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

Transcription

1 3 rd International Conference on ALTERNATE FUELS AND RAW MATERIALS IN CEMENT INDUSTRY Organized by Cement Manufacturers Association India th March, 2017 Circular Economy: Spent Pot Lining an Alternate Fuel In Cement Industries Jawaharlal Nehru Aluminium Research Development & Design Centre, Nagpur

2 Circular Economy The circular economy aims to eradicate waste not just from manufacturing processes, as lean management aspires to do, but systematically, throughout the life cycles and uses of products and their components. Importance of circular economy Creating growth opportunities Reduce waste Drive productivity Deliver competitive economy Address resource security/scarcity Reduce environmental impacts

3 New Capacities of Aluminium Production: Asia to Dominate

4 Future of Aluminium

5 Forecast of SPL generation

6 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 and profitability are the concerns of business Challenge is to balance environmental protection and economic interest

7 International R&D In a preliminary study undertaken by Central Queensland University, Australia (CQU) research group in 2013, different fuels were evaluated based on the data available for their suitability in cement kiln. The study showed that SPL is one of the most promising candidates for further research*. It is proposed that a blend of AFs and fossil fuel can be used in different proportions for characterising the fuel for its performance under different operating conditions 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: , pp , 2013

8 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, SO 2, NO X, and CO emissions & dusty kilns Final clinker composition since the combustion byproducts 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

9 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

10 Origin of Spent Pot Linings (SPL) Hazardous Waste from Aluminium Industry Kg/ton of Aluminiu m Spent Pot Linings Dross (Primary) Dross (Secondary) 80

11 Hierarchy of SPL waste

12 Composition of SPL Sn Component 1 st cut carbonaceous(56%) 1 Carbon Total Fluoride (50-50) nd cut Refractory(44%) 3 Free Al 2 O Metallic Al Calcium, CaO Quartz, SiO Phosphorus, P g/t g/t 8 Sulphur, S Total Sodium, Na (40-60) Moisture Total Cyanide, CN Free Cyanide, CN

13 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.)

14 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 is used as AF in a cement kiln SPL would also be a supplement of raw materials such as silica, alumina and ferrous components. SPL has high fluorine content, and hence handling and transportation 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 D. Mikša, M. Homšak, N. Samec, Spent potlining utilisation possibilities, Waste Manage Res, Vol. 21, 2003, pp R.L. Kohnen, Disposal options for spent potliner, ERAtech Publications, eratech.com/ papers/disposalspl.html, viewed on 23rd February, 2012.

15 Added Advantages of SPL as a AF* SPL has high levels of fluorides, sodium and carbon, which are potentially valuable in industries like cement manufacture, where large energy inputs are required. Fluoride present is beneficial for reducing temperature of Clinker 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 kiln exhaust and fixed in the clinker as Fluorspar (CaF 2 ). Na can be beneficial if operating fuel has high amonut of S. Ammonia & Cyanide components present in SPL acts to reduce Nitrous Oxide (NO 2 ) emissions from the cement kiln by up to 1/3 rd, and outcomes are non-hazardous, thereby falling in emission norms of Cement plants. *2 nd meeting of Cement/Aluminium industry task force

16 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, CaF 2... 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 CaF 2 Product can be land filled at a hazardous waste site BEFESA UK Co-processing of SPL and salt cake from dross

17 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, sp, viewed on 1st March, 2012 Alcoa in Australia: Environmental Management: Waste, 2012, com/australia/en/info_page/environ_waste.asp, viewed on 1st March, 2012

18 Indian Scenario SPL 70,000 tons per annum Clinker production 350 million tonnes per annum World s practice 20kg of SPL-derived products for each tonne of clinker 7 million tonnes of SPL-derived products can be consumed by the cement industry

19 SPL Technology Developed by JNARDDC for NALCO /VEDANTA Electrically heated rotary tube furnace at JNARDDC Heat Treatment of SPL SPL processing Material balance Bench Scale Unit at JNARDDC

20 Indian Cement Industries- Barriers to SPL as AF Sizing, Hardness & crushability: Very hard to crush and with Bond work index of 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

21 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 a hazardous waste material that can be transformed and safely re-used by the cement industry, resulting in a closed industrial ecosystem where waste from one industry becomes feedstock for another.

22 Thank You Anupam Agnihotri Director Jawaharlal Nehru Aluminium Research Development & Design Centre, Nagpur