CSP Case Study

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1.0 COPPER SMELTER PROJECT DESCRIPTION

The objective of this chapter is to discuss various processes of the Copper SmelterProject, with particular reference to their pollution generating potential. The latter

is important for environmental impact analysis of and the development of

environmental management plan for the project.

The integrated copper smelter project will comprise a copper smelter plant,

sulfuric acid plant, phosphoric acid plant, precious metal recovery plant andcaptive power plant. The copper smelter plant will be based on Outokumpu Flash

Smelting Technology. The sulfuric acid plant will use technology from Monsanto

Enviro-Chem, USA. The electrolytic refining process for copper extraction is

based on the ISA electro refining process and MIM, Australia, designed byOutokumpu. The precious metal plant will use the technology from Outokumpu,

Finland. The lignite based captive power plant and phosphoric acid plant with

fluorine recovery system will utilize technology from Prayon, Belgium. The

operation of each of these plants is discussed in the following paragraphs. Thepollution potential of each plant with respect to the generation of air pollutants,

water pollutants and solid waste is also discussed. However, quantitative detailsrelated to the discharge of potential pollutants are provided in Chapter 6, which

discusses the environmental impact assessment.

1.1 Copper Smelter Plant

The copper smelter plant operation will involve

i) Receiving, storage and processing of raw material, i.e., copper

concentrate, silica flux and coke.

ii) Extraction of copper from the copper concentrate using Flash Smelting

Furnace (FSF) and Peirce Smith Converter.

iii) Fire refining of the blister copper to produce 99.5% Cu as anodes.

iv) Electrolytic refining to produce 99.99% Cu as copper cathods, and

v) Recovery of Grade B copper anodes from the spent electrolyte.

Flash Smelting area process block diagram and Refinery area block diagram areshown in Figure 3.1 and Figure 3.2, respectively. Various processes of the plant

are discussed in detail in the following paragraphs.

1.1.1 Storage and processing of raw material

The copper concentrate, silica flux and coke will be transported to the plant

premises using a belt conveyor system from the jetty, and stored in storage bays.

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The concentrate will be stored in a covered building with a capacity to hold 2

months supply. The concentrate from the storage bays will be blended with silica

flux and coke in proper proportion and the blend will be transferred to day bins,which will be made of concrete with stainless steel inside lining. The concentrate

mixture will be fed into a concurrent flow multicoil steam dryer to reduce the

moisture content to less than 0.2% to meet the requirement of the feed for a flashfurnace. This mixture will be stored in dry bins. The mixture from the dry bins

will be conveyed into the charge drag conveyor to feed the mixture into the

furnace. There is potential for dust emissions from the dryer. Bag filters will beprovided to clean the off gases from the dryer before these are discharged into the

atmosphere through the dryer stack.

1.1.2 Flash smelting furnace operation

The dried concentrate mixture will be smelted in a flash smelting furnace, which

will be preheated to 1300C. The fuel oil fired burners will be used for

preheating the furnace. Preheated oxygen enriched air will be fed during thesmelting operation to control the process temperature, the latter depending on the

degree of oxygen enrichment. In case, the concentrate reaction heat (reactions areexothermic) is low, some fuel will have to be introduced into the reaction shaft.

Smelting of the concentrate will result in the formation of two layers viz., bottomlayer comprising the matte the top layer will be the flash smelting slag. The matte

(65% copper) from the smelter will periodically be poured through launders to the

matte ladles and carried to a Peirce Smith converter, whereas the slag will be

transmitted to the electric slag cleaning furnace. The flash smelting furnace offgases will be treated for particulate dust recovery using an electrostatic

precipitator which will be transferred to the flue dust bin of the flash smelting

furnace. The dust free and sulfur dioxide rich flue gas stream will be treated forthe recovery of sulfur dioxide.

1.1.3 Pierce smith converter operation

In the converter, copper matte from the flash smelter will be subjected to two

stage process i.e., slag blow and copper blow. In the slag blow process, air will

be blown through the molten matte to remove sulfur and iron to produce whitemetal. The latter would mix with silica to produce molten slag, which will be

transmitted to the electric slag cleaning furnace. Silica flux will be fed to the

converter from silica flux bins. During the copper blow stage, sulfur in whitemetal will be blown to sulfur dioxide producing blister copper. The blister copper

produced in the converter is expected to contain about 98.5% copper.

Blister copper produced in the Pierce Smith converter is likely to contain various

impurities e.g., sulfur, oxygen, nickel, iron, zinc, lead, cobalt, selenium, arsenic,

antimony, bismuth, gold and silver. These impurities will be removed by fire

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refining and electrorefining to obtain copper with specific physical and chemical

properties.

The process gases from the converter hoods will be treated for dust removal.

Dust so collected will be transferred back to the dust bin of the flash smelting

furnace and the gases will be further cleaned in the gas cleaning section of thesulfuric acid plant. Heat carried by flue gases will be recovered by using a waste

heat boiler. A small amount of gas leaking outside the primary gas hood will be

captured by the secondary gas hood and then led through the secondary gasscrubbers to the main stack.

1.1.4 Refining and anode casting operation

Blister copper from the converter will be charged to an anode furnace for fire

refining to increase the copper content to 99.5%. The furnace will be heated by

using fuel oil to keep copper in the molten state during charging. After charging,

oxidation will be carried out by blowing air through the tuyeres in molten copper.Impurities such as iron will be transformed to the slag and sulfur will be

transferred to the gaseous phase. The off-gases from the anode furnace will beincinerated. The slag will be skimmed with utmost care to avoid remixing of

impurities with copper during deoxidation.

The oxidation phase will be followed by deoxidation phase, where only the excess

oxygen will be removed from the copper by using LPG as the reducing agent.

The refined copper will be caste into copper anodes on a rotating anode casting

wheel. The anode cooling waters will be circulated through the water coolingarea where copper scales will be settled in a settling tank and the water will be

cooled using cooling towers. These anodes will be dispatched to a tank house for

electrorefining.

During deoxidation stage and idling, the anode furnace off-gases are led through a

ventilation gas bag house to the anode casting area stack.

1.1.5 Electro-refining operation

The electrorefining cell will be used for further refining of the extracted copper.The cell will contain permanent stainless steel cathodes and copper anodes casted

from the blister copper in an electrolytic solution i.e. an acidic copper sulfate

solution. DC current will be passed through cells, which would result in themovement of copper ions from the copper anode to the stainless steel cathode

resulting in 99.99% of copper deposition on the cathodes. The product cathode is

transported to the storage.

During the electrorefining process, the copper anode will be dissolved except for

those impurities, which include precious metals e.g., selenium, tellurium and lead.

Other metals such as copper, nickel, arsenic, antimony and bismuth will dissolve

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partially. The impurities will deposit as slime at the bottom of the electrolytic

cells. The slime will also contain finely divided copper powder from the chemical

degradation of cuprous oxide contained in the anodes. The slime will be removedfrom the cells at the anode replacement time and will be pumped to the slime

treatment thickener for settling. The thickened slime will then be leached

batchwise in an atmospheric leaching reactor. In the reactor, the anode slime,electrolyte and added acid will be mixed by introducing oxygen. The mixture will

be filtered. The copper containing filtrate will be treated in the decopperising

system after possible cementation of tellurium to avoid contamination. Thecopper free leached slime will be transported to the precious metal plant for

further processing.

Other impurities will partially leach out into the electrolyte. A small portion ofthe electrolyte will be bled off in the process to restrict the level of impurities in

the electrolyte.

The cathodes and anode scrap from the commercial cells will be washed free ofelectrolyte and anode slime. Anode scrap will be recycled to the smelter.

The electrolyte bleed and scrap wash water will be treated in the effluent

treatment plant.

1.1.6 Treatment of spent electrolyte

The bleed from the electrolytic cells will be treated to recover copper sulfate,

grade B copper cathodes and copper/arsenic precipitate. An evaporative coppersulfate crystallizer will be used for the recovery of copper, which will be returned

to the main circuit for keeping the copper concentration at a constant level. The

spent electrolyte from the crystallizer will be led to the liberator cells for furthertreatment. The process will involve three stage electrowinning to produce Grade

B cathodes, impure cathodes and As/Cu powder. The first stage solid cathodes

will be sold in the market, whereas the second stage impure cathodes will be sentback to the smelter. The latter will be washed using high-pressure water jets in

the scrap washing machine. Cu/As powder will be packed in PVC drums for

storage. This powder will contain antimony, bismuth and tellurium in addition to

copper and arsenic.

The decopperised bleed will be sent to the neutralization unit of the ETP for

further treatment. Water from anode scrap washing will also be led to the ETP.

1.1.7 Slag cleaning furnace

In the slag cleaning furnace, the flash smelting furnace slag (2% copper content)

and Pierce Smith converter slag (10% copper) will be treated by adding coke,

which will reduce copper and other metal oxides present in the slag. Coke and

reverts will be fed through the furnace roof. Electric power will be needed for

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reduction reactions, heat losses and smelting of reverts. At temperatures higher

than, gases containing SO2 and dust will have to be discharged, and these gases

will be led to the atmosphere through the electric furnace stack. Slag from theelectric furnace will be tapped into a slag granulation unit. The granulation

launders will be fitted with nozzles through which water will be sprayed on the

molten slag to form slag granules. Granulation water will be circulated through asettling pond, cooling pond and cooling towers. A part of granulation water will

be bled off to maintain its quality. The size of granules would typically vary from

0.17 mm to 6 mm.

Granulated slag will be transported to the slag storage area. The matte from the

slag cleaning furnace will be taken back to the Pierce Smith converter. The

granulation water bleed will be led to the ETP for treatment.

1.1.8 Cooling water circuit

The cooling water is first pumped to the head tank of the jacket cooling system.Water flows from the head tank to the copper cooling elements of the flash

smelting, slag cleaning and anode furnaces. Warm water from the coolingelements is led through plate heat exchangers and then returned to the jacket

water tank. A small bleed is led out, which can be used for general cooling or as

process water, and the corresponding amount of make up water is added.

1.1.9 Pollution generation potential of the smelter plant

Gaseous emissions

Dust will be generated during the drying of the copper concentrate mixture in the

drying area. The dust will be collected in bag filters, and the uncaptured portionof the dust will be discharged into the atmosphere through the dryer stack.

Dust emissions will also be generated at the converter feed system and these willbe led to the atmosphere the converter area stack.

During smelting operation, gas leakages from matte slag tapping, slag cleaning

furnace, secondary gas hoods will be collected and passed through the secondarygas scrubber, and the unabsorbed gases will be discharged into the atmosphere

through the main stack.

The anode furnace off-gases generated during deoxidation stage and idling will be

led through a ventilation gas bag house to capture dust. The small amount of dust

which escapes the filter will be discharged into the atmosphere through the anodecasting area stack.

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Dust and sulfur dioxide containing gases will also be discharged into the

atmosphere from the slag cleaning electric furnace when the temperature of

incineration gases is higher than 180C.

Liquid effluents

Various liquid effluent streams generated in the copper smelter plant operation

are:

Bleed from the liberator cell or spent electrolyte containing mainly sulfuric

acid and heavy metals;

Bleed from slag granulation unit;

Bleed from cooling water circuit; and

Scrubber water from the secondary gas scrubber.

The secondary gas scrubber will receive gases from other plants. Both process

waters and cooling water will be recycled to the maximum extent possible tominimize the generation of wastewater. Only the bleed from a process streamwill be discharged to maintain the quality of the stream. The above identified

waste streams are treated in the Effluent Treatment Plant.

Solid wastes

Slag generated from FSF and PS converter after cleaning and granulation willhave to be either disposed off as a solid waste or reutilised.

Liquid effluent streams that will be treated in the Effluent Treatment Plant (ETP)

will contribute to the generation of the ETP sludge, which needs to be disposedoff.

Copper / Arsenic powder separated from the Grade B copper cathodes in the thirdstage of the electrowining process need to be adequately packed and disposed off.

1.2 Cakes and Billets Plant

Copper cathodes from electrorefining process will be stored in buckets in the

storage area of the cakes and billets plant, ready for discharging these into thecharging wagon. These cathodes will be fed into the induction furnace by tilting

the charge wagon at the front opening of the induction furnace. The latter will bea channel type induction furnace which completely operates on electricity.

During melting, the furnace will be in a horizontal position and during casting itwill be tilted to allow the melt to flow into a casting mold along a refractory lined

launder till the desired length of cast is reached. These molds will be oscillating

and the melt in these molds will be covered by graphite powder to preventoxidation. The mold will be surrounded by a special copper jacket which will be

water cooled. Upon leaving the bottom of the mold, the already solidified cast

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will further cooled by direct cooling water spray. The cast will be sawn from both

ends and the edge cuttings will be recycled to the furnace. The sawn casts will be

transported out of the building by means of roller conveyors.

Gas burners will be provided for preheating the launder prior to casting to control

the flow of molten metal. The fumes will be collected by a fume hood andexhausted to atmosphere via the anode casting stack.

Gaseous emissions

Fume from the anode casting unit will be led to the anode casting stack for

discharging these into the atmosphere.

1.3 Precious Metal Plant

The leached slime from the refinery area will be further treated in the precious

metal plant, which would involve the recovery of the following precious metals.

Selenium recovery

Silver recovery

Gold and platinum recovery

The Precious Metal Plant block diagram is shown in Figure 3.3.

1.3.1 Selenium recovery

Selenium roasting

The leached slime from the refinery will be transferred to the roasting trays, and

then carried to the roasting furnace. Roasting will be carried out at 600C in thepresence of sulfur dioxide and oxygen, which will be fed as reagents. As a result

of roasting, Selenium Dioxide (SeO2) will be generated in the furnace, which will

be sucked out through an ejector and passed through aqueous solution containingsulfuric acid. Here, SeO2 will be reduced to elemental selenium by sulfur dioxide.

In this process, SO2 will be oxidized to SO3, which will subsequently be absorbed

in the aqueous solution containing sulfuric acid. A part of the sulfuric acid

solution (bleed) will be used for slime leaching. The desalinized slime will bedischarged into a feeding bin of the Dor'e Smelting Furnace.

The reduced elemental raw selenium powder will be filtered, washed and dried ordirectly smelted to produce 99.5% commercial grade selenium. Exhaust gases

from roasting will be led to secondary scrubbing area of the precious metal plant.

Vapor gases generated during filtering will be collected by a hood and then led tothe ventilation pipeline.

Selenium distillation

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Dried crude selenium will be loaded into a distillation retort, and then placed into

a distillation furnace. The furnace will be electrically heated to a temperature ofabout 700C at which the distillation of selenium will take place. Distilled

selenium will be run down into flowing water so that selenium is granulated. The

granulated selenium (99.95%) is dried and packed. The distillation residue isrecycled to the selenium roasting furnace. The exhaust gases will be filtered

through bag filters and led to the ventilation pipeline. The collected dust will be

circulated to the selenium roasting trays.

1.3.2 Silver recovery

Dor'e smelting

The desalinized slime will be mixed with soda and borax and then smelted

batchwise in a rotary type Dor'e furnace (TROF - converter) for the recovery of

silver. The smelting process will be carried out in two stages. In the first stage,the materials will be smelted and primary slag separated out from metal. The

primary slag will be sent to the copper smelter. In the second stge of smelting,oxygen refining will be carried out in the furnace. The refined metal will be cast

into anodes and subsequently subjected to silver electrolysis. The silver rich slag

produced during the refining stage will be recycled into the furnace along with thesubsequent feed batches. The fule gases will be passed through a bat filter and

vented out through a stck. The flue dust will be recycled to the Dor'e Smelting

Furnace.

Silver electrolysis

Dor'e anodes will be subjected to electrolysis in Moebius cells to separate silverfrom gold and platinum metals. Silver will dissolve in the nitric electrolyte and

on the passage of current will deposit as crystals on the cathodes. These silver

crystals will be scrapped from the cathode surface, washed, dried, melted and castinto bars or granules. Gold, platinum and some silver left in the anodes will be

collected in bags surrounding the anodes.

After the electrolyte has been contaminated, it will be replaced by a newelectrolyte (AgNO3). The spent electrolyte and washing waters will be treated in

the desilverizing tank.

Silver cementation

In this process, all spent solutions, which may contain dissolved silver, will bedesilverized. These solutions include the spent electrolyte from the silver

electrolysis, washing waters of gold mud, and washing waters of crystal silver.

The desilverizing will be carried out in a desilverisation tank by the cementation

reaction with zinc or copper powder. The cement silver produced in this process

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will be filtered, washed and recycled to the Dor'e furnace. Waste liquid will

either be partly or totally recirculated in the process. Any effluent wll be treated

in the effluent treatment plant.

1.3.3 Gold and platinum recovery

Gold treatment process

The gold mud harvested from the Moebius cells will be washed and then boiled inconcentrated sulfuric acid to remove residual silver to get gold sand containing

typically 90-95% gold. The Ag2SO4 formed in the process will be decanted and

led to the desilverizing tank. Gold sand will be leached with concentrated

hydrochloric acid (30-35% HCl) using hydrogen peroxide (50% H2O2) as areagent. After leaching, the batch will be filtered and the residue mostly silver

chloride (AgCl) will be recycled to the Dor'e smelting process. The leached

product (AuCl3) will be subjected to the precipitation process where gold will be

precipitated in two steps using sodium-meta-bisulfite (Na2S2O5) as a reagent. Thefine gold powder (Au > 99.99%) obtained after the reduction will be filtered,

washed, dried and finally melted to form gold bars. The process is repeatedseveral times till most of the gold is recovered.

Platinum metal will be precipitated from the solution using metallic iron, whereplatinum metal chlorides will be reduced to form iron chlorides. The concentrate,

which contains 85-95% platinum metal, will be washed, dried and sold. The

bleed off will be transferred to the effluent treatment plant for further processing.

Cement silver from the leaching of gold mud and spent electrolyte produced in

Moebius system as well as residue from the gold treatment process are also

recycled to the Dor'e furnace.

1.3.4 Pollution potential of the PM plant

Air emissions

Exhaust gases containing sulfur dioxide and dust from selenium roasting will be

passed through secondary scrubber and then led to the scrubber gas stack of themain stack.

Vapors from selenium filtering and distillation will be lead through ventilationbag filter and then discharged into the atmosphere through the precious metal

stack. Flue gases from the silver recovery process will also be vented out to the

atmosphere after passing through a bag house.

Liquid effluents

The following effluent streams will be generated from the precious metal plant:

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Bleed from the spent electrolyte;

Waste liquid from the silver cementation process; and

Wash waters

Solid waste

Liquid effluent streams that will be treated in the Effluent Treatment Plant (ETP)

will contribute to the generation of the ETP sludge, which needs to be disposed

off.

1.4 Sulfuric Acid Plant

The SO2 rich gases from the flash smelting furnace and the converter are used to

produce sulfuric acid in the sulfuric acid plant. Various steps involved in the

production are :

Cleaning of the sulfur dioxide (SO2) gases from the smelter

Drying of the sulfur dioxide gas

Converting sulfur dioxide gas into sulfur trioxide (SO2) gas, and

Absorbing sulfur trioxide gas in the dilute acid to form 96-98% sulfuric acid

About 99.8% of SO2 present in smelter gases will be recovered during the

production of sulfuric acid. After recovering SO2 in the form of H2SO4, SO2emissions in the flue gas stream are expected to be in the range of 150-500 ppm.Figure 3.4 shows the sulfuric acid plant area block diagram.

1.4.1 Gas cleaning section

The smelter gas containing SO2 will be cleaned using Monsanto Enviro-Chem's

state-of-the-art Dyna Wave gas cleaning system. in this system, gas will enter the

top of a reverse jet scrubber and the circulating weak acid will be injectedupward. A standing wave of highly turbulent flow will be created at the point

where the liquid is reversed by the gas. In this region, also called as forth zone,

the gas will be efficiently quenched; and dust, condensed fume and SO 3/acid mistwill be removed from the gas stream. Two reverse jet scrubbers will be used if

the amount of contamination in the gas is high. The gas will then be led to the

final reverse jet scrubber, where halogens will be removed and the gas will becooled to meet acid plant water balance requirements by bringing it in contact

with externally cooled weak acid.

Make up water will be fed into the final reverse jet scrubber to adjust weak acidstrength. The weak acid effluent will be led countercurrent from the final to first

vessel, stripped of SO2 using air, and finally pumped to effluent treatment plant.

The stripping air leaving from the first reverse jet scrubber will be led to a duct.The cooled gas leaving the Dyna Wave System will then be passed through a

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chevron vane demister located at the top of the final vessel to remove the

remaining particles of acid mist and metallic fumes; and solids will be removed

by using wet electrostatic precipitators. After leaving the wet electrostatic mistprecipitators, the gas will enter the drying section of the acid plant.

1.4.2 Gas drying section

The cleaned gas from Dynba Wave gas cleaning system and the final wet

electrostatic precipitators will be diluted by air to adjust the O2/SO2 ratio and thenpassed through the drying tower where strong sulfuric acid will be counter-

currently sprayed. As a result, moisture present in the gas stream will be absorbed

into the strong acid. Heat evolved during the absorption process will be

dissipated by externally cooling the circulating acid by using cooling water. Thelatter will be recirculated through cooling towers.

The acid circulated in the drying tower will get diluted due to water vapor

removed from the SO2 gas.

1.4.3 Conversion and absorption of SO2

The dry and clean SO2 gas will be led to the contact converter for oxidizing it to

SO3 using vanadium pentoxide (V2O5) catalyst at 420-650C. The oxidationreactions are exothermic and these will generate heat. This heat will be mainly

utilized in preheating of incoming gases. The conversion of SO2 to SO3 will be a

two stage process. In the first stage, the gas will be passed through the vanadium

pentoxide catalyst layer three times. After each pass, the oxidized hot gas will becooled back to minimum ignition temperature (420C). the gas will be led

through interpass absorption tower, where SO3 is absorbed into circulating acid.

About 96% of the SO2 gas will be converted into SO3 during the first stage ofconversion. The unabsorbed gas will be led back to the converter for the second

stage of conversion where the gas passes over one more layer of catalyst. Finally,

the gas will be led through the final absorption tower to the main stack for ventingit into the atmosphere. The total conversion, after 3 + 1 passes is expected to be

over 99.75%.

In the absorption towers, sulfur trioxide will be absorbed into 98-99% sulfuricacid. The SO2 gas will react with the water content of the acid to further

concentrate the sulfuric acid. There will be a total of three acid circulating

systems with their own circulating pumps, pipings, acid cooling heat exchangersand pump tanks. One of these systems will be used for gas drying. The other two

will be used for SO3 interpass absorption and final absorption towers. The three

acid circulating systems will be interconnected to allow the control of the acidconcentrations in each of the acid circulation systems. The drying acid will be

concentrated with strong absorption acid, and the absorption acid will be diluted

with drying acid. The concentration of absorption acid is kept constant by

adjusting make-up water. Acid will be pumped from the final absorption pump

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tank to a product pump tank. The product concentration will be maintained at 93-

96% acid. The product acid will finally be pumped to the storage tank.

1.4.4 Heat recovery

The reactions involved in the conversion of SO 2 into SO3 and absorption of SO3into dilute H2SO4 will be highly exothermic. The heat generated from SO2conversion and SO3 absorption will be recovered by closed hot water circulating

systems. The generated hot waters will be utilized by hot water users and/orcooled with a heat exchanger connected to the secondary cooling system at the

cooling water area.

1.4.5 Acid storage

The role of the acid storage in the acid plant area will be to store the product

sulfuric acid in the place from where the acid can be further pumped to acid

storage near the harbor.

1.4.6 Pollution potential of the sulfuric acid plant

Air emissions

The unabsorbed gases from the conversion and absorption unit of the sulfuric acid

plant will be vented into the atmosphere through the acid plant stack of the main

stack.

Liquid effluent

A portion of the weak acid left after the stripping of sulfur dioxide gas from theconcentrated sulfuric acid will be discharged into the ETP.

Solid waste

Liquid effluent streams, treated in the Effluent Treatment Plant (ETP) will

contribute to the generation of the ETP sludge, which needs to be disposed off.

1.5 Phosphoric Acid Plant

Phosphoric acid plant uses rock phosphate and sulfuric acid from the sulfuric acidplant as the raw materials. Rock Phosphate of mesh size 40% will be ground in

an open circuit ball mill to obtain rock phosphate slurry with 68 to 70% solid

content. The slurry will be pumped to multi-compartment reactor where it wouldreact with 98% sulfuric acid to form phosphoric acid and phosphogypsum. Being

exothermic, the reaction will generate heat. The temperature of the reactor will be

maintained between 78 to 80C to facilitate the reaction to take dihydrate route

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and the formation of gypsum crystals. Due to exothermic nature of the reaction,

fumes of HF and SiF4 will be generated in the reactor.

The slurry from the reactor will be pumped to belt filter to a separate

phosphogypsum crystals from the liquid phase phosphoric acid (29%). This

dilute phosphoric acid will be concentrated up to 52% to meet the merchant gradestandard in a rubber lined flash chamber. Vacuum in the chamber will be

maintained by two stage steam ejectors. During acid concentration process,

fluorine vapors will also be evolved.

The HF and F carrying gases from the reactor, belt filter section and concentration

chamber will be led to a gas scrubber involving three stage washings with cold

water. The scrubbed gas will be vented to the atmosphere through a 60 meter tallstack.

The phosphogypsum separated out by the belt filter from acid slurry will be

dumped in a rectangular storage/dump yard. The storage / dump yard will belined with a synthetic LDPE liner to prevent the contamination of subsoil with

acid water. The liquid from the dump yard will be collected by a garland drainwith a pit from where it will be pumped out of the yard.

The plant will also have a continuous blowdown of acidic water at the rate of 45m/hr from the cooling tower. The blowdown will be maintained by giving a

purge from the fluorine absorber seal tank.

The liquid effluents from the plant will be collected in an effluent buffer tank andpumped to liquid effluent neutralization unit for two stage neutralization with

CaCO3 solution. The neutralized effluent will be routed to the treated effluent

lagoon of the centralized effluent treatment plant.

1.5.1 Pollution potential of the phosphoric acid plant

Air emissions

The unabsorbed gases containing F from the scrubber unit of the phosphoric acid

plant will be vented to the atmosphere through the Phosphoric acid plant stack.

Liquid effluent

The following liquid effluents will be generated by the plant:

Scrubber water

Phosphoric acid dump yard effluent

Phosphoric acid plant blowdown

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These effluents will be subjected to two stage neutralization with CaCO3 solution

and the neutralized effluent discharged into the treated effluent lagoon.

Solid waste

Phosphogypsum produced as a byproduct will have to be disposed off adequatelyor used as a resource.

1.6 Captive Power Plant

A 24.5 MW lignite based Captive Power Plant will be installed to supplement

power supplied by the Gujarat Electricity Board and during emergency power

sheeding or grid failure. The power plant will use 140 T/Hr Circulating FludisedBed Combustion (CFBC) boiler with MCR rating at 66 Kg/cm steam pressure

and 485C steam temperature at superheated outlet. In CFBC boilers, fuel

particles in suspension escaping the combustion chamber of the furnace will be

captured by a cyclone and circulated back to the combustion chamber. Thiswould results in better combustion efficiency.

A condensing type steam turbine with provision to extract steam for regenerative

feed heating and process requirements will be used. The turbine will be complete

with steam ejectors, deaerating heater and boiler feed pumps. The condensatefrom the condenser will be pumped to the condensate storage tank, where from it

will be sent to the deaerator through a LP heater. The condensate is finally

circulated back to boiler through a HP heater.

The use of CFCB boiler will also result in low NO x emissions. Under usual

operating conditions of the boiler, 90% of fuel nitrogen will be converted to N 2.

The thermal NOx, which is produced at temperatures of 1200 to 1300C, will notbe formed as the optimum temperature in the fludised bed is about 850C.

The SO2 emissions from the boiler furnace will be limited by injecting limestoneon the furnace bed. The limestone injection will fix sulfur present in coal into ash

and a very little quantity of SO2 will escape into the atmosphere. Since fly ash is

recirculated into the combustion chamber, line stone reutilisation for sulfur

fixation will be very high.

An electrostatic precipitator will be used for collecting particulate matter, and

only small portion of fly ash will be discharged into the atmosphere.

1.6.1 Pollution generating potential of the captive power plant

Air emissions

The combustion of lignite will generate fly ash, SO2 and NOx. Even though

circulating fludised bed combustion boiler with lime injection system will

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considerably reduce SO2 and NOx emissions, small quantities of these pollutants

will have to discharged into the atmosphere. An electrostatic precipitator will be

used for capturing fly ash, and only a very small percentage of it will bedischarged into the air.

Liquid effluent

Boiler blowdown will constitute to liquid waste generated from the captive power

plant. The quantity of this waste will be very small.

Solid waste

Solid waste will constitute fly ash collected by the electrostatic precipitator andbottom clinker i.e., bottom ash and gypsum (produced as a result of sulfur fixation

of lime stone in the boiler furnace).

In this chapter, potential sources of air pollution, liquid waste and solid wastehave been identified for each plant of the Copper Smelter Project. As is obvious

from the above discussion, various pollution control systems are already part ofthe various process units. These pollution control systems along with other

mitigation measures planned for reducing adverse environmental implications of

the project are discussed in the following chapter.

2.0 MITIGATION MEASURES

The selection/identification of mitigation measures for reducing the adverseenvironmental impacts of the copper smelter project formed the integral part of

the copper smelter project design. Thus, the selection of clean and efficient

technologies, installation of the end-of-pipe air pollution control equipment andsetting up of the effluent treatment plant were important elements of the project

design. In addition to these, the solid waste management, greenbelt and

community welfare plans were prepared to alleviate the other adverse impactsanticipated due to the project. This chapter highlights various design/technology

related features of the copper smelter project and end-of-pipe pollution controls

installed for protecting the air, water and land environment. The salient points of

the greenbelt development, solid waste management and community welfareplans are also highlighted in this chapter.

2.1 Air Pollution Controls

Air pollution sources of the project will be equipped with appropriate pollution

control equipment to reduce emissions to levels which comply with the emissionstandards and / or do not cause violation of the ambient air quality standards.

Table 4.1 depicts various air pollution sources of the copper smelter project and

the control equipment that will be used for each of these sources.

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A short description on the operation of the equipments listed in Table 4.1 is

presented in the following paragraphs.

Cyclones

Cyclones, because of their low cost, are commonly used for collecting dust. Sincethese can be constructed with refractory lining, dust bearing hot gases (up to

982C) can easily be treated by cyclones. The dust bearing gas stream is

tangentially introduced into a cyclone to impart it a circular motion. Dustparticles being heavier than gas molecules are thrown out against the wall by the

centrifugal force. These dust particles slide down the walls and get collected in a

hopper. Cyclones are typically effective for larger size particles (dust), and

therefore, will be used for dust generated in dryer area.

Electrostatic Precipitators (ESP)

It is an extremely efficient air-pollution control device for capturing particulatematter (particularly small size particles which are generated in combustion

processes) from a gas stream with efficiency more than 99 percent. In an ESP, ahigh voltage source is used to negatively charge corona to create a strong electric

field. Due to this strong electric field, gas molecules get ionized and particles

present in the gas stream become negatively charged. These negatively chargedparticles move towards the grounded collecting plates, from where these are

periodically removed. The initial capital investment for an ESP is high, but it is

off set by its low operating cost. ESPs will be used for collecting fly ash from the

captive power plant.

Table 2.1 Various sources of air pollution and the Controls to be adopted

Plant Area Pollution

Source

Pollutant Control Facility

Concentrate

Drying Area

Dryer Off

Gases

Dust (bearing

Cu concentrate)

Cyclone and Electrostatic

Precipitator for recovery and

recycle of dust.

Smelter &

Converter OffGases

SO2Dust (bearingCu, copper

oxides and

sulfides)

ESP for recovery and recycle

of dust (dust free gas taken toacid plant for sulfuric acid

production)

Smelting

Furnace &Converter

Launders,

tapholes andopenings in

smelter and

electric

furnace

Fugitive Fumes

containing SO2

To be exhausted outside

building through hood,ducting, ID fan, stack.

Axial fans to be installed at

top floor for general exhaust.

Converter Fugitive fumes To be exhausted outside

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Secondary

Fumes

containing SO2

and other minorconstituents

building through hood,

ducting, ID fan and stack.

AnodeRefining and

Casting Plant

Gas fromAnode

Furnace

Dust To be exhausted outside thebuilding through hood,

ducting, ID fan and stack.Alternatively, this shall beused in rotary dryer.

RefineryPlant

Fumesgenerated in

Cell house

Acidic fumes Building ventilation systemfor adequate air exchange.

Also fume extraction systems

for selected areas.

Sulfuric Acid

Plant

Tail Gas SO2/ SO3 and

acid mist

Double Contact Double

Absorption (DCDA) Plant

Phosphoric

Acid Plant

Tail Gas Acid Mist,

Fluorides etc.

Treated in scrubber before

discharge into the

atmosphere.Captive

Power Plant

Dust and Gas SO2, NOx and

Ash particles

Lime injection for SO2

capture and ESP for fly ash

capture.

Bag House Filters

Bag houses find wide range of application as far as particulate matter collection isconcerned. The dust particles present in a gas stream passed through a bag house

filter are removed first by sieving action of the fabric of the bag and later by

sieving action of pores of the dust layer collected on the surface of the bag.

Mechanical shakers or high pressure air pulse introduced in the opposite directionare used to periodically dislodge dust from the fabric. The efficiency of fabric

filters are normally above 98 percent and can go up to 99.9%.

Ventilation gases from bin and conveyor local ventilations, anode furnace off-

gases during idle and deoxidation stages and ventilation gases from electric slag

cleaning furnace will be cleaned in bag houses. The clean gases will then be ledto the main stack.

Secondary Gas Scrubber

Scrubbers are efficient gas cleaning devices. In a scrubber, a gas stream is passedcounter current to the liquid stream to allow the latter to capture undesirable gases

or particles present in the gas stream. A scrubber will be used for cleaningsecondary gases from the following sources:

The connection between flash smelting furnace and waste heat boiler

Converter secondary hoods

Smelter furnace tap holes

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Launders

Ladle spots

Anode furnace gases during oxidation

The secondary gases will be treated by one stage wet scrubbing using calcium

hydroxide {Ca(OH)2} as the reagent. The efficiency of desulfurization isexpected to be about 99% and the level of SO2 in the exhaust gases is expected tobe 50 ppm. The treated gases will be led to the main stck for venting these into

the atmosphere.

Lime injection and Circulating Fludised - Combustion (CFBC) boiler

To limit the generation of air pollutants from the .. based captive powerplant, 140 T/Hr Circulating Fludised Bed Combustion (CFBC) boiler will be

used. In CFBC boilers, fuel particles in suspension escaping the combustion

chamber of the furnace will be captured by a cyclone and circulated back to the

combustion chamber. This would results in better combustion efficiency andreduction in the particulate matter levels in the exhaust gases. The particulate

matter or fly ash will further be captured by an electrostatic precipitator so that

only a small portion of fly ash is discharged into the atmosphere.

The use of CFCB boiler will also result in low NO x emissions. Under usual

operating conditions of the boiler, 90% of fuel nitrogen will be converted to N 2.The thermal NOx, which is produced at temperatures of 1200 to 1300C, will not

be formed in this case, as the optimum temperature in the fluidised bed is about

850C.

The SO2 emissions from the boiler furnace will be limited by injecting limestoneon the furnace bed. The limestone injection will fix sulfur present in coal into ash

and a very small quantity of SO2 will escape into the atmosphere. Since fly ash isrecirculated into the combustion chamber, lime stone reutilisation for sulfur

fixation will also be very high.

2.2 Liquid Waste Management

The copper smelter and associated plants will generate a number of effluent

streams, which need to be treated before discharging these into a surface waterbody or on land. A discussion on processes resulting in the generation of these

effluent waste streams is provided in Chapter 3. Table 4.2 highlights importantcharacteristics of these waste water streams. These waste water streams will beled to an Effluent Treatment Plant for removing pollutants and bringing the

effluent quality in compliance with the effluent standards. The major focus of

ETP is the conversion of dissolved arsenic and other heavy metals into theinsoluble form and separate these solids from the effluent to be stored adequately.

Table 2.2 : Characteristics of the influent to the Effluent Treatment Plant

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Impurity Concentration (g/l) Quantity (t/yr.)

Sulfuric Acid 12.49 7923.3

Copper 0.06 38.9

Lead 0.06 34.9

Nickel 0.32 204.2

Arsenic 0.43 274.4Cadmium 0.01 6.2

Zinc 0.06 40.6

Iron 0.05 34.0

Mercury 0.00 1.1

Fluorine 0.08 50.2

Chlorine 0.05 33.3

Solids/Inerts 0.12 75.5

Figure 2.1 shows the block diagram of the effluent treatment plant. The ETPconsists of two storage tanks to receive various waste water streams from the

Copper Smelter Project. Each of the two storage tanks will have a capacity of 400m. Tank 1 will receive scrubber and slag granulation waters. Tank 2 will receiveeffluents from the anode casting unit, precious metal plant, refinery and sulfuric

acid plants. The two tanks will be connected to accommodate overflow from each

other. Miscellaneous effluent comprising rain and wash waters will be taken byboth the tanks.

The effluent with controlled concentration of dissolved arsenic (440 mg/l) andacid content of 12 g/l from the storage tanks will be led to three

precipitation/neutralization tanks connected to each other is series so that outflow

from one flows into the next. Each of these tanks will have an operational volume

of 95 m and total volume of 134 m. each of the precipitation/neutralization tankwill be provided with an air injection system which feeds in air and mixes it with

the waste water with the help of an agitator. The latter will also keep the solids in

suspended state. In the first reaction tank, aqueous ferrous sulfate (FeSO4) will beadded and the oxidation of ferrous to ferric state and As +3 to As+5 will be carried

out. Excess iron, about three fold compared with the stoichiometric amount, will

be required for the precipitation of ferric arsenate precipitate. The ferrous sulfatesolution will be prepared by dissolving 23.6 tons of ferrous sulfate hexahydrate

FeSO4 x 7H2O in 60 m of water and agitating the batch. The batch volume may

be adjusted as per the requirement.

In the second and third reaction tank, lime will be added. Sulfuric acid will beneutralized and excess iron precipitated as geothite. Lime milk will be prepared

in a separate tank by mixing slacked lime Ca(OH)2 with water to producesuspension containing about 200 g/l. lime.

As pH of the suspension will rise, dissolved heavy metals will be precipitated ashydroxides. The following reactions provide the basis for the treatment in

neutralization/precipitation tanks.

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H3AsO4 + FeSO4 + Ca(OH)2 + 0.25 O2 FeAsO4 + CaSO4 + 2.5 H2O

HAsO2 + FeSO4 + 1.75 O2 + Ca(OH)2 FeAsO4 + CaSO4 + 1.5 H2O

H2SO4 + Ca(OH)2 CaSO4 + H2O

FeSO4 + Ca(OH)2 + 0.25 O2 CaSO4 + FeOOH + 0.5 H2O

The suspension from the third neutralization/precipitation tank will be fed to the

thickener where flocculant is added to the mixture. In this tank, suspension willbe thickened from 33 g solids/l to 200 g/l. Flocculant solution will be made in the

flocculant. The overflow from the thickener, which contains very less amount of

solids will flow to the circulation tank by gravity and will be used for thepreparation of ferrous solution, lime suspension and flocculant solution. The

excess water in the circulation tank will be pumped to the effluent lagoon and

subsequently filtered by sand filters. Each sand filter will have circulating sandbed, which is continuously cleaned with the help of water and compressed air.The compressed air would lift the dirt from the sand bed. Six sand filters are

envisaged for treating the whole effluent volume. After sand filtration, solids in

the treated effluent are expected to contain less than 30 mg/l solids and complywith the effluent standards. Table 4.3 provides the expected quality of treated

effluent, which will be led into the effluent pond.

Table 2.3 : Expected quality of treated effluent to be stored in the effluent pond

Characteristics Concentration (mg/l)

Copper 3.0Lead 0.1

Nickel 3.0

Arsenic 0.2

Cadmium 2.0

Zinc 5.0

Iron 3.0

Mercury 0.01

Fluorine 2.0

Chlorine 50

Solids 30

The underflow will be pumped to an automatic horizontal plate filter press, which

would be provided with filtration, pressure drying, air drying and discharging

stages. The filtrate will be collected in the filtrate tank. The filter cake will be

taken to the ETP sludge storage place. Although the cake will appear to be dry, itwill contain water about the same weight as solids.

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2.3 Solid Waste Management

The following six types of solid wastes will be generated by the copper smelter

project. Various methods that will be used to dispose off or reutilise these solid

wastes are briefly discussed in this section. The detailed discussion is provided in'Solid Waste Disposal Plan' and 'Phosphogypsum Reutilisation Plan' reports

which are prepared as a part of this EIA and EMP study.

Granulated slag

Filter cake from the effluent treatment plant

Copper/Arsenic precipitate from the refinery

Spent catalyst from the sulfuric acid plant

Fly ash and bottom ash from the captive power plant

Phosphogypsum from the phosphoric acid plant

2.3.1 Granulated slag

Granulated slag will be generated from the flash smelter furnace and Pierce Smithconverter during the copper smelter operation. The amount of granulated slag

produced for 100,000 tons of annual copper production is estimated to be between

82,500 and 115,500 tons. Taking into account the maximum production of115,500 tons of slag with density of 3.6 tons per cubic meter, 1.98 hectares of

area (200m x 90m) has been designated for storing slag up to 5 meter stack

height. This storage space will accommodate the slag production for 2.6 years.Since, the slag has reuse potential, storage need not to be provided for the plant's

life time production. Moreover, the stack height can be increased to

accommodate more slag, if necessary. The storage site will not require any liner,as fajalites and other silicates comprising slag are inert.

The granulated slag could have different uses depending the size of granules.

Being hard and dense, these granules make ideal abrasives. The slag can be usedas substitute for sand blasting, filler for saphalt shingles and black roofing

granules. In addition to exploring market for the above uses, the slag my also be

provided at subsidized rates for subsurface filling of the surrounding villageroads.

2.3.2 Filter cake from the effluent treatment plant

This waste type does not have any reutilisation potential, and hence provisions are

made for safe on-site disposal of the waste produced for the entire life time of the

plant. The latter is assumed to be 30 years. Considering an average annualproduction of 42,600 tons of ETP cake (wet weight), the total quantity of ETP

cake generated in 30 years will be approximately 1.278 million tons. An area of

14.91 hectares (497m x 300m) will be reserved on-site for the disposal/storage ofthe ETP cake.

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The ETP cake would fall under the hazardous waste category as it will contain

Arsenic, Cadmium, Lead and Mercury in quantities higher than limits specifiedthe hazardous waste category of the Hazardous Waste (Management and

Handling) Rules, 1989. To prevent percolation of these heavy metals and other

impurities in the ground water and sub-soil systems, the storage/disposal site forETP cake will have a double layer composite liner along with leachate collection

and removal system (LCRS). Sumps will be provided for both primary and

secondary LCRS for the periodic monitoring of the leachate quality. The leachatewill be circulated back to the effluent treatment plant. The detailed description

about the development of the site for storing the ETP cake is provided in 'the

Solid Waste Disposal Plan' report. This site will be developed in stages, if

necessary.

2.3.3 Copper/Arsenic precipitate from the refinery

The amount of copper/arsenic precipitate or powder produced from the refinery isexpected to be 327 tons per annum with arsenic content being about 96 tons per

annum. This Cu / As precipitate will be stored in PVC drums. These drums willbe stored on-site. Employees handling this waste will be trained for this purpose.

The allocated area for storing these waste containing drums will have restricted

access.

2.3.4 Spent catalyst

Vanadium Pentoxide will be used as a catalyst during the production of sulfuricacid. The annual average change of catalyst is expected to be 51.4 tons. The

spent catalyst will be smelted in the Flash Smelting Furnace in small quantities.

The possibility of selling the spent catalyst back to vendor will be explored.

2.3.5 Ash from the Captive Power Plant

Fly ash

The amount of fly ash generated per year from the lignite based captive power

plant, which needs to be disposed off, is estimated to be about 45,900 tons. Theemphasis will be placed on exploring the market for the utilization of this fly ash

in cement industry. However, on-site storage provision will be made to store the

fly ash for over 2 years to allow for the development of market or accommodateash when the market is sluggish. An area of 1.98 hectares (200m x 90m) will be

reserved for the storage of fly ash produced for 2.18 years.

Although fly ash, depending on its characteristics, can have several potential uses,

focus has been placed on using fly ash in cement industry because of the

following factors:

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Cement industry has the potential to utilize fly ash in bulk quantities.

Cement industry is an organized sector, and doing business with an organized

sector is easier than doing business with an unorganized sector such asconstruction industry or agricultural sector.

Since phosphogypsum that will be produced from the phosphoric acid plant

also has use potential in cement industry, marketing efforts for both fly ash

and phosphogypsum can be combined.

Fly ash is already being used by several cement industries, and there may be more

pressure from the government on the cement industry for using fly ash.

Fly ash when mixed with Calcium Hydroxide (or burnt lime and water)

chemically reacts with the latter to form the same types of binding agents as

Portland cement. Fly ash may be added to Portland cement up to the replacement

level of 20-30 percent. In fact, fly ash addition to cement could have a number oftechnological advantages, which include reduction in water demand, improved

workability, reduction in water segregation, reduction in the heat of hydration,

and therefore, less susceptibility to thermal cracking. Some disadvantages ofmixing fly ash with cement include increase in the initial setting time and

reduction in initial strength even though the ultimate strength after 28 days and 1

year will be the same as Portland cement.

As mentioned above, fly ash characteristics will also determine its use potential in

cement industry. These characteristics are determined by both nature of coal /

lignite used in the captive power plant as well as the type of combustion

technology used. Since the captive power plant will use Circulating Fludised-bedBoiler technology, which has high combustion efficiency, the carbon content of

fly ash will be low. Also, the use of highly pulverized coal will be used in boilerfurnace, which would result in fine particle size fly ash. Both the low carbon

content in and fine particle size of the fly ash will enhance its reactivity, which is

desirable for mixing fly ash with Portland cement.

Moreover, for better quality control, the composition of fly ash will be regularly

monitored to meet the specifications of the cement industry with which the

agreement for selling the fly ash will be signed.

Bottom ash / ash clinker

The bottom ash or ash clinker along with gypsum (produced as a result of lime

injection in the furnace to capture SO2) will be stored on-site. An area of 4.14

hectares (460m x 90m) of land will be kept aside for storing this waste. As thiswaste can not be reused, provision will be made to store this waste for the plant

life, which is taken as 30 years.

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2.3.6 Phosphogypsum from the phosphoric acid plant

The annual production of phosphogypsum from the phosphoric acid plant with theannual production capacity of 1,00,000 tons is expected to be 5,00,000 tons. This

is a huge quantity of waste, which on inadequate disposal could have both

quantitative and qualitative impacts on various environmental componentsdepending on the mode of disposal. Fortunately, phosphogypsum has several

potential uses, which include using it

i) As additive in the manufacture of cement for retarding setting time,

ii) In manufacturing of ammonium sulfate (fertilizer),

iii) As soil additive for alkaline agricultural soils, and

iv) In manufacturing of plaster and plaster boards.

To begin with, the focus will be on the use of phosphogypsum in cement industry,

and the market for the same will be explored.

Phosphogypsum could be added in place of gypsum to cement clinker obtained

from the incineration of finely ground mixture of lime bearing material such ascalcium carbonate with clay or laterite containing aluminium silicate.

Phosphogypsum or gypsum is added to retard the setting time of cement for better

workability. Typically, gypsum or phosphogypsum required to be added to theclinker as a retarder is about 4 percent of the cement produced. Using this as a

basis, the demand for gypsum/phosphogypsum in the cement industry in Gujarat

and adjacent states is estimated to be about 13.72 lakh tons, which could

theoretically accommodate 5 lakh tons of phosphogypsum produced. Moreover,since phosphogypsum needs to be added at the grinding stage of the cement

clinker, phosphpgypsum could be directly supplied to grinding plants.

The replacement of natural (mineral) gypsum by phosphogypsum as a retarder

could have limitations. Due to P2O5 content and fluoride impurities in

phosphogypsum, hydration characteristics of cement could get affected. Theseimpurities, particularly if soluble, delay setting time beyond desirable limits and

also reduce early age compression strengths of cement. Hence, the desirable

quality of phosphogypsum will be maintained so that it is acceptable to the

cement industry. The recommended chemical composition of phosphogypsum forusing it in the cement industry is shown in Table 2.4.

The use of phosphogypsum to convert ammonium carbonate fertilizer toammonium sulfate will also be explored in the long run. In this process,

phosphochalk of equal quantity will be produced which would have to be

disposed off either as a landfilling material or using it in the cement industry.

Table 2.4 : Recommended chemical composition of Phosphogypsum

Constituent Recommended Limit

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Gypsum content (CaSO4 2H2O) > 85%

Lime content (CaO) > 27.5%

Sulfur trioxide content (SO3) > 39.5%

Phosphorous Pentaoxide- P2O5Total < 1.0%

Water soluble < 0.1%Fluorides

Total < 0.3%

Water soluble < 0.1%

Free Chloride < 0.01%

Organic Matter < 0.01%

Gypsum hemihydrate Nil

Free moisture < 2.0%

Even though, emphasis is placed on the use of phosphogypsum, about 11.65hectares of land will be reserved for the on-site storage of phosphogypsum.

About 5 meter high stack at this site can accommodate 2 years of phosphogypsumproduction. If necessary, the stack height could be as high as 18 meters. The sitereserved for storing phosphogypsum will be lined with low density poly-ethylene

(LDPE) sheets to prevent leachate (which may contain F) percolation in the

ground water and subsoil system.

2.4 Greenbelt Development

About 194,526 trees covering 758, 541 square meters of land area (which is about

35 percent of the project site area) will be planted to enhance the environmental

quality. These trees will help in absorbing greenhouse gases and other air

pollutants discharged from the copper smelter project to some extent. The treecover will also improve the aesthetics of the site and act as wind breaker. The

layout of the greenbelt is shown in Figure 4.2.

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