Pollution in Coal Based DRI

Summer Internship Project, 2012Supervised by

Susmita Dasguptasusmita.dasgupta@hotmail.com

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DRI, or directly reduced iron is a method of producing solid iron from

iron oxide

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Iron from iron ore can be• In solid formIn solid form, iron ore can

be 1. DRI produced in coal

based kilns2. HBI produced in gas

based kiln.3. DRI does not need

coking coal at all.

• Or in molten formIn molten form iron can

be produced in the 1. Blast Furnace, needs

coking coal.2. Corex , can use

significant quantities of non coking coal but cannot do away with it totally.

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DRI is preferred in India because of

1. Small scale of production.2. Access to iron ore.3. Paucity of coking coal in India. Between 2004-05 and 2009-10, the DRI

production in India has increased by 24% as compared to only 8% for steel. For steel produced through the coking coal route, the production growth is only 5.5%.

• Source: JPC ,2011.

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In India, 27% of all steel is produced through coal DRI

And 7% of all steel is produced through Gas DRIAnd 20% is through the scrap route.

Source: JPC,2012

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54% OF INDIAN STEEL IS THROUGH THE NON BLAST FURNACE ROUTE.

SOURCE: JPC, 2012.

This means that the DRI segment is a vital constituency of the steel industry.

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India is the world’s largest producer of DRI

India produced 28 million tonnes of DRI in 2010 as against 57 million tonnes of global

production.

Source: World Steel Association, 2012.

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DRI is produced and consumed

locally; being unstable in composition, DRI cannot be exported out or transported

over long distances.Factories are located close to raw material

sources

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No wonder then most DRI plants are located in Odisha,

Jharkhand, Chhattisgarh, West Bengal and Karnataka

Since they are rich in iron ore and

coal.

Source: CSE, 2012.

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DRI Process

Raw materials,

partly coal, iron ore,

fluxes enter the rotary kiln

Rotary kiln= 2.5% Slope and 0.47 rpm speed

Preheating zone or

combustion zone where coal is

heated

Solid iron and unburnt char, lime is discharged

The remainder coal in

powdered form and hot air is

charged

Flue gasAfter Burn Chamber

Cooler discharge and product

separator10

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Paths of Iron and Gas

DRI Route1. Raw material yard2. Crusher, screener3. Rotary kiln4. Recuperator5. Cooler discharge6. Product separator7. Stock house8. Loading points9. Trucks

Reactant Gas route1. Rotary kiln discharge or

combustion end.2. Gas Conditioning tower3. After Burn Chamber4. Gas cleaning plant5. Dust settling chamber6. Waste Heat Recovery

Boiler7. Stack

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Input Output In DRI Plantsper tonne of DRI

Matter Input Output

Solids Iron Ore 6-20 mm : 1500 kgCoal 0-3 mm : 300 kgCoal 3-15 mm: 700 kgLimestone: 0-3 mm: 75 kg

Sponge Iron +3 mm: 790 kgSponge Iron 1-3 mm: 210 kgsSponge Iron -1 mm: 50 kgChar +3mm :30 kgChar 1-3mm: 75 kgChar -1mm:195 kg

Air 6000 Nm3 5000 Nm3

Energy in Gcal = 10 (9)

Coal = 6 Char = 1.15Cooling 0.3Sponge Iron =1.7Waste Heat Recovered = 2.25Unaccounted radioactive = 0.6

Source: http://www.newagepublishers.com/samplechapter/001741.pdf 13

Unfortunately, DRI is a polluting

industryAir, water, solid

wastes containing mainly PM, SO2, NOX and CO abound the

ambient environment.

Source: CPCB,2008

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Garbage Factor for a tonne of sponge iron unit.

INPUT (in Tonnes) OUTPUT (in Tonnes)

1.6-1.75 Iron Ore 1.8-2 Carbon Dioxide

1.2-1.5 Coal 0.25 Dust

0.035-0. 5 Dolomite 0.29 Coal Char

1.5-2 Water 0.02 Kiln accretions

0.2 Sulfur Dioxide with water vapour

Water vapour

Source: Down to Earth, September 16,2006.

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Sources of Air Pollution

Process1. Combustion of coal in the

preheating zone, kiln2. Oxidation of iron ore in the

process zone, kiln3. Flue gas from the kiln

through the upper end.4. Dust of char, unburnt lime,

sulphur, alumina and others through the discharge end.

5. Flue gas through the cap of the After Burn Chamber.

6. Particulate matter from ESP

Fugitive1. Raw material handling and

feeding area.2. Recuperator (in lieu of

WHRB)3. Discharge end and cooler

discharge.4. Product separator.5. Work area of plant.

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Dust Collection CentersSource: CSE 2008

Location Nomenclature

Raw material storage yard Stock house

Coal is crushed for charging as powder Coal Crusher

Iron ore is crushed to fit 5 to 16 mm size Iron crusher

Raw materials sent to plants Transfer points

Sponge iron is cooled by spraying water Cooler discharge

Sponge iron rests before screening and separation Intermediate bin

Sponge iron is separated from char Product separation

Product is stocked Product house17

Norms of Air PollutionSource: CPCB, 2010.

Process• 100 mg/Nm3 for CPCB.• Lower at 86 mg/Nm3 for

Karnataka, 69mg/Nm3 for Chhattisgarh.

Fugitive• 2 mg/Nm3

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Sources of water consumption and pollution

Water consumption1. Rotary kiln cooler.2. Cooler discharge.3. Gas Cooling Water is circulating water

in the sense the water which is used to cool the kilns is again used to cool the coolers of solid discharge and flue gas. Make up water is kept in reserve.

Water pollution1. Cooler discharge contains

solid waste particle.2. Gas coolers also contain solid

particles.3. Some sulphides are mixed

irretrievably into water.4. Water is sprayed on dust

while disposing it off in trucks.

5. Water in gas scrubbing may contain PAH compounds.

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Water Requirement in m3/tonne DRIPurpose Water in m3/tonne DRI Nature of water

Cooling 1.32 Circulating and non contact

ABC 0.48 Direct and contact

Dust suppression 0.30 Direct and contact

Wet Scrubber 0.78 Direct and contact

Total Contact 1.54 To be recycled

Total Circulating 1.32 To be made up

Total Water

Source: CSE, 2008

2.88

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707 kgs/ tonne of DRI is solid waste. Source: CSE,2012

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Solid waste from DRI is wet

dust in the form of sludge

And is mostly allowed to drain out into rivers, ponds, fields.

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Solid waste in DRI PlantsSource CSE, June 2012

Dust Due to Source Percentage of Total Dust

Char Dust Incomplete combustion. Gangue and stony elements.

Rotary kiln, Recuperator 42%

ESP Dust Ash in coal, incomplete waste recovery and gas cleaning.

Stack connected to ESP 24%

Dust Settling Chamber

Impurities in raw materials, incomplete combustion of coal, poor oxidation of ore.

Stack connected to Gas Cleaning Plant, sometimes the Waste Heat Recovery Boiler.

3%

Cooler Discharge and Product Separating area

Due to physical fall of material

Ambient spillage, bag filter 15%

ABC Dust Poor waste heat recovery ABC Cap 5%

Kiln accretions Poor quality coal, non preheated material, over oxidation of iron ore due to presence of sulphur.

Stack connected to kiln 11%

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Standard Norms for discharged effluents. Source: CPCB, 2008.

PARAMETER PERMISSIBLE LIMIT

pH 6.5 ~ 8.5

COD (mg/L) 250

BOD (mg/L) 30

O & G (mg/L) 10

Flouride (mg/L) 5

Hexavalent Chromium (mg/L)

0.1

Iron (mg/L) 3

Total Chromium (mg/L) 2

Manganese (mg/L)

2

TSS (mg/L) 100

Cyanide (mg/L) 0.2

Phenolic Compounds (mg/L) 1

Sulphide (mg/L) 2 24

Pollution from the sponge iron industries is the core reason why

communities rise in arms against this industry.

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Various CSE Reports of 2008 inform us

1. In Odisha, women from the Bonai Vana Suraksha Committee marched up to the District Collector with samples of soil, water and grain to protest against sponge iron plants.

2. Similar protests in Keonjhar and Sundargarh.3. In Chhattisgarh, popular protests led to closure of offending

units and discovery of illegal operators.4. Public protests in Chhatisgarh were around a sudden

increase in respiratory diseases and skin allergies.5. In Andhra Pradesh people filed cases in courts and obtained

compensation for lost kharif crops.6. In Karnataka, there is an ongoing protest in Bellary against

sponge iron industries.

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Blast Furnace vs. DRISource: CSE,2012.

BF must be taken together with Coke Ovens and Sinter Plants

• Raw material consumption in tonnes per tonne of iron = 3.5

• Thermal Energy Consumption = 0.4 ( C0) +0.5 (Sinter/Pellet) + 4.5 (BF) = 5.4 Gcal/ tonne of iron

• Pollution Norms = 50 ( CO) + 100 (Sinter/Pellet) + 150 (BF) = 300 mg/Nm3

Coal based DRI• Raw material consumption

in tonnes per tonne of iron = 5.08

• Thermal Energy Consumption = 7.5Gcal/ tonne

• Pollution Norms = 100 mg/Nm3

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Blast furnaces have higher stack heights due to larger volume

DRI have lower stack due to smaller volumes and hence pollution impact

is higher.28

Interestingly, Coal DRI is one third as much polluting as the Blast FurnaceRaising the stack height might actually help.

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WEST BENGAL CASE STUDY

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Features of sample1. Nearly 95% of sponge iron units in West Bengal have

been considered.2. All plants are declared as red hot.3. Plants occur in clusters like Durgapur, Jamuria and

others in Burdwan; in Bankura, Purulia, Haldia in East Midnapore and in West Midnapore.

4. All plants had run for 720 hours from the last measurement.

5. All plants are coal based DRI, using SL/RN Process.6. Sampling was done for 25 to 30 minutes.

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Data reveals1. Size is not related to flouting of norms. Lower stack heights are not

related to pollution.2. Commonest source of pollution is the kiln area due to combustion and

carbonization faults. This is due to poor quality of raw materials.3. Due to poor combustion, thermal efficiency is low and heat exchange is

also low.4. The existence of pollution control equipment does not guarantee clean

operations. Poor raw material quality may not permit the proper running of facilities.

5. Sulphides lead to higher temperature of flue gas.6. High CO2 interferes in nitrogen cycle leading to high Nox in emissions.7. Sludge is not controlled because of poor commercial reuse value.8. Char is generated due to low quality of coal.

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CSE Study, West Bengal Sponge Iron Industry Clusters November 2011

1. WBPCB fails to control pollution. Irregular monitoring. No enforcement.

2. Factories are repeat and habitual offenders.3. 92% of inspection reports show abnormally high emissions from

the kilns.4. 52% fail to meet emission standards.5. Solid waste management is pathetic.6. Open storage of raw materials a major issue.7. Sponge Iron units do not use the pollution control equipment.

Source: WBPCB,2011.

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West Midnapore, CSE Report

• People’s movement very strong against the sponge iron industry especially Rashmi Cement/ Ispat in 2009, in West Midnapore.

• Maoist politics emerged solely due to pollution from sponge iron plants in West Midnapore.

• Pollution Control Board found gross violation on water, air and solid waste disposal.

• Nagarik Mancha led campaign against Rashmi Ispat.

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Jamuria, Burdwan

• Poor water quality.• Cattle has stopped grazing.• Fish inedible.• Units release pollutants at night from the ABC

cap to avoid inspection.• Due to water shortage in Jamuria, water is not

used as dust suppressant.

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West Bengal Pollution Control Board

• Romita Dutta in Live mint reports that WBPCB has issued closure notice to 50-60 units out of the 250 units in West Bengal.

• More than 40% of the units in West Bengal violate the environment.

• WBPCB claims that night inspection in West Midnapore was stalled because of Maoists.

• According to WBPCB, air pollution has been the main problem.

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CSE Recommendations• Kilns with capacity less than 300 tpd should be

phased out.• Only integrated plants should be allowed in

the future.• Mandatory standards for material handling,

storage and transportation must be enacted.• New cluster based standards should be

imposed.• Stricter enforcement.

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Pollution Control Mechanisms (CSE & CPCB Recommendations)

1. Concrete floor in the work area as well as in the material handling area.

2. Use of covered trucks and enclosed hoppers to transport dust and ash.

3. To put a WHRB after the ABC so that the GCC is avoided.4. Use of ESP instead of the DSC attached to ABC and GCC.5. Use of magnetic separator at the discharge end.6. Use of suction hood, bag filter and ESP to cooler

discharge.7. Use of raw material i.e. coal preheating to reduce energy

consumption and char.8. Use of pellets.

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Our recommendations for waste Utilization in DRI

• Char is used as fuel in thermal power plants, industries and domestic purposes. Coal fines can be mixed with char fines for fuel.

• Dust and fly ash can be made into bricks.• Kiln accretions and slag can be used as landfills and road

making.• Product circuit dust can be used as activated carbon in

edible oil refineries.• Dolchar and char can be used in cement making.• Waste Heat is recovered in captive power plants.• Waste water recycled as make-up water.

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Our Recommendations ( Technical)1. We can set up air quality monitoring stations to track certain specified air

pollutants and toxins. Delhi for example has set up several real time air quality monitoring stations. The system uses Lidar (light detection and ranging) technology, which releases and captures a laser beam and measures the before-after difference to gauge the concentrations of various pollutants in the air.

2. Construction of screen grit chambers to trap the sludge from the effluent through the introduction of de-salting tables to minimize the quantity of salt in the effluent.

3. Use of Sonic Horns, a pneumatically actuated device which produces high pressure acoustic energy or sound waves that are capable of fluidizing powder that adheres to surfaces in the bag filter. This low frequency vibration provides an effective means of cleaning the filter. The FES sonic horn helps in the removal of powder from walls, ceilings, curtain, and filter bags in the dust collector. (http://www.fesintl.com/htmfil.fld/sonichrn.htm )

4. Use of Heat pipe Exchangers instead of WHRB, which can transfer up to 100 times more thermal energy than copper, the best known conductor. Heat pipe is a thermal energy absorbing and transferring system and have no moving parts and hence require minimum maintenance.

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New Gadgets

Heat Pipe Exchanger (HPHE) Sonic Horn

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Our Recommendations (Legal)

• reduction of green house gas by implementation of clean development mechanism (listed by UNDP/GEF) is found to be depend upon the sincerity and integrity of the plant owner.

• Granting land on lease basis with ultimate owner as the community.

• Granting license on term basis to the plant owners.

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Our recommendations (Institutional)

1. Sponge iron industries may come under a cooperative organization for management of waste.

2. Assured quality of raw materials must be provided. Raw material quality must be declared.

3. Pooled resources to set up common facilities towards pelletization, or ore beneficiation, transportation and others.

4. Electronic alarms in the Air monitoring systems (that use LIDAR technology) might be set up on facilities connected to a central computer which shuts operations whenever limits of emission are crossed. This has been CPCB’s recommendation for a long time.

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THANK YOU

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