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PRESENTATION TOPIC;

Control of particulate emissions using cyclones

Presentation by

Komal ArooshM.Sc (4th semester)

DEPARTMENT

CENTER FOR COAL TECHNOLOGY

PUNJAB UNIVERSITY LAHORE


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QUESTIONS

What are the particulate emissions? Why its necessary to control the particulate emissions?

What systems are available to control the particulate emissions?

History of high efficiency cyclones

What is agglomeration spray?

Commercial applications of high efficiency cyclones Working principle

Advantages

disadvantages

Can a cyclone reach efficiencies of ESP / Bag filter / Wet scrubber?

Selection criteria

Outlook


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Particulate emissions are emissions characterized by

the presence of small particles of solids and liquids.

These common byproducts of combustion are amajor health and environmental concern in many

regions of the world, and steps have been taken to

reduce particulate emissions and to educate people

about their risks. These emissions are also known asparticulate pollution or particulate matter.

What are the particulate emissions?


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Sources of particulate emission can be man made ornatural.

the vast majority of such emissions coming from

factories around 10% coming from vehicles on the road.

Combustion of fossil fuels also releases othersubstances and particulatesinto the air

Some particulates occur naturally, originating fromvolcanoes, dust storms, forest and grassland fires,living vegetation, and sea spray.

Sources of particulate emissions



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Sometimes, particulate emissions are visible in

the form of soot or smoke, because the particles

are so large. Most are not visible, however,

which is part of what makes them dangerous,because people do not realize that the emissions

are occurring. Small particles are also more

dangerous because they are less likely to be

trapped in the mucus linings of the nose and

throat.

Why its necessary to control the particulate emissions?


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If the particles, which can be composed of any

combination of hundreds of chemicals and

elements, are able to get through the defenses ofthe nose and mouth, then they can find their way

into the lungs and possibly even pass into the

blood stream. This can cause respiratory problems

and potentially contribute to a higher risk forcertain types of cancer or heart disease.

Effect of particulate emissions on the humans



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The particulates may block their leaves so thatthey cannot photosynthesize properly.

The climate as a whole can be heavily impacted by

such emissions, as they can block the sunlight sothat it cannot reach the Earth.

Cause a decrease in crop yields, and contribute to

global warming trends.

Effect of particulate emissions on the plants


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For animals, particulate emissions pose a threat to

cardiovascular and lung health. In the lungs,

particulates can block or rupture the alveoli,

interfering with lung function. A number ofrespiratory conditions including asthma and

cancer are linked to exposure to particulate

emissions. The heart muscle and blood vessels can

also be damaged by particulates if they enter the

bloodstream through the lungs, causing

widespread medical problems.

Effect of particulate emissions on the animals


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But particulate emission control requirements

will become more and more stringent

Many stacks

Are still emitting

high levels

of particulate



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What systems are available to control

Particulate emissions ?

Electrostatic precipitatorBag house fabric filter

Wet scrubber

High efficiency cyclones


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Main steps of ESP

The processes of

electrostatic precipitator

are known as three main

stages:

particle charging

transport

collection.

Evaluation of ESP:High cost (investment, maintenance & operation)

Complex large size plant with sub-systems

Requires constant gas conditions (sulphur, temp, moisture)


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Evaluation of bag filters for industrial boilers:High cost (investment, maintenance & filter bags)

Difficult to handle sulphur and sparks

Not robust (one faulty bag destroys efficiency)

Main process of bag house fabric filterBughouses are very efficient particulate

collectors because of the dust cake formed on

the surface of the bags. The fabric provides a

surface on which dust collects through the

following four mechanisms: Inertial collection

Interception

Brownian movement

Electrostatic forces


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Evaluation of wet scrubbers for industrial boilers:High cost (large water treatment plant)

Difficult to separate fine particulate

Sulphur control costly & difficult


Main process of wet scrubber

Mechanism

Wet scrubbers relay on the liquid spray to

remove dust particles from the gas stream.

It is also useful in fume extraction systems.

It removes air pollutants by inertia of

diffusional impaction, reaction withabsorbent or reagent slurry or absorption

into a liquid solvent. The inlet gas stream

usually enters the bottom of the tower and

moves upward, while liquid is sprayed

downward from one or more levels.


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History:

1975 - 1980 work with Prof. Stairmond (UK)

Cyclones for coal fired gas turbine 80 MW PFBC

19931998basic research in

cyclone technology

Cape Town

development center



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Project 1996 / 97

30 year old Bttner solid fired wood chip dryer equipped

with low efficiency cyclone. Emission > 650 mg / Nm3

Solution:

Step 1 = retrofitting of high efficiency cyclones

Reduction of emission to < 100 mg / Nm3

Step 2 = installation of THERMAX agglomeration sprays

upstream of cyclones

Reduction of emission to < 20 mg / Nm3

First idea of agglomeration spray in 1997



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What is the agglomeration spray?

Water spray with very fine droplets

Fully evaporative (dry system)

Droplets capture small particles

and agglomerate them

Larger particles are easily collected

Typical water consumption

30 liter / t steam generation



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High efficiency cyclone plant

with fully evaporative

fine agglomeration sprays

(Installation 1997)

Efficiency > 99 %

Emission < 20 mg / Nm3



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Cyclones are inertial

separators that operate on

the principle of centrifugalforce to remove particles

from gas streams. A

standard cyclone design is

able to remove particlesthat have a size greater

than 20 m.


Cyclones


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Cyclones can be used as it is or combined

with other control device. Cyclones are used

to pretreat the gas stream by removing thepurge particles while the second device will

function to collect smaller particles present at

a much reduced particulate loading but at

higher collection efficiency.


Cyclones


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The dirty airs enter

the side.

The airs swillsaround the cylinder.

Particulate falls out

from the bottom ofthe cone and out.

Dust discharge


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Working principleThe working principle of the cyclone is as follow:

The gas stream enters the cyclone in a manner that spirals around

inside of the cyclones.

The particles with a great inertia will be forced to the outside walls of

the device. The particles will then fall to the cone to the collection hopper due to

the collision with the outside walls of the cyclone.

The clean gas will then rise near the center and is exhausted through

the top of the device.

There are two methods that cause the gas to spin in the cyclone.I. One of it's by introducing the gas to the device in a tangential

manner. The gas will curve around the body of the device.

II. The second method is by using axial vanes at the inlet of the

cyclones which will cause the gas to spin when it passes through

the vanes.



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Commercial applications of high efficiency cyclones:

BurnerMax

Fluidized bed furnace

High efficiency cyclonesoperating at 400 C



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Current CyDesign specifications for

advanced cyclone technology:

Integrated cyclone system with

fully evaporative agglomeration

water spray (20 l / h per cyclone)

To provide a robust, economic,

low maintenance,

very high performance,flue gas cleaning system



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Cyclone parts are manufactured to high precision as

erosion & corrosion resistant castings

Cyclone vortex blade ring

with pressure recovery

Wax dies

Castings



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Relative simplicity and few

maintenance problems

Relatively low operating pressure

drop (for the degree of particulate

removal obtained) in the range of

approximately 515 cm (26 inches)

water column

Temperature and pressurelimitations imposed only by the

materials of construction used

Dry collection and disposal

Relatively small space requirements


Advantages


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Disadvantages:

Low collection efficiency due to:

Bad manufacturing quality

Lack of maintenance (blockage of cyclone cells)

Inability to handle sticky materials

But cyclone system advantages are low cost and robust installation

Can a cyclone reach efficiencies of ESP / Bag filter / Wet scrubber?

This question triggered our cyclone development Program

in 1994 to improve cyclone efficiency and to invent thedry spray agglomeration principle



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Common control devices Pollutants Examples where they used

Electrostatic precipitators Particulate matters Power plants ,steel and paper

mills, cement plants ,oil refineries

Bag houses fabric filter Particulate matters Steel mills, fertilizer plants and

other industrial processes

Wet scrubber Gasses ,vapors , solid particles,

liquid particles

Coal burning power plants:

facilities that emit sulphur oxide,

hydrogen sulphide,ammonia and

other gasses that can be absorbed

in the water and can neutralized

with the appropriate reagent

Cyclones Large particulate matters Wood working shops, cotton gins,

rock crushers, cement plants


Examples where the common control devices used


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Selection criteria

ESP Bag house Scrubber High efficiency

Cyclones

Emissionmg/Nm3

100 30 200 < 100

Reliability ++ + ++ ++++

Cost ++++ ++++ +++ +



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Outlook:

Its necessary to

control the

particulate

emissions

For a cleaner

Environment!



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