How much fuel does automatic temperature control on a zinc bath save?

Holding a Howrah zinc bath at 500 °C instead of 520 °C with an automatic controller saves 4,442 litres of furnace oil a year in BEE's study, 3.8% of the furnace's 118,080 litres. That is 13.2 t CO2, not the report's 15 t. Cost Rs 2.34 lakh; payback 1.8 years at Rs 30 a litre.

Why baths run hot

IS 2629:1985 suggests a zinc bath of 440 to 460 °C. Howrah units run 480 to 520 °C to keep output up and help the centrifuge shed excess zinc, and operators keep it high to be safe when job sizes change. BEE found 490 to 500 °C, held steady, enough for production. A hotter bath burns more oil and makes more dross and ash, so zinc is lost too.

What the controller is

• A thermocouple in the bath and a temperature controller.
• A VFD panel on the 0.37 kW fuel pump and the 15 kW blower, so the firing rate follows bath temperature.
• Air control is a separate project in BEE's series; this one sets the fuel rate only.
• Cost: Rs 2.25 lakh for the system plus Rs 0.09 lakh other, Rs 2.34 lakh.

How the 4,442 litres was worked out

The unit galvanizes 2,399 t a year: 2,229 t of steel and 170 t of zinc. Heating that metal to 500 °C instead of 520 °C takes 5.13 million kcal less a year. Divided by the furnace's low efficiency, about 12%, that is 4,442 litres of oil, 3.8% of what it burns.

Two checks on the report

• Money: 4,442 x Rs 30 = Rs 1,33,260; Rs 2.34 lakh pays back in 1.76 years. At your oil price, the saving is 4,442 times the price per litre.
• CO2: it claims 15 t at 3.24 t per tonne of oil, but 4,442 litres is 4,087 kg, and even its own factor gives 13.2 t. At 2.97 kg per litre it is also 13.2 t.

Records that show it worked

1. The controller's bath temperature log.
2. Furnace oil per tonne galvanized, month by month.
3. Zinc bought per tonne galvanized, which should fall as dross falls.

One furnace, one year

• Oil saved: 4,442 L x 2.97 = 13.2 t CO2
• Oil before: 118,080 L x 2.97 = 350.7 t CO2
• Share cut: 13.2 / 350.7 = 3.8%
• Money at Rs 30 a litre: Rs 1,33,260; at Rs 60, Rs 2,66,520 and under a year to pay back

Furnace oil at 2.97 kg CO2 per litre. Oil price is the report's; use your own invoice price.

What Senseible does here

Senseible reads furnace oil invoices into monthly records at 2.97 kg CO2 per litre; add tonnes galvanized and the drop in oil per tonne shows month by month. The calculators give a quick CO2 figure.

• Carbon calculators
• Galvanizing furnace air preheater
• Galvanizing energy per tonne benchmark
• Hot-dip galvanizing footprint

Sources: BEE, Detailed project report: temperature control in zinc bath in galvanizing, Howrah galvanizing and wire drawing cluster (SAMEEEKSHA)

Last reviewed 2026-10-31.