Compressed air and dye-house hot water often run on the same shifts, yet heat leaves one room as fuel is burned in another.
TCF POST Desk
Textile mills may be throwing away a large share of the energy they pay for in their compressor rooms. Atlas Copco, a compressor maker, said up to 94% of a compressor’s electrical input can be converted into compression heat in suitable installations. The company argues that this heat is often released outdoors while the dye house burns fuel to heat water.
The company framed dyeing and finishing as a strong fit because the two utilities often run at the same time. Compressed air drives pneumatic controls and production equipment, while the dye house needs thermal energy for dye baths, washing, steam generation and drying. Atlas Copco said mills could use both outputs of the same electrical input.
What the numbers mean
Atlas Copco said suitable hot-water recovery systems may deliver water at around 70–90°C. It cautioned that the actual temperature depends on compressor design, loading, inlet-water temperature and heat-exchanger configuration.
The company put the thermal load in context: heating 1,000 litres of water by 20°C takes roughly 23 kWh, before losses. On that basis, a 100 kW compressor at the 94% ceiling would yield about 94 kW of heat, enough to lift around 4,000 litres by 20°C every hour. That figure is an illustrative calculation from the company’s numbers, not a result Atlas Copco reported. Real systems would recover less.
Where the heat comes from
Atlas Copco identified three sources: the oil circuit in oil-injected screw compressors, the aftercooler that cools compressed air, and the cooling air or water that carries heat away from the machine. An oil-to-water heat exchanger can pass oil-circuit heat to a separate water loop without mixing the fluids, the company said. Water-cooled, oil-free machines can feed larger, steadier volumes of hot water, it added.
A preheater, not a boiler replacement
The company stressed limits. Recovered heat would preheat process water, boiler feedwater, and washing and rinsing water, and could support drying-air systems. Existing boilers or steam systems would still supply the final temperature rise, and high-temperature stenters and finishing lines would keep their own heaters. Atlas Copco said recovery typically supplements the boiler rather than replacing its high-temperature duty.
The deciding factor: timing
Atlas Copco said the project stands or falls on whether compressor running hours overlap with real heat demand. A compressor running overnight contributes little to daytime heating unless storage is economical. It recommended starting with one dependable heat user, such as process-water or boiler-feed preheating, and gave a four-step savings method:
- Estimate the usable heat recovered each year.
- Multiply it by the cost of the boiler fuel it displaces, adjusted for boiler efficiency.
- Deduct pump electricity, maintenance and distribution losses.
- Compare the net savings with installed cost.
For Indian mills, the company noted, fuel tariffs and production schedules can materially affect payback.
Where recovered heat is too cool for the process, Atlas Copco said an industrial heat pump may lift it, provided the extra electricity and equipment costs are justified.
Equipment on offer
Atlas Copco pointed to energy recovery systems for its GA oil-injected compressors and ER 90-900 units for water-cooled, oil-free Z compressors. In its ZR/ZT oil-free range, ZR machines are water-cooled and ZT machines are air-cooled, and the company said the right recovery setup must be confirmed for each model.
