Biomass
and plastic waste gasification has been demonstrated as
a promising technology for developing a long-term waste management
system that reduces emissions and enhances energy recovery. Chemical
looping co-gasification of alfalfa (AL) and polyethylene (PE) with
Fe2O3 as oxygen carrier (OC) was studied in
a fixed-bed reactor. The effects of temperature, steam/alfalfa mass
ratio (S/AL), OC/alfalfa mass ratio (OC/AL), and PE/alfalfa mixing
ratio (PE/AL) were investigated. The results revealed that at a gasification
temperature of 950 °C, the optimum product distribution was achieved
with a S/AL ratio of 1, an OC/AL ratio of 0.5, and PE/AL mixing ratios
of 50 and 75%. The presence of PE in the feedstock led to higher production
of synthetic gas, particularly the hydrogen yield, as the H2/CO ratio increased to more than 2 to match the demand of Fischer–Tropsch
synthesis. At a mixing ratio of 50%, the lower heating value and the
H2/CO ratio achieved their maximum values of 14.05 (MJ/Nm3) and 2.50, respectively. This research clarified that the
combined gasification of biomass with plastic constitutes an ideal
approach for high-quality synthesis gas production as well as environmental
preservation and materials recycling.
Novel flue-gas internal recirculation (FIR) is gaining increasing attention owing to its overwhelming stable combustion and nitrogen oxide (NOx) reduction advantages. This paper aims to reveal the nitrogen reduction mechanisms in the exciting new FIR methods and discuss the main FIR techniques in terms of combustion performance. In particular, the basic concept and the nitrogen reduction mechanism of FIR are first introduced. Besides, three main categories of FIRs are reviewed in accordance with the characteristics and operation status of different devices. The analysis of 16 FIR systems suggests that the recirculation space, effective recirculation rate, and combustion ignition limit must be considered during the design process, in order to balance NOx reduction and combustion efficiency. The integrated FIR and external FIR can achieve NOx emission reductions of at least 20% and 15.5%−20%, respectively. The embedded FIR exhibits more outstanding NOx emission reduction performance, with NOx reduction ratios of up to 26.09%−65%. In addition, the influence elements of FIR on combustion efficiency and nitrogen reduction are also discussed. In conclusion, strategies aimed at enhancing the combustion performance of novel FIR burners are thoroughly delineated, and the challenges that need to be addressed are succinctly highlighted in a forward-looking perspective. This review is expected to clarify the NOx reduction and combustion characteristics of current FIR techniques and suggest a development direction for FIR design.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.