The Michelsen stability and multiphase flash calculation by direct minimization of Gibbs free energy of the system at constant temperature and pressure, was used for systems containing gas hydrates. The solid hydrate phase was treated as a solid solution. The fugacities of all components of the hydrate phase were calculated as a function of compositions by the rearranged model of van der Wa...

Clathrate hydrates are crystalline compounds formed by a physically stable interaction between water and relatively small guest molecules. Under suitable conditions of guest pressure and temperature, water molecules, via hydrogen bonds, form into polyhedral cavities that connect to give space-filling frameworks. Because of partial cage filling, these crystalline compounds are nonstoichiometric....

We present an experimental study on the formation and dissociation characteristics of carbon dioxide (CO2) gas hydrates using Raman spectroscopy. The CO2 hydrates were formed from sodium chloride/water solutions with salinities of 0-10 wt %, which were pressurized with liquid CO2 in a stirred vessel at 6 MPa and a subcooling of 9.5 K. The formation of the CO2 hydrate resulted in a hydrate gel w...

Replacement of methane with carbon dioxide in hydrate has been proposed as a strategy for geologic sequestration of carbon dioxide (CO(2)) and/or production of methane (CH(4)) from natural hydrate deposits. This replacement strategy requires a better understanding of the thermodynamic characteristics of binary mixtures of CH(4) and CO(2) hydrate (CH(4)-CO(2) mixed hydrates), as well as thermoph...

One of the main problems in oil recovery via the gas injection is the formation of hydrates in thelines. In order to prevent the formation of hydrate in these lines, which leads to the blockage andsometimes explosion, at first, the equilibrium formation conditions must be determined and then toprevent its formation by changing the thermodynamic conditions or by adding the inhibitors. In thisres...

A two-dimensional pore-network model based on invasion percolation is used to study the patterns obtained from the release of methane during the dissociation of methane hydrates (without including dissociation kinetics) caused by a sudden pressure reduction in the system below the hydrate equilibrium pressure. The concept of the critical gas saturation S(gc) (volume fraction of the gas phase at...

varieties of st. john’s wort (hypericum perforatum l.) native to iran possess the largest percentage of hypercin in their leaves and flowers. isotherm curves show the relationship between the relative humidity and moisture content of the plant at a constant temperature. it is essential to understand the isotherms curves for successful storage and drying of the plant. this study used adsorption ...

Gas hydrates are crystalline solids formed from mixtures of water and low molecular weight compounds, referred to as hydrate formers, that typically are gases at ambient conditions (1). Generally, hydrates are formed in the laboratory from two-phase systems by contacting a hydrate former or formers in the gas or liquid phase with liquid water and increasing the pressure until crystalline hydrat...

Though ammonium bisulfate is one of the most common of atmospheric hygroscopic aerosols, knowledge of its interaction with water has, until now, been extremely limited. This paper presents our observations on single isolated ammonium bisulfate aerosol particles, as they interact with water vapor at temperatures ranging from -40 to 30 °C. The complete phase diagram in the temperature/composition...