Thermochemical behavior of agricultural and industrial sugarcane residues for bioenergy applications.

The Colombian sugarcane industry yields significant residues, categorized as agricultural and industrial. While bagasse, a widely studied industrial residue, is employed for energy recovery through combustion, agricultural residues are often left in fields. This study assesses the combustion behavior of these residues in typical collection scenarios. Additionally, it encompasses the characterization of residues from genetically modified sugarcane varieties in Colombia, potentially exhibiting distinct properties not previously documented. Non-isothermal thermogravimetrical analysis was employed to study the thermal behavior of sugarcane industrial residues (bagasse and pith) alongside agricultural residues from two different sugarcane varieties. This facilitated the determination of combustion reactivity through characteristic combustion process temperatures and technical parameters like ignition and combustion indexes. Proximate, elemental, and biochemical analyses revealed slight compositional differences. Agricultural residues demonstrated higher ash content (up to 34%) due to foreign matter adhering during harvesting, as well as soil and mud attachment during collection. Lignin content also varied, being lower for bagasse and pith, attributed to the juice extraction and milling processes that remove soluble lignin. Thermogravimetric analysis unveiled a two-stage burning process in all samples: devolatilization and char formation (~170°C), followed by char combustion (~310°C). Characteristic temperatures displayed subtle differences, with agricultural residues exhibiting lower temperatures and decomposition rates, resulting in reduced ignition and combustion indexes. This indicates heightened combustion reactivity in industrial residues, attributed to their elevated oxygen percentage, leading to more reactive functional groups and greater combustion stability compared to agricultural residues. This information is pertinent for optimizing sugarcane residues utilization in energy applications.

Weather in collection time affects composition of sugarcane agricultural residues.Combustion of sugarcane residues occurs over similar temperature ranges.Industrial residues are more reactive to combustion than agricultural residues.Overall thermal behavior of sugarcane residues depends on their composition.

Novel Thermal and Microscopic Techniques To Determine the Causes of Suboptimal Combustion Performance at Colombian Stoker Furnaces.

This study presents the application of a novel approach, using thermal and optical techniques, to identify the causes of poor burnout performance of Colombian stoker furnaces in the Cauca Valley State. The four coals used in these furnaces were characterized to obtain particle size distribution, particle and tapped density, elemental and proximate composition, mineral composition, and maceral content. Up to 80% incomplete combustion was noted in macro-TGA tests compared to complete combustion in a micro-TGA. Reflectance and intrinsic reactivity measurements were for chars prepared in three different particle sizes (<6, 6-19, and 19 mm), three temperatures (700, 900, and 1050 °C), and three residence times (10, 30, and 120 min). Two of the coals produced char samples with reflectance values above 6%, which matched those seen in the stoker, indicating that the furnace temperature was not the cause of poor combustion and that only two of the four coals were likely to be present in the furnace bottom ash. These tests were also able to prove that oxygen diffusion limitation was the root cause of the poor burnout where the carbon inside the furnace bottom ash was shielded from oxygen ingress through the formation of a nonpermeable slag layer. Thus, this study demonstrates the potential of both thermal profiling and optical reflectance as a tool for forensically evaluating the thermal history and operational performance of furnaces.

Upgrading of Low-Grade Colombian Coals via Low-Cost and Sustainable Calcium Nitrate Dense Media Separation.

Wet coal beneficiation in Colombia is prohibitive due to the high cost and scarcity of commonly used dense media. The practical value of this study is that it demonstrates for the first time that a common fertilizer, calcium nitrate, can be used in the beneficiation of low-grade Colombian coals. Three high-ash low-grade Colombian coals (Valle, Cundinamarca, and Antioquia) commonly used in Colombian sugar mill stoker furnaces were tested. Coal mineralogy and prevalence were analyzed before and after washing using mineral liberation analysis. The swelling potential of the coals was assessed using a novel application of thermal mechanical analysis (TMA) and an ash fusion oven (AFO). Calcium nitrate reduced ash levels across all size fractions, even for high-ash coals like Valle (29% to below 7%) to acceptable levels for coke manufacturing or pulverized fuel combustion. The novel use of TMA and AFO to analyze coal swelling demonstrated that swelling varies under constrained and unconstrained conditions and the small sample size allows for rapid testing of coal swelling. This study has demonstrated that the use of common fertilizers can allow beneficiation to become a processing option for low-grade coals in Official Development Assistance countries where conventional dense media is prohibitively expensive.

Experimental data on morphological characterization of chars from coal and bagasse blends.

Morphological characterization of chars from coal and bagasse plays an important role in both the burning efficiency and intrinsic reactivity of chars, during a combustion process [1], [2]. In this work, abundant data on the morphology of chars produced from coal and bagasse blends are presented. Char synthesis was performed varying the temperature (900, 1000 and 1100 °C) and bagasse proportion feeding (0, 25, 50, 75 and 100% w/w) in the pyrolysis reaction. Proximate, ultimate, petrographic and vitrinite reflectance of raw coal and bagasse are presented. Char morphology is classified into three groups -- thin walls, thick walls, and solid particles--, and results are exhibited. The data set is a comprehensive source for advancing in a further understanding of char's morphology from coal-bagasse blends.