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