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Several combustions tests using biochar briquettes of peanut shells and charcoal from Ziguinchor town in a locally named “jambar” stove are reported in this article. The biochar briquettes were produced following a 23 factorial plan for testing the influence of the rate (R) of binder on a dry basis, the pyrolysis temperature (T), and the volume (V) of ellipsoid shape biochar briquette on emission factors (CO and PM2.5) and thermal efficiency. The minimal and maximal levels were defined as following R = [6%; 10%], T = [400 °C; 800 °C], and V = [7 cm3; 31 cm3]. Wheat flour was used as a binder. A specially designed hood with an extractor fan is used to collect the overall emissions produced during a simulated household cooking task. Physicochemical characterizations are conducted to determine immediate analysis, elemental analysis, and calorific value of the produced biochar briquettes and the charcoal from Ziguinchor town. The results of the physicochemical characterizations show that all produced biochar briquettes had a content of fixed carbon greater than 60%, ashes content below 18%, and moisture content below 8%. All biochar briquettes presented a lower heating value (between 24.35 MJ/kg and 26.55 MJ/kg) below those from Ziguinchor charcoal (28.02 MJ/kg). The results show that the CO emission factors varied from 140.08 g/kg to 217.09 g/kg when the levels of factors changed. The CO emission factor of charcoal from Ziguinchor was 178.46 g/kg. The lowest CO emission factor, 140.08 g/kg, was obtained for the lower levels of the factors (R = 6%, T = 400 °C, and V = 7 cm3). The PM2.5 emission factors of the biochar briquettes varied from 0.57 mg/kg to 1.53 mg/kg and were equal to 7.91 mg/kg for Ziguinchor charcoal. The lowest PM2.5 emission factor, 0.57 mg/kg, was obtained for the levels of the factors (R = 6%, T = 800 °C, and V = 31 cm3). It was generally observed that the more is the rate of binder and the volume of the briquette, the more is the emissions of PM2.5 and CO, respectively.

The torrefaction (mild pyrolysis) process modifies biomass chemical and physical properties and is applied as a thermochemical route to upgrade solid fuel. In this work, the catalytic effect of thermo-acoustic on oxidizing woody torrefaction is assessed. The combined effect of two acoustic frequencies (1411, 2696 Hz) and three temperatures (230, 250, and 290 &deg, C) was evaluated through weight loss and its deviation curves, calculated torrefaction severity index (TSI), as well as proximate, calorific, and compression strength analysis of Eucalyptus grandis. A new index to account for the catalytic effects on torrefaction (TCEI) was introduced, providing the quantitative analysis of acoustic frequencies influence. A two-step consecutive reaction numerical model allowed the thermo-acoustic experiment evaluation. For instance, the thermogravimetric profiles revealed that the acoustic field has a catalytic effect on wood torrefaction and enhances the biomass oxidation process for severe treatments. The kinetic simulation of the acoustic coupling resulted in faster conversion rates for the solid pseudo-components showing the boosting effect of acoustic frequencies in anticipating hemicellulose decomposition and enhancing second step oxidizing reaction.

International audience; Hybrid propulsion generally combines a liquid oxidizer with a solid fuel. Compared to solid or bi- liquid engines, this type of propulsion offers advantages in terms of cost and flexibility. For several years, ONERA has been providing expertise in this area, both in experimental and numerical simulations. Various hybrid rocket motors have been designed and tested on ground, including under low ambient pressure conditions and in flight. The Propulsion Laboratory unit of the DMAE uses fully instrumented engine breadboards in order to optimize the oxidizer/fuel pair, as well as the injection system and the combustion efficiency. In addition, 0D and 1D codes for engine design areactively being developed. More recently, studies have been undertaken as part of the LEOP future satellite platforms, with the development of an innovative new combustion chamber.; La propulsion hybride combine généralement un oxydant liquide et un combustible solide. Comparé aux moteurs solides et bi-liquides, ce type de propulsion présente des avantages en termes de coût et de flexibilité. Depuis plusieurs années, l’ONERA offre une expertise dans ce domaine, par la réalisation à la fois d’études expérimentales et de simulations numériques. Différents moteurs hybrides y ont été conçus et testés au sol, y compris dans des conditions de haute altitude, et en vol. L’unité Laboratoire de Propulsion du DMAE utilise des moyens d’essais instrumentés pour optimiser le couple oxydant/combustible mais aussi le système d’injection et le rendement de combustion. En outre des codes 0D et 1D permettant la conception de ces moteurs y sont également développés. Plus récemment, des études ont été entreprises dans le cadre des futures plateformes de satellite de télécommunication avec le développement d’une architecture de chambre de combustion innovante.

International audience; The combustion of solid fuels in the rotary kiln and in the calciner of a cement plant generates fuel and thermal NO. This NO can be reduced inside the reducing zone of the calciner. This occurs in two different ways: homogeneous reduction by hydrocarbons and heterogeneous reduction by char. The purpose of this paper is to identify the relative contribution of volatile matters or char on the NO reduction process, which largely depends on the nature of the solid fuel used for reburning.Experiments were undertaken in an Entrained Flow Reactor (EFR), at three temperatures: 800, 900 and 1000 °C. Four major fuels used in the cement production process were studied: a lignite, a coal, an anthracite and a petcoke. Specific experiments were undertaken to determine (i) their devolatilisation kinetics and the gas species released. A wide range of species influencing the NO chemistry was carefully analyzed. Then, (ii) the char oxidation and (iii) the char NO reduction kinetics were characterized. Finally, (iv), the “global” NO reduction capability of each fuel was quantified through experiments during which all phenomena could occur together. This corresponds to the situation of an industrial reactor in reducing conditions. Anthracite and petcoke reduce only very small quantities of NO whereas lignite and coal reduce, respectively, 90% and 80% of the initially present 880 ppm of NO (at 1000 °C after 2 s).The four types of experiments described above were then modeled using a single particle thermo-chemical model that includes heterogeneous reactions and detailed chemistry in the gas phase. This model reveals that both NO reduction on char and NO reduction by volatiles mechanisms contribute significantly to the global NO reduction. After short residence times (several tenth of a second), gas phase reactions reduce NO efficiently; after long residence times (several seconds) the char reduces larger quantities of NO.

The rate of burning (pyrolysis) of cribs of wood and non- dripping synthetic polymers has been studied at various levels of forced ventilation. It has been found that the burning of non-charring fuels is virtually unaffected by the ventilation level, whereas charring materials burn faster up to a maximum as the flow rate of air increases., Reprinted from: Combustion and Flame, v. 31, no. 1, 1978, p. 259-264. ISSN: 0010-2180. DOI: 10.1016/0010-2180(78)90138-4