» REFINING POTS
About Lead Refining
Lead recycled from used lead acid batteries or
other sources (Secondary Smelting) via the Mini Blast Furnace or
RotaryFurnace route, contains lot of contamination and undesired components.
On the other hand, Lead required for batterymanufacturing is either soft
Lead with 99.97% purity or hard Lead of varying Antimony compositions.
In order to make quality of lead suitable for its different uses, different
variations of pot melting processes are employed.
- "Re-Melting" for removal of slag,
- "Refining" for attaining required purity levels and
- "Alloying" for producingvarious alloys of lead.
- The equipment used is the same, the consumables and the processes,
Refining Pot Details
The Refining Pot (or Refining Kettle or Alloying
Pot, as it is variously called), is a mechanical mixing device with a pot
and aheating arrangement. The inner pot is made of heavy MS plate with dish
end bottom. It is placed within a jacket of refractorybricks, which in turn,
are protected by an outer cover of MS plate with reinforcements. The pot is
covered at the top withopening for feeding lead ingots and is provided with
an electro-mechanical mixer. At the bottom, a heating source, usually anoil
fired/ Diesel burner& sometimes by Wood burning is provided to heat the
pot and to melt the lead.Once lead melts, impurities are skimmed and removed
and any consumables required are added. Lead is then drained fromthe pot
through an outlet pipe and valve.
Capacity of such pots depends upon the requirements of particular units.
Standard pot capacities made are from 3.0 Tons per Batch to20.0 Tons per
Batch. Higher capacity pots are also manufactured as required by any
Melting pots are installed both with and without accessories which may
include Ingot Casting Machine, Ball MakingMachine (where Ball Mills are
installed down the line), Air Pollution Control Systems, Jib Cranes etc.
Melting Processes have been grouped as
- Re-Melting Process
- Refining Process
- Alloying Process
This process is undertaken for value addition to the recycled lead from
furnaces. Lead is melted in the pot and major impurities are skimmed from it
to make it saleable in the market.
Lead is melted in the pot, additives such as Sulphur, Wooden Powder and
Coke Breeze are added and mixed gently followedby dross removal. Thereafter,
Tin is added to remove Copper and temperature is increased to 550-6000C.
Further, additivessuch as Sodium Nitrate & Caustic Soda are added to
remove Antimony. This process is repeated to get the desired purity oflead.
Lead is melted in the pot; additives such as Sulphur, Wooden Powder &
Coke Breeze are added and mixed gently followed bydross removal. Thereafter,
Tin & Antimony are added to the liquid metal to get the desired grade of
Melting processes lead to generation of air pollution
at the following stages
- Initial heating and melting generates fumes
- Drossing with sulphur, wooden powder and coke breeze generates lot of
smoke and dust particles
- Further heating for Refining and Alloying with different chemicals
generates fumes and dust particles.
Hence, to meet various goals of maintaining employees' health, factory
environments as well as regulatoryrequirements, it becomes imperative to get
high end Air Pollution Control Systems to be installed with the Melting
Characteristics of Air Pollution generated in Melting
- Dust : 500-600 mg/Nm3
- Temperature : 60-80° C
- Gases: Fumes and Dust
Discharge Characteristics required as per Norms
- Dust : Less than 50 mg/Nm3
- Lead ( Pb) : Less than 10 mg/Nm3
- Temperature : 50-60° C
- Gases : Not Detectable
Selection & Detailson Technology for Air
Based on the Parameters and the Standards
mentioned, the following technology is adopted for Air Pollution Control
Systemin Melting Pot is Pulse Jet based Bag House Filtration System
SUCTION HOOD: -
Aerodynamically designed suction hoods are provided to capture flue gases
generated at source itself.
DUCTS & BENDS: -
Ducts and bends are required to convey flue gases from point of suction to
final top of the chimney and connect variousequipments like suction hood,
bag house, ID fan and chimney. All bends and reducers are aerodynamically
designed and haveprovision of manhole cleaning mechanism.
BAG FILTRATION SYSTEM: -
It is used for final filtration of flue gases to remove fine dust
particulate matter using Pulse Jet Technology. Treated gases fromall the
bags are collected at top of bag house and passed through ID Fan to exhaust
the same to chimney. The dust is collectedat bottom of hopper and is
discharged through Rotary Air Lock Valve.
ID FAN: -
ID Fan provides necessary driving force to convey flue gases from top of
furnace to top of the chimney. The volume sucked overcomes the total
resistance offered by equipment and duct with the help of fluid horse power
provided by ID Fan driven bysuitable motor.
STACK (CHIMNEY): -
The generated gases are passed into atmosphere after treatment through
chimney of suitable height and diameter.