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Acciaierie di Verona (ADV), part of the Pittini Group, where a 1500-kWf absorber had been installed by Danieli to serve the new, 750,000-ton/year wirerod rolling mill and future extensions.

During the first year of operation of the system, the following data were recorded:

- Heat recovery coming from the rolling mill plant;
- Rated power of the pumps for cooling water, of furnace water and of cooling tower water;
- Cooling capacity supplied by the absorption chiller, making it possible to analyze the system from thermal, electrical and Return on Investment (ROI) perspectives.

Diagram of the direct correlation among measured parameters: heat recovery, cooling capacity, A/C water temperature

By re-processing the data, it was possible to note that the best performance of the machine occurs at the maximum demand for chilled water, which coincides with the maximum production peak.

Following the reason why is that in these conditions:

- The process of separating water from lithium bromide is more effective;
- Water (i.e., the refrigerant fluid of the cycle) streams with higher flow;
- The efficiency of the heat exchangers (the evaporator, in particular) increases;
- The overall cooling capacity improves, not only in terms of power (kW), but also as power per water flow (i.e., refrigerant flow) (kJ/kg).

The recorded data of heat recovery vs. cooling capacity shows that the best performance of the machine occurs at the maximum demand for chilled water

Considering the nominal data valid, the following is obtained:

- Internal absorber pump: PaN = 3 kW;
- Electric chiller compressors: PcN = 305 kW;
- Plant operations: L = 6,443 h/year;
- The annual power saved is: ES = Energy Savings = (PaN-PcN)*L = 1,950 MWh/year.

This value equals the yearly energy requirements of more than 500 houses, i.e. a city of 1,500 inhabitants.
As carbon dioxides avoid pollution, it corresponds to about 900 t CO2/year.

Overall first-year data coming from the rolling mill indicate that the return of investment is on average 40%, which coincides with a payback of 2.5 years.

This result depends on cost of energy and on production mix.

SAVE

Yearly electric energy of 500 families' houses

and avoid about

900 tpy of CO2 emissions