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Complex fluid-rock interactions can occur during the injection of carbon dioxide (CO2) into saline aquifers for sequestration, which may affect CO2 injectivity and storage capacity. In this paper, a comprehensive reactive transport model is established to analyze salt precipitation, CO2-water-rock geochemical reactions, and their effects on reservoir physical properties and injectivity. In addition, sensitivity analyses are conducted to investigate the main factors that affect fluid-rock interactions and injectivity with relevance for site selection for CO2 storage. Results show that the back flow of formation water not only affects the salt precipitation but also affects the CO2-water-rock geochemical reactions, resulting in salt and calcite precipitations mainly occurring in the dry-out zone. However, most of the mineral dissolution/precipitation caused by CO2-water-rock reaction occurs in the two-phase and aqueous-phase zones, and their effect on reservoir porosity and permeability are small. A considerable amount of sodium chloride precipitates in the dry-out zone as brine is drawn by capillary action into this zone, with significant consequences for porosity, permeability and injectivity. The injection rate, salinity, capillary pressure–saturation relationships, and reservoir permeability strongly affect the distribution of salt precipitation. Moderate injection rates, salinities, capillary pressures, and permeabilities all lead to favorable CO2 injectivity.

International audience; One of the best low-cost approaches for capturing carbon dioxide from the combustion of solid fuels is chemical looping combustion (CLC) technology, where the processes of fuel oxidation and extraction of oxygen from the air are split in two separate reactors. In order to model the petroleum coke (petcoke) conversion in a CLC method, detailed knowledge about the reactions of pet-coke with O2, CO2, and H2O at temperatures between 750 and 1100 °C is required. Due to the lack of sufficient literature data, in this paper, the reactivity of these reactions is investigated in a custom-built test rig that enabled measurements of the mass loss of the fuel sample and the composition of the released gases. The Avrami, Random Pore, Shrinking Core, and Hybrid models were applied to the experimental results to determine the kinetic parameters of petcoke gasification. At temperatures up to 1000 °C, the reaction with CO2 was found to be negligibly slow. An activation energy of 103.91 kJ/mol was obtained for petcoke gasification in 10–40 vol% of H2O, while a value of 15.87 kJ/mol was found for oxidation in 2–4 vol% O2, as described by best-fitting models, i.e. Hybrid and Random Pore models, respectively.

Carbon dioxide ( C O 2 ) sequestration is considered to be one of the most effective technologies of mitigating greenhouse gas emissions. In this technology, single phase supercritical C O 2 is injected into an underground geological formation such as a deep saline aquifer. Existing sequestration projects demonstrate that successful implementations are possible; however, significant uncertainties associated with the risks of leakage remain an obstacle for broader use of this technology. The security of underground disposal could be considerably increased by dissolving the C O 2 in a brine produced from the aquifer, then re-injecting the mixture underground. The dissolution process occurs before the mixture reaches the aquifer; this significantly reduces or completely eliminates the risks of C O 2 leakage. This technique can drastically extend the amount of worldwide aquifers available for carbon sequestration. As was previously shown, complete dissolution could be achieved in a surface pipeline operating under the pressure of a target aquifer, where C O 2 is injected. In this paper, a comprehensive model of C O 2 droplet dissolution in a vertical injection well is presented. The model accounts for droplet breakup, coalescence, and dissolution processes as well as temperature and pressure variations over well depth. Feasibility and results are discussed and compared with surface dissolution options.

Carbon dioxide emissions from the chimneys of thermal power plants create major environmental risks. Therefore, an important step toward reducing the emissions in these power plants can be the carbon dioxide pre-combustion capture process. In this paper, a 150 MW thermal steam cycle power plant fueled by bagasse was studied. The power plant has an efficiency of 32.74%, and emits 246.52 t/h carbon dioxide. First, the design and simulation of a suggested pre-combustion carbon dioxide capture process was outperformed. In this process, the amount of carbon dioxide separation and capture using mono ethanol amine (MEA) 30 wt% as solvent is 90%. In this condition, the mass flow of bagasse was increased about 60% to keep the plant efficiency constant. At the same time, the energy loss as a result of the addition of the carbon dioxide recovery unit was around 11%. The process was optimized through Pinch Analysis to reduce energy waste and fuel flow. Moreover, it was indicated that power plant efficiency could be increased around 8% by integrating the hot exhaust gases from the gasification unit with power plant boiler using a heat recovery steam generation (HRSG) unit. With this modification, bagasse consumption was decreased by 23%.