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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.

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.

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.

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.

Currently, most plastic waste stems from packaging materials, with a large proportion of this waste either discarded by incineration or used to derive fuel. Accordingly, there is growing interest in the use of pyrolysis to chemically recycle non-recyclable (i.e., via mechanical means) plastic waste into petrochemical feedstock. This comparative study compared pyrolysis characteristics of two types of reactors, namely fixed and fluidized bed reactors. Kinetic analysis for pyrolysis of SRF was also performed. Based on the kinetic analysis of the pyrolytic reactions using differential and integral methods applied to the TGA results, it was seen that the activation energy was lower in the initial stage of pyrolysis. This trend can be mainly attributed to the initial decomposition of PP components, which was subsequently followed by the decomposition of PE. From the kinetic analysis, the activation energy corresponding to the rate of pyrolysis reaction conversion was obtained. In conclusion, pyrolysis carried out using the fluidized bed reactor resulted in a more active decomposition of SRF. The relatively superior performance of this reactor can be attributed to the increased mass and heat transfer effects caused by fluidizing gases, which result in greater gas yields. Regarding the characteristics of liquid products generated during pyrolysis, it was seen that the hydrogen content in the liquid products obtained from the fluidized bed reactor decreased, leading to the formation of oils with higher molecular weights and higher C/H ratios, because the pyrolysis of SRF in the fluidized bed reactor progressed more rapidly than that in the fixed bed reactor.

Phosphorus (P) is a significant limiting nutrient which is essential for all forms of lives. However, phosphate rock reserves are depleting rapidly due to population growth. At the same time, several countries have imposed legislative regulations on P-release into surface waters due to eutrophication. Nutrient recovery from wastewater can facilitate a sustainable, cost-effective and environment-friendly source of phosphorus. Although P-recovery as struvite from wastewater has been widely studied for a long time, there still exists a lot of challenges for widespread full-scale implementation. This paper presents a comprehensive analysis of the current state of the technologies for phosphorus recovery in the form of struvite. Fluidized bed reactors (FBRs) are widely used compared to continuously stirred reactors for P-recovery as struvite because of different solid and liquid retention time. Commercially available technologies were reported to accomplish about 80% P-removal efficiencies with a reasonable P-recovery for the most of the cases. The struvite production rate of various technologies varies from 0.89 to 13.7 kg/kg influent P. Nevertheless, these technologies are associated with several shortcomings such as high operational costs, high energy consumption, and large footprint. Increasing efforts focusing on the development of sustainable and commercially feasible technologies are expected in this sector as P-recovery is considered to be the future of wastewater engineering.

In this paper, the most influential parameters (numerical and operating parameters) affecting the performance of fluidized bed reactors are studied. The investigated parameters are constitutive and numerical parameters, minimum fluidization velocity, operating pressure, temperature, gas distributor, and particle size distribution (PSD). Furthermore, the recent methods for solving population balance equations coupled with computational fluid dynamic (CFD-PBM) are discussed. The direct quadrature method of moments (DQMOM) was found to be the most efficient method for CFD-PBM coupled simulations. It must be pointed out that due to the computational cost there is limitation on the application of CFD in practical reactor with detailed mass/heat transfer and reaction mechanisms, especially under industrial operating condition.

This study explored the feasibility of fluoride removal from simulated semiconductor industry wastewater and its recovery as calcium fluoride using fluidized bed crystallization. The continuous reactor showed the best performance (>90% fluoride removal and >95% crystallization efficiency) at a calcium-to-fluoride ratio of 0.6 within the first 40 days of continuous operation. The resulting particle size increased by more than double during this time, along with a 36% increase in the seed bed height, indicating the deposition of CaF2 onto the silica seed. The SEM-EDX analysis showed the size and shape of the crystals formed, along with the presence of a high amount of Ca-F ions. The purity of the CaF2 crystals was determined to be 91.1% though ICP-OES analysis. Following the continuous experiment, different process improvement strategies were explored. The addition of an excess amount of calcium resulted in the removal of an additional 6% of the fluoride; however, compared to this single-stage process, a two-stage approach was found to be a better strategy to achieve a low effluent concentration of fluoride. The fluoride removal reached 94% with this two-stage approach under the optimum conditions of 4 + 1 h HRT combinations and a [Ca2+]/[F−] ratio of 0.55 and 0.7 for the two reactors, respectively. CFD simulation showed the impact of the inlet diameter, bottom-angle shape, and width-to-height ratio of the reactor on the mixing inside the reactor and the possibility of further improvement in the reactor performance by optimizing the FBR configuration.

Biomass gasification is a versatile thermochemical process that can be used for direct energy applications and the production of advanced liquid and gaseous energy carriers. In the present work, the results are presented concerning the H2 production at a high purity grade from biomass feedstocks via steam/oxygen gasification. The data demonstrating such a process chain were collected at an innovative gasification prototype plant coupled to a portable purification system (PPS). The overall integration was designed for gas conditioning and purification to hydrogen. By using almond shells as the biomass feedstock, from a product gas with an average and stable composition of 40%-v H2, 21%-v CO, 35%-v CO2, 2.5%-v CH4, the PPS unit provided a hydrogen stream, with a final concentration of 99.99%-v and a gas yield of 66.4%.

Short-chain olefins are the important feedstock for the chemical industries. The selection of a proper catalyst for oxidative dehydrogenation (ODH) reaction is critical. Here, the study summarized different catalysts by physicochemical techniques such as BET surface area, Raman spectroscopy, and temperature programmed reduction (TPR). The BET analysis of different catalysts gives an optimum value of active and metal loading catalysts for optimum alkenes selectivity. From different Raman spectroscopy analyses, the study pointed out the factor responsible for varying mono vanadate and poly vanadate formation. From TPR analysis of different catalysts, this study pointed out the factors that varied on increasing or decreasing temperature and the effect on the selectivity of alkenes. The effect of different operating conditions was studied. Without catalyst regeneration after each ODH run, the catalyst under the study shows stable behavior and increases the selectivity of the desired product. The CREC riser simulator was used for ODH of propane and ethane, while two zones of fluidized bed reactor (TZFBR) and ICFBR reactors were used for ODH of butane. From the study of MoO 3 /MgO catalyst, it was observed that TZFBR have high selectivity of butadiene than CFBR and fixed bed reactor. It was concluded that the catalyst VO x –Nb/La-ɣAl 2 O 3 has high conversion (20.1%) of ethane and good selectivity of (85.7%) of ethylene, while in ODH of propane and butane the catalyst 7.5 VO x /ɣAl 2 O 3 ·ZrO 2 (1:1) and MoO 3 /MgO have high selectivity of propane and 1,3-butadiene respectively. This review will help researchers in decision making for the selection of proper catalyst for ODH of alkane to alkenes.