ELECTROSTATIC PRECIPITATORS FOR A THERMAL POWER STATION OVERVIEW, ERECTION PLAN & CONSTRUCTION FEATURE PART -I

Air pollution is the presence of some substances added directly or indirectly

by different operations in such quantity and of such duration so as to affect

or try to affect human beings ,animal , vegetations , materials , climates etc

adversely. Example of primary air pollutants are CO;SO2,NO2 etc , second-

ary pollutants are O3, NO2, H2SO4,HNO3 etc. Thermal Power station

operation with oil and coal as fuel are source of these pollutants and also ash

from burnt out coal. On average if two and half rake of coal are used in the

power station then there will be one rake of ash to be cleared.

NATIONAL AMBIENT AIR QUALITY STANDARDS ( NAAQS)

                                                                        Land Use.

Pollutants         Average time    Industrial      Residential, Rural    Sensitive

SO2                    ANNUAL          80                         60                    15

NO2                   --DO----             80                         60                    15

SPM                   --DO----           360                       140                    70

RPM (<10microns) - do --          120                         60                   50

LEAD (Pb)           --do---                 1.0                    0.75               0.60

(All values are micro gramme / metre cube. )

AMMONIA          ---do---                0.1                     0.1                0.1

( All values are milligramme / metre cube)

In earlier days i.e. before the use of ESP mechanical devices like i) Settling

chamber  ii) Cyclone Separator  iii) Bag House Filter iv) Wet scrubber.

Out which Bag House Filter type of precipitators are still in use specially by

Chinese suppliers.

However once technology of ESP comes into force all other separators

became obsolete. The performance of ESP can now be guaranteed up

to 99.97%.

Electrostatic precipitators is most widely used device to control particulate

emission in Industry now.

Electrostatic Precipitation is physical process by which particles suspended

in gas stream  are charged electrically and  under the influence of electric

field  are separated from the gas stream. The precipitation system consist of

positively charged collecting surface ( Termed as collecting electrode ) and

high voltage negative charged wire suspended from the top of the frame to

bottom the frame hook ( Termed as emitting electrode). The total frame was

suspended from the top through a high voltage insulator. At a very high DC

voltage to the tune 50 KV to 70 KV are applied  between emitting and

collecting electrode and a corona discharge occurs close to emitting

electrode . This will charge the whole gas path across the electrode and

particulate charged with negative charge will attract towards the +ve

collecting electrode and gets deposited on the surface.

A Typical ESP area  foundations are getting ready for start of erection.

 



Base Column erection under progress for an ESP pass.

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