Three heat exchangers in a biogas plant. One unit heats the sludge from 45°C to 71°C (1.291 kW). The other two units are for energy recovery : 45 m³/h of digested sludge with a temp. of 71°C pre-heats raw incoming sludge from 35°C to 45°C (497 kW heat transfer). Note the limited footprint of the installation.