The Indian cement industry has realised that strong business growth can be achieved by sustaining manufacturing in an eco-friendly manner. As the industry is moving ahead to embrace green technologies, SP Deolkar, a veteran in the field, lists out some of the obstacles in its path.

Cement entrepreneurs have to face many challenges while setting up new cement manufacturing plants on greenfield sites. Emphasis on sustainable development is a new dimension to consider while designing the plant. The cement industry is committed to reducing emission of Greenhouse Gasses (GHG) and to save limestone reserves and fossil fuels, while simultaneously maintaining the quality of the ambient air.

All new cement plants are adopting green processes. This means they would be making blended / composite cements, using alternate fuels (AF),using waste gasses to co-generate power or to even make cement and using renewable sources of power like wind and sun.

The challenges

The challenges in setting up a cement plant can be broadly divided into technical challenges and external challenges.

Technical challenges include those related with processes, preparation of raw materials, fuels and semi- finished products for processing, availability of machinery, plant and equipment for various operations, instrumentation and process control management for plant operation at optimum levels.

External challenges are related to deciding on the most suitable location for the plant with respect to access to raw materials, fuel, power, and of course, the market.

Technical challenges Processes

There are hardly any technological challenges with respect to process or machinery; even for current sizes of plants with more than 10,000 tpd kiln capacity. Machinery of required design and capacity is available to be used as single units. Out of necessity, cement mills are installed as multiple units to produce different types of cements simultaneously. Multi -stream pre-heaters and calciners are used on 10,000 tpd production lines. Calciners have been developed to permit multi- stage feeding of raw meal and fuel, and to keep NOx levels down within permissible limits. Both the kiln and calciner can be fired simultaneously with coal/oil and alternate fuels; several designs of highly efficient clinker coolers are available. Vertical mills, roller presses and ball mills of required sizes and capacities are available; the industry has already reached fuel efficiency levels of ~ 650 kcal/kg clinker and power consumption of ~ 80 kwh/tonne of cement.

Alternative fuels

The only new element is the preparation of alternative fuels for firing in kiln/calciner. AFs come from myriad sources in many different forms and are widely different from each other and from coal. Fuel preparation systems have to be designed to suit selected AFs for use on a continuous basis. This could involve crushing, drying, pulverising petcoke, shredding tyres, briquetting rice husk, gasification of biomass, etc. The process may require special equipment like briquetting press, shredders, gasification plant and machineries like hot disc, multi-channel burners to fire oil, coal and gas simultaneously. Such versatile systems are at the disposal of modern cement plants today.

What is most necessary for use of AFs is rigorous quality control at all stages, right from the source, to the point of firing. It is also necessary to monitor chlorine, dioxins, heavy metals, etc, in specific cases. In some cases, it may be necessary to install a kiln bypass system at the kiln inlet. Some AFs are hazardous and need special care in their handling and storage.

Waste heat recovery systems

A wide range of options are available in waste heat recovery systems (WHRS). This wide range makes it crucial to select the system most appropriate. There are many ways in which a WHRS can be installed. Suitable machinery is available for every type of requirement.

External challenges

Apart from the challenges arising from financial angles, setting up a plant would require attention to several other factors. These challenges are common for all types of cements as much as for green cement.

Some external challenges include:

• Selecting location for the proposed cement plant.
• Acquisition for land for factory and colony.
• Obtaining mining lease.
• Obtaining environmental clearances.

Land acquisition

Acquisition of land can be a big problem particularly if the land is under cultivation. A 10,000 tpd clinkering unit producing ~ 6.5 mtpa of slag cement, along with a railway siding, would require about 300 hectares just for its factory. The selection of the right location for a proposed cement plant is based on access to market, location of mineral deposits, sources of power and fuel, infrastructural facilities like rail and road links, availability of manpower, etc. Now a new dimension is added to this; a sources of AF.

The final location ought to be selected in a way that it balances the pros and cons and veer strongly in favour of the plant. If an ISP (Intermediate Service Provider) is available to supply AFs in ready use form, the problem is resolved to a great extent.

Careful investigations of prospective deposits in terms of quality and quantity to suit the selected process and the the final capacity of the plant is very important. The most promising deposit may not be readily available for exploitation, or if available, it may not be large enough. Thus, finalising the deposits and acquiring a mining lease can be a long drawn-out process. It becomes even more difficult if the deposits are in reserved areas like in forests or in sanctuaries.

Statutory clearances

Clearances for setting up a cement plant must be obtained from the MoEF (Ministry of Environment and Forests) and Pollution Control Boards. These clearances are issued only after various conditions stipulated by government norms are met.

Important conditions linked to: Mining operations, so as to leave as small a footprint as possible.

• Greening of slopes, use of ground water in mines and afforestation.
• Water management; recharging groundwater by rainwater harvesting, system of garland canals and check dams in specific cases, ETP, zero waste water discharge.
• Green belts and landscaping in and around the factory and colony.
• Monitoring and adhering to emission norms for particulates from stacks and for fugitive dusts as laid down by State and Central Pollution Control Boards.

New dimension

Though not mandatory at the moment, the industry is expected to monitor emissions of greenhouse gasses. These stipulations are to be met by all proposed cement plants, green or grey. Since the cement industry is committed to the principle of sustainable development, it will willingly comply with these stipulations and do necessary planning in advance.

Green buildings

Norms have been developed for green buildings that make maximum use of sun and wind to reduce dependence on lighting and air- conditioning. Though not mandatory, adopting them would make the existing plants greener. The Bureau of Energy Efficiency has issued norms for lighting fixtures and cooling media to be used in refrigerators and air- conditioners. It would be best to keep these in mind right from the planning stage.

Benefits of meeting these challenges

There are several real and tangible benefits of accepting the challenges and in greening the cement plants.

• GHG emissions can be reduced from ~0.76 t/t for OPC to 0.30 t/t for slag cement with AF and WHR..
• Substantial savings can be achieved by conserving reserves of limestone and fossil fuels. Capital costs of annual capacity can come down by 30 to 40 per cent even after allowing for additional costs for AF and WHR. Costs of production of naked cement excluding works also come down by 20 to 25 per cent in case of blended cements with AF and WHR.

Renewable energy

Power plants based on renewable sources such as wind and solar power will soon become an integral part of new cement plants, making them greener as these sources of energy are totally free of GHG emissions. The necessary technology to meet these goals is now available and very reliable.

However, the main problem associated with these sources is that the generation of wind and solar power is not consistent. The capacity factor is also very low compared to that of thermal power plants. Secondly, it may not always be possible to locate the wind or solar power plants close to the cement plant. A cement plant would have to manage several sources of electrical energy, grid, captive power plant, WHRS and power from renewable energy. A sound strategy must be in place to ensure continuity of power at optimum cost.

Future challenges

Cement industry will have to gear up itself to meet new challenges in the future such as upgrading its technologies for carbon capture and storage. GHG emissions cannot be pulled down to the targeted levels merely by making blended cements and by using AF. There are technologies for separating CO2 from waste gases on the horizon. It could be used by other industries or it can also be used for making new cements substitutes such as those made by Calera Corporation (http://www.calera.com). Several cement substitutes like Calera, Novacem, Aether, are in various stages of development.

All the new cements are green cements. The cement industry should be watchful and examine how these green products could be made in their existing production facilities.

SP Deolalkar, Director, Deolalkar Consultants, Reference- Author’s forthcoming book : Designing Green, Cement Plants.