The public defens of Jan Skvaril´s doctoral thesis in Energy and Environmental Engineering
Doctoral thesis and Licentiate seminars
The public defens of Jan Skvaril´s doctoral thesis in Energy and Environmental Engineering will take place at Mälardalen University.
The doctoral thesis has serial number 224
The title of the thesis is “Near-Infrared Spectroscopy and Extractive Probe Sampling for Biomass and Combustion Characterization”.
The faculty examiner is Professor Anestis Kalfas, Aristotle University of Thessaloniki; and the examining committee consists of Professor Torbjörn Lestander, Swedish University of Agricultural Sciences; Professor Brigitte Leblon, University of New Brunswick; Professor Emeritus Dan Loyd, Linköping University.
Reserve: Adjunct Professor Carl-Fredrik Lindberg, MDH
Biomass is an abundant, renewable and carbon-neutral feedstock material. It plays an important role in the modern industrialized world that is characterized by ever-growing energy and material demand, and population growth.
As a feedstock material biomass has highly variable properties which make its use challenging. It can be converted to more valuable energy forms and important end-products through a variety of conversion processes. Biomass conversion is represented mostly by thermo-chemical processes (e.g., combustion), chemical and biochemical processes (e.g., pulping), and physiochemical processes. This thesis focuses on addressing important issues related to two biomass conversion technologies: combustion and pulping.
Experimental investigations were carried out on a full-scale biomass-fired bubbling fluidized bed boiler. The results showed that the combustion process is very complicated with high levels of process variability during the course of the experimental campaign. The asymmetric course of combustion reactions was evident and could be explained by the unbalanced fuel feed. Increased levels of unburned carbon monoxide were detected in the vicinity of the boiler walls which increases the risk of carbon-induced wall corrosion.
The near-infrared spectroscopy (NIRS) technique is an optical and non-destructive method able to characterize solid and liquid materials. A literature study was performed covering research trends on applications of NIRS for biomass energy conversion. From the literature examined, it can be seen that NIRS demonstrates an enormous potential to provide fast and reliable property information for heterogeneous feedstocks and end-products. Moreover, NIRS proves its ability to directly monitor processes producing or processing biofuels.
Experimental work, signal processing, and mathematical modeling were performed focused on the utilization of the NIRS technique for measuring different properties of biomass feedstock material. The developed models were able to predict heating value, ash content and moisture content, i.e. characteristics that are fundamental in thermochemical conversion. The investigated biofuel mixtures were consisting of: stem wood chips, forest residue chips, bark, peat, and sawdust. The NIRS technique was further able to determine the amount of glass in artificial wood/glass mixtures, which is of interest in waste incineration. An experimental NIRS study focusing on the influence of different parameters on lignin quantification was also performed. Spectral data were acquired on moving woodchips as opposed to earlier works that focused on static samples. Models were developed for the prediction of acid soluble and acid insoluble lignin. Data acquisition on moving woodchips was found to increase the representativeness of the spectral measurements leading to improvements in model performance.
Overall, the present work demonstrates the possibility to develop NIRS-based soft-sensors for characterization of biomass properties. The implementation of such sensors on a process line enables feed-forward process control, diagnostics and optimization.