This article aims to improve the corrosion resistance of 304 stainless steel in high-temperature chloride molten salts, clarify the application effect and corrosion inhibition mechanism of aluminum powder as a corrosion inhibitor, and provide a practical reference for the material protection of solar thermal storage molten salt systems.

The high-temperature electrochemical corrosion behavior of 304 stainless steel was investigated in a ternary chloride molten salt (NaCl-KCl-MgCl₂) at 700 ℃ with the addition of aluminum powder at mass fractions of 0, 1%, 2%, and 5% respectively. Potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) were employed to evaluate the corrosion kinetics and interfacial characteristics. The surface and cross-sectional morphologies, elemental distribution, and phase composition of corrosion products were analyzed using scanning electron microscopy combined with energy-dispersive spectroscopy (SEM/EDS) and X-ray diffraction (XRD).

The addition of aluminum powder significantly suppressed the corrosion of 304 stainless steel. With 5% aluminum powder addition, the corrosion current density decreased from 299.98 mA/cm² (without addition) to 31.673 mA/cm², representing a reduction of 89.4%. The polarization resistance increased markedly from 0.348 Ω (without aluminum) to 2.974 Ω (with 5% aluminum), indicating enhanced resistance to corrosion reactions. Electrochemical impedance spectroscopy (EIS) analysis revealed that the addition of aluminum altered the corrosion control mechanism from diffusion-controlled (without aluminum) to a dual-layer synergistic protection system at higher aluminum contents. After 100 h of corrosion，the thickness of the internal diffusion layer was significantly reduced from 150 μm (without aluminum) to 36 μm (with 5% aluminum powder addition). XRD and SEM/EDS analysis showed that at aluminum additions of 2% and 5%，a continuous and dense Al₂O₃ layer formed on the surface，while aluminum diffused inward to form an aluminum-rich layer and intermetallic AlNi₃ phase within the alloy subsurface. This dual-layer structure effectively suppressed the outward diffusion of Cr and Fe，thereby mitigating corrosion.

The corrosion inhibition mechanism of aluminum powder involves a synergistic protective process. Aluminum preferentially reacts with oxidizing impurities (e.g., moisture and oxygen) in the molten salt, forming a stable Al₂O₃ film on the alloy surface. Simultaneously, a portion of aluminum diffuses inward, creating an aluminum-rich layer and precipitating AlNi₃ phases, which together act as an internal diffusion barrier. This combined surface film and internal diffusion barrier system effectively blocks the outward migration of Cr and Fe, substantially reducing the corrosion rate. The results demonstrate that adding aluminum powder to chloride molten salts is a simple and effective strategy to enhance the corrosion resistance of 304 stainless steel. Future work should focus on the evaluation of the long-term durability and erosion resistance of this protective system under dynamic flow conditions, to facilitate its practical applications in concentrating solar power systems.

To address the issues of insufficient renewable energy integration into the power grid and the high exhaust steam loss in coal-fired power units, a novel Carnot Battery system integrated with a steam ejector is proposed to provide a technical solution for the flexibility transformation of coal-fired units.

This study designed two new systems, System Ⅰ and Ⅱ, utilizing turbine exhaust steam and extraction steam as low-temperature heat sources. System Ⅱ introduces a steam ejector, which uses exhaust from the intermediate-pressure turbine to entrain the exhaust steam, thereby increasing the cold source temperature of the heat storage cycle. Based on the EBSILON Professional, thermodynamic modeling was conducted to compare the coefficient of performance (C_COP), round-trip efficiency (η_RTE), and exergy loss of each system, followed by a techno-economic assessment.

Thermodynamic analysis indicates that the exhaust steam losses of System Ⅰ and Ⅱ are reduced by 38.19 MW and 39.62 MW, respectively, compared to the reference system. Benefiting from the elevated cold source temperature, the C_COP of both systems increased to 1.36 and 1.42. Sensitivity analysis shows that System Ⅱ achieves an optimal round-trip efficiency of 61.51% at a cold source outlet temperature of 55 ℃, an improvement of 2.11 percentage points over the reference system. In terms of techno-economic performance, System Ⅱ performs best, with a dynamic payback period of 9.44 years and a levelized cost of storage as low as 2 094.59 yuan/(MW·h).

The novel System Ⅱ not only effectively reduces energy consumption and improves energy storage efficiency but also demonstrates significant economic competitiveness, which is of great importance for promoting the low-carbon transition of China’s energy industry.

Conventional combined heating and power (CHP) systems often suffer from suboptimal thermal integration and limited exergy utilization, resulting in low overall energy efficiency and significant carbon emissions. To address these challenges, this study proposes a novel high-efficiency CHP system based on the synergistic integration of a solid oxide fuel cell (SOFC) and a lithium bromide (LiBr) absorption heat pump. The architecture is specifically designed to maximize cascaded energy recovery and enhance comprehensive thermodynamic and economic performance.

A comprehensive steady-state model encompassing thermodynamic and economic analysis was developed to evaluate the system behavior. In the proposed configuration, unreacted fuel in the SOFC anode exhaust is combusted using oxy-fuel technology, yielding a CO₂-concentrated flue gas suitable for carbon capture while simultaneously upgrading waste heat quality. The high-temperature flue gas is then recovered through an advanced cascaded heat exchanger network, sequentially enabling cathode air preheating, endothermic methane reforming, and high-pressure steam generation. This steam serves as the thermal driving source for the LiBr absorption heat pump to meet heating demands. A detailed parametric sensitivity analysis was conducted to investigate the effects of the steam-to-carbon ratio, SOFC operating temperature, and fuel utilization factor on key performance indicators.

Simulation results show that increasing the steam-to-carbon ratio monotonically reduces both SOFC electrical efficiency and overall thermal energy utilization efficiency, whereas the coefficient of performance (COP) of the absorption heat pump remains stable at approximately 1.72. Higher SOFC operating temperatures significantly improve electrochemical kinetics and flue gas quality, thereby enhancing both electrical and thermal performance. A clear trade-off is observed with fuel utilization: higher fuel utilization factor increases electrical output but diminishes the availability of high-grade heat for downstream recovery. Under optimized conditions (with the steam-to-carbon ratio of 2, temperature of 1 000 ℃, and fuel utilization ratio of 0.85), the system achieves an electrical efficiency of 52%, an exergy efficiency of 56.6%, and an overall thermal energy utilization efficiency of 100.54% (defined on the basis of the fuel’s lower heating value, including all recovered thermal energy). Compared to a conventional natural gas-fired CHP benchmark, the proposed system improves the thermal utilization efficiency by 20%, and increases the exergy efficiency by 2.6%. Economic evaluation yields a levelized cost of exergy of 0.102 6 dollars/(kW·h) and a dynamic payback period of 8 years under current industrial energy pricing.

This coupled system significantly improves the energy utilization efficiency and comprehensive performance through the optimization of the energy cascade utilization mode. It demonstrates substantial economic feasibility and potential for engineering applications. The identified influence mechanisms of key parameters provide a theoretical foundation for the optimal design and operational control of such systems.

The carbon capture pretreatment system faces challenges such as high energy consumption, unstable purification efficiency, and significant fluctuations in SO₂ absorption efficiency due to variations in pH value of washing solution. This study proposes a hybrid modeling method combining mechanism models with data-driven by taking the carbon capture pretreatment system in a power plant as the research object.

By integrating chemical reaction kinetics and decision tree algorithms, the model is implemented in Python to predict key parameters accurately, including the pH value of the washing solution and the SO₂ mass concentration at the system outlet.

The model yields a correlation coefficient of 0.85 and 0.80 for the pH value of the washing solution and the SO₂ mass concentration at the system outlet, respectively. The values fall within an acceptable error band, indicating the proposed model has good simulation performance. Moreover, a sensitivity analysis driven by baseline plant data further reveals that the model faithfully reproduces the system response to perturbations in inlet flue-gas temperature, liquid-to-gas ratio, and alkali feed rate.

These outcomes furnish a quantitative foundation for subsequent optimization of the CO₂-capture pretreatment system, offering clear avenues for energy minimization and robust steady-state operation.

In the context of achieving the “dual-carbon” goals in the new era, coal-fired cogeneration systems are required to be highly efficient, flexible, and low in pollution and carbon emissions.

To tackle these challenges, this study proposes a novel system that integrates a supercritical CO₂ cycle with split-flow heating and low-temperature regeneration (SR-SCO₂-CHP), an ultra-low emission (ULE) flue gas control module, and a vacuum temperature swing adsorption (VTSA) carbon capture module (denoted as the SR-SCO₂-CHP-ULE-VTSA system). A system using monoethanolamine (MEA) for carbon capture (SR-SCO₂-CHP-ULE-MEA) serves as the benchmark for comparison. A comparative exergy analysis is conducted.

The results demonstrate that the proposed system achieves superior exergy efficiency across all electrical loads, because the exergy loss of the VTSA carbon capture submodule is less than one-third of that of the MEA. The exergy losses of MEA mainly occur in the absorption tower and desorption tower, which account for 80% of the total exergy losses of the carbon capture submodule. However, the exergy losses of VTSA adsorption & desorption tower and the pressure machine are relatively large, accounting for more than 60% of the total exergy losses of the carbon capture submodule. At full load, its exergy efficiency reaches 39.84%, significantly outperforming the benchmark system’s 35.16%. Furthermore, the proposed system enables effective thermo-electric decoupling through adjustments in the heat split ratio (x₁) and the split ratio of CO₂ turbine driving vacuum pump (x₂). The exergy efficiency of the system decreases as the split ratio x₁ and x₂ increase under any electrical load, and the optimal split ratios of x₁ and x₂ increase as the electrical load decreases. At 100% electrical load, the optimal values for x₁ and x₂ are 0.52 and 0.14, respectively. The carbon reduction capability of the proposed system is also remarkable. Across the electrical load range from 100% to 30%, the carbon reduction increases from 11.9 g/(kW·h) to as high as 85.3 g/(kW·h), demonstrating a significant advantage over the benchmark system.

This work confirms the SR-SCO₂-CHP-ULE-VTSA system as a promising solution for highly efficient and low-carbon coal-fired cogeneration. It should be noted that in terms of economic performance, the initial investment of the carbon capture module of the SR-SCO₂-CHP-ULE-VTSA system is closely related to the performance of the adsorbent material, and further optimization of the adsorbent is required to reduce equipment size and cost. Additionally, in terms of operation, its carbon capture module has a complex structure and high requirements for multi-tower operation switching, so its technical maturity needs to be further improved to promote its industrial application.

This study aims to enrich the experimental study of the ORC using mixture working fluids and analyze its transient and steady-state operating characteristics.

A 4-kW organic Rankine cycle (ORC) prototype using R236fa/R123 was tested to obtain the transient and steady-state operating data.

The results of the ORC system at different mixture concentrations reveal that the operation characteristics of the ORC with mixed working fluids are consistent with those using a pure working fluid. The adjustment of the working fluid mass flow rate significantly affects the system output power, while it has a limited impact on the thermal efficiency. The ORC system operates relatively stable with the variation in the mixture concentration, as it has a minimal effect on both the output power and thermal efficiency. With the increase in the R236fa mass fraction, the expander inlet pressure is stable while its outlet pressure gradually increases, resulting in high pressure ratios. This phenomenon indicates that adopting the expander with a larger internal volume ratio can optimize the ORC performance. The trade-off between the exergy destructions of the evaporator and condenser at different mixture concentrations is the main factor determining the system performance. The temperature glide caused by the condenser pressure drop limits the attribution of the mixture working fluid to optimize the system performance.

In the design and operation of mixed-working-fluid ORC systems, it is crucial to consider the matching of the condenser pressure drop and the working fluid inherent properties.

In practical energy and chemical engineering systems, pipeline layouts often exhibit complex multi-directional configurations due to equipment arrangement, spatial constraints, and process requirements, rather than simple straight horizontal or vertical sections. This is particularly evident in applications such as compact heat exchangers for supercritical carbon dioxide (S-CO₂) Brayton cycles, nuclear reactor cooling circuits, and chemical transport pipelines, where the working fluid frequently undergoes abrupt changes in flow direction. Among these configurations, the L-shaped bend, a classic directional-changing structure that connects horizontal and vertical pipe sections, is especially common and plays a crucial role in achieving spatial redirection of the working fluid. Therefore, investigating the heat transfer characteristics of S-CO₂ in L-shaped bends is of significant importance. This study aims to investigate the effect of buoyancy-induced density stratification in a heated horizontal section on the subsequent heat transfer in a vertical upward flow under different experimental parameters.

An experimental system with high expandability was established, featuring a single-cycle S-CO₂ heat transfer test platform utilizing stainless steel circular pipes with adjustable lengths and bend angles. Experiments were conducted to study the flow and heat transfer characteristics of S-CO₂ inside a horizontal-to-vertical L-shaped turning pipe.

The experimental results reveal two distinct types of “asymmetric heat transfer deterioration” in the turning pipe: one characterized by asymmetry in the severity of deterioration, and the other by asymmetry in its location. When the wall heat flux is increased, wall temperature peaks indicating heat transfer deterioration appear in the vertical section, with unequal peak values on the two sides, representing asymmetry in severity. A further increase in wall heat flux shifts the deterioration position toward the inlet, while the enthalpy at which deterioration initiates remains unchanged, indicating that the wall heat flux does not affect the onset enthalpy of deterioration. When the heat flux is raised sufficiently for the deterioration to advance to the inlet of the vertical section, the wall temperature peak on the inner side occurs earlier than that on the outer side, demonstrating asymmetry in the location of deterioration.

The study demonstrates that asymmetry in severity originates from non-uniform cross-sectional mass flow distribution caused by temperature stratification extending from the horizontal section. In contrast, asymmetry in location occurs under high-temperature and high-heat-flux conditions due to the earlier fulfillment of deterioration criteria within the inner-side boundary layer. This research elucidates the coupling effect between buoyancy and flow redirection in L-shaped pipes, providing an experimental basis for the design of related heat exchange equipment.

To investigate the effects of biomass gas co-firing on combustion stability and in-furnace parameters under low-load conditions, a 660 MW tangentially fired boiler was taken as the research object to carry out the study. A stability index was proposed, and a combined approach of numerical simulation and artificial neural network (ANN) was employed.

Comparative analysis was conducted between pure coal and co-firing conditions at loads of 100%, 70%, 50%, and 30%.

The results show that the deviation of the temperature stability coefficient (M_T) under co-firing is less than 3.9%, indicating stable combustion at low load conditions. When the unit load decreases from 100% to 70%, the average temperature in the main combustion zone drops by 147.87 K for pure coal and 69.37 K for co-firing, indicating a slower temperature decay. At 30% load, the NO_x volume fractions in the reduction and burnout zones under co-firing are 0.051 2% and 0.044 4%, which are lower than 0.093 3% and 0.078 6% under pure coal combustion condition, with smaller fluctuations of other parameters. Furthermore, an artificial neural network (ANN) model was developed to describe the complicated relationships among in-furnace parameters, and the results show that the regression coefficients R² for temperature, CO₂ volume fraction, and NO_x volume fraction predictions are all greater than 0.96 in both pure coal and co-firing conditions.

This study provides support for optimization and prediction of low-load operation in biomass gasification co-firing boilers.

To address the issues of low reheated steam temperature and local overheating of platen superheaters (PSH) during low-load operation of a 660 MW ultra-supercritical tangentially fired once-reheat boiler, this study proposed a wall-mounted flue gas recirculation (FGR) arrangement in the burner region. The aim was to synergistically raise reheated steam temperature and suppress PSH overheating while maintaining combustion stability.

Numerical simulation was performed at 40% rated load to optimize the proposed layout. First, the baseline case and corner-mounted and wall-mounted concentrated FGR arrangements were compared. Subsequently, the feasibility of wall-mounted grouped injection was investigated.

The results indicated that: corner-mounted FGR significantly increased the ignition distance of pulverized coal jets, which adversely affected low-load combustion stability. Both fire-side and rear-side concentrated FGR increased the heat absorption of the high-temperature reheater, but neither could simultaneously mitigate PSH local overheating. Fire-side grouped FGR substantially enhanced heat absorption of the reheater but still carried a risk of PSH overheating, whereas rear-side grouped FGR reduced the overheating risk but yielded only limited reheater improvement. A combined grouped arrangement, in which flue gas was injected through the two lower layers on the fire-side wall together with the upper layer on the rear-side wall, increased the heat absorption of the reheater by 18.9%, effectively mitigated local overheating of the PSH, and maintained stable combustion.

These findings provide design and optimization references for safe, flexible, and efficient boiler operation across wide load ranges in next-generation coal-fired power plants.

The low-temperature (–20~ –40 ℃) oxidation adsorption of multiple pollutants from coal-fired flue gas onto activated carbons enables their integrated removal, which has promising application prospect and environmental benefits.

This article studied the adsorption processes of NO and SO₂ by four activated carbons (graded-pore activated carbon, coal-based activated carbon, and two coconut shell-based activated carbons) in inert atmosphere and simulated flue gas under low temperature conditions of –20 ℃.

The experimental results showed that in an inert atmosphere, the adsorption performance of the four activated carbons for NO was weak, with a saturated nitrogen capacity of less than 0.07 mg/g, and the saturated sulfur capacity for adsorbing SO₂ was 31.70~57.07 mg/g. In simulated flue gas conditions, the presence of O₂ increased the saturated nitrogen capacity of activated carbons by three orders of magnitude and the saturated sulfur capacity by 2~5 times. The optimal coconut shell activated carbon-2 had a saturated nitrogen capacity of 175.70 mg/g and a saturated sulfur capacity of 320.65 mg/g. Density functional theory (DFT) calculations show that the adsorption binding energies of NO, SO₂, and their oxides on the zigzag edge carbon model follow the order of NO₂> SO₃> SO₂> NO. After NO and SO₂ are oxidized by O₂ into NO₂ and SO₃, their adsorption on activated carbon surfaces is significantly enhanced.

The research results can provide an important theoretical basis for the integrated adsorption and removal of NO and SO₂ in coal-fired flue gas under low temperature conditions.