Low Carbon FootprintMetal Extraction

• Sricharan Sunder (09MT3008)• Piyush Verma (09MT3018)• Kislaya Dubey (09MT1006)

Department of Metallurgical and Materials EngineeringIndian Institute of Technology, Kharagpur

A measure of the total amount of carbon dioxide (CO2) and methane (CH4) emissions of a defined population, system or activity, considering all relevant sources, sinks and storage within the spatial and temporal boundary of the population, system or activity of interest. Calculated as carbon dioxide equivalent (CO2e) using the relevant 100-year global warming potential (GWP100)

What is Carbon Footprint

Why we need to reduce ?

• The accumulation of carbon dioxide in the environment is recognized as a major contributor to the Global Warming Problem caused by this Green House Gas.

• The main influences on carbon footprints include population, economic output, and energy and carbon intensity of the economy.

Where should the focus be?

•By adopting techniques that use non carbon containing fuels such that carbon dioxide is not formed anywhere in between its production .

•Minimizing the number of steps in a Metal production such that fuel consumption is reduced if we have to use a Carbon-Fuel.

Introduction

• Increasing demand for metals, declining ore grades and complex new deposits are all contributing to an increase in greenhouse emissions from primary metal production.

• As a result, the mineral processing and metal production sector is coming under increasing pressure to reduce its energy consumption and GHG emissions and improve the overall sustainability of its operations.

World metal production and ore processing rates (MT/year)

Copper Nickel Lead Zinc Iron/steel

Aluminium

Current Metal 15.5 1.4 8.7 11.7 1327 36.3

Ore 1914 111 193 260 2633 202

2030 Metal 31.4 2.7 14.8 19.2 2540 78.0

Ore 4984 273 411 533 5040 434

Global Energy Consumption and Associated Carbon emission

Discussion

• Number of technologies under development in the metal extraction stage of Iron/Steel and Aluminium which may realize some of the opportunities for reducing the energy and greenhouse footprints of primary metal production.

• Mineral processing offers less opportunities for reducing energy consumption and greenhouse gas emissions compared to metal extraction.

• New technologies producing energy savings if incorporated optimally into comminution circuits e.g.

Stirred mills.High pressure grinding rolls.

• These technologies in combination with others (e.g. improved circuit design), may possibly achieve the 50% improvement in energy efficiency for comminution.

METAL EXTRACTION TECHNIQUES LOWERING C-Footprint

Steel production

Charcoal from biomass

1. Woodchar or biomass char is considered renewable because the carbon cycle via wood ( biomass)is very short (5–10 years) compared to fossil coal (approximately 100 million years).

2. Coke contributes 75% to the GHG emissions from steel production . Replacement of coke with charcoal derived from biomass would reduce GHG, as the biomass comes with a greenhouse gas credit due to the carbon dioxide sequestered during its formation.

• Impossible to operate large blast furnaces with 100% substitution of charcoal-lower crushing strength,(20% being considered practical.)

• Other Methods to Reduce Carbon footprint in Steel making

•  Dry granulation of slag

• Bath smelting – HIsmelt

Al production

• Using Drained cathodes• The use of aluminium-wetted and drained

cathodes will enable a reduction in the thickness of the metal pad, which will allow ultimate stability of this interface to be achieved. anode-to-cathode distance (ACD) is also reduced, thereby producing a lower cell voltage. The lower cell voltage and higher current efficiency will reduce the power consumption of the cell.

Comminution

 High pressure grinding rolls• Since its first commercial application in 1985,

high pressure grinding rolls have become a near standard unit operation for pre-grinding cement clinker, and grinding of raw materials such as slag, coal and lime in the cement industry. It has subsequently been utilised in the diamond industry for selective liberation. The broader use of high pressure grinding rolls for metalliferous minerals has only been considered more recently. Initial concerns over wear rate of the rolls have been addressed, and as a result there are strong signs of increasing interest, particularly in the processing of gold, copper and iron ores. While energy reductions in the order of 30–50% have been suggested for the high pressure grinding rolls based on cement industry experience, reductions in the order of 20% are more likely for metalliferous ores 

Stirred Mills

• Three stirred mill types have gained industry acceptance for fine and ultra-fine grinding duties, ie., the tower mill, the detritor mill and the IsaMill. The first two mills are vertical stirred mills with steel spirals and long pins respectively to agitate the mill charge, while the latter mill is a large horizontal stirred mill with discs as stirrers. The major advantage of stirred mills over traditional ball mills are their ability to effectively use smaller grinding media for fine and ultra-fine grinding to achieve high energy efficiency at high mill throughput . It has been reported that stirred mills are up to 50% more energy-efficient than conventional ball mills for products finer than 100 μm

Conclusions• The results from a number of life cycle

assessments of primary metal production processes, together with predicted future ore grades, metal production rates and liberation size, have been used to show that endeavours to reduce the energy consumption and associated GHG emissions from primary metal production should mainly focus on the metal extraction stage of the metal life cycle, and that there is considerable scope to make significant reductions here, particularly for steel and aluminium. While the contribution of the mining and mineral processing stage to energy consumption and GHG emissions can be expected to increase in the future as a result of a deterioration in the quality of ores, and will present opportunities for reducing these impacts by improving the energy efficiency of comminution, these opportunities will still be appreciably less than those from the metal extraction and refining stage

References

• Wikipedia• Sciencedirect• Images taken from Google Images

and Sciencedirect.

Thank You