GREEN CEMENT PLANT AND ITS CHALLENGES

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 it also has to face certain challenges. 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.

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.

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.

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