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Activated carbon (AC) was prepared from furfural residue (FR) in a horizontal tube reactor under a carbon dioxide atmosphere comparing one- and two-step activation methods. Considerable differences were observed between ACs produced from these two methods in microscopic morphology, structural properties, organic structure, and crystallinity. It showed that the AC obtained by one-step activation (800 oC, 20 min, K2CO3: FR = 0.5:1) exhibited microporous and alkaline surface characteristics, and achieved the highest iodine value of 1305.7 mg/g and BET surface area 2083.6 m2/g. While, for the two-step method, the iodine value was 1004.9 mg/g and the BET surface area was only 726.3 m2/g. Furthermore, one-step activation obtained a higher yield of high-quality AC in a shorter activation time than the two-step method. The adsorption data fitted well with the Redlich-Peterson isotherm model and reached the highest value of 1761.1 mg/g, while the adsorption kinetics agreed well with the pseudo-second-order model.

This paper investigates the equilibrium performance of CaO hydration and CaCO3/Ca(OH)2 co-calcination in calcium-looping processes. A novel lime hydration configuration is proposed, introducing saturated steam as the reactivating reagent and direct-heat-removal medium. The proposed hydrator generates a substantial amount of superheated steam, used elsewhere as required. The slaked lime and limestone are calcined simultaneously in a methane-concentrated oxy-fuel calciner. The equilibrium performance of the co-calciner is studied at different reactor temperatures, operating pressures, solid/gas feed ratios and feed compositions. A correlation is proposed which estimates the required gaseous feed composition for autothermal, coke-free and complete sorbent regeneration using this novel technology.

This paper presents a steady-state simulation of sorbent-enhanced steam methane reforming in turbulent fluidized bed reactors. The effects of different operating conditions are assessed, including ...

Biomass gasification is one of the primary thermal conversion processes where fluidized bed reactors are often used to produce syngas with low heating values. However, there has not yet been an effective model to predict gasification yield with broad applicability. In this study, machine learning was adopted to realize the prediction of syngas compositions and lower heating values (LHV) using various lignocellulosic biomass feedstocks at a wide range of operating conditions. Three machine learning techniques, i.e., Random Forest (RF), Support Vector Machine (SVM) and Artificial Neural Network (ANN) were adopted after determining hyperparameters optimization. Pearson correlation and permutation importance were used for the sensitivity analysis. RF and ANN were found to have high prediction accuracy with R2 and RMSE results (RF: R2=0.809-0.946, RMSE=1.39-11.54%; ANN: R2=0.565-0.924, RMSE=1.46-10.56%). Monte Carlo filtering (MCF) was integrated into the three machine learning algorithms to forecast the desired products by predicting the important features of the operating conditions and biomass characteristics. Considering the desired H2/CO > 1.1 and LHV > 5.86 MJ/m3, the RF-MCF was a more suitable approach with R2=0.791-0.902 for H2, CO and LHV features. The machine learning approach can be widely adapted in various scenarios predicting output features as well as MCF for finding the significant variables for optimization.

Thermogravimetric analysis was performed to differentiate between the thermal and thermo-catalytic decomposition behaviour and kinetics of switchgrass (SG) pyrolysis and catalytic pyrolysis using bentonite or clinoptilolite. Silica sand was tested as an inert material with a thermal conductivity close to bentonite. Using a three-parallel reaction mechanism, it is shown that bentonite and clinoptilolite significantly increased the conversion percentage of all three pseudo-components, while the major difference was found for pseudo-lignin. Silica sand significantly increased the conversion of pseudo-hemicellulose only. Addition of catalysts increased the conversion of pseudo-lignin by 43 and 36% compared to SG and sand, respectively. The lowest activation energy value of pseudo-lignin was found for 30Bento which was lower by 29 and 25% than SG and sand, respectively. Based on subsequent study using microwave catalytic pyrolysis, it was observed that lignin decomposition was promoted by clinoptilolite and the phenolic compounds particularly the alkylated phenols in bio-oil product were increased by 49% higher than SG, which are primarily derived from lignin. The results obtained from the two-step kinetic model confirmed the speculation based on one-step 3-components kinetics that catalysts are mostly responsible for promoting the catalytic cracking of vapours released from lignin decomposition at high pyrolysis temperatures.

This paper studied the catalytic effects of mixtures of different catalysts (i.e., K3PO4 “KP”, Bentonite “Bento” and Clinoptilolite “Clino”) on biomass catalytic pyrolysis compared to the single catalyst under microwave heating and thermogravimetric analyzer (TGA). Since some catalysts can promote microwave absorption while others show promising catalytic effects, it is possible to use mixtures of catalysts to improve high microwave heating rate and simultaneously catalyze biomass pyrolysis reactions. 10K3PO4/10Bentonite (10 wt.%KP+10 wt.%Bento) catalyst mixture increased the mass loss rate by 85% and 45% at 100 and 25 °C/min, respectively, compared to switchgrass without catalyst. The highest microwave heating rates for torrefaction (110–260 °C) and pyrolysis stages (260–400 °C) were found for the catalyst mixtures, with the highest being achieved by 10KP/10Bento. It was also found that the catalyst mixtures affected the type of coke deposited on catalyst surfaces during pyrolysis, which plays an important role on determining the microwave heating rate under microwave catalytic pyrolysis by affecting the dielectric properties of the bed material and then microwave absorption. Oxygenated-coke deposited on catalyst surfaces reduces the microwave heating rate markedly, while graphitic-coke increases the microwave heating rate considerably. Finally, catalyst combinations improved the catalytic performance significantly and reduced the catalyst loads which in turn will reduce the production cost of bio-oil and biochar from microwave-assisted catalytic pyrolysis.

The attrition of binary mixtures of iron powder, as a representative oxygen carrier, and limestone, as a CO2 sorbent, was investigated to examine the interactions of two different solid species. An air-jet apparatus based on ASTM D5757, with several improvements, was used to test particle attrition for various times (3, 6 and 12 h), temperatures (20, 250 and 500 °C), gas flow rates (6, 8 and 10 LPM) and particle mixture compositions (Iron:Limestone mass ratios 1:0, 0.75:0.25, 0.5:0.5, 0.25:0.75 and 0:1). Attrition was affected by the fluidization velocity in relation to the minimum fluidization velocities of the two species, and the mixture mass ratio. High temperature increased the generation of iron fines, while reducing the production of limestone fines. As expected, increasing the air flow rate led to the generation of more fines of both iron and limestone.

The combination of limestone calcination, catalytic methane reforming, and combustion in a membrane reactor is simulated as a possible means to achieve autothermal and hydrogen-producing sorbent re...

11 figures, 3 tables.-- Supplementary information available., The attrition behaviour of several promising oxygen carriers tested in Chemical Looping Combustion (CLC) units has been evaluated using an air-jet apparatus based on ASTM D5757 at 20 and 800 °C. Results were evaluated to determine a general testing procedure that allows estimating the adequacy at working temperature of a potential oxygen carrier. For both fresh and used oxygen carriers, attrition was lower when the temperature of the Air Jet attrition Index (AJI) test was increased. Thus, tests with potential oxygen carriers must be performed close to the temperature they are planned to be used to obtain reliable information. Results indicated that used oxygen carriers with AJI value at hot conditions between 1 and 2% showed long lifetimes under continuous CLC operation., This work was supported by the Spanish National Research Council (CSIC) through the international collaboration project i-LINK+ 1225. The authors would also thank the support of the European Regional Development Fund (ERDF) under the program “Programa Operativo FEDER Aragón 2014-2020 - Construyendo Europa desde Aragón: Proyecto BiosinCO2 (LMP180_18)” and of the ENE2017-89473-R AEI/FEDER, UE. T. Mendiara thanks for the “Ramón y Cajal” post-doctoral contract awarded by the Spanish Ministry of Economy and Competitiveness.

Pb, Ni, and Co are among the most toxic heavy metals that pose direct risks to humans and biota. There are no published studies on biochars produced at low temperatures (i.e., 300 °C), which possess high sorption capacity for heavy metal remediation and reclamation of contaminated sandy soils. This research studied the effect of catalytic microwave pyrolysis of switchgrass (SG) using bentonite and K3PO4 to produce biochar at low temperature (300 °C) with high sorption capacity for reducing the phytotoxicity of heavy metals, and investigated the synergistic effects of catalyst mixture on biochar sorption capacity. The quality of the biochars was examined in terms of their impacts on plant growth, reducing phytotoxicity and uptake of heavy metals in sandy soil spiked with Pb, Ni, and Co. All catalysts increased the micropore surface area and cation-exchange capacity of biochars, and resulted in biochars rich in plant nutrients, which not only decreased heavy metal phytotoxicity, but also boosted plant growth in the spiked soil by up to 140% compared to the sample without biochar. By mixing bentonite and K3PO4 with SG during microwave pyrolysis, the efficacy of biochar in reducing phytotoxicity and heavy metals uptake was further enhanced because of the highest micropore surface area (402 m2/g), moderate contents of Ca, Mg, K, and Fe for ion-exchange and moderate concentration of phosphorus for the formation of insoluble heavy metal compounds. Generally, the biochar created at 300 °C (300-30KP) showed similar performance to the biochar created at 400 °C (400-30KP) in terms of reducing heavy metal bioavailability.

International audience; The spatial distribution of solid particles is a key factor affecting the performance of fluidized bed reactors. Non-invasive techniques including radioactive particle tracking (RPT) and positron emission particle tracking (PEPT) are deployed to measure the solids distribution. Different methods to calibrate the particle tracking measurements have been developed to quantify mean solids concentration. In this paper, gas-solid flows in a traveling fluidized bed are simulated with CFD-DEM and the behavior of different particles, including bulk sand particles and tracer particles are investigated. The simulated hydrodynamics are compared with experimental measurements. Analyses are carried out to derive the mean solids concentration from the tracer particle data. Different calibration approaches are examined, and the simple calibration method is verified. It is shown that the mean solids concentration can be measured reliably using representative tracer particles. The experimental RPT data are then revisited with the new calibration method which yields more realistic results.

This study's aim was to compare biochar and steam activated biochar functionalized with iron for removal of selenium as selenate from solutions also containing nitrate and sulfate. The Fe-biochar composites were made impregnating iron (ferric nitrate) onto regular biochar (RB) and steam activated biochar (SAB), forming the Fe-biochar composites FeRB and FeSAB. Iron oxyhydroxide deposits were observed on the surface of FeRB using Raman spectroscopy analysis, but not on the FeSAB surface. Unmodified biochar samples did not remove selenium, as Se(VI), from solution, whereas FeRB and FeSAB recovered 8.3 mg-Se⋅g-composite

In a liquid-solid fluidized bed crystallization system (having particles of different sizes), two opposite processes (classification and dispersion) influence overall particle size distribution. Interactions between these processes make designing crystallizers challenging, as the solid crystals within the bed exhibit some degree of mixing. Therefore, a better understanding of bed expansion and particle mixing/segregation is required to design fluidized bed crystallizers. In this study, a numerical investigation of the hydrodynamics of liquid-solid fluidized beds of polydisperse struvite crystals was thoroughly performed for the first time. This study also tested and validated three established empirical drag law correlations used to explain momentum exchange between solid and liquid phases. Wen and Yu (1966) and Gidaspow (1994) drag law models showed greater predictive power in terms of pressure drop and voidage in the fluidized beds of multi-particle systems. The simulated bed expansion behavior of different sizes of struvite crystals was found to be consistent with experimental results. At steady state, six different size groups of struvite studied in this investigation were found to be classified according to their sizes with limited intermixing between successive layers.

This paper investigates the effect of calcination temperature and duration on the cyclic CO2 capture performance of natural lime-based sorbents. Tests showed that increasing calcination temperature considerably reduced the sorbent reactivity over the first few calcination-carbonation cycles. No significant variation in performance was observed when a sorbent remained at the calcination temperature after completing limestone decomposition. On the other hand, incomplete limestone calcination significantly altered the sorbent cyclic utilization and CO2 carrying capacity. A semi-empirical method is proposed to estimate the fast reaction-controlled carbonation extent at different reaction cycles, calcination extents and temperatures. This method is shown to work well for two different naturally-derived limestones exposed to different calcination conditions.

A unique indirect steam gasification system for biomass has been developed and tested. The unit features a bubbling bed gasifier equipped with a “sore thumb” and central standpipe, which circulate a mixture of bed material and char through a U-bend to a riser in which char combustion occurs. Re-circulated silica sand from the riser is returned to the bubbling bed through a trickle valve at sufficiently high temperatures to drive biomass gasification. Factors which govern re-circulation of solids are explored and pressure profiles demonstrated. Gasification tests using wood pellets fed at 10–15 kg/h showed that syngas with heating value of about 12 MJ/m3 and nitrogen contents

In this study, blends of biodiesel and softwood derived fast pyrolysis oil (FPO) were produced, characterized, and evaluated for thermodynamic and emission performance in a single cylinder research engine. FPO was supplied from an in-house fluidized bed reactor as well as a commercial source. Separate FPO-biodiesel blends from both FPO sources were prepared using initial volumetric ratios of 80:20 and 60:40 (biodiesel:FPO, by volume). After blending, mixing, and a 24 h settling period, two layers formed and the top, biodiesel-rich layers containing about 5 and 10 vol% FPO were decanted and characterized on the basis of a thermogravimetric analysis, viscosity, acid number, water content, elemental analysis, and heating value. Significant decreases in viscosity, acidity, and water content from the original FPO validated blending as means of extracting compounds suitable for use as fuels from pyrolytic liquids in biodiesel. A single cylinder, common rail, direct injection diesel engine was used to analyze the combustion performance of the FPO fuel blends against neat diesel and biodiesel. Fuel performance was characterized on the basis of a thermodynamic combustion analysis, as well as corresponding exhaust emission measurements for CO 2 , CO, unburned hydrocarbons, particulate matter, and NOx. Engine testing revealed similar indicated efficiencies for biodiesel and diesel at all considered engine operating modes, while blend fuels showed indicated efficiencies between 75 and 95% of diesel values. In general, FPO fuels exhibited increased ignition delays and shorter combustion durations with greater FPO blend concentrations, though this could be partially compensated for using a pilot injection strategy. The longer ignition delays of the blend fuels resulted in overly lean regions of the cylinder, which produced largely premixed combustion events contributing to brake specific CO and uHC emissions up to 1.5 and 3.5 greater than diesel, respectively. Specific PM emissions were 41–62% lower for blend fuels than diesel. Both blends of in-house FPO showed similar PM emission performance, however at higher concentration than low blend commercial fuel.

The gas velocity interval for initiating gas fluidization of binary mixtures of Geldart type B particles has been thoroughly investigated experimentally and theoretically by Formisani et al. (2008–2014). The same approach has now been applied in our laboratory to liquid fluidization of binary macro-solids. Experimental results for water fluidization in a 190.5 mm diameter column of initially well mixed packed beds, consisting of different volumetric fractions of 1.91 mm and 4.54 mm glass spheres of density 2510 kg/m3, are well predicted by the methods of Formisani et al., whether the equations are based on random-dense voidages as practiced by that group, or based on random-loose voidages as commonly used for monocomponent solids. This article is protected by copyright. All rights reserved

A transportable fluidization column, operating under identical conditions at three different locations, was employed to compare three experimental solids flux measurement techniques for hydrodynamic characterization of gas-fluidized beds. This paper compares measurements of solids mass and momentum flux obtained by radioactive particle tracking at the Ecole Polytechnique, positron emission particle tracking at University of Birmingham, and borescopic high speed particle image velocimetry at PSRI, carried out with FCC particles of mean diameter 107 μm. These techniques provided broadly similar time-average solids flux profiles, but there were significant quantitative differences. Analysis of the results, focusing on the fundamentals of each measurement technique, provides valuable insights into the reasons for the discrepancies. The results also add to a unique hydrodynamic database for validation of CFD and other models.

Climate change is often tackled via a two-pronged approach of behaviour change and technological advancement. Policy studies and social sciences generally take ownership of influencing behaviours, while natural sciences and engineering tackle generating newer, more efficient technologies. Fusion of these methodologies is severely lacking. Engineers are uniquely situated to contribute to positive environmental action in both technological and behavioural realms. This article explores the psychological mindset of engineers as they make decisions to dissect factors that undermine sustainable behaviour. The Theory of Planned Behaviour, Multi-Criteria Decision Analysis and the Health Belief Model are applied to engineering decision making to develop a methodology for engineers to modify their behaviour to consistently make more sustainable choices, and in turn, assist others by making actions towards sustainability more convenient.

Transdisciplinary engineering curricula prepare future engineers with a holistic understanding of complex real-world problems, and the ability to tackle these problems with knowledge and skills in both engineering and non-engineering areas. What are transdisciplinary skills in the engineering education context? What learning activities can we design and implement to develop students’ transdisciplinary skills in the first-year engineering program? How can we assess transdisciplinary skills and evaluate the instructional effectiveness of these learning activities?The current study is an initial attempt to explore these questions. We introduce a conceptual framework ofusing systems thinking, empathy and metacognition asproxy indicators of transdisciplinary skills, and presentthe learning activities we have designed to developstudent competencies in these areas. In addition, wepropose an evaluation approach that includes a surveyinstrument and formative learning assessment, with which we investigate the relationships among empathy, systems thinking, and metacognitive skills in the context ofengineering education.

International audience; Particle tracking methods using emitted radiation are attractive for following motion in opaque systems such as granular materials. Leading examples are Positron Emission Particle Tracking (PEPT) and Radioactive Particle Tracking (RPT). The application of such techniques sometimes requires the use of tracer particles which differ in size, density and/or shape from the particles of interest. This study investigates the extent to which such differences affect the result of the study by using the open source MFIX-DEM software to model particle motion in the travelling fluidized bed experiments. The results are compared with previously reported experimental studies using both PEPT and RPT. Consistent numerical results were obtained for both PEPT and RPT tracer particles. In determining averaged velocities using such techniques, there is a choice to be made between averaging velocities of particles crossing a virtual plane over a period of time (the "face-average" approach) or those passing through a defined volume over time (the "volume-average" approach). The differences between results obtained with these two approaches are shown to be significant in this case, for both computation and experiment.

A jet attrition model is developed to predict the evolution of the particle size distribution in fluidized beds. This model predicts changes in particle size distribution due to impact attrition in the jet region as a function of operating parameters – temperature, particle impact velocity and time. The model provides good agreement with experimental results for iron and hematite as oxygen carriers, with limestone and lime as CO2 sorbent at temperatures from 20 to 800 °C and jet velocities from 59 to 221 m/s. It is found that fragmentation, abrasion, and material fatigue over the attrition duration must be considered. Two fitting parameters considering fatigue by material properties and repeated collisions are applied in this model, with their values determined based on nonlinear least squares regression following the evolution of the particle size distribution.

This study's aim was to compare biochar and steam activated biochar functionalized with iron for removal of selenium as selenate from solutions also containing nitrate and sulfate. The Fe-biochar composites were made impregnating iron (ferric nitrate) onto regular biochar (RB) and steam activated biochar (SAB), forming the Fe-biochar composites FeRB and FeSAB. Iron oxyhydroxide deposits were observed on the surface of FeRB using Raman spectroscopy analysis, but not on the FeSAB surface. Unmodified biochar samples did not remove selenium, as Se(VI), from solution, whereas FeRB and FeSAB recovered 8.3 mg-Se⋅g-composite−1 and 5.9 mg-Se⋅g-composite−1, respectively. Higher Se uptake was achieved at higher Fe-loads and lower acetone:biochar ratio, to a maximum of 17.3 mg-Se⋅g-composite−1 (FeRB). Washing after Fe-impregnation using deionized water diminished nitrate and Fe-leaching from the Fe-biochar composites while removing selenium. Se(VI) and sulfate uptake were observed when washed composites were tested in the presence of possible competing ions at environmentally relevant concentrations ([Se]t=0 = 1.01 ± 0.03 mg⋅L−1; [N–NO3-]t=0 = 40.2 ± 0.2 mg⋅L−1; and [SO42−]t=0 = 496 ± 25 mg⋅L−1). One of the possible mechanisms of removal might be the complexation of Se with the iron oxyhydroxide deposits (goethite and hematite) found on the FeRB surface.

Engineered biochars produced from microwave-assisted catalytic pyrolysis of switchgrass have been evaluated in terms of their ability on improving water holding capacity (WHC), cation exchange capacity (CEC) and fertility of loamy sand soil. The addition of K3PO4, clinoptilolite and/or bentonite as catalysts during the pyrolysis process increased biochar surface area and plant nutrient contents. Adding biochar produced with 10wt.% K3PO4+10 wt.% clinoptilolite as catalysts to the soil at 2wt% load increased soil WHC by 98% and 57% compared to the treatments without biochar (control) and with 10wt.% clinoptilolite, respectively. Synergistic effects on increased soil WHC were manifested for biochars produced from combinations of two additives compared to single additive, which may be the result of increased biochar microporosity due to increased microwave heating rate. Biochar produced from microwave catalytic pyrolysis was more efficient in increasing the soil WHC due to its high porosity in comparison with the biochar produced from conventional pyrolysis at the same conditions. The increases in soil CEC varied widely compared to the control soil, ranging from 17 to 220% for the treatments with biochars produced with 10wt% clinoptilolite at 400°C, and 30wt% K3PO4 at 300°C, respectively. Strong positive correlations also exist among soil WHC with CEC and biochar micropore area. Biochar from microwave-assisted catalytic pyrolysis appears to be a novel approach for producing biochar with high sorption affinity and high CEC. These catalysts remaining in the biochar product would provide essential nutrients for the growth of bioenergy and food crops.

The novel “travelling fluidized bed” (TFB), operated under identical conditions, was deployed to compare alternate experimental measurement techniques for the investigation of solid motion in gas-fluidized beds operating in the square-nosed slugging regime. Measurements of particle velocity obtained by radioactive particle tracking (RPT — non-invasive at the Ecole Polytechnique de Montreal), positron emission particle tracking (PEPT — non-invasive at University of Birmingham), optical fibre probes (invasive at UBC) and borescopic high speed particle image velocimetry (invasive at PSRI) are compared for sand particles of mean diameter of 292 μm. Significant differences between the time-average radial profiles of particle velocity are observed in many cases. The results provide valuable insights into the merits and challenges of advanced particle velocity measurement techniques.

Activated biochar (i.e., a by-product of biomass pyrolysis) is developed as a renewable, low-cost, and promising carbon-based electrode for capacitive deionization (CDI) of NaCl and ZnCl 2 solutions. High surface area biochar samples (i.e., between 971 and 1675 m 2 g −1 ) are prepared with three types of tailored porous structure: (a) predominately microporous (87% of total pore volume), (b) mesoporous (72% of total pore volume), and (c) a combination of both structures. The effect of the different porous structures, including also the sub-nanometer pore size ranges, on the electrosorption of Na + and Zn 2+ is studied by electrochemical techniques (i.e., cyclic voltammetry, galvanostatic charge/discharge, and batch-mode electrosorption) complemented by surface structural and compositional analysis. For NaCl removal, all samples showed promising capacity (i.e., up to 5.39 mg NaCl g −1 ) and durability through four consecutive adsorption/regeneration cycles. In case of ZnCl 2 on the other hand, the microporous sample experienced considerable drop in removal capacity (>75% drop) from cycle nr. 1 to 4. Interestingly, the sample with mostly mesoporous structure showed the highest removal capacity and durability for Zn 2+ removal. These results emphasize the importance of tailoring the porous structure of the biochar electrode material as a function of the specific size of adsorbate ions to improve the CDI performance.

This study reveals a novel method to tailor the micro- and meso-porous structures of activated biochar by exploiting the interaction between pre-carbonization drying conditions and carbonization temperature in KOH activation. Biochar samples were mixed with concentrated KOH and then dried under air or nitrogen for various periods of time (0–280 h) followed by carbonization at 475, 675 or 875 °C. It is confirmed that by manipulating drying conditions and carbonization temperatures, the KOH activated biochar can have a predominantly microporous, mesoporous or a combined (micro/meso) porous structure. The surface area, micropore and mesopore volumes tailored between: 488–2670 m2 g−1, 0.04–0.72 cm3 g−1, and 0.05–1.70 cm3 g−1, respectively. The mechanism of porosity development was investigated by FTIR analysis suggesting conversion of KOH to K2CO3 due to different drying conditions as a major role in tailoring the structure. The application of activated biochar with tailored porosity was investigated for Electric Double Layer adsorption of NaCl/NaOH to be employed in water treatment (capacitive deionization) or energy storage (supercapacitor) processes. The majorly microporous activated biochar (N2-dried activated at 675 °C) showed promising capacitances between 220 and 245 F g−1. Addition of mesoporous structure resulted in capacitances between 182 and 240 F g−1 with significantly reduced electrode resistance and improved capacitive behavior as evidenced by Impedance Spectroscopy and Galvanostatic Charge/Discharge tests.