Case Studies

At Copper India and Zinc Businesses, we have commissioned the Tail Gas Treatment plants at total cost of INR 210 million ($4.8 million) to reduce the SO2 emissions from the acid plant stack by 50% (from 4 kg/tonne to < 2 kg/tonne of sulphuric acid produced). We have adopted the state-of-the-art technology developed by (MESCO), Japan at our zinc smelters to treat the gases using zinc oxide slurry; and zinc sulphate solutions thus produced during the process is recycled back to the hydrometallurgical plant for recovery of metals.

This advanced technology was selected in preference over commonly used and cheaper technologies such as lime scrubbing, which also produce sludge as a hazardous waste

We have adopted Ausmelt technology for lead production at Chanderiya Smelter; which is a state-of-the art technology provided by M/s Cansolv Technologies Inc., Canada. The off-gases from the Ausmelt furnace contain varying percentage of SO2, depending on the process cycle, which cannot be handled directly in acid plant due to its operational limitations.

This process uses the fact that SO2 is absorbed in a cold amine solution and can be easily released from the solution when the SO2 laden solution is heated. By using this ‘circle-type’ process, the SO2 can be separated from the other gaseous parts of the SO2 gas. This separation of SO2 from the other gaseous compounds allows the release of the non-absorbed gases (without SO2) to the atmosphere; and release of concentrated SO2 gas to the sulphuric acid plant.

For the biodiversity conservation at Kolli and Yercaud mines of MALCO, attempts are being made to raise pioneer species and soil binder species like grass, herbs and legumes to enrich the soil. About 11,700 medicinal plants such as Adhatoda (Adhatoda zeylanica) and Chitharathai (Alpinia galanga) have been planted in the reclaimed areas, slopes and among natural vegetation; which had gone lean due to various human activities in the past. Proper manuring of the planted species at regular intervals has also been done. The top soil is stored separately from the areas that were mined. This helps in preventing it from being mixed with debris of lesser nutrient value; retaining its seed bank and utilizing it to top up reclaimed mine areas post screening with 20 mm gravity screen to remove lumps, and enrich its texture and soil fertility. The slopes of the hillocks, on the top plateau of which the bauxite mines are located, have been covered with natural vegetation. Skirting of the mine pits with a barrier of 5-10 m width has been maintained, to avoid disturbance to the natural vegetation patches.

Most of the power generated in India is through thermal power plants given the large coal reserves in the country. We however took the initiative of setting up environment friendly Wind Energy farms. Our first 38 MW Wind Power Project (WPP) was commissioned during March ’07; we have steadily added on this and currently have 123.2 MW of WPP operating at designed levels. These wind energy farms are located in the states of Gujarat & Karnataka in India.

Geo-textiles are thin permeable materials consisting of coir fibres interwoven with nylon filaments to provide support and strength. Initial experiments using geo-textiles were conducted with the technical support of Coir Board, Leraloa. The desired strength to withstand the monsoon was developed after trials conducted over three years.

Geo-textiles reduce the impact of rain on the dump surface, by preventing erosion, conserving moisture and encouraging better plant growth. Use of geo-textiles is now an integral part of our dump management and reclamation procedures at many of our locations.

 

We have conducted extensive R&D for the gainful utilization of slag generated at pyro smelter at Chanderiya Smelting Complex. The R&D studies with premier institutions like National Council for Cement and Building Materials (NCCBM), Central Road Research Institute (CRRI), and Malviya National Institute of Technology (MNIT) indicated safe and beneficial utilization of slag in cement manufacturing and for road construction. Based on this, we have approached cement industries in the proximity of our operations. Post the required approval from the statutory bodies we have successfully utilized the slag in cement manufacturing. This has ensured that the old stockpile accumulated since its inception (1990) has been reduced considerably and the whole endeavor has resulted in overall reduction of our waste footprint and is our first step towards establishing an industrial ecology.

With these efforts, more than 6,15,000 MT of slag were consumed by the cement manufacturers as on 31st March 2010 and around 40 ha of land has become free for other use.

These efforts are continuing and the entire stock will be liquidated during the financial year 2011.

To combat global warming, SIIL took up a unique initiative – by utilizing process waste heat to generate 11.2 MW of electricity. There were inherent process risks associated with implementing a waste heat recovery boiler in the copper smelter. However, Sterlite successfully implemented this project.

Waste gases coming out of the copper smelter at a temperature of 1,044 oC is allowed to pass through a waste heat recovery boiler. By utilizing the thermal energy from waste gases, the boiler – with operating pressure of 70 bars and temperature 285 oC – generates 45 TPH of steam. The temperature of the steam is further increased by the super heater to enhance its thermal energy. The super heater utilizes the furnace oil to increase the temperature of steam to 485 oC and 64.4 bar pressure. The steam generated is used to drive the turbine with 11.2 MW rated capacity.

Thus the activity utilizes waste heat recovery technology to generate electricity, which displaces grid import. Thereby reducing greenhouse gas emissions from the grid connected to fossil fuel-based power plants. It was successfully registered as a CDM project in the United Nations Framework Convention on Climate Change (UNFCCC) in December 2009 having a CER potential of 18,000 tonne of equivalent CO2/ year. Three more CDM projects have been identified at SIIL having potential CERs of 65,000 per annum.

In continuation to our commitment towards environment protection and preservation of natural resources, boiler has been installed utilizing heat of LCV (low calorific value) gases generating from pyro zinc operation which were otherwise being flared in stack.

In Imperial Smelting furnace of pyro zinc operation, sintered lumps of zinc and lead oxide are charged with the preheated coke. During burning process of coke a volume of around 65 to 70 KNM3/H (LCV) gas is getting generated of which approx. 42 KNM3/H is consumed for preheating the coke and blast air. Remaining 23 to 25 KNM3/H was being flared in stack. Now this cleaned gas is utilized for generating steam by installing boiler. This project is presently under CDM registration having a CER potential of 33,000 tonne of equivalent CO2/ year.