The intervention carried out consists in reusing the heat contained in the fumes leaving a steam generator in order to preheat the food water entering the generator and to heat the process water to 80 °C. Before the intervention, the process water was taken directly from the aqueduct and heated by means of heat produced onerous. The water of the boiler food, on the other hand, was not preheated. A single 2-stage heat recovery system was built:
- ECO (economiser) heats 5,000 l/h of food water from 90 °C to 121 °C
- RC2 (second stage) heats 2,700 l/h of process water from 15 °C to 60 °C.
The heat recovery system was installed simultaneously with a new 15 t/h steam generator, replacing an old boiler, increasing its efficiency from 90% to over 100%. The fumes are cooled from about 200/180 °C (depending on the instantaneous thermal load of the boiler) to about 48 °C. Before release into the atmosphere, the produced condensate is collected and disposed of.
Results obtained:
- Thermal energy saving: 2.574.000 kWh/year
- Primary energy saving: 221 Toe/year
- Saving of natural gas: 265.000 scm/year
- CO2 not released into the atmosphere: 523 tons/year
- Payback intervention: about 11 months
The new system has been equipped with a monitoring system able to measure and historicize the post-intervention consumption essential for the final balance and the verification of the energy savings achieved.
The intervention has been analysed, designed and implemented by RENOVIS.