CO2 Phase Change Research Articles

Experimental study on the dynamic filtration control performance of N2/liquid CO2 foam in porous media

Liquid CO2 has been successfully used as a fracturing fluid and injected into rock formations to enhance oil and gas production. However, the difficulty in controlling the filtration of liquid CO2 in porous media limits its application. The goal of this study is to investigate the dynamic filtration control performance of N2/liquid CO2 foam with a fluorochemical (HFE) as stabilizer. A laboratory apparatus has been specially designed and built for the generation of N2/liquid CO2 foams and the measurement of their viscosity and filtration rate under high pressure (10–25MPa). The test results show that after liquid CO2 and HFE were mixed with N2, the N2/liquid CO2 foams were generated and showed significant viscosity improvement compared to liquid CO2. The foams exhibited better filtration control performance compared to liquid CO2 and liquid CO2+N2 systems. Although the addition of HFE did not result in the formation of filter cake, the foam showed a wall-building behavior, which could be explained by the CO2 phase change in porous media. As foam quality increased from 28% to 92%, the leakoff coefficient and spurt loss volume first decreased until the foam became unstable and changed into mist flow. The leakoff coefficient of foam increased with the increase in permeability of porous media. For foam with the quality of about 50–80%, a change of 2 orders of magnitude in permeability resulted in a change of 1 order of magnitude in leakoff coefficient. At high pressure difference, lower initial quality foam (∼30%) showed better filtration performance than higher initial quality foam (∼80%). When the pressure difference was high enough to cause the CO2 phase change from liquid to gas in the porous media, the initial foam damage after filtration became obvious, but the damage could be eliminated with time by gas return flow. Thus, by using N2/liquid CO2 foam in porous media, the fluid filtration behavior could be controlled without damage.

A Novel CO2 Phase Change Absorbent: MEA/1-Propanol/H2O

Due to the high energy consumption in CO2 capture by amine absorbents, CO2 phase change absorbent, CPCA, has attracted a great attention in research institutes recently. Two phases are formed after CO2 absorption with CPCA as the absorbent, and only the CO2-rich phase goes to the stripper, which could potentially reduce the energy consumption. In this work, the CPCAs composed of MEA/1-propanol/H2O were developed based on the principles of aqueous two-phase systems. The effects of temperature, amine concentration, and total CO2 loading on the phase separation of CPCAs were studied. CO2 loading and 1-propanol distributions in two phases under different experimental conditions were measured. The results indicated that the total CO2 loading is the key factor affecting the distribution of components in two phases. Moreover, in comparison to traditional 30 wt % MEA, the initial absorption rates of all CPCAs were higher than that of MEA, and its maximum value was 5 times higher. The cyclic capacity of the CPCA w...

Development of MEA-based CO2 phase change absorbent

By using the salting-out phenomenon to induce phase separation, the novel CO2 phase change absorbents (CPCAs) composed of MEA/water-miscible alcohol/H2O were developed. The absorbents using 1-propanol, 2-propanol and tertiary butanol as the diluent were selected as CPCAs. The CPCAs composed of MEA/1-propanol/H2O were further examined include the species distributions in the two phases, physical properties, cyclic capacity and absorbent regenerability. In comparison to 30wt% MEA/H2O, the optimal CO2 cycle capacity of CPCA is 2.59mol CO2/kg which increase 62% and the volume of CPCA sent to the stripper decreased over 67%. The developed CPCAs would benefit to reduce energy consumption of CO2 capture.

Simulations of long‐column flow experiments related to geologic carbon sequestration: effects of outer wall boundary condition on upward flow and formation of liquid CO2

AbstractImproving understanding of CO2 migration, phase change, and trapping processes motivates the development of large‐scale laboratory experiments to bridge the gap between bench‐scale experiments and field‐scale studies. Critical to the design of such experiments are defensible configurations that mimic relevant subsurface flow scenarios. We use numerical simulation with TOUGH2/ECO2M and ECO2N to design flow and transport experiments aimed at understanding upward flows including the transition of CO2 from supercritical to liquid and gaseous forms. These experiments are designed for a large‐scale facility such as the proposed laboratory for underground CO2 investigations (LUCI). LUCI would consist of one or more long‐column pressure vessels (LCPVs) several hundred meters in length filled with porous materials. An LCPV with an insulated outer wall corresponds to the column being at the center of a large upwelling plume. If the outer wall of the LCPV is assigned fixed temperature boundary conditions corresponding to the geothermal gradient, the LCPV represents a narrow upwelling through a fault or well. Numerical simulations of upward flow in the columns reveal complex temporal variations of temperature and saturation, including the appearance of liquid CO2 due to expansion cooling. The results are sensitive to outer thermal boundary conditions. Understanding of the simulations is aided by time‐series animations of saturation‐depth profiles and trajectories through P‐T (pressure‐temperature) space with superimposed phase saturations. The strong dependence of flow on hydrologic properties and the lack of knowledge of three‐phase relative permeability and hysteresis underlines the need for large‐scale flow experiments to understand multiphase leakage behavior. © 2012 Society of Chemical Industry and John Wiley & Sons, Ltd