タイトルまたは説明
Mini Blast Furnace (Mandir Bhatti) with Air Pollution
Control Device
for lead smelting Recycling plant
About Mini Blast Furnace
A Mini Blast Furnace (commonly known as Mandir Bhatti or Shahi
Bhatti) is a simple, time-tested and widely used system to
produce secondary lead in India and many other countries. It is
the most basic of all furnaces and a production system based on
this technology has certain distinct characteristics such as:
- Low Project Capital Cost
- Low Energy Cost ( wooden coke fired)
- Easy to install
- Easy to operate & maintain
- Production of low Antimony Lead (soft lead) at low
temperature
- Generates high pollution
Description Of Mini Blast Furnace
The Furnace itself is a modified blast furnace which consists of a
brick lined structure with fire brick oven in the midst and a metal
Exo-skeletal structure outside. Raw material & fuel (coke) is
charged manually through the side metal doors fitted in the brick
structure and air is provided from the FD fans provided at the back
of the brick structure. Molten metal & slag is tapped at the
pits made in front of the brick structure and flue gases are sucked
from the top of the brick structure which is provided with a
metallic hood.
A typical Double Oven Mini Blast Furnace has the following
standard sizes & specifications:
- Outside Dimensions of Brick Structure :
***0mm L x ***0mm W x ***0mm H
- No. of Ovens
: 2 Nos.
Oven SizeTop Dia
: **0mm
- Bottom Dia
: **0mm
- Depth
:
**0mm
- No. of FD Fans
: 2 Nos. (1 for each oven)
- FD Fan Capacity
: **0cmh at **0mm of WG
- No. of Charging Doors
:
2 Nos. (1 for each oven)
- Charging Door Dimensions
: ***0mm H x **0mm W
Manufacturing Process
Lead to be manufactured from Mini Blast Furnace is usually obtained
from scrapped batteries. They are cut open or broken to segregate
lead scrap, plastic and other materials from it. Lead scrap in the
form of lead powder and plates etc. is charged in the furnace along
with a proportionate charge of wooden coke. Thereafter the furnace
is manually fired with the help of rags. FD Fan provides the
necessary air required for combustion from the back of the furnace.
Coke in the oven performs the functions of both, the fuel as well
as a reducing agent for obtaining lead from its oxides charged in
the form of lead plates & powder.
Temperature of the furnace is maintained at the desired level for
approximately *0 minutes, after which molten lead along with slag
flows out from the bottom of the oven into the outlet pit. Here
slag is separated and molten lead is poured into Ingot Moulds. To
maintain this, continuous charge of raw material and coke is
maintained in the furnace.
This process leads to generation of flue gases which are toxic in
nature and need appropriate and adequate Air Pollution Control
System for their treatment.
Process Details for a typical Double Mini Blast
Furnace
Raw Material Charged
: ******0 kg/ hr.
Fuel used
:
Wooden Coke
Calorific Value of Fuel used :
********0 kCal/ kg.
Advantages
- No consumables used other than Wooden Coke which is also used
as Fuel
- Low Power Consumption
- Produces low Antimony Lead suitable for soft lead purposes
- Pollution can be controlled with minimum fugitive emissions
- Easy to install, operate & maintain
Disadvantages
- Cannot recover **0% lead in the first operation
- Subsequent recovery of lead after first recovery consumes
higher coke & manpower.
- Equipment cannot be scaled up for higher production
capacities.
Air Pollution Control System for Mini Blast
Furnace
Various types of lead present in used batteries, plates and paste
of lead oxide are charged in the furnace. In addition to these,
certain compounds of sulphur are also present in the batteries.
When this material is heated in the presence of carbon, lead
oxide is converted to lead. This conversion along with burning of
fuel generates flue gases and fumes containing dust, dirt, oxides
of lead, lead particles and other impurities etc.
Hence, to meet various goals of maintaining employees' health,
for factory environments as well as regulatory requirements, it
becomes imperative to get high end Air Pollution Control Systems
to be installed with the Mini Blast Furnaces.
Characteristics of Air
Pollution generated in Mini Blast Furnace:
Dust
: *********0 mg / Nm3
Temperature :
******0oC
Gases
: Traces of NOx, SO2 and CO
Discharge Characteristics required as per
Norms:
Dust
: Less than *0 mg / Nm3
Lead (Pb) :
Less than *0 mg / Nm3
Temperature :
****0o C
Gases
: Traces of NOx , SO2 and CO
Selection of Technology for Air Pollution Control
System
Based on the parameters and the standards mentioned, the
following technology is adopted for Air Pollution Control System
in Mini Blast Furnace:
- Gravity Chamber
- Involute Cyclone
- Pulse Jet based Bag House Filtration System
Details of Air Pollution Control Device with
functions
-
Duct & Bends: Ducts and Bends are
required to convey flue gases from point of suction to final
top of the chimney and connect various equipments like spark
arrestor, gravity chamber, cyclone, bag house, ID Fan and
chimney. All bends and reducers are aerodynamically designed
and have provision for manhole cleaning mechanism.
-
Gravity Chamber: It is a low pressure
drop device which:
- Allows large size particles to settle down
- Cools down temperature of flue gases
- Used as spark arrestor to entrap live or red hot particles
3. Involute
Cyclone: Cyclone is used to remove medium size
particles from flue gases stream.
The treated flue gases are discharged from
top and dust is collected at bottom.
4. Bag Filtration
System: It is used for final filtration of flue
gases to remove fine dust particulate
matter using Pulse Jet Technology. Treated gases from all
the bags are collected at top of bag
house and passed through the ID Fan to exhaust the
same through chimney. The dust is
collected at bottom of
hopper and is discharged through Rotary Air Lock Valve.
5. ID Fan: ID Fan
provides necessary driving force to convey flue gases from top of
furnace to top
of the chimney. The volume
sucked overcome the total resistance offered by equipment and
duct
with the help of fluid horse
power provided by ID Fan driven by suitable motor.
6. Stack
(Chimney): The generated gases are passed to
atmosphere after treatment through
chimney of suitable
height and diameter.
Wet Scrubber for Air Pollution Control
Device
A Wet Scrubber in the Air Pollution Control System is mandatory
in India and many parts of the world. Wet Scrubber uses
water to scrub clean the flue gases of any pollutant gases or
particles that may remain after Bag Filtration System. The
Scrubber therefore requires a pump, pipeline and a retention
tank.
The size of the Scrubber depends upon the capacity of the system
being installed. Flue gases are introduced in the body of the
Scrubber from side and as they move up towards the top of the
Scrubber which has the outlet, they pass through a spray of fine
water droplets provided by a spray shower provided in the body.
This fine spray leads to scrubbing of any pollutant in the flue
gases. Cleaned gases escape through the top opening after passing
through a mist eliminator whereas water with pollutants moves to
the bottom of the Scrubber from where it is passed into the tank.
One or more chambers of the tank allow for settling of pollutants
which are then periodically cleaned and fresh water is added to
make up any loss in quantity of water. It is then recirculated to
the Scrubber.
