Nitrogen removal from natural gas: Phase II

Abstract In 2018, China’s natural gas import reached 90.39 million tons, and the liquefied natural gas (LNG) import was 53.78 million tons, accounting for 59.5% of total natural gas imports. With the construction of LNG terminals, more studies on the leakage of LNG storage and transportation facilities have emerged to prevent catastrophic consequences such as explosions and frostbite. However, most of previous researches focused on gas pipeline leakage after LNG gasification, and few of those have been done on LNG liquid pipeline leakage. In this paper, Fluent software is used to numerically simulate the process of LNG liquid pipeline leakage. After the occurrence of LNG leakage, it will suffer the process of endothermic, evaporation, and diffusion, which is considered as a two-phase diffusion process. The Euler-Lagrangian method is introduced to simulate the diffusion process of gas phase and liquid phase separately. In the simulation, the liquid phase is regarded as discrete droplets for discrete processing. The movement trajectory, heat transfer process and evaporation process of each droplet are tracked respectively. Different from the liquid phase, the gas phase is regarded as a continuous phase and the Navier-Stokes equations are adopted for calculation. Thereafter, coupling calculations of two phase are performed to determine the concentration field and temperature field of the LNG liquid pipeline leakage. As a supplement to this research, the influence of wind speed on LNG leakage and diffusion process is analysed in detail. Finally, the numerical simulation method is applied to a coastal LNG terminal in northern China to determine the distribution of natural gas concentration and temperature, as well as delimit the combustion range. The results can provide scientific reference for the delimitation of risky zones and the formulation of emergency response strategy.

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Processing of natural and casing-head gases by the gas-phase oxidation

Kataliz v promyshlennosti ◽

10.18412/1816-0387-2021-4-227-237 ◽

2021 ◽

Vol 21 (4) ◽

pp. 227-237

Author(s):

V. S. Arutyunov ◽

V. I. Savchenko ◽

I. V. Sedov ◽

A. V. Nikitin

Keyword(s):

Natural Gas ◽

Gas Phase ◽

World Economy ◽

Direct Methods ◽

Hydrocarbon Gases ◽

The World ◽

Phase Oxidation ◽

Gas Phase Oxidation ◽

Chemical Products ◽

Main Component

The paper considers the growing importance of gas chemistry for the world economy and the related necessity of developing new, particularly noncatalytic technologies for the conversion of natural gas and other hydrocarbon gases into chemical products. The available and promising noncatalytic processes of their conversion into syngas as well as the direct methods for the synthesis of chemical products from methane, which is the main component of natural gas, are discussed.

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Conformational polymorphism in a Schiff-base macrocyclic organic ligand: an experimental and theoretical study

Acta Crystallographica Section B Structural Science ◽

10.1107/s0108768110029514 ◽

2010 ◽

Vol 66 (5) ◽

pp. 527-543 ◽

Cited By ~ 11

Author(s):

Leonardo Lo Presti ◽

Raffaella Soave ◽

Mariangela Longhi ◽

Emanuele Ortoleva

Keyword(s):

Schiff Base ◽

Solid State ◽

Dft Calculations ◽

Gas Phase ◽

Phase Ii ◽

Density Functional ◽

Organic Ligand ◽

Stable Phase ◽

Stable Form ◽

Molecular Conformations

Polymorphism in the highly flexible organic Schiff-base macrocycle ligand 3,6,9,17,20,23-hexa-azapentacyclo(23.3.1.111,15.02,6.016,20)triaconta-1(29),9,11,13,15(30),23,25,27-octaene (DIEN, C24H30N6) has been studied by single-crystal X-ray diffraction and both solid-state and gas-phase density functional theory (DFT) calculations. In the literature, only solvated structures of the title compound are known. Two new polymorphs and a new solvated form of DIEN, all obtained from the same solvent with different crystallization conditions, are presented for the first time. They all have P\bar 1 symmetry, with the macrocycle positioned on inversion centres. The two unsolvated polymorphic forms differ in the number of molecules in the asymmetric unit Z′, density and cohesive energy. Theoretical results confirm that the most stable form is (II°), with Z′ = 1.5. Two distinct molecular conformations have been found, named `endo' or `exo' according to the orientation of the imine N atoms, which can be directed towards the interior or the exterior of the macrocycle. The endo arrangement is ubiquitous in the solid state and is shared by two independent molecules which constitute an invariant supramolecular synthon in all the known crystal forms of DIEN. It is also the most stable arrangement in the gas phase. The exo form, on the other hand, appears only in phase (II°), which contains both the conformers. Similarities and differences among the occurring packing motifs, as well as solvent effects, are discussed with the aid of Hirshfeld surface fingerprint plots and correlated to the results of the energy analysis. A possible interconversion path in the gas phase between the endo and the exo conformers has been found by DFT calculations; it consists of a two-step mechanism with activation energies of the order of 30–40 kJ mol−1. These findings have been related to the empirical evidence that the most stable phase (II°) is also the last appearing one, in accordance with Ostwald's rule.

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