Bettina Liebmann

Determination of glucose and ethanol in bioethanol production by near infrared spectroscopy and chemometrics.

The concentrations of glucose and ethanol in substrates from bioethanol processes have been modeled by near infrared (NIR) spectroscopy data. NIR spectra were acquired in the wavelength range of 1100-2300 nm by means of a transflectance probe for measurements in liquid samples. For building of regression models a genetic algorithm has been applied for variable selection, and partial least-squares (PLS) regression for creation of linear models. A realistic estimation of the prediction performance of the models was obtained by a repeated double cross-validation (rdCV). Reduced data sets with only 15 variables showed improved prediction qualities, in comparison with models containing 235 variables, particularly for the determination of the ethanol concentration in distillation residues (stillages). The squared correlation coefficient, R(2), between the concentrations obtained by HPLC analysis and the concentrations derived from NIR data (using 15 selected wavelengths, test set samples) was 0.999 for ethanol in stillage, and 0.977 for glucose in mash. The standard deviation of prediction errors, SEP, obtained from test set samples was 0.6 g L(-1) for ethanol (2% of the mean ethanol concentration), and 2.0 g L(-1) for glucose (9.6% of the mean glucose concentration).

Integration of the bio-ethanol process in a network of facilities for heat and power production from renewable sources using process simulation

Abstract The economic competitiveness of ethanol as a liquid fuel strongly depends on the amount of energy used during the production. To a sustainable production of fuel ethanol contributes also the use of energy from renewable sources. Process simulation is used to integrate a bio-ethanol plant in a network of facilities for heat and power production from residues of ethanol and feedstock production. Results show that depending on plant capacity and form of biogas utilization it is possible to cover heat demand using biogas produced from stillage of bioethanol fermentation. Partial combustion of straw from feedstock production even enables to cover the heat demand of small ethanol facilities.