# How fast does waste heat recovery on a ceramic roller kiln pay back?

Canonical: https://senseible.earth/answers/roller-kiln-waste-heat-recovery-saving

In under a year at 2010 prices. BEE's Morbi report fits a recuperator to a vitrified tile roller kiln's preheating zone exhaust, warming burner air to about 175 C and saving 295 scm of gas a day, 3.1% of the kiln's use. Cost Rs 8.46 lakh, saving Rs 10.44 lakh a year, about 143 t CO2.

## Which exhaust this uses

A roller kiln has two hot exhausts. Most Morbi units already send final cooling zone air, at 250 to 300 C, to their dryers. This project takes the other one: flue gas from the preheating zone, which leaves at about 249 C. A shell and tube recuperator of 32 m2 cools it to about 125 C and passes the heat, about 108,000 kcal an hour, to the combustion air.

## The audited kiln

- 5,929 m2 of vitrified tile a day (15,980 tiles), firing at about 1,223 C.
- 9,540 scm of gas a day, about 1.61 scm per m2.
- Preheating zone flue gas carried about 5% of the heat input.
- 236 working days a year in the report's sums.

## Cost and payback

- Recuperator Rs 6.90 lakh, fitting Rs 0.35 lakh, taxes Rs 0.35 lakh, interest Rs 0.18 lakh, contingency Rs 0.69 lakh: Rs 8.46 lakh.
- Saving: 295 scm x 236 days = 69,620 scm at Rs 15 = Rs 10.44 lakh. The cover table labels this kWh; it is scm.
- Payback 0.8 years. At 330 firing days the saving rises to about 97,000 scm.
- Twelve days of kiln downtime to fit the ducting.

## Keep the saving

- Log flue temperature after the recuperator weekly; a rise means fouling.
- Check burner air pressure after fitting, since hot air takes more volume and burners may need retuning.
- Track gas per m2 fired, not monthly gas, which moves with output.

## One kiln, one year

- Gas saved: 295 scm x 236 days = 69,620 scm
- CO2 saved: 69,620 x 2.05 = 142.7 t
- Per m2: 1.61 scm (3.30 kg CO2) falls to 1.56 scm (3.20 kg)
- The report's own figure is 142 t

Natural gas at our factor of 2.05 kg CO2 a scm, an estimate.

## What Senseible does here

Senseible reads gas bills into monthly records with CO2 at 2.05 kg a scm, so gas per m2 before and after the recuperator can be shown to a lender or an EU buyer. The green loan check shows what a lender asks for.

- [Green loan readiness check](https://senseible.earth/green-loan-check)
- [Morbi tile kiln gas and CO2 per m2](https://senseible.earth/answers/morbi-tile-kiln-gas-carbon-per-square-metre)
- [Low thermal mass kiln cars](https://senseible.earth/answers/tunnel-kiln-low-thermal-mass-car-gas-saving)
- [Morbi ceramic cluster carbon footprint](https://senseible.earth/answers/morbi-ceramic-cluster-carbon-footprint)

Sources: [BEE, Detailed project report: waste heat recovery in roller kiln, Morbi ceramic cluster (2010, SAMEEEKSHA)](https://sameeeksha.org/pdf/dpr/MRV_CRM13.pdf)

Last reviewed 2026-10-31. Report figures are from a BEE SME programme project report at 2010 prices, when gas cost Rs 15 a scm. Redo the payback with today's gas price and a current quote.