buletinul institutului politehnic din iaşi - Universitatea Tehnică ...

Bul. Inst. Polit. Iaşi, t. LVIII (LXII), f. 4, 2012 19
44.96 MW. The gas consumption is a 5,7% of the quantity regasified but only a
3% is attributable to the regasification process. The overall electric efficiency of
the CHP cycle is 43% and the whole efficiency of the CHP cycle is 69%.
Considering a mean Lower Heating Value for NG of 36,209 kJ/Stm 3 (8,560
kcal/Stm 3 ) the gas consumption is 108.69 ×10 6 Stm 3 /y which correspond to
94.00 ktoe/y of primary energy. The amount of electric energy produced is
469.73 GWh/y. Bearing in mind these values, the primary energy need in Italy
to produce the same amount of electric energy is of 103.33 ktoe/y, so there is a
primary energy saving of 9.33 ktoe/y.
4.2.2. The Proposed CHP Plants Working with Nitrogen. The process
proposed is seeming to the other working with Helium (Fig. 9). The Top cycle
includes a modern gas turbine system working at high temperatures which is
shown in the higher part of figure at left. The bottom Cycle, which is shown in
the higher part of figure at right, works with Helium, the higher pressure is 37.4
bar and the lower is 5 bar; the temperature of Nitrogen at the inlet in GTbottom
turbine is 479°C, then Nitrogen coming out of gas turbine gives heat to LNG in
the Cryogenic Regasifier and it is cooled down to -129°C, is then pumped by
the Cryogenic Compressor C2 and at the exit it has a temperature of 0°C. The
values reported pertain to a modular plant with a regasification capacity of 2
×10 9 Stm 3 /y when working 24 h a day all a year around (270 days).
The mean net power inlet in bottom cycle is 67.96 MW, the mean
Electric production 22.28 MW and 44.03 MW is the thermal power exchanged
in the cryogenic regasifier. The mean electric efficiency is of a 33%. The mean
electric efficiency of top cycle is of a 27%; the thermal power furnished is 146.3
MW and gross thermal power recovered by flue gas is 70.04 MW while the
Electric power produced is 39.00 MW. The gas consumption is a 4,9% of the
quantity regasified but only a 3% is attributable to the regasification process.
The overall electric efficiency of the CHP cycle is 42% and the whole
efficiency of the CHP cycle is 72%. Considering a mean Lower Heating Value
for NG of 36,209 kJ/Stm 3 (8,560 kcal/Stm 3 ) the gas consumption is 94.24 ×10 6
Stm 3 /y which correspond to 80.00 ktoe/y of primary energy. The amount of
electric energy produced is 397.05 GWh/y. Bearing in mind these values, the
primary energy need in Italy to produce the same amount of electric energy is of
87.00 ktoe/y, so there is a primary energy saving of 7.00 ktoe/y.
4.3. Comparison Between CHP Modular Plants Working with Helium or Nitrogen
The advantage offered by use of innovative modular CHP plants
proposed in comparison with OR evaporators technology is mainly attributable
to reduced environmental impact of cold released in the sea near the
regasification site (mean avoided release of cold: 740…750 kJ/kg of LNG
regasified); other benefits follow from the use of such a kind of CHP innovative