What do the Tiruppur manual's flue gas heat recovery and condensate recovery reports save for a small wood fired boiler?
The Bureau of Energy Efficiency (BEE) Tiruppur manual saves 23 tonnes of wood yearly, rupees (Rs) 0.46 lakh (1 lakh = 100,000), by cooling flue gas from 220 to 120 degrees Celsius (C), and 21.9 tonnes, Rs 0.66 lakh, by returning 100 kilograms (kg) an hour of condensate. The first pays back in 1.1 years; the second prints no cost.
Flue gas heat recovery
- Flue gas leaves above 220 degrees C and is vented without recovery in most units. The manual says heat can be recovered from 220 down to 120 degrees C because the fuel is wood, preheating boiler feed water or combustion air.
- Saving booked: 5% of fuel, 3 kilograms an hour, 23,040 kilograms a year. That implies 7,680 hours, or 320 days of 24 hours. Wood at Rs 2 a kilogram: Rs 46,080. Investment Rs 50,000, so 50,000 / 46,080 = 1.09 years, printed 1.1.
- The manual says it applies to units that may not invest in a new boiler in the near future.
Condensate recovery
- Boiler making 125 kilograms of steam an hour, 80% of it recoverable as condensate: 100 kilograms an hour at 80 degrees C, with water at 32 degrees C. Heat: 100 x (80 minus 32) = 4,800 kilocalories (kcal) an hour.
- Boiler efficiency 39.44%. Wood saved: 4,800 / 0.3944 = 12,170 kcal an hour, and at about 4,000 kcal a kilogram that is 3.04 kilograms an hour, printed as 3.0.
- Year: 24 hours x 300 days x 3.04 = 21,888 kilograms, about 21,900. The manual prints 21,904 kilograms and Rs 65,713, at Rs 3 a kilogram. No investment is printed, and the summary tables say immediate.
- The manual says some compacting units have no condensate recovery and drain it all.
Three cautions
- The two cases use different wood prices, Rs 2 and Rs 3 a kilogram, and different boilers. Do not add them; each depends on your boiler and your fuel price.
- The condensate case prints a boiler efficiency of 39.44%. At 70% the same 4,800 kcal saves 1.7 kilograms an hour, so the saving shrinks as the boiler improves.
- Condensate recovery with no investment printed still needs a return line, a tank and a pump. Get a quote before calling it free.
Condensate case from the printed lines
- Condensate: 125 x 80% = 100 kg an hour; heat 100 x (80 minus 32) = 4,800 kcal an hour
- Wood: 4,800 / 0.3944 / 4,000 = 3.04 kg an hour; x 24 x 300 = about 21,900 kg (printed 21,904)
- Rupees: about 21,900 x 3 = about Rs 65,700 (printed Rs 65,713)
- At 70% boiler efficiency: 4,800 / 0.70 / 4,000 = 1.71 kg an hour
The 4,000 kcal a kilogram is the value in the manual's chulha table, used because the condensate table prints no wood value. It gives about 21,900 kilograms; the manual prints 21,904 and Rs 65,713, so 4,000 kcal a kilogram is close to the value it used.
What Senseible does here
Senseible reads fuel invoices and electricity bills into monthly records, so wood bought each month is on file before and after a recovery fit. Steam made and condensate returned need your own meters.
- Boiler blowdown heat recovery savings
- Tiruppur boiler swap: compacting or dyeing
- Tiruppur manual: payback table in months or years
- Green loan readiness check
Last reviewed 2026-11-05. Figures are from the manual's study year (around 2010 to 2011), with wood at Rs 2 to 3 a kilogram. Redo the sums with your own boiler test and fuel price.