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Abstract The use of water production as a pressure mitigation tool in the context of CO2 storage is widely studied but the impact it might have on the migration behaviour of a buoyant CO2 plume is less well reported. To investigate this further two different scenarios were modelled. In the first, a single water production well was used to draw CO2 along the strike of an open aquifer with a regional dip. Large rates of water production (5–10 times the volume of injected CO2) were required to achieve only small displacements of the CO2 plume. The second scenario investigated to what extent an induced hydraulic gradient might spill CO2 already stored in a structural trap. Here the effects were more pronounced with over 90% of the CO2 being spilled at a water cycling rate of 10 Mt per year (corresponding to a hydraulic gradient of 1.28 bar/km). The modelling was tested by the real case at Sleipner where CO2 migration in the Utsira Sand is potentially impacted by water production at the nearby Volve field. Simulations concluded that the CO2 plume at Sleipner should not be materially affected by water production from Volve and this is supported by the time-lapse seismics.

The transportation impact on pollution and global climate change, has forced the automotive sector to search for more ecological solutions. Owing to the different properties of Fuel Cell (FC), real potential for reducing vehicles’ emissions has been witnessed. The optimization of FC integration within Electric Vehicles (EVs) is one of the original solutions. This paper presents an innovating solution of multi-stack Fuel Cell Electrical Vehicle (FCEV) in terms of efficiency, durability and ecological impact on environment. The main objective is to illustrate the interest of using the multi-stack FC system on the global autonomy, cycling, and efficiency enhancement, besides optimizing its operation performance.

Swirl combustors have proven as effective flame stabilisers over a wide range of operation conditions thanks to the formation of well-known swirl coherent structures. However, employment of swirl combustors to work on lean premixed combustion modes while introducing alternative fuels such as high hydrogen blends result in many combustion instabilities. Under these conditions, flame flashback has been considered as one of the major instability problems that have the potential of causing considerable damages of the combustion systems hardware in addition to the significant increase in pollutant levels. Combustion Induced Vortex Breakdown (CIVB) is considered a very particular mode of flashback mechanism in swirling flows as this type of flashback occurs even when the fresh mixture’s velocity is higher than the flame speed, consequence of the interaction between swirl structures and swirl burner geometries. Improvements of burner geometries and manipulation of swirl flows can produce good resistance against this type of flashback. However, increase flame flashback resistance against CIVB can lead to an increase in the propensity of another flashback mechanism, Boundary Layer Flashback (BLF). Thus this paper presents an experimental and numerical approach that allows the increase in CIVB resistance by using diffusive air injection and simultaneously avoid BLF by changing the wall boundary layer characteristics using microsurface grids as a liner for the nozzle wall. Results show that using those two techniques together has promising potentials regarding wider stable operation for swirl combustors, enabling them to burn a great variety of fuel blends safely.

Environmental concern for our planet has changed significantly over time due to climate change, caused by an increasing population and the subsequent demand for electricity, and thus increased power generation. Considering that natural gas is regarded as a promising fuel for such a purpose, the need to integrate carbon capture technologies in such plants is becoming a necessity, if gas power plants are to be aligned with the reduction of CO2 in the atmosphere, through understanding the capturing efficacy of different absorbents under different operating conditions. Therefore, this study provided for the first time the comparison of available absorbents in relation to amine solvents (MEA, DEA, and DEA) CO2 removal efficiency, cost, and recirculation rate to achieve Climate change action through caron capture without causing absorbent disintegration. The study analyzed Flue under different amine-based solvent solutions (monoethanolamine (MEA), diethanolamine (DEA), and methyldiethanolamine (MDEA)), in order to compare their potential for CO2 reduction under different operating conditions and costs. This was simulated using ProMax 5.0 software modeled as a simple absorber tower to absorb CO2 from flue gas. Furthermore, MEA, DEA, and MDEA adsorbents were used with a temperature of 38 °C and their concentration varied from 10 to 15%. Circulation rates of 200–300 m3/h were used for each concentration and solvent. The findings deduced that MEA is a promising solvent compared to DEA and MDEA in terms of the highest CO2 captured; however, it is limited at the top outlet for clean flue gas, which contained 3.6295% of CO2 and less than half a percent of DEA and MDEA, but this can be addressed either by increasing the concentration to 15% or increasing the MEA circulation rate to 300 m3/h.

AbstractAn Artificial Neural Network surrogate modelling approach was used to optimise CO2 storage into a highly heterogeneous semi- closed saline aquifer which exhibits considerable pressure increase due to injection. The methodology was implemented to minimise the overall field pressure and well bottom-hole pressures, and to maximise the amount of dissolved and trapped CO2 in the storage aquifer. Different realisations of permeability and porosity were stochastically generated to represent the uncertainty in the model. Artificial neural networks were used to reduce the computational time of the optimisation procedure by approximating the objective functions for CO2 storage as surrogates to the expensive solutions of flow by the simulator. A multi- objective evolutionary algorithm was run on these approximators to generate solutions of the multi-objective optimisation's Pareto front. These solutions were compared with the solutions obtained by the computationally expensive optimisation and they were found to give satisfactory results, illustrating that this methodology can be a viable, and low computational cost alternative for optimisation in CO2 storage design.

Abstract An analysis of the integration of a Ca-looping process into a cement plant is presented. The capture process, based on selective absorption of CO2 by calcium oxide, has two interconnected reactors where the carbonator captures CO2 from the preheater flue gases and the calciner regenerates the CaCO3 into CaO by oxy-combustion. The study also considers the purge rate of part of the circulating CaO, given the tendency of the material to sinter and reduce its capture capacity. Fresh CaCO3 is added to maintain reactivity in the carbonator, while the purged sorbents are utilised as a cement kiln feed. The detailed carbonator model has been implemented using Matlab and incorporated into Unisim to provide a full flowsheet simulation for an exemplary dry-feed cement plant as a user-defined operation. The effect of molar flowrate ratio of lime make-up to feed CO2 ( F 0 / F CO 2 ) between two operational limits has been investigated. This process configuration is capable of achieving over 90% CO2 capture with additional fuel consumption of 2.5–3.0 GJth/ton CO2 avoided which depends on the F 0 / F CO 2 ratio. It is found that a proper heat recovery system supplementary to the Ca-looping process makes the Ca-looping process more competitive than the traditional low temperature absorption process based on amine solvents.

In a domestic central heating system, the phenomenon of microbubble nucleation and detachment on the surface of a boiler heat exchanger finds its origins in the high surface temperature of the wall and consequential localised super saturation conditions. If the surrounding bulk fluid is at under-saturated conditions, then after exiting the boiler, the occurrence is followed by bubbly flow and bubble dissolution. A comprehensive understanding of the fundamentals of bubble dissolution in such a domestic wet central heating system is essential for an enhanced deaeration technique that would consequently improve system performance. In this paper, the bubble dissolution rate along a horizontal pipe was investigated experimentally at different operating conditions in a purpose built test rig of a standard domestic central heating system. A high speed camera was used to measure the bubble size at different depths of focal plane using two square sectioned sight glasses at two stations, spaced 2.2 m apart. A dynamic model for bubble dissolution in horizontal bubbly flow has been developed and compared with experimental data. The effects of several important operating and structural parameters such as saturation ratio, velocity, temperature, pressure of the bulk liquid flow, initial bubble size and pipe inside diameter on the bubble dissolution were thus examined using the model. This model provides a useful tool for understanding bubble behaviours in central heating systems and optimising the system efficiency.

202310 bcvc ; Version of Record ; RGC ; Others ; Imperial College London; European Research Council; National Natural Science Foundation of China ; Published