Influence of Direct Current–Voltage Accompanied by Charge Flow on CO2 Hydrate Formation

The capture and storage of carbon dioxide (CO2) are urgent and crucial to achieve the goal of carbon neutrality. Hydrate-based CO2 capture technology is one of the promising technologies for capturing and storing CO2. This work studied the nucleation and growth of CO2 hydrate provoked by direct current–voltage accompanied by charge flow with the agitation of 450 rpm at an initial pressure of 3.5 MPa and a temperature of 274.15 K. The results show that the physical bubble behavior and electrochemistry mechanisms could influence CO2 hydrate formation process in the application of voltage. The induction time and semi-completion time of CO2 hydrate formation were decreased by 51% and 27.8% in the presence of 15 V, respectively. However, more product of electrolysis, Joule heat and ions, could inhibit the CO2 hydrate formation process in the application of a high voltage (60 V). In addition, a high voltage (60 V) could change the morphology characteristics of CO2 hydrate from gel-like to whisker-like. This study provides valuable information on the formation of CO2 hydrate under the action of charge flow.

Dynamics of shock waves in bubble zones of finite size with a hydrate-forming gas

The purpose of this study is to study the dynamics of the wave field, which is realized in a channel with a liquid containing a rectangular zone with bubbles of the freon-12 hydrate-forming gas during the propagation of a pressure shock wave. In the initial state, the considered gas-liquid system is under pressure P0. After a sudden increase in pressure to the value of Pe, a pressure wave of a stepped profile propagates in the system and, as a result of the presence of a bubble curtain, its amplitude increases, which in turn has a more favorable effect on the formation of hydrate in gas bubbles. In the initial state, the hydrate formation process was not taken into account. As a result, the dynamics of the pressure wave is shown during its propagation in a semi-infinite channel containing a gas curtain with a hydrate-forming gas. The mechanism of gas hydrate formation is described in this work on the basis of the theory of nonequilibrium phase transitions in vapor-liquid systems.

A Brief Overview of Lab - Scale Apparatuses Used in the Recent Years for Experimental Investigations on Gas Hydrates

Gas hydrates are nonstoichiometric solid crystalline compound, whose formation is function of several parameters, such as pressure, temperature, fluid phase composition, reservoir saturation degree and others. One of the most critical aspects related to the research on this manner stays in differences existing between experimental results reached by using different experimental apparatuses. Moreover, laboratory scale reactors often have very contained dimensions with a consequent increasing influence of the boundary conditions. In the present paper, a brief overview of reactors used worldwide for experimental research on gas hydrates formation, is provided. In particular, the surface/volume ratio was calculated for each different typology of reactor and then associated with the ratio between moles of guest compound entrapped into water cages and moles injected. Even if such ratio does not represent the process efficiency, it is proportional to it. Consequently, that comparison was useful to well define the supporting effect of a greater S/V ratio on the hydrate formation process efficiency.

Study on microscopic growth mechanism of emulsion system hydrate

In order to master the microscopic growth mechanism of natural gas hydrate, a series of experiments were carried out using a high-pressure hydrate flow loop. The microscopic physical information of the growth of hydrates in the emulsion system is captured by advanced microscopic equipment and the phenomena of the experiments show that: 1) not all water droplets instantaneously generate a hydrate shell, but only a few of the water droplets gradually generate a hydrate shell when reaching the conditions of the hydrate formation; and 2) the coalescence and shear do occur in the hydrate formation process, and the distribution of hydrate particle size has changed.

Geomechanical effects of carbon sequestration as CO2 hydrates and CO2-N2 hydrates on host submarine sediments

Over the past 10 years, more than 300 trillion kg of carbon dioxide (CO2) have been emitted into the atmosphere, deemed responsible for climate change. The capture and storage of CO2 has been therefore attracting research interests globally. CO2 injection in submarine sediments can provide a way of CO2 sequestration as solid hydrates in sediments by reacting with pore water. However, CO2 hydrate formation may occur relatively fast, resulting decreasing CO2 injectivity. In response, nitrogen (N2) addition has been suggested to prevent potential blockage through slower CO2-N2 hydrate formation process. Although there have been studies to explore this technique in methane hydrate recovery, little attention is paid to CO2 storage efficiency and geomechanical responses of host marine sediments. To better understand carbon sequestration efficiency via hydrate formation and related sediment geomechanical behaviour, this study presents numerical simulations for single well injection of pure CO2 and CO2-N2 mixture into submarine sediments. The results show that CO2-N2 mixture injection improves the efficiency of CO2 storage while maintaining relatively small deformation, which highlights the importance of injectivity and hydrate formation rate for CO2 storage as solid hydrates in submarine sediments.

STUDY OF THE HYDRATE FORMATION IN A PIPELINE WITH INSULATION COATING DURING GAS TRANSFER FROM THE “DOME-SEPARATOR”

The paper proposes a mathematical model describing the process of the hydrate formation in a vertical pipeline through which the gas is transported from the dome-separator designed to eliminate a technogenic spill of oil from the well at the seabed. If the dome is located in the zone of stable hydrate existence, then hydrate deposits can form within and in the pipeline, which can lead to the pipeline clogging. The influence of the presence of a pipeline insulation coating, which consists of the layers of polyurethane and polyurethane foam, and its thickness on the hydrate formation process in a steel pipeline is studied on the basis of numerical modeling. It is shown that if the gas is derived from the dome located at a depth of 1500 m, the zone of hydrate deposits is formed at the inlet of the pipeline without insulation (in the dome-separator vicinity). When the thermal insulation of the pipeline is used, it leads to an upward shift of the hydrate formation conditions. As a result, depending on the thickness of the insulation coating, the zone of hydrate deposits is formed near the outlet of the pipeline (in the ocean surface vicinity) or no hydrates are formed in the pipe. It is also shown that the motion of the seawater around the pipeline has almost no effect on the process of hydrate formation within the pipe.