The intervention consists in recovering the heat contained in the fumes coming out of three steam generators in order to:
- Preheat the boiler feed water;
- Preheat the make-up water for the boilers;
- heat diathermic water for winter microclimate use;
- Preheat the water used for the process washings.
Before the intervention, no recovery of the thermal waste had ever been implemented in the plant configuration of the thermal plant. A single 3-stage heat recovery system was therefore built for smoke/water heat exchange:
- ECO (centralized economizer) heats 7.150 l/h of food water from 80 °C to 120 °C
- RC2 (second heat recovery stage) heats 2.700 l/h of make-up water from 15 °C to 60 °C
- RC3 (third heat recovery stage) heats closed-circuit diathermic water from 35°C to 55°C.
The third stage of heat recovery (RC3) is also used for the preparation of hot water for production, precisely for process washing. The fumes are cooled from about 195 - 230 °C (depending on the instantaneous thermal load of the boiler) to about 40 °C. Before release into the atmosphere, the condensate produced is separated, treated and disposed of.
Results obtained:
- Thermal energy saving: 3.517.920 kWh/year
- Primary energy saving: 302 Toe/year
- Saving of natural gas: 362.000 scm/year
- CO2 not released into the atmosphere: 715 tons/year
- Payback intervention: about 36 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.