What did the Bureau of Energy Efficiency test on three old 400 kilogram wood boilers in Vapi, and which efficiency does it print?

A boiler is the wood-fired kettle that makes steam for a dye plant. The Bureau of Energy Efficiency (BEE) Vapi report tested three old 400 kilogram boilers at 41.4, 37.9 and 44.7%. The report prints 41.43% as the average, which matches unit 1 alone. A new 65% boiler would save 49 tonnes of wood a year.

What a boiler test tells you, in plain words

A boiler burns wood to boil water. The steam travels in pipes to the reactors and heats them, like a kettle that heats a whole building. Efficiency is how much of the wood's heat ends up in the steam. Think of carrying water in a leaky bucket: it is the share that reaches the tank.

The report is a detailed project report (DPR), a costed plan for one upgrade, by the Bureau of Energy Efficiency (BEE) for Vapi dye and chemical units. It tests three old boilers, then prices a new one.

The three tests

• Swapnil Organics: 83.5 kilograms of wood an hour x 3,800 kilocalories (kcal) per kilogram = 317,300 kcal in. Steam 210 kilograms an hour at 5 kilograms per square centimetre (kg/cm2), each kilogram carrying 626 kcal more than the feed water, so 131,460 kcal out. 131,460 / 317,300 = 41.4%.
• Hatkesh Chem and Engineering: 78 x 3,800 = 296,400 in. Steam 180 kilograms an hour at 4 kg/cm2 x 624 = 112,320 out. 37.9%.
• Asian Dye Chem: 75 x 3,800 = 285,000 in. Steam 205 kilograms an hour at 3.5 kg/cm2 x 622 = 127,510 out. 44.7%.
• Plain average of the three: (41.4 + 37.9 + 44.7) / 3 = 41.3%.

Which figure the report uses

Section 1.4.2 says the operating efficiency of the existing boiler is 41.43%, and Annexure 3 uses 41.4. Section 3.1.1 calls 41.43% the average, but it matches unit 1 alone (our check: 131,460 / 317,300 = 41.43%). The new boiler is also sized against that one unit's wood: 135 tonnes a year is the Swapnil Organics figure, which the report uses as the typical unit.

Where summary and body differ

• Summary: most units run old boilers at 40 to 45%. The tests show 37.9 to 44.7%, so one is outside that range.
• Loading: the text says the boilers run at less than 20% of capacity. The tested steam, 180 to 210 kilograms an hour on a 400 kilogram boiler, is 45 to 52.5% of the rating. That is our arithmetic, on the reading that capacity use means steam made against rating. The report does not say how it measured it.
• Waste heat: the summary credits the new boiler's 65% partly to waste heat recovery, while section 1.3.1 says waste heat recovery has no potential in smaller boilers, then in the same sentence says there is enormous potential in the flue gas, which leaves at 240 to 270 degrees Celsius.
• Labels: the enthalpy row says 'at 5 kg/cm2' for all three units though the pressures printed are 5, 4 and 3.5, and Annexure 1 is titled efficiency of the existing pumps. The values 656, 653 and 652 kcal per kilogram are used as printed.

The saving and the money

• Hours: 9 hours a day x 180 days = 1,620 hours. 135 tonnes / 1,620 = 83.3 kilograms an hour, matching the first unit's 83.5.
• New boiler at 65%: 135 x 41.4 / 65 = 86 tonnes. Saving 135 minus 86 = 49 tonnes. At rupees (Rs) 3,500 a tonne that is Rs 1.715 lakh, printed 1.72. A lakh is 100,000.
• Cost Rs 5.10 lakh = 4.40 for the boiler + 0.60 for taxes. Payback 5.10 / 1.72 = 2.97 years, printed 2.96.
• Own money 25% is Rs 1.28 lakh and the loan 75% is Rs 3.83 lakh. The report leaves out the boiler's electricity because the feed water pump is small.

Unit 1 test, line by line

• Heat in: 83.5 x 3,800 = 317,300 kcal an hour
• Heat per kilogram of steam: 656 minus 30 = 626 kcal
• Heat out: 210 x 626 = 131,460 kcal an hour
• Efficiency: 131,460 / 317,300 = 41.4%
• Same steam at 65%: 131,460 / 0.65 = 202,246 kcal in, which is 202,246 / 3,800 = 53.2 kilograms of wood an hour against 83.5

Inputs are the report's own. The last line is our check of what 65% means for this unit's hour.

What Senseible does here

Senseible reads fuel invoices and electricity bills into monthly records, so a year of wood purchases is on file to test the 135 tonne baseline against. Self-serve, Senseible reads bills, not steam or flue gas. Steam and gas meters can be set up with the Senseible team on request.

• Green loan readiness check
• Boiler efficiency: direct and indirect method
• Steam flow meter or fuel records
• Vapi reports: wood counted as a cut or zero

Sources: BEE, Detailed project report: energy efficient boiler 400 kg/hr, Vapi dyes and chemicals cluster (SAMEEEKSHA)

Last reviewed 2026-11-07. Figures are from the report named above, written in 2010; costs, fuel prices and paybacks are at that year's prices. Check today's prices and a current maker's quote before you rely on the payback.