Efficiency Priority

Metals industry exceeds targets under PAT

The metals and mining industry is a key contributor to the country’s economy as its output is used across sectors such as construction, power, automobile, defence and aerospace. Higher government spending on infrastructure, ambitious schemes in the power sector and increasing exports are expected to significantly drive demand in the metals and mining industry.

However, increase in raw material prices, intense global competition and a decline in sales realisations are putting pressure on the balance sheets of the metals industry. The optimisation of energy costs, which form a major component of input costs for these industries, is crucial for ensuring sustainable, cost-effective and environment-friendly operations.

For instance, aluminium manufacturing is an energy-intensive process. Smelting, which involves extracting aluminium from its oxide, alumina, accounts for 85-90 per cent of the total electrical energy consumed by the manufacturing plant. Similarly, iron and steel manufacturing also requires a large amount of energy. The specific energy consumption of large integrated steel plants in the country is 6.5-7.0 Giga calories (GCal) per tonne of crude steel as against the international norm of 4.5–5.5 GCal per tonne. One of the key initiatives for reducing energy consumption in the metals and mining industry has been the Ministry of Power’s (MoP)  perform, achieve and trade (PAT) scheme launched in March 2012. In the first PAT cycle, designated consumers (DCs) from the aluminum and iron and steel industries took noteworthy energy conservation initiatives to reduce their specific energy consumption. Together, they achieved one-third of the cumulative savings of 8.67 million tonnes of oil equivalent (mtoe) under PAT Cycle-I.

In addition, metal manufacturing leads to a significant emission of greenhouse gases and other pollutants. The steel industry contributes about 30 per cent of the total industrial emissions. However, given the country’s commitment to reduce carbon emissions at the Paris Summit 2015, there is an urgent need for the metal industry to adopt emission control technologies.

PAT I

In the first cycle of PAT (compliance period 2012-13 to 2014-15), a total of 77 DCs were covered in the iron and steel and aluminium industries. These include Hindalco Industries, Vedanta Aluminium, National Aluminium Company, Essar Steel, SAIL, Rashtriya Ispat Nigam Limited and Tata Steel.

The threshold energy consumption limit for a DC in the aluminum sector was 7,500 tonnes of oil equivalent and based on this, 10 DCs were selected in the first cycle. With an annual energy consumption of about 7.7 mtoe, these consumers accounted for 4.7 per cent of the total energy consumed by DCs across all sectors. By the end of the first cycle (2014-15), the DCs achieved energy savings of 0.73 mtoe, about 60 per cent higher than the MoP’s target of 0.46 mtoe.

In the iron and steel sector, 67 plants with a total annual energy consumption of 25.32 mtoe were included in the scheme. The energy consumption limit for these DCs in this sector was 30,000 tonnes of oil equivalent per annum. At the end of the first PAT cycle, the DCs in the industry achieved energy savings of 2.10 mtoe, 41 per cent higher than the target of 1.5 mtoe.

PAT Cycles II and III

Under PAT Cycle II (compliance period 2016-17 to 2018-19), four more DCs have been included from the iron and steel sector taking the total to 71, and two have been added in the aluminium sector, taking the total number to 12. The total energy saving target in this cycle is 8.869 mtoe till 2018-19, of which 0.57 mtoe is to be achieved by DCs in the aluminium sector and 2.14 mtoe by those in the iron and steel sector.

Further, the PAT scheme is being implemented on a rolling basis, with new DCs being added every year. The next cycle, PAT III (compliance period 2017-18 to 2019-20) was notified on March 30, 2017 with the inclusion of 116 new DCs. From the aluminum sector, one new consumer was added in this cycle and from the iron and steel sector 29 new consumers were added with energy saving targets of 0.06 mtoe and 0.41 mtoe respectively.

Energy saving initiatives

Under PAT I, the DCs in the aluminium sector implemented several energy saving measures entailing a total investment of Rs 1.4 billion. These include the deployment of slotted anodes in pots through in-house design engineering and optimisation of stubs; the use of indigenously formulated fuel additive for dozing inside the furnace; and the installation of intelligent soot blowing systems, variable frequency drives and high efficiency screw compressors. Besides, the DCs adopted better operational practices like stoppage of driers in service air system, interconnection of pumps, installation of efficient pumping systems, modification of the compressed air system, and renovation and modernisation of captive power plants.

The DCs in the iron and steel sector also executed significant energy saving initiatives such as the use of pellets in the burden material, which helped bring down coal consumption, improve metallisation of pellets, reduce the fines and prevent the loss of iron ore. The installation of a high top pressure blast furnace also helped recover energy from large volumes of pressurised top gas. Also, top pressure recovery turbines can be installed to generate electricity from this high pressure.

In addition, waste heat recovery from the direct reduced iron process significantly reduced the need for external fuel like coal. Further, direct rolling of a hot continuous cast billet to produce thermo-mechanically treated bars prevented the use of furnace oil in the reheating furnace. Coke dry quenching helped in the recovery of waste heat to produce steam and power apart from providing environmental benefits such as the reduction of dust, SOx and NOx emissions.

Emission management

In an energy-intensive industry, emissions management is also a key priority area. As per the Centre for Science and Energy, the carbon dioxide emissions from the iron and steel industry are projected to nearly double from 227 million tonnes (mt) in 2011 to 415 mt in 2020.

The industry is currently covered under the Environment Protection Act (EPA) and the Environment (Protection) Rules, 1986, of the Ministry of Environment, Forest and Climate Change. Under the EPA, entrepreneurs are required to obtain statutory clearances from the central and state governments for the setting up or expansion of iron and steel plants.

Some of the key measures taken by the industry to reduce its emissions have been the use of variable oven pressure regulation technology and high pressure ammonia liquor aspiration in the coke oven. Besides, the control of particulate and dust emissions is being taken care of during raw material handling and processing. Simple steps like dust suppression by water sprinkling, installation of a dry fog system and use of covered conveyors is being taken up for controlling fugitive emissions.

The emission of dioxins and furans from the sintering unit is being controlled with the use of activated carbon in flue gas stream, reduction of chlorine content in the feed, and installation of fabric filters with catalytic oxidation systems. Further, effluent treatment plants are being installed to get rid of the effluents discharged from the blast furnace. These contain nitrogen, suspended solids and metallurgical waste.

Similarly, the aluminium manufacturing process involves the emission of perfluorocarbons, carbon dioxide, sulphur dioxide and hydrogen fluoride gas. For controlling these, scrubbers, dry fume control and fluoride recovery systems, inert anodes instead of traditional baked carbon anodes, and fabric filters or electrostatic precipitators are being deployed by the industry. Industry players have also installed online emission and effluent monitoring systems to transmit real-time data to the pollution control board.

Summing up

Energy efficiency is essential for optimising the energy requirements of the metals industry. The PAT scheme further incentivises energy efficiency improvement through the trading of energy saving certificates, which can generate additional revenue for the consumers.

Industry players have the financial and technical capability to adopt advanced technologies that entail slightly higher investment and longer payback period. The implementation of emission control measures will create a positive impact on the environment and render a green image to these industries. Overall, energy and emission management can help the industries meet their long-term energy demand in a cost-effective manner, while mitigating environmental and climate threats.

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