching the central portion of the separator

and then rise and leave through the central outlet at the top. Tangential velocity (how fast the

gasses are swirling) is lowest near the wall and at the center of the cyclone. It reaches

maximum at a point approximately 60% to 70% of the way from the wall to the center.

Generally, a decrease in diameter will increase efficiency (

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Process flow diagram

Dirty air enters at inlet

Concentration of dustparticles along the wall

Descending vortex

Dust discharge andcollected at the bottom

Clean air exits at thetop

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Conclusion

As conclusion, solid-gas cyclone separators are commonly used to separate the particles from a

conveying gas. The performance of a cyclone separator is characterized by two parameters,

namely pressure drop and collection efficiency. As for the choice for cleaning air or filtering air

for large scale industries, solid-gas cyclone separators are inexpensive. Solid-gas cycloneseparators are simple in design, little floor space required, dry continuous disposal of collected

dusts, low to moderate pressure loss, handles large particles and high dust loading and is

temperature independent.

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References

1. http://www.muellerenvironmental.com/documents/Fundamentals%20of%20Gas%20Solids%20

Liquids%20Separation.pdf

2. http://www.cmsb.com.my/

3. http://www.eng-forum.com/recycling/Plastic_Reycling_Cyclone.htm4. http://engineering.dartmouth.edu/~d30345d/courses/engs37/Cyclones.pdf

5. Industrial process notes

http://www.muellerenvironmental.com/documents/Fundamentals%20of%20Gas%20Solids%20Liquids%20Separation.pdfhttp://www.muellerenvironmental.com/documents/Fundamentals%20of%20Gas%20Solids%20Liquids%20Separation.pdfhttp://www.muellerenvironmental.com/documents/Fundamentals%20of%20Gas%20Solids%20Liquids%20Separation.pdfhttp://www.muellerenvironmental.com/documents/Fundamentals%20of%20Gas%20Solids%20Liquids%20Separation.pdfhttp://www.muellerenvironmental.com/documents/Fundamentals%20of%20Gas%20Solids%20Liquids%20Separation.pdfhttp://www.cmsb.com.my/http://www.cmsb.com.my/http://www.eng-forum.com/recycling/Plastic_Reycling_Cyclone.htmhttp://www.eng-forum.com/recycling/Plastic_Reycling_Cyclone.htmhttp://engineering.dartmouth.edu/~d30345d/courses/engs37/Cyclones.pdfhttp://engineering.dartmouth.edu/~d30345d/courses/engs37/Cyclones.pdfhttp://engineering.dartmouth.edu/~d30345d/courses/engs37/Cyclones.pdfhttp://www.eng-forum.com/recycling/Plastic_Reycling_Cyclone.htmhttp://www.cmsb.com.my/http://www.muellerenvironmental.com/documents/Fundamentals%20of%20Gas%20Solids%20Liquids%20Separation.pdfhttp://www.muellerenvironmental.com/documents/Fundamentals%20of%20Gas%20Solids%20Liquids%20Separation.pdf