What does heat recovery save on a 200 tonne downdraft kiln, and is the report's CO2 right?

In the Bureau of Energy Efficiency (BEE) Godavari report, preheating combustion air with 690 degrees C flue gas saves 1,302 tonnes of coal a year, Rs 56.19 lakh, for Rs 25 lakh. Its 1,354 tonnes of carbon dioxide (CO2) is about 1.04 a tonne of coal; Indian coal gives about 2,292 tonnes of CO2.

How the report gets 1,302 tonnes

• A batch burns 280 tonnes of coal; flue gas leaves at 690 C and is cooled to 210 C. 3,493,000 kg of flue gas x 0.29 x 480 = 486,225,600 kilocalories (kcal) a batch.
• A heat exchanger at 75% recovers 364,669,200 kcal, equal to 86,826 kg of coal a batch at 4,200 kcal a kg.
• 15 batches a year: 1,302.39 tonnes, 31% of the 4,200 tonnes the kiln burns.

The money

1,302.39 tonnes x Rs 4,500 = Rs 58.61 lakh. The blower takes 64,454 kilowatt hours (kWh) a year, Rs 2.42 lakh, leaving Rs 56.19 lakh on Rs 25 lakh: payback 0.44 years.

The carbon dioxide line

The report gives 1,354 tonnes of carbon dioxide (CO2), 1.04 tonnes for each tonne of coal. The coal gasifier report from the same cluster gives 1,200 tonnes for 666.7 tonnes, 1.80 a tonne. Coal cannot emit as little as 1.04. At 4,200 kcal a kg (17.6 gigajoules a tonne) the Intergovernmental Panel on Climate Change (IPCC) bituminous coal default gives 1.66 tonnes a tonne, and at Senseible's Indian coal factor of 1.76, 1,302 tonnes of coal is about 2,292 tonnes of CO2.

Carbon dioxide at an Indian coal factor (estimate)

• Coal saved: 1,302.39 tonnes x 1.76 = 2,292 tonnes CO2
• Blower power: 64,454 kWh x 0.675 = 43.5 tonnes
• Net: about 2,249 tonnes a year, against the report's 1,354

Coal at Senseible's Indian coal factor and grid power at the Central Electricity Authority financial year 2025-26 factor, both estimates. Heat figures from the Bureau of Energy Efficiency (BEE) report.

What Senseible does here

Senseible reads fuel invoices and electricity bills into monthly records with carbon dioxide equivalent (CO2e), so coal per batch before and after heat recovery is on record, not remembered. The green loan check shows what a lender asks for.

• Green loan readiness check
• Waste heat recovery on a 100 tonne kiln
• Coal gasifier on a 100 tonne downdraft kiln
• Godavari refractory cluster: coal and carbon

Sources: BEE, Detailed project report: waste heat recovery for a 200 tonne downdraft kiln, East and West Godavari refractories cluster (SAMEEEKSHA), IPCC 2006 Guidelines, Volume 2 Energy, Tables 1.2 and 2.3, CEA, CO2 Baseline Database for the Indian Power Sector

Last reviewed 2026-11-04. Report figures are from a Bureau of Energy Efficiency (BEE) Small and Medium Enterprises (SME) programme project report; costs and paybacks are at the report year's prices. Check today's prices and a current quote before you rely on the payback.