Industrial heat pumps and vapour recompression

Raising low-grade waste heat to a useful temperature.

Recovery and reuse · Shared heat and everyday recovery · No. 136

• Recovery and reuse
• Heat grade: Low (below 230 C)

An evaporator that recompresses its own steam can do with 30-50 kWh what once took a whole tonne of steam.

Chart: Illustration: Industrial heat pumps and vapour recompression

Where it comes from

Chart: Map of where it comes from

Industrial heat pumps use electricity to lift heat from a temperature nobody can use to one a process needs. Mechanical vapour recompression does it by squeezing the steam boiled off in an evaporator.

Three things to know

1. About 75% of heat demand in less energy-intensive industries is below 200 C, the range heat pumps now reach.
2. A heat pump at COP 4.5 beats a gas boiler on CO₂ on any grid below about 1 kg CO₂ per kWh, including coal-heavy ones.
3. Running an electric boiler cost about 4 times as much as gas in the US in 2024, but only 2 times in China.

The journey

1. 1 Waste heatCooling water, dryer exhaust, evaporator vapour
2. 2 EvaporatorRefrigerant picks up the low-grade heat
3. 3 CompressorElectricity lifts it to 140-160 C
4. 4 CondenserReleases heat into process water or steam
5. 5 Process useDrying, pasteurising, evaporation, distillation

Go deeper pick a tab to open it in full