Which Bureau of Energy Efficiency Godavari heat recovery report pays back fastest for a refractory unit: 50, 100 or 200 tonnes a batch?

In three Bureau of Energy Efficiency (BEE) Godavari reports, kiln heat recovery costs rupees (Rs) 9, 15 and 25 lakh and pays back in 0.57, 0.45 and 0.44 years. All three price coal at Rs 4,500 a tonne. The 50 tonne report prints its carbon dioxide (CO2) twice, 379 and 650 tonnes.

The three reports side by side

• 50 tonnes a batch: cost Rs 9.00 lakh. Coal 45,000 kilograms a batch, 12,355.6 saved, 30 batches a year, so 370.67 tonnes. Net benefit Rs 15.69 lakh. Payback 0.57 years.
• 100 tonnes: cost Rs 15.00 lakh. Coal 140,000 kilograms a batch, 38,439.5 saved, 20 batches, so 768.79 tonnes. Net benefit Rs 33.52 lakh. Payback 0.45 years.
• 200 tonnes: cost Rs 25.00 lakh. Coal 280,000 kilograms a batch, 86,826.0 saved, 15 batches, so 1,302.39 tonnes. Net benefit Rs 56.19 lakh. Payback 0.44 years.
• All three cool the flue gas to 210 degrees Celsius (°C) from 650, 650 and 690 °C, with a heat exchanger 75 percent efficient and coal at 4,200 kilocalories (kcal) a kilogram. The net benefit is coal saved at Rs 4,500 a tonne less the blower's electricity, Rs 0.99, 1.07 and 2.42 lakh.

Why the 200 tonne report saves a bigger share

The savings are 27.5%, 27.5% and 31.0% of the coal burned. The 200 tonne report uses a hotter flue, 690 against 650 °C, and the annexure uses 35% excess air against 30%, although section 1.4.1 of the same report prints 30%. That gives about 1,538, 1,538 and 1,737 kcal of waste heat above 210 °C for each kilogram of coal burned. At 75% recovery and 4,200 kcal a kilogram, that is 27.5%, 27.5% and 31.0%.

The 50 tonne report disagrees with itself on coal

• Annexure: 45,000 kilograms a batch, so 30 batches use 1,350 tonnes a year.
• Section 1.4.1: 15 tonnes of coal for 35 tonnes of hollow bricks in an 8 day batch, in a kiln designed for 50.
• Table 1.1: one unit, 914 tonnes of coal and 800 tonnes of product a year, 1.14 kilograms of coal for each kilogram.
• If 15 tonnes were the real baseline: 15,000 x 27.46% = 4,119 kilograms a batch, x 30 = about 123.6 tonnes a year, Rs 5.56 lakh, less Rs 0.99 lakh of blower electricity = Rs 4.57 lakh. Payback 9.00 / 4.57 = about 2.0 years, not 0.57.
• The 100 and 200 tonne reports are closer on the section 1.4.1 figures: 140 tonnes of coal for 90 of product and 280 for 180, both 1.56 for each tonne of product.
• A small slip: the 50 tonne text prints the internal rate of return as 149.04% and its Table 4.2 as 149.40%.

Other places the reports disagree with themselves

• 100 tonnes: section 4.1.1 says the system costs ` 9.00 lakhs as per quotation, while the summary and the annexure say 15.00 lakh. This page uses 15.00.
• 200 tonnes: section 1.4.1 prints excess air measured at 30% and heat maintained 2 days, but the annexure uses 35% excess air and section 2.1.1 says 3 days is the soaking period.
• Table 1.2 prints coal at 1.14, 1.00 and 0.94 kilograms for each kilogram of product (50, 100 and 200 tonnes), against the 1.56 for each tonne of product that section 1.4.1 gives for the two larger kilns.

Carbon dioxide: the lines to leave alone

The summary tables print 379, 807 and 1,354 tonnes of CO2 a year. The 50 tonne text (section 3.4.2) says 650 tonnes for the same 370.67 tonnes of coal, 1.75 for each tonne, against the 379 of its summary. On Senseible's Indian coal factor of 1.76 kilograms of CO2 for each kilogram (India BUR-2, 2018), 370.67 tonnes of coal is 652 tonnes, close to 650 and far from 379. The report prints no factor that I could find for 379, so do not copy that line. The 100 and 200 tonne lines are checked on their own pages, linked below. Use your own coal tonnes with a sourced factor.

The 50 tonne annexure arithmetic

• Flue gas: 45,000 x (8.50 x 1.30 + 1) = 45,000 x 12.05 = 542,250 kilograms a batch
• Heat above 210 °C: 542,250 x 0.29 x (650 minus 210) = 69,191,100 kcal
• Recovered at 75%: 51,893,325 kcal / 4,200 = 12,355.6 kilograms of coal a batch
• x 30 batches = 370.67 tonnes x Rs 4,500 = Rs 16.68 lakh; less Rs 0.99 lakh = Rs 15.69 lakh; 9.00 / 15.69 = 0.57 years

Every input is the report's own: 8.50 kilograms of theoretical air, 30% excess air, 0.29 specific heat.

What Senseible does here

Senseible reads fuel invoices and electricity bills into monthly records, so once you upload your coal and power bills, coal bought each month sits on record to test a report's per batch baseline against. In the self-serve product it does not read kiln logs, so batch counts come from your own firing book; custom integrations are available on request.

• Downdraft kiln heat recovery on a 100 tonne kiln
• Godavari 200 tonne kiln heat recovery CO2 check
• Godavari kiln batches a year behind the savings
• Green loan readiness check

Sources: BEE, Detailed project report: waste heat recovery for preheating refractories, up to 50 tonnes a batch, Godavari refractories cluster (SAMEEEKSHA), BEE, Detailed project report: waste heat recovery, 100 tonne kiln, Godavari refractories cluster (SAMEEEKSHA), BEE, Detailed project report: waste heat recovery, 200 tonne kiln, Godavari refractories cluster (SAMEEEKSHA)

Last reviewed 2026-11-06. Figures are from the Bureau of Energy Efficiency (BEE) Small and Medium Enterprises (SME) programme reports, at the report year's prices, coal at Rs 4,500 a tonne. Check today's coal price and a current quote before relying on any payback. Where a report disagrees with itself this page says so.