Consuelo Pizarro

Characterization of Spanish biomass wastes for energy use.

Energy plays an important role in the worlds present and future. The best way to absorb the huge increase in energy demands is through diversification. In this context biomass appears as an attractive source for a number of environmental, economical, political and social reasons. There are several techniques used to obtain energy from biomass. Among these techniques, the most commonly used throughout the world is a thermo-chemical process to obtain heat. To optimize the combustion process in adequate reactors, a comprehensive study of the characterization of biomass fuel properties is needed, which includes proximate analysis (determination of moisture, ash, volatile and fixed carbon content), ultimate analysis (C, H, N, S and O composition) and calorimetry, focusing on biomass fuels obtained in Spain.

Biomass proximate analysis using thermogravimetry.

This work proposes a 25 min-last thermogravimetric method as a tool to determine biomass samples proximate analysis data (moisture, ash, volatile matter and fixed carbon contents) just by direct measure of weight changes on each samples TG chart. Compared with international standards commonly used to that aim, TG is a faster and easier to develop technique. Obtained results were satisfactory, with AEE under 6% for moisture and volatile matter, close to 10% for fixed carbon determination and AAD of 1.6 points for ash content.

Determination of kinetic parameters for biomass combustion.

The aim of this work is to provide a wide database of kinetic data for the most common biomass by thermogravimetric analysis (TGA) and differential thermogravimetry (DTG). Due to the characteristic parameters of DTG curves, a two-stage reaction model is proposed and the kinetic parameters obtained from model-based methods with energy activation values for first and second stages in the range 1.75·10(4)-1.55·10(5)J/mol and 1.62·10(4)-2.37·10(5)J/mol, respectively. However, it has been found that Flynn-Wall-Ozawa and Kissinger-Akahira-Sunose model-free methods are not suitable to determine the kinetic parameters of biomass combustion since the assumptions of these two methods were not accomplished in the full range of the combustion process.

Novel method for holocellulose analysis of non-woody biomass wastes

Compositional analysis of non-woody biomass is quite important to determine its possible applications. However, current standard methods developed for woody biomass compositional analysis have been revealed to be unsuitable when applied to non-woody biomass. Therefore, a novel and less-time consuming modified method which enables for a proper isolation of holocellulose in non-woody biomass samples while increasing lignin degradation has been developed. The novel method mainly consists in a treatment with sodium chlorite and glacial acetic acid at boiling point, which precludes changes in the holocellulose crystallinity degree or losses of carbohydrates, as shown by DSC, XRPD, and HPLC analysis. It was successfully applied to the determination of the structural components of 10 different non-woody biomass samples. Also, its use revealed that non-woody biomass belongs to LHC and LCH groups in the biomass structural composition ternary diagram, which are completely different than the ones the woody biomass belongs to.

COMPARISON BETWEEN OXIDATIVE AND NON-OXIDATIVE TORREFACTION PRETREATMENT AS ALTERNATIVES TO ENHANCE PROPERTIES OF BIOMASS

Oxidative and non-oxidative torrefaction pretreatments are the most employed in order to enhance some properties of biomass such as hygroscopicity, low energy density, or poor grindability and so biomass could be a more competitive renewable energy source. The aim of this paper is to compare oxidative and non-oxidative torrefaction processes applying to a pine wood sample. Torrefaction in the range of temperatures 200–250oC was conducted in a tube furnace reactor and proximate and ultimate analyses and heating value determination were carried out in order to characterize the torrefied samples. Torrefaction kinetics were obtained at three different temperatures using a thermogravimetric analyser. Both mass and energy yields in oxidative cases were lower as torrefaction temperature was increased compared to non-oxidative treatment. Heating value data of oxidative option were slightly lower than those of non-oxidative one were, although they were higher than the heating value of raw biomass. According to the proximate analysis, the moisture content decreased from 7.63% in raw biomass to 3.46% and 3.15% in pine torrefied at 250°C in oxidizing and inert atmospheres, respectively. H/C and O/C ratios decrease was more drastic for oxidative torrefaction than for non-oxidative one. In addition, the van Krevelen diagram shows that oxidative torrefaction is more interesting than non-oxidative alternative, this circumstance suggests that any optimizing criterion has to take into account at least three variables, including ultimate analysis and mass and energy yields.