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1. INTRODUCTION 1.1. WHAT IS VEDANTA?

They are an LSE-listed diversified FTSE 100 metals and mining company, and Indias largest non-ferrous metals and mining company based on revenues. Its business is principally located in India, one of the fastest growing large economies in the world. In addition, they have additional assets and operations in Zambia and Australia. We are primarily engaged in copper, zinc, aluminum and iron are businesses, and are also developing a commercial power generation business. FOUNDER: Founder of this recognition is Mr. ANIL AGARWAL, who is chairman of this group, a simple person without any special degree in management field but have a great experience in this field and a sharp sight of the future conditions and requirement.

1.2. ABOUT THE ORGANISATION 1.2.1. VISIONBe a world-class zinc company, creating value, leveraging mineral resources and related core competencies.

1.2.2. MISSION

Be a lowest cost Zinc producer on a global scale, maintaining market leadership Be innovative, customer oriented and eco-friendly, maximizing stake-holder value

The only integrated Zinc producer in India Refined Zinc production capacity 230,000 TPA Refined Lead production capacity 35,000 TPA Ore treatment capacity 4.6 Mtpa

Continuous operational improvements, meticulous planning, constant innovation, extensive R&D, technological upgradation and so much more - HZL has come a long way and grown into a multi-unit and multi-product company. Competitive position Zinc

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1.3.

HISTORY

Hindustan Zinc Ltd. was created from the erstwhile Metal Corporation of India (MCI) on 10th January, 1966 as a Public Sector Undertaking. In April 2002, the Government of India, disinvested its majority stake in HZL , and it became a part of the fast growing Sterlite group. Sterlite Opportunities and Ventures Ltd. (SOVL) India was founded in 1986, bringing together several metal related activities managed by the Agarwal family. In April 2002, acquired 26% stake and management control in HZL from the Government of India in privatization. Since the technology and costs were not in line with the global markets it was the right time for the Government to sell and SOVL to buy HZL. Since then HZL has been growing from strength to strength. HZL produces Zinc, Lead and other by-products including Sulphuric Acid, Silver and Cadmium. HZL achieved an all-time high with a record output of 2,61,226 tonnes Zinc and 6,14,938 tonnes of record production of Zinc concentrate during 2003-04. Today HZL is Indias leading base metal producer. HZL is a vertically integrated Mining & Smelting company, gearing up to:

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Harnessing mining resources to help India achieve self-sufficiency in Zinc. Become a global leader in Zinc. Create value for all entities whether it is Customers, Investors or Employees.

Constant innovation, meticulous attention to detail, extensive investments in R&D and technology are the hallmarks of HZL making it a multi-unit and multi-product company.

1.4.

HZL milestones at a glance:

2002-03 Sterlite acquires 26% and management control in HZL from the Government of India in privatization. A further 20% is bought from market through open offer and 18.92% from Government of India under call option. 1991 Chanderiya pyrometallurgical lead-zinc smelter and Rampura Agucha mine begin production. 1983 1977 1971 1968 1942 Rajpura Dariba Mine starts production. Vizag zinc smelter and second set of Zawar mine facilities commissioned. First expansion of Zawar mine commissioned. Debari smelter commissioned. Commencement of mining at Zawar.

HZL is a vertically integrated company with Mines and smelters spread across multi-locations

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1.5.

ZINC PRODUCTION

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1.6.

Chanderiya Lead Zinc smelter, Chittorgarh1991 120 km east of Udaipur, Rajasthan, India 100,000 tpa of refined Zinc, 35,000 tpa of refined Lead

Commissioned Location Capacity Details

A pyrometallurgical smelter using ISP technology. Main by-products are Sulp Acid and Silver and one of the by-product is Cadmium.

Certifications

ISO 9001:2000, ISO 14001:1996, OHSAS 18001:1999

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HZL MATRIXHZL

MINES

SMELTERS

ZAWAR MINES Commissioned: 1942 RC: 1.2 MTPA ore

RAMPURA AGUCHA Commissioned: 1991 RC: 3.75 MTPA ore

VIZAG ZINC SMELTER Commissioned: 1977 RC: 56000 TPA Zinc CHANDERIYA LEAD ZINC SMELTER Commissioned: 1991 RC: 275000 TPA Zinc

RAJPURE DARIBA MINES Commissioned: 1983 RC: 1 MTPA ore

DEBARI ZINC SMELTER Commissioned: 1968 RC: 80000 TPA Zinc

RC ~ Rated Capacity as in July 2006 THE HINDUSTAN ZINC LIMITED VARIOUS UNITS: LOCATIONS AND CAPACITIES CLZS (CHANDERIYA LEAD ZINC SMELTER)

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CLZS

UNIT 1 PYRO

UNIT 2 HYDRO

UNIT 3 CPP

ISF Technology Commissioned: 1991 RC: 105000 TPA Zinc 40000 TPA Lead

AUSMELT Technology Commissioned: 2005 RC: 50000 TPA Lead OUTOKUMPU Tech. Commissioned: 2005 RC: 170000 TPA Zinc

CAPTIVE POWER PLANT Commissioned: 2005 RC: 154 MW

RC ~ Rated Capacity as in July 2006

1.6.1. CLZS EXPANSION PHASES:

2. Zinc Hydro Plant Projects: Phase 1: Phase 2: 1,70,000 TPA Zinc plant commissioned in 2005 1,70,000 TPA Zinc plant project in progress, to be commissioned in 2007. 3. Ausmelt Lead Project: 50000 TPA Lead plant commissioned in 2005. 4. Debottleneckking and Modification of already existing Unit-1 Pyro Plant from 85,000 TPA Zinc to 1,05,000 TPA in 2005.

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5. CPP Captive Power plant Projects: Phase 1: 154 MW plant commissioned in 2005 Phase 2: 80 MW power project in progress, to be commissioned in 2007.

2. Introduction to Zinc & ApplicationsZinc or spelter (which may also refer to zinc alloys), is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2. Zinc is the 24th most abundant element in the Earth's crust and has five stable isotopes. The most exploited zinc ore is sphalerite, a zinc sulfide. The largest exploitable deposits are found in Australia, Asia, and the United States. Zinc production includes froth flotation of the ore, roasting, and final extraction using electricity (electrowinning). Brass, which is an alloy of copper and zinc, has been used since at least the 10th century BC. Impure zinc metal was not produced in large scale until the 13th century in India, while the metal was unknown to Europe until the end of the 16th century. Alchemists burned zinc in air to form what they called "philosopher's wool" or "white snow". Zinc is an essential mineral of "exceptional biologic and public health importance". Zinc

deficiency affects about two billion people in the developing world and is associated with many diseases. In children it causes growth retardation, delayed sexual maturation, infection susceptibility, and diarrhea, contributing to the death of about 800,000 children worldwide per year. Enzymes with a zinc atom in the reactive center are widespread in biochemistry, such as alcohol dehydrogenase in humans. Consumption of excess zinc can cause ataxia, lethargy and copper deficiency.

2.1. Applications of ZincOver 11 million tonnes of zinc is produced annually worldwide. Around 48% of the amount is used for galvanizing to protect steel from corrosion. Approximately 17% is used the production

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of zinc base alloys like die castings etc. Nearly 10% of the zinc is also utilized for compounds such as zinc oxide and zinc sulfate and about 11% is used in the alloys especially brass.

Galvanising: Zinc is one of the best forms of protection against corrosion and is used extensively in building, construction, infrastructure, household appliances, automobiles, steel furniture, and more. Galvanising accounts for around 48% of global zinc usage.

Zinc Oxide: The most widely used zinc compound, zinc oxide is used in the vulcanisation of rubber, as well as in ceramics, paints, animal feed, pharmaceuticals, and several other products and processes. A special grade of zinc oxide has long been used in photocopiers. 10% of global zinc usage is in this segment.

Die Castings: Zinc is an ideal material for die casting and is extensively used in hardware, electrical equipments, automotive and electronic components. 17% of zinc used in the word is through Die Castings.

Alloys: Zinc is extensively used in making alloys, especially brass, which is an alloy of copper and zinc. Alloy accounts for around 11% of global zinc usage.

Rolled Zinc: Zinc sheets are used extensively in the building industry for roofing, flashing and weathering applications. These are also used in graphic art to make plates and blocks, as well as battery callouts and coinage.

2.2.

Properties of Zinc (metallic) at 293K

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1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12.

Density Melting Point

: :

7140Kg./m3 693K

Specific Latent Heat of Fusion: 10 J/ Kg Specific heat capacity Linear expansivity Thermal conductivity Electric Sensitivity : 385 J/Kg/K : 31/K

: 111 W/m/k : 5.9 ohm meter

Temp. Coefficient of resistance : 40/k Tensile Strength : 150 Mpa Elongation Young modulus Passions Ratio : : 50% : 110 Gpa 0.25

3. Safety DepartmentSafety is a degree of control over hazards. Workers working in the factory are exposed to all sorts of dangers so some personal protective equipment are available to protect them head to toe such as1. Ear Muff 2. Dust Mask 3. Face Shield 4. Gas Mask 5. Gloves 6. Goggles 7. Helmets 8. Leg Guard 9. Respirators 10. Rubber Apron 11. Rubber Gum Boots 12. Safety Ball

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13. Safety shoes Factorizing the entire operation to safe sequence, efficiency in carefully performing the work for the welfare of group in which the worker attached, you and protection of your own job. Accidents are caused due to following reasons 1. Unsafe Condition 2. Unsafe Act Unsafe Condition: such condition includes leaking gases & unprotects able machines, not furnace, professional hazard, occupational diseases prevailing in the industry. Unsafe act: These accidents happen due to laziness and negligence of the rules while he is on duty

3.1.

General Rules and Safety

1. Be alert on work & do it in attention. 2. Working place path should be clean. 3. Always use safety belt while climbing up ladders. 4. Take help from skilled worker to start machine. 5. Waste dirt should not be scattered in Narrow Street. 6. Scattered thing stored in proper place. 7. Before eating meal, wash hands & clean nail. 8. While working in hot place put on asbestos gloves. 9. Don't store guiding wheel at moisturized place, don't use them at higher than rated speed. 10. Dont pass beyond the chain block or come when heavy loading is being done.

4. HYDRO PLANTThe hydro plant consists 3 main sections namely; The roaster & acid plant The leaching plant The cell house

At the roaster, zinc concentrate from the mines is converted into its oxides and the SO 2 gases from the roasting process are converted to sulphuric acid. The purpose of leaching is to extract maximum zinc from the calcine (ZnO), discharged from the roasting process, into zinc sulphate form and to purify the solution from all other impurities like copper, cobalt, cadmium, arsenic, nickel etc.

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At the cell house, the zinc sulphates containing impurities is treated and zinc is extracted by the process of electrolysis. Zinc sheets thus formed on cathodes are melted and cast into ingots ready for transportation. The total area of the whole plat is 334.85 hectares and the total number of executives in the hydro plant is 322.

Process DescriptionROASTER AND ACID PLANT 5. ROASTER

5.1.

Preliminary production and consumption figures:

All production and consumption figures shown below are based on preliminary process. 5.1.1. Production figures: Calcine: Sulphuric acid (100%) Typical analysis: HP Steam 907 tpd 860 tpd 98.5% H2SO4 47.2 tpd 40 bar 400C Weak acid5.1.2. Consumption figures:

approx. 4-6 m3ph

Zinc concentrates Cooling water Fresh water

nom. 954 tpd 3000 m3ph 10-15 m3ph

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Demineralised water

55 tph

The power consumption for the roasting, gas cleaning and acid plant will be 220 kW/tcath.Zn

5.2. Concentrate StorageThe zinc concentrates from various mines (Rajpura Dariba (RDM), Rampura Agucha(RAM) and Zawar) are delivered by trucks and are discharged into two underground bins. Several belt conveyors transport the concentrate from the underground bins to the concentrate storage blend yard. There, the concentrates are mixed in a required ratio to maintain the zinc percentage. A Pay loader feeds the materials into two hoppers. By means of discharging and transport belt conveyors including an over-belt magnetic separator, a vibrating screen and a hammer mill (which reduces the size of the oversized particles of the vibrating screen to a required size and the material again taken in to the loop), the materials are transported to the concentrate feed bin.

Figure 1: Storage blend yard

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Figure 2: Feed bin and conveyor belt

Dross material from the cathode melting and casting process will be added to the feed material before the vibrating screen. For moistening of the concentrate, several spraying nozzles are foreseen in the concentrate storage hall, as well as on the conveying belt before the concentrate feed bin.

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Roaster & Acid PlantDM WaterConcentrates & Recycles

Steam

Air

Fluo - Solid Roaster

Gases

Waste Heat Boilers Calcine

Waste Gas Cyclones

Hot Gas Precipitator Calcine to Storage/ Leaching Plant Gases Quench tower

Packed tower

Wet ESPs (4 no.) Chlorine Calomel Acid Plant Drying Tower Mercury Removal System

Gases to Stack

Converter (Catalyst Beds)

Absorption Towers Product Acid

Figure 3:flowsheet of roaster and acid plant

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5.3. Material Feeding System and Fluid Bed FurnaceThe roaster is designed to treat concentrates of varying compositions. The produced calcine has the following characteristics: Sulphide sulphur in calcine Sulphate sulphur in calcine approx. 0.3% approx. 1.8%

Blended feed from the concentrate feed bin is discharged onto a discharge belt conveyor, which in turn discharges onto a rotary table feeder.

Figure 4: Feeding to the roaster through belt conveyors The rotary table feeder supplies concentrates to the slinger belts, which directly feed it into the roaster. The slinger belts provide a very soft, equal, and fine distribution of the concentrates in the bed area, and prevent local material deposits and the development of gas zones of varying S02 concentration.

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Figure 5: Slinger belt feeding into the roaster bed To charge the concentrates i.e., before the first start-up, as well as for start-ups after extended shut-downs, the fluid bed furnace and the waste heat boiler have to be preheated. For this purpose, the roaster is equipped with a preheating unit for start-up purposes, which consists of 4 oil burners and 12 oil lances with accessories. The necessary combustion air is taken from the main roaster air fan. The combustion air serves as a carrier medium for the fluid bed as well as a source of oxygen for the predominant reaction, which converts zinc sulphide to zinc oxide and sulphur dioxide.

ZnS + 1.5 O2 -> ZnO + SO2

H = -446 kJ/mol

The fresh concentrate fed into the roaster by slinger belt thus meets a fluidized bed of finegrained roasted material at a temperature of 900C to 975 C consisting mainly of zinc oxide. The combustion air for the roasting process is provided by a high-pressure air fan.

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The reaction in the roaster is strongly exothermic, and the gases leave the roaster with a temperature of approximately 930C - 975C and with an S02 concentration of approximately 10.2% by volume, dry basis. Part of the reaction heat is absorbed by cooling coils installed in the fluid bed, thus cooling the fluid bed by indirect heat transfer. The flexibility needed for the operation of treating concentrates with varying calorific values is provided by the combined direct/indirect cooling of the turbulent layer. A portion of the feed charged into the roaster agglomerates in the bottom of the fluid bed and would result in a continuously increasing pressure loss in the roaster if an appropriate quantity of material were not withdrawn.

Bed material is withdrawn via: The continuous roaster overflow.

The roaster overflow functions by gravity and its barrier rim can be raised or lowered by the insertion of weir plates. The purge device for coarse agglomerates.

The purge-discharging device is operated manually and withdraws the material from the grate level and thus prevents the accumulation of the coarser-sized particles. The operation frequency depends on the formation of coarse agglomerates. The roaster has a cylindrical bed section, a conical intermediate section, a cylindrical enlarged top section, and a grate area of 123 square meters. The enlarged cylindrical section enables a complete roasting of even the finest calcine particles without the occurrence of a secondary combustion phenomenon. For process optimisation, 10 secondary air nozzles are installed to be able to distribute additional roasting air above the bed. A slight draught is maintained at the roaster gas outlet to ensure the safety of the roaster operation.

5.4. Calcine Discharging SystemThe calcine is discharged at four points during normal operation: 1.) Roaster

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2.) Waste heat boiler 3.) Cyclones 4.) Hot electrostatic precipitator

The cyclone and precipitator dust is received relatively cold (300-350C) and sufficiently fine in size, whereas the calcine of the roaster and waste heat boiler requires primary cooling as well as grinding to the size required for leaching. This results in the following arrangement of the calcine handling. Roaster calcine and boiler dust are combined in a common chute and passed to a drum cooler. A water-cooled rotary valve provides the gas seal of the boiler chain conveyor. The cooling air blower cools the boiler chain conveyor. The material temperature at the drum cooler outlet is below 150C. The pre-cooled calcine is transferred into a ball mill via an inclined chain conveyor. This ball mill is designed to achieve the desired grain size, which is 90% below 0.075 mm and 70% below 0.050 mm for the total calcine. The finest dust precipitated in the hot gas ESP is combined with the mill discharge and transferred to the calcine silos via the pneumatic transport system. Screw type compressors provide the air for the pneumatic transport pumps A bag filter is provided to capture fugitive dust from the calcine handling ventilation system. Furnace heating occurs prior to start-up of normal roasting operation with Zn-concentrate. Pre start-up activities contain basically: Grate drying Dry firing of roaster and waste heat boiler Cleaning of boiler Filling of boiler system Feeding of inert material (calcine) and heating up of system Feeding of Zn-concentrate As combustion medium during the above described preheating diesel oil is used. The maximum flow of diesel oil amounts to 3000 kg/h.

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The total duration of first drying, boiler cleaning and preheating takes approx. 3 weeks. The duration of preheating after shut down of the roaster depends on the furnace temperature. If the furnace is cooled down to ambient temperature preheating and restart takes approx. 2-3 days.

5.5. Waste Heat BoilerThe hot dust laden gas stream leaving the roaster is drawn into the waste heat boiler under suction from the SO2 blower. The waste heat boiler is a horizontal-pass boiler, gas-tight welded, membrane wall-type, directly connected with the gas outlet flange of the roaster by means of a flexible fabric expansion joint. In the boiler, the dust-laden gases are cooled down from the roasting temperature to about 350C before entering the dust precipitation system. The waste heat boiler is a forced-circulation-type boiler for the production of superheated steam. The convection heating surfaces of super heaters and evaporators are combined in bundles in a suspended arrangement. The waste heat boiler is equipped with a membrane tubed settling (drop-out) chamber ahead of the front convection bundles. In the settling chamber, part of the dust carried along with the gas is separated. Since the waste heat boiler handles roasting gases having very high dust content, a mechanical rapping device has to be provided. Pneumatic cylinders drive these rappers. Depending on the degree of fouling, the rappers can be actuated by a cylinder controller from a switching cabinet. The pneumatic cylinders are operated by compressed air, which can be taken from the plant air system. The gas-flow velocity through the tube banks was designed to be very low to avoid erosion. The tube banks can be easily removed for maintenance after the plant has been taken out of operation. The rapping device is automatically actuated at certain time intervals. The dust separating out in the boiler is collected in a chain conveyor and fed to the rotary drum cooler. The combined system of cooling coils in the roaster, superheated tube bundles, evaporator tube bundles, and

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membrane wall casing is designed for the maximum load of the boiler. The boiler produces steam in a forced circulation system and is equipped with two circulating pumps, one motordriven and one turbine-driven. The stand-by steam-driven circulating pump will start automatically when the electric power supply fails or when the flow of circulating water falls below a preset quantity. A pressure relief system is included to exhaust steam directly to the atmosphere via a noise damper in the event of curtailed steam usage in the leaching plant. The steam relief system is designed for the full waste heat boiler production of 49 metric tons per hour. The level-control valve installed in the incoming demineralised water line controls the feed water tank level. The demineralised water is deaerated in the deaerator on top of the feed water tank. Deaeration is accomplished by means of steam from the saturated steam line. The feed water tank pressure is maintained by the pressure control valve. The deaerated feed water is preheated and fed to the steam drum via the feed water pumps, one motor-driven and one steam-driven. The steam drum level is controlled using a three-element control system. An additive preparation and dosing station for the boiler feedwater is included in the system. Cooled gases leaving the waste heat boiler flow into the hot electrostatic precipitator (ESP) for final dust removal.

5.6. Hot Gas CleaningHot gas cleaning comprises of: two hot gas cyclones for roaster gas pre-dedusting one single line three field hot ESP

5.6.1. CyclonesThe cooled and dust loaded gas enters the two parallel cyclones for pre-dedusting with a temperature of approx. 350 C. The gas leaves the cyclones at the top whereas the dust is

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collected in the lower part of the cyclones and removed via rotary valves. Final dedusting of the hot gas is achieved in the hot ESP.

5.6.2. Hot Gas Electrostatic PrecipitatorThe gas leaving the cyclones enters a three field hot gas ESP. The ESP consists of the discharge electrodes, the collecting electrodes, gas distribution walls, casing, roof, hoppers, horizontal inlet and outlet nozzles, pressure relief system, rapping systems, sealing air system for the insulators with electric heater and transformer rectifiers with control cabinet for the electrostatic fields. In this system the dust particles are being charged up so that they can stick to the collecting electrodes. The precipitator is insulated. The collected dust is removed from the ESP via the chain conveyor and the rotary valves. Rapping systems are installed at the gas distribution plates in the inlet cone of the precipitator and at the discharge and collecting electrodes. At their bottom end, the collecting electrodes run through rapping bars, so that the rap is affected at the lower side end in the plate plane. A hammer shaft rotates at the end of each electrostatic field, lifting the rapping hammers which drop down in a free fall when the vertical position is exceeded. The acceleration amounts to more than 200 g (200 x 9.81 m/s2) at the total collecting electrode area. During start-up and shut-down the gas temperature in the precipitator can fall below the dew point. To prevent condensation on the insulator a heating system is installed.

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Figure 7: Roaster plant: A) air blower, B) roaster bed, C) waste heat boiler, Hot gas cleaning section: a) cyclones, b) hot gas precipitator

5.7. Fuel Oil SupplyThe fuel oil supply for heating up of the roasting and acid plant is provided by a fuel oil storage tank. The capacity of the tank with 100 m is designed for one start-up procedure from cold conditions.

5.8. Wet Gas Cleaning SystemThe gas cleaning system (gas washing and cooling section) described here is installed for purification of SO2-Gas from a Zinc roaster. The SO2-gas shall be processed to sulphuric acid. To allow the production of sulphuric acid, the SO2-gas must be cleaned (removal of dust, aerosols and unwanted gaseous compound) and water vapor must be removed (condensed). This is achieved by the application of a multistage process. In the first step, the SO2-gas is adiabatically cooled (quenched) and partly cleaned in a scrubber. Then the water vapor in the gas is condensed in a packed gas cooling tower. The packed gas

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cooling tower is also used for halogenide removal. In the next stage, the SO2-gas is demisted in wet electrostatic precipitators. In the last cleaning step, the gaseous mercury is removed.

Figure 8: Wet gas cleaning section

5.8.1. Quench with settling tank and stripperIn the quench tower, the hot gas is cooled by the evaporation of water. The heat of the incoming gas (Temperature: > 300C) is used for the evaporation of water that is sprayed into the Quench Tower. The sensitive heat of the gas is converted into water vapor (latent heat). This type of cooling can be considered as an adiabatic process. Adiabatic means, the process step is operated without energy exchange with the environment. But besides this quenching, also a part of the dust and condensable impurities in the gas will be scrubbed in the quench tower. At the outlet of the tower, the gas contains water vapor. If the temperature is lowered, water vapor will condense. The Quench Tower is designed as counter current flow type quencher. The gas inlet is at the bottom part of the casing. The gas outlet is at the top of the quench tower.

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The liquid is sprayed into the quench tower in counter-current flow to the gas. A part of the spray does evaporate, but the biggest portion will be collected in the lower part of the tower which does serve as pump tank. A side stream of the spray circuits is guided through a settling tank for removal of suspended solids. Excess liquid from the washing and cooling system is discharged from the quench tower circuit via strippers.

5.8.2. Weak Acid BleedThe weak acid bleed which will be handled in the effluent treatment plant (by client) contains impurities and SO3/H2SO4, which have been removed from the process gas. In order to ensure a correct and reliable operation of the wet gas cleaning system, the concentration of these impurities in the weak acid bleed should not exceed certain limits. According to our experience following values of impurities should not be exceeded: Acid concentration: Solids: Chlorides Fluorides: < 6-7 g/l < 5 g/l Na2(Fe6(SO4)4(OH)12) + 6 H2SO4 To keep the free acidity at the desired 8-10 g/l of free H2SO4, additional calcine is added into the third jarosite tank. The addition of this calcine is done from the calcine bin via the weighing belt conveyor. The slurry from the magnesium removal plant (vacuum belt filter cake) containing basic zinc sulphate and gypsum crystals is added to the forth jarosite tank. The basic zinc sulphate will help to neutralize the jarosite solution whereas the gypsum will remain as a solid and end up in the jarosite cake. From time to time cadmium free zinc bearing solution is recycled from the cadmium plant to the leaching plant. This solution, which is pumped over in batches, is recycled to the first jarosite tank. After a retention time of approximately 15 hours at the above mentioned leaching conditions, 90% of the incoming dissolved iron will have precipitated as jarosite. The

suspension from the last jarosite tank will flow via the launder to the separation thickener for solid liquid separation. To improve the solid liquid separation flocculent solution is added to the thickener feed launder. The separation thickener flow over with a free acid content of 8 - 10 g/l and an iron content of 2 g/l is collected in the over flow tank from where it is then pumped to the first tank of the pre-neutralization step via the level controlled pumps. A small flow controlled bleed stream of this solution is sent to the magnesium removal plant for cake repulping. The thickener under flow is pumped directly from the thickener under flow cone to the feed launder of the jarosite wash thickener. To improve and accelerate the jarosite formation, a manually adjusted small thickener under flow stream is recycled to the first jarosite tank. These solids will act as seed material accelerating the jarosite formation. Diluted filtrate from the jarosite filtration section is also added to the wash thickener feed launder to dilute the zinc content of the incoming liquor of the jarosite slurry. As in the other thickeners a diluted flocculent solution is added to this jarosite wash thickener feed steam to improve solid sedimentation. The wash thickener is arranged at a higher level then the separation thickener. The overflow of this wash thickener can therefore flow by gravity via the launder directly to the centre of the separation thickener where it is mixed with the suspension from the jarosite tanks.

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The jarosite slurry collected in the wash thickener underflow cone is pumped with speed controlled thickener underflow pumps directly to the feeding box of the two horizontal vacuum belt filters. The operator shall always maintain a constant slurry flow with a high and constant solid content in the thickener underflow, by manually adjusting the speed pump. Variations in solid and or slurry flow will disturb and complicate the operation of the jarosite vacuum belt filters.

7.6. Pre Neutralisation (PN)The pre-neutralisation is a leaching plant section to neutralize and pre-purify the jarosite thickener overflow solution. The purification of this solution stream will considerably reduce the impurity load on the neutral leaching section thus improving operational safety considerably. This plant section comprises of the following main equipment: Two 200 m leaching tanks One 21 m thickener One 14 m underflow tank One 13 m overflow tank

The jarosite thickener overflow solution containing approx. 2 g/l of iron, 15 g/l of free acid and all the remaining impurities, which were not precipitated together with the jarosite, is pumped with the jarosite thickener overflow pumps via a flow control valve to the first preneutralization tank. The pre-neutralisation leach tanks are arranged in cascade and are connected with an overflow launder, so that the solution fed to the first tank, can flow by gravity through the leaching tanks into the thickener without the need of pumps. The calcine fed into the first pre-neutralization tank is extracted from the calcine storage bin via rotary valve, dosing belt weigher and screw conveyor. The calcine flow will be manually set by the operator on the calcine flow controller is such a way that the final acidity in the pre-neutralization thickener overflow stabilizes at pH of 4.8 to 5.0. Manual adjustments to the calcine flow shall be done following the pH indicator installed between the two pre-neutralization tanks. At this final pH all the dissolved ferric iron will precipitate as iron hydroxide Fe(OH)3, co-precipitating and absorbing impurities like As, Sb, Ge, Al, etc., thus acting as an important purification agent. The main chemical reactions will be:

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ZnO

+ H2SO4 ZnSO4

+ H2O

All the precipitated iron hydroxides and the neutral leaching residues from the calcine added into this step will be separated from the main stream in the pre-neutralization a thickener. Diluted flocculent solution is added to the thickener feed stream to improve the solid flocculation and settling speed. These residues will be treated in the HAL I & II to recover the zinc from the zinc ferrites. The thickener underflow slurry is pumped by the variable speed driven thickener underflow pumps at a constant rate from the thickener underflow tank to the first tank of the hot acid leaching section. The purification of neutral leach solution is necessary because this solution contains copper, cadmium, cobalt, and nickel as major impurities and also small amounts of arsenic and antimony, which enhances or impeded the electrolytic winning of zinc. As far as these impurities have not been completely removed during the ferric hydroxide purification in the neutral leaching plant. The purification is carried out by addition of zinc dust. The basic reaction is that of electrolytic reduction of those metals, whose positions in the electromotive series for sulphate are below that of zinc: CdSO4 + Zn0 ZnSO4 + Cd0 CoSO4 + Zn0 ZnSO4 + Co0 CuSO4 + Zn0 ZnSO4 + Cu0

Zinc metal tends to protect itself against corrosion by forming of an inert zinc oxide film. Any factor, which tends to dissolve the oxide film, will cause the zinc dust to become more active. For that reason, copper in case of need, and antimony will added as activators in order to increase the activity of the zinc dust and speed up the precipitation of the impurities. The purification of neutral solution will be carried out in three steps: First step or cold purification for the removing of copper and cadmium.

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Second step or hot purification for removing of cobalt and nickel as guide impurities.

Third step or polishing step to ensure top quality of purified solutionFor all the three purification steps one big elevated zinc dust bin has been provided. This

zinc dust bin is located above all the purifications tanks in such a way that zinc dust can be drawn from this bin via steep inclined pipe chutes to the individual zinc dust dosing equipment installed on all the main purification tanks. The zinc dust flows from the zinc dust bin to the dosing units is by gravity. This zinc dust bin is internally divided into two compartment, one for coarse and one for fine zinc dust. Filling of this zinc dust bin will be accomplished by two pneumatic operated zinc dust transport lines which will discharge the fine and coarse zinc dust into the corresponding bin compartment. Zinc dust transport air will be vented to the atmosphere via a bag house installed on top of the zinc dust bin.

7.7. Jarosite Filtration (JF)In the jarosite filtration section the jarosite slurry is filtered and washed on two horizontal vacuum belt filters to maximize water-soluble zinc recovery. The solids from the jarosite wash thickener underflow are pumped via to the vacuum belt filters and, where the supplied slurry is separated into filter cake (moisture content 35 - 45%) and the mother liquor. The vacuum belt filters are parallel arranged. The operator will manually control the speed of the thickener under flow pumps in such a way as to obtain a continuous and steady slurry flow with a constant solid content. To minimize the soluble zinc content in the final jarosite, the jarosite cake is washed on both filters on two in counter current arranged washing steps. The expected water-soluble zinc content in the dry jarosite cake can be reduced to 0,3 % with a wash water ratio of 1,4 m wash water per ton of dry cake. This wash water is added in counter current to the cake flow. For proper vacuum control each horizontal belt filter will be equipped with its own water-ring type vacuum pump system. The cake discharge from the filter is transported to the repulping tank via a screw conveyor where it is mixed with a constant flow of jarosite-pond water to obtain a diluted suspension of solids.

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Figure14: Horizontal bed filter

This suspension (150 g/l solids) is then pumped with the pumps to the jarosite pond. The pump operation will be of the stop & go type, controlled by the level contacts of the level probe. The mother liquor (filtrate) containing all the water-soluble zinc is collected in the filtrate tank from where it is pumped with the level controlled variable speed filtrate pumps to the feed launder of the jarosite wash thickener. This filtrate will mix with the jarosite separation thickener underflow slurry thus diluting the zinc content in this launder feed suspensions.

7.8. Cadmium Plant (CD)The cadmium plant is designed to recover the zinc from the hot and polishing purification. The cakes from hot and polishing step is collected CD-01 tank , where it is agitated for leaching and overflow of the tank passes through launder to CD-02 and then CD-03. Then it is pumped to filter press. There are two filter presses, the filtrate of the cadmium plant is sent to Jarosite section and the discharged cake is being sent to existing pyro plant.

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7.9. Magnesium Removal SectionThe magnesium removal plant is required to maintain a magnesium tenor at 10 g/l Mg in process solutions. For the separation of Zn from the Mg lime milk is used. The lime milk solution is prepared in the lime milk tank. The Ca(OH)2 is fed from a lime bin via a screw conveyor into this tank. Into the first precipitation tank the spent electrolyte with 10 g/l magnesium is fed. The lime milk is transported over a ring line with two branching off for the precipitation tanks. The two precipitation tanks are arranged in cascade and connected with a launder. The neutralization process is continuous and dimensioned for about one and half hours retention time. Reactors, where lime slurry and bleed are mixed, have pH control. In these reactors pH is 7.5 7.8. Zinc is precipitated together with gypsum as basic zinc hydroxide. The lime feed is arranged by such a way that the pH is 7.0 in the first neutralization reactor and adjusted to its final value, 7.8 in the second one. If the pH rises between 8 and 9 magnesium begins to precipitate which is not a desired situation. The following curves show solubility of metal hydroxides depending on pH. In pH 8 Zn is almost totally precipitated and Mg has not started to precipitate. The zinc concentration will be below 10 mg/l after neutralization. Samples will be taken and analysed once/shift and correction in lime feed made if too much zinc is going trough. The theoretical data about dissolved zinc vs. pH are only suggestive since the process cannot be in balance because of limited retention times in the process. Additionally the pH measurements may creep in the process. ZnSO4 + Ca(OH)2 + 2 H2O -> Zn(OH)2 + CaSO4 2 H2O MgSO4 + Ca(OH)2 + 2 H2O -> Mg(OH)2 + CaSO4 2 H2O H2SO4 + Ca(OH)2 -> 2 H2O + CaSO4 2 H2O

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0.90.8 Metal Content (g/l) 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 6 7 8 pH Value9 10 11Zn Cd Mn Mg

Figure 15: Solubility of Metal Hydroxides

The solution flows over through the two precipitation tanks into a launder and after that into the thickener. In addition to the reactor fluid, the filtrate from the band filter is fed into the launder. The precipitate of the Mg removal is settled easily. However, flocculent will be fed according to the amount of solids in the launder. The flocculent dosage is determined according to solid material in the thickener. The overflow will be directed to the overflow tank from where it is pumped to the Effluent Treatment Plant. The thickener underflow is pumped to a vacuum belt filter where it is filtrated. The filtrate of the vacuum belt filter is sent back to the launder, while the filter cake is sent to the gypsum repulper tank. The filter cake with 40 - 45% moisture is mixed in the gypsum pulper with a solution from the thickener overflow of the jarosite precipitation step and after that pumped to the leaching tank in the jarosite precipitation step.

Process disturbances and correction measures:

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A short term Zn peak will attenuate in the thickener. If the peak is long term unnecessary amount of zinc will get to the effluent treatment. In this case the pH measurement shall be checked and the pH of the first neutralization tank risen.

In case the pH in the tank 2 is low, Mg has also precipitated and lime consumption has been unnecessary high. The pH measurements shall be checked and instruments cleaned and repaired.

In case the thickener overflow is not clear or the precipitate level in the thickener is rising, the flocculent dosage has been too low. The most probable reason, however to the rising precipitate level and high torque in the rake is too low underflow take off.

If the filtrate is not clear there are holes in the filter cloth

8. Purification Plant8.1. Cold Purification (PC) (Presently out of line)The three purification tanks, which are arranged in cascade, are interconnected by an overflow launder. Each tank is covered and equipped with an agitator and a forced ventilation chimney. The un-purified neutral solution is pumped from the 350 m neutral leach thickener overflow tank of the neutral leaching section via one of two flow controlled pumps into the first cold purification tank. The optimum temperature for the cold purification is approximately 60 - 70C, thus no heating or cooling of un-purified solution is required. Zinc dust addition is done continuously via the dosing belt conveyors. The amount of zinc dust fed into tanks depends on the Cu- and Cdcontent of the un-purified solution. At nominal solution flow (225 m/h) the zinc dust consumption will be approximately 360 - 450 kg/h. To achieve good cadmium and copper cementation, the pH in the overflow of the first tank of the cascade must be maintained 4.8 (20C). The control of the pH is then done manually by increasing or decreasing the spent

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electrolyte addition into tank. The second cold purification tank is also equipped with a zinc dust and spent electrolyte addition system for final cadmium control and pH-adjustment. From the last tank of the purification cascade the solution containing the cemented cadmium and copper as well as some excess of zinc dust is pumped to the four parallel working filter presses for separation of the above mentioned solids from the now Cd- and Cu-free zinc sulphate solutions. Three filter presses are normally in operation; the fourth one is in cleaning cycle or as stand-by for operation. When a cleaned filter press is taken into operation, the filtrate must be recirculated into tank until the filtrate is absolutely clear, i.e. no solids are passing the filter press. Once the filtrate is clean, it is sent to the filtrate collecting tank. From there the solution is pumped to the hot purification step. During filter press-cleaning operation the Cu-Cd-filter press cake will be discharged onto a screw conveyor located beneath each filter press. This screw conveyor will then move the cake to a collecting chain conveyor which will then transport the cake into the first of three in cascade arranged cadmium and zinc leaching tanks of the Cd-plant. Solution drippings from the operating filter press and from filter cloth wash water will flow through the same screw and chain conveyor to the cadmium plant tank Presently cold purification is out of stream, there is no addition of zinc dust in the reaction tanks, only the neutral overflow is being circulated and cleaned through filter presses.

8.2. Hot Purification (PH)Cobalt and nickel as well as traces of antimony and arsenic are the main impurities that will be removed in the hot purification step. This hot purification step is based on the antimony purification process. The hot purification section consists of the following main equipment: Two 85 m spiral heat exchangers. Two 17 m reagent preparation tanks for PAT. Two 5 m reagent preparation tanks for CuSO4. Five 150 m purification tanks Three 0.18 m zinc dust bins with 400 mm zinc dust dosing belts.

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Five 120 m chamber filter presses. One 20 m condensate tank.

The five purification tanks are arranged in the same way as in the cold purification section. The tanks are also equipped in the same way as in the cold purification section except for steam heating coils in the first four tanks, which are required to keep solution temperature constant during stops and start-ups. The zinc sulphate solution, which has been purified for Cu and Cd is pumped with the speed controlled pumps from the filtrate tank through the spiral heat exchangers into the first hot purification tank. The heat exchangers, which are connected parallel, will automatically heat up the incoming solution to a constant temperature of 87C.

Main cobalt and nickel purification reagent is zinc dust, which is dosified into the first hot purification tank via the zinc dust dosing belt. The amount of zinc dust can be manually adjusted to the required flow, which at nominal capacity will be approximately 150 - 200 kg/h. To improve the reactivity of the zinc dust, copper sulphate and potassium antimony tartrate (PAT) must be added. The amount of copper and antimony added to the first hot purification tank shall be such as to obtain a copper and antimony concentration of 30 to 40 ppm and 0.5 to 1.0 ppm respectively. Copper sulphate and antimony PAT will be mixed with water in the reagent preparation and dosifying tanks at a concentration of 40 g/l for copper and 1 g/l for antimony. This Cu and Sb solution is then pumped into the first hot purification tank at a rate of approximately 0,7 m/h PAT-solution and 0.18 m/h cupper sulphate at a purified solution flow of 226,6 m/h. The optimum pH for Co- and Ni-cementation is pH 5.0 (20C). The overflow solution from tank flows via a launder through the tanks into the tank, from where it is pumped to six chamber filter presses for separation of cemented Co, Ni and excess of zinc dust from the now purified neutral zinc sulphate solution. The tanks and are also equipped with zinc dust-dosing belts and spent electrolyte addition as well as online pH meters for final Co- and Ni-control. The filter presses of the hot purification are of the same type as of the filter presses from the cold purification. The cake from the hot purification filter presses contains a big amount of cupper and cobalt is therefore sent to cadmium recovery plant. The copper cake is directly

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discharged from the filter press via a conveyor in to cadmium plant. The final solution quality check is done from the filter press filtrate, which if solid free, is collected in the first purification tank of the polishing step. If solids are detected in the filtrate it must be returned to the last hot purification tank, until it is solid free.

8.3. Polishing Step (PS)The polishing step is a safety and quality insurance purification process step. Mainly cadmium that may have slipped through in the two prior purification steps will be definitely be removed in this purification step. The two purification tanks, which are arranged in cascade, are interconnected by an overflow launder, thus permitting the solution to flow through the tanks without the need of pumps. The first tank is equipped with a temperature indicator and with an online pH meter, the last tank which is also a pumping tank is equipped with a local level indicator. The pre purified solution (filtrate from the five hot purification filter presses) flows to the first polishing step tank by gravity. The process temperature for the polishing step is approximately will stabilize at approximately 75-80C. No heating or cooling of the solution is required. As in he other purification steps, zinc dust continuously added into the first tank via the dosing belt conveyors. The amount of zinc dust, which is fed into the tank, depends on the remaining cupper- and cadmium-content of the solution after the hot purification. At nominal solution flow (228 m/h) the zinc dust addition will be approximately 80 - 150 kg/h. To achieve good cadmium and copper cementation, the pH in the overflow of the first tank of the cascade must be maintained 5.1 (20C). From the second tank of the polishing step the solution containing the cemented cadmium and copper as well as some excess of zinc dust is pumped to the five parallel working filter presses for separation of the above mentioned solids from the now fully purified zinc sulphate solutions. Four filter presses are normally in operation; the fifth one is in cleaning cycle or as standby for operation. When a cleaned filter press is taken into operation, the filtrate must be recirculated into tank until the filtrate is absolutely clear, i.e. no solids are passing the filter press. Once the filtrate is clean, it is sent to the filtrate tank. Final solution quality check is done in this

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tank. If the analysis indicates an impurity level equal or below the following standards, Co 0.2 ppm, Ni 0.05 ppm, As + Sb 0.04 ppm, the solution is pumped to the cooling towers of the gypsum removal plant. The cake collected in the polishing filter presses will mainly consist of zinc dust and some amounts of cadmium and copper. During filter-press cleaning operation the Zn-Cu-Cdfilter press cake will be discharged onto a screw conveyor located beneath each filter press. This screw conveyor will then move the cake to a collecting chain conveyor, which will then transport the cake into the second of three in cascade arranged zinc and cadmium leaching tanks of the Cdplant. Solution drippings from the operating filter press and from filter cloth wash water will flow through the same screw and chain conveyor to the cadmium plant tank.

8.4. Enrichment PlantThe enrichment plant is designed to recover as much as possible of the zinc from the hot purification filter press cake and to keep all other unwanted impurities in the cake. The amount of treated cake will depend on the impurities content of the calcine leached in the leaching section. The enrichment plant can be operated continuously or as a batch process. The enrichment plant consists of following main equipment: o Four in cascade arranged leaching tanks o One NaOH solution storage tank o Four filter presses o One filtrate tank The four enrichment plant tanks EP_02 C005 - EP_02 C008, which are arranged in cascade, are interconnected by an overflow launder EP_02 W001, thus permitting the solution to flow through the tanks without the need of pumps. Each tank is covered and equipped with an agitator and a forced ventilation system. All tanks have following inlets: o Spent electrolyte o Steam o Slurry from the hot purification slurry tank o NaOH-solution o Process water

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o Oxygen The oxygen and spent electrolyte addition to the tanks is flow controlled and can be adjusted in the control room. Every tank is equipped with a pH-indicator. The NaOH-addition shall only be used for emergency reasons. All tanks are connected by an outlet at the bottom of the tank to the centrifugal pumps EP_02 G010 and EP_02 G011. The possible chemical reactions in the enrichment plant are: Zn + H2SO4 + O2(g) ZnSO4 + H2O Zn + H2SO4 ZnSO4 + H2(g) Cd + H2SO4 + O2(g) CdSO4 + H2O Cd + H2SO4 CdSO4 + H2(g) Co + H2SO4 + O2(g) CoSO4 + H2O Co + H2SO4 CoSO4 + H2(g) Ni + H2SO4 + O2(g) NiSO4 + H2O Ni + H2SO4 NiSO4 + H2(g) Cu + H2SO4 + O2(g) CuSO4 + H2O Cu + H2SO4 CuSO4 + H2(g) The oxygen addition shall oxidize the metals but it is also possible that the elements will be leached with the sulphuric acid and producing hydrogen. Hydrogen is generated by contact of metals with dilute sulphuric acid. Zinc sulphate is formed in solution and the hydrogen is produced as unwanted by-product. a mixture of hydrogen with oxygen is highly explosive. Dont add oxygen into the tank while free acid is in the same time in the tank. To avoid any explosion add only oxygen into a neutral solution and wait 10 Minutes before starting the spent addition. All the time the ventilation system over the stack must be in operation. The reactions already show the main components in the hot purification cake. The concentrations and the arrangement of the metals in the electromotive series shows the following table. Element E 25C [V] Mass.-% 2+ 1. Zn /Zn - 0,763 60 - 75 2. Cd2+/Cd - 0,400 15 25 2+ 3. Co /Co - 0,283 0,1 - 0,5 2+ 4. Ni /Ni - 0,236 0,1 - 0,5 5. Cu2+/Cu + 0,345 7 12 Tab. 1: Electromotive series and HP cake composition The electromotive series shows that if all impurities would have the same concentration the zinc metal would be leached first, next cadmium and at least copper. Beside the electromotive voltage also the concentration of the elements in the cake has an impact on the leaching sequence. The leaching process of the metals is overlapping each other. The following figure shows qualitatively the leaching sequence of the above shown elements versus time. At the beginning zinc is leached. While the zinc is leached, the zinc concentration in the cake decreases and the acid finds more and more cadmium in higher concentration for the leaching reaction. For cobalt and nickel the concentration and the voltage are similar. Thus the leaching reaction starts nearly at the same time. The last element, which will be leached, is copper. The purpose of the enrichment plant is to leach as much as possible of the zinc in the hot purification AND to avoid the re-leaching of the unwanted impurities. The conditions show that the leaching process has to

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be observed very carefully and the process parameters have to be checked all the time to avoid the re-leaching of the impurities in the filter cake.

Figure 15: Qualitative leaching sequence in enrichment plant The pH in the enrichment plant tanks should be in the range of 3,5 - 4,5 (at 20C). Below 3,5 the reaction velocity increases rapidly and beside the Zn also Cd would be leached very fast. If in one tank the pH drops below 3,5 than it is possible to add some NaOH from the tank EP_02 C028. A pH higher than 4,5 would decrease the leaching velocity and could produce precipitates in form of hydroxides. For a good process control with approximately pH 4 - 4,5 gives the operator the best possibility to control the process. By leaching as much as possible of the zinc metal and in the same time to avoid the leaching of cadmium and the other impurities. This however causes a high retention time. The leaching process should be stopped as soon as the cadmium of cake is leached. The start of the Cd-leaching is shown when the cadmium concentration in the solution increases. In that moment the spent electrolyte addition should be stopped immediately and the suspension should be sent to the filter. The following table shows the process parameters for the enrichment plant tanks: o pH: 3,5 - 4,5 (never go below 3,5, exceeding 4,5 is allowed for a short time) o Temperature: 50 - 70C o Solid content: 30 - 100 g/l (it is possible to increase the solid content up to 200 g/l but not recommendable) o Retention time: 1 - 14 h Depending on the amount of filter cake, the solid content in the suspension and the needed retention time, the process can be operated continuously or as a batch process. For the continuous operation up to four tanks are used in cascade. For the batch process the tanks are used in parallel. All tanks can be used as pump tank, which gives the operator the possibility to send the solution from every tank to the filters.

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For the preparation of the suspension in the slurry tank PH_02 C017 following solutions can be used: o Cleaning water from the Hot Purification filters o Suspension from the sumps in the Purification plant. Dont use the sump of the acid corner of the purification, where also the solution from the cloth and plate washing is added. o Recycling of the filtrate from the Enrichment plant filters o Process water Before filling any filter cake into the slurry tank PH_02 C017 it must be ensured that the mixer is more than only covered by solution. Otherwise the cake could damage the agitator. The pH in the slurry tank should never become lower than 3,5 to avoid any leaching reaction in this tank. Under normal conditions the above-mentioned solutions should have following pH ranges: Cleaning water of filters pH = 5,0; suspension from the sumps in purification pH = 4,8 - 7,0; recycling of the filtrate from the enrichment plant filters pH = 4,0 - 4,5, process water pH = 5,5 8. This mixture finally should give a pH value of approximately 4,5 - 7,0. After the leaching step the suspension is sent via pumps to the filters. The level of the purification tanks are controlled by means of suspension discharge. Controlling the speed of the centrifugal pumps EP_02 G010 and EP_02 G011 regulates the discharge flow rate. High level and low level will generate only an alarm when activated. Low low level stops the pumps EP_02 G010 or EP_02 G011 for rundry protection. After the filter the solution is collected in the filtrate tank EP_02 C030. The level of the filtrate tank is controlled by means of suspension discharge. Controlling the speed of the centrifugal pumps EP_02 G032 and EP_02 G033 regulates the discharge flow rate. High level and low level will generate only an alarm when activated. The low low level stops the discharge pumps EP_02 G032 and EP_02 G033 for run-dry protection. The solution in the filtrate tanks can be sent to following destinations: slurry tank in the hot purification (PH_02 C017); conversion process (CN_02 C001) or enrichment plant tanks (EP_02 W001). The flow is measured in the supplying line and is adjusted by means of the controller and the speed of the centrifugal pumps EP_02 G032 and EP_02 G033. The controller will adjust the control valve position to achieve the desired flow. The flow ratio to the flow measurements will be adjusted in the DCS. The next chapters will describe how to run the plant continuously or as a batch process.

9. Cell house Process Description9.1. Gypsum Removal (GR) The gypsum removal system will be necessary to remove gypsum from hot neutral solution before it is taken to the cell house in order to reduce gypsum precipitation in electrolytic cells, piping, launders and cooling towers. The neutral solution that is saturated with gypsum will

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be cooled in three atmospheric cooling towers from 86C to 34C. This causes crystallization of gypsum from the solution still remains saturated with gypsum. The gypsum will be then removed in a thickener. Spent acid will be fed for pH adjustment and flocculent (1 g/l aqueous solution) into the thickener. The thickener overflow will be taken to the purified solution storage tanks. The underflow will be pumped to the jarosite step. Prior to be directed to the cooling towers the pH of the solution will be adjusted to 4.9 to prevent formation of basic zinc sulphates. The pH adjustment is made in the filtrate collecting tank of the polishing purification step by adding a controlled amount of spent electrolyte. The solution is fed to the top of the tank through nozzles. The falling solution meets the air produced by the fan and solution will cool down when water is evaporated. The cooled solution is collected on the bottom of the tower and leaves the tower trough an overflow box, which is provided with temperature control and level detection The overflow from the thickener flows by gravity via the launder to the selected purified solution storage tank. In this whole process, a part of gypsum, about 157 kg/h is removed from the solution.

9.2.

Electrolyte storage (ES) For the sake of storage of electrolyte four-solution storage tanks have been provided, two

for purified solution and two for spent electrolyte. Each of these tanks has a holding capacity of 1500 m. All four tanks are equipped with a cover to avoid solution contamination and dilution during the rainy season. 9.3. Cell house Electrolyte Circuit I & II (EC) In the tank house zinc form the purified solution is deposited as metallic zinc on the aluminium cathodes. This cathode zinc is then removed from the cathodes and sent to the melting and casting plant where the cathodes are melted and cast to SHG/HG zinc ingots. The cell house consists of the following main plant sections and or equipment:

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2 electrolyte circulation systems consisting of:o 124 electrolytic cells, each equipped with 114 aluminum cathodes 115 lead silver anodes 1 water cooled intermediate bus bar

2-electrolyte return launders systems (one for each cell row). 2 concrete electrolyte circulation tanks. 12 atmospheric cooling towers. 2 electrolyte feed launder systems (one for each cell row). 2 transformer rectifiers with the corresponding bus bar system. Electrode handling system consisting of: o 2 cathode stripping machines o 2 stripping cranes o 1 anode cleaning and flattening machine

Reagent preparation station Cell cleaning system

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Fig. 16: Cell house, the electrolytic cells Warm spent electrolyte (38C) overflowing from the cells belonging to one cell row is collected in the electrolyte return launder. This spent electrolyte (50 g/l Zn and 180 g/l H2SO4) flows by gravity to the circulation tank. A controlled amount of purified neutral solution is continuously added to the circulation tank to raise the zinc content in the electrolyte to 55 g/l. The flow of the added purified solution will be adjusted on the automatic flow control valve according to the actual cathode zinc production. A level probe installed in this circulation tank controls the amount of spent electrolyte withdrawn from this electrolyte circuit. This level control will keep the electrolyte level constant at a preset level. The empty volume maintained in the circulation tank with this level control is required to absorb backflow of electrolyte in case of a general power failure.

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Figure 17: flowsheet of cell house

Consumption figures:

Ammonium Chloride

2 kg/t Zn

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Sr CO3 Animal glue Crecilic Acid Natural Gas

3 kg/t Zn 3 kg/t Zn 100 kg/t Zn 100 kg/t Zn

The power consumption for the tank house will be 3175 kW/tcath.Zn

9.4.

Electrolyte cooling To cool down the enriched electrolyte to cell feed temperature of 34C, Cooling is

archived by evaporating water from the warm electrolyte in the atmospheric cooling towers. This is accomplished by passing atmospheric air through the cooling tower in counter current to the warm electrolyte. 9.5. Cell feeding system The cooled electrolyte will leave the cooling tower basin via 2 solution siphons which discharge the electrolyte into 2 small launders. The siphons prevent acid mist from escaping to the atmosphere. These launders, 2 per cooling tower totalling 12 per electrolyte circulation circuit, do all discharge into the electrolyte collecting feed launder. These 12 small launders are evenly distributed over the total length of the electrolyte collecting feed launder, implying a very small axial flow velocity of the electrolyte in the collecting feed launder. This low velocity will guarantee an even electrolyte overflow stream to all and each of the 62 cells.

9.6.

Zinc electro winning The recovery of metallic zinc by electrolysis is accomplished by the application of a

direct electrical current through insoluble the lead-silver anodes, the electrolyte to the aluminium cathodes, resulting in a decomposition of the aqueous zinc sulphate electrolyte, the deposition of Zn++ at the cathode and the deposition of O2 at the anode. All the electrolytic cells (124) are electrically connected in series, whereas the electrodes (anodes & cathodes) of each cell are connected in parallel

Dissociated elements:

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ZnSO 4 SO 2 Zn 2 4 SO 2 H2O H2SO 4 O2 4

Reaction ions: Zn2+ + 2e- Zn

General formula: ZnSO4 + H2O H2SO4 + Zn + O2 The oxygen, which is liberated at the anode, will oxidize Mn-ions from the electrolyte to MnO2. MnSO4 + O2 + H2O MnO2 + H2SO4 This manganese dioxide will deposit as solid chips on the anodes and must be removed from the anodes every 30 days to avoid short circuits between the electrodes. The electrochemical process will heat up the electrolyte flowing through the cells by 4 to 6C depending on the current density The main design and operating data of the cell house are: Number of cells Current setting Current density Current efficiency Stripping cycle Delta Zn of electrolyte Spent electrolyte 124 cells 160 KA 400 A/m(design 480 A/m) 90 % 48 h 5 g/l Zn 50 g/l Zn 180 g/l H2SO4 38C

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All these contact, 114 cathodes of one cell and 115 anodes of the adjacent cell will rest on the intermediate bus bar. To avoid overheating of these intermediate cell bus bars and to increase its lifetime, a bus bar cooling system is provided. This cooling system consists of a closed cooling water circuit, which provides full de-mineralised cooling water to all the intermediate bus bars.. The collected warm de-mineralised cooling water is re-cooled to the required temperature in a de-mineralised cooling water heat exchanger and then to the cold demineralised water manifold.

9.7.

Cell cleaning During the electro winning process some solids will be generated on the anode, which

will settle in the cell bottom. These solids will mainly consist of MnO2, CaSO4 * H2O and or other precipitated impurities such as PbSO4, PbCO3, SrSO4, SrCO3. Sufficient free space has been provided between cell bottom and the lower edge of the electrodes in a cell to accumulate a certain amount of cell slurry, however this slurry must be removed from time to time to prevent electrical short circuit between anodes and cathodes, which would destroy the anodes and contaminate the cathode zinc.

9.8.

Anode cleaning As already mentioned above, MnO2 and some gypsum will deposit on the anode surface

during the electro winning process. To avoid short circuits between anodes and cathodes due to too much MnO2 and or gypsum deposit, anodes must be removed from the cells for cleaning(with the help of high pressure water jet nozzles). Anodes are made of a lead silver alloy that is not very stiff due to the softness of the lead. During the anode cleaning process the anode plate is mechanically straightened. This is necessary to obtain an almost constant distance between the cathode and anode surface, which ensures an even current density and reduces short circuit caused by bend anodes. The anode cleaning cycle will be 30 calendar days, which means that 475 anodes must be cleaned and straightened every day (including weekends). The cell slurry from the cell cleaning operation and the ground MnO2 anode slurry from the anode cleaning is stored in the MnO2 slurry buffer tank, which is equipped with an agitator to keep the solids in suspension. From this tank a controlled amount of MnO2 suspension is

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continuously pumped to the head tank of the neutral leaching section to support oxidation of the ferrous to ferric iron.

9.9.

Cathode handling and stripping After a deposition period of 48 hours at a current density of 400 A/m the cathodes must

be removed from the cells, brought to the stripping machines where the zinc is stripped, the aluminium cathode brushed and then returned to the cell. This so called stripping operation is done with two full mechanized stripping cranes and stripping machines. Each cell row is serviced by one dedicated stripping crane that transports cathodes between the cells and the stripping machine. Cathode zinc sheets are stacked, weight and delivered as cathode stacks to a forklift pick up station.

Fig18: The cathode stripping section consisting of the stripping cranes. The stripping crane and cathode stripping operation are fully automated. At the beginning of the shift the operator will select the cell stripping sequence (cells to be stripped) on the stripping crane control system. During the first day only odd cathodes from each cell are stripped whereas on the second day only even cathodes of the same cell group will be stripped.

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.Zinc loaded cathodes will be rinsed with water before they enter the stripping station to reduce the adhering spent electrolyte. The dirty cathode wash water is sent to the effluent treatment plant. If during the stripping operation a cathode could not be stripped due to sticky zinc or damaged side strip, the stripping machine operator can reject this cathode, which will automatically be replaced by a new or repaired one. The stripped zinc sheets are mechanically stacked on the stacking table located beneath the stripping machine floor. These cathode zinc sheet stacks are then weighed on a weighing station, moved to the stack lift to lift the cathode stacks to the forklift pick-up position.

9.10. Reagent preparation (RP) Three different chemical reagents are added to the electrolyte circuit to improve the cathode zinc quality. These reagent solutions are prepared in the reagent preparation section located on the east side of the cell house building. Each electrolyte circuit is equipped with its own reagent dosing pumps. The following reagents are added:

Strontium carbonate: Purpose: SrCO3 precipitates dissolved lead thus reduces lead in the cathode zinc Characteristics: fine ground white powder

Gelatine(glue Arabic): Purpose: gelatin (glue arabic) solution is added as an impurity suppressor Characteristics: fine galantine granulate If added in excess will make cath. zinc brittle and hard and tends to make zinc sticky

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Gelatine is first dissolved in agitated dissolving tanks and then the prepared solution is drained into the reagent storage and pump tanks for final concentration adjustment. Strontium carbonate is prepared directly in the corresponding mixing tank. 9.11. House keeping The key to a successful cell house operation is house keeping. The following house keeping tasks must be scheduled and strictly followed: Cooling Tower Cleaning Piping cleaning Tank cleaning Feed launder cleaning

Spent electrolyte has up to 1 g/l of solids in suspension. These solids tend to settle in all the big storage tanks. As in the process piping, gypsum will also precipitate and adhere to the walls bottom and suction pipelines of the storage tanks. These solids and accretions must be removed from the tanks at scheduled intervals. If accretions are not removed at regular intervals it will lead to accretion hardening making cleaning operation extremely difficult.

9.12. Casting, Zinc Dust Plant and Dross Plant The conceptual engineering for the cathode melting, casting and dross separation plants has been carried out with the objective of providing a modern plant with the maximum of automation to minimize labour requirements and employing the most modern methods and equipment to maximize process efficiency. A maximum of 2% of cathode converted to recycled dross oxide is guaranteed. Metallic zinc separated from the dross oxide and skims produced from the casting lines will be melted in the cathode melting furnaces by feeding through the cathode charge chutes. Zinc dust will be produced from molten metal transferred to the zinc dust plant or alternately, rejected ingots from the casting machines.

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9.12.1.

Design Criteria and Capacity

The melting plant is to be operated 330 days, 16 hours per day to process the cathode produced in the cell house. The cell house is designed to operate continuously, 24 hours per day, with the stripping function taking place 16 hours per day. The cathode is to be melted in two electric induction furnaces and cast into SHG ingots on two automatic casting lines. Equal tonnages of 1000 kg and 25 kg ingots will be produced. 9.12.2. Cathode Transport to Melting Plant

Zinc cathode bundles with a nominal weight of 3000 kg (2000 kg - 5000 kg) will exit the cell house on conveyors and be placed by HZLs lift trucks into either ground level storage or the automatic cathode transfer system feeding the melting and casting plant. The Automatic Cathode Transfer System receives the cathode bundles from the fork lifts, records the bundle weight, hoists the bundle to the melting furnace charge floor (approx. 8 m) and distributes the bundle to the automatic furnace feeding systems. The system capacity is 16 bundles per hour (48 t/h while handling 3000 kg bundles) The system is comprised of the following equipment: A chain conveyor A bundle hoisting system. A bundle distribution hoist-grab assembly.. A state of the art PLC system interfacing with the customers DCS and the furnace feeding system.

9.12.3.

Automatic Furnace Feed System

The Automatic Furnace Feed System receives individual cathode bundles with a nominal weight of 3000 kg (2000 kg - 5000 kg), in a horizontal orientation, from the Automatic Cathode Bundle Transfer System. The bundles are conveyed to the furnace feed chutes, rotated 90 to a vertical orientation, picked up by a powered gripping device and lowered into the melting furnace bath in a gentle and controlled fashion at a rate determined by the PLC control system. The automatic feed system has sufficient internal bundle storage capacity (22 operating positions @ 3000 kg) to support a 90 minutes interruption in bundles fed from the cell house.

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Additionally, provision is made for storage of 600 tonnes (one days production) of bundles on the charging floor. Removing excess bundles from the feed system by forklift will fill this storage. In the event of failure of the Cathode Bundle Transport System, the Automatic Furnace Feed System is designed to receive bundles of cathode, by forklift, from the charge floor storage area.

The power consumption for the melting and casting plant including dross plant will be 126 kW/tcath.Zn

Design Considerations: The automatic furnace feed system feeds bundles of cathode to two identical electric inductions, cathode melting furnaces. These furnaces operate on the basic principle that zinc cathodes may be melted in the furnace bath by continuously adding energy to the liquid metal in the furnace bath via inductors. Simultaneously, an amount of molten metal equal to that melted is continuously transferred to the casting machine to maintain the furnace at a constant bath level and temperature. Several key design factors must be considered in order to maximize the efficiency and operating life of the melting furnaces: The furnaces are equipped with an automatic temperature control system that maintains the bath at a constant temperature (approximately 530C). This temperature is maintained by varying the electrical power fed to the inductors. The Automatic Furnace Feed system automatically controls the level of the bath by adjusting the rate of cathode bundle immersion into the bath to equate the rate that molten metal is withdrawn from the furnace. This control system operates in exactly the same manner to allow the operator to instantly change from one production rate to another within the maximum melting rate of the furnace. 1.1.4 Cathode Melting Furnaces

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As described above, cathode melting will be carried out in two identical electric induction furnaces. The furnaces will have a guaranteed average melting rate of 22 tonnes per hour of zinc cathodes (maximum ~ 24 tonnes per hour). The melting rate is infinitely variable between 0% and 100% of the maximum melting rate and is controlled by the automatic control system to match the rate that molten metal is removed (pumped) from the furnace. Each furnace is equipped with a still well equipped with one or more molten metal pumps. The pump delivers molten zinc to a launder system feeding the casting machine. Each furnace feeds a single casting line. In addition, provision is made to pump molten zinc from one of the furnaces to the zinc dust production plant. In addition to cathode bundles, the furnace chutes are designed to receive metallic zinc from the dross separation plant and metallic zinc skims from the casting machines. This material is fed to any chute (normally one dedicated chute) from forklift transported to hoppers that have been raised to the charging floor by the freight elevator (lift). The required amount of NH4Cl to enhance the melting of this material is manually added to each hopper prior to dumping in the charge chute. When cathode zinc is melted, a layer of dross comprised mainly of zinc oxide entrained molten zinc droplets is produced. This dross must be removed from the furnace once in every 24 hours by manually skimming the dross from the surface of the bath in a process called drossing. This process consists of opening one of the doors on the side of the furnace, manually spreading a few kg of NH4Cl onto the dross layer, manually agitating the dross layer with a steel rake and finally using the rake to drag the dross through the open door of the furnace into a forklift tote bin. During the drossing process, the furnace is operated under conditions of increased ventilation to contain the fumes and dust that are generated by the agitation and dross removal processes. The totes of furnace dross are transported by lift truck to the dross cooling area, to await treatment in the dross separation plant 9.12.4. Ingot casting System

Melting furnaces feed the molten metal to the jumbo casting system (1000kg jumbo ingots) and the slab casting system (25 kg slab ingots)

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Fig.19: The casting system (the casting wheel and furnaces in the background) The casting system utilizes the latest technology to automatically pour molten zinc into moulds, solidify the molten zinc in a controlled manner to eliminate voids, remove the ingot from the mould, weigh and mark each ingot, strap the bundles(25 kg ingots into bundles of 1000kg) and report the product data to the customers DCS.

Fig.20: The robot transferring ingots from the conveyer at the melting and casting section.

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Ingots are removed from the casting system accumulation conveyor by the clients lift truck and placed in the product storage/shipping area east of the casting plant building. Bundles of product are removed from the slab casting system accumulation conveyor by the clients lift truck and placed in the product storage/shipping area east of the casting plant building.

Fig.21: Strapped zinc bundles ready for transport

9.12.5.

Zinc Dust Plant

The plant consists of 4 nos. channel type, twin chamber induction furnace of 100 KVA rating in which the solid virgin zinc ingots are melted at 500-550 degree temperature to make free molten metal bath up to desired level in the furnace. The molten metal is drawn out through specially made high alumina ceramic disk having an orifice of 3.5 mm dia to form a circular metal jet. this metal jet is atomized with high pressure compressed air passing through a specially made atomizer fixed to the furnace through a flexible hose. the metal jet is atomized into fine zinc dust particles passing through a duct line which is connected to composite air separating cyclone and the cooled dust is collected in the cyclone. Further zinc dust collected in the cyclone will be fed into a rotary screen through a rotary air lock valve, which fitted below the cyclone.

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The fine particles pass through the screen and get collected in the storage bin for further conveying/bagging. The oversize from the screen collected separately for re-melting. Very fine zinc dust particles will pass through a pulse jet automatic cleaning bag filter and clean air will pass through the ventilation fan to the stack.

Figure 22: zinc dust process flowsheet 9.12.6. Dross Plant

Due to oxidation and other chemical reactions taking place during the cathode melting process, approximately 2% of the cathode metal is converted to a dross product composed mainly of zinc oxide (ZnO). This dross product is a dense powdery material that forms on the surface of the furnace bath. As melting proceeds, dross is continuously being formed and accumulates on the bath surface. The accumulated dross layer must occasionally be removed to

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allow more cathodes to be melted. Entrained in this dross layer are molten droplets of metal, which are removed from the furnace with the dross. Once removed from the furnace the dross begins to cool. As the furnace dross cools, the molten droplets of zinc freeze into small beads of solid zinc. During the cooling process some of the molten zinc droplets coalesce to form lager particles of solid metal or drain to the bottom of the hopper to form a puddle that freezes into a larger piece of solid zinc. Cold furnace dross is a non-homogeneous mixture of metallic zinc particles and zinc oxide (ZnO) powder. The ZnO portion of the furnace dross is a dry, powdery substance similar in appearance to zinc calcine produced by the roaster plant. In order to recover the zinc present in the metallic particles, they must first be separated from the dross oxide, melted and cast into ingots. The dross oxide portion of the furnace contains 80% zinc. In order to recover the zinc present in the dross oxide it must be separated from the metallic zinc particles and recycled through the roaster, leaching and electrolytic plants. The separation of the metallic zinc particles from the dross oxide is carried out in the dross treatment plant. In this plant, the furnace dross is cooled and treated in a rotary grinding and dust removal system (air swept ball mill). The milling system produces a metallic zinc stream into hoppers while the dross oxide stream is removed as a dust and captured in a bag house. The dross oxide is then conveyed to the roasting plant by a pneumatic conveying system. The hoppers of metallic zinc are conveyed by lift truck to the charge floor and fed to the cathode meting furnace(s) for recovery of the contained zinc.

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Fig.23: Feed hopper and the ball mill The dross treatment plant is comprised of: Cooling bays where the hot furnace dross is deposited by lift truck A ventilated, tilting feed hopper system that receives cold furnace dross from the dross cooling bay(s) and delivers it to the air swept dross grinder. An air swept, rotating dross grinder (ball mill). Furnace dross is fed to the grinder in approximately 5 t batches. The grinder rotates to tumble the furnace dross charge. In a similar manner to an autogenously grinding mill, the heavier metallic zinc pieces act as grinding media to break up lumps of oxide and the tumbling action removes oxide particles from the zinc particles. As the grinder rotates, air is simultaneously injected into the grinder by a blower and withdrawn from by the dross system bag house. This air stream sweeps the light dust particles of dross oxide from the grinder while the zinc particles, because of their much higher density, remain in the grinder. When processing of the batch is complete, the direction of rotation of the grinder is reversed to eject the zinc metallic particles from the grinder. The zinc metallic particles exit the grinder onto a conveyor belt with a magnetic head pulley that removes any tramp iron that may have entered the dross stream (or in case of non-

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functioning of the conveyer, the metallic is removed from the mill manually and fed into bags).

10. UTILITIES10.1. COMPRESSOR:

Principle: The principle behind the compressor is increasing the velocity and the pressure of the atmospheric air.Impeller imparts velocity to the atmospheric air. In the diffuser the pressure of the air coming from the impeller increases but along with pressure the temperature also increases.To reduce the temperature of the air cooling is required, which is done with the help of cooler.

Process diagram:

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Figure 24 process flow sheet of compressor

Process:The atmospheric air contains some particulate matter.In the primary air filter (PAF) particles of size up to 8 microns and in the secondary air filter (SAF) particles of size up to 2 microns are removed.The outlet air from the SAF while going through each stage the velocity and the pressure both are increased ,followed by cooling after every stage.After the third stage cooling some amount of air goes to plant air receiver for plant air supply and the remaining goes to instrument air receiver after drying for instrument air supply.Plant air is used in the process and instrument air is used in the insruments of roaster,leaching,cell house and DM plant.

Salient features: Total production capacity of both plant air and instrument air is 7955 nm3/hr at7.5 kg/cm2 pressure.

PAF contains cloth wire mesh and SAF contains aluminium fines. Impeller speed is 45000 revolutions per minute.

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At every stage cooling the temperature of the air reduces from 65 to 32 degreeCelsius. Range of outlet temperature of the dryer air is 3-10 degree Celsius.

Air consumption (daily basis) :

P.A NZP

P.A CPP

P.A NLP

B.A NZP

I.A NZP

I.A CPP

I.A NLP

TOTAL

AIR

CONSUMPTION

Shift-A Shift-B Shift-C

6526 6480 6190

6324 7064 9158

2000 2000 2000

814 772 727

1695 1747 1647

3781 3694 3577

500 500 500

21640 nm3 22257 nm3 23799 nm3

NZP: New Zinc plant I.A : Instrument Air CPP : Captive Power Plant NLP : New Lead Plant B.A : Baggage air

10.2. COOLING TOWERSThe main purpose of the cooling towers is reduce the temperature of the incoming water by maintaining a particular temperature difference between the incoming and the outgoing water. Number of cooling towers: 5 (CT-1, CT-2, CT-3, CT-4, CT-5) From Gosunda dam nearly 430 m3/hr of water is required for hydro plant. Consumption is 5000 m3/day. All cooling towers are induced draft cross flow towers.

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Approximately 10500 m3/hr of water running in circulation every time at the time of running all cooling towers. Evaporation loss in all cooling towers is approximately 140 m3/hr. Bleed offs in all cooling towers is nearly 23 m3/hr. Make up water required in all cooling towers is nearly 160 m3/hr. Total side stream filter water required is approximately 310 m3/hr. Differential pressure in side stream filter is 0.8 kg / cm2 Source of Water supply for the first four cooling towers is preheated filter water from DM plant. Source of water supply for the fifth cooling tower is soft water from DM plant. CT-1 water goes to New Acid Plant. CT-2 water goes to New Gas Cooling Plant. CT-3 water is used in Turbo Generator & Utilities. CT-4 water is used in cell house and in melting & casting.

In Cell house : For bus bar cooling : 60 m3/hr For rectifier cooling : 50 m3/hr For Inductor cooling : 60 m3/hr For Ingots cooling : 120 m3/hr

In melting and casting:

CT-5 water is used in Roaster & centac air compressor. In centac air compressor 150m3/hr of water is in use. Roaster requirement is 310 m3/hr of water.

For Roaster cooling drum, nearly 295 m3/hr is used and the remaining goes to Roaster air blower.

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COOLING TOWER

PUMP CAPACITIES (m3/hr)

OUTLET PRESSURES (kg/cm2)

CT-1 CT-2 CT-3 CT-4 CT-5

350 300 450 460 200

4.5 4.0 3.2 3.5 3.5

SYSTEM DETAILS:

Parameter Water holding capacity

Unit

CT-1

CT-2

CT-3

CT-4

CT-5

M3

990

570

920

570

60

Circulation rate Temperature difference Evaporation loss

M3/hr

3300

1925

3060

1725

460

Degree Celsius M3/hr

10.5

10.0

8.0

10.5

8.0

39.11

28.51

36.26

26.83

5.45

Bleed-off

M3/hr

6.51

4.75

6.04

4.47

0.9

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Cycle of concentration Make up Water Side stream filter water M3/hr M3/hr

7

7

7

7

7

45.62

33.26

42.30

31.30

6.35

99

58

92

41

14

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10.3. DM Plant:

Figure25: Flow Diagram of dm plant

CWST: Cold Water Storage Tank PSF: Primary Sand Filter

FWST: Filtered Water Storage Tank ACF: Activated Carbon Filter

SWST: Soft Water Storage Tank NLP: New Lead Plant

WAC: Weak Acid Cation SAC: Strong Acid Cation

WBA: Weak Base Anion SBA: MB: Strong Base Anion Mixed Bed

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DMWST: De-mineralized water stora