Giulio Allesina

Biodiesel and electrical power production through vegetable oil extraction and byproducts gasification: Modeling of the system

Aim of this work is to introduce an alternative to the standard biodiesel production chain, presenting an innovative in situ system. It is based on the chemical conversion of vegetable oil from oleaginous crops in synergy with the gasification of the protein cake disposed by the seed press. The syngas from the gasifier is here used to produce electrical power while part of it is converted into methanol. The methanol is finally used to transform the vegetable oil into biodiesel. Through a coupled use of ASPEN PLUS(TM) and MATLAB(TM) codes, a rapeseed, soy and sunflower rotation, with a duration of three year, was simulated considering 15ha of soil. This surface resulted sufficient to feed a 7kWel power plant. Simulation outputs proven the system to be self-sustainable. In addition, economical NPV of the investment is presented. Finally the environmental, economical and social advantages related to this approach are discussed.

Modeling and investigation of the channeling phenomenon in downdraft stratified gasifers.

Downdraft stratified gasifiers seem to be the reactors which are most influenced by loading conditions. Moreover, the larger the reactor is, the higher the possibility to stumble across a channeling phenomenon. This high sensitivity is due to the limited thickness and superficial placement of the flaming pyrolysis layer coupled with the necessity to keep all the zones parallel for a correct running of this kind of gasifier. This study was aimed at modeling and investigating the channeling phenomenon generated by loading condition variations on a 250-kWe nominal power gasification power plant. The experimental campaign showed great variations in most of the plant outputs. These phenomena were modeled on two modified mathematical models obtained from literature. The results of the models confirmed the capability of this approach to predict the channeling phenomena and its dependency on the loading method.

An experimental analysis of a stand-alone standing-wave thermoacoustic refrigerator

AbstractIn the last years, the thermoacoustic phenomena had intensified the scientific community’s interest due to its implications in thermodynamics, heat transfer, and acoustic matters that make possible the conversion between sound and heat. This work is aimed at exploring the Russell-Weibull refrigerator, analyzing the behavior of the different parts in order to achieve a good level of thermal separation, together with the capability of working as stand-alone. Special attention was given to all those parts that need to be designed properly with explanation of the physics that ruled them, such as sound generator, woofer box, stack, and tube insulation. In the second part of the work, the results obtained are discussed, consistently showing that, if some expedients are adopted, this simple refrigerator can achieve a temperature difference of 24°C. The design choices concerning materials and geometries are shown to be of great influence on the device behavior.

Combined effects of LED lights and chicken manure on Neochloris oleoabundans growth

In this study a photobioreactor prototype is presented for the culture growth of microalgae model organism Neochloris oleoabundans by using chicken manure waste as feedstock along with the optimum combination of led light wavelengths and light intensity. Particularly interesting results are observed on the strains fed by chicken manure medium under the proper combination of red and blue LED light illumination, the microalgal growth resulted comparable with the strains fed by the costly commercial microalgal growth medium (BG 11 medium). Cell concentration, optical density, growth rate, cell size, total lipid and photosynthetic pigment content have been monitored during a time-course experiment. The data suggest that there are difficulties due to white light diffusion into the dark chicken medium, which leads to a generally lower intensity scattered along all wavelengths; blue or combined red and blue lights resulted in a higher irradiation density, affecting microalgae cell growth.

Uses of a Water-Algae-Photo-Bio-Scrubber for Syngas Upgrading and Purification

Aim of this work is to try to put together the two worlds of syngas filtering and syngas upgrading trough the use of a water-algae water photobio-scrubber. The system studied consists of a 10 kWel downdraft gasifier provided with a water scrubber where the syngas is bubbled in a solution of water, nutrients, algae and artificial light (. The heat provided by the syngas keeps the scrubber to the proper temperature where tars are condensed and algae can grow at proper rate. At the same time the CO2 content in the gas can be, in part, converted into biomass by the algae. From the scrubber it is disposed a multi-phase liquid composed of water, biomass, tars and char. The first analysis carried out in this work consisted in a two phases process of the gas. First, in the gasification system, part of the gas was derived into a simple water scrubber where all the flows where measured and the temperature was kept constant at 30 °C. Then the water obtained in such a way was used as basis for algae grown in lab conditions. Results shown the capability of such a system to be used in existing gasification facilities.

Energy and economical comparison of possible cultures for a total-integrated on-field biodiesel production

This work is aimed at investigating the energy conversion effectiveness and the economical advantages of a total integrated solution for on-field biodiesel and electrical energy production. The system proposed here is based on the synergy of four sub-systems: a seed press for oil production, a downdraft gasifier, a biodiesel conversion plant and a Solid Oxide Fuel Cell (SOFC). Two possible culture rotations, suggested by literature review, were analyzed here from economical and energy balance points of view. Both the rotations were composed of oleaginous crops only, therefore the seeds collected from the different cultures were pressed, then the protein cake produced in the process was gasified in the downdraft reactor. The gasification process was modeled here, and its output suggested that, for a precise number of hectares, the syngas obtained through the cake gasification was enough for producing methanol required for oil-biodiesel conversion and feeding a 10-kW SOFC. The purge line in the methanol reactor was used in the SOFC as well. The system was simulated using ASPEN PLUSTM and MATLABTM codes. Results of the SOFC and gasifier models underlined the capability of the fuel cell to work with this particular system, furthermore the whole system analysis suggested that the surface required for sustainability of the processes is a function of the rotation choice. In both cases little surfaces ranging from 11 to 21 hectares were found to be enough for system self-sustainability with a ROI under 7 years in all the operating conditions analyzed.