Conception and elaboration of a prototype of pellet domestic stove and combustion tests with DIN+ pellets
Session chaired by Pr. Epaminondas Mastorakos
The present study deals with the possibility to use waste from Cameroonian forest- and agro-industries as combustible for energy production in a circular economy. Such waste may first be assembled in pellets for easier transportation from the production zone to the final destination and for preparation of a combustible with higher energy density. Selected Cameroonian and more generally sub-Saharan waste (palm nut shells, palm nut fibers and coffee husks) and the associated pellets were characterized,and their thermodynamic profile was determined through pyrolysis and combustion processes performed in a thermobalance. These materials were proved to be appropriate candidates for combustible, [1]. More specificaly, the present study focuses on the elaboration of a low-cost domestic stove which could use such pellets for example for cooking purpose at a domestic scale. The combustion zone of the pellet stove consists of a cone placed in a cylinder to concentrate the hot gases in the upper part of the stove. A pan filled in with 5 liters of water was placed on the thick (6 mm) plate or circular crown posed on the upper part of the stove. Normalized DIN+ pellets were used during the combustion tests in this stove. The temperatures were measured during the combustion test through thermocouples type K placed at different zones of the stove. The thermal efficiency of the stove was determined first determining the HHV of the DIN+ pellets and observing the time necessary to bring the water to ebullition with a pellet flux of 900 g/h. The thermal efficiency was measured at low levels in the case of the thick plate and slightly higher in the case of the thick circular crown. The thermal behavior of the stove was simulated writing balances in the complete system and assuming simplifying hypotheses, among which a uniform temperature of the thick plate. The model predicts a faster increase of the temperature of the water in the pan than observed during the experiment. The exhaust gases (especially CO, as NOx emissions are very low in biomass combustion) were measured at around 50 cm above the stove with a TESTO 350-XL analyzer, to determine the exposition levels of a person during the stove activity. The CO emissions were measured below 5 ppm. For comparison, OMS suggests a maximal level of 9 ppm CO emissions at human height close to a stove during 8 h without health risks. The next stages of the study will consist to improve the combustion process in an improved domestic stove and to test the combustion of pellets built with Cameroonian waste in this domestic stove. [1]. T. Vitoussia, A. Brillard, D. Kehrli, A. Kemajou, E. Njeugna, J. Brilhac, Thermogravimetric analyses and kinetic modeling of pellets built with three Cameroonian biomass. Biomass Conversion and Biorefinery (2020), 10.1007/s13399-019-00558-3
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