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Pressurized chemical looping combustion (PCLC) provides the benefit of simplifying the carbon capture process by generating a flue gas stream with high CO2 concentration. However, flue gas polishing is required to remove the residual impurities for pipeline transport. The intensified heat exchanger reactor (IHXR) is a promising method for flue gas polishing while maximizing useful heat recovery that incorporates alternating catalytic packed beds with interstage cooling via printed circuit heat exchangers (PCHE). This work offers a design process for an IHXR capable of polishing a flue gas stream from a 100 MWth natural gas-fired PCLC unit while recovering 1.6 MW of useful heat in the form of saturated steam at 180 °C. Simulation work performed in Aspen HYSYS was used to determine the polished flue gas outlet species concentrations as well as the required number and size of the packed bed sections. The PCHEs for interstage cooling were sized via a thermal circuit approach. The final IHXR consists of six packed beds at 0.06 m in length and five PCHEs at 0.265 m in length, combining to a total IHXR length of 1.685 m. The height and width of the IHXR is shared between the packed beds and PCHEs at 0.91 m and 0.45 m, respectively. The resulting IHXR is capable of recovering heat at a rate of approximately 2.3 MW/m3.

The concentration of residual O2 in oxy-fuel combustion flue gas needs to be reduced before CO2 transportation, utilization, or storage. An original application of the printed circuit heat exchanger (PCHE) for catalytic combustion with natural gas (catalytic deoxygenation) is described for reducing the residual O2 concentration. The PCHE design features multiple adiabatic packed beds with interstage cooling and fuel injection, allowing precise control over the reaction extent and temperature within each reaction stage through the manipulation of fuel and utility flow rates. This work describes the design of a PCHE for methane–oxygen catalytic combustion where the catalyst loading is minimized while reducing the O2 concentration from 3 vol% to 100 ppmv, considering a maximum adiabatic temperature rise of 50 °C per stage. Each PCHE design differs by the number of reaction stages and its individual bed lengths. As part of the design process, a one-dimensional transient reduced-order reactor model (1D ROM) was developed and compared to temperature and species concentration axial profiles from 3D CFD simulations. The final design consists of five reaction stages and four heat exchanger sections, providing a PCHE length of 1.09 m at a processing rate of 12.3 kg/s flue gas per m3 PCHE.

This work investigates the impact of fluid (CO2(g), water) flow rates, channel geometry, and the presence of a surfactant (ethanol) on the resulting gas–liquid flow regime (bubble, slug, annular), pressure drop, and interphase mass transfer coefficient (kla) in the FlowPlateTM LL (liquid-liquid) microreactor, which was originally designed for immiscible liquid systems. The flow regime map generated by the complex mixer geometry is compared to that obtained in straight channels of a similar characteristic length, while the pressure drop is fitted to the separated flows model of Lockhart–Martinelli, and the kla in the bubble flow regime is fitted to a power dissipation model based on isotropic turbulent bubble breakup. The LL-Rhombus configuration yielded higher kla values for an equivalent pressure drop when compared to the LL-Triangle geometry. The Lockhart–Martinelli model provided good pressure drop predictions for the entire range of experimental data (AARE < 8.1%), but the fitting parameters are dependent on the mixing unit geometry and fluid phase properties. The correlation of kla with the energy dissipation rate provided a good fit for the experimental data in the bubble flow regime (AARE < 13.9%). The presented experimental data and correlations further characterize LL microreactors, which are part of a toolbox for fine chemical synthesis involving immiscible fluids for applications involving reactive gas–liquid flows.

Fire whirls can occur during urban fires, especially in intense fires in combustible building structures, and more often in forest or wildland fires. They are a special swirling diffusion flame characterized by significant enhancement in burning rates, flame heights and flame temperatures, along with a strong whirling motion of the flame. This whirling motion can pick up large firebrands and scatter them afar leading to spot fires. Many researchers have published experimental work on small- and medium-scale pool fire whirls and gaseous fuel fire whirls using split cylinders and various fixed-frame apparatus to investigate axial and tangential velocity profiles, axial and radial temperature distribution, burning rates, and flame heights. Likewise, several researchers have attempted to predict the experimental results of fire whirls using different modelling approaches and simulation software. In this paper, experiments were undertaken to study the dynamics of propane gas fire whirls in a small-scale, square-based, fixed-frame apparatus. Measurements of flame height and temperature profiles (both axial centerline and radial) were made for a low initial momentum burner of 76.2 mm internal diameter. The burner was operated at a volumetric flow rate of 6 dm3/min, which gave a heat release rate of 9.12 kW. Simulations using Fire Dynamics Simulator (FDS 6.6.0) and ANSYS Fluent 17.1 were performed to compare with the experimental measurements. Four separate mesh refinements were employed and four different sub-grid-scale (SGS) turbulence models were tested with FDS. The Deardorff, Wall-Adapting Local Eddy-viscosity (WALE), and dynamic Smagorinsky models, formed stable fire whirls for the two largest mesh refinements. The temperature profiles were overpredicted at the core of the flame with FDS and underpredicted with Fluent. The FDS simulation prematurely predicts the peak temperature for the axial centreline profile, whereas with Fluent the axial temperature profile matches the general trend of the experimental measurements. The visible flame height, determined through image processing, was approximately 0.88 ± 0.06 m, which corresponds to a measured temperature of ∼500°C. The 500°C temperature contour was used as a rough approximation of the flame height in the numerical simulations. It was found that with Fluent the 500°C contour grew until the fire whirl stabilized and reached the top of the hood at 1.6 m, clearly overpredicting the flame height. The height estimates based on the predicted 500°C contours show a strong dependence on the mesh resolution. This is primarily due to increased instability resulting in more mixing and spreading of the temperature for the coarser mesh size. However, the simulated flame heights show less dependence on the SGS turbulence models.