The iron and steel industry is considered as one of the hard-to-abate heavy sectors due to the massive demand for metallurgical coke in the energy-intensive blast furnace (BF) ironmaking process. In this work, an electrochemical conversion of two major metallurgical exhaust gases, namely, blast furnace (BFG) and coke oven gas (COG) into renewable methanol (CH₃OH) is proposed for deeply decarbonizing steel production. An innovative low-carbon BF ironmaking process, which combines solid oxide cells (i.e., renewable-powered co-electrolysis and COG-fed solid oxide fuel cells) and oxyfuel combustion for CO₂ capture, is thermodynamically modeled to evaluate various performance metrics in terms of energy conversion efficiency, product yield, and carbon intensity of renewable methanol. To enhance the process conversion efficiency, four different recycling configurations are designed and compared for efficient tail gas utilization: Scenarios 1 and 4 (co-electrolysis and methanol synthesis via short-loop recirculation) and Scenarios 2 and 3 (co-electrolysis and methanol synthesis via long-loop recirculation). The results indicate that efficient tail gas utilization via long-loop recirculation into the co-electrolysis unit could generate a much higher methanol yield than the short-loop design. Up to 73 % carbon conversion efficiency can be achieved, while 30 % energy conversion efficiency can be attained using long-loop design at a recirculation ratio (RR) of 0.8. Nevertheless, a higher RR operation results in increased energy demand associated with the methanol synthesis process, which in turn leads to higher indirect carbon emissions. Overall, the carbon intensity of methanol ranges from approximately 1.05–1.48kg-CO₂/kg-CH₃OH across the four process configurations under the selected RRs. The long-loop design is likely to offer a reduction in CO₂ emissions of up to 57 % compared to the traditional blast furnace ironmaking process. In particular, a maximum energy conversion efficiency of 38 % can be achieved through heat integration, while net negative CO₂ emissions are achievable based on the evaluated system boundary. The developed process not only has great potential to close the carbon loop between steel makers and chemical producers but also efficiently stores energy in the form of renewable methanol.

Renewable synthesis fuels play a crucial role in enabling a circular economy. This study assesses the environmental impacts of power-to-hydrogen and biomass-to-hydrogen routes, considering four hydrogen storage options: hydrogen, ammonia, methane, and methanol with a function unit of 1 liter of a stored hydrogen-derived product. The assessment encompasses metrics such as carbon footprint, use of fossil and nuclear energy, ecosystem quality, human health impact, and water scarcity. The results reveal that the biomass-based route has a lesser impact on global warming potential (GWP), with the system involving chemical looping technology and using ammonia as the storage medium achieving a negative GWP of -7.55 kg CO₂eq. The power-based route outperforms the biomass-based route except for GWP which is influenced by the penetration of renewable energy. Liquid hydrogen is found to be suitable for the fossil fuel-based route, while methane and ammonia are favorable to the power-based and biomass-based routes, respectively.

Efficient CO₂ utilization in the thermochemical conversion of biomass plays an important role in creating a future low-carbon economy. This study attempts to explore the CO₂-assisted chemical looping gasification and co-gasification process of lignocellulosic biomass components (hemicellulose, cellulose, and lignin) with iron oxide oxygen carriers using thermogravimetry and differential thermal analysis. Three different iron oxide oxygen carrier-to-biomass (O/B) ratios were taken into account to deeply understand the thermal degradation characteristics of individual components (O/B ratio: 0) and their blending with iron oxide oxygen carriers (O/B ratio: 0.5 and 1). Meanwhile, the reduction characteristics of three major biomass components were also investigated in terms of X-ray diffraction (XRD), synergistic interaction, and reduction degree. Experimental results suggest that the existence of iron oxide oxygen carriers could accelerate the reaction kinetics under the reactive CO₂ environment, arising from the competitive relationship between the direct reduction reaction by char in biomass and the Boudouard reaction at high temperatures (600–950 °C). Interestingly, the reoxidation behavior of the reduced iron oxide is observed at high temperatures, especially for lignin. Among all the tested biomass materials, their ability to reduce iron oxide oxygen carriers under the CO₂ atmosphere follows the order of biomass mixture (1:1:1 wt%)>lignin>xylan>cellulose. Moreover, the findings indicate that significant synergistic interaction exists during the CO₂-assisted chemical looping co-gasification process.

Because of their compact structure, ease of processing and higher heat transfer coefficient, curved-tube heat exchangers are widely applied in various industry applications, such as nuclear power systems, solar-powered engineering, aircraft engine cooling systems and refrigeration and cryogenic systems. Accurate knowledge about the heat transfer characteristics of the supercritical fluids in the tube is critical to the design and optimization of a curved-tube heat exchanger. The available literature indicates that the flow of supercritical fluids flowing in curved tubes affected by the dual effects of the buoyancy force and centrifugal force is more complex compared to straight tubes. Therefore, to obtain insight into their unique characteristics and further research progress, this paper presents a comprehensive review of available experimental and numerical research works on fluids at supercritical pressure flowing in curved tubes. Overall, the secondary flow caused by the curvature enhances the heat transfer and delays the heat transfer deterioration, but it also causes a non-uniform heat transfer distribution along the circumferential direction, and the strengthening performance of the curved tube is damaged. Compared with the more mature theories regarding straight tubes, the flow structure, the coupling mechanism of buoyancy and centrifugal force, and the general heat transfer correlation of supercritical fluids in a curved tube still urgently need to be further studied. Most importantly, studies on the suppression of heat transfer oscillations and heat transfer inhomogeneities specific to curved tubes are scarce. Considering the current status and shortcomings of existing studies, some study topics for supercritical fluids in a curved tube are proposed