Question

Laser fume from plastics, metals and wood comprises harmful particulate matter. This industrial dust needs to be extracted from air when an operator is engaged in the laser cutting process.

(i) Explain how both a cyclone and an electrostatic precipitator work, and then, giving your reasons, rationalise why, out of the two technologies, you would recommend using electrostatic precipitation to be used for extracting dust during laser cutting of plastics. (6 marks)

(ii) The efficiency (E) of an electrostatic precipitator with plate collectors is given by: E = 1 – exp(-AW/Q) where: A is the area of the plates (in m2 ) Q is the gas flow rate (in m3 /s) W is the particle drift velocity in an electric field (in m/s) which can be estimated as being numerically equal to onetwentieth of the average particle diameter (in microns). If the laser cutting of a plastic produces PM2.5 particles with a concentration of 12 g/m3 in an air flow rate from the production line of 8 m3 /s, estimate both the plate area required to achieve 90% efficiency in removing the particles from the air stream, and the daily particulate mass removed by the electrostatic precipitator

Answer 1

Inertia. Cooker mixtee Solid Comise So working of Cyclone Sepertor. Cyclone Sepcietor now on principle of A Centrifugal Poice. It is used to Separete the Solid pesticles from id-gen by by utilising inertia of Sond Particles. In the techinque the velocity through Conical Structure creating vortex inside & Eluring this gros flows ep words way! & Corse porticles Thrown aside due to Bottom at high mixture is blown vertical in helical ote collected at cie insotica لین + T T gasin T 个 1个 1个 ES Ir theated working of ESP! cyclone ESP work on Principle that when Particle is kept in strong electric field it experiences ripolorisation hence to one of charged poles. In Esp ger. of Fine Porticles pass tro plates mainlained high voltage & Result due to on plates Chorge acquied by them in mede Consisting to through at ionise op pending on

For separating Loser fume inerna i to high electric field Connsting hormful Particulate motter not sufficient To seperate by cyclone hence con be. Subjected to tónu & Seperate by Electic field- ml-exp(-Ary) Drøm%s Wa I (9.5% m=0.9 expl-Aw/a)-0-1 à 1.95 xioł m/s Jo Anyago5 14.72 x 15 m² A=go 5x8 1095X107

using given data and equtions we can find the requried area

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