New type of dry substances content meter using microwaves for application in biogas plants

Nacke, Thomas; Brückner, Kathleen; Göller, Arndt; Kaufhold, Sebastian; Nakos, Xenia; Noack, Stephan; Stöber, Heinrich; Beckmann, D.

doi:10.1007/s00216-005-0105-7

Cited by 10 publications

(7 citation statements)

References 3 publications

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“…Multivariant data analysis was shown to be a suitable approach for detecting organic dry mass in biogas plants [48]. The data have been reduced to a combined parameter derived from a narrow spectrum between 2.2 and 2.6 GHz which is in first approximation the reflection coefficient at 2.45 GHz.…”

Section: Dry Matter In Slurries and Mashesmentioning

confidence: 99%

Bioimpedance: A Review for Food Processing

Pliquett

2010

Food Eng. Rev.

111

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Electrical measurement is a simple innocuous tool for material characterization. Unlike for instance milk or dairy products, the majority of naturally grown food is composed of cells. The cells of meat or vegetables are surrounded by an insulating membrane, while the cytosol and the extracellular fluids are electrolytes. Despite the high permittivity of water, electrolytes behave like ohmic resistors up to hundreds of MHz. In contrast, membranes form capacitive elements due to their high resistance. The typical time constant for charging cell membranes is of the order of a microsecond. Thus, cells influence the impedance in a frequency range up to several MHz. At higher frequencies, the cytosolic content, i.e., macromolecules, gives rise to characteristic relaxation processes. Using the impedance in the microwave range where water dipoles show a distinct dispersion, humidity of dried matter can be addressed. Moreover, with sensitive measurement setup and proper models, one can determine the dry content in mashes and slurries as well. Several quality standards correlate well with the permeability of the membranes or the total water content. Because of the comparatively simple measurement of the electrical impedance together with advanced mathematical modeling, it is often a good approach in quality assessment of agricultural products. The change in conductivity of a culture medium contains information about the metabolism of incubated cells. Using specific culture media and time-lapse conductivity monitoring allows a high sensitivity and selectivity in microbial detection. Because the electrical impedance is very sensitive to the permeability of cell membranes, it is a great choice for the assessment of changes due to high voltage application. Today, many attempts to use impedance measurement in food technology show fast success in research but fail in practice. The reason is often an overestimation especially of the selectivity while underestimating the uncertainties in a harsh environment of a food-processing plant. Established, however, is the use of robust process measurement systems and the limitation of impedance measurement to applications with highly significant outcome or as supplemental measurement in a multiparameter approach. This review introduces the basics of bioimpedance measurement, points to sources of uncertainty, and presents successful applications in food industry.

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Section: Dry Matter In Slurries and Mashesmentioning

confidence: 99%

Bioimpedance: A Review for Food Processing

Pliquett

2010

Food Eng. Rev.

111

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“…The use of microwave technology yields a non contact method for monitoring the substrate within tanks of biotechnological plants [24]. Using an economic, narrow bandwidth method with sophisticated post processing (principal component analysis), it was shown that the determination of total organic mass is accurate enough for controlling a biogas plant.…”

Section: Measurement Of Content Of Organic Dry Substancesmentioning

confidence: 99%

Electricity and biology

Pliquett

2008

2008 11th International Biennial Baltic Electronics Conference

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Life and electricity are closely connected. All membranes, first the plasma membrane but also intracellular membrane systems, are electrically charged. Virtually all functions of cells and tissues are somehow controlled by the electric field within membranes. It influences the conformation of membrane residual proteins and thereby the functionality of the membrane. Ionic channels in membranes can be controlled by several gating variables resulting in a variable conductivity of the membrane.Therefore, active and passive electrical properties of cells and tissue are well suited for monitoring purposes.Besides the assessment of electrical properties, they can be manipulated by the application of electric field which results either in a change of the functionality of the cells or even in cell killing.

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“…Even more critical, there are few methods available for online monitoring of total solids. However, Luck et al [19] and Nacke, et al [20], reported on-line monitoring of solids in biogas plant using microwaves and NIR spectroscopy, respectively. On the other hand, one of the limitations in non-invasive NIR methodology is the need to construct optical aperture in the process line.…”

Section: Dry Matter (Ts) Monitoringmentioning

confidence: 99%

“…The optical aperture is liable to fouling by microbial growth and may reduce effective process monitoring over a long period of time [4,18]. Also, in both studies [19,20] optimal validation with independent test set samples were lacking which is a cause of critical concern for future prediction purpose [21]. 6…”

Section: Dry Matter (Ts) Monitoringmentioning

confidence: 99%

Acoustic chemometric prediction of total solids in bioslurry: A full-scale feasibility study for on-line biogas process monitoring

Ihunegbo

Madsen

Esbensen

et al. 2012

Chemometrics and Intelligent Laboratory Systems

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Dry matter is an important process control parameter in the bioconversion application field. Acoustic chemometrics, as a Process Analytical Technology (PAT) modality for quantitative characterisation of dry matter in complex bioslurry systems (biogas fermentation), has not been successful despite several earlier dedicated attempts. A fullscale feasibility study based on standard addition experiments involving natural plant biomass was conducted using multivariate calibration (Partial Least Squares Regression, PLS-R) of acoustic signatures against dry matter content (total solids, TS). Prediction performance of the optimised process implementation was evaluated using independent test set validation, with estimates of accuracy (slope of predicted vs. reference values) and precision (squared correlation coefficient, r 2 ) of 0.94 and 0.97 respectively, with RMSEP of 0.32 % w/w (RMSEP rel = 3.86 %) in the range of 5.8 -10.8 % w/w dry matter. Based on these excellent prediction performance measures, it is concluded that acoustic chemometrics has come of age as a full grown PAT approach for on-line monitoring of dry matter (TS) in complex bioslurry, with a promising application potential in other biomass processing industries as well.

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New type of dry substances content meter using microwaves for application in biogas plants

Cited by 10 publications

References 3 publications

Bioimpedance: A Review for Food Processing

Bioimpedance: A Review for Food Processing

Electricity and biology

Acoustic chemometric prediction of total solids in bioslurry: A full-scale feasibility study for on-line biogas process monitoring

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