Thermochemical processes in ash transformation of fast growing broadleaf trees

The overall aim of this PhD project is to propose efficient and sustainable thermochemical conversion processes based on fast-growing broadleaved species. More specifically, the detailed objectives are to determine the influence of plant species, tissue types, forest management, harvesting, and feedstock handling factors on: 

1. the composition and concentrations of the ash forming/inorganic matter in the feedstock
2. the ash transformation and -behavior (e.g., ash composition, -melting, slagging, agglomeration, particle formation) in combustion-, gasification- and pyrolysis processes. 

Based on the generated new scientific knowledge from i) and ii) suitable uses of fast-growing broadleaved species in mixes with other biomass fuels or as additives to other fuels and optimal thermal process conditions will be suggested.  

The influence of the previously mentioned production parameters on the feedstock characteristics will be determined and compared with currently used biomass-based feedstocks. Analyses include the elemental composition of ash forming main and trace elements. Based on the fuel composition and supplementary thermochemical model calculations, the fast-growing broadleaved species' ash transformation characteristics in pyrolysis, gasification, and combustion will initially be screened and discussed. Secondly, the detailed ash transformation and -behavior will be determined for the different feedstocks in different lab-scale setups mimicking the various thermochemical conversion techniques. After that, several interesting feedstock assortments and their mixtures will be selected and proposed for further evaluation by full-scale experiments in different industrial-scale thermal conversion units. 

This project (Project 10) will specifically focus on the ash forming/inorganic matter in the feedstock and their effect on the thermochemical conversion process, and the sister project in work package 3 (Project 12) will focus on the feedstock's organic fractions (CHNO) and thermophysical properties and their effect on the conversion process.