Yue Jiao

Co-combustion is a crucial route for the high-efficiency utilization and clean conversion of different carbonaceous feedstocks (biomass, coal, petroleum coke, etc.). The migration and transformation of alkali and alkaline earth metals (AAEMs) are not only related to ash-related issues in actual application, but also directly affect the reaction behavior of binary particles during co-conversion. This review paper summarizes research progress in the detection methods (online and offline) and influencing factors (feedstock type, feedstock blending ratio, reaction temperature, reaction time) of AAEMs migration and transformation during the co-combustion of carbonaceous feedstocks. Furthermore, it provides a detailed summary of research progress on factors (feedstock blending ratio, heating rate, etc.) influencing the co-combustion reactivity of carbonaceous feedstocks, synergy behavior, and its mechanisms. The influence of feedstock type on AAEMs migration and transformation during co-combustion is mainly related to the composition categories, chemical forms and contents of intrinsic mineral in binary feedstocks. The increase in the combustion temperature will intensify the release of inherent AAEMs in carbonaceous feedstocks, and promote AAEM deactivation. For high K and Cl-containing biomass, a higher biomass proportion in blends would result in more AAEMs release during the co-combustion process. Conversely, an increase in coal proportion in blends will directly favor the reduction or inhibition of AAEMs release. Synergy behavior during co-pyrolysis and subsequent char co-combustion is usually presented as an inhibition effect and an synergistic effect, respectively. The synergistic mechanisms of carbonaceous feedstock co-combustion reactions can be divided into two categories: non-catalytic synergistic mechanisms related to the excitation and migration of biomass-based free radicals and catalytic synergistic mechanisms related to biomass-based AAEMs catalysis. Additionally, future research prospects are also proposed based on the systematic review.

Bamboo, a rapidly growing plant known for its remarkable strength-to-weight ratio and eco-friendly qualities, finds extensive applications in decorative construction materials and glue-laminated beams. However, the dimensional instability and flammability of natural bamboo limit its application range. In this study, a series of environmentally friendly methods are devised to produce functional bamboo hybrids possessing exceptional strength, excellent dimensional stability, and flame-retardant properties. These hybrids are created through bamboo delignification, in situ mineralization of CaCO₃, and hot pressing after impregnation with phenolic resin. The highly aligned and densified nanocellulose stacking between hydrogen bonds of the bamboo hybrids results in the high tensile (583.6 MPa) and flexural strength (374.8 MPa), as well as an excellent specific strength of 486.3 MPa (cm³ g)⁻¹. This value is significantly greater than those of other reported bamboo materials and most structural materials (e.g., steels and alloys). The favorable dimensional stability of the as-prepared bamboo hybrids is mainly associated with the impregnation of phenolic resin and mineralization of CaCO₃ with the improvement of hydrophobicity. Compared to natural bamboo, the total heat release and smoke production rate of the bamboo hybrid were reduced by 37.7% and 50.0% respectively. This study provides a green processing strategy to manipulate and functionalize the microstructure of bamboo into high strength, superior fire-retardancy, and dimensional stability in various applications, such as structural construction, aerospace, and automotive manufacturing.