PlantmarginSteam and boiler losses in tea, dairy and sugar plants
Fuel for the boiler is often the largest energy cost in a processing plant. Firewood, briquettes, bagasse or heavy fuel oil all burn through the same losses.
Measure fuel per tonne of steam
The key indicator is kg of fuel per tonne of steam at a stated steam pressure. Watch it daily. A sudden rise means combustion has drifted, or steam is being lost.
The usual losses
Excess air. Too much air carries heat up the chimney.
- Flue oxygen of 7–8% on a biomass boiler, where 5–6% is achievable, typically wastes 2–4% of fuel.
- An O₂ trim control holds it automatically.
Stack temperature. Every 20 °C above the design stack temperature is roughly 1% of fuel. A feedwater economiser recovers part of this heat.
Steam traps.
- A trap stuck open blows live steam into the condensate line.
- Surveys commonly find 10–25% of traps failed in plants without a maintenance programme.
Blowdown. Continuous blowdown set by a timer, not by measured TDS, throws away hot water.
Condensate not returned. Every tonne of condensate returned saves fuel and water treatment.
Firewood moisture
Wet firewood (40% moisture) gives much less useful heat per kg than seasoned wood (20–25%). Buying by weight without checking moisture means paying for water. Fuel per tonne of steam shows it straight away.
Where to start
- Meter the steam, or the feedwater, and the fuel.
- Log the flue O₂ and stack temperature.
- Survey the traps.
- Then size an economiser or O₂ trim from the data.
Plantmargin tracks all of these live, raises an alarm when fuel per tonne drifts, and values each loss in shillings.