Gunning for lower downtime
Gunning for lower downtime

Gunning for lower downtime

For minimising downtime, techniques like gunning and shotcreting are being adopted, instead of using pre-fired bricks in refractories.

Portland cement manufacturing is an energy intensive operation, and a refractory lining that can withstand high temperatures, alkalinity and corrosive conditions is absolutely essential.

Refractories play a critical role in both the rotary kiln lining, and the lining of the high volume static equipment areas that comprise a modern pre-calciner kiln system. The refractory kiln process involves pyro-processing of raw material, and extremely high temperature in rotary kilns. Often the kiln feeds are alkaline in nature, generate corrosive reactants. Hence the importance of refractories with strong resistance to such characteristics and having robust thermal efficiencies in cement manufacturing. 'After two years of depressed market, currently refractory market has stabilised a bit and it seems that recovery is underway in 2018,' says Ish Mohan Garg, Managing Director, Calderys.

While iron and steel industry is the major consumer of refractories with 65-75 per cent share, cement is the second major consumer of the equipment with 10-15 per cent share of total refractory consumed, followed by glass, non-ferrous metals, petrochemicals and hydrocarbons, which also involve high temperature processes.

Imports
About 30 per cent of refractories consumed in India is imported, mostly from China. 'The primary driver for these imports is the abundant availability of raw material there, especially magnesite. To that extent, we cannot wish away the role of China and this is also the reason why refractory companies have set up plants in China,' says Sameer Nagpal, CEO, Dalmia-OCL. However, the recent raw material crisis in China provides immense opportunity for India to bolster its domestic refractory industry by allowing it to source and secure raw materials from other countries with zero import duty.

But, certain policy anomalies have to be corrected to achieve this, says Garg. 'Refractory is essentially a "Make in India" business model where we import raw materials and create value-added products in India. But while import duty on raw material is 5 per cent, that on finished product is 2.5 per cent. This import duty has to be increased to encourage domestic manufacturing activity.'

With India becoming the world's second largest steel and cement producer, it should also be a leading refractory producer to support these industries. 'Indian companies have the wherewithal to emerge as a globally competitive player and we are actively pursuing this direction. We are looking at acquisitions in Europe that can help us build scale and access latest technologies,' says Nagpal.

'Due to its low-cost and highly skilled workforce, India is a competitive market for refractory manufacturing and is also a sourcing base for Americas and Europe,' Nagpal adds. Dalmia-OCL has a network spread across different countries and exports constitute 15 per cent of its revenue.

However, Garg differs on competitiveness of the Indian refractory industry. 'Raw materials being 60-70 per cent of the total cost of refractory makes it difficult for Indian refractory industry to become globally competitive, due to sheer dependence of Indian manufacturers on imported raw materials. As a country, our ability to tap into global/ regional market is very much restricted,' he points out.

Technology
As cement demand picks up and capacity utilisation goes up, cement manufacturers may want to minimise the downtime for replacing refractory lining. 'This is giving rise to demand for higher performing bricks with higher life and shorter application time. Techniques like gunning and shotcreting using monolithic refractory, which is in powder form and takes shape after being applied, instead of using pre-fired bricks, is also gaining currency,' says Nagpal.

Dalmia-OCL has formed a joint venture with a leading European refractory company for bringing to India the latest in gunning and shotcreting products, and is setting up the most modern monolithic plant in Katni, Madhya Pradesh.

Also, Indian cement makers use a lot of alternative fuels, which puts tremendous thermochemical pressure on refractory. Hence second or third generation spinels, hybrid refractories are coming up to take care of the increased thermochemical loads. Another trend is the effort towards reduction of thermal losses by introducing energy-saving refractories. New concepts are also coming up on thermal insulation of pyro system.

In the past, the major focus had been on the kiln performance, primarily productivity but with stricter environmental norm there has been major shift on the cement kiln system refractories too. 'Well known hexavalent chrome problem associated with Mag Chrome refractories has made them unusable in cement kiln. In the kiln burning zone, Mag Chrome bricks have been substituted by wide range of alternate spinel products, e.g. MagAl, Hercenyte and others like zirconia containing magnesia, etc.,' says Garg of Calderys.

Ammonia injection, once stricter NOx and SOx norms is implemented, would put significantly more stress on the refractory in the cement kiln system. Refractory manufacturers need to gear up for these upcoming regulatory norms.

Cement kilns in India are virtually being used as incinerator, where pharma and municipal wastes are common feed as fuel. This obviously has changed the kiln operating environment. This has resulted in increased coating build in kiln inlet as well as Spurrite ring formation within the kiln. On many occasions, the clinker is dustier compared to the past. 'These changes obviously have called for refractories with different features. Incorporation of the requisite features has turned out to be much easier in monolithic, primarily castables, compared to bricks. Against this backdrop, castable in kiln inlet, tip casting, bull nose and cooler bench has become a standard practice. With the advent of shotcrete installation process, for identical castable formulations, faster installation extension of refractory life, by repair, has been possible,' says Garg.

Boost domestic manufacturing
While emphasising the need to boost local refractory manufacturing, Nagpal of Dalmia-OCL suggested reduction of duties on raw material import; enabling mining policies for minor minerals like bauxite, quartzite, magnesite, etc., which are critical refractory raw materials, to reduce dependence on external sources; and support to refractory and ceramics R&D to boost local innovation, for this purpose.

The primary support from government should be on the following three fronts - 'technology development, developing young talent and sustainability,' says Garg of Calderys.

On behalf of IRMA, Calderys has set up Centre of Excellence at IIT BHU aimed at technological advances for making industry globally competitive. 'We need to accelerate such advances in multiple Institute of repute,' Garg adds.

For decades, the industry has been dumping used refractory in landfills, however, more sustainable way is to extract key raw materials from the same, use it again for refractory. 'We trust Government should work with user industry to enable reverse supply chain of used refractory,' says Garg.

-BS SRINIVASALU REDDY

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