Nonisothermal Kinetics Based on Two-Stage Scheme for Co-Drying of Biomass and Lignite
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This study investigates nonisothermal co-drying kinetics of two typical biomasses (cornstalk and red pine) with lignite in the presence of a nitrogen atmosphere using a thermal gravimetric analysis technique. The drying rate can be increased by either decreasing the blending ratio of biomass or increasing the heating rate. The activation energies of cornstalk/lignite blends and red pine/lignite blends in the two falling rate periods are less than that of their parent samples. In the first falling rate period, the dominant mechanisms of drying for lignite are described by the Avrami–Erofeev equation (n = 1.5), while the mechanisms for the cornstalk, red pine, and mixture samples are fitted to the Mample equation (n = 1.0). In the second falling rate period, the mechanisms are described by the Avrami–Erofeev equation (n = 1.5 or n = 2.0). The general kinetic compensation effect correlations are obtained for all samples within heating rates of 10–30°C/min. Significant synergistic interactions between the Chinese lignite and cornstalk or red pine are detected during co-drying.Keywords:
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In most studies of exposures to man-made mineral fibres both fibre number and total mass concentration have been measured, but, generally, correlations between these measures were found only for data pooled by plant or activity rather than for individual samples; also, there were differences between fibre types. Gravimetric measurements have practical advantages and suggestions have been made to approach MMMF exposure evaluation either on a dual gravimetric/fibre count basis or by use of a gravimetric screening test. This paper describes Danish experience in the derivation and performance of a gravimetric screening limit value (SLV) as against a ‘correct’ hygienic index which combines both respirable fibre and total mass concentrations. The system is considered to have many advantages, but the adopted SLV should be checked before use under new or changed conditions.
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The aim of this work is to study the suitability and limitations of a new gravimetric hydrogen evolution (HE) collection method for corrosion rate determination on pure Mg. This method, originally developed by Curioni [1], is based on the real-time weight measurement of the H 2 produced during dissolution and exhibits a higher accuracy level as well as better collection efficiency than the traditional volumetric method. The gravimetric HE collection method overcomes some of the limitations exhibited by the traditional volumetric HE method, where hydrogen gas tends to accumulate at the walls of the funnel and the burette, leading to a lower determination of the amount of H 2 produced and thus, an underestimation of the HE rate. The gravimetric HE collection method also exhibits good suitability for the study of Mg alloys with high corrosion resistance and for short experimental times, where the low levels of H 2 produced prevents reliable measurements of the amount of gas evolved by the volumetric HE collection method. The gravimetric HE collection method is also applicable for dynamic measurements, i.e. potentiodynamic and galvanodynamic polarizations. The gravimetric method was evaluated for the study of anodic HE on pure Mg (also termed Negative Difference Effect (NDE)), which is characteristic of Mg and its alloys when they are forced to dissolve at anodic potentials from the E corr . Possible artifacts and experimental limitations of the gravimetric experimental method will be discussed. [1] M. Curioni, The behaviour of magnesium during free corrosion and potentiodynamic polarization investigated by real-time hydrogen measurement and optical imaging, Electrochim. Acta 120 (2014) 284-292.
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Abstract A study of the kinetics of N 2 O decomposition on the surface of Fe 2 O 3 , Al 2 O 3 , and Fe 2 O 3 supported on Al 2 O 3 or Li‐doped Al 2 O 3 shows that Fe2O3/Al 2 O 3 is the most active catalyst.
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The present theories and experimental methods to evaluate the swelling behaviors by gravimetric measurement were experimentally tested for polyvinyl alcohol (PVA) films. It was found that the swelling behaviors and swelling kinetic parameters, such as diffusion exponent n, by gravimetric measurement may be greatly influenced by experimental procedures. In this pa- per, both the continuous (denoted as scheme A) and the separated (scheme B) experimental procedures of the gravimetric method to evaluate the swelling behaviors were presented and the difference between the two schemes were analyzed. The results suggest that the continuous diffusion of water molecules in films during gravimetric determination may be the key factor affecting the swelling behaviors. The advantages and disadvantages of the two schemes were discussed. It was concluded that an appropriate selection of experimental schemes is effective to extend the applicability range of gravimetric methodology and to increase the accuracy of gravimetric measurement.
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