To enhance the peak shaving performance of heating units, a new process for double-reheat heating unit integrating five thermo-electric decoupling technologies, namely cylinder cut-off, high-/medium- and low-pressure bypass heating, heat pump, hot water tank and electric boiler, has been proposed. A detailed thermodynamic model of the system was established, and the peak shaving performance of the novel power plant is compared with that of a reference power plant. Relying on the electricity market, a systematic economic operation strategy was put forward, and a techno-economic analysis was performed. The results show that, when the heating demand is 1 460 MW, the reference plant cannot meet the heating demand under the extraction-condensing condition. Under the cylinder cut-off condition, the load regulation range of the reference plant is 77.9% to 80.0% of the rated load, and it almost loses its load regulation ability. While under the cylinder cut-off + bypass condition, the load regulation range of the reference unit is 50.0%~80.0%, and its peak regulation ability has been improved. For the novel plant, in the same heating demand, the load regulation range has been expanded to 0~80.0%, and zero-power grid connection can be achieved especially during the low electricity demand period. Compared with the reference plant, the novel plant can reduce the power output during peak shaving periods by 107 600 MW·h per month, save 17 700 tons of coal, achieve an annual net profit increase of approximately 68.988 million yuan during the heating season, and have a payback period for new equipment investment of 5.6 years, demonstrating significant economic benefits.

Induced draft fans in power plants run under complex and harsh conditions, where various faults often occur. These faults not only affect the fans’ safety and stability but also pose an indirect threat to normal operation of the boiler system. Thus, early fault monitoring and prompt, accurate diagnosis are essential to ensure the power plants’ operation efficiency and safety. Common fault types of forced draft fans and their potential effects are analyzed and summarized. Three typical fault types and their causes are explained in detail. Fault monitoring and diagnosis methods are elaborated from both quantitative and qualitative perspectives, including measurement point installation and data processing techniques. Each method’s advantages and disadvantages are analyzed, and suitable applications for different fault types are discussed, along with proposed targeted improvement measures. Finally, key challenges of fault diagnosis are identified, and future development directions for forced draft fans’ fault monitoring and diagnosis are outlined.

Proton exchange membrane (PEM) electrolysis for hydrogen production has broad application prospects, but it still has disadvantages such as high equipment cost and insufficient durability. Optimizing the flow channel can improve the uniformity of water and heat distribution in PEM and extend the service life of the electrolyzer. To enhance the performance of PEM, a three-dimensional wavy flow channel model was designed and simulated using COMSOL simulation software. The polarization curves, distribution of reactants and products, and temperature distribution of electrolyzers with different frequency wavy structures were studied, and the influence of flow rate changes due to the addition of wavy structures on the performance of the electrolyzer was explored. The results show that, compared with the conventional rectangular flow channel, the electrolyzer with wavy flow channels has significantly enhanced the heat and mass transfer effects and got better polarization performance. When the wavy frequency is 1.0, the current density of the electrolyzer increases by 2.1%, and the average gas volume fraction in the anode catalyst layer decreases by 3.7%, achieving the best overall performance. This study can provide certain references for the flow channel design of PEM electrolyzers.

Researches on the application of calcium carbide residues in carbon fixation is mainly conducted at a macroscopic level, with limited studies exploring the carbon fixation mechanism of calcium carbide residues from a microscopic perspective. It remains unclear whether the various impurities present in calcium carbide residues adversely affect the CO2 adsorption activity of this material. To solve this problem, the phase compositions of calcium carbide residues before and after calcination were analyzed using X-ray diffraction, and density functional theory was employed to construct the most stable low-index crystal planes such as CaO-CaO (0 0 1), CaO-Fe₂O₃ (0 0 1), CaO-Al₂O₃ (1 1 1), CaO-MgO (1 0 0) and CaO-SiO₂ (0 0 1). Moreover, the adsorption properties of CaO clusters on various impurity-supported surfaces and doped surfaces were simulated, along with the capabilities of these surfaces to support the adsorption of CO₂ molecules. The adsorption energy, charge transfer, density of states, and differential charge density of each adsorption system were analyzed. The results indicate that SiO₂ does not significantly influence the adsorption process. The four different supported surfaces enhance the anti-sintering performance of calcium carbide residues, with the strength of the effects ranked as follows: Al₂O₃ > Fe₂O₃ > MgO > CaO. The adsorption energy on the Al₂O₃ supported surface is –8.82 eV, which is 1.24, 2.45, and 3.69 times greater than that on the Fe₂O₃, MgO, and CaO supported surfaces, respectively. The capacities of the various surfaces to support CaO in the adsorption of CO₂ are similar, with the electron transfer quantities for the CaO clusters adsorbing CO₂ on the CaO, Fe₂O₃, Al₂O₃, and MgO supported surfaces being 0.67, 0.68, 0.71 and 0.66 e, respectively. The presence of impurities can effectively improve the anti-sintering performance of calcium carbide residue as a CaO-based material, but can not significantly enhance the CO₂ adsorption effect. Compared with the pure CaO supported surfaces, the doped surfaces exhibit a stronger capability for CaO to adsorb CO₂, with adsorption energy and electron transfer quantities being –4.92 eV and 0.71 e, respectively.

The complex and variable meteorological conditions have a significant impact on operational characteristics of indirect air cooling systems. To enhance the cooling performance of indirect air cooling systems, an optimized regulation strategy for circulating water in indirect air cooling systems is proposed. By taking the indirect air cooling unit in a power plant as an object and considering the influence of surrounding buildings, the optimization distribution of circulating water flow in each sector of the air cooling heat exchanger is numerically studied. Firstly, a one-dimensional thermodynamic model of the indirect air cooling unit and a three-dimensional numerical model of the indirect air cooling tower are established and coupled for numerical calculation. Secondly, the influence of different meteorological conditions on the operating back pressure of the unit and the flow and heat transfer characteristics of the cooling tower is analyzed. As a result, the economic back pressure variation law of the unit under specific environmental meteorological conditions is obtained. Finally, constrained by the economic back pressure of the unit, the circulating water flow rate of each sector of the indirect air cooling heat exchanger is optimized according to the so-called heat load matching principle, which enhances the flow and heat transfer performance of the indirect air cooling system. The research results indicate that as the ambient temperature increases, the economic back pressure will also increase accordingly. When the ambient wind speed increases, the economic back pressure of the unit also increases. By optimizing the distribution of circulating water flow in each sector of the indirect air cooling heat exchanger, the uniformity of the outlet water temperature in each sector can be improved, the average outlet water temperature of the intercooled tower can be reduced, the total circulating water flow can be decreased, and the operating economy of the unit can be improved. This study can provide theoretical basis and reference for optimizing the operation of indirect air cooling units.

With the increase in parameters and capacity of newly built coal-fired units, the expansion of critical long-distance and large-diameter pipelines due to high parameters becomes more significant, making the design of supports and hangers particularly important. In a case involving a 2×660 MW ultra-supercritical unit, the diagonal brace of a rigid hanger tripod supporting the main steam pipeline buckled, resulting in a pipeline subsidence of nearly 130 mm. A comprehensive inspection of the pipeline supports and hangers was conducted, along with mechanical analysis of the statically indeterminate tripod structure and stability analysis of the diagonal brace. The study concluded that the failure of the diagonal brace and the pipeline sinking were primarily caused by an incorrect design of the radial horizontal restraint gap. Additionally, the excessive constant force of the constant hanger also contributed to the damage of the diagonal brace. This research not only analyzed the design flaws of the pipeline supports and hangers, but also proposed an engineering solution to optimize the restraint gap, which was validated on-site. A rectification plan involving horizontal limit adjustment and pipeline lifting was developed and implemented, successfully restoring the pipeline to its designed state and resolving the issue. This problem is highly representative in the construction of large-scale power units and should draw the attention of designers to avoid similar issues in future projects.

The formation and emission of SO₃ in coal-fired flue gas not only pose significant threats to atmospheric environments and human health but also negatively affect power plant operations. Injecting alkaline sorbents into flue gas has proven to be an effective method for SO₃ removal. The removal efficiency of SO₃ by injecting Na₂CO₃ and Ca(OH)₂ absorbents was investigated under different flue gas conditions, and the removal performance was compared with that of the blended absorbents. Moreover, the physicochemical properties of the alkaline absorbents before and after the reaction were characterized using SEM, XRD, FT-IR, and XPS techniques. Based on experimental data and characterization results, the gas-solid reaction model were proposed to elucidate the mechanisms of SO₃ removal by Na₂CO₃ and Ca(OH)₂. Furthermore, the adsorption process of Na₂CO₃ on SO₃ was simulated, and the adsorption energy was calculated and compared with that of Ca(OH)₂. The results showed that, Na₂CO₃ demonstrated superior SO₃ removal efficiency compared with Ca(OH)₂, and the removal efficiency was enhanced by increasing the reaction temperature, SO₃ mass concentration, absorbent stoichiometric ratio and residence time. The blended absorbent with a molar ratio of Ca:2Na:S=5.00:1.25:1.00 achieved an SO₃ removal efficiency of 86.07% under practical operating conditions at a low cost. The findings indicated that the gas-solid reaction between Na₂CO₃ and SO₃ followed the shrinking core model, while the reaction between Ca(OH)₂ and SO₃ adhered to the grain model. The adsorption energy of SO₃ on Na₂CO₃ was higher than that on Ca(OH)₂. This study can provide theoretical insights and technical support for efficient and cost-effective removal of SO₃ from coal-fired flue gas.

The deposition of corrosion products in orifice of the steam generator of high temperature gas cooled reactor (HTGR) in nuclear power units threats to safe operation of the unit seriously. To effectively inhibit the deposition of corrosion products in the orifice, the influence of dissolved oxygen in water on the orifice deposition rate was studied under the simulated water condition in the secondary loop of the HTGR. Moreover, the variation law of ZETA potential with dissolved oxygen in iron solution was also studied. It is found that the deposition rate of corrosion products in the orifice area is extremely sensitive to the dissolved oxygen, it decreases with the increase of dissolved oxygen concentration in water. Secondly, over high pH value is not conducive to the inhibition of orifice deposition, which is mainly due to the effect of dissolved oxygen and pH value on the ZETA potential. The wall current electrokinetic effect plays an important role in the orifice deposition, and increasing the concentration of dissolved oxygen in feed water is an effective method to restrain the orifice deposition and clogging in the steam generator of HTGR.

The coordinated operation of coal-fired power plant (CFPP) with large-scale energy storage systems can effectively regulate the flexibility of power system and smooth the renewable power output. A gas-liquid interconversion carbon dioxide energy storage system coupled with a CFPP was proposed, which recovers compression heat using condensate and feedwater of CFPP and preheats turbine inlet CO2 through drain water, realizing thermal decoupling of charge and discharge processes without heat storage devices. Based on the mathematical models of the coupling system, the system coupling schemes were designed and optimized, and a comparative performance analysis with stand-alone system was conducted. The results show that, the compression heat cascade recovery boosts the exergy efficiency of last-stage intercooler from 73.3% to 89.6%, and the exergy efficiency of the first-stage preheater improves from 53.1% to 89.7% by replacing extraction preheating with drain water cascade preheating. In the optimal coupling scheme, the system energy storage efficiency improves from 63.6% to 76.8% compared to the stand-alone system, and the levelized cost of electricity reduces from 0.130 dollar/(kW·h) to 0.093 dollar/(kW·h), with a slight reduction in round-trip efficiency to 63.2%. The turbomachinery and heat exchangers, representing the main contributors to the total system exergy destruction and investment cost, are key components in improving thermodynamic and economic performance. Increasing the discharge power to 90 MW reduces the levelized cost of electricity to 0.089 dollar/(kW·h) and expands the peak regulating range to 86.4%~107.6%.

Thermochemical thermal storage has attracted wide attentions because it has high thermal density heat storage and can realize seasonal thermal storage and long-distance transportation. The CaCO₃/CaO reaction system, as one of the most promising thermochemical heat storage materials, has problems such as particle aggregation and sintering as the number of heat storage cycles increases, and the material gradually loses its activity. To solve this problem, composite CaO materials doped with Al₂O₃ or CeO₂ were synthesized by the template method. The microstructure of the materials and the effect of chemical doping on the cyclic stability of the composite CaO materials were investigated by means of characterization tests such as X-ray diffraction (XRD), scanning electron microscopy (SEM) and synchronous thermal analyzer (STA). The effect of chemical doping on exothermic reaction temperature range of the composite CaO materials was analyzed. The results show that, the CaO prepared by the template method has a richer pore structure and a superior cycling stability than the CaO obtained by decomposition of CaCO₃. When the doping molar ratio of CaO to Al₂O₃ is 100.0:2.5 (Ca:Al), the composite has the best cycling stability. After 30 cycles, the effective conversion rate decays by only about 7.1% from 0.70 to 0.65 and the exothermic energy density is 2 057 kJ/kg. The cyclic stability of the composite is better than that of CaO when the molar ratio of CaO to CeO₂ doping is 100.0:10.0 (Ca:Ce=100.0:10.0). It is found that doping with Al₂O₃ decreases the onset temperature of the exothermic reaction of the CaCO₃/CaO reaction system, whereas CeO₂ increases the onset temperature.