buletinul institutului politehnic din iaşi - Universitatea Tehnică ...

Bul. Inst. Polit. Iaşi, t. LVIII (LXII), f. 4, 2012 5
2.2 The Regasification Process of LNG
The Italian natural gas transmission system works with major pipelines at
a pressure rating up to more than 70 bar, then the LNG regasified has to be sent
in the transport pipeline at a pressure of the same order of magnitude.
Fig. 1 – Thermodynamic process during regasification of LNG (La Rocca, 2010).
In principle it is possible to pump natural gas at this pressure after
regasification at a low pressure (Fig. 1, path AB’D’D), but this option isn’t
applied in Europe. When the regasification is carried out at low pressures and,
then, the gas is compressed at the pressure required by pipelines, the pumping
power, WNG, is very high. Instead, if the LNG is pumped in liquid phase, at a
pressure lying in the pressure rating required by pipelines (usually a
hypercritical pressure in Europe) there is convenience because the pumping
power, WLNG, is lower (see Fig.1, path ABCD). The ratio WNG/WLNG is higher
than 20. Moreover, with regasification at hypercritical pressures, the heat
exchange by the LNG side is very good and heat transfer equipment is more
reliable.
In this paper a summary and some results of researches carried out at the
Dipartimento dell’Energia of Palermo are reported.
3. Production of Cold from Regasification of LNG
The research developed on this subject includes both cryogenic
applications and industrial use of cold at very low temperature inside the
regasification site and cold utilization by end users far from the regasification
site in deep freezing facilities and for space conditioning in the commercial
sector (e.g.: Supermarkets and Hypermarkets).
An application that want recovery cold from a regasification plant of
LNG, need to be as close as possible to the regasification site, but this is very
difficult due to safety restriction. LNG is flammable and a fire may take place in
case of leakage, so it is necessary to fix safety distances with other production
site or other activities.