Utilizing Liquefied Natural Gas Cold Research Articles

Finite sum based thermoeconomic and sustainable analyses of the small scale LNG cold utilized power generation systems

Liquefied natural gas (LNG) cold utilized micro cogeneration systems are the feasible and sustainable solutions for the inland regions where the large scale LNG cold utilization or the conventional pipeline systems are not economically applicable. The present study investigates the single and combined systems in three LNG importing countries by using the finite sum modeling which is firstly performed for the LNG cold utilization systems with the sustainability index assessment. To generate electricity, the microturbine is integrated with an LNG vaporizer and an LNG pump in the single system while the combined system includes a Stirling engine and a thermal energy storage tank in addition to the microturbine and LNG cold utilization components. Thermodynamic, environmental, thermoeconomic and sustainable analyses are performed to obtain their yearly performance maps that are extremely difficult to obtain with the conventional dynamic modeling. The yearly performance trends of the net power generation rate, exergetic efficiency, and the levelized product cost are found similar to each other while they have contrary yearly trends with the overall energetic efficiency and the Stirling engine performance parameters. The net generated power rate, the Stirling engine performance parameters, the levelized product cost, the emission rate and the sustainability index have significant changes which must be considered for the real applications while the other factors are able to be neglected during the dynamic analysis since their fluctuations are small. The most convenient time are found at 08:00 am in all the case countries though the corresponding months change for each case country. The combined system is found more feasible than the single system from the thermodynamic, thermoeconomic, environmental and sustainable viewpoints.

Thermoeconomic and environmental assessments of a combined cycle for the small scale LNG cold utilization

Liquefied natural gas (LNG) cold utilized micro-cogeneration systems can be used as a part of small scale LNG regasification processes. The study proposes a LNG cold utilized micro-cogeneration system which combines a Stirling engine and a micro gas turbine. The combined system is compared to a conventional micro-cogeneration system the point of thermodynamic, environmental and thermoeconomic views. Parametric studies are conducted in the ranges of 288.15–313.15K for the ambient air temperature and 3–4 for the compressor pressure ratio, respectively. Thermodynamic efficiencies and power generation rates are studied in thermodynamic analyses while carbon dioxide emission rates and the relevant emission reductions are observed in environmental analyses. An original exergy-cost matrix is produced for the combined system and thermoeconomic comparison is performed between the combined system and the conventional micro-cogeneration system. It is found that the combined system provides 7.8% higher power generation rates whereas it has 1% and 2.4% higher energetic and exergetic efficiencies, respectively at the actual pressure ratio of the micro gas turbine. Emission reductions are observed as 3.9%, 7.8% or 8% at individual pressure ratio of 3, 3.64 or 4. The unit fuel costs are calculated for the system components and it is deduced that the combined system has higher unit fuel costs at the lower pressure ratios. It is found that the single system has roundly 25% less levelized product cost than the combined system at the actual pressure ratio. A simple graphic-based thermoeconomic optimization study demonstrates that the minimum relative cost differences are at different locations for the combined cycle.

LNG ocean transportation: experience and prospects

There are increasing liquefied natural gas (LNG) demands from many parts of the world because LNG is now considered safe and is less polluting. The demands are to be met by an increase in new liquefaction plants that are based from the unconventional gas and new discoveries. The new liquefaction plants under consideration will be built with higher efficiency in environmentally responsible manners. This means the whole LNG supply chain, from the well heads, gas treatment, liquefaction,; transportation, and regasification, must be designed and configured with low emissions and high efficiency. Additionally, there is also a drive to lower the cost of natural gas liquefaction and improve the value of the LNG regasification plant. This chapter discusses the development, advances, innovations, and new ideas in the LNG supply chain. The focus will be on more efficient liquefaction technology, larger and higher efficiency drivers, improved liquefaction equipment design, NGL recovery, LNG regasification, and LNG cold utilization. The applications of some of these technologies may further improve the image of the LNG industries.