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The performance of the Trickle Bed Reactor (TBR) critically depends on the gas-liquid flow distribution in the reactor, which in turn depends on the catalyst shape, size, and structure. Extensive research has been carried out with spherical particles (catalyst),whereas industrially more complex-shaped particles (Cylindrical, Trilobe, and Quadrilobe) are used. Little work has been reported for the liquid distribution in packed beds employing these shapes.In this work, the liquid distribution was investigated in a cylindrical column of internal diameter 100 mm, containing particles of diameter 1.3 mm trilobed extrusions and length 1.8–8.8 mm. The influence of different loading methods - Central single source, solid cone, and hollow cone, gas and liquid flow rates, variation along the height of the column were studied. Air-water system was used. Pressure drop was measured with the help of a manometer and Maldistribution index (Mf) was calculated based on the variation of quantity of water collected at column outlet.It was observed that the Mf decreased with the increase in both the gas and liquid flow rate which was due to better spreading of the fluids with the increasing gas and liquid flow rate. The decrease in the Mf with the increasing gas and liquid flow rate indicates better distribution as reported in the literature 0 (best distribution) and 1 (worst distribution). Further, it was also noted that the pressure drop increased with the increasing gas and liquid flow rate. The hollow cone packing method shows the better distribution confirmed from the bulk voidage, Mf profiles, pressure drop variation, and flow profiles. A correlation has been proposed for the two-phase pressure drop for three packing methods.

Biological methanation is the production of CH4 from CO2 and H2. While this approach to carbon capture utilization have been widely researched in the recent years, there is a gap in the technology. The gap is towards the flexibility in biomethanation, utilizing biological trickling filters (BTF). With the current intermittent energy system, electricity is not a given surplus energy which will interfere with a continuous operation of biomethanation and will result in periods of operational downtime. This study investigated the effect of temperature and H2 supply during downtimes, to optimize the time needed to regain initial performance. Short (6 h), medium (24 h) and long (72 h) downtimes were investigated with combinations of three different temperatures and three different flow rates. The results from these 27 experiments showed that with the optimized parameters, it would take 60 min to reach 98.4% CH4 in the product gas for a short downtime, whereas longer downtimes needed 180 min to reach 91.0% CH4. With these results, the flexibility of biomethanation in BTFs have been proven feasible. This study shows that biomethanation in BTFs can be integrated into any intermittent energy system and thereby is a feasible Power-2-X technology. [ABSTRACT FROM AUTHOR]

[Display omitted] • Successful biomethanation in trickle bed reactors following a solar energy pattern. • Ramp-up times of < 16 min was achieved at a rate of 40.65 ± 0.11 NL H 2 L−1 d−1. • Standby periods function as a natural clean-in-place to convert accumulated acids. • Producing grid injected CH 4 retained 50.70 % of the photovoltaic power input. • Levelised cost of production of CH 4 was demonstrated to be 147.84 $ (MWh)−1. The accelerating green transition envisions large shares of renewable intermittent power supplies, which challenges the balancing of the grid. A promising approach to long-term storage is the power-to-X technology of biomethanation. This study developed an operating model for ex situ biomethanation in a trickle bed reactor (TBR) based on daily photovoltaic (PV) solar generation profiles from the California Flats solar cell park and demonstrated long-term discontinuous biomethanation of raw biogas. The TBR was operated discontinuously for 29 days, where biomethane admissible for natural gas grid injection could be achieved within a ramp-up time of < 16 min after an adaptation period of 6 days with a purity of < 2 % hydrogen and > 97.5 % biomethane. The shutdown periods demonstrated a continuous digestion of accumulated acids and biomass. Therefore, shutting off the hydrogen addition could synergistically be employed as a clean-in-place procedure, where ∼60 % of the accumulated volatile fatty acids were converted during 12 h of standby. The TBR performance was subsequently used to evaluate the economic feasibility of integrating biomethanation to convert and store solar PV energy. The levelized cost of production of grid-quality biomethane by a small commercial biomethanation system, subject to solar PV energy (28 MWh e d−1), was found to be 147.84 $ (MWh CH4 HHV)−1 in a 2030 scenario. [ABSTRACT FROM AUTHOR]

Trickle beds are among the most used reactors in different sectors of chemical industries. In this work the aim was to develop a general heterogeneous multiscale model for continuous trickle bed reactors, which enables the calculation of instantaneous concentration and temperature changes as well as the stationary behaviour of the reactor. The model development was based on solving simultaneously both the energy and mass balances for the continuous gas and liquid phases and for the stagnant catalyst particles. Mass transfer coefficients and pressure drop equations from well-established correlations were used. The developed model is aimed to be as general as possible in order to be used as a framework for other kind of bed reactors and arbitrary reaction schemes. The model can be simplified taking into consideration only one or two phases, and in this case it was applied to catalytic sugar oxidation to sugar acid and the effect of catalyst shape and size was investigated. Simulation results revealed that complete sugar conversion was achieved only for small catalyst particles, also the length of the reactor affects the conversion of arabinose more than the residence time or the bed radius: in fact for much bigger particles the conversion can also be achieved for longer reactor beds. [Display omitted] • Development of 3 phases dynamic trickle bed reactor model. • Developed model was used to study the arabinose oxidation. • Effect of shape and size of catalyst was studied numerically. • Model was successfully implemented in gProms. [ABSTRACT FROM AUTHOR]

[Display omitted] • Multiphase flow simulation in Trickle-Bed Reactors (TBR) using the Volume-Of-Fluid approach (VOF) • Pressure drop, liquid saturation and wetting efficiency prediction are investigated. • Three different catalyst shape particle loadings: spheres, trilobes and quadrilobes are studied. • Satisfactory predictions of hydrodynamic parameters: two-phase pressure drop, liquid saturation and wetting efficiency. • New wetting efficiency correlation accounting for gas velocity and particle shape effects. The characterization of hydrodynamics in Trickle-Bed-Reactors is a complex task due to the opacity of the medium. In particular, the determination of pressure drop, liquid saturation , wetting of the catalyst surface and catalyst shape effect on these parameters is very important for optimal catalyst use and reactor operation. Measurements under industrial conditions are limited to indirect estimations, and direct measurement methods are limited to near-ambient conditions. In this context, the objective of the present article is to use Computational-Fluid-Dynamics to investigate pressure drop, liquid saturation and wetting efficiency in Trickle-Bed-Reactors and to improve existing correlations, with a special focus on the catalyst shape effect and wetting prediction. The Volume-Of-Fluid approach was used to simulate two-phase flow through particle loadings of spherical, trilobe and quadrilobe-shaped particles. The numerical model was validated against literature correlations in terms of pressure drop, liquid holdup and wetting efficiency. The CFD model was then employed to explore two effects that does not reach out a consensus in existing literature, i.e effects of particle shape and gas-phase velocity on wetting efficiency. As a result, it was shown that CFD provides good predictions of pressure drop and liquid saturation for different catalyst particle shapes, the achieved deviations between CFD results and correlation estimations are below 20%. A new wetting efficiency correlation is also proposed. This new correlation is able to predict wetting efficiency with a precision of 6.99% for a wide range of liquid velocities (from 0.2 to 0.8 cm/s) and gas velocities (from 5 to 20 cm/s) and three particle shapes. [ABSTRACT FROM AUTHOR]

• Newly developed dynamic radioactive particle tracking system. • Probability distribution of heavy metal contaminants deposition. • Heavy metal deposition related to pressured drops. A newly developed modified Dynamic Radioactive Particle Tracking system (DRPT) was used to investigate the heavy metal contaminants deposition locations in different catalyst beds, sphere, cylinder, trilobe, and quadrilobed in Trickle Bed Reactors. In the present paper, Kernel Density Estimator (KDE) was used to estimate the probability density distributions of heavy metal contaminants depositions in terms of bed radius height. The result shows that the four cases have similar probability density distribution in terms of radius, while the spherical catalyst has the larger distribution range in terms of bed height. The heavy metal deposition is directly related to the pressure drops along the bed height which indicate the bed porosity and intricate bed structure in catalyst packed beds. Heavy metals have more chance to deposit at higher levels of packed beds with higher pressure drops. [ABSTRACT FROM AUTHOR]