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•Disorder of cellulosic H-bonds during pre-treatment developed amorphous Cellulose II.•EmimOAc pre-treatment reduced the activation energy of biomass pyrolysis.•Presence of amorphous ...Cellulose II in treated biomass enhanced dehydration reaction.•Enhanced dehydration of treated biomass during pyrolysis increased furans yield.•Cleavage of β-O-4 bonds of lignin during pre-treatment enhanced phenols yield.
Slow pyrolysis of regenerated cellulose-rich material (RCRM) and recovered lignin produced from imidazolium-based ionic liquid (IL) pre-treatment of sugarcane straw (SCS) was investigated employing a Thermogravimetric Analyser (TGA) instrument coupled with a Fourier-Transform Infrared (FTIR) spectroscopy. 1-ethyl-3-methylimidazolium acetate (EmimOAc) pre-treatment of SCS altered the hydrogen bonds of cellulose and produced amorphous Cellulose II structure in RCRM. FTIR spectroscopic analysis of liquid products showed that the IL pre-treatment increased the production of furans from the pyrolysis of RCRM, because the presence of amorphous Cellulose II in RCRM enhanced the dehydration reaction during pyrolysis. Moreover, the recovered lignin from IL pre-treatment enhanced the production of phenol-rich pyrolysis oil due to the cleavage of β-O-4 ether bonds of lignin during pre-treatment. Scanning electron microscope (SEM) analysis indicated highly porous structure of both RCRM and recovered lignin derived biochars. The kinetic analysis using a hybrid approach (a combination of model-fitting and model-free methods) indicated a reduction in the activation energy for both RCRM and recovered lignin pyrolysis. It is concluded that IL pre-treatment of lignocellulosic biomass followed by low-temperature pyrolysis can be an efficient route for biorefinery production.
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GEOZS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Drying kinetics is vital to optimize and predict the moisture content and drying rate when designing drying systems for new drug products. In this work, drying kinetics was studied for naproxen ...sodium drug formulation dried using microwave radiation by measuring the drug moisture content and drying rate. Ten semi-theoretical and empirical thin layer models were tested for their suitability in representing the drying kinetics data at different levels of microwave power. The experimental results showed that the extent of moisture removal increased with increasing microwave power output. It took 35, 24 and 8 minutes to remove 90% of the original moisture content at 30, 60 and 90 W, respectively. The drying rate increased steeply with an increase in time to reach maximum values of 4.7, 6.9 and 11.1 kg/m2.min at 30, 60, and 90 W, respectively and then decreased to reach a constant value. Among the mathematical models tested, logarithmic model provided the best fit in representing the drying kinetics data for all microwave power values. Two new empirical models developed using experimental moisture content and drying rate data could estimate these two parameters with higher accuracy as a function of drying time and microwave power.
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•Microwave radition was used to dry a new formulation of naproxen sodium drug.•Rapid and two fallingrate drying periods controlled the drying of naproxen sodium.•Logarithmic thin-layer model fits the experimental drying rate data closest.•Two new models were proposed for predicting the drying rate and moisture content.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The current work focuses on the comparison of renewable choline cation-based ionic liquids (ILs) with imidazolium cation-based ILs for their delignification performance. Choline cation-based ILs ...removed a higher percentage of lignin (78.1–83.7% vs. 51.4–64.5%) and hemicellulose (64.7–72.8% vs. 7.1–29.9%) from sugarcane straw pre-treatment compared to imidazolium cation-based ILs. This was mainly attributed to the presence of fewer alkyl group and extra –OH group in choline cation. In general, ILs pre-treatment significantly increased the volatile matter and reduced fixed carbon in regenerated cellulose-rich material. Higher content of cellulose and higher crystallinity in the case of choline-based ILs enhanced the production of furfural and levoglucosenone from the pyrolysis of regenerated cellulose rich material. On the contrary, the presence of higher content of amorphous cellulose from imidazolium-based ILs, particularly 1-ethyl-3-methylimidazolium acetate produced γ-butyrolactone. Therefore, ILs pre-treatment can be favourable for the selective production of platform chemicals via pyrolysis route.
Graphic abstract
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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•COD solubilisation follows the same trend regardless of concentration and temperature.•There are similar decreasing trends of yield stress and infinite viscosity.•The increase of ...sCOD is proportional to decrease of yield stress and infinite viscosity.•The change of rheology and composition of WAS & digested sludge follows the same pattern.
The rheological properties of sludge are key parameters in the design and optimisation of wastewater treatment processes. However, these properties are irreversibly altered when the sludge is exposed to heat (e.g. either passing through heat exchangers of anaerobic digesters or during thermal pre-treatment process before digesters). Literature showed that thermal pre-treatment of waste activated sludge (WAS) solubilises particulate organic matter in sludge and increases the biodegradability of WAS in anaerobic digesters.
This paper reports the similarity between the kinetic of rheological enhancements due to thermal treatment and the rate of organic matter solubilisation in the WAS when it is subjected to cyclic thermal treatment between 20 and 80°C up to 1h. This work observed the evolution of rheological characteristics and soluble oxygen demand (sCOD) of 3.5–9.9wt.% WAS at different temperatures and for different thermal histories (1h thermal treatment at 50, 60, 70 and 80°C).
Results showed that, the rate of yield stress and infinite viscosity reductions due to thermal treatment (for 1h treatment at 50, 60, 70 and 80°C) were linearly proportional to the rate of solubilisation of organic matter. Because similar results were observed in the literature with digested sludge, these results confirmed that rheological measurement (e.g. infinite viscosity and yield stress) can be used to predict the level of solubilisation of organic matter in any type of sludge when it is exposed to thermal treatment. Vice versa, the rate of COD changes can be used as an indicator of the rate of rheological changes.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•Analysis of ultrasound waves propagation in gas-liquid media using CFD simulation.•Analysis of mass transfer intensification under ultrasound irradiation.•Analysis of the effects of acoustic ...streaming, fluid flow pattern, turbulence on KLa.
This paper aims at investigating the influence of acoustic streaming induced by low-frequency (24kHz) ultrasound irradiation on mass transfer in a two-phase system. The main objective is to discuss the possible mass transfer improvements under ultrasound irradiation. Three analyses were conducted: i) experimental analysis of mass transfer under ultrasound irradiation; ii) comparative analysis between the results of the ultrasound assisted mass transfer with that obtained from mechanically stirring; and iii) computational analysis of the systems using 3D CFD simulation. In the experimental part, the interactive effects of liquid rheological properties, ultrasound power and superficial gas velocity on mass transfer were investigated in two different sonicators. The results were then compared with that of mechanical stirring. In the computational part, the results were illustrated as a function of acoustic streaming behaviour, fluid flow pattern, gas/liquid volume fraction and turbulence in the two-phase system and finally the mass transfer coefficient was specified. It was found that additional turbulence created by ultrasound played the most important role on intensifying the mass transfer phenomena compared to that in stirred vessel. Furthermore, long residence time which depends on geometrical parameters is another key for mass transfer. The results obtained in the present study would help researchers understand the role of ultrasound as an energy source and acoustic streaming as one of the most important of ultrasound waves on intensifying gas-liquid mass transfer in a two-phase system and can be a breakthrough in the design procedure as no similar studies were found in the existing literature.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The delignification of sugarcane straw (SCS) was investigated using 1-ethyl-3-methylimidazolium acetate, EmimOAc, varying three process parameters such as temperature, residence time, and stirring ...rate. The maximum degree of delignification was around 63.9% at 90 °C for a stirring rate of 1400 rpm and a residence time of 5 h. The 2
3
full factorial statistical model was well-fitted with the experimental results. Among the 26 solid-liquid reaction mechanisms studied in this study, Zhuravlev, Lesokhin, and Templeman diffusion (i.e., shrinking core/product layer) model was found to be the most suitable model for describing the delignification mechanism of SCS using EmimOAc. When compared with other process parameters, higher temperatures produced low crystalline and low thermally stable recovered cellulose-rich material with high porosity and BET surface area due to higher degree of crystalline cellulose I to amorphous cellulose II transformation. The recovered lignin was of low molecular structure with high content of phenolic OH
−
groups and syringyl units. The recovery of EmimOAc was > 85% with no structural changes.
Graphical Abstract
Crystallization is an experimental phenomenon that does not always depend on predicted data for efficient processing. It, therefore, becomes important to conduct experiments in the seeded or unseeded ...crystallization process to gain insight into the growth kinetic parameters. The knowledge of the process and kinetic parameters is proved useful in developing strategies for the optimal design of crystallizers and in control of crystal size distribution. A differential scanning calorimeter (DSC) was used to perform isothermal growth experiments for seeded crystallization, and the kinetics was evaluated using a de-supersaturation curve. In order to get the de-supersaturation curve, the DSC heat flow signal was used to measure and quantify the mass change of seeds during the crystal growth process as a function of time at a particular temperature. Experiments were performed at temperatures ranging from 10 to 40 °C in sealed DSC pans. The growth order g was calculated from the isothermal experiments at varying temperatures, and the mass growth rate coefficient
K
g
, linear growth rate coefficient
k
g
, mass rate of crystal growth
R
G
and activation energy
E
a
of benzoic acid in the ethanol–water binary solvent were estimated from growth order g. The kinetic parameters were compared with the data obtained using online measurement techniques and found to be in good agreement. The present work establishes the reliability of calorimetric transformation studies for estimating growth kinetics using a small amount of sample in a very short period, at higher temperatures and pressures.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
•Solid–liquid mass transfer was studied at high solids concentrations.•Specific impeller power consumption is the lowest for solids concentration of 0.2 (v/v).•Solid–liquid mass transfer coefficient ...(kSL) is the highest between solids concentration of 0.15 and 0.20 (v/v).•A mathematical correlation is proposed to estimate kSL with increasing solids concentration.
The effect of solids concentration on specific impeller power consumption and solid–liquid mass transfer coefficient was investigated in a 0.2m diameter baffled agitated vessel with standard six-bladed Rushton turbine for solids concentration up to 0.40 (v/v). It was found that the increase of solids concentration significantly increases the mass transfer coefficient up to an optimum solids concentration and decreases thereafter when the system is operated at a just-suspended condition. The increase in mass transfer coefficient with an increase of solid concentrations is mainly due to the increase in Njs (critical impeller speed) with increasing solids concentration, thereby leading to an upsurge of turbulence around the particles. The solids concentration at which the highest mass transfer coefficient is obtained is designated as the effective solids concentration. In a geometrically similar 0.3m diameter tank, the trends in impeller energy efficiency and solid–liquid mass transfer coefficient values with increasing solids concentration are similar. The experimental data are satisfactorily correlated using the concept of the Kolmogoroff's theory of isotropic turbulence to develop an equation to estimate the solid–liquid mass transfer coefficient in agitated vessels.
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GEOZS, IJS, IMTLJ, IZUM, KILJ, KISLJ, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
•Mixing of a sludge simulant with submerged jets studied using flow visualization techniques.•Different flow regimes discovered and analysed using imaging tools.•Phenomena characterising individual ...regimes and transitions between them discussed.
We study the flow regimes that develop when a non-Newtonian fluid that simulates municipal wastewater sludge is agitated in a mixing vessel using a submerged, downwards-pointing, recirculating jet and report a series of empirical scaling laws that emerge. A stream extracted from the vessel itself feeds the nozzle that discharges the jet via a pump. We observe that the volume that remains unperturbed (inactive volume, Vi) decreases steadily over time and when plotted against a normalised time-scale Nt=(Q̇/VT)t where Q̇ is the recirculation rate, VT the total volume of the vessel and t the elapsed time, the quantity (Vi/VT) follows distinct trends that can be related to the apparent flow patterns within the mixing vessel. We study these domains experimentally using analytical video images to establish the differences between the flow behaviours that develop in these domains. Our experiments demonstrate that (Vi/VT) decreases slowly at first in the initial regime (Regime 1 and 2) and then rapidly in the terminal regime (Regime 3) with a rate almost an order of magnitude larger than the initial decay. While the rate of decay in the initial regime depends on the rheological properties of the fluid, the rate becomes independent of the same as the terminal regime is reached. Our experiments show that the transition between the initial and the terminal regimes can be a complex one and that the initial regime can persist for a remarkably long period of time. We provide empirical evidence to prove that that these regimes are affected by the rheology of the fluid and the principal operating condition, the injection velocity, when the geometrical factors are held constant.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
A novel approach is proposed for the numerical evaluation of scale thickness and its distribution in a mixing tank. Whereas a majority of the available literature on scale buildup focuses on the ...application of chemical antiscalants, few works have been devoted to the prevention of scale formation through the proper design and operation of stirred vessels. The methodology proposed in the current study consists of two major phases: (1) identifying an accelerated process to grow scales on the walls of a laboratory reactor and (2) analyzing the grown scale physically. These objectives were achieved through the fabrication of a reactor that could be disassembled and the scanning of the reactor’s surface using a coordinate measuring machine (CMM). The proposed approach was used to study the effects of liquid flow velocity and experiment duration on the patterns of scale formed both qualitatively and quantitatively.
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IJS, KILJ, NUK, PNG, UL, UM
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