# Is insulating the thermopac dust collector worth it in a processing house?

Canonical: https://senseible.earth/answers/thermopac-dust-collector-insulation-saving

Yes, if an air preheater sits after it. BEE's Pali report found bare dust collectors cooling flue gas by 20 C; insulating about 10 m2 keeps that heat for the preheater and saves 23.56 t of pet coke a year. Cost Rs 1 lakh, saving Rs 1.77 lakh, payback about 7 months (2010).

## Why the preheater decides it

The dust collector catches fly ash, which carries unburnt fuel, between the thermopac and the stack. Its bare skin ran above 230 C and the gas lost 20 C crossing it. With high sulphur coke, the air preheater can cool flue gas only to about 180 C, so every degree kept before the preheater is heat it can return to the burner. With no preheater, insulating the collector just sends the same heat up the chimney.

## The arithmetic

- 250 kg of coke an hour with 27 kg of air per kg: 7,000 kg of flue gas an hour.
- 7,000 x 0.23 x 20 C = 32,200 kcal an hour.
- 20 hours a day, 300 days: 193.2 million kcal / 8,200 = 23.56 t of coke.
- At Rs 7,500 a tonne, Rs 1.77 lakh against Rs 1 lakh: about 7 months.
- This assumes the preheater recovers all 20 C it gets back.

## What to buy

Rock wool mattress with cladding, or removable jackets so the collector can still be opened for cleaning. The report prices 10 m2 at Rs 0.84 lakh plus Rs 0.16 lakh fitting, with no downtime.

## Do it in this order

1. Tune the air damper: the report's 27 kg of air per kg of coke is more than twice what pet coke needs to burn.
2. Fit the air preheater.
3. Insulate the dust collector and the duct between them.

## One thermopac, one year

- Heat kept: 32,200 kcal an hour x 6,000 h = 193.2 million kcal
- Coke saved: 193.2 million / 8,200 = 23.56 t
- CO2: 23.56 x 3.17 = 74.7 t
- The report says 64 t, using a lower factor

Pet coke at the IPCC 2006 default, 3.17 t CO2 a tonne (32.5 GJ a tonne x 97.5 kg CO2 per GJ). An estimate; a lab analysis of your own coke is better.

## What Senseible does here

Senseible keeps each pet coke invoice as a monthly tonnage record, so the preheater and insulation savings show in sequence. With no pet coke factor of its own, apply the 3.17 above. For a loan on the preheater, run the green loan check.

- [Green loan readiness check](https://senseible.earth/green-loan-check)
- [Thermopac air preheater: pet coke saved](https://senseible.earth/answers/thermopac-air-preheater-petcoke-saving)
- [Boiler excess air and fuel saving](https://senseible.earth/answers/boiler-excess-air-fuel-saving)
- [Pet coke emission factor in India](https://senseible.earth/answers/petcoke-emission-factor-india)
- [Steam pipe insulation heat loss](https://senseible.earth/answers/steam-pipe-insulation-heat-loss)

Sources: [BEE, Detailed project report: insulation of dust collector in thermopac, Pali textile cluster (2010, SAMEEEKSHA)](https://sameeeksha.org/pdf/dpr/PAL_TXT4.pdf), [BEE, Detailed project report: air pre heater in thermopac, Pali textile cluster (2010, SAMEEEKSHA)](https://sameeeksha.org/pdf/dpr/PAL_TXT1.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 2026-11-01. Report figures are from a BEE SME programme project report; costs and paybacks are at the report year's prices. Check today's fuel and power prices and a current quote before you rely on the payback.