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Date palm trees, being an important source of nutrition, are grown at a large scale in Saudi Arabia. The biomass waste of date palm, discarded of in a non-environmentally-friendly manner at present, can be used for biofuel generation through the fast pyrolysis technique. This technique is considered viable for thermochemical conversion of solid biomass into biofuels in terms of the initial investment, production cost, and operational cost, as well as power consumption and thermal application cost. In this study, a techno-economic analysis has been performed to assess the feasibility of converting date palm waste into bio-oil, char, and burnable gases by defining the optimum reactor design and thermal profile. Previous studies concluded that at an optimum temperature of 525 °C, the maximum bio-oil, char and gases obtained from pyrolysis of date palm waste contributed 38.8, 37.2 and 24% of the used feed stock material (on weight basis), respectively, while fluidized bed reactor exhibited high suitability for fast pyrolysis. Based on the pyrolysis product percentage, the economic analysis estimated the net saving of USD 556.8 per ton of the date palm waste processed in the pyrolysis unit. It was further estimated that Saudi Arabia could earn USD 44.77 million per annum, approximately, if 50% of the total date palm waste were processed through fast pyrolysis, with a payback time of 2.57 years. Besides that, this intervention will reduce 2029 tons of greenhouse gas emissions annually, contributing towards a lower carbon footprint.

Biochar activation is critical for producing high-performance adsorbents; however, conventional activation methods are energy-intensive and difficult to control, particularly when air is used as an activating agent. This study investigates CO2–air co-activation in a laboratory-scale fluidized bed reactor as an energy-efficient alternative. Experiments were conducted at 750–850 °C under varying gas flow rates with a constant CO2/O2 ratio. Optimal properties were achieved at 800 °C and 0.2–0.3 L/min CO2, yielding a maximum BET surface area of 479 m2/g, a micropore contribution of 42%, and controlled carbon conversion (~25–35% yield). Aspen Plus equilibrium simulations also confirm that CO2-only activation remains endothermic (heat duty up to +0.07 kW), air-only activation becomes strongly exothermic (down to −0.13 kW), while the CO2–air mixture exhibits near-thermoneutral to mildly exothermic behavior (+0.13 to −0.10 kW), thereby reducing external energy demand potentially by approximately 60–70% compared with CO2-only activation and significantly improving process stability. These results demonstrate that CO2–air co-activation offers a practical route to produce high-quality activated biochar with controlled porosity and improved energy efficiency.

Esters are versatile compounds with a wide range of applications in various industries due to their unique properties and pleasant aromas. Conventionally, the manufacture of these compounds has relied on the chemical route. Nevertheless, this technique employs high temperatures and inorganic catalysts, resulting in undesired additional steps to purify the final product by removing solvent residues, which decreases environmental sustainability and energy efficiency. In accordance with the principles of “Green Chemistry” and the search for more environmentally friendly methods, a new alternative, the enzymatic route, has been introduced. This technique uses low temperatures and does not require the use of solvents, resulting in more environmentally friendly final products. Despite the large number of studies published on the biocatalytic synthesis of esters, little attention has been paid to the reactors used for it. Therefore, it is convenient to gather the scattered information regarding the type of reactor employed in these synthesis reactions, considering the industrial field in which the process is carried out. A comparison between the performance of the different reactor configurations will allow us to draw the appropriate conclusions regarding their suitability for each specific industrial application. This review addresses, for the first time, the above aspects, which will undoubtedly help with the correct industrial implementation of these processes.

In petroleum refineries, naphtha reforming units produce reformate streams and as a by-product, hydrogen (H2). Naphtha reforming units traditionally deployed are designed as packed bed reactors (PBR). However, they are restrained by a high-pressure drop, diffusion limitations in the catalyst, and radial and axial gradients of temperature and concentration. A new design using the fluidized bed reactor (FBR) surpasses the issues of the PBR, whereby the incorporation of the membrane can improve the yield of products by selectively removing hydrogen from the reaction side. In this work, a sequential modular simulation (SMS) approach is adopted to simulate the hydrodynamics of a fluidized bed membrane reactor (FBMR) for catalytic reforming of naphtha in Aspen Plus. The reformer reactor is divided into five sections of plug flow reactors and a continuous stirrer tank reactor with the membrane module to simulate the overall FBMR. Similarly, a fluidized bed reactor (FBR), without membrane permeation phenomenon, is also modelled in the Aspen Plus environment for a comparative study with FBMR. In FBMR, the continuous elimination of permeated hydrogen enhanced the production of aromatics compound in the reformate stream. Moreover, the exergy and economic analyses were carried out for both FBR and FBMR.

Chemical looping combustion (CLC) has been recognized as a promising CO2 capture technology, in which oxygen carriers (OCs) transport lattice oxygen to the fuel instead of the air. This study aims to evaluate a newly developed perovskite OC for biomass CLC and to clarify the role of staged fuel conversion in improving gas–solid redox efficiency. This is the first application of perovskite OC CaMn0.625Ti0.125Fe0.125Mg0.125O3 in biomass CLC using a dual-stage fluidized bed. The perovskite OC was synthesized via a solid-phase synthesis method, and its performance in a dual-stage fluidized bed reactor was evaluated using pine wood chips and furfural residues as model solid fuels. The in situ conversion of volatile compounds and gasification products derived from the two biomass types was comprehensively studied. The effects of operational parameters, including temperature, OC-to-biomass ratio, and gas flow rate, on the combustion efficiency and CO2 yield were examined. Results showed that separated gasification–combustion enhanced the combustion efficiency and CO2 yield. At 950 °C, an OC-to-pine chip ratio of 100:1, and a gas flow rate of 0.7 L/min, the maximum combustion efficiency and CO2 yield of 79% and 82% were obtained, respectively. Moreover, under the optimal gasification conditions (gasification rate > 99%), increasing the fuel concentration resulted in an increase in the oxygen release from 0.21 g to 0.40 g. Concurrently, the corresponding total oxygen demand increased from 4.34% to 10.56%, indicating the suitability of CaMn0.625Ti0.125Fe0.125Mg0.125O3 in the CLC of biomass.

Gasification of plastic waste is an emerging technology of particular interest to the scientific world given the production of a hydrogen-rich gas from waste material. Devolatilization is a first step thermochemical decomposition process which is crucial in determining the quality of the gas in the whole gasification process. The devolatilization of polypropylene (a key compound of plastic waste) has been investigated experimentally in a bench-scale fluidized bed reactor. Experimental tests were carried out by varying two key parameters of the process—the size of the polypropylene spheres (8–12 mm) and temperature (650–850 °C). Temperature shows the highest influence on the process. Greater molecular cracking results were more pronounced at higher temperatures, increasing the production of light hydrocarbons along with the formation of solid carbon residue and tar. The overall syngas output reduced, while the H2 content increased. Furthermore, a pseudo-first-order kinetic model was developed to describe the devolatilization process (Eapp = 11.8 kJ/mol, A1 = 0.55 s−1, ψ = 0.77).

This study utilized a fluidized bed reactor (FBR) for fluoride removal from high-concentration fluoride-ion-containing simulated semiconductor industry wastewater and recovered high-purity CaF2 crystals. The effects of hydraulic retention time (HRT), pH, Ca2+ to F− ratio, upflow velocity, seed size and seed bed height were investigated by performing lab-scale batch experiments. Considering fluoride removal and CaF2 crystallization efficiency, 5 h HRT, pH 6, seed height of 50 cm and [Ca2+]/[F−] ratio of 0.55 (mol/mol) were found to be optimum. The effect of the interaction between the important process parameters on fluoride removal was further analyzed using response surface methodology (RSM) experimental design. The results showed that all the individual parameters have a significant impact (p = 0.0001) on fluoride removal. SEM-EDX and FTIR analysis showed the composition of the crystals formed inside FBR. HR-XRD analysis confirmed that the crystalline structure of samples was mainly CaF2. The results clearly demonstrated the feasibility of silica seed material containing FBR for efficient removal and recovery of fluoride as high-purity calcium fluoride crystals.

Gas–solid fluidized bed reactors are widely used in the power generation industry. The critical effect of the presence of liquid phase, either as a result of heat, chemical reaction or physical interaction, on the hydrodynamics of the reactor is well recognized by academic researchers and industrial operators. However, theory and simulation frameworks to predict such a condition using the continuum modeling approach are not yet available. This study first shows the significant changes in the flow pattern and distinguishable flow regimes in a slightly wet fluidized bed recorded by an advanced imaging technique. The study then describes the development and implementation of new mathematical formulations for wet particle-particle interactions in a continuum model based on the classic kinetic theory of granular flow (KTGF). Quantitative validation, carried out by comparing the predicted and measured fluidization index (FI) expressed in terms of pressure drop, has shown a good match. The prediction also demonstrates increased bubble splitting, gas channeling, slugging fluidization, and energy dissipation induced by liquid bridges developing from wet particle interactions. These characteristics are similar to those commonly observed in the fluidization of cohesive powders. This model constitutes an important step in extending the continuum theories of dry flow to wet particle-particle interactions. This will allow accurate description and simulation of the fluidized bed in its widest application including power generation systems that involve wet particle fluidization.

In this study, dolomite was heated under CO2 and N2 gases using fluidized bed reactor from 85 °C to 835 °C. Dolomite under N2 atmosphere did not show any significant changes on its crystallite size, suggesting there is no significant chemical reaction. On the other hand, dolomite under CO2 atmosphere shows no significant changes on its crystallite size until it reaches high temperature (> 800 °C) where MgO started to be observed in X- ray diffraction. This shows that few chemical reactions started to happen in this reaction condition.

The COVID-19 pandemic has caused a heavy expansion of plastic pollution due to the extensive use of personal protective equipment (PPE) worldwide. To avoid problems related to the entrance of these wastes into the environment, proper management of the disposal is required. Here, the steam gasification/pyrolysis technique offers a reliable solution for the utilization of such wastes via chemical recycling into value-added products. The aim was to estimate the effect of thermo-chemical conversion temperature and steam-to-carbon ratio on the distribution of gaseous products obtained during non-catalytic steam gasification of 3-ply face masks and KN95 respirators in a fluidized bed reactor. Experimental results have revealed that the process temperature has a major influence on the composition of gases evolved. The production of syngas was significantly induced by temperature elevation from 700 °C to 800 °C. The highest molar concentration of H2 gases synthesized from both types of face masks was estimated at 800 °C with the steam-to-carbon ratio varying from 0 to 2. A similar trend of production was also determined for CO gases. Therefore, investigated thermochemical conversion process is a feasible route for the conversion of used face masks to valuable a product such as syngas.