V.A. Istomin

Combined CFD/Population Balance Model for Gas Hydrate Particle Size Prediction in Turbulent Pipeline Flow

A combined computational fluid dynamics/population balance model (CFD‐PBM) is developed for gas hydrate particle size prediction in turbulent pipeline flow. The model is based on a one‐moment population balance technique, which is coupled with flow field parameters computed using commercial CFD software. The model is calibrated with a five‐moment, off‐line population balance model and validated with experimental data produced in a low‐pressure multiphase flow loop.

EXPERIMENTAL METHOD FOR DETERMINATION OF THE RESIDUAL EQUILIBRIUM WATER CONTENT IN HYDRATE-SATURATED NATURAL SEDIMENTS

The equilibrium “pore water in sediment–gas hydrate-former–bulk gas hydrate” was experimentally studied. This residual pore water corresponds to a minimal possible amount of water in the sediment, which is in thermodynamic equilibrium with both gas and the bulk hydrate phase. This pore water can be defined as non-clathrated water by analogy to unfrozen water widely used in geocryological science. The amount of non-clathrated water depends on pressure, temperature, type of sediment, and gas hydrate former. The presence of residual pore water influences the thermodynamic properties of hydrate-saturated samples. The paper’s purpose is to describe a new experimental method for determining the amount of non-clathrated water in sediments at different pressure/temperature conditions. This method is based on measuring the equilibrium water content in an initially air-dried sediment plate that has been placed in close contact with an ice plate under isothermal, hydrate-forming gas pressure conditions. This method was used to measure the non-clathrated water content in kaolinite clay in equilibrium with methane hydrate and CO2 hydrate at a temperature of –7.5 o C in a range of gas pressures from 0.1 to 8.7 MPa for methane and from 0.1 to 2.5 MPa for CO2. Experimental data show that at the fixed temperature the non-clathrated water in hydrate-containing sediments sharply reduces when gas pressure increases. The experiment demonstrates that the non-clathrated water content strongly depends on temperature, the mineral structure of sediment, and the hydrate-forming gas.

A novel method for CO2 storage and methane recovery in gas hydrate reservoirs through injection of flue gas from coal-fired power plants

The geological Storage of CO2 together with the recovery of methane gas from methane hydrate reservoirs in permafrost and sub-marine areas is promised a strategy towards overcoming climate change and energy supply. The major challenge in carbon capture and storage (CCS) is the difficulty in removing and capturing CO2 from other components of air mainly nitrogen, covering the main cost in CCS. In this study, a novel economical technique, without CO2 capture process, based on direct injection of flue gas from coal-fired power plants (14 mol% CO2, and 86 mol% N2) into gas hydrate reservoirs was investigated at bulk conditions. Experiments were conducted at different typical hydrate reservoir temperatures (278.2 K, and 283.2 K) and different ratio of flue gas to initiated methane hydrate. The efficiency of both CO2 storage and methane recovery were investigated by measuring the gas composition change during step-wise depressurization of system using gas chromatography. Methane recovery was induced by flue gas injection, shifting the methane hydrate phase boundary due to driving force of changed Vapour phase composition. In addition, injected CO2 was sequestrated as different types of hydrate. Finally, it’s concluded that CO2 storage efficiency is dependent on thermodynamic condition of the experiment.