How much coal can raw material preheating save in a 100 TPD sponge iron kiln?
The Bureau of Energy Efficiency's (BEE) detailed project report for a 100 tonnes per day (TPD) Odisha kiln estimates that preheating the raw material with hot flue gas saves about 1,965 kg of coal an hour, or 14,145 tonnes a year. It is a 2010 engineering estimate, not a measured result, so check it against your own coal bills.
What the report assumes
- A 100 TPD rotary kiln with flue gas of about 24,000 normal cubic metres (Nm3) an hour at around 900 degrees C, carrying about 5.89 million kcal an hour.
- Coal of 3,000 kcal per kg, so 5.89 million kcal an hour is about 1,965 kg of coal an hour.
- 24 hours a day for 300 days a year, which gives 14,145 tonnes of coal a year.
- A preheating kiln that warms the iron ore and dolomite mixture before it enters the main kiln, using the heat that now goes up the stack or is cooled by fans.
How it compares to the kiln's coal use
The report puts a typical 100 TPD kiln at 48,000 tonnes of coal a year, so 14,145 tonnes is about 29 percent. Elsewhere it lists coal at 180 tonnes a day, which over 300 days is 54,000 tonnes and makes the saving about 26 percent. Both sit above the report's own line that at least 20 percent of coal is saved, so treat the headline as a generous estimate and plan on measuring.
What it costs in power
The preheating kiln uses about 1,800 kWh a day, roughly 540,000 kWh over 300 days. The report also says electricity is saved on the forced draft fans and the gas cooling system, but gives no figure for that.
Other effects the report claims
- About 20 percent more production capacity, because the charge spends less time in the main kiln.
- No significant effect on product quality.
Example: carbon dioxide (CO2) on the report's own numbers (estimate)
- Coal saved: 14,145 t x 1.76 kg CO2 per kg (Indian coal) = 24,895 t CO2
- Extra power: 540,000 kWh x 0.675 kg CO2 per kWh = 365 t CO2
- Net before fan savings: about 24,530 t CO2 a year
Estimate. It uses the report's 14,145 t, the Indian coal factor from India's Second Biennial Update Report (2018) and the Central Electricity Authority grid factor for FY 2025-26. Your own coal per tonne of sponge iron is the real test.
What Senseible does here
Senseible reads coal and electricity invoices into monthly tonnes and CO2 per site, so coal per tonne of sponge iron before and after a retrofit is on record. The saving the report estimates can only be confirmed by your own bills.
Last reviewed 2026-11-04. A 2010 estimate with some internal differences; compare with metered coal per tonne after any retrofit.