Antonio Gutiérrez Lavín

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.

The regrowth of phytoplankton cultures after UV disinfection.

This study addresses how cultures of three phytoplankton species -Chaetoceros calcitrans, Chlorella autotrophica and Phaeocystis globosa - can recover from the effects of UV-C exposure if the cells are placed in a rich medium. Flow cytometry and pulse amplitude modulation (PAM) were used to determine cell recovery after UV treatment. The recovery of C. calcitrans was complete 9 days after treatment. For C. autotrophica, the recovery was noticeable 5 days after treatment. P. globosa only recovered if the UV dose did not exceed 7.3×10(5) μWs/cm(2). The recovery of the UV-treated cultures introduced to a regrowth medium, compared with the recovery of the irradiated cultures kept in their original environment, had two main characteristics: cell recovery was slower but was more efficient. This pattern of recovery has very important implications for real ballast water management systems because such systems discharge treated water into the environment.

Evolution of phytoplankton cultures after ultraviolet light treatment.

Introducing invasive species in new environments through ballast water is a specific problem of contamination and has recently become one of the main concerns of Maritime Organizations. Ultraviolet-C radiation (UV-C) is a technological alternative to prevent this maritime pollution. This study addresses the effect of UV-C on different phytoplankton cultures and also the ability to recover following exposure to damage. A UV-C low-pressure lamp irradiates the cultures. The distance from the source and the thickness of the layer prevent part of the energy from reaching the culture and the disinfective process is diminished. Some cultures such as Chlorella autotrophica and Chaetoceros calcitrans can easily recover from UV-C damage. However, Phaeocystis globosa does not have this ability. C. calcitrans forms cysts and exhibits two different behaviours depending on the dose applied.

Influence of physical properties of solid biomass fuels on the design and cost of storage installations

The aim of this work consists on determining biomass fuels properties and studying their relation with fixed and variable costs of stores and handling systems. To do that, dimensions (length and diameter), bulk density, particle density and durability of several brands and batches of wood pellets and briquettes were tested, according to international standards. Obtained results were compared with those in literature. Bulk density tests were applied for several other biomass fuels too, and later used to determinate which ones of all the biomass-fuels tested are economically more profitable for a typical transport/store system made of a screw conveyor and a concrete bunker silo.

High liquid holdup airlift tower loop reactor: I. Riser hydrodynamic characteristics

The hydrodynamics of high liquid holdup airlift reactors have not been widely studied. In this work we study the riser of a reactor of this type, focussing on the influence of the gas flow rate and the submergence ratio on various hydrodynamic parameters: liquid circulation velocity, gas holdup, and gas residence time in the liquid. A notable difference in reactor behavior is observed with a submergence ratio equal to unity and with a ratio lower than unity. Correlations for the parameters studied in different conditions, as several submergence ratios, are proposed, these are extrapolations of other equations proposed in the literature for airlift reactors. The reactor studied in this work can be thought of as an element of a great pool formed by multiple elements of similar flux type. The studied parameters are shown to be very important for subsequent hydrodynamic and mass transfer modeling of the reactor.

High liquid holdup airlift tower loop reactor : II. Downcomer hydrodynamic modeling

Hydrodynamics in the downcomer of a high liquid holdup airlift tower loop reactor, whose riser has been previously studied, is presented. A visual procedure with colorimetric tracers injected into the top part of the riser and monitored by means of a video camera system, for subsequent treatment of the obtained images, was used. The tracer front advance curves have suggested a compartmental model of three parameters to be used for physical transport processes. © 2000 Society of Chemical Industry

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.