# How much furnace oil does an oxygen sensor on a galvanizing furnace save?

Canonical: https://senseible.earth/answers/galvanizing-furnace-oxygen-sensor-blower-vfd-saving

About 17,400 litres a year, 15% of a 112,500 litre unit, in the Bureau of Energy Efficiency (BEE) report for Howrah. A zirconia oxygen probe trims blower speed through a variable frequency drive (VFD), cutting excess air from 110% to a 15% target. Cost Rs 4.68 lakh, saving Rs 5.22 lakh, payback 0.9 years at 2010 prices.

## What BEE measured

- A zinc furnace burning 31 litres of oil an hour, 12 hours a day, 300 days a year, with the vat at 467 C and flue gas at 520 C.
- Oxygen in the flue gas was 11%, which is about 110% excess air.
- Furnace efficiency by the direct method was 19.28%.
- Air is set by hand with a damper on a 15 kW blower.

## What is fitted

A zirconia oxygen probe in the flue, a control panel with a variable frequency drive on the blower motor and fuel pump, calibration gas bottles and an auto calibration unit. No change to the burner or furnace. The report allows 2 to 3 days of downtime, a 12 week schedule and about 8 years of life. Its named risk is flue gas leaking where the probe goes in.

## Check before you buy

- Read your own flue oxygen with a portable analyser first. A 15% excess air target is about 2.7% oxygen, so a furnace already near that has little to save.
- The sum assumes 3,600 operating hours. Use your own.
- The report counts only the fuel saving, not the blower electricity that the drive will also cut.

## The saving, step by step

- Air now: 897 kg an hour. At a 15% excess air target: 492 kg an hour. Less air to heat: 405 kg an hour
- Heat that no longer goes up the stack: 405 x 0.24 x (520 minus 40) = about 46,700 kcal an hour
- Oil: 46,700 / 10,500 kcal a kg = 4.45 kg an hour, or 4.83 litres an hour at 0.92 specific gravity
- Per year: 4.83 x 12 x 300 = about 17,400 litres, which is 15% of 112,500 litres
- Money: 17,400 x Rs 30 = Rs 5.22 lakh. Payback 4.68 / 5.22 = 0.90 years, about 11 months
- CO2: 17,400 x 2.97 kg = 51.7 tonnes (t) a year, against 55 t in the report

Furnace oil at 2.97 kg CO2 a litre, an estimate from Intergovernmental Panel on Climate Change (IPCC) carbon content. Figures from the report; costs at its prices.

## What Senseible does here

Senseible reads furnace oil invoices into monthly litres and carbon dioxide equivalent (CO2e) at 2.97 kg a litre, each linked to its bill, so the drop after the sensor shows against the months before. The green loan check shows what a lender asks for.

- [Green loan readiness check](https://senseible.earth/green-loan-check)
- [Furnace air ratio and oxygen targets](https://senseible.earth/answers/furnace-air-ratio-oxygen-target)
- [Air preheater on a galvanizing furnace](https://senseible.earth/answers/galvanizing-furnace-air-preheater-oil-saving)
- [Galvanizing plant energy per tonne](https://senseible.earth/answers/galvanizing-plant-energy-per-tonne-benchmark)

Sources: [BEE, Detailed project report: air fuel ratio control with oxygen sensor, Howrah galvanizing and wire drawing cluster (2010, SAMEEEKSHA)](https://sameeeksha.org/pdf/Howrah_galvinising/DPR_on_Air_Fuel_Ratio_Control_with_Oxygen_Sensor.pdf), [IPCC 2006 Guidelines, Volume 2 Energy, Tables 1.2 and 2.3](https://www.ipcc-nggip.iges.or.jp/public/2006gl/vol2.html)

Last reviewed 2026-11-04. Report figures are from a BEE SME programme project report; costs and paybacks are at the report year's prices. Check today's prices and a current quote before you rely on the payback.