A 300 MW supercritical carbon dioxide (S-CO₂) Brayton cycle oxyfuel power generation system is designed, and a simulation model is constructed using process simulation methods to study the effects of key operating parameters (such as the primary dry cycle flue gas ratio, the economizer side split ratio, the cold primary air temperature and the high-pressure turbine inlet pressure) on the system’s thermal performance indexes. The effects of key operating parameters such as primary dry cycle flue gas ratio, economizer side split ratio, cold primary air temperature and high-pressure turbine inlet pressure on the system thermodynamics were investigated, and the thermal characteristics of the generating unit were revealed. The results show that, the boiler efficiency decreases with the increase of the proportion of primary dry-cycle flue gas, and when the proportion of primary dry-cycle flue gas reaches 50%, the net electric efficiency of the system is the highest, which is 42.93%. The boiler efficiency rises at first and then decreases with the increase of the coal economizer-side shunt ratio, and the net electric efficiency of the system reaches the highest (42.86%) when the coal economizer-side shunt ratio is 11%. With the increase of cold primary air temperature, the boiler efficiency keeps increasing, and the rising trend slows down and stabilizes at 99.29% at temperatures higher than 65 ℃, and the net electric efficiency of the system keeps increasing and reaches 43.06% at 95 ℃. With the increase of high-pressure turbine inlet pressure, the boiler efficiency firstly rises and then decreases, and reaches the maximum value of 99.35% at 29.5 MPa, and the net electric efficiency of the system reaches the optimal value (43.66%) at 29.0 MPa.

Due to the significant volatility and randomness of wind power data, low prediction accuracy is often observed with a single model in wind power prediction. To overcome this, an ultra-short-term wind power prediction method is introduced, based on modal decomposition and a combined neural network model. Firstly, the wind power data are processed based on the improved fully integrated empirical modal decomposition and sample entropy, which decomposes the unsteady series into smoother sub-sequences and reconstructs the high-frequency oscillatory component and low-frequency smooth component synchronously. Secondly, a hybrid prediction model for wind power based on an adaptive sparse self-attention mechanism is constructed. For the high-frequency oscillatory component with high complexity, the adaptive sparse Transformer model is used to fully explore the fluctuation information. For the low-frequency stationary components, the sequence features are fully extracted by the bidirectional gated recurrent unit model. Finally, the final prediction outcomes are derived by overlaying the forecast results of each component. Test was performed with actual data from a wind farm in Shandong, and the results show that, compared with other commonly used models, the proposed model’s root mean square error and average absolute error has decreased by 2.644 MW and 2.42 MW, and the coefficient of determination has a notable 18.2% increase, implying it has a good prediction performance.

Supercritical carbon dioxide (S-CO₂) in horizontal tube with circumferential heating and semicircle heating is investigated numerically based on pseudo-boiling theory. The phase distribution of supercritical fluid in the tube is obtained. It is found that the heat transfer performance of supercritical fluid is determined by the thickness of vapor-like film on tube, which can be characterized by supercritical K number, involving the balance between evaporation momentum force and inertia force. The increasing thickness of local vapor-like film can trigger heat transfer deterioration. There are both overshoot wall temperature along the flow direction and non-uniform wall temperature in the circumferential direction. The emerging condition of heat transfer deterioration can be accurately predicted by supercritical boiling number SBO. Under working conditions where the pressure p is 8~20 MPa, and the range of mass flux G and heat flux density q_w is 300~1 300 kg/(m²·s) and 42~500 kW/m² respectively, compared with the circumferential heating tube, the semicircle heating tube behaves thinner vapor-like film to enhance the heat transfer performance. The critical SBO to heat transfer deterioration rises from 6.179×10^–4 to 9.798×10^–4. Furthermore, the semicircle heating tube keeps more uniform vapor-like film, the maximum temperature difference between the top and bottom generatrix of tube wall changes from 116.3 K to 57.1 K. Due to the ability to repress heat transfer deterioration and non-uniform wall temperature, semicircle heating is recommended to ensure the safe operation of horizontal heat exchangers in advanced supercritical CO₂ system.

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.

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.

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.

The sterilization effect of chlorine-containing disinfectants does not hinge on the total available chlorine concentration, but rather on the concentration of hypochlorous acid (HClO) molecules. To reduce the cost of circulating water sterilization in thermal power plants, HClO solution was used to sterilize circulating water. The HClO solution was prepared from sodium hypochlorite (NaClO) solution, CO₂ and pure water by non-electrolytic method, and experimental study on application performance (including stability and sterilization effect) of the HClO solution was conducted. The results showed that, the mass concentration of HClO in NaClO solution was extremely low, the mass fraction of HClO to available chlorine was only 0.690%~0.012% in NaClO solution with mass concentration of available chlorine in the range of 100~2 000 mg/L, which could be increased to 94.91% by reacting with CO₂, thereby improving the sterilization efficiency. When 30, 60, 80, and 90 mg/L stabilizer were added, the decomposition rate of HClO solution with mass concentrations of 500, 1 000, 1 500 and 2 000 mg/L could meet the requirements for a shelf life of one year of the Disinfection Technical Specification. When the dosage of NaClO and HClO (calculated by available chlorine) was 5 mg/L and 0.06 mg/L，the sterilizing time was 120 min and 15 min, the sterilizing rate could reach 90%, and it can be seen that HClO was more economical and efficient for sterilization. HClO solution can reduce the cost of circulating water bactericides in thermal power plants by more than 55% compared with that of conventional NaClO.

Data quality is a key factor affecting the application effectiveness of optimization models of denitrification system operation. In response to the problems of lagging and poor representativeness of monitoring parameters in denitrification system operation, a denitrification performance parameter dimension reduction technology suitable for real-time performance monitoring is developed. The utilization rate of reducing agents that can reflect the denitrification ability of the denitrification system itself is set as the monitoring and evaluation parameter for denitrification system operation status, to improve the efficiency of data generation. Based on this, an optimization method for denitrification system operation that can eliminate adjustment delays is established, and an identification technology for typical abnormalities in denitrification system operation is constructed to guide the economic, safe, stable, and standard operation of the denitrification system. This technology has been implemented and applied in a 1 000 MW coal-fired unit at different loads. The results show that, the denitrification system operation guided by the utilization rate of reducing agents reduces the unit consumption of urea solution by 1.5%~8.4% and the ammonia escape at the denitrification system outlet by 10.7%~27.0%, and all of the ammonia escape at different loads meets the general control value of ammonia escape rate. The variation range of NO_x emission mass concentration in the exhaust reduces from 44.5~58.3 mg/m³ to 9.2~10.6 mg/m³, and the distribution deviation significantly decreases from 59.2%~75.2% to 21.4%~25.1%, which is more conducive to the automatic and stable control of the denitrification system.

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.