Sugarcane bagasse has a great potential to be used as biofuel; however, its use as feedstock in fluidized bed reactors is hampered due to its fibrous nature, low apparent density, high moisture content, and difficulties with its fluidization. The present study evaluated the torrefaction of sugarcane bagasse to propose suitable process conditions that balance the properties of the fuel obtained in the torrefaction and the process’s energy requirements. Based on the thermogravimetric analysis and previous reports, two final process temperatures (230 °C and 280 °C) and residence times (35 and 45 min) for the same heating rate (5 °C/min) and nitrogen flow (1 L/min) were evaluated. Within the experimental conditions evaluated, it can be concluded that for 30 min of residence time, the average target temperature of 230 °C should be high enough to produce a stable torrefacted bagasse with a 3.41% reduction in the volatile content and obtain 98.85% of energy yield. Higher temperatures increase the feedstock’s carbon content and energy density, but the reduction in energy yield and the fraction of volatiles do not justify higher temperatures or longer residence times for pretreating the sugarcane bagasse.
Global gas markets are changing as natural gas (NG) is replaced by biomethane. Biomethane is produced by upgrading biogas, which can have a molar concentration of methane to over 98%. This renewable energy has been injected into the pipeline networks of NG, which offers the possibility to increase its usage in industrial and residential applications. However, the expectation of the increase in biomethane proportion on the NG grids could increase the fluctuations on the composition of the NG–biomethane mixture in amplitude and frequency. In this context, the injection of biomethane into the existing network of NG raises a discussion about the extent to which variations in gas quality will occur and what permissible limits should exist, as variations in combustion characteristics can affect the operation of the combustion processes, with consequences for consumers, distributors and gas producers. This study describes a gas quality analysis with regard to the use of biomethane in industrial equipment, mixed or not mixed with NG, taking into account the indicators for gas interchangeability and provides a discussion on the necessary gas quality level to be achieved or maintained for efficient combustion in equipment originally designed to operate with NG. NG and biomethane real data collected for 92 consecutive days in 2022 and provided by two different companies in Brazil were used for this study. It is shown that the maximum deviation of the Wobbe Index (WI) of 5%, which is allowed for industrial plants, does not work for the operation of furnaces at temperatures of 1200 °C or more. In addition, it is shown that the WI, as defined in relation to the calorific value of the fuel, may allow inappropriate substitution of fuel gases, which is likely to reduce the range of blending of biomethane in NG pipelines. The results can be assessed to analyze how the addition of biomethane to NG grids will impact the WI and the equipment operation parameters such as the air-to-gas ratio, products-to-gas ratio, adiabatic flame temperature and furnace temperature.
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