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Liquid injection in fluidized beds occurs in well-established industrial processes as fluid coking, spray fluidzed bed granulation and condensed mode gas-phase polymerisation. These processes still suffer performance issues due to their complex nature, where liquid injection adds even more complexity.In this work, the effect of liquid injection on the temperature uniformity in a pseudo-2D fluidized bed was studied using Infra-Red Thermography. The Infra-Red images were also studied to qualify the agglomeration behaviour.Injecting smaller droplets (-90 lm affects the uniformity of the bed more than injecting larger droplets (-225 lm. However, the formation of agglomerates increases with increasing droplet size. The injection velocity influences the average temperature of the bed more for the larger droplets. Additionally, increased solids motion was observed to reduce the agglomeration formation in the bed. Lastly, the particle temperature distribution does not reflect the presence of agglomerates and is thus unsuitable to quantify the agglomeration behaviour.(c) 2022 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/).

ThermoCatalytic Decomposition of methane (TCD) offers an interesting route to convert natural gas into hydrogen and functional carbon. In this study the reaction kinetics of TCD is studied for a nickel supported catalyst using a special fluidized bed reactor. The effect of operating conditions such as temperature, concentrations of methane and hydrogen and space velocity (SV) was studied on a commercial nickel catalyst on a silica support. The performance of the catalyst was evaluated in terms of three parameters: maximum reaction rate, lifetime and carbon yield. Values up to and in excess of 70gC/gcat and 12h (at 550 °C and 70vol.% CH4-5vol.% H2) have been achieved for carbon yield and lifetime, respectively. The carbon product has fish bone structure. Our study has revealed that at lower temperatures and in the presence of small amounts of hydrogen () a higher carbon yield is obtained. Lower concentration of methane (higher concentration of the inert) lowers the reaction rate, the lifetime and therefore the carbon yield. A dual kinetic approach has been adopted to determine maximum reaction rate and the associated deactivation factor. The kinetic parameters were estimated for the temperature range of 550-600 °C.

Bubble columns are widely used in the chemical industry because of their simple design and high efficiency. The scale-up of these kinds of columns is challenging and time-consuming. Since high throughput is targeted, they are operated in the heterogeneous bubbling regime where the flow is complex and turbulent. Large-scale bubble columns can in principle be simulated using continuum models (TFM/MFM) with closures from more detailed models such as Front Tracking (FT) or Volume of Fluid (VOF). Multi-fluid models are capable of predicting the flow field, but to accurately describe mass transfer rates, an accurate interfacial area of the bubbles is required as well as mass transfer coefficients for dense bubble swarms. This requires the MFM to be coupled with models that can predict bubble size distributions. The Discrete Bubble Model (DBM) can be scaled up but the bubble-bubble interactions make it computationally very intensive. Stochastic Direct Simulation Monte Carlo (DSMC) methods treat the bubbles in a discrete manner while more efficiently handling the collisions compared to the DBM. The DSMC model has earlier been used for very small particles in the size range of Angstroms to microns where the particles are purely inertial at high Stokes numbers. In the work of Pawar et al. (2014) this was used for micrometer sized particles/droplets where this method proved to be 60 to 70 times faster than more classical methods like the Discrete Particle Model (DPM). In this work the DSMC method has been extended to finite sized bubbles/particles in the order of millimeters. A 4-way coupling (liquid-bubble-bubble) is achieved using the volume-averaged Navier Stokes equations. The model is verified first for monodisperse impinging particle streams without gas. Then the model is verified with the DBM of a 3D periodic bubble driven system. The collision frequencies are all within 10 percent accuracy and the speed up achieved per DEM time step is nearly 10 times compared to the DBM, which facilitates simulation of large systems.