Presentation on roaster and acid plant
(hindustan zinc ltd)
Company profile
• HZL was created from MCI in 1966.• In 2002, sterlite acquired 26% stack.• Chanderiya lead zinc smelter has annual
capacity of 100000 tpa zinc.• HZL has total capacity of 232000 tpa from its 3
plants in India.• It is largest zinc producing company in Asia.
Main products
• Zinc – mainly used galvanizing• Lead – mainly used in batteries
By products• Sulphuric acid – used in making fertilisers• Silver – photo films• cadmium- alkaline batteries
Extraction of zinc from zinc sulfideoccurs in three sections
• Roaster and acid plant• Leaching and purification plant • Cell house
RoasterIt has following parts
• Furnace• Waste heat recovery
boiler• Cyclone separator• Hot gas precipitator• Drum cooler
Raw material handling section flowsheet
Underground bin Magnetic separator screens
Concentration storage bin
Hammer mill
Roaster day bin Table feeder Slinger machine
furnaceBall mill Drum cooler
boiler
Hot gas precipitator cyclone
Horizontal chain conveyer boiler
Silos(2)
Sulphuric acid plant
There are four main process criteria.• Gas drying and water balance• Energy (heat) balance.• Conversion of SO2 to SO3 .
• required O2/SO2 ratio
Physical properties of acid
• It is colourless,water white ,viscous liquid,with MP 10 C,BP 280 C.
• It may be mixed with water in any proportion.• Density increases with increase in
concentration at fixed temperature.• Physical properties will depend on SO3
concentration.
Chemical properties
• Sulphuric acid is chemically and thermally very stable.
• Known hydrates are H2SO4 x H2O,H2SO4 x2H2O, and H2SO4 x 6H2O .
• Pure sulphuric acid is dissociated to only a small extent in accordance with equations .
2 H2SO4 = H3SO4+ + HSO4
-
2H2SO4 = H3O+ + HS2O7-
Wet gas cleaningThis is achieved by application of multistage process.
• Quenching tower• Packed gas cooling
tower• Wet electrostatic
precipitator
Wet gas cleaning flowsheet
Quenching tower
Packed gas cooling tower
Wet electrostatic precipitator
Drying tower
SO2
blower
wat
er
Hot SO2
Vapor SO2 W
eak
acid
SO2
Acid 96.5%
Converter system
• It is tower with four catalyst beds.• Inbuilt cooling tubes are provided.• Catalyst is alkali vanadium pentaoxide with
cesium salt promoter.• Four heat exchangers are provided to cool or
heat the gaseous stream.
Catalytic converter
HE 1
HE 2
HE 4
economiser
HE 3A
HE 3B
IAT
98.5%
FATStack
SO2 < 200ppm
400 c
425 c
433 c 443 c
165 c
400 c
410 c
270 c
180 c
Thank you