Utilization of Cryogenic Exergy of LNG by MGT (Mirror Gas Turbine)

Abstract

In the course of the worldwide efforts to suppress the global warming, the saving energy becomes more important. Recently, the LNG (liquefied natural gas) terminals in our country have received more than 50 million tons of LNG per year. Therefore, the utilization of the cryogenic exergy in connection with the regasification of LNG gains more and more importance. The aim of this paper is the recovery of the energy consumed in liquefaction using the MGT (Mirror Gas Turbine), which is a kind of new combined cycle of a conventional gas turbine worked as a topping cycle and TG (inverted Brayton cycle) as a bottoming cycle. The optimum characteristics have been calculated and it is shown that this cycle is superior to the current-use gasification systems in employing seawater heats in terms of thermal efficiency and specific output. In the present cycle, the cold of LNG is used to cool the exhaust gas from a turbine of TG, and then the exergy of the liquefied natural gas is transformed to electric energy with a very high efficiency. The main feature of this new concept is the removal of an evaporation system using seawater.

System Analysis of Waste Heat Applications With LNG Regasification

“…Since the 1970's Japan has been operating LNG receiving terminals for power generation using Rankine cycles and direct expansion of natural gas, accounting for about 85 MW installed capacity (2004) with first-law electrical efficiencies between 13-23% 1 [13]. In recent years several alternative methods have been under R&D, reporting theoretical efficiencies up to 60% or more.…”

“…Seawater is delivered to an overhead distributor at the top of the ORV and it flows downwards, transferring heat to the LNG that flows upwards inside the tubes ( Figure 6) [14], [15]. In terms of power consumption, an ORV demands approximately 0.008 kWh/kg LNG to pump the seawater [13]. Aluminum alloy is used as construction material for the ORV since it possesses good mechanical characteristics at low temperatures, excellent thermal conductivity and workability.…”

“…LNG receiving terminals for power generation have been used in Japan since the 1970's and up to 2004 the installed electric power capacity was about 85 MW (see Table 2) [13]. The selected technologies in these plants are: i) Rankine cycles with organic or inorganic materials as working fluid and ii) direct expansion turbines with and without recuperation and reheating.…”

“…The selected technologies in these plants are: i) Rankine cycles with organic or inorganic materials as working fluid and ii) direct expansion turbines with and without recuperation and reheating. Electric efficiencies for the mentioned technologies are between 13-23% [13]. …”

Proposal of the Atmospheric Pressure Turbine (APT) and High Temperature Fuel Cell Hybrid System

“…The authors have already conducted the basic experiment on the inverted Brayton cycle (3) , and proceed to evaluate conceptually its applications and potentialities of a new combination of Brayton/inter cooled inverted Brayton cycle on a basis of thermal efficiency (4), (5) . Hybrid heat engines are power generation systems in which a heat engine, such as a micro gas turbine, is combined with a non-heat-engine, such as a fuel cell.…”