Resource detail
The Indian forging industry comprises hundreds of units of different capacities that are dispersed across the country. There are around 50 small and medium sized forging units operating in Pune, Maharashtra, along with 20 heat treatment units which are mainly vendors of the forging units. The forging and heat treatment furnaces are major energy consuming operations, accounting for 60–70% of the total energy consumption. Consequently, there is a big opportunity for energy conservation through insulation and waste heat recovery.
About the project: The Pune forging cluster is one of the five MSME clusters targeted under the GEF–World Bank project titled ‘Financing Energy Efficiency at MSMEs’ being implemented by Bureau of Energy Efficiency (BEE). Under this project, the German Agency for International Cooperation (GIZ) associated with KAEFER, the world’s largest provider of complete insulation solutions, to demonstrate the techno-economic feasibility of veneering (hot face insulation) technology as an energy efficiency measure in heat treatment furnaces, along with advisory services, capacity building, financing, etc.
About the intervention in the unit: A heat treatment unit was selected as demonstration unit for the project, based on a pre-feasibility test and in consultation with Association of India Forging Industry. The demo unit uses a box type heat treatment furnace of capacity 0.7 tons. The furnace is operated in batches, and used for heat treatment processes like normalization, annealing and tempering. Depending on the heat treatment process, the material is heated up to 940 oC and soaked at this temperature for few hours before it is cooled. The furnace is operated on compressed natural gas.
For assessing the energy saving potential, the project team conducted a detailed study of furnace design, operation and maintenance practices and identified two major factors that led to energy losses, and that offered potential for energy saving through improved insulation:
- High levels of heat storage by the refractory material
- High surface temperature of furnace (120 oC), leading to radiation losses.
To reduce these heat losses, the project team implemented veneering (hot face insulation) technology. Veneer modules (75 mm thickness) were applied from the hot face of the furnace to its existing refractory lining. The veneer modules are a low mass insulation material made from compressed ceramic fibre blanket with a low thermal conductivity. The process involved surface finishing/ preparation, pasting the veneer modules, and heat retardant coating. The veneer reduced the levels of heat storage by the refractory, and thereby decreased heat losses during furnace operation. Conversely, the veneer enabled heat retention in the refractory bricks during furnace shutdown, thereby reducing the heat and time required for the next start.
A documentary of this activity can been seen at http://www.youtube.com/watch?v=BQxalZ4eGng
Outcome/Benefits: After veneering, the furnace operation was monitored for about a month to assess its benefits. The results, as confirmed by the plant personnel, are as follows -- For cold start, the time required to reach the desired temperature (940 oC) reduced from 9 hours to 4 hours; Fuel required during cold start reduced to 50% without any design or process modifications; Around 8–10% reduction in fuel consumption during the heat treatment process; Thermal scanning of the furnace confirmed reduction in the surface temperature from 120 oC to 55 oC, thereby reducing radiation losses. The payback period for the veneering technology is estimated at about 5–6 months, assuming the cost of procurement and installation of 75mm thick veneer module at Rs 1200/ft², 225 days of operation and 72 cold starts per annum. The actual payback period will differ from unit to unit. As the veneer modules are applied on the existing refractory lining, the complete implementation process requires only 3–4 days of down time. Other benefits that result from the veneering process include -- Enhanced production capacity due to reduction in cold start up time; Enhanced refractory life, as the veneer reduces thermal spalling (breaking up of refractory due to repeated heating and cooling); Decreased risk of burns to factory personnel, due to lower surface temperatures; Reduction in greenhouse gas emissions
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