Air pollution control device for lead acid battery manufacturing units.
Lead acid battery manufacturing consists of various stages which broadly involve (after producing or receiving lead oxide):
•Paste mixing
•Grid casting
•Grid pasting & curing
•Hydro setting, parting & enveloping
•Stacking, grouping & intercell welding
•Formation
Exposure of workmen to lead during all or any of the processes outlined above exceeds the prescribed standards if appropriate equipment in this respect is not installed at any battery manufacturing unit.
All of the above processes, some more than others, involve release of lead particles or fumes into the environment.
Pollution from the above processes can be grouped into two possible types, viz:
•Lead oxide becomes airborne and there is particulate pollution
•Fumes are generated and there is gaseous pollution
While first five of the above listed broad stages fall in the ambit of particulate pollution, last one is the cause for gaseous pollution. Of those classified under particulate pollution, only paste mixing & grid pasting are the major source of the same.
To control the pollution generated in these operations, suitable air pollution control device are to be installed. These are commonly also called ventilation systems or fumes extraction systems etc.
They have to be selected based on many factors which include:
•Size of the operations
•Physical layout of the unit
•Relative location of different points of generation of pollution
•Particular processes to be covered
Broadly, on the basis of nature of pollutants involved, the air pollution control device can be dealing with non-corrosive or corrosive gas streams. They are hence, designed accordingly.
Battery crushing and hydro separation
Battery crushing and segregation plants are required for handling of large volume of battery scrap to feed smelting units. In this automated system, batteries of all sizes are loaded on conveyor and fed into hammer mill. Batteries are crushed into small pieces and particles are collected at the bottom of hammer mill in a container. The container is already filled with water solution of specific gravity. The plastic material floats on the top of water solution and lead bearing scraps settles at the bottom in the container.
The plastic is removed from the top with the help of water jet system. The bottom of container is fitted with screw conveyor for discharge outlet for lead bearing scrap. The lead bearing scrap is conveyed through screw conveyor to a vibrating screen, where large particles are retained and collected. They are further dried and used as raw material for smelting unit.
The fine particles at the bottom of container are kept in agitation and after that passed through filter press to form a cake. This cake is further dried and used as a raw material for smelting unit. The plastic material is collected, washed further for processing. The portion of waste water is taken into treatment plant and similar amount is replaced with fresh water.
There are very few battery crushing and hydro separation units installed with corporate groups. It is not viable for small and medium scale units because of high capital investment. Gradually parties are interested to install battery crushing and hydro separation units since it is mandatory to have same for import of used batteries in india.
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: 2400mm L x 1900mm W x 2400mm H
No. of Ovens: 2 Nos.
Oven Size
Top Dia: 600mm
Bottom Dia: 250mm
Depth: 650mm
No. of FD Fans: 2 Nos. (1 for each oven)
FD Fan Capacity: 300cmh at 250mm of WG
No. of Charging Doors: 2 Nos. (1 for each oven)
Charging Door Dimensions: 1100mm H x 650mm W
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 100% 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.
About Induction Melting Furnace
Induction Melting Furnace is major steel producing technology using scrap & sponge iron (directly reduced iron) as main raw material. This technology contributes significant steelmaking capacity in secondary steel sector in India and abroad. It has
Air Pollution
Steel scrap comes from various sources and generally has contaminants/coating etc on it. When this scrap is heated contamination/coating etc. disintegrates from steel and comes out either as slag or becomes air borne, thus causing air pollution. The major source of Air Pollution is :
1. Dust & Dirt
2. Rust
3. Oil & Grease
4. Paint & Galvanized Iron
5. PVC Coated Steel
Selection of Technology for Air Pollution Control Device
The following technologies are usually adopted for Air Pollution Control System in Induction Furnace industry:
a. Bag Filter Type System (Dry)
b. Venturi Scrubber Type System (Wet)
About Bag Filter Type System (Dry Process)
Working of Equipment Bag Filter Type System
1. Suction Hood
2. Spark Arrestor:
3. Bag Filtration System :
4. ID Fan:
5. Stack (Chimney):
Advantages:
1. Low Power Consumption
2. Dry System, No water pollution
3. No corrosion of metal except normal wear & tear
4. Suitable for dust pollution which are the major cause of pollution in induction furnace
5. Achieves desired characteristic of treated gases even for high dust load, as
Efficiency of bag filters is very high
6. Low operation & maintenance cost
Control Practices
About Venturi Scrubber Type System (Wet Process)
Working of Equipment Venturi Scrubber Type System
1. Suction Hood:
2. Ducts & Bends:
3. Venturi Scrubber:
4. ID Fan :
5. Stack (Chimney) :
Advantages :
1 Low Floor Area
2 Can handle high temperature gases
3 Suitable for gas pollution such as SO , NO , etc. 2 x
Disadvantages :
1 Higher Power Consumption to achieve desired standards
2 Generates Water Pollution
3 Material of Construction is prone to corrosion hence low life cycle
4 Choking of pipe, Nozzle and duct (near scrubber) due to Wet condition
5 Higher operation & maintenance cost
6 Can remove submicron particle only with very high pressure drop leading to still higher power consumption
7 Material of Construction is prone to corrosion hence low life cycle
8 Choking of pipe, Nozzle and duct (near scrubber) due to Wet condition
9 Higher operation & maintenance cost
10 Can remove submicron particle only with very high pressure drop leading to still higher power consumption.
About Rotary Furnace
The Rotary Melting Furnace is a very flexible and universal equipment used for recycling many non-ferrous metals. It is the major lead production technology used in India and many other countries for Secondary Lead Production. A lead production system based on this technology has certain distinct characteristics such as:
•Equipment scalable for installing higher capacities
•Recovers all lead in one production cycle
•Plates & powder from scrap battery as well as slag from Mini Blast Furnace can be used as raw material
•Requires addition of certain consumables
•Can be fired with various fuels
•Generates high Pollution both as Flue Gases & Fugitive Emissions
Description of Rotary Furnace
It is a Rotary kiln in the form of a metallic cylinder with conical sides on both ends. Mild steel plate is used for construction of this shell and its thickness varies depending upon the capacity of the equipment. This shell is rotated on its own axis at 1-2 rpm. For this purposes tyres (also called riding rings) are fitted on the shell. These are fabricated from MS squares or flats, machined for a smooth finish. These tyres ride on steel rollers which are again machined finely. These rollers are fitted on a robust MS structural frame and driven by a gear & motor arrangement. The shell is lined inside with insulation and fire bricks of suitable Alumina content.
Conical ends of the furnace are open on both sides. The furnace is charged with Raw material along with additives from the front end. This side is provided with a movable door on which a burner is mounted. The burner can be a conventional one or a fully automatic one depending upon the fuel used. At the other end, an exhaust block lined with refractory bricks is provided. A tapping hole is provided in the center of the shell from where molten metal & slag are discharged. Flue gases generated are sucked from the exhaust block side of the furnace.
A typical 3.0 TpB Rotary Furnace has the following standard sizes & specifications :
•Outside dimensions of the Rotary
•Shell dia : 2075mm
•Shell length : 2500mm
•Total length : 4500mm
•Charging dia : 450mm
•Exhaust side dia : 450mm
•Refractory thickness : 200mm
•Fuel : Furnace Oil
•Burner : Model 4 A Make: Wesman with complete assembly
•FD Fan capacity : 550 cmh at 44mm of WG
•Gear Box in drive : 8”, 1:40 Ratio
•Motor in drive : 15.0 HP x 960 RPM
•Structure used for base : ISMC 250 x 80
Advantages
•Recovers 100% lead in the first operation.
•Slag produced is lead free.
•Equipment can be scaled up for higher production capacities.
Disadvantages
•Many chemicals are required for operation.
•High power consumption.
•Difficult to produce low Antimony lead suitable for soft lead purposes.
•Fugitive Emissions need to be captured in addition to flue gases.
•Need skilled operators and careful maintenance.
UNIVERSAL TILTING ROTARY FURNACE (UTRF) for Lead recycling
the above mentioned photograph under production capacity 10 ton/batch.
Universal Tilting Rotary Furnace is designed like a rotary closed well furnace. It has advantages of rotary furnace, rebvetory furnace and dry hearth furnace in a single equipment.
Main advantage of UTRF is that it can be rotated as well as tilted. Firstly lead scrap is loaded in furnace with smelting flux and furnace locked. The material is heated with the help of oil/gas burner which is mounted on the door, until it reaches melting point. Heating is immensely faster because of horse shoe flame design. Due to the quick heating, consumption of oil and melt loss is very less as compared to the conventional tube furnace.
Merits of Universal Tilting Rotary Furnace:
1. Less amount of flux is required for melting.
2. Efficient working condition.
3. All non-ferrous scrap can be recycled in a single unit.
4. Homogenous charge resulting in high quality of material.
5. Self-cleaning of lining.
6. Recurring cost is approximately 30% less as compared to horizontal rotary furnace.
7. Ensures faster melting rate.
8. Better yield.
Comparison between UTRF and Horizontal fixed axis Rotary Furnace:
The traditional furnace (fixed axis rotary furnace) is primarily a rotating tube with burner on one end and flue at the other. The furnace functions under negative pressure and gets cold air from outside making it virtually impossible to control the atmosphere in the furnace, which is nearly always oxidizing (air rich). It view of it, large amount of flux is required to protect the charge. Consumption of oil is also high because travel length of flue gas is less.
On the other hand, UTRF furnace is designed with a single entrance and exist point. The door carries burner and flue. The furnace operates under positive pressure and during firing of the burner there is complete absence of cold air from outside resulting in reduced amount of flux required during operation. In addition the furnace operates at an angle, the charge is mixed with similar action that of a concrete mixing machine. This improves homogeneity heat transfer resulting in high thermal efficiency.
Salient Features of Universal Tilting Rotary Furnace:
1. Tap to tap cycle time 4- 5 Hrs.
2. Energy consumption 600 Kw/MT
3. Robust steel structure with proven drum
4. Life of refractory lining is long
5. Oversize driving system and bearings.
6. Tilting, door opening and closing is hydraulically operated.
7. Sturdy interlocks for safety of the equipment.
8. Less manpower required. Only two persons per shift can operate the furnace.
About Lead Refining
Lead recycled from used lead acid batteries or other sources (Secondary Smelting) via the Mini Blast Furnace or Rotary Furnace route, contains lot of contamination and undesired components. On the other hand, Lead required for battery manufacturing 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. These include – “Re-Melting” for removal of slag, “Refining” for attaining required purity levels and “Alloying” for producing various alloys of lead.
The equipments used are the same, the consumables and the processes, however, differ.
Description of Melting Pot
The Melting Pot (or Refining Pot or Alloying Pot, as it is variously called), is a mechanical mixing device with a pot and a heating arrangement. The inner pot is made of heavy MS plate with dish end bottom. It is placed within a jacket of refractory bricks, which in turn, are protected by an outer cover of MS plate with reinforcements. The pot is covered at the top with opening for feeding lead ingots and is provided with an electro-mechanical mixer. At the bottom, a heating source, usually an oil fired burner, 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 from the pot through an outlet pipe and valve.
Capacity of such pots depends upon the requirements of particular units. Standard pot capacities made are from 4.0 TpB to 20.0 TpB. Higher capacity pots are also manufactured as required by any particular establishment.
A typical 10.0 TpB Refining Pot has the following standard sizes and specifications:
•Diameter (ID) : 1150mm
•Height : 1250mm (+Dish Depth of 200mm)
•Flange Width : 350mm
•Outer Shell Diameter : 1900mm
•Stirrer MoC & Dia : SS-304 & 75mm
•Stirrer Motor : 5.0 HP x 960 RPM
•Outlet Valve Size : 40mm
•Burner : Diesel Fired
•Fuel Consumption Range : 8-18kg/ltr
Melting pots are installed both with and without accessories which may include Ingot Casting Machine, Ball Making Machine (where Ball Mills are installed down the line), Air Pollution Control Systems, Jib Cranes etc.
This ingot casting conveyor will operate in conjunction with a suitable capacity of refining pots. Your require ingot casting machine to produce 25~26 kg lead ingots with a production capacity of 10 tons per hour.
The final system will be composed of the following machines and equipments
Technical specifications of auto ingot casting machine
This ingot casting conveyor will operate in conjunction with a suitable capacity of refining pots. Your require ingot casting machine to produce 25~26 kg lead ingots with a production capacity of 10 tons per hour.
The final system will be composed of the following machines and equipments
1. Flow control box (tundish)
2. Tilting launder: -
3. Distributor wheel:
4. Ingot casting conveyor:
The conveyor will be complete when assembled with:
4.1. Ingot mould: -
4.2. Conveyor chain:
4.3. Idler- end assembly:
4.4. Drive end assembly:
4.5. Ingot knockout arrangement:
4.6. Ingot retaining mechanism:
5. Mould cooling arrangement:
6. Pre-heating arrangement:
7. Control system:
Battery cutting machine (semi-automatic)
Main parts:
Conveyor:
Guide rail:
Cutter house:
Cutter platform:
Control panel:
Additional features:
•curtains at outlet to contain debris
•height marker to adjust height of cutter wheels
•modular panels of cutter house for easy maintenance
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Lead acid batteries contain lead bearing raw material inside the pvc or rubber containers. For recycling, pvc and other material need to be segregated from lead bearing raw material. For this purpose processes of battery cutting or crushing are adopted.
Ball mill for lead oxide is a basic device in the modern world of metallurgy and is extensively used in a variety of applications. Among others, it's applications in the processing of non-ferrous metals is one of the most important. In the field of lead processing, dry type ball mills are used for conversion of lead pellets into fine lead oxide powder (lead oxide free lead), also commonly called grey oxide due to its appearance. The ball mill with its preparatory and collecting equipments is therefore also called a grey oxide plant.
Description of process:
Lead is melt in a melting pot and cast into pellets (hemispherical or cylindrical shape) at a ball making machine and fed into the ball mill. The ball mill is rotated on its own axis at low speeds. The rotation of the mill imparts tumbling & cascading action to the balls fed (in this case the lead pellets). The rotation is adjusted so that the raw material inside does not reach critical speed. Below the critical speed (at around 65 - 75%), the balls which are carried along the walls of the mill fall back to the center. This continuous action leads to friction and generation of heat which induces the reaction of lead (pb) with oxygen (o2) present in air and generation of lead oxide (2pbo). This reaction is an exothermic reaction which leads to generation of heat and this sets of a chain reaction of heat generation and accelerated oxidation process. Draft of air through the mill carries small sized or light particles outside the mill to the collection system. Temperature within the mill is controlled with the help of water spray outside the barrel of the mill. Several crucial characteristics of this produce such as free lead percentage, retention percentage, apparent density are set as per requirements of the client.
Jumbo ingot mould
Jumbo ingot moulds are collection trolleys used for collecting molten lead from rotary furnaces. They can be of varying capacities, ranging from 500 kg. , 750 kg. And 1000 kg. The most prevalent of the same is 500 kg. Ingot mould. Due to higher weight of the cast, it is called a jumbo ingot mould.
These moulds have trolley type structure with two unidirectional wheels at the back and one free spin wheel at the front. It is provided with a handle to pull it. They are moved manually or on rails electro-mechanically, varying from unit to unit. They are smoothened on the inside and do not have any sharp folds or edges. They are usually constructed in sg cast iron for longer life and increased strength.
We also provide basket type of jumbo ingot moulds for handling with material handling device i.E. Eot crane.
Typical parameters for a 500 kg jumbo ingot are
Shapepyramidical hopper type
Size – top500mm x 500mm (inside)
Size – bottom350mm x 350mm (inside)
Height500mm
Mocsg iron
Thk40mm
Back wheels200mm dia x 50mm wd
Front wheel150mm dia x 50mm wd.
About Steel re-Rolling Mill
Steel Re-rolling is a major steel section and bar producing technology used in India and abroad. Since its inception in India with setting up of first re-rolling mill in Kanpur in 1928, this technology has contributed significant steelmaking capacity in secondary steel sector in India.
Air Pollution
Depending upon the fuel used in heating the furnace of a Steel Re-rolling Mill, the characteristics of flue gases may vary. For coal fired furnaces they may consist of gaseous as well as particulate pollutants. For oil or gas fired furnaces, these flue gases may consist of just gaseous pollutants. The flue gases may also be corrosive in nature.
Selection of Technology for Air Pollution Control Device Selection of Technology for Equipment in an Air Pollution Control System in case of a Steel Re-rolling Mill depends upon the fuel to be used :
a. Scrubber based System for Oil / Gas Fired Furnaces
b. Cyclone and Scrubber based System for Coal Fired Furnaces
About Scrubber based System for Oil / Gas Fired Furnaces
Characteristics of Air Pollution Generated In Induction Furnace
1 Pollutants : Dust & Gases such as NO , SO , CO, Co x 2 2
2 Concentration : SPM - 1200-1500 mg/Nm (Maximum, in coal fired)
3 So - 800-1000 mg/Nm 2
4 NO - 20-50 mg/Nm x
5 Temperature : At Suction Point: 250-300 C
6 Nature of Dust : Slightly Sticky, Non Abrasive and Non Explosive
Control Practices
The control practice adopted in controlling air pollution in this industry mainly depends upon following parameters :
1 Dust/Gas Concentration at inlet
2 Discharge Standards
3 Temperature of Flue Gases
4 Nature of Pollutant i.e. Dust (Particulate) or Gaseous
5 Nature of Dust i.e. Sticky, Abrasive
6 Nature of Gases i.e. Corrosive, Non Corrosive
Working of Equipment
1. Ducts & Bends :
2. Scrubber :
3. ID Fan :
4. Stack (Chimney) :
About Cyclone and Scrubber based System for Coal Fired Furnace
Working of Equipment
1. Ducts & Bends :
2. Cyclone :
3. Scrubber :
4. ID Fan :
5. Stack (Chimney) :
Discharge Characteristics as Per Norms
1 Dust : Less than 150 mg/ Nm
2 Temp : Less than 80-100 C
3 Gases : Traces of SO , NO , Co , Co.
Sewage and its Treatment
Sewage is the spent water stream generated after use of fresh water in various activities of domestic, non-industrial nature, such as washing water, food preparation waste, laundry waste, and other waste products of normal living including sanitary
Waste water.
This sewage, if discharged untreated into water bodies, leads to their pollution and degradation of the most valuable resource of all – water. Sewage hence needs to be treated before its discharge and after that, can also be reused for some applications such as toilet flushing and gardening etc.
Sewage Treatment Plant and its Process
A Sewage Treatment Plant, commonly called as STP, is domestic waste water treatment plant used to achieve the end of making spent water pollution free before its disposal or re-use. It mainly consists of 3 stages:
Preliminary, Biological and Tertiary:
Depending upon the intended end use of treated water, a fourth stage of advanced treatment may also be considered.
Preliminary Treatment
Consists of screening and removal of oil and grease (if applicable) for which mostly physic mechanical processes are used. The purpose of this stage is to remove external large solid/ floating material as well as floating oils in the stream so as to make it suitable for biological treatment stage.
Biological Treatment
Is the stage where organic impurities in the waste stream are treated by the use of microbial organisms. These organisms metabolize the pollutants as their food either in presence or absence of air, called aerobic or anaerobic processes respectively. The sludge so generated is settled and ultimately flushed out from the system.
It is thus, the Biological Reactor which is the HEART of any Sewage Treatment Plant and it is on the basis of the same, that all processes are classified into different groups. Other than this, different stages of all processes are similar.
Tertiary Stage consists of disinfection and filtration. Disinfection is required for the purpose of removal of any residual harmful bacteria in the water stream. Filtration is used to remove any TSS in the stream and also for polishing the treated water clean.
Sewage Treatment Plant & Process:
1 Resistant to shock loads
2 Widely used and accepted
3 Properly digested sludge
4 Low maintenance cost
5 Recycling of Sludge into the reactor
6 Low retention times of 12-16 hrs.
7 No External Media
8 Easy to operate and maintain.
