Circular Economy: Spent Pot Lining an Alternate Fuel In Cement Industries

Jawaharlal Nehru Aluminium Research Development & Design Centre, Nagpur

3rd International Conference on ALTERNATE FUELS AND RAW MATERIALS IN CEMENT INDUSTRY

Organized by Cement Manufacturers’ Association India23-24th March, 2017

Circular EconomyThe circular economy aims to eradicate waste—not just frommanufacturing processes, as lean management aspires to do, butsystematically, throughout the life cycles and uses of products andtheir components.

Importance of circular economy•Creating growth opportunities•Reduce waste•Drive productivity•Deliver competitive economy•Address resource security/scarcity•Reduce environmental impacts

New Capacities of Aluminium Production: Asia to Dominate

Future of Aluminium

Forecast of SPL generation

Need for Alternate Fuel

• Greenhouse gases and global warming

• Efficient use of non-renewable fossil fuels &toxic residues

• Reduce contamination of water and soil

• Cost competitiveness, global competition andprofitability are the concerns of business

• Challenge is to balance environmentalprotection and economic interest

International R&D• In a preliminary study undertaken by Central

Queensland University, Australia (CQU) researchgroup in 2013, different fuels were evaluated basedon the data available for their suitability in cementkiln.

• The study showed that SPL is one of the mostpromising candidates for further research*.

• It is proposed that a blend of AFs and fossil fuel canbe used in different proportions for characterising thefuel for its performance under different operatingconditions in a kiln of a local industry.

*Industrial Waste as Alternative Fuel in Cement Industry: Its Impact on Environment

Recent Researches in Environmental and Geological Sciences ISBN: 978-1-61804-110-4, pp 108-114, 2013

AF Advantages & Disadvantages• Cheaper than fossil fuels (FF+AF optimal

proportion)

• Preservation of non-renewable energy sources

• Reduction of waste disposal sites

• Different Characteristics than conventional fuels:

– Heat ducts, SO2, NOX, and CO emissions & dusty kilns……

• Final clinker composition since the combustion by-products are incorporated into clinker

• Initial investment costs associated with adjustment or replacement of burner

• Establishment of AF delivery systems

• New fuel storage and distribution facilities

Criteria of AF • NO criteria for SPL as AF by Indian Cement industry

• Economics, availability, toxicity, volatiles, grindability, emissions

• Specific criteria to be defined for setting material AF – Energy ……………… (14 MJ/kg) (25.2 MJ/kg)

– Chlorine …………….(<0.2 %) (BDL)

– Sulphur ……………..(<2.5 %) (0.1%)

– Polychlorinated Biphenyls ( < 50 ppm)….(BDL)

• Heavy metals …<2500 ppm{Hg(10), [Cd+Tl+Hg]<100)…. (BDL)

• Content of circulating elements (Na, K, Cl, S)

• Other properties for even fuel combustion– Even particle size distribution

– High and uniform calorific value

– Free of detrimental contents like metals, glass, minerals

– Low moisture content

Origin of Spent Pot Linings (SPL)Hazardous Waste from Aluminium

Industry

Kg/ton of Aluminiu

m

Spent Pot Linings 20-30

Dross (Primary) 15-30

Dross (Secondary) 80

Hierarchy of SPL waste

Composition of SPLSn Component 1st cut

carbonaceous(56%)2nd cut Refractory(44%)

1 Carbon 40 - 75 0 - 20

2 Total Fluoride (50-50)

10-20 4-10

3 Free Al2O3 0-15 10-50

4 Metallic Al 0-5 --

5 Calcium, CaO 1 - 6 1- 8

6 Quartz, SiO2 0-6 10-50

7 Phosphorus, P 0-650 g/t 0-300 g/t

8 Sulphur, S 0.1 0.1

9 Total Sodium, Na (40-60)

5-15 1-5

10 Moisture 1-5 1-2

11 Total Cyanide, CN 0.01-0.5 0 – 0.01

12 Free Cyanide, CN 0 – 0.1 0 – 0.05

SPL Treatment Best Available Techniques(BAT)

• Stricter environmental and safety regulations make SPL acceptable for

–Use in cement manufacture

–Use as a carburiser in the steel and ferro-alloy industry

–Use as a secondary raw material (rock wool, salt slag recovery, etc.)

SPL as an AF• Heating value of SPL is 25.2 MJ/kg equivalent to

bituminous coal

• The total SPL generation in India is 70,000 tons /annum which implies the availability of SPL as AF

• Almost 99.9% of the cyanide is destroyed when it isused as AF in a cement kiln

• SPL would also be a supplement of raw materials suchas silica, alumina and ferrous components.

• SPL has high fluorine content, and hence handling andtransportation of SPL could be an issue.

•D. Lechtenberg, Spent cell linings from the aluminium smelting process as an alternative fuel and raw material for cement production, Global Cement Magazine, January 2009, pp. 36-37.•D. Mikša, M. Homšak, N. Samec, Spent potlining utilisation possibilities, Waste Manage Res, Vol. 21, 2003, pp. 467– 473.•R.L. Kohnen, Disposal options for spent potliner, ERAtech Publications, http://www. eratech.com/ papers/DisposalSPL.html, viewed on 23rd February, 2012.

Added Advantages of SPL as a AF*• SPL has high levels of fluorides, sodium and carbon, which

are potentially valuable in industries like cementmanufacture, where large energy inputs are required.

• Fluoride present is beneficial for reducing temperature ofClinker by fluxing action from 1450°C to 1350°C.

• Due to presence of large quantities of lime & Limestone,virtually all gaseous fluoride is scrubbed from the kilnexhaust and fixed in the clinker as Fluorspar (CaF2).

• Na can be beneficial if operating fuel has high amonut of S.

• Ammonia & Cyanide components present in SPL acts toreduce Nitrous Oxide (NO2) emissions from the cement kilnby up to 1/3rd, and outcomes are non-hazardous, therebyfalling in emission norms of Cement plants.

*2nd meeting of Cement/Aluminium industry task force

Treatment of SPL -Examples

• Rito Tinto Alcan –Saguenay , Quebec, Canada– Capacity 80,000 tons/year of SPL– Process based on treatment of SPL with water and acidic

and basic solutions– Products: Carbon, CaF2.......

• Alcoa –Gum Springs, Arizona, USA– SPL mixed with lime and calcium silicate and treated in a

furnace at >700°C– Cyanides are destroyed, and fluorides bound in CaF2

– Product can be land filled at a hazardous waste site

• BEFESA –UK– Co-processing of SPL and salt cake from dross

Treatment of SPL -Examples

• U.S.-generated SPL was recycled up to 79% in cement kilns in 2010

• In 2009, 7449 tones of SPL were recycled in Australia, mostly in cement industry as AF

•Alcoa Worldwide Sustainability: Sustainability of Operations: Environmental: Emissions & Waste, 2012, http://www.alcoa.com/sustainability/en/info_page/operations_env_emissions .a sp, viewed on 1st March, 2012•Alcoa in Australia: Environmental Management: Waste, 2012, http://www.alcoa.com/australia/en/info_page/environ_waste.asp, viewed on 1st March, 2012

Indian Scenario• SPL 70,000 tons per annum

• Clinker production 350 million tonnesper annum

• World’s practice 20kg of SPL-derivedproducts for each tonne of clinker

• 7 million tonnes of SPL-derived productscan be consumed by the cementindustry

SPL Technology Developed by JNARDDC for NALCO /VEDANTA

Bench Scale Unit at JNARDDC

Electrically heated rotary tube furnace at JNARDDC

SPL processing Material balance

Heat Treatment of SPL

Indian Cement Industries- Barriers to SPL as AF

• Sizing, Hardness & crushability: Very hard to crush and with Bond work index of 40-45 kWh/t [HGI 44 (As it is), 55 (wash)]

• Variability (Homogenisation): Cement clinkering process is sensitive to small changes in the addition rate of F and Na.

• Process & maintenance impact: Abrasive, high & variable content of Na and F with high ignition temperature of carbon

• Willingness to pay for co-processing/proper disposal of SPL

• Continuous availability

• Clearance from CPCB, lack of directives from regulatory authority , friendly disposal of SPL

• Waste quantification and national database on SPL

• Safety & Transportation

Concluding Remark• R&D group at JNARDDC, Nagpur looks at SPL as a

strategic material as opposed to a hazardous waste.

• Better waste management required to deal with SPL, rather than landfilling.

• The way forward is to use SPL in value added applications, ensuring proper waste handling and disposal and making the environment cleaner/safer.

• Aluminium smelter Spent Pot lining (SPL) is ahazardous waste material that can be transformedand safely re-used by the cement industry, resultingin a closed “industrial ecosystem” where wastefrom one industry becomes feedstock for another.

Thank YouAnupam Agnihotri

Director

Jawaharlal Nehru Aluminium ResearchDevelopment & Design Centre, Nagpur

director@jnarddc.gov.in+91 7104220763+91 9404084435

www.jnarddc.gov.in