Steam - oxygen gasification of refuse derived fuel in fluidized beds: Modelling and pilot plant testing

A one-dimensional kinetic model for steam‑oxygen gasification of refuse derived fuel in a bubbling fluidized bed reactor has been developed. The model incorporates the reaction network of steam‑oxygen gasification within the fluid dynamics of a fluidized bed to predict waste and tars conversion, gas composition and overall gasification performance. The model was validated by comparing outlet products composition and temperature profile with experimental data from a pilot-scale fluidized bed gasifier, operated at different conditions. The model showed accurate predictive capability and ease of computation. The effects of the operating conditions on gas yield and process efficiency were evaluated and the most appropriate fuel feeding height, equivalent ratio and the relative amount of steam to inject were identified

7-Bromo-4b-methyl-7,8-dihydro-4bH-9-thia-8a-aza­fluorene 9,9-dioxide

The title compound, C12H12BrNO2S, was isolated after direct irradiation (hν 350 nm, hexa­ne) of a mixture of stereoisomeric sulfonamides containing a vicinal dibromide and a conjugated diene. This product is one of a group of substrates that has contributed to our understanding of the photoreactivity patterns of non-bridged sulfonamides. The crystal structure was determined from a non-merohedrally twinned data set, where the twin law corresponded to a 180° rotation about the a* axis. The minor twin component refined to a value of 0.176 (3). The conformation of the mol­ecule is planar at one end, as the benzene ring and the adjacent fused five-membered ring are coplanar, and U-shaped at the other end, where the five-membered ring is fused to the heterocyclic six-membered ring containing an allyl bromide group

Measurement of solids circulation rates with optical techniques in circulating beds and comparison to pressure drop methods

The number of applications employing circulating fluidized beds has increased considerably over the last years following the important development of chemical looping technologies for power generation (combustion) or fuel conversion (reforming) with inherent CO2 capture. The performance of these reactors is strongly determined by the amount of solids transferred from one reactor to the other, commonly referred to as the Solids Circulation Rate (SCR). The solids inventory, particle characteristics and gas velocities strongly influence the SCR. The determination of the SCR has been carried out using invasive and non-invasive measurement techniques. The direct measurement through solids collection in the loop seal is the most applied technique, but this technique requires opening of the loop seals and thus may be expensive, whereas other methods suffer from large inaccuracies. There is yet no optimal technique available that combines good accuracy with reasonable costs, as recently also discussed by Alghamdi et al. (1). In this work, a pseudo 2D internally circulating fluidized bed (Figure 1) has been built to explore the potential of optical techniques like Particle Image Velocimetry (PIV) combined with Digital Image Analysis (DIA) for non-invasive, whole-field measurements. Moreover, the setup allows for the measurement of the pressure drop (fluctuations) along the riser and the collection of particles circulating from one reactor to the other, so that the three different measurement techniques can be compared. Please click Additional Files below to see the full abstract

Characterization of wake properties in freely bubbling fluidized beds using Particle Image Velocimetry

The performance of fluidized beds in many physical or chemical operations is predominantly determined by the hydrodynamics and mass transfer characteristics. However, a proper description of a fluidized bed using phenomenological models requires correlations based on many different assumptions for the bubble and emulsion phases, where most of these assumptions have not been validated thoroughly at different operating conditions. One of the most typical assumptions is the fact that the wake of a bubble rises with exactly the same velocity as the bubble and occupies a specific and constant fraction in the bed, commonly around 15% of the bubble volume (1). The wake fraction has been studied using optical techniques and the geometry of the single bubbles injected has been analysed at different experimental conditions (2). However, these results are mainly based on geometric observations, and are not based on specific properties of fluidized beds. In this study, two new methods for the characterization of wake properties in fluidized beds are developed and studied based on the dynamics of the solids phase. Particle Image Velocimetry (PIV) allows to determine the solids phase velocity profiles in detail, which is used for the investigation of the wake properties. PIV combined with Digital Image Analysis (DIA) can provide the average solids mass fluxes throughout the fluidized bed, along with the bubble properties. When relating all positive solids fluxes to the solids carried along by the bubbles in their wakes, the average wake fraction can be obtained directly, as presented in the Figure 1. This method provides information on average results and therefore accounts for all bubbles observed during the experimental evaluation. Please click Additional Files below to see the full abstract

Hydrogen permeation studies of composite supported alumina-carbon molecular sieves membranes: Separation of diluted hydrogen from mixtures with methane

One alternative for the storage and transport of hydrogen is blending a low amount of hydrogen (up to 15 or 20%) into existing natural gas grids. When demanded, hydrogen can be then separated, close to the end users using membranes. In this work, composite alumina carbon molecular sieves membranes (Al-CMSM) supported on tubular porous alumina have been prepared and characterized. Single gas permeation studies showed that the H2/CH4 separation properties at 30 °C are well above the Robeson limit of polymeric membranes. H2 permeation studies of the H2–CH4 mixture gases, containing 5–20% of H2 show that the H2 purity depends on the H2 content in the feed and the operating temperature. In the best scenario investigated in this work, for samples containing 10% of H2 with an inlet pressure of 7.5 bar and permeated pressure of 0.01 bar at 30 °C, the H2 purity obtained was 99.4%.This project received funding from the Fuel Cells and Hydrogen 2 Joint Undertaking under grant agreement N700355 (Hygrid). This Joint Undertaking receives support fromthe European Union’s Horizon 2020 Research and InnovationProgramme, Hydrogen Europe and N. ERGH