What does a flue gas analyser save on a Batala, Jalandhar or Ludhiana foundry cupola, according to the Bureau of Energy Efficiency report?

The Bureau of Energy Efficiency (BEE) prices a flue gas analyser for a Punjab foundry cupola at rupees (Rs) 1.00 lakh. It counts 3.21 tonnes of coal saved a year, worth Rs 0.48 lakh, a payback of 2.07 years. The saving comes from cutting oxygen in the exhaust from 9.95% to 6%.

What the instrument does, in plain words

A cupola is the tall furnace that melts scrap and pig iron with burning fuel and a blast of air. Flue gas is the hot smoke that leaves the top. A flue gas analyser is a probe and a meter that tells you how much oxygen is still in that smoke.

Oxygen in the smoke means air went in that did no burning. Think of heating a room with the window open: the heater runs, and part of the heat walks out. Less spare air means less fuel wasted warming it. The meter does not save anything by itself. Someone has to read it and move the blower damper, the flap that sets how much air goes in.

The report's numbers for one cupola

• Before: oxygen in the exhaust 9.95%, which the report prints as 90% excess air, exhaust temperature 250 to 300 degrees Celsius.
• After: oxygen 6.00%, printed as 40% excess air.
• Each batch charges 2.38 tonnes of metal and burns 384.8 kilograms of coal before, 372.0 after. A kilogram of coal is costed at Rs 15.
• Over a year of 250 working days, coal falls from 96.2 to 92.99 tonnes. The saving is 3.21 tonnes, printed as 3.34% of the coal, Rs 0.48 lakh. A lakh is 100,000.
• Cost: Rs 99,676, made of Rs 94,780 for the analyser, Rs 1,896 of tax and Rs 3,000 of other cost. The report's own loan, return and sensitivity tables give a payback of 2.07 years and an internal rate of return of 30.97%.
• Carbon dioxide (CO2): the report prints 6.4 tonnes a year saved.

Which of the printed figures hold up

• The air figures tie. The air ratio is 21 divided by (21 minus the oxygen percentage). At 9.95% that is 1.90, so 90% extra air. At 6% it is 1.40, so 40% extra.
• The coal sums tie. 384.8 kilograms x 250 batches = 96,200 kilograms, so the report's 96.2 tonnes works out to one batch a day. The saving per batch is 12.8 kilograms, which over 250 batches is 3.2 tonnes. The report prints 3.21.
• The 555 tonnes of output ties as good castings, not metal charged: (2.38 minus 0.160 tonnes rejected) x 250 = 555. On that basis the cupola burns 96.2 / 555 = 0.173 kilograms of coal per kilogram of good castings. The report's own table of specific fuel use says 0.2 kilograms of coal for each kilogram of molten metal. The batch figures give 0.16 on the metal charged. Quote the batch figure only if you also say which tonnes you divided by.
• A sister report in the same series, on the divided blast cupola, costs a different sample cupola: 2.14 tonnes charged and 500 kilograms of coal a batch, which is 23%, and 500 tonnes a year. This report's cupola is 2.38 tonnes and 384.8 kilograms, which is 16%, and 555 tonnes. They are two sample units, not one. Do not mix their baselines.
• The summary and the body differ. The executive summary says oxygen falls from 9% to 6%. Every table in the body uses 9.95%.
• The CO2 line has no printed factor. 6.4 tonnes on 3.21 tonnes of coal is about 2.0 tonnes of CO2 per tonne of coal. Senseible's default for Indian coal is 1.76 (India's second Biennial Update Report, Table 2.3), which would give about 5.65 tonnes. The live page on the divided blast cupola says cupolas burn foundry coke, and the report's "coal" is probably coke. At the IPCC default of about 3.02 tonnes of CO2 per tonne of coke, 3.21 tonnes is about 9.7 tonnes. Use your own fuel and a sourced factor, not the 6.4.
• The saving appears to assume the exhaust stays at 300 degrees Celsius. That is our reading of Table 3.2, where after is 300 and before is 250 to 300. It does not price any change in melt time or in rejects.

Before you buy one

1. Write down the coal or coke you charge per batch and the tonnes of good castings, from your own invoices and tally sheets. If you cannot, the analyser has nothing to be compared with.
2. Take a reading at the start of the blast and again an hour in. Oxygen moves through a heat.
3. Decide who owns the damper. The report's saving needs the setting changed, not just the probe fitted.
4. Re-run the sum at today's fuel price. The report uses Rs 15 a kilogram and Rs 5 a unit from 2009 to 10 data.

Example: your own cupola, same method

• Coal per batch now: 420 kilograms for 2.5 tonnes charged (example numbers)
• Oxygen now 9.95%, target 6%. If the report's 3.34% carries over: 420 x 0.0334 = 14.0 kilograms a batch
• At 230 batches a year: 14.0 x 230 = 3,220 kilograms, about 3.2 tonnes
• At an example Rs 32 a kilogram (check your invoice): 3,220 x 32 = Rs 1.03 lakh a year, against about Rs 1 lakh to buy

The 3.34% is the report's own figure for its sample unit. Your result depends on your cupola. The batch, price and year here are examples.

What Senseible does here

Senseible reads coal invoices into monthly records. You bring your own castings tonnes to compare against. Analyser or oxygen sensors can be added on request.

• What air ratio or oxygen should a furnace run at
• Divided blast cupola and coke saving
• CO2 per tonne of castings at a cupola foundry
• Your carbon number for buyers and banks

Sources: BEE, Detailed project report: flue gas analyser to reduce excess air, Batala, Jalandhar and Ludhiana foundry cluster (SAMEEEKSHA), BEE, Detailed project report: divided blast cupola, Batala, Jalandhar and Ludhiana foundry cluster (SAMEEEKSHA)

Last reviewed 2026-11-07. Figures are from a 2011 report on 2009 to 10 data, at its Rs 15 a kilogram coal price and Rs 5 a unit power price. Check today's prices and a current quote before you rely on the payback.