Isothermal kinetics based on two-periods scheme for co-drying of biomass and lignite

Thermal drying behavior of the municipal sewage sludge in nitrogen atmosphere was explored using a thermal analysis technique under isothermal and nonisothermal drying conditions. The Midilli model, MR ¼ expðÀkt n Þ þ bt, was the best suitable for predicting both the isothermal and nonisothermal drying behavior of the sewage sludge with the highest R 2 . The isothermal drying apparent activation energies of the first falling rate period and the second falling rate period were 18.03 and 11.87 kJ mol -1 , respectively. The nonisothermal drying apparent activation energies of sewage sludge were from 33.61 to 47.37 kJ mol -1 in the first falling rate period and from 20.47 to 33.43 kJ mol -1 in the second falling rate period, respectively. In two falling rate periods, the dominant mechanism functions for the isothermal drying were identical, À lnð1 À aÞ. The dominant mechanism functions for the first falling rate period and the second falling rate period in the nonisothermal drying were described by ½À lnð1 À aÞ 1=2 and ½À lnð1 À aÞ 1=3 , respectively.

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“…Similar result was shown in the Ref. [36]. Figure 4 illustrates the TG and DTG curves of the sewage sludge at different heating rates.…”

Section: Resultssupporting

confidence: 85%

A comparison of isothermal with nonisothermal drying kinetics of municipal sewage sludge

Zhang

Chen

2015

J Therm Anal Calorim

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“…The ultimate analysis for 139 the lignite samples(Liu et al, 2013) were also presented inTable 1. Proximate and ultimate analyses of lignite .…”

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confidence: 99%

Thin-layer drying kinetics of lignite during hot air forced convection

Chen

2015

Chemical Engineering Research and Design

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“…The g( ) represents the mechanism function. α 0 dα g(α) = = kt f α (14) As shown in Table 5, several kinetics equations corresponded to different forms of mechanism function f( ) & g( ) [17,21,31] could be substituted into Equation (14) to calculate the experimental data.…”

Section: Kinetics Analysis Of the Drying Processesmentioning

confidence: 99%

“…From the activation energy determined from the dewatering kinetics, the drainage of water is the dominating process even during secondary consolidation [16] . Liu et al experimentally determined the co-drying kinetics of biomass with lignite and found that the activation energy of the pure Bermuda grass and red pine were higher than those of the grass/lignite and pine/lignite blends, respectively [17] . For high moisture content matrixes such as foods, liquid diffusion is supposed to dominate in the relatively fast decreasing rate stage, while vapor diffusion should be the main mechanism of moisture transportation in the relatively slow decreasing rate stage [18] .…”

Section: Introductionmentioning

confidence: 99%

Removal behaviors of moisture in raw lignite and moisturized coal and their dewatering kinetics analysis

et al. 2016

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In order to investigate the dewatering kinetics and mechanism of low rank coal, the dewatering behaviors of a Chinese lignite and its moisturized sample (prepared from dewatered coal moisturized under relative humidity of 75% at 303 K for 48 h) in nitrogen and the temperature range of 333-433 K were tested. Physical structure changes of raw coal, moisturized coal before and after drying were determined. The results indicate that drying process of lignite could be divided into four stages, which are increasing rate stage, constant rate stage, relatively fast decreasing rate stage and relatively slow decreasing rate stage. Jander model and First order kinetics model are favorite to describe the relatively fast decreasing rate stage and relatively slow decreasing rate stage, respectively, and the corresponding dewatering mechanism equations are y= 1/3 2 [1-(1-α)] and y= -ln(1-α) . The effective diffusion coefficients and diffusion activation energy were calculated by Fick's second law. The diffusion activation energy of the dewatering stages, related to the relatively fast and slow decreasing rate stages, were 35.80 kJ/mol, 40.75 kJ/mol for raw coal and 27.80 kJ/mol, 37.34 kJ/mol for moisturized coal, respectively. The effective Downloaded by [University of Cambridge] at 17:16 04 June 20162 diffusion coefficient was significantly affected by drying temperature through the pore structure change of coal when other drying operation parameters were fixed. These prove that the forms of re-adsorbed water are not entirely the same as that in raw lignite, in which the former is relatively simple and the latter is more complex.

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Isothermal kinetics based on two-periods scheme for co-drying of biomass and lignite

Cited by 20 publications

References 42 publications

A comparison of isothermal with nonisothermal drying kinetics of municipal sewage sludge

A comparison of isothermal with nonisothermal drying kinetics of municipal sewage sludge

Thin-layer drying kinetics of lignite during hot air forced convection

Removal behaviors of moisture in raw lignite and moisturized coal and their dewatering kinetics analysis

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