Thermochemical processes, such as pyrolysis and gasification, are gaining increasing attention for syngas production (H2, CO) . These processes are industrially limited by the energetic efficiency in converting biomass and waste into syngas. Indeed, two main issues are highlighted: (1) the production of by-products such as tar and char, and (2) the energy consumption to reach high temperature during pyro-gasification. It has been shown that high temperatures favor the syngas production, and rapid heating enhances H2 amount [2, 3]. In order to overcome energy consumption and high temperatures pyro-gasification, solar pyro- gasification appears as an interesting candidate [3-5]. Most of the studies are focused on the efficiency and the quality of the syngas produced from biomass or coal [2-10]. A few studies have recently focused on the by-products production and the char characterization [11-13]. Char from biomass and waste pyro-gasification may be used in further applications such as catalyst, support of catalyst or sorbent . These uses are directly related to the properties of the char obtained. Moreover, the development of improved biomass solar pyro-gasification models is required for accurate modeling and design of biomass solar pyro-gasification equipment. Such improved models (and necessary kinetic rates) must be based on reliable experimental data obtained with biomass gasification at high temperature and high heating rates, and the element(C, H, O) concentration of reactant should be measured using an on-line, non-intrusive method . Indeed, in the thermal conversion of solid fuels, and particularly of biomass, the hot flue gas is usually contaminated with alkali species (Na, K) in vapor or particulate form. The damage caused to plant materials by such species stems largely from their low melting points and high reactivity. Moreover, biomass is used for heavy-metal containing soil remediation and consequently the behavior of metals during thermal treatment of biomass is a key issue for process development. Thus detailed knowledge on the behavior of metal species in plant processes is needed. Continuous online measurement of the element(Na, K, Pb, As, etc) concentration in the solid during reaction is essential or at least advantageous for control . Laser-induced breakdown spectroscopy (LIBS) is an emerging analytical spectroscopy technique, now become a viable commercial technology. It has been developed rapidly for many purposes, such as identifying elements, material identification, process monitoring, material sorting and site screening [17-19]. LIBS has been developed as a useful method for determining the elemental composition of different materials such as: coal, metal, oil, water..., but it was never reported to be used for biomass ultimate analysis. So, a study of the in-situ measurement of C, H, O and M (metals) concentrations in biomass during its solar pyro-gasification is an innovation and a challenge.
This work has two objectives:
1/ First objective is to implement the LIBS technique to measure quantitatively the C, H, O and M changes in biomass under solar pyro-treatment. The effects of different gasification temperatures, heating rates and gasification pressures for element concentration will be experimented and discussed systematically. These data are essential for the kinetic rate expression and model development concerning biomass gasification by concentrated solar energy.
2/ Second objective is to improve the knowledge on the physico-chemical, thermal, and mechanical properties of the char from solar pyro-gasification, and to better understand the role of the solar flux on its structure and texture. Solar char will be characterized and compared to that from conventional thermochemical processes. Indeed, the temperature and solar flux may impact the char composition [11-13] as well as the mineral clusters . A particular attention will be put on the solar flux-biomass contact, leading to the production of tars. The char characterization will drive the application from cracking reactions, and catalysis, to gas purification, depending on its structure, its mineral/metal content and speciation, its surface functional groups, and its carbonaceous matrix structure.
This work will benefit from the expertise acquired from solar pyro-gasification [11, 12] and char characterization and use .
The candidate will work between PROMES Odeillo-Font Romeu (solar equipment + LIBS) and RAPSODEE Center Albi (char characterization and utilization). The steps of the work will be:
Literature review on subsequent uses regarding char properties
Biomass and/or waste selection
Raw material characterization
Solar pyro-gasification and char collection
Char characterization and comparison to that from conventional pyro-gasification
Experimental investigation of char applications
Application must be sent to Gilles Flamant () and Ange Nzihou () with the subject: “SOLSTICE Post-doc on solar pyro- gasification”.
Starting November 1, 2016, duration: 2 years
The net salary will be in the range 2 100 - 2 800 €/month depending on the background.
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