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Study of the phase equilibrium of natural gas components plays an important role in the designing of LNG plants. Since the problems of equilibrium in two-phase vapor-liquid systems of natural gas hydrocarbons have been extensively studied, investigations are currently focused on multiphase systems of hydrocarbons in mixtures with inorganic substances such as water, carbon dioxide, hydrogen sulfide, hydrogen, and nitrogen. This article dwells on the phase equilibrium of binary mixtures of methane, ethane, and propane with nitrogen. Depending on the ratio of the components and the thermobaric parameters, mixtures of these hydrocarbons with nitrogen may exist as mixtures of mutually soluble components or mixtures of only partially soluble components. The areas of existence of three-phase liquid-liquid-gas system were determined by calculation. The results obtained hold great importance for LNG process design and modernization. [ABSTRACT FROM AUTHOR]

Precise data on the non-variant equilibrium of the four phases (vapor-aqueous solution-ice-gas hydrate) in P - T coordinates are highly desired for developing accurate thermodynamic models and can be used as reference points (similar to the triple point of water). Using the two-component hydrate-forming system CO 2 -H 2 O, we have proposed and validated a new express procedure for determining the temperature and pressure of the lower quadruple point Q 1 . The essence of the method is the direct measurement of these parameters after the successive formation of the gas hydrate and ice phases in the initial two-phase gas-water solution system under intense agitation of the fluids. After relaxation, the system occurs in the same equilibrium state ( T = 271.60 K, P = 1.044 MPa), regardless of the initial parameters and the order of crystallization of the CO 2 hydrate and ice phases. Considering the combined standard uncertainties (±0.023 K, ±0.021 MPa), the determined P and T values agree with the results of other authors obtained by a more sophisticated indirect method. Validating the developed approach for systems with other hydrate-forming gases is of great interest.

Phase-change materials (PCMs) attract much attention with regard to their capability of mitigating fossil fuel-based heating in in-building applications, due to the responsive accumulation and release of thermal energy as a latent heat of reversible phase transitions. Organic PCMs possess high latent heat storage capacity and thermal reliability. However, bare PCMs suffer from leakages in the liquid form. Here, we demonstrate a reliable approach to improve the shape stability of organic PCM n -octadecane by encapsulation via interfacial polymerization at an oil/water interface of Pickering emulsion. Cellulose nanocrystals are employed as emulsion stabilizers and branched oligo-polyol with high functionality to crosslink the polyurethane shell in reaction with polyisocyanate dissolved in the oil core. This gives rise to a rigid polyurethane structure with a high density of urethane groups. The formation of a polyurethane shell and successful encapsulation of n -octadecane is confirmed by FTIR spectroscopy, XRD analysis, and fluorescent confocal microscopy. Electron microscopy reveals the formation of non-aggregated capsules with an average size of 18.6 µm and a smooth uniform shell with the thickness of 450 nm. The capsules demonstrate a latent heat storage capacity of 79 J/g, while the encapsulation of n -octadecane greatly improves its shape and thermal stability compared with bulk paraffin.