Fluidized Bed Reactor

Excess Phosphate and nitrogen cause eutrophication and impair the quality of water resources. Hence the discharge of these nutrients, especially phosphate, into recipient water is usually regulated [1]. Several biological [2], physical and chemical methods [3-5] have been devised to remove phosphate from wastewaters. Overall, chemical precipitation [1] and fluidized-bed crystallization (FBC) remain the preferred methods for phosphate removal [6]. Compared to the high-moisture-content sludge generated from conventional chemical precipitation technology, the solid by-product from FBC reactors contains only about 1-5% moisture [7]. In general, phosphate removal by struvite precipitation in a fluidized bed crystallizer is superior to other approaches in terms of operating cost, efficiency and purity of by-products [1,7]. Phosphate removal by FBC however, suffers from two undesirable phenomena: (1) primary nucleation in the liquid phase and (2) abrasion of the mineral layer in the bed [8]. Both these occurrences produce small particles or ''fines'', which leave the bed and goes to the top of the reactor and eventually to the effluent. These fine solids, together with the remaining phosphate in the solution, constitute the fraction of phosphate that is not removed by the FBC process. Fines may, however, aggregate onto the surface of some seed material resulting in relatively high phosphate removal. Sand is readily available, inexpensive and is widely used as seed material in various crystallization systems. However, struvite (MAP, MgNH 4 PO 4 Á6H 2 O) produced with sand as seed would require further purification if pure phosphate minerals are to be used as raw materials [9]. Hence, the use of appropriate seed material is necessary to produce phosphate crystals with the highest purity. In this study, MAP seeds synthesized from batch experiments were used as carriers for MAP crystallization in a fluidized-bed reactor. The effects of influent pH and Mg/P molar ratio on MAP crystallization were examined. Likewise, characterization and thermal decomposition of MAP crystals were investigated. The thermal stability of MAP crystals were evaluated using kinetic and thermodynamic parameters obtained during MAP crystallization at various pH values and Mg/P molar ratios. This study also provides evidence of the formation of new materials during the course of struvite thermal decomposition and the stability of MAP crystals in the presence of heat for various applications.

An integrated fluidized bed reactor (FBR) has been employed as the treatment for petrochemical industry wastewaters with high organic matter and aromatic compounds, under anaerobic and aerobic conditions. The system was operated at hydraulic residence time (HRT) of 2.7 and 2.2 h in the anaerobic and aerobic reactor, respectively. The degree of fluidization in the beds was 30%. This system showed a high performance on the removal of organic matter and aromatic compounds. At different organic loading rates (OLR), the chemical oxygen demand (COD) removal in the anaerobic reactor was close to 85% and removals of the COD up to 94% were obtained in the aerobic reactor. High removals of benzene, toluene, ethylbenzene, xylenes, styrene, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene and naphthalene were achieved in this study.

Bio-oil and bio-char were produced from corn cobs and corn stover (stalks, leaves and husks) by fast pyrolysis using a pilot scale fluidized bed reactor. Yields of 60% (mass/mass) bio-oil (high heating values are w20 MJ kg À1 , and densities >1.0 Mg m À3) were realized from both corn cobs and from corn stover. The high energy density of bio-oil, w20-32 times on a per unit volume basis over the raw corn residues, offers potentially significant savings in transportation costs particularly for a distributed ''farm scale'' bio-refinery system. Biochar yield was 18.9% and 17.0% (mass/mass) from corn cobs and corn stover, respectively. Deploying the bio-char co-product, which contains most of the nutrient minerals from the corn residues, as well as a significant amount of carbon, to the land can enhance soil quality, sequester carbon, and alleviate environmental problems associated with removal of crop residues from fields.

Comparative study of the artificial neural network and mechanistic model was carried out for NO removal in a bubbling fluidized bed reactor. The effects of temperature, superficial gas velocity and ammonia/nitric oxide ratio on the NO removal efficiency were determined and their optimum conditions were estimated by the experimental study, the artificial neural network and mechanistic models as well. The optimum values of ammonia/nitric oxide ratio, temperature and superficial gas velocity for the maximum NO removal efficiency were found to be 1.5, 300°C and 0.098 m/s, respectively. A mechanistic model was implemented in our previous study [Muhammad F. Irfan, Sang Done Kim and Muhammad R. Usman, 2009] and it was found that this model fitted well only at specific condition i.e. maximum conversion temperature (300°C). However, it failed to perfectly match with rest of the experimental data points at other temperatures and parametric conditions as well. To improve this, an artificial neural network modeling strategy was applied and its predictions were evaluated which were favorably matched with the experimental data rather than the mechanistic model.

Steam gasification studies were carried out in an atmospheric fluidised bed. The gasifier was operated over a temperature range of 700-900 8C whilst varying a steam/biomass ratio from 0.4 to 0.85 w/w. Three types of forestry biomass were studied: Pinus pinaster (softwood), Eucalyptus globulus and holm-oak (hardwood). The energy conversion, gas composition, higher heating value and gas yields were determined and correlated with temperature, steam/biomass ratio, and species of biomass used. The results obtained seemed to suggest that the operating conditions were optimised for a gasification temperature around 830 8C and a steam/biomass ratio of 0.6-0.7 w/w, because a gas richer in hydrogen and poorer in hydrocarbons and tars was produced. These conditions also favoured greater energy and carbon conversions, as well the gas yield. The main objective of the present work was to determine what reactions were dominant within the operation limits of experimental parameters studied and what was the effect of biomass type on the gasification process. As biomass wastes usually have a problem of availability because of seasonal variations, this work analysed the possibility of replacing one biomass species by another, without altering the gas quality obtained.

Widespread application of bubbling fluidised bed reactors to chemical processes has been hindered by some inherent drawbacks, like the high degree of internal mixing and the low contact efficiency between gas and solid phases. The staging of fluidised beds through the insertion of horizontal baffles may overcome these drawbacks, approaching plug-flow and limiting bubble size. The authors, based on theory and experiments, have developed a methodology to properly design staged fluid bed catalytic reactors, considering gas and solid backmixing, bubble size, flooding and dynamic forces, which is described in the paper.

This review reports recent advances on chemical-looping combustion (CLC). CLC is a promising technology for fossil fuel combustion preventing CO 2 dilution with flue gases, mainly nitrogen. In CLC, the solid oxygen carrier supplies the stoichiometric oxygen needed for CO 2 and water formation, and this leads to a free nitrogen mixture. As a result, the requirement of CO 2 separation from flue gases, a major cost for CO 2 capture, is circumvented. Furthermore, formation of NO x is also reduced. A good oxygen carrier for CLC shall readily react with the fuel gas and shall be reoxidized upon being contacted with oxygen. An oxygen carrier is typically formed by a metal oxide and an inert binder, which provide, respectively, oxygen storage, fluidizability and mechanical strength. Over the last 10 years, several research groups have been researching oxygen carriers which are both active and stable under fluidized bed conditions. While Fe, Ni, Cu, Mn and Co oxides are potential oxygen carrier materials, recent studies show that Ni is best suited for CLC. Few studies have been devoted to the solid-state kinetics of both reduction and oxidation with either a nucleation-nuclei growth or unreacted shrinking core models being considered. In order to implement CLC, two interconnected fluidized bed reactors (the fuel and air reactor) with the oxygen carrier circulated between units have been proposed. While reactor design, modeling and hydrodynamics are matters that have been analyzed by several research groups; these topics still require more attention and investigation. Preliminary economic assessments, have suggested that CLC holds great promise for combustion processes, having the potential for achieving very efficient and low cost CO 2 capture. Even with these favorable prospects, commercial scale-up of CLC still depends nowadays on the availability of highly performing and stable oxygen carriers.

Thermite mixtures with improved contact between the fuel and oxidizer can provide increased reaction rates compared with traditional thermite mixtures. One technique to create thermite mixtures with improved contact is to deposit the oxidizer directly onto nanometer-sized fuel particles. This study investigates the atomic layer deposition (ALD) of SnO 2 onto nanoparticles using SnCl 4 and H 2 O 2 reactants. The nanoparticle ALD was performed in a small, hot wall, vertical fluidized bed reactor. The SnO 2 ALD was first demonstrated on ZrO 2 nanoparticles. Auger electron spectroscopy, inductively coupled plasma-atomic emission spectroscopy (ICP-AES), transmission electron microscopy (TEM) and particle size distribution analysis were used to characterize the SnO 2 -coated ZrO 2 nanoparticles. Subsequently, SnO 2 ALD was performed on Al nanoparticles. The SnO 2 -coated Al nanoparticles were analyzed using ICP-AES and TEM. The SnO 2 -coated Al and the uncoated Al particles were also ignited and filmed with a digital video recorder. Although the SnO 2 -coated Al particles were far from stoichiometric thermite composites, the SnO 2 -coated Al particles reacted much more quickly and violently than the uncoated Al particles. The lower than expected Sn percent by mass observed on the SnO 2 -coated Al nanoparticles highlighted a major difficulty with coating nanoparticles. The nanoparticles have an extremely high surface area and the required reactant exposures are large even when assuming 100% reactant efficiency. These results illustrate the utility of ALD techniques to coat oxidizers on fuel nanoparticles to create enhanced thermite materials. D

The slow and fast pyrolysis of cherry seeds (CWS) and cherry seeds shells (CSS) was studied in fixed-bed and fluidized bed reactors at different pyrolysis temperatures. The effects of reactor type and temperature on the yields and composition of products were investigated. In the case of fast pyrolysis, the maximum bio-oil yield was found to be about 44 wt% at pyrolysis temperature of 500°C for both CWS and CSS, whereas the bio yields were of 21 and 15 wt% obtained at 500°C from slow pyrolysis of CWS and CSS, respectively. Both temperature and reactor type affected the composition of bio-oils. The results showed that bio-oils obtained from slow pyrolysis of CWS and CSS can be used as a fuel for combustion systems in industry and the bio-oil produced from fast pyrolysis can be evaluated as a chemical feedstock.

Silicon nitride thin films with thicknesses around 1 Am were deposited on AISI316 steel by Chemical Vapor Deposition in a Fluidized Bed Reactor at Atmospheric Pressure (AP/FBR-CVD). The films were obtained by reaction of SiCl 4 and NH 3 in a reducing atmosphere at temperatures in the range 725 -775 -C. They were amorphous and substoichiometric. Activation of the bed particles through alternating reaction steps resulted in a higher deposition rate. The formation of chromium nitride was detected for several microns beneath the film. The deposition temperature was found to have a great influence in their morphology and mechanical properties. The coatings presented hardness values up to 26 GPa. D

The kinetics of n-butane oxidation to maleic anhydride over a commercial V-P-O catalyst for uid bed reactors was investigated systematically and modelled according to a scheme of eight reactions, involving also the combustion of both n-butane and maleic anhydride to CO and CO2, as well as the formation and the combustion of acetic and acrylic acids. A one-dimensional, heterogeneous (two-phase) uid bed reactor model incorporating the independently derived kinetic scheme was successfully validated on a predictive basis against conversion, selectivity and steam production data collected in a full-scale MA production plant. ?

Rice husk lean-combustion in a bubbling and atmospheric fluidized bed reactor (FBR) of 0.3 m diameter with expansion to 0.4 m in the freeboard zone and 3 m height was investigated. Experiment design – response surface methodology (RSM) – is used to evaluate both excess air and normal fluidizing velocity influence (independent and controllable variables), in the combustion efficiency (carbon transformation), bed and freeboard temperature and silica content in the ashes. Hot gases emissions (CO2, CO and NOx), crystallographic structure and morphology of the ash are also shown. A cold fluidization study is also presented. The values implemented in the equipment operation, excess air in the range of 40–125% and normal fluidization velocities (0.13–0.15 Nm/s) show that the values near the lower limit, encourage bed temperatures around 750 °C with higher carbon transformation efficiencies around 98%. However, this condition deteriorated the amorphous potential of silica present in the ash...

Laccase from the white rot fungus Coriolopsis polyzona was immobilized for the first time through the formation of cross-linked enzyme aggregates (CLEAs). Laccase CLEAs were produced by using 1000g of polyethylene glycol per liter of enzyme solution as precipitant and 200muM of glutaraldehyde as a cross-linking agent. These CLEAs had a laccase activity of 148Ug(-1) and an activity recovery of 60.2% when using 2,2'-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) as substrate. CLEAs formed by co-aggregation with bovine serum albumin (BSA) as a stabilizer showed lower laccase activity and affinity for ABTS than those without BSA. The CLEAs co-aggregated with BSA showed higher residual activity against a protease, NaN(3), EDTA, methanol and acetone. The thermoresistance was higher for CLEAs than for free laccase and also higher for CLEAs co-aggregated with BSA than for simple CLEAs when tested at a pH of 3 and a temperature of 40 degrees C. Finally, laccase CLEAs were teste...

In this paper, an experimental investigation, an analytical analysis and a numerical model of a typical four-point bending test on a honeycomb sandwich panel are proposed. The honeycomb core is modelled as a single solid layer of equivalent material properties. Analytical and numerical (finite element) homogenization approaches are used to compute the effective properties of the honeycomb core. A general kinematic model (unified formulation) has been adopted and used for the modelling of honeycomb sandwich panel submitted to the bending test. A comparative study of major classes of representative theories has been considered. Qualitative and quantitative assessments of displacement, stress have been presented and discussed.

A laboratory scale fluidized bed pyrolysis system has been designed and fabricated for obtaining liquid fuel from biomass solid wastes. The components of the system are: fluidized bed reactor, gas preheating chamber, reactor feeder, heating system, heater feeder, liquid condenser and liquid collectors. The reactor operating parameters and dimensions have been considered on the basis of cold model study and thermogravimetric analysis (TGA) of the feedstock. The major components made of stainless steel. A number of trial runs have been carried out with jute-stick as feedstock. At an optimum pyrolysis condition of fluidized bed temperature of 425 o C with 300-600µm feed particle size and 30 l/min fluidizing gas flow rate, the oil product is found to be 50 wt% of dry biomass feed. The oil obtained at this optimum condition is analyzed for their fuel properties-compared with other biomass pyrolysis oils and petroleum product. The fuel properties compared are physical properties, calorific value, elemental (CHNOS) analysis and chemical composition using FTIR spectroscopy.

Biotite dissolution rates in acidic solutions were determined in fluidized-bed reactors and flowthrough columns. Biotite dissolution rates increased inversely as a linear function of pH in the pH range 3-1, where the rate order n = -0.34. Biotite dissolved incongruently over this pH range, with preferential release of magnesium and iron from the octahedral layer. Release of tetrahedral silicon was much greater at pH 3 than at higher pH. Iron release was significantly enhanced by low pH conditions. Solution compositions from a continuous exposure flow-through column of biotite indicated biotite dissolves incongruently at pH 4, consistent with alteration to a vermiculite-type product. Solution compositions from a second intermittent-flow column exhibited elevated cation release rates upon the initiation of each exposure to solution.

Rice husk lean-combustion in a bubbling and atmospheric fluidized bed reactor (FBR) of 0.3 m diameter with expansion to 0.4 m in the freeboard zone and 3 m height was investigated. Experiment design e response surface methodology (RSM) e is used to evaluate both excess air and normal fluidizing velocity influence (independent and controllable variables), in the combustion efficiency (carbon transformation), bed and freeboard temperature and silica content in the ashes. Hot gases emissions (CO 2 , CO and NO x ), crystallographic structure and morphology of the ash are also shown. A cold fluidization study is also presented. The values implemented in the equipment operation, excess air in the range of 40 e125% and normal fluidization velocities (0.13e0.15 Nm/s) show that the values near the lower limit, encourage bed temperatures around 750 C with higher carbon transformation efficiencies around 98%. However, this condition deteriorated the amorphous potential of silica present in the ash. An opposite behavior was evidenced at the upper limit of the excess air. This thermochemical process in this type of reactor shows the technical feasibility to valorize RH producing hot gases and an amorphous siliceous raw material.

A dynamic model for ethylene copolymerization in an industrial Fluidized-Bed Reactor (FBR) is developed to describe its behavior and calculate the properties of polyethylene. The presented model considers particle entrainment and polymerization reaction in two phases. Two-site kinetic and hydrodynamic models in combination, provide a comprehensive model for the gas phase fluidized-bed polyethylene production reactor. The governing moment and hydrodynamic differential equations were solved simultaneously and the results compared with a similar work, as well as industrial data. The dynamic model showed accurate results for predicting Polydispersity Index (PDI), Molecular Weight Distribution (MWD), reactor temperature and polymer production rate.

A two-phase model, which takes into account the change of the number of moles associated with the reaction, is used to investigate the possibility of using ftuidized bed configurations without and with selective metallic (or composite) membranes to conduct the catalytic reversible endothermic reaction for the dehydrogenation of ethylbenzene to styrene. This reaction is usually carried out industrially in adiabatic fixed beds. The effect of different design and operating parameters for the two fluidized bed configurations is investigated and the results are compared with those of an equivalent industrial fixed bed unit. It is shown that through the proper choice of design and operating parameters a considerable increase in the styrene production, over that of the industrial fixed bed unit, can be achieved.

The FBD-4 (¯uid bed dehydrogenation) technology for the dehydrogenation of isobutane to isobutene is described, including the scenario in which the development of this technology was decided and the scale-up procedure used. The paper is then particularly focused on the efforts to develop a reliable mathematical model for design and simulation of the¯uid bed reactor. # 0920-5861/99/$ ± see front matter # 1999 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 0 -5 8 6 1 ( 9 9 ) 0 0 0 8 0 -2

A study on gasification of empty fruit bunch (EFB), a waste of the palm oil industry, was investigated. The composition and particle size distribution of feedstock were determined and the thermal degradation behaviour was analysed by a thermogravimetric analysis (TGA). Then fluidized bed bench scale gasification unit was used to investigate the effect of the operating parameters on EFB air gasification namely reactor temperature in the range of 700–1000 °C, feedstock particle size in the range of 0.3–1.0 mm and equivalence ratio (ER) in the range of 0.15–0.35. The main gas species generated, as identified by a gas chromatography (GC), were H2, CO, CO2 and CH4. With temperature increasing from 700 °C to 1000 °C, the total gas yield was enhanced greatly and reached the maximum value (∼92 wt.%, on the raw biomass sample basis) at 1000 °C with big portions of H2 (38.02 vol.%) and CO (36.36 vol.%). Feedstock particle size showed an influence on the upgrading of H2, CO and CH4 yields. The feedstock particle size of 0.3–0.5 mm, was found to obtain a higher H2 yield (33.93 vol.%), and higher LHV of gas product (15.26 MJ/m3). Equivalence ratio (ER) showed a significant influence on the upgrading of hydrogen production and product distribution. The optimum ER (0.25) was found to attain a higher H2 yield (27.31 vol.%) at 850 °C. Due to the low efficiency of bench scale gasification unit the system needs to be scaling-up. The cost analysis for scale-up EFB gasification unit showed that the hydrogen supply cost is RM 6.70/kg EFB ($2.11/kg = $0.18/Nm3).

Bio-oil was produced at 450°C by fast pyrolysis in a continuous auger reactor. Four feed stocks were used: pine wood, pine bark, oak wood, and oak bark. After extensive characterization of the whole bio-oils and their pyrolytic lignin-rich ethyl acetate fractions by gas chromatography/mass spectrometry (GC/MS), gel permeation chromatography (GPC), calorific values, viscosity dependences on shear rates and temperatures, elemental analyses, 1 H and 13 C NMR spectroscopy, water analyses, and ash content, these bio-oils were shown to be comparable to bio-oils produced by fast pyrolysis in fluidized bed and vacuum pyrolysis processes. This finding suggests that portable auger reactors might be used to produce bio-oil at locations in forests to generate bio-oil on-site for transport of the less bulky bio-oil (versus raw biomass) to biorefineries or power generation units. The pyrolysis reported herein had lower heat transfer rates than those achieved in fluidized bed reactors, suggesting significant further improvements are possible. ; Steele, P. Pyrolysis of wood/biomassa critical review. , 20, 848-889.

For an installed silicon based solar cell panel, about 40% of the energy consumed producing the cell was used during production of the silicon feedstock. Reducing the energy consumption in this step is therefore crucial in order to minimize the energy payback time of installed capacity. The most promising alternative to the conventional methods is fluidized bed reactors (FBR). The development of FBR for the production of polysilicon is here reviewed. Through the last half century several research groups and companies have contributed to the development of such reactors to a point where the method is competitive on the terms given in today's marked. Most work within the field of research has been done by the industry and this has resulted in few articles and a substantial amount of patents on the topic. This article aims to summarize the development and to paint the complete picture on what concepts have been investigated, what challenges arose and where the development stands today.

Pyrolysis and gasification are two of the more promising utilization methods for the conversion of biomass toward a clean fuel source. To truly understand and model these processes requires detailed knowledge ranging from structural information of raw biomass, elemental composition, gas-phase reaction kinetics and mechanisms, and product distributions (both desired and undesired). The various analytical methods of biomass pyrolysis/gasification processing are discussed, including reactor types, analytical tools, and recent examples in the areas of (a) compositional analysis, (b) structural analysis, (c) reaction mechanisms, and (d) kinetic studies on biomass thermochemical processing.

A fluidized bed reactor (FBR) was designed and constructed for the delivery of reactive gases to particle surfaces to functionalize particles at large scale using atomic layer deposition (ALD). Nano-and micron-sized particles were effectively fluidized using an inert carrier gas assisted by mechanical agitation of the powder bed. The gas-solid contacting properties of fluidized bed reactors are beneficial for ALD surface reactions, while the frequent solid-solid collisions do not disrupt the self-limiting behavior of ALD reactant gases. Films can be deposited with monolayer control on individual particles of various substrate types, including metals, ceramics and polymers. In situ mass spectrometry was used for realtime monitoring of gaseous product(s) and reactants throughout the ALD reaction. Alumina (Al 2 O 3 ) ALD on particles demonstrates the process control capabilities of this unique, scalable configuration. The applications of Al 2 O 3 ALD films on particles are widely varying but typically involve core substrate surface passivation, which includes thermal oxidation resistance, photocatalytic activity mitigation and the fabrication of electrically insulative metal particles. Particle functionalization is achievable to nanoscale precision on a wide range of substrate types and sizes with minimal waste of costly ALD precursors and process time.

A mathematical model of biomass gasification in bubbling fluidized gasifier has been developed. It is a one-dimensional, two-phase (bubble and emulsion), two-zone (bottom dense bed and upper freeboard), steady state model. The model is based on global reaction kinetic, mass and energy balances and is capable of predicting temperature, solid hold ups and gas concentration along the reactor's major axis. The overall model has sub-models to deal with biomass pyrolysis, gasification, bed hydrodynamics, material classification and property calculation. A sub-model for tar generation and cracking is included in this study. The model is capable of dealing with wide variety of biomasses and fluidizing agents, i.e. air, oxygen, steam or a mix of these gases. Results show that during devolatilization step, gases release and mixing are sensitive and critical parameters. They have a strong influence on the overall performance of a gasifier. A comparison with experimental data from numerous literature works was done, which showed fairly good agreement. The model can be used to study and optimize the operation of bubbling fluidized bed gasifier. However, further validation with diverse data will help to fine-tune the model.

Polyethylene is the most common thermoplastic and used in a wide range of applications. There are various commercial technologies available to produce polyethylene. Gas fluidized bed polymerization is one of the later technology developed and is commonly employed in the production of linear-low density polyethylene (LLDPE) and high density polyethylene (HDPE). This paper reviews the historical development of fluidized bed polymerization technology as well as the development of catalyst from Ziegler-Natta catalyst to metallocene-based catalyst. A critical review of the challenges and opportunities from an operations view-point is presented.

A new model with comprehensive kinetics for propylene homopolymerization in fluidized bed reactors was developed to investigate the effect of mixing, operating conditions, kinetic and hydrodynamic parameters on the reactor performance as well as polymer properties. Presence of the particles in the bubbles and the excess gas in the emulsion phase was considered to improve the two-phase model, thus, considering the polymerization reaction to take place in both the bubble and emulsion phases. It was shown that in the practical range of superficial gas velocity and catalyst feed rate, the ratio of produced polymer in the bubble phase to the total production rate is roughly between 10% and 13%, which is a substantial amount and cannot be ignored. Simulation studies were carried out to compare the results of the improved two-phase, conventional well-mixed and constant bubble size models. The improved twophase and well mixed models predicted a narrower and safer window at the same running conditions compared with the constant bubble size model. The improved two-phase model showed close dynamic behavior to the conventional models at the beginning of polymerization, but starts to diverge with the evolution of time.

Although currently microalgae biomass is not considered as a sustainable feedstock for biofuel production, future developments of microalgae cultivation and harvest could make the commercial application of such fast-growing photosynthetic biomass economically and environmentally feasible. This article aims at reviewing thermochemical conversion of microalgae into bio-crude oil through pyrolysis and hydrothermal liquefaction technologies. Subsequently, possible solutions to overcome the constraints to achieve the sustainable conversion of microalgae biomass are discussed in detail. The drawbacks of bio-crude oil as a transportation fuel and the technologies required for its upgrading are highlighted. Currently, microalgae-derived bio-crude oil is inferior to biodiesel and diesel in terms of quality, thus cannot be used as a transportation or jet fuel. It requires catalytic upgrading steps and further processing, including durable and cost-effective catalysts with strong regenerative capabilities.

Biomass Hydrogen Olivine a b s t r a c t Air gasification of olive kernels in a 5 kW bench scale, bubbling fluidized bed gasifier, aimed at H 2 enrichment of the producer gas, was the target of this study. The effects of reactor temperature (T ¼ 750-850 C) and equivalence ratio (ER ¼ 0.2-0.4), representing the under stoichiometric amount of air inserted into the reactor to that necessary for complete combustion, on producer gas quality were determined. The experimental results revealed that producer gas H 2 content increased at the temperature of T ¼ 750 C and ER ¼ 0.2, resembling the high-temperature pyrolysis conditions that favour H 2 and CO production.

Simulation of a Fluidized Bed Reactor is carried out to find out the possible abatement of amount of fluorine and fluorides from gaseous effluents of Phosphatic Fertilizer Plant. Red-mud with small amount of coarse aluminium particles (approx. 760 microns) are used as bed materials. Bed hydrodynamics were studied to determine the proper fluidization conditions. Aspen Plus Simulation is used to study the effect of various parameters (i.e. temperature, pressure and composition of bed materials) on abatement of fluorides assuming chemical equilibrium where the total Gibbs energy of the system has its minimum value. The required conditions for maximum possible abatement of fluorine and fluorine bearing compounds from the industrial gaseous effluents are determined.

A mathematical model of biomass gasification in bubbling fluidized gasifier has been developed. It is a one-dimensional, two-phase (bubble and emulsion), two-zone (bottom dense bed and upper freeboard), steady state model. The model is based on global reaction kinetic, mass and energy balances and is capable of predicting temperature, solid hold ups and gas concentration along the reactor's major axis. The overall model has sub-models to deal with biomass pyrolysis, gasification, bed hydrodynamics, material classification and property calculation. A sub-model for tar generation and cracking is included in this study. The model is capable of dealing with wide variety of biomasses and fluidizing agents, i.e. air, oxygen, steam or a mix of these gases. Results show that during devolatilization step, gases release and mixing are sensitive and critical parameters. They have a strong influence on the overall performance of a gasifier. A comparison with experimental data from numerous literature works was done, which showed fairly good agreement. The model can be used to study and optimize the operation of bubbling fluidized bed gasifier. However, further validation with diverse data will help to fine-tune the model.

A general simulation program has been developed, with the aime of realizing an optimal representation of the various chemical schemes which can be carried out in fluidized bed reactors. Four classical models based on bubble dynamics have been modified so that the most complex chemical reactions can be treated, and to take into account the variations in gaseous flow which

Steady state operational data from a pilot scale circulating fluidized bed bioreactor (CFBBR) during biological treatment of landfill leachate, at empty bed contact times (EBCTs) of 0.49, and 0.41 d and volumetric nutrients loading rates of 2.2-2.6 kg COD/(m 3 d), 0.7-0.8 kg N/(m 3 d), and 0.014-0.016 kg P/(m 3 d), was used to calibrate and compare developed process models in BioWin ® and AQUIFAS ® . BioWin ® and AQUIFAS ® were both capable of predicting most of the performance parameters such as effluent TKN, NH 4 -N, NO 3 -N, TP, PO 4 -P, TSS, and VSS with an average percentage error (APE) of 0-20%. BioWin ® underpredicted the effluent BOD and SBOD values for various runs by 80% while AQUIFAS ® predicted effluent BOD and SBOD with an APE of 50%. Although both calibrated models, confirmed the advantages of the CFBBR technology in treating the leachate of high volumetric loading and low biomass yields due to the long solid retention time (SRT), both BioWin ® and AQUIFAS ® predicted the total biomass and SRT of CFBBR based on active biomass only, whereas in the CFBBR runs both active as well as inactive biomass accumulated.

Thermo catalytic decomposition (TCD) of methane using Ni-Cu-Al catalyst in a pilot scale fluidized bed is studied. The conventional method of catalyst preparation based on co-precipitation is compared versus an easier preparation method based on the fusing of the metallic nitrates. Catalysts prepared by both methods shown similar behavior. Fluidodynamic studies have shown that TCD can be carried out in a fluidized bed reactor without reactor clogging provided that a methane velocity of two times the minimum fluidization velocity is used. This high spacial velocity resulted in a reduction of the fraction of methane converted, but not in the quantity of carbon deposited per gram of catalyst. The optimum gas velocity should be chosen in terms of hydrogen production rates and fluidization quality. A semi-continuous fluidized bed installation has been started up and operated to produce at the scale of 60 l h −1 of hydrogen and 15 g h −1 of carbon nanofibers. ᭧

A series of experiments were conducted to compare the pore development in palm-shell and coconut-shell-based activated carbons produced under identical experimental conditions. Carbonization and activation processes were carried out at 850 °C using a fluidized bed reactor. Within ...

A circulating fluidized bed (CFB) is a gas-solid contactor in which solids are transported vertically in a riser by a high-velocity gas stream. CFB reactors are becoming increasingly attractive for conducting specific catalytic reactions. The catalytic oxidation of n-butane to maleic anhydride (MAN) has been simulated for a ao-m-high, 30-cm-diameter CFB to investigate the reactor performance under various operating conditions. The comprehensive simulation combines a core-annular hydrodynamic model of the CFB with a fixed bed reaction kinetics model. Reactor performance is evaluated in terms of n-butane conversions, product yields, and selectivity. The simulation can easily accommodate different reaction kinetics and therefore can be used to predict the performance of a CFB reactor for any catalytic process.

The biodegradation of waters polluted by some bisphenols, endowed with endocrine activity, has been studied by means of laccase or tyrosinase immobilized on polyacrylonitrile (PAN) beads. Bisphenol A (BPA), Bisphenol B (BPB), Bisphenol F (BPF) and Tetrachlorobisphenol A (TCBPA) have been used. The laccase-PAN beads system has been characterized as a function of pH, temperature and substrate concentration. The biochemical parameters so obtained have been compared with those of the free enzyme to evidence the modification induced by the immobilization process. Once characterized, the laccase-PAN beads have been employed in a fluidized bed reactor to determine for each of the four bisphenols the degradation rate constant (k); the s 50 , i.e., the time to obtain the 50% of degradation, and the removal efficiency (RE 90 ) after 90 min of enzyme treatment. The same parameters have been measured for each of the four pollutants with the same fluidized bed bioreactor loaded with tyrosinase-PAN beads. The internal comparison, i.e., in each of the two catalytic systems, has shown that both enzymes exhibit a removal efficiency in the following order BPF[BPA[BPB[TCBPA. The external comparison, i.e., the comparison between the two catalytic system, has shown that the catalytic power of laccase were higher than that of tyrosinase. The operational stability of both catalytic systems resulted excellent, since they maintained more than 80% of the initial activity after 30 days of work.

Sus domestica a b s t r a c t Utilizing large amounts of animal waste as a source of renewable energy has the potential to reduce its disposal problems and associated pollution issues. Gasification characteristics of the manure compost make it possible for low temperature gasification. In this paper, an energy efficient approach to hydrogen-rich syngas from manure compost is represented at relatively low temperature, around 600 C, in a continuous-feeding fluidized bed reactor.

A two-phase model is proposed for describing the behavior of a fluidized bed reactor used for polyethylene production. In the proposed model, the bed is divided into several sequential sections where flow of the gas is considered to be plug flow through the bubbles and perfectly mixed through the emulsion phase. Polymerization reactions occur not only in the emulsion phase but also in the bubble phase. Voidages of the emulsion and bubble phases are estimated from the dynamic two phase structure hydrodynamic model. The kinetic model employed in this study is based on the moment equations. The hydrodynamic and kinetic models are combined in order to develop a comprehensive model for gas-phase polyethylene reactor. The results of the model are compared with the experimental data in terms of molecular weight distribution and polydispersity of the produced polymer. A good agreement is observed between the model predictions and actual plant data. It has been shown that about 20% of the polymer is produced inside the bubble phase and as such cannot be neglected in modeling such reactors. ᭧

In order to contribute to better resource efficiency and industrial waste management leading to a sustainable production and consumption pattern new processes must be developed, which should be operated in such a way that waste production is reduced or avoided. Fluoride removal by precipitation generates huge amounts of a water rich sludge. Calcium fluoride is not recovered from the waste streams and it is not recycled due to the high water content and the low quality of the sludge. Crystallization process in a fluidized bed reactor (FBR) appears as an alternative technology to the conventional chemical precipitation process. In the crystallization process in a FBR silica sand is usually used as seed material, however silica is a deleterious impurity because it causes losses in the yield of HF and its content should be less than 1%. In this paper, granular calcite has been used as seed material in order to obtain synthetic calcium fluoride. According to the composition (CaF(2)>97%, SiO(2)<1%), the synthetic calcium fluoride from the crystallization process in a FBR is able to be recycled as raw material for the manufacture of hydrofluoric acid leading to a reduction of raw materials consumption. The crystallization process in a FBR to remove fluoride from industrial wastewaters contributes to an environmental friendly production, because it allows to reduce the waste production as well as to increase the recovery of materials.

Various methods of thermal shock testing are used by aircraft and industrial gas turbine engine (IGT) manufacturers to characterize new thermal barrier coating systems in the development stage as well as for quality control. The cyclic furnace oxidation test (FCT), widely used in aircraft applications, stresses the ceramic/bondcoat interface, predominantly through thermally grown oxide (TGO) growth stress. The jet engine thermal shock (JETS) test, derived from a burner rig test, creates a large thermal gradient across the thermal barrier coating (TBC), as well as thermomechanical stress at the interface. For IGT applications with long high-temperature exposure times, a combination of isothermal preoxidation and thermal shock testing in a fluidized bed reactor may better represent the actual engine conditions while both types of stress are present. A comparative evaluation of FCT, JETS, and a combined isothermal oxidation and fluidized bed thermal shock test has been conducted for selected ceramic/bondcoat systems. The results and the failure mechanisms as they relate to the TBC system are discussed. A recommendation on the test method of choice providing best discrimination between the thermal shock resistance of the ceramic layer, the ceramic/bondcoat interface, and even substrate related effects, is given.

Seven mixtures of coals, plastics and wood have been pelletized and fed into a pre-pilot scale fluidized bed gasifier in order to investigate the main aspects of the co-gasification of these materials. The main components of the obtained syngas (CO, H 2 , CO 2 , N 2 , CH 4 , C n H m ) were measured by means of on-line analyzers and a gas cromatograph. The performance of the gasifier was evaluated on the basis of syngas composition, carbon conversion efficiency, energy content of syngas, cold gas efficiency and yield of undesired by-products (tar and soot-like particulate). The results of a first series of experimental tests showed the effect of gas fluidizing velocity and that of equivalence ratio on the main performance parameters for a specific coal-plastics mixture. A second series of tests has been carried out by changing the mixture composition keeping fixed the gas velocity and equivalence ratio. The presence of wood and coal in the mixture with plastics contributed to reduce the tar production even though it is accompanied by a lower syngas specific energy.

ABSTRACTS 349 rated priority pollutants. Toward that end, the PIs have previously established the following data base of such technologies: 1) sodium perborate mediated oxidation applicable to a range of model compounds and to some priority pollutants; 2) the efficacy of mixed oxidation systems; 3) the general utility of appropriate ruthenium species as the catalytic contributor in mixed oxidation systems and; 4) the potential of sodium hypochlorite (household bleach) as the safe, cheap and efficient co-oxidant in a practical mixed oxidation system. The focus of the work in the current proposal is to define, develop and optimize a new oxidative degradation technology based on a sodium hypochlorite/ruthenium oxide mixed oxidation system. The work will include the following studies: 1) in-depth study with styrene to optimize the reaction conditions; 2) reaction survey of a range of structural class model compounds under the optimized conditions; 3) reaction survey of several representative unsaturated priority pollutants under the optimized conditions and; 4) investigation of the feasibility of using an inert-supported ruthenium species in the process.

This paper examines the effect of organic loading rate on the removal efficiency of COD and TOC anaerobic thermophilic fluidized bed reactor (AFBR) in the treatment of cutting-oil wastewater at different hydraulic retention time (HRT) conditions. The essays are development at laboratory scale using a porous support medium.

A predictive model was developed for the fully developed zone of a circulating fluidized bed (CFB) riser reactor operating in the fast fluidization regime that overcomes limitations of existing models. The model accounts for the upward flow of gas and solids in the core and downward flow of the two phases in the annulus. Additionally, a numerical solution methodology for the simulation of a riser reactor employing the hydrodynamic model was devised. A simulation was performed using the fast, main Claw reaction to demonstrate the effects of backmixing in the fast fluidization regime. It was found that the molar flow rates of the reactants leaving a fast fluidized CFB riser reactor were significantly higher than those leaving an identical reactor operating in the pneumatic transport regime.