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16 Antonino La Rocca et al.
In Fig. 8: ENG (47.7% of ELNG) is the exergy of the exit stream of NG
regasified; EL.CO (25.7% of ELNG) is the exergy of cold available during the
regasification process of LNG delivered in the Ethane condenser (see Fig.2);
EL.CU1 (6.4% of ELNG) is the exergy of cold available during the regasification
process of LNG delivered in the LNG cryogenic heater CU1; EL.CU2 (4.3% of
ELNG) is the exergy of cold available during the regasification process of LNG
delivered in the cryogenic heater CU2; ED.PS (15.9/% of ELNG) represents the
exergy destroyed by the whole amount of pressure losses in the regasification
facility of Fig. 2 by the LNG side.
Fig. 8 shows also a detail of the above parameters and splits each part of
exergy exchanged in the regasification facility indicating the item pertaining to
exergy recovered in the Ethane condenser, in the cryogenic LNG heaters and
the item pertaining the pressure losses in the whole regasification facility.
The exergy delivered in the Ethane condenser requires a thorough
analysis, the results obtained are shown in Fig. 8. The item ER.EL is the part of
LNG exergy which is recovered as electric power produced by the Power Cycle
working with Ethane. This cycle has a mean overall efficiency of a 14% and it
produces a rated power of 3.2 MW (16.7% of input exergy delivered by LNG in
the Ethane condenser), exergy losses in the Ethane pump unit (ED.PU) amounts
to a 0.10% of input exergy. The item ER.PU is the part which is recovered and
then used to drive the Ethane pump and it represents a 0.30% of input exergy.
The ER.CU indicates the exergy recovered in the Ethane preheater CU (see Fig. 2)
and ED.CU indicates the exergy destroyed, the nomenclature used in the Fig.8
with the prefix ER (e.g.: ER.CU1) indicates the exergy recovered in the device
named with the same symbol in Fig. 2, those with the prefix ED (e.g.: ED.CU1)
indicates the exergy destroyed in each device. The item ED.P (7.1% of input
exergy) indicates the exergy destroyed by the pressure losses along the Ethane
Loop.
4. Production of Electric Energy from Regasification of LNG
The analysis performed at Dipartimento dell’Energia, Palermo
University, on this subject includes two ventures: one of them pertains to a CHP
Binary Cycle composed of two Brayton Cycles whose Bottom cycle works with
Helium and another has the Bottom cycle working with Nitrogen but the
pressures of the cycle have been selected, after an optimization analysis, higher
than those pertaining the Process described in (Snamprogetti, 1978). Heat
transfer Equipment proposed are also analysed designing a suitable heat transfer
matrix to improve the processes analysed.
4.1.The Process Proposed
The process proposed for this application is shown in Fig. 9. The Top
cycle includes a modern gas turbine system working at high temperatures which