A pinboard by
Arnab Dutta

Research Scholar, National University of Singapore


Cost effective utilization of cold energy associated with LNG [Liquefied Natural Gas]

Energy has become an indispensable part of our daily lives. Energy demand is expected to grow in the years to come. Currently fossil resources are expected to meet our growing energy demand and dependence on fossil fuel will continue. With increasing exploration of various unconventional natural gas resources, the world is all set to enter the ‘golden age of gas’. Natural gas being the cleanest fossil resource, and owing to its abundant availability there is a major shift towards natural gas as an energy resource. However, natural gas reserves are not uniformly distributed all over the world. Hence, natural gas will either be transported via pipelines or in liquefied form (LNG) to meet the rising global demand for natural gas. LNG is the preferred mode of transportation for long distances and it is expected that in near future LNG trade will nearly be double. With many new LNG regasification terminals being proposed worldwide, it is worthy to investigate process integration opportunities within a LNG regasification terminal. LNG comes with a lot of cold energy that has the potential to be utilized. However, currently the entire cold energy is wasted. In this context, I am using process simulation and optimization as a tool to come up with different process configurations to cost effectively utilize this available cold energy. This is expected to increase the overall worth of a regasification terminal both in terms of sustainability as well as from economics view point.


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

Abstract: 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 288.15–313.15 K 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.

Pub.: 09 Feb '17, Pinned: 16 Aug '17

Optimal design and integration of a cryogenic Air Separation Unit (ASU) with Liquefied Natural Gas (LNG) as heat sink, thermodynamic and economic analyses

Abstract: LNG regasification terminals are the final destination of LNG carriers. This is where the liquefied natural gas is returned to the gaseous state and fed into transmission and distribution grids. While regasification process, cryogenic LNG has a great potential for cold energy recovery. This cold energy can be used in various applications such as power generation, material freezing and sea water desalination. In this study, we used the mentioned cold energy for cryogenic air separation unit to improve the performance of this cycle. Some of the most important results of this integration are 8.04% reduction in the amount of power requirement and also 17.05% reduction in initial capital cost of ASU plant. In this paper, the required LNG flow rate for applied integration was 24.43% of ASU cycle generated oxygen flow rate. Annualized cost of system was chosen as an economic approach. A year reduction of system period of return in relation to the before integration of ASU cycle with LNG, was the most important economic result of this integration. Sensitivity analysis was done on the system economic parameters (electrical energy, oxygen and nitrogen price). The results show that the considered integration will have a more positive impact on the system period of return in higher prices of electrical energy and also in lower prices of oxygen in the market.

Pub.: 21 Mar '17, Pinned: 16 Aug '17