Performance analysis of RF dielectric models for density-independent estimation of moisture content in sorghum

Performance analysis of RF dielectric models for density-independent estimation of moisture content in sorghum

Precise on-line and bulk-density independent monitoring of moisture content in processing grain into flour is important information to improve the milling process efficiency and to obtain a high quality final product. However, since feed moisture content is difficult to measure, it is nearly never a...

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Bibliographic Details
Published in:Powder technology Vol. 246; pp. 369 - 378
Main Authors: Moura, E.E., Berbert, P.A., Berbert-Molina, M.A., Oliveira, M.T.R.
Format: Journal Article
Language:English
Published: Amsterdam Elsevier B.V 01-09-2013
Elsevier
Subjects:
Applied sciences
bulk density
Chemical engineering
dielectric properties
Exact sciences and technology
flour
grain sorghum
Loss factor
mass flow
milling
milling industry
Miscellaneous
Moisture
monitoring
Permittivity
prediction
Radiofrequency
Solid-solid systems
Sorghum
water content
Loss factor
Sorghum
Radiofrequency
Permittivity
Moisture
Bulk density
Correlation
On line
Bias
Dielectric properties
Prediction
Calibration
Modeling
Mass flow rate
Statistical parameter
Surveillance
Correlation analysis
Water content
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Summary:Precise on-line and bulk-density independent monitoring of moisture content in processing grain into flour is important information to improve the milling process efficiency and to obtain a high quality final product. However, since feed moisture content is difficult to measure, it is nearly never available in the milling industry. This work addresses a reliable solution to reduce the deleterious effect of the mass flow rate on the estimation of grain sorghum moisture content, a method which is based on the high correlation between grain moisture content and two of its dielectric properties, i.e., relative permittivity ε′, and loss factor ε″. Thus, the object of this paper was to analyse the effectiveness of three dielectric models for estimation of sorghum moisture content at excitation frequencies in the range from 75kHz to 5MHz, for moisture contents from 13 to 23% w.b., and bulk densities ranging from 575 to 818kgm−3. Goodness of fit between experimental and predicted values of moisture content was based on the following statistical parameters: coefficient of multiple determination, standard error of calibration, worst-case error, root mean squared error, mean absolute percentage error, mean bias, fit index, and reduced chi-squared. Residual plot analysis and the principle of parsimony were also considered in the selection of the most effective dielectric model. The model based on the measurement of ε′ and ln(ε″) at 5MHz gave the best predictions of sorghum moisture content for the conditions studied. [Display omitted] •On-line sensing of flowing grain moisture is important to improve milling efficiency.•As feed mc is difficult to measure, it is seldom available in the milling industry.•A reliable solution is the use of density-independent dielectric functions.•The effectiveness of three dielectric models for sorghum mc measurement was assessed.•Measurement of ε′ and ln(ε″) at 5 MHz gave the best predictions for sorghum mc.
Bibliography:http://dx.doi.org/10.1016/j.powtec.2013.04.030
ISSN:0032-5910
1873-328X
DOI:10.1016/j.powtec.2013.04.030