Flue Gas Injection Research Articles

Synergistic Effect of O2 and H2S on the Corrosion Behavior of N80 Steel in a Simulated High-Pressure Flue Gas Injection System

The aim of this work was to understand the synergistic effect of O2 and H2S on the corrosion behavior of N80 steel in a simulated high-pressure flue gas injection system. Weight loss measurements show that the presence of O2 and an increase in temperature significantly accelerated the general corrosion rate of the N80 steel. We calculated a gray relational grade between different impact factors and the general corrosion rate from the results of an orthogonal experimental corrosion rate. The grade ranking of impact factors was: O2 concentration (0.817) > temperature (0.706) > total pressure (0.689) > H2S concentration (0.665) > CO2 concentration (0.517). Surface characterization of corrosion scales was done using scanning electron microscopy, energy-dispersive spectroscopy, x-ray powder diffraction, and 3D optical microscope analysis. The results show that in the O2-H2S-CO2-H2O coexistence system the products were composed mainly of FeCO3, FeS, Fe2O3, Fe3O4, and elemental sulfur. The results of the corrosion rate test and the characterization show that the presence of O2 greatly accelerated the corrosion process and changed the corrosion mechanism. Elemental sulfur, which was generated by the reaction between the H2S and the O2, participated in the corrosion process of the N80 steel. It could be considered that the synergistic effect of O2 and H2S accelerated the corrosion of the N80 steel. In addition, the porous structures of the corrosion scales and the severe local pits show that the high content of O2 inhibited the formation of FeCO3 and aggravated the corrosion of N80 steel.

Experimental investigation on precipitation damage during water alternating flue gas injection

Water Alternating Gas (WAG) approach can improve the efficiency of gas flooding. However, the precipitation damage that is induced by the gas injection may be inevitable. The precipitation pressure point test of gas injection, and the WAG parallel double-tube long-core flooding experiment under different injection conditions were systematically performed to obtain the optimum injection parameters. The variations of petrophysical properties were caused by precipitation, and its morphology was also determined by centrifugal capillary force and environmental scanning electron microscope. The precipitation pressure rised with the increase of the amount of gas injection, generally 2.0 MPa ~ 3.0 MPa higher than the bubble point pressure (Pb), and it was confirmed by X-ray energy spectrum and scanning electron microscope that the precipitation was mainly asphaltene. The optimum injection parameters for WAG were Gas–Water Ratio (GWR) of 1:1 and slug size of 0.1 HydroCarbon Pore Volume (HCPV), which benefited the recovery of low-permeability and high-permeability pipe by additional recovery of 28.5% and 17.4% respectively, while WAG process enhanced the total oil recovery by 23.4%. The pore volume and median radius of capillary pressure of all cores were both reduced with more obvious effects on conglomerate. Combined with the results of sediment saturation, it also showed the poorer the physical properties of the cores, the severer the influence of the precipitation. Overall, the WAG could greatly improve the recovery but the influence of precipitation must be considered.

Internal flow reconstruction strategies to improve both thermo-flow performance and flue gas diffusion characteristic of the integrated dry-cooling tower and stack system

The interaction between thermo-flow performance and flue gas injection in an integrated dry-cooling tower and stack system was revealed. Flue gas injection slightly increases the ventilation and heat rejection of the tower, and rear radiators are protected due to the blocking effect of the desulfurizer and stack. Both the swirl and downwind deflection of internal rising airflows contribute to the chaotic diffusion of flue gas. Two internal flow reconstruction strategies were proposed. One works in the stage of inflow air mixing, and the other works in the following stage of airflow rising. Numerical results show that the former strategy performs better on tower performance improvement, since the latter one causes a decline of tower ventilation at low wind speed. Both the two strategies have evident superiority in controlling gas diffusion inside the tower, especially at the medium wind speed of 10 m/s, the chaos of internal rising airflows reduces remarkably, and the contact area between flue gas and inner tower shell reduces over 85%. Thanks to the mitigation of plume downwash after flow reconstruction, diffusion passage of flue gas in the atmosphere is uplifted, and the reduction of contact area between flue gas and outer tower shell reaches 40%.

An Experimental Investigation on the Kinetics of Integrated Methane Recovery and CO2 Sequestration by Injection of Flue Gas into Permafrost Methane Hydrate Reservoirs

Large hydrate reservoirs in the Arctic regions could provide great potentials for recovery of methane and geological storage of CO2. In this study, injection of flue gas into permafrost gas hydrates reservoirs has been studied in order to evaluate its use in energy recovery and CO2 sequestration based on the premise that it could significantly lower costs relative to other technologies available today. We have carried out a series of real-time scale experiments under realistic conditions at temperatures between 261.2 and 284.2 K and at optimum pressures defined in our previous work, in order to characterize the kinetics of the process and evaluate efficiency. Results show that the kinetics of methane release from methane hydrate and CO2 extracted from flue gas strongly depend on hydrate reservoir temperatures. The experiment at 261.2 K yielded a capture of 81.9% CO2 present in the injected flue gas, and an increase in the CH4 concentration in the gas phase up to 60.7 mol%, 93.3 mol%, and 98.2 mol% at optimum pressures, after depressurizing the system to dissociate CH4 hydrate and after depressurizing the system to CO2 hydrate dissociation point, respectively. This is significantly better than the maximum efficiency reported in the literature for both CO2 sequestration and methane recovery using flue gas injection, demonstrating the economic feasibility of direct injection flue gas into hydrate reservoirs in permafrost for methane recovery and geological capture and storage of CO2. Finally, the thermal stability of stored CO2 was investigated by heating the system and it is concluded that presence of N2 in the injection gas provides another safety factor for the stored CO2 in case of temperature change.

The flue gas-solvent assisted steam assisted gravity drainage studies: experiments and numerical simulation in extra-heavy oil reservoirs

ABSTRACTSteam-assisted gravity drainage (SAGD) has been used successfully for developing extra-heavy oil around the world. But many experiments and field production have pointed out problems, such as heat loss to the overburden and low oil-steam ratio. Compared with SAGD, flue gas-solvent assisted SAGD (FGS-SAGD) is a relatively new thermal recovery technology. FGS-SAGD combines the multiple advantages of gas injection, solvent injection, and thermal recovery processes. In this paper, 3D sand pack models were established to study the steam chamber expansion characteristics and the development performance of different drainage experiments. Numerical models based on the experimental parameters were conducted to further study the gas and solvent migration and its effect on the temperature and oil saturation profiles. The results show that in the process of FGS-SAGD, the accumulation of flue gas effectively inhibited steam override and reduced heat loss to the overburden, which slowed the vertical expansion of steam chamber and improved the lateral expansion of steam chamber. Solvent was vaporized under high temperature and mixed with extra-heavy oil at the edge of steam chamber to reduce oil viscosity, which further improved the profile of steam chamber. Both flue gas and solvent injection significantly improved the heat utilization efficiency and increased the steam sweep volume and oil recovery. The oil recovery of FGS-SAGD (41.9%) was 12% higher than that of SAGD in the experiments. In addition, the oil mobility was increased by 26.2%, and water phase mobility was decreased by 19.7% in the process of FGS-SAGD. The study indicates that FGS-SAGD is a feasible technique for improving development performance in extra-heavy oil reservoirs.

Numerical investigation of flue gas injection enhanced underground coal seam gas drainage

AbstractCoal seam with low permeability is widely distributed in China. Injection of flue gas (N2:CO2 = 0.85:0.15) is an effective approach to improve coal seam gas drainage efficiency. This process relates complex responses among ternary gases (CH4, CO2, and N2) competitive sorption on coals, gas diffusion, gas‐water migration by means of two‐phase flow, and coal deformation. In this paper, an improved hydraulic‐mechanical model coupling above interactions is established for flue gas injection enhanced gas drainage. This model is used to simulate flue gas enhanced drainage by finite element method. The sensitivity analyses of key factors are made to recovery a better understanding on the processes controlling flue gas enhanced drainage. Results show that the flue gas enhanced drainage can indeed improve the efficiency of gas extraction and reduce the gas pressure to the required value in a shorter duration. Due to the competitive adsorption and gas sweeping effect of injected flue gas, CH4 is driven toward drainage borehole, and CH4 pressure and content near the injection borehole decrease faster than that near the drainage borehole. The peak CH4 pressure laterally moves from the injection borehole to the drainage borehole. Higher injection pressure, initial permeability, and smaller sorption affinity ratios may lead to greater CH4 production rate at early drainage stage, but smaller CH4 production rate at late stage. The factors controlling the behavior of flue gas enhanced drainage are initial permeability, injection pressure, and sorption affinity ratios in order. This work offers useful framework to investigate important technical challenges associated with enhanced mine gas drainage, as well as unconventional gas development.

CFD Simulation of Pollutant Emission in a Natural Draft Dry Cooling Tower with Flue Gas Injection: Comparison between LES and RANS

Accurate prediction of pollutant dispersion is vital to the energy industry. This study investigated the Computational Fluid Dynamics (CFD) simulation of pollutant emission in a natural draft dry cooling tower (NDDCT) with flue gas injection. In order to predict the diffusion and distribution characteristics of the pollutant more accurately, Large Eddy Simulation (LES) was applied to predict the flow field and pollutant concentration field and compared with Reynolds Average Navier-Stokes (RANS) and Unsteady Reynolds Average Navier-Stokes (URANS). The relationship between pollutant concentration pulsation and velocity pulsation is emphatically analyzed. The results show that the flow field and concentration field simulated by RANS and URANS are very close, and the maximum value of LES is about 43 times that of RANS and URANS for the prediction of pollutant concentration in the inner shell of cooling tower. Pollutant concentration is closely related to local flow field velocity. RANS and URANS differ greatly from LES in flow field prediction, especially at the outlet and downwind of cooling tower. Compared with URANS, LES can simulate flow field pulsation with a smaller scale and higher frequency.

Experimental study on the corrosion of a downhole string under flue gas injection conditions

AbstractFlue gas collection from steam generators and its utilization in enhanced oil recovery (EOR) can reduce CO2 emissions into the atmosphere and improve oil recovery efficiency. Under the environments of flue gas corrosion in oilfields, the effects of corrosion time, temperature, pressure, velocity, and concentrations of O2, SO2, H2O, and NaCl on corrosion rates of steels used for a downhole string were investigated through physical simulation experiments. The corrosion mechanisms were analyzed by component, and the morphology of the corrosion products tested by X‐ray diffraction (XRD) and scanning electron microscopy (SEM). In the gas phase, the corrosion rates of X70, P110, and N80 notably increase with temperature and O2 concentration. The corrosion rates first increase rapidly with pressure from 1.0 to 3.0 MPa and then remain largely stable. Meanwhile, the corrosion rates of X70, P110, and N80 in the liquid phase first increase and then decrease with temperature and reach maximum values at 90°C. The corrosion rates of X70, P110, and N80 increase notably with velocity and the concentrations of O2, SO2, H2O, and NaCl. The corrosion rate of 13Cr is considerably lower than those of N80, P110, and X70, which shows good corrosion resistance performance. To reduce the flue gas corrosion of a downhole string, the relative humidity of the flue gas should be lower than 0.7, the temperature of the flue gas in the wellbore should avoid the range between 80 and 100°C, the excess air coefficient of the boiler should be kept at a reasonable value to reduce the O2 content in the flue gas, and the flue gas should not be coinjected into wellbores with brine. The injection of flue gas is technically feasible considering the corrosion of downhole string.

Influence of turbulence boundary condition on pollutant diffusion for a natural draft cooling tower with flue gas injection

The influence of the specification of turbulence model in equilibrium atmosphere boundary layer (ABL) on the numerical simulation of pollutant diffusion for a natural draft cooling tower with flue gas injection is investigated. The ABL must be considered due to the immense size of cooling tower. The flow field and pollutant distribution under the circumstance of different turbulence boundary conditions are predicted by solving Navier-Stokes (N-S) equations based on shear-stress transport (SST) k-ω turbulence model. The results indicate that the pollutant distribution remains almost unchanged when the turbulence boundary condition changed, it can be inferred that the turbulence boundary condition has little effect on the diffusion of pollutant for other Reynolds Average Navier-Stokes (RANS) turbulence models. Since RANS cannot consider the fluctuation velocity, it is not very suitable for predicting the pollutant diffusion. To more accurately simulate the pollutant propagation and diffusion, the large eddy simulation (LES) model is needed.

Numerical simulation of the influence of flue gas discharge patterns on a natural draft wet cooling tower with flue gas injection

This paper introduces a distributed arrangement of flue gas emissions and presents conclusions on the optimal placement and quantity of flue gas vents in a certain horizontal plane of a natural draft wet cooling tower (NDWCT). An NDWCT set up based on the arrangement of flue gas vents established herein will raise efficiency with the increase of radial distance and flue gas vents. The authors found a way to inject flue gas at a certain angle, which can make the flue gas and humid air in the tower swirl upward, thereby increasing the pumping force of the cooling tower and further improving the cooling tower efficiency. When the incident angle is parallel to the generatrix of the hyperboloid cooling tower, the cooling tower efficiency is maximized. The flue gas flowrate effect on the cold-water temperature was also investigated based on determining the optimal value of the radial distance, quantity, and angle of the flue gas vent reach. Moreover, the formula that can be generalize the result to other NDWCTs is obtained to reach the optimal emission mode of flue gas. Comparing with the case before improved, the flow rate of NDWCT increases by 822.05 kg/s (18.9%), and the cold-water temperature decreases by 1.12 k, under a 200% flue gas flowrate.

An Enhanced Carbon Capture and Storage Process (e-CCS) Applied to Shallow Reservoirs Using Nanofluids Based on Nitrogen-Rich Carbon Nanospheres.

The implementation of carbon capture and storage process (CCS) has been unsuccessful to date, mainly due to the technical issues and high costs associated with two main stages: (1) CO2 separation from flue gas and (2) CO2 injection in deep geological deposits, more than 300 m, where CO2 is in supercritical conditions. This study proposes, for the first time, an enhanced CCS process (e-CCS), in which the stage of CO2 separation is removed and the flue gas is injected directly in shallow reservoirs located at less than 300 m, where the adsorptive phenomena control CO2 storage. Nitrogen-rich carbon nanospheres were used as modifying agents of the reservoir porous texture to improve both the CO2 adsorption capacity and selectivity. For this purpose, sandstone was impregnated with a nanofluid and CO2 adsorption was evaluated at different pressures (atmospheric pressure and from 3 × 10−3 MPa to 3.0 MPa) and temperatures (0, 25, and 50 °C). As a main result, a mass fraction of only 20% of nanomaterials increased both the surface area and the molecular interactions, so that the increase of adsorption capacity at shallow reservoir conditions (50 °C and 3.0 MPa) was more than 677 times (from 0.00125 to 0.9 mmol g−1).

Influence of Flue Gas Injection on the Long-Term Durability of a Natural Draft Concrete Cooling Tower.

The article undertakes the very important topic of the long-term durability of concrete in a natural draft concrete cooling tower with flue gas injection. The corrosive conditions, including temperature, relative humidity, and CO2 and SO2 gas concentrations, near the inner wall of a cooling tower with flue gas injection were monitored in real time to obtain the long-term durability performance of concrete. The pH and chemical compositions of the condensed liquid that adhered to the tower’s inner face and the macromorphology, compressive strength, and neutralization depth of in situ specimens were tested periodically. In addition, a finite element numerical simulation was conducted to simulate and verify the concentration distributions of CO2 and SO2 in the flue gas in the cooling tower. The results showed that the cleaned flue gas was enveloped, diluted, and uplifted by hot vapor in the cooling tower, and its concentration decreased. Meanwhile, the effective diffusion radius increased gradually as the flue gas rose. With the same elevation in the cooling tower, the concentration of flue gas decreased rapidly from the central point to the surrounding area. The air near the inner surface of the cooling tower was merely dampened air with a low concentration of acidic gas due to the gigantic diameter of the cooling tower. As a result, the injection of cleaned flue gas will not evidently increase the corrosion risk in a natural draft concrete cooling tower.

Exergy and economic analysis of using the flue gas injection system of a combined cycle power plant into the Heller Tower to improve the power plant performance

Natural Draft Dry Cooling system (Heller Tower) is regarded as one of the frequently used cooling systems in steam power plants. The performance of these towers depends heavily on environmental conditions. Under wind conditions, due to the lack of symmetry in pressure distribution around the tower and the formation of wind cover phenomena on the top of the tower, the inlet flow rate to the tower drops and accordingly, the heat rejected by Heller Tower reduces almost by 40%, leading to a reduction in the power and efficiency of cooling tower and entire power plant. The injection of flue gas dissipated by the recovery boiler, which has the temperature of about 130°C, into a cooling tower at the combined cycle power plant is regarded as one of the recent methods proposed to improve the cooling tower efficiency under wind conditions. The present study aimed to examine various dimensions of the effect of flue gas injection into the cooling tower of a combined cycle power plant on the entire power plant, as well as its efficiency in terms of exergy and economic analysis. For this purpose, a Heller Tower was modeled by the CFD method. In addition, the amount of the cooling tower heat was calculated by the results of numerical analysis and used for the thermo-exergy simulation of various components of a combined cycle power plant in states of with and without flue gas injection under the tower design and crosswind conditions. The results indicated that the power generated by the steam cycle increased by a maximum of 7.92 MW due to the flue gas injection and under wind conditions. Finally, the results of the economic analysis represented the return on investment rate of 81.18 and 91.17% for two states of permanent and economic use, respectively, and the payback period of about one year.

Effects of temperature on oxidation behaviours of 35CrMo in high temperature flue gas environment

The pipelines made by alloy 35CrMo are widely used in the process of flue gas injection. Therefore, corrosion behaviours of alloy 35CrMo have been investigated at varied temperatures, namely 120 °C, 150 °C, 200 °C and 250 °C, with same experimental pressure of 9 MPa and flus gas environment. Scanning electron microscopy was employed to examine the morphologies and microstructures of the oxide films. The results indicated that moderate temperature stands an essential role in the reaction mechanism and aggressive effects. In addition to increase in the diffusion rate of both alloy ions and corrosive gas, temperature can also reform the morphology of oxides by resulting in larger oxide particles and thicker oxide films, plus the transmission from needle-like oxides to spherical oxides.

Thermal performance improvement of the three aligned natural draft dry cooling towers by wind breaking walls and flue gas injection under different crosswind conditions

The substantial objective of using circulating cooling water in a typical power plant is to remove the heat effectively from the vapor cycle and to expel it to the environment. One of the most popular cooling systems for this purpose is the natural draft dry cooling tower (NDDCT) which is widely used in regions with the shortage of water, such as Iran. Environmental conditions affect the Heller cooling tower's performance strictly. Temperature, density, and the mass flow rate of sucked air into the cooling towers will all influence their operation. To improve the cooling tower's performance and air suction capability, it is proposed to inject the steam generators' flue gas into the tower. In this study, a single natural draft dry cooling tower incorporating the flue gas duct is modeled to study the effect of flue gas injection on the sucked air flow rate and the radiator heat transfer. Considering the buoyancy effect term, for a 3-D incompressible flow, the Navier Stokes' equations, as well as the energy equation, are solved by computational fluid dynamic method (CFD) to obtain the airflow pattern inside and outside the tower as well as the heat transfer from the radiators. The tower is assumed to be equipped with windbreak walls in one case and without it in another case so that the effect of crosswind could be investigated. Having compared the thermal performance of the towers, the results show that the thermal deficiency is more pronounced for the towers in crosswind without any flue gas injection. It is also shown that the injection of the hot flue gas (with temperature of 130 °C) will increase air intake and the thermal performance of the towers which, in turn, results in the reduction of the outlet water temperature. The modeling is then extended to three aligned NDDCTs to determine the effect of flue gas injection in the presence of windbreak walls under crosswind condition. Consequently, a notable promotion had been observed in all three towers thermal performance but with different ratios.

An optimization model for carbon capture utilization and storage supply chain: A case study in Northeastern China

In recent years, several strategies have been developed and adopted in a bid to diminish the carbon dioxide (CO2) released into the atmosphere. Carbon capture, utilization and storage (CCUS) system is one of the options. In this paper, we develop a CCUS supply chain superstructure by introducing more comprehensive transportation routes as well as the resultant system deployment schemes. A mixed integer linear programming (MILP) model is proposed to optimize the strategic CCUS deployment in Northeast China by making simultaneous selection of emission sources, capture facilitates, CO2 pipeline, intermediate transportation sites, utilization and storage sites. The CCUS cost includes the cost of flue gas dehydration, CO2 capture, transportation and injection, and revenue from CO2 utilization through enhanced oil recovery (CO2-EOR). The overall network is economically optimized over a 20 years’ life span to provide the geographic distribution and scale of capture, utilization and sequestration sites as well as the transportation routes for different scenarios. The results suggest that it is economic feasible to reduce 50% of the current CO2 emissions from the stationary sources at a total annual cost $2.30 billion accompanied with $0.77 billion of revenue generated annually through CO2-EOR. Overall, the optimal CCUS supply chain network correspond to a net cost of $23.53 per ton of CO2. The results are compared with source-sink model and it can be observed that the total annualized net cost is reduced from $1.62 billion to $1.53 billion and the transportation cost are reduced from $0.27 billion to $0.19 billion.

The Coupling Effect of O₂ and H₂S on the Corrosion of G20 Steel in a Simulating Environment of Flue Gas Injection in the Xinjiang Oil Field.

Flue gas injection for heavy oil recovery has received a great deal of attention, because it is more cost effective than lots of other injection methods. However, the corrosion could occur easily, because the flue gas usually contains corrosive gases such as CO2, H2S, and O2. In this work, the corrosion behaviors of G20 steel in flue gas injection environment simulating Xinjiang oil field (China) were investigated using weight loss measurement and surface characterization techniques. The effect of environments including the O2-containing environment, the H2S-containing environment, and the O2-H2S-coexisting environment on the corrosion of G20 steel in gas phase and liquid phase was discussed. The results show that the corrosion rate of G20 steel in the O2-H2S-coexisting environment is much higher than the sum of corrosion rates of the O2-containing environment and the H2S-containing environment, regardless of the gas phase and the liquid phase. This indicates that there is a coupling effect between O2 and H2S, which can further accelerate the corrosion of steel in O2-H2S-coexisting environment. The results of surface characterization demonstrate that in a typical flue gas injection environment, the corrosion products are composed of FeCO3, FeS, FeO(OH), and elemental sulfur. Elemental sulfur could obviously accelerate the corrosion of steel. Therefore, it can be considered that the coupling effect of O2 and H2S on corrosion of G20 steel in flue gas injection environment is caused by the formation of elemental sulfur in corrosion products.

Numerical Study on Smoke Plume for Natural Draft Cooling Tower with Flue Gas Injection

The new exhaust mode of natural draft cooling towers (NDCT) with flue gas injection is investigated. The three-dimensional model for NDCT with flue gas injection and the boundary conditions are established via the Gambit 2.3. The cross-section of drift eliminator is set the velocity entrance for thermo-hygro air (velocity-inlet). The flue entrance is set admission velocity (velocity-inlet), the exit of NDCT with flue gas injection is set free gas export (outflow), and the emission of net flue gas to the cooling tower is a source of buoyant jets. The N-S equations are solved with the standard k- turbulence model by the Fluent 6.3. The improved NDCT with flue gas injection avoids air disturbance low-pressure zone compared with the conventional NDCT with flue gas injection. The corrosion of NDCT with flue gas injection in throat is reduced because net flue gas is wrapped in thermo-hygro air. Temperature gradient of net flue gas was distinct, the high-temperature zone is concentrated, and the uplifting performance is improved.

The Experimental Analysis of the Role of Flue Gas Injection for Horizontal Well Steam Flooding

Heavy oil is an important hydrocarbon resource that plays a great role in petroleum supply for the world. Co-injection of steam and flue gas can be used to develop deep heavy oil reservoirs. In this paper, a series of gas dissolution experiments were implemented to analyze the properties variation of heavy oil. Then, sand-pack flooding experiments were carried out to optimize injection temperature and injection volume of this mixture. Finally, three-dimensional (3D) flooding experiments were completed to analyze the sweep efficiency and the oil recovery factor of flue gas + steam flooding. The role in enhanced oil recovery (EOR) mechanisms was summarized according to the experimental results. The results show that the dissolution of flue gas in heavy oil can largely reduce oil viscosity and its displacement efficiency is obviously higher than conventional steam injection. Flue gas gradually gathers at the top to displace remaining oil and to decrease heat loss of the reservoir top. The ultimate recovery is 49.49% that is 7.95% higher than steam flooding.

CO2 Capture by Injection of Flue Gas or CO2-N2 Mixtures into Hydrate Reservoirs: Dependence of CO2 Capture Efficiency on Gas Hydrate Reservoir Conditions.

Injection of flue gas or CO2-N2 mixtures into gas hydrate reservoirs has been considered as a promising option for geological storage of CO2. However, the thermodynamic process in which the CO2 present in flue gas or a CO2-N2 mixture is captured as hydrate has not been well understood. In this work, a series of experiments were conducted to investigate the dependence of CO2 capture efficiency on reservoir conditions. The CO2 capture efficiency was investigated at different injection pressures from 2.6 to 23.8 MPa and hydrate reservoir temperatures from 273.2 to 283.2 K in the presence of two different saturations of methane hydrate. The results showed that more than 60% of the CO2 in the flue gas was captured and stored as CO2 hydrate or CO2-mixed hydrates, while methane-rich gas was produced. The efficiency of CO2 capture depends on the reservoir conditions including temperature, pressure, and hydrate saturation. For a certain reservoir temperature, there is an optimum reservoir pressure at which the maximum amount of CO2 can be captured from the injected flue gas or CO2-N2 mixtures. This finding suggests that it is essential to control the injection pressure to enhance CO2 capture efficiency by flue gas or CO2-N2 mixtures injection.