Smog Tower : "EMPOWER IAS"

In news:

• Ahead of its infamous smog season, Delhi has got a ‘smog tower’, a technological aid to help combat air pollution.

 

What are Smog Towers?

• Smog towers are structures designed to work as large-scale air purifiers. They are fitted with multiple layers of air filters and fans at the base to suck the air.
• After the polluted air enters the smog tower, it is purified by the multiple layers before being re-circulated into the atmosphere.

 

Structure of the Delhi smog tower

• The structure is 24 m high, about as much as an 8-storey building — an 18-metre concrete tower, topped by a 6-metre-high canopy. At its base are 40 fans, 10 on each side.
• Each fan can discharge 25 cubic metres per second of air, adding up to 1,000 cubic metres per second for the tower as a whole. Inside the tower in two layers are 5,000 filters.
• The filters and fans have been imported from the United States.

 

How does it work?

• The tower uses a ‘downdraft air cleaning system’ developed by the University of Minnesota.
• Polluted air is sucked in at a height of 24 m, and filtered air is released at the bottom of the tower, at a height of about 10 m from the ground.
• When the fans at the bottom of the tower operate, the negative pressure created sucks in air from the top.
• The ‘macro’ layer in the filter traps particles of 10 microns and larger, while the ‘micro’ layer filters smaller particles of around 0.3 microns.
• The downdraft method is different from the system used in China, where a tower uses an ‘updraft’ system — air is sucked in from near the ground, and is propelled upwards by heating and convection.
• Filtered air is released at the top of the tower.