Synergistic interaction and biochar improvement over co-torrefaction of intermediate waste epoxy resins and fir

This study investigated the synergistic effect of co-torrefaction with intermediate waste epoxy resins and fir in a batch-type reactor towards biochar improvement. The synergistic effect ratio was used to judge the interaction between the two materials assisted by statistical tools. The main interaction between the feedstocks was the catalytic reaction and blocking effect. Sodium presented in the intermediate waste had a pronounced catalytic effect on the liquid products during torrefaction. It successfully enhanced the volatile matter emissions and exhibited an antagonistic effect on the solid yield. Different from the catalytic reaction that occurred during short retention time, the blocking effect was more noticeable with a longer duration, showing a synergistic effect on the solid yield. Alternatively, a significantly antagonistic effect was exerted on oxygen content, while the carbon content displayed a converse trend. This gave rise to a major antagonistic effect on the O/C ratio which was closer to coal for pure materials torrefaction. The other spotlight in this study was to reuse the tar as a heating value additive. After coating it onto the biochar, the higher heating value could be increased by up to 5.4%. Although tar is considered as an unwanted byproduct of torrefaction treatment, the presented data show its high potential to be recycled into useful calorific value enhancer. It also fulfills the scope of waste-to-energy in this study

Progress in biomass torrefaction: Principles, applications and challenges

The development of biofuels has been considered as an important countermeasure to abate anthropogenic CO2 emissions, suppress deteriorated atmospheric greenhouse effect, and mitigate global warming. To produce biofuels from biomass, thermochemical conversion processes are considered as the most efficient routes wherein torrefaction has the lowest global warming potential. Combustion is the easiest way to consume biomass, which can be burned alone or co-fired with coal to generate heat and power. However, solid biomass fuels are not commonly applied in the industry due to their characteristics of hygroscopic nature and high moisture content, low bulk density and calorific value, poor grindability, low compositional homogeneity, and lower resistance against biological degradation. In recently developing biomass conversion technologies, torrefaction has attracted much attention since it can effectively upgrade solid biomass and produce coal-like fuel. Torrefaction is categorized into dry and wet torrefaction; the former can further be split into non-oxidative and oxidative torrefaction. Despite numerous methods developed, non-oxidative torrefaction, normally termed torrefaction, has a higher potential for practical applications and commercialization when compared to other methods. To provide a comprehensive review of the progress in biomass torrefaction technologies, this study aims to perform an in-depth literature survey of torrefaction principles, processes, systems, and to identify a current trend in practical torrefaction development and environmental performance. Moreover, the encountered challenges and perspectives from torrefaction development are underlined. This state-of-the-art review is conducive to the production and applications of biochar for resource utilization and environmental sustainability. To date, several kinds of reactors have been developed, while there is still no obviously preferred one as they simultaneously have pros and cons. Integrating torrefaction with other processes such as co-firing, gasification, pyrolysis, and ironmaking, etc., makes it more efficient and economically feasible in contrast to using a single process. By virtue of capturing carbon dioxide during the growth stage of biomass, negative carbon emissions can even be achieved from torrefied biomass

Kinetic and thermodynamic analysis of iron oxide reduction by graphite for CO<inf>2</inf> mitigation in chemical-looping combustion

© 2020 John Wiley & Sons Ltd Chemical-looping combustion (CLC) provides a platform to generate energy streams while mitigating CO2 using iron oxide as a carrier of oxygen. Through the reduction process, iron oxide experiences phase transformation to ultimately produce metallic iron. To understand iron oxide reduction characteristics and optimally design the fuel reactor, kinetic and thermodynamic analyses were proposed, utilizing graphite. This study aims to evaluate the reduction behavior under the non-isothermal process of various mixture ratios of hematite and graphite via thermogravimetric analysis with simultaneously evaluating evolved gases using a Fourier transform infrared spectrometer. The Coats-Redfern model was employed to approximate the kinetic and thermodynamic parameters which assessed the different reaction mechanisms together with the distributed activation energy model (DAEM). The results revealed that the hematite-to-graphite ratio of 4:1 had the highest reduction degree and had three distinct peaks representing three iron oxide reduction phases. The zero-order reaction mechanism agreed with the experimental results compared with other reaction models. The thermodynamic analysis showed an overall endothermic spontaneous reaction for the three phases which signified the direct reduction of the iron oxides. The DAEM result validated a stepwise reduction of iron oxides to metallic iron. The study aids the optimal design of the CLC fuel reactor for enhanced system performance

Flow shear stress applied in self-buffered microbial fuel cells

© 2020 Elsevier Ltd The development of renewable and clean energy has been the priority of the global research field due to the urgent effects of climate change. Microbial fuel cell (MFC) is recognized as a sustainable approach to simultaneously generate power and treat wastewater through the employment of microorganisms as catalyst. The use of buffer solution in the wastewater treatment makes the commercial application of MFCs challenging due to their environmental impact and high costs. This work uses rotational motion to generate the flow stress in the anode chamber of the MFCs to enhance biofilm growth and mass transfer that leads to an overall performance improvement of the system. The effects on pH, chemical oxygen demand (COD), and power density were evaluated under rotational speeds of the magnetic stirrer from 0 to 640 rpm. The influence of the stirrer was then assessed utilizing the same parameters specified for scenarios with and without buffer. The results reveal that at 480 rpm of stirring speed, the pH value was neutral with a maximum COD removal of 82 % for bufferless and 93 % for buffered scenarios. In addition, for bufferless operation at 480 rpm yielded a power density of 402 mWm−2. The results of the flow stress analysis for bufferless and buffered MFCs are beneficial for the commercialization and future development of the system for wastewater treatment applications