Search

In this work is presented a repeatability study applied to a cookstove based on wood pellets gasification (19.03 MJ/kg). The analysis is carried out under a modified water boiling test (WBT 4.2.3). The repeatability of the gasification-based cookstove was assessed by means of two methodologies, such as the variation coefficient (CV, %) and the analysis of variance (ANOVA). The answer variables evaluated under repeatability were the efficiency (η, %), power (P, kW), fuel consumption (FC, g/min), fuel specific consumption (SFC, g/L), energy specific consumption (SFEC, kJ/L), and energy specific consumption per unit time (SFCT, kJ/L-min). By the CV analysis, the global average CV was 4.69% ± 0.87%. Therefore, as CV ≤ 5%, it is concluded that the gasification based cookstove is statistically repeatable. Concerning the ANOVA, the P-values of the variables studied were higher than 0.05 (P>0.05), thereby, it is stated that the improved cookstove is repeatable with a confidence level of 95%. Consequently, it is highlighted that the average thermal efficiency reached by the cookstove is ~29% ± 2.25%, with a confidence level of 95%. This thermal efficiency value is comparable with other biomass cookstoves based on gasification reported in the literature with values between 16 and 38%. The methodology and the results of this work constitute a theoretical foundation for assessing future developments of biomass cookstoves since the results reliability found in the prototypes tested at the laboratory level can be quantified and analyzed. [ABSTRACT FROM AUTHOR]

Biochar (BC) is a solid byproduct of gasification and could be valorized looking for contributing to the feasibility of gasification projects. In this study, the effect of airflow during fixed-bed gasification of pelletized fallen leaves to BC was evaluated at 0.075 and 0.150 kg/s/m2. The influence of glycerol in the leaf feedstock was also studied, and the gasification products were characterized. BC formation under gasification conditions was simulated using a two-dimensional (2D) unsteady computational fluid dynamics (CFD) model. When airflow was increased, convective heat transfer from the gas to the solid phase increased by 250%, and absorption of radiative heat transfer in the solid phase increased by 59%. This was ascribed to the increase in the process temperature, which also promoted the release of volatile matter. The H:C and O:C ratios in the feedstocks were reduced by 80% and 92%, respectively. The surface areas and pore volumes of the samples increased by up to 50%. The BC with the largest surface area (68.63 m2/g) also had the highest total organic carbon content (21.3%) and the highest water retention capacity (408.13%). The pH of the BCs obtained in the study ranged from 8.7 to 10, making them suitable for acid soils. • Gasification's cold gas efficiency of fallen leaves pellets (FLP) is up to 60%. • Convective and radiative heat transfer affect physicochemical properties of biochar. • If glycerol increases, biochar (BC) density decreases and BC temperature increases. • FLP's BC as a byproduct of fixed-bed gasification is suitable for acid soils. • FLP's BC is not suitable as a solid fuel due to its high ash content (∼58 wt%). [ABSTRACT FROM AUTHOR]

The gardens from the University of Antioquia main campus (Colombia) produce ∼2.8 tons of fallen leaves (FL) per month on a dry weight basis. A sample of this garden waste was pelletized (fallen leaves pellets, FLP). Accordingly, the physical and thermochemical properties of FLP were characterized for use as solid biofuel. The densification of FL was carried out with varying moisture (10, 15 and 20 wt%) and the glycerol contents (0, 5, and 10 wt%) as binders following a multifactorial statistical experimental design. In particular, the significant effect of the glycerol content on physical properties of FLP is noteworthy, as its increase influenced bulk density, which decreased from 524 to 380 kg/m3. Furthermore, it was found that with the simultaneous increase of moisture and glycerol contents, tensile strength decreased by 10%, but the elastic behavior of pellets was elevated, leading to increases in their deformation capacity from 0.75 mm to 2.35 mm. This behavior can also be checked with superficial hardness of FLP, which decreased by up to 70% when the glycerol content increased. The fuel value index of FLP diminished by 15% with the glycerol content, while the volatile matter increased, leading to improve the reactivity of the pellets. Image 1 • A physical and thermochemical analysis of fallen leaf pellets is presented. • If moisture and glycerol content increase in pellets, densities decrease. • If glycerol content increase, tensile strength decreases, and deformation increases. • Volatile matter of pellets increases with low moisture and high glycerol contents. • The glycerol addition in low concentrations improves energy properties of pellets. [ABSTRACT FROM AUTHOR]

• Biochars (BCs) from main biomass commodities traded worldwide are characterized. • Gasification temperature of wood pellets (WP) is higher than that of chips (WCH). • High density and temperature lead to increase the gasification efficiency by ∼41 %. • As BC from WP has 367.33 m2/g and 29.25 MJ/kg, it is a suitable solid biofuel. • WP as compared to WCH is a better feedstock to co-produce producer gas and BC. Wood pellets (WP) and chips (WCH) are the most frequently sold products worldwide to produce bioenergy under thermochemical processes. The effects of the bulk density of patula pine (Pinus patula) WP (555.97 kg/m3) and WCH (151.29 kg/m3), and their gasification conditions were studied on the properties of the produced biochars (BCs). The aim of this study was to generate a good-quality gas fuel (producer gas), as well as a BC with properties that would enable it to be used as a solid biofuel instead of being considered as a byproduct or waste. An atmospheric reverse-downdraft gasifier was used, setting the air flow at 0.12 kg/m2/s for the samples of biomasses studied. With regard to the gasification performance, the temperature inside the reactor was found to increase by 70 % for WP, obtaining a higher cold gas efficiency (51.6 %) in comparison with the efficiency achieved for WCH (36.7 %). Concerning the properties of the BCs, the highest gasification temperature allowed to reach a pellet-derived biochar (WP-BC) with a surface area (BET) larger than that one obtained for the chip-derived biochar (WCH-BC), with 367.33 m2/g and 233.56 m2/g, respectively. Furthermore, the WP-BC heating value was found to be 29.25 MJ/kg, while this parameter for the WCH-BC was 28.36 MJ/kg. It is highlighted the low probability of corrosion and ash fusion occurrence within the reactor when using these biofuels (raw and BCs). Additionally, regarding the pyrolysis kinetics of the raw biomasses, WCH showed a higher reactivity with an activation energy (E α) of 80.84 kJ/mol in comparison with the E α value obtained for WP (124.38 kJ/mol). [ABSTRACT FROM AUTHOR]