Heating Strategies in Cellulose Pyrolysis as an Alternative For Targeting Energy Efficient Product Distribution

Energy generation and platform chemicals production from biomass are a potential route towards an oil-free economy. Pyrolysis is one of the key technologies for transforming biomass into both fuels and chemicals. However, pyrolysis is a complex and energy-intensive process, and optimizing the operation for reducing its energy requirements is critical for the design of competitive biorefineries. This work presents a model to describe cellulose pyrolysis based on mass, energy and momentum conservation of solid and gaseous species. Lumped and detailed kinetic models are used to investigate how heating conditions impact pyrolysis product distribution. The resulting complex system was solved using gPROMS. Results suggest that pyrolysis mainly occurs in the boundary of the modelled particles. The developed model presents flexibility to use lumped and detailed kinetic models and provided both a general perspective of the pyrolysis process and detailed information on product distribution. Using this model, the results show that an initial high heating rate, followed by a lower heating rate, could reduce energy requirements by 10 % without changing the product distribution. There is also a trade-off between the yield of high added-value products, such as levoglucosan, and the overall energy requirement

Thermal storage of nitrate salts as Phase Change Materials (PCMs)

This study presents the energy storage potential of nitrate salts for specific applications in energy systems that use renewable resources. For this, the thermal, chemical, and morphological characterization of 11 samples of nitrate salts as phase change materials (PCM) was conducted. Specifically, sodium nitrate (NaNO3), sodium nitrite (NaNO2), and potassium nitrate (KNO3) were considered as base materials; and various binary and ternary mixtures were evaluated. For the evaluation of the materials, differential Fourier transform infrared spectroscopy (FTIR), scanning calorimetry (DSC), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) to identify the temperature and enthalpy of phase change, thermal stability, microstructure, and the identification of functional groups were applied. Among the relevant results, sodium nitrite presented the highest phase change enthalpy of 220.7 J/g, and the mixture of 50% NaNO3 and 50% NaNO2 presented an enthalpy of 185.6 J/g with a phase change start and end temperature of 228.4 and 238.6 °C, respectively. This result indicates that sodium nitrite mixtures allow the thermal storage capacity of PCMs to increase. In conclusion, these materials are suitable for medium and high-temperature thermal energy storage systems due to their thermal and chemical stability, and high thermal storage capacity

Syngas composition in atmospheric pressure gasifiers after a catalytic treatment

The current work describes the experimental results of the composition of syngas obtained from gasification of municipal solid waste (MSW). This particular study was carried out in an updraft, atmospheric-pressure, and pilot-scale gasifier. The gasifier is also outfitted with a gas reflux line, air and oxygen feed, and a catalytic packed-bed reactor coupled to the gasification unit in order to improve the syngas quality. Characteristics and operation variables related to the gas retention time along the gasifier and catalytic reactor are also mentioned and analyzed as part of the described study. The assessment was focused in increasing the carbon monoxide (CO) concentration in the outlet stream of syngas while the carbon dioxide (CO2) is reduced. Observed effects in other gaseous components of syngas are also mentioned . Preliminary results show the proposed alternative is able to increase the CO/ CO2 ratio in 30% in comparison with reported results of similar gasifiers. The described phenomenon appears as a suitable and low-cost alternative for enhancing the energy content and the content of energy vectors such as CO and hydrogen (H2) of syngas in gasification processes since high pressure conditions are avoided