The most important aspect of Lead Smelting operation is treatment of effluent gases, which generates by reduction / smelting operation. These pollution control equipments are designed and tested in house at various degree of operations on various atmospheric conditions. It consists of suitable size Dust collecting chamber (Settling Chamber), Cyclone Separator, Cooling Tower, Ducts, Spark Arrestor, Bag Filter House unit, Wet-Scrubber, Induced Draft Fan and Chimney through which flue gases finally forced out.
These pollution control equipments, are totally, controlled for any kind of over pressure and over temperature. At the inlet of Bag House, Spark Arrestor would be installed, which will catch the sparks coming in the bag house and prevent the burning of Filter Bags. Automatic temperature controlled system at the inlet of bag house is provided. The temperature controller will sense the temperature of hot air gases and open the fresh air damper valve to control the temperature of incoming gas before entering into the Bag House.
Bag Filter House is a 100% polyester Non-woven fabric filter bags fitted in the bag holding cage and equipped with pulse jet type cleaning arrangement. Filter unit is designed for continuous operation and operates at 5 – 7 Kg./sq. cm. compresses dry air. Electrically actuated solenoid valves control the whole system of compressed air through 10 stage electronic sequential timer.
The filter bags are capable of catching the particulate matter as small as up to 5 microns size. Wet scrubber scrub sulfur di-oxide from the flue gas and dust particles in the gas stream, if any with the help of scrubbing water sprayed on packed bed in the scrubber. Induced draft Blower is connected with controlling air damper and loose flexible connection at inlet with Wet scrubber and outlet connected to the chimney of about 30 meter Height.
Pollution Control & Waste Management
In Lead Smelting/ Recycling process following equipment in series mainly form Pollution Control system:
- Dust Collector
- Cooling Tower
- Spark Arrester
- Bag House
It is a sort of Gravity Settling Chamber, the gravity-settling chamber consist of a chamber with baffles in which the gas velocity is reduced to enable dust to settle out by the action of gravity. Here normally the settling of particles larger 100 micron takes place. The velocity of flue gases entering into the dust collector will not be more than 2 m/sec and designed for minimum turbulence in chamber for easy settlement.
It is connected after Dust Collector where flue gas path involves a double vortex with the gas spiraling downward at the outside and upward at the inside. When the gas enters the cyclone, its velocity undergoes redistribution so that the tangential component of velocity increases with decreasing radius. The spiral velocity in a cyclone reaches a value several times the average inlet-gas velocity. These cyclone collects the dust up to the size of 50 Micron.
It is connected after the Cyclone where the flue gases are allowed to cool down up to 1200C to 1300C to avoid burning of filter bags. This is properly designed as per the ambient air temperature and based on the heat transfer through conduction and convection. At the bottom of the cooling tower screw conveyor with Rotary air lock valves are provided to collect discharge dust in the bins.
It is also installed after the cooling tower and just before to the bag house to avoid entering any spark into the bag house. Because of any spark, polyester filter bags may get burnt. To avoid such type of problem the spark arrester is designed and fitted before the bag house.
It is present in series, after Spark Arrester and contains filter bags through which dust laden gases passes. Filter bags are made of 100% polyester non woven fibers with Anti adhesive finish for water repellence and easy dust release with 550+ 50 GSM weight of filter cloth and air permeability of 15 m3/m2/min at ½” WG.
These filter bags are capable to filter 33000 CMH flue gases at temperature of 120oC-130oC in the presence of pulse jet cleaning system, which works at the air pressure of 6 kg./cm2 .
Screw Conveyor equipped with Rotary air lock valve is provided at the bottom discharge end for dust removal.
It is one of the most essential equipment in the series for controlling pollution mainly removing gaseous pollutants. Counter Current vertically upward flow flue gas against water spray through the packed bad improve efficiency of removal of most unwanted gas from flue gas by water. Mist generated during wet scrubbing action is controlled by mist eliminators present in wet scrubber before flue gas outlet port.
|The circulating water absorbs Sulfur Di-Oxide gas and the acidic water formed which passes through Water Treatment Plant and get neutralized. Neutralized water is re-circulated in the system.
Chimney is provided for venting flue gases and dispense pollutants at altitude helping to ease down its influence on surrounding over greater area reducing pollutants concentration in compliance with regulatory limits.