[en] Highlights: • An innovative self-recuperative expander-based integrated process. • Offshore coproduction of LNG, LPG, and Pentane-plus. • Commercial feasibility of integrated LNG-LPG-condensate production process. • Energy and exergy analysis are performed. • Environmental impact in terms of CO₂ emissions was also calculated. -- Abstract: In the current scenario of energy challenges, natural gas (NG) and associated liquids such as liquefied petroleum gas (LPG) are considered to be clean energy sources compared with coal and oil. Liquefaction is one of the most feasible and safe approaches for transporting NG from the site of production to the site of consumption. However, NG processing to produce liquefied natural gas (LNG) and LPG is extremely costly in terms of both operating and capital expenses because it requires a tremendous amount of energy, particularly at offshore sites. We have developed a new liquefaction process that uses N₂ self-recuperation rather than external precooling with 80% less energy consumption than that required by existing single N₂ expander processes. In this work, we evaluate the use of an innovative self-recuperative expander-based integrated process to produce LNG–LPG–pentane plus (condensate) at an offshore site in an energy-efficient manner with minimal capital expenditure. Thermodynamic and economic analyses were performed to evaluate the commercial feasibility of the proposed process. Furthermore, the environmental impact in terms of CO₂ emissions was calculated. This study reveals that LNG–LPG can be produced at a specific energy expense of 0.2362 kW with a payback period of 1.38 years.

[en] Highlights: • A modified refrigerants SMR process was optimized for NG liquefaction. • Recently developed metaheuristic VSO algorithm was proposed. • VSO generates the optimal results for the complex process outstandingly. • Up to 41.5% energy was saved with COP of 32.8%. - Abstract: A metaheuristic vortex search algorithm was investigated for the optimization of a single mixed refrigerant (SMR) natural gas liquefaction process. The optimal design of a natural gas liquefaction processes involves multivariable non-linear thermodynamic interactions, which lead to exergy destruction and contribute to process irreversibility. As key decision variables, the optimal values of mixed refrigerant flow rates and process operating pressures were determined in the vortex pattern corresponding to the minimum required energy. In addition, the rigorous SMR process was simulated using Aspen Hysys® software and the resulting model was connected with the vortex search optimization algorithm coded in MATLAB. The optimal operating conditions found by the vortex search algorithm significantly reduced the required energy of the single mixed refrigerant process by ≤41.5% and improved the coefficient of performance by ≤32.8% in comparison with the base case. The vortex search algorithm was also compared with other well-proven optimization algorithms, such as genetic and particle swarm optimization algorithms, and was found to exhibit a superior performance over these existing approaches.

[en] Highlights: • Asian LNG-exporting countries are studied through product space model. • PRODY, EXPY, proximity, density, strategic value, and open forest are calculated. • Asian LNG-exporting countries have a negligible share in global petrochemical exports. • Indonesia and Malaysia are very close to unexploited petrochemicals. • UAE, Myanmar, and Oman are medium proximate countries. Asian liquefied natural gas (LNG)-exporting countries have large natural gas reserves with a combined LNG export share value of 58% globally. Nevertheless, their global share in petrochemical exports is merely 2.2%. Among the selected countries, Indonesia and Malaysia have exploited 39% and 17% of the products in their petrochemical sectors, but the UAE, Myanmar, Oman, Qatar, and Brunei have exploited only 2%–10%. The significant potential for these countries with regard to exploiting these petrochemical products to scale up their export diversification, in turn leads to sustainable economic growth. The primary reason for their low global share is insufficient knowledge concerning their production capacity, as well as the sector's feasibility and potential with respect to their capabilities. This study thoroughly investigates the export diversification potential and opportunities for Asian LNG-exporting countries by exploring the nexus between LNG and petrochemicals using a product space model (PSM). The results indicate that production of unexploited petrochemicals is imminent in Indonesia and Malaysia, while the UAE, Myanmar, and Oman have moderate opportunities for exploration. These findings can assist policymakers in formulating realistic policies in accordance with their country's capabilities. It will also assist entrepreneurs in identifying potential sectors for establishing new enterprises.

[en] Highlights: • A propane-nitrogen two-phase expander cycle is proposed for natural gas liquefaction. • The proposed process improves the energy efficiency significantly. • The proposed process remains the low global warming potential. • Particle swarm algorithm is used for optimization with exergy analysis. Nitrogen (N₂) expander liquefaction process has the highest ecological and safety advantages over different types of available commercial natural gas liquefaction processes. However, its relatively low energy efficiency is a major issue. In this context, the optimum flow rate of propane as a high-boiling component with low-global warming potential was mixed with conventional refrigerant N₂, resulting in a two-phase single mixed refrigerant appearing at the suction point of the conventional turbo expander. The potential application of a two-phase cryogenic expander was investigated to generate a cooling effect through the expansion of the high-pressure two-phase propane-nitrogen refrigerant. The proposed study was modeled using Aspen Hysys® and optimized by adopting a MATLAB coded particle swarm optimization approach that was linked to Aspen Hysys® using the ActiveX (also known as COM) functionality. The results revealed that the specific energy consumption and required refrigerant flow rate for liquefied natural gas (LNG) production can be reduced up to 46.4% and 27.7%, respectively, in comparison with the conventional N₂ single expander LNG process. Furthermore, the overall energy can be reduced from 79.2% to 29.5% as compared to previously reported N₂ single expander LNG processes, depending on feed conditions, composition, and design parameters. An exergy analysis of the proposed LNG process revealed that the compressors and LNG heat exchanger have the highest exergy loss, i.e., 34.0% and 29.7%, respectively.

[en] Highlights: • Liquefaction is promising approach for long distance H₂ storage and transportation. • Commercial H₂ liquefaction plants have specific energy consumption of 10–12.$\mathit{kWh}/{\mathit{kg}}_{{\mathit{LH}}_2}$. • Increased number of ortho-to-para converters increases the process complexity. • Mixed refrigerant cascaded process with only two catalytic converters is proposed. • Hydrogen is liquefied at the expense of 6.45 $\mathit{kWh}/{\mathit{kg}}_{{\mathit{LH}}_2}$with 47.2% exergy efficiency. To reduce CO₂ emissions and address climate change concerns, most futuristic studies investigating 100% renewable energy sources and subsequent power-to-gas/fuel/liquid/X technological developments have been based on hydrogen (H₂). The long-term storage and transportation of H₂ over long distances restrict its feasibility as an energy vector, mainly due to its low energy density. Liquefaction is a promising approach for overcoming these issues. However, it requires a large amount of energy, and if H₂ itself is used to provide this energy, then 25% to 35% of the initial quantity of H₂ is consumed. The existing H₂ liquefaction plants have specific energy consumption values in the range of 10–12 $\mathit{kWh}/{\mathit{kg}}_{{\mathit{LH}}_2}$ and exergy efficiencies in the range of 20%–30% with complicated configurations. Therefore, a thermodynamically efficient and compact design is required to facilitate a roadmap to H₂ economy. This paper proposes a simple, energy-efficient, and cost-effective process for H₂ liquefaction. Three refrigeration cycles with optimal mixed-refrigerant compositions are used, which makes the proposed process energy-efficient. Additionally, two-stage ortho-to-para conversion makes the process compact. The proposed process is unique in terms of its configuration and mixed-refrigerant combination. The modified coordinate descent approach was adopted to identify the optimal design variables for the proposed H₂ liquefaction process. The proposed process consumes an energy of 6.45 $\mathit{kWh}/{\mathit{kg}}_{{\mathit{LH}}_2}$, which is 36.5% and 16.1% lower than that consumed by the base design of the proposed process and a published base case, respectively. Additionally, the exergy efficiency of the proposed process is 47.2%. This study will help process engineers achieve a sustainable green economy by improving the competitiveness of H₂ storage and transportation over long distances.