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Taj Mahal, the architectural wonder that brings the world to Agra's courtyard, has been robbed of its grandeur. Polluted air from various sources, including the teeming industrial units in its vicinity was believed to cause the damage. Beyond the fear of a medieval glory being hidden behind fumes, the looming reality is that the numerous polluting industrial units operating in the entire Taj Trapezium Zone were affecting the health of millions of inhabitants of the area. One of the reasons for this is the pollution caused by the small scale glass industry cluster in the city of Firozabad, which was the nerve centre of this trade in India.

While the bigger glass melting units in Firozabad employ tank furnaces, the smaller ones use pot furnaces. Also, a large number of muffle furnaces are being used for baking bangles. The technology in all these cases, however, had remained the same over the past many decades, and very little effort had been made to improve the working conditions and the technology. The traditional designs of coal-fired pot and muffle furnaces are very poor in terms of energy efficiency and environmental performance. As per the Supreme Court judgment, it was mandatory for polluting furnaces to shift to the use of natural gas within a definite time frame. But there was no off-the-shelf technology available for the pot and muffle furnaces to facilitate the shift. To these industrial units looking for a way out of their predicament, TERI's intervention to provide them with energy-efficient and natural-gas-based technological solutions was much-needed indeed.

A polluting glass baking unit in Firozabad

TERI researchers developed a model for environmental performance – natural-gas-based pot and muffle furnaces that are energy-efficient, which also make good economic sense. By agreement with the glass industry association and the district authority of Firozabad, TERI set up two demonstration plants, one each for pot and muffle furnaces. Aiming at helping these units switch over to the new technology, the pilot programme was a joint initiative involving TERI and the Swiss Agency for Development and Cooperation.

The new natural-gas-fired pot furnace

Innovation: A state-of-the-art natural-gas-fired pot furnace was set-up at Firozabad by TERI with support from British Glass. Keeping the traditional design and mode of operation unchanged, the new system minimized energy wastage by using pre-heated air for combustion, and utilizing the heat of the outgoing flue gases. Also, the installation of efficient combustion systems and use of better refractory and insulation materials reduced functional and structural losses. The refurbished furnace was centrally fired by a single burner mounted on the furnace crown for better heat distribution. Improved structural design and use of better quality material for the furnace crown extended its life to three years degradation.

Similarly, better quality refractory materials like silimanite and zirmul were used for the floor in place of conventionally used refractories. To check the heat from escaping through the stack, a heat recovery system in the form of a metallic recuperator was installed to pre-heat incoming combustion air to 600 °C.

A natural-gas-fired muffle furnace was designed and demonstrated by adopting a participatory technology development approach.

Outcome/Benefits: The refurbished natural-gas-based furnaces are excellent environment performers in that there was a substantial reduction in energy consumption as well as emissions of pollutants. The glass units could benefit immensely as the gas-fired furnaces demonstrate energy savings up to 50% and 30% in the case of pot and muffle furnaces, respectively. TERI's initiative has motivated 45 muffle furnace units to switch over to the TERI model despite paucity of piped gas supply in the area. In the case of pot furnace, besides the demonstration plant, another unit based on the TERI model has been set up while two more are under construction.

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