The energy-efficient removal of CO2 from flue gas has become increasingly important for operators of CO2-emitting industrial facilities such as waste-to-energy plants and cement production sites. Conventional carbon capture processes have long been employed for acid gas removal (natural gas treatment) and are technologically mature. However, when applied for CO2 capture from flue gases, these methods substantially decrease net energy production of the plants, and in many regions the regulatory framework for underground CO2 storage remains uncertain. In recent years, a new process has been developed in which CO2 capture and conversion are integrated into a single step through electrochemical solvent regeneration and conversion. The integration of regeneration and conversion promises a more straightforward process design and lower energy requirements for the production of carbon based products from diluted CO2 sources. This work compares (1) interconnected state-of-the-art process chains—such as monoethanolamine (MEA) based CO2 separation with subsequent reverse water-gas shift synthesis gas production, and Fischer-Tropsch (FT) or methanol (MeOH) synthesis, and (2) emerging electrochemical CO2 conversion processes. Contrary to what current literature indicates, the findings in the carried out simulations show that conventional state-of-the-art processes require less energy to capture and convert CO2 than the electrochemical pathway at its current stage of development. However, the difference in energy requirement is small especially with FT syncrude as an end product. The results show that the carbon capture and conversion effectiveness of the electrochemical pathways exceeds the carbon capture and conversion effectiveness of the MEA and hot potassium carbonate (HPC) pathways and leads to higher product outputs. Compared to conventional pathways, the electrochemical pathway has a 4.4 percentage points higher carbon capture and conversion effectiveness for MeOH production and a 15.5 percentage points higher carbon capture and conversion effectiveness for FT syncrude production, which highlights the large potential for electrochemical pathways. It is anticipated that the electrochemical pathway will become energy-competitive in the future, provided that development continues rapidly and the technology achieves parity with the advancement of water electrolysis.
The surface of 4H-SiC has been sputtered with Arn+ GCIBs (gas cluster ion beams) at varying kinetic energies ranging from 2.5 to 8.0 eV/atom with cluster fluences reaching the range of 1015 clusters·cm−2 to investigate the near-surface chemical modifications after high-energy bombardment. Sputtering was performed in-situ of a XPS (X-ray photoelectron spectroscopy) equipment to monitor the evolution of these modifications compared to an as-received 4H-SiC surface. Changes in core-level spectra, preferential sputtering, peak shift, and the appearance of a new spectral component were observed. The impact of low- and high-intensity GCIB cleaning regimes was demonstrated by detailed analysis of C 1s and Si 2p spectra. While optimized sputtering conditions enable gentle, selective surface cleaning, excessive kinetic energy or cluster fluence can induce the formation of metallic silicon, potentially leading to misinterpretation of XPS data.
High-speed scanners often suffer from limited scanning accuracy due to the bandwidth constraints of feedback control. Although conventional iterative learning control (ILC) can improve performance, its learning bandwidth remains constrained by model uncertainties and hardware constraints associated with the scanner’s structural dynamics. This paper proposes a direct frequency selection-based ILC (DFS-ILC) framework tailored to repetitive scanning systems with fixed duty cycles. By exploiting a lifted-form representation of repetitive dynamics, DFS-ILC provides a systematic frequency-wise learning design in which the admissible learning bandwidth is determined by the system dynamics and a corresponding bandwidth-limited reference is constructed. By matching the reference bandwidth to the learning bandwidth, the proposed approach avoids excitation of undesired structural modes while theoretically achieving perfect tracking within the admissible frequency range. Upon learning convergence, the residual scanning error is therefore primarily determined by the reference reconstruction error. The effectiveness of DFS-ILC is experimentally demonstrated on a polygon mirror-based high-speed stereolithography system for active error compensation, achieving up to a 50% improvement over conventional ILC methods.
The structural behavior of a 640 m long stretch of the segmental lining in the north tube of the Koralm tunnel’s construction lot KAT3 is analyzed. Over a period of 3.5 years, circumferential normal strains were measured in nine measurement rings, each consisting of seven tubbings equipped with a centrally located strain sensor pair. A hybrid analysis combines the monitoring data with (visco)elastic modeling of concrete and steel as well as kinematics of slender circular arch theory. This allows for computing circumferential normal forces and axial bending moments at longitudinal sections through the measurement tubbings containing the strain sensor pairs. Cubic splines are used for circumferential interpolation between sensor positions and longitudinal interpolation between measurement rings. The obtained fields of internal forces are translated into fields of utilization degrees of both the reinforced concrete tubbings and the longitudinal joints consisting of plain concrete. The utilization degrees are illustrated in interaction diagrams. All computed pairs of normal force and bending moment – including those transmitted across reinforced tubbing sections – fall within the ultimate capacity boundary of the longitudinal joints. This is consistent with the interpretation that the longitudinal joints play a role in controlling lining stresses. This is particularly the case in highly utilized joints, where concrete exhibits nonlinear creep. This amplifies the overall deformability of the segmental tunnel ring, and thus provides a possibility for the lining to follow the deformation of the surrounding ground mass without activating overly high internal forces.
Understanding the thermochemical conversion of pulverized coal (PC) in the blast furnace raceway zone is essential for improving coal utilization and process efficiency. However, determining kinetic parameters under raceway conditions remains challenging because direct measurements at high temperatures, pressures, and heating rates are limited. In this study, the Alternative Reducing Agents (ARA) reactor was used to investigate the pyrolysis and combustion behavior of a low volatile coal under raceway relevant conditions. Separate experimental series were conducted by systematically varying oxygen partial pressure, absolute pressure, reactor temperature, and particle heating rate. The heating rate effect was evaluated by operating the reactor with and without a hydrogen burner positioned at the particle injection point. Burner activation increased the particle heating rate by a factor of 2 to 4 and raised the local gas temperature.Absolute pressure reduced pyrolysis rates at low heating rates, while this effect is negligible at high heating rates. Significant effects of temperature on the pyrolysis rate were observed until 1200 ∘C, whereas an increase to 1400 ∘C had only a minor effect. No clear trend was observed for the heating rate effect on pyrolysis.Under combustion conditions, burnout increases at higher oxygen partial pressures and temperatures, while a minor effect of the absolute pressure was also observed. Heating rate effects were hard to evaluate due to a simultaneous temperature increase in the gas stream. Determining reaction orders for coal oxidation yielded different results between experiments with and without the burner. Reaction orders for oxygen between 0.7 and 0.8, and between 0.5 and 1.12 were determined for low heating and high heating rates, respectively, at the different experimental temperatures.Additional comparison data from ARA experiments and blast furnace injection are required before ranking PC is possible.
