Liquefied natural gas (LNG) is attracting great interest
as a clean
energy alternative to other fossil fuels, mainly due to its ease of
transport and low carbon dioxide emissions, a primary factor in air
pollution and global warming. It is expected that this trend in the
use of LNG will lead to steady increases in demand over the next few
decades. To meet the growing demand for LNG, natural gas liquefaction
plants have been constructed across the globe. Furthermore, single
train capacity has been increased to strengthen price competitiveness.
To achieve greater capacity, more complex refrigeration cycle designs
that combine two or more different conventional single refrigeration
cycles are being developed to obtain synergistic effects in the liquefaction
process. At the same time, a variety of recent studies have focused
on designing suitable processes for offshore and small-scale plants
to improve the profitability of stranded gas fields. LNG plants are
known to be energy/cost-intensive, as they require a large amount
of power for the processes of compression and refrigeration, and need
special equipment such as cryogenic heat exchangers, compressors,
and drivers. Therefore, one of the primary challenges in the LNG industry
is to improve the efficiency of the current natural gas liquefaction
processes in combination with cost savings. In this paper, we review
recent developments in LNG processes, with an emphasis on commercially
available refrigeration cycles. We also discuss recent research and
suggest future directions for natural gas liquefaction processes.
Up to this point, most studies have focused on operating cost. To
achieve better results, future studies that investigate optimal design
and operation of LNG technologies should consider both capital cost
and operating cost.
One of the most important challenges in a natural gas liquefaction plants is to improve the plant energy efficiency. In particular, if part of the natural gas is used as a fuel gas or the liquefaction ratio is taken into account as a design factor in an liquified natural gas (LNG) plant, process design focusing on cold energy recovery is an attractive option. In this study, various energy recovery-oriented process configurations and the potential improvements of energy savings in LNG plants were analyzed. Our primary focus for energy recovery in the LNG liquefaction process was centered on utilizing the flash gas stream from the phase separator. The applicability of the proposed configurations was validated by modeling and simulation of the single mixed refrigerant (SMR), propane precooled mixed refrigerant (C3MR), and single nitrogen (N2) expander processes. The simulation results for all cases exhibited considerable reductions of refrigerant flow rates, seawater cooling duties, and the specific work. For example, when the liquefaction ratio was fixed at 0.90, the amount of refrigerant was reduced by 4−5% by employing configuration 1, which recovers cold energy from the flash gas in LNG heat exchangers. This also led to 4−5% reductions of the specific work and seawater duty. Any energy recovery configuration will result in a considerable energy consumption reduction as the natural gas liquefaction process consumes a large amount of energy. Therefore, the optimization of energy recovery configurations in the natural gas liquefaction process is highly recommended with the objective of maximized energy savings considering capital costs.
This study focuses on the techniques of improving refinery reliability, profitability, and availability. In this study, a corrosion control document (CCD) knowledge base system in crude oil distillation unit process is developed. CCD consists of numerous parts namely damage mechanisms (DM), design data, critical reliability variables (CRV), guidelines, etc. To develop CCD, first off, a material selection diagrams (MSD) is drawn. The DM of each process effecting equipments that are based on American Petroleum Institute 571 should be chosen. Operating variables affecting severity of DM are selected in the beginning stage of CRV. Finally, guidelines are provided for the reliability of equipments.
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