The vibration mechanism and characteristics of stator housing in nuclear power turbo-generators under different excitation forces are investigated, and an analysis and treatment method for the stator housing vibration fault is proposed. Moreover, analysis and verification is conducted by using three nuclear power turbo-generator units as examples. The results show that, the main cause of excessive stator housing vibration is the structure resonance resulting from the natural frequency of the stator housing being close to the rotating frequency or its double. The structure resonance caused by rotor excitation force can be controlled in two ways: by reducing the excitation force through field dynamic balance, or by adjusting the natural frequency of the stator housing through adjustment of the stator bottom bracing load distribution. Performing on-site dynamic balancing can effectively reduce the rotor excitation force. Adjusting the natural frequency of the stator housing can be realized through load distribution adjustment of the stator feet. However, due to the limited adjustment range of the magnetic pulling force, it is necessary to control the structure resonance caused by magnetic pulling force by adjusting the natural frequency of the stator housing. To prevent structure resonance of the stator housing, it is important to adjust the stator bottom bracing load distribution during installation or maintenance of the turbo-generators to keep the natural frequency of the stator housing away from the rotating frequency and electromagnetic force frequency.

In order to investigate the effects of oxygen addition amount and type of gasification medium on coal gasification efficiency as well as the optimization of integrated gasification combined cycle (IGCC) power system, a simulation analysis is carried out by baking two kinds of coals with significant differences in oxygen content as the examples. Firstly, based on the equilibrium reaction model, the influence of oxygen carbonation stoichiometric ratios (considering the oxygen content of different coal types) on gasification characteristics for different coal types is compared. Then, the gasification characteristics are analyzed and optimized when CO₂ and steam are added as gasification media respectively. On this basis and considering CO₂ capture, a novel IGCC power cycle system with CO₂-assisted gasification, pure oxygen combustion and partial gas recirculation is proposed and analyzed, and the gas turbine model is simulated and optimized. The results show that, the coal gasification performance is the best when the total oxygen-carbonation stoichiometric ratio is around 0.47. Under this condition, adding CO₂ as the gasification medium can increase the efficiency of cold gas by about 1.3%, compared with that of the conventional way that adding steam as the gasification medium. Compared with the conventional IGCC power system with pre-combustion decarbonization, the net power efficiency of the proposed system increases by about 1.5% and the exergy efficiency increases by 1.7%, which provides a new idea for designing a low-carbon and efficient IGCC power generation system.

Partial heating supercritical carbon dioxide (S-CO₂) power cycle system is proven to be one promising option for waste heat recovery. By using LiBr-H₂O and NH₃-H₂O as working fluids, two types of novel combined power systems consisting of a parting pre-heating S-CO₂ cycle and different absorption power cycle (APC) systems are proposed. The detailed mathematical models of the proposed parting heating S-CO₂/APC systems are built and verified. Based on the results of single- and multi-objective optimization, the performances of the proposed S-CO₂/APC system and the standalone S-CO₂ system are compared from the perspective of thermodynamics and economics. The single-objective optimization study reveals that the net power output and net efficiency of the S-CO₂/LiBr-H₂O system and the S-CO₂/NH₃-H₂O system increases by 7.40% and 4.30%, respectively, compared with the standalone S-CO₂ system. The multi-objective optimization results show that, the S-CO₂/LiBr-H₂O system and S-CO₂/NH₃-H₂O system can obtain improvements of 7.94% and 5.13% in net efficiency as well as promotion of 12.35% and 9.02% in the specific investment cost respectively, indicating that the S-CO₂/LiBr-H₂O system has a greater potential. Exergy loss analysis reveals that the main exergy loss exists in the coolers and the heaters, and the proposed S-CO₂/APC systems can significantly reduce the exergy loss in the S-CO₂ cooler by about 45%.

In the context of carbon peak and carbon neutrality, the development of coal-biomass coupling power generation is one of the important ways to accelerate the transformation and upgrading of electric power and realize low-carbon development of coal power. A coal-fired power generation system directly coupled with biomass combustion was designed for a 300 MW circulating fluidized bed (CFB) boiler, and the combustion characteristics of directly firing biomass with coal were studied by using the system. The results show that, this biomass direct combustion coupling system could run stably and reliably. When wood pellets was co-fired in the CFB boiler, with the increase of wood pellets’ blending ratio, the fly ash carbon content of the mixed fuel decreased, the CO emission reduced, and the burnout performance of the mixed fuel improved. After optimization on the boiler combustion and air distribution, the NO_x emission was slightly lower than that of pure coal burning. The pollutants test under typical conditions showed that, after adding wood pellets, the dioxin emission from boiler flue gas was 0.008 8 ng TEQ/m³ (standard condition, ϕ(O₂)=11%), and the dioxin emission in fly ash was 0.020 6 ng TEQ/m³. The total emission of heavy metals and harmful trace elements such P, As and Se from fly ash was 32.121 mg/l, and that from the bottom slag was 3.918 mg/L. The emission of harmful substances like dioxins and heavy metals in flue gas and fly ash all met the emission limits of national environmental protection standards.

There is a delay in NO_x measurement for flexible operations in coal-fired power plants, which leads to a delayed response in ammonia injection control system of selective catalytic reduction (SCR) reactor, resulting in potential over or under-injection of ammonia and significant fluctuations in NO_x mass concentration at outlet of the SCR reactor. To enable proactive adjustment of ammonia injection and considering the interconnected factors influencing the NO_x emissions from coal combustion, a prediction model for NO_x mass concentration at the SCR reactor inlet is proposed based on convolutional neural networks (CNNs) and long short-term memory neural (LSTM) networks. By using operational parameters from a 330 MW coal-fired power plant, a Pearson coefficient method is employed to calculate the correlation between feature variables. Significant features are extracted to define the model input matrix and output matrix. The random search algorithm is used for hyper-parameters optimization to enhance predictive performance. The SHAP algorithm is then applied to interpret the model structure and explain the black-box model. Finally, the control effects of model with NO_x concentration prediction is verified through Simulink simulation. The results indicate that, the CNN-LSTM prediction model demonstrates higher predictive accuracy for the variable NO_x mass concentration at the SCR reactor inlet during the frequent load fluctuations. It can provide feedback to the ammonia injection control system of 25 seconds in advance. The optimized ammonia injection control strategy not only reduces the standard deviation between the NO_x mass concentration at the SCR reactor outlet and the set value by 28%, but also improves the response speed of NH₃/NO_x regulation, reducing the maximum ammonia slip by 22%. The research findings can provide guidance for intelligent SCR denitration system and combustion optimizing operating during flexible operation of coal-fired power plants.

The utilization hours of thermal power units continue to decline, and peak shavings become more frequent. Under this background, the existing ammonia injection mixing technology can no longer meet the new normal needs of coal-fired power plants, and ultra-low emissions put forward higher requirements for uniformity of the NH₃/NO_x molar ratio distribution at the SCR reactor inlet. The grid-type ammonia injection grid (AIG) and static mixer are optimized through CFD numerical simulation and physical model test. The design method and an anti-blocking nozzle are proposed to ensure the uniformity of ammonia distribution, adjustment flexibility, and anti-blocking performance of the ammonia injection grid. Moreover, a triangular large-scale flue gas self-mixing device is developed to improve the uniformity of the NO_x concentration field at inlet of the SCR reactor and enhance the load adaptability of the SCR denitrification device from the root. The relative standard deviation of NO_x distribution at the SCR outlet of a 600 MW unit under high, medium and low loads reached 8%~19% by using this technology, and the ammonia escape at full load decreased by 51%.

Methane is one of the main components of atmospheric pollutants, which is challenging to be eliminated by catalytic oxidation under mild conditions because of its tetrahedral structure stability. In this work, the acidic sites of Pd-based catalysts are modified by introducing transition metals (Cr, Mo, W) to promote the cleavage of C-H bonds and therefore to enhance the catalytic oxidation performance of methane. The oxygen vacancies, acidity and redox property of prepared catalysts are systematically characterized by XRD, Raman, H₂-TPR and NH₃-TPD techniques. The results show that, the transition metal modification increases the acidic site of Pd catalysts obviously, and the modified PdM catalysts have a higher amount of oxygen vacancies. However, only Mo modified PdMo catalyst exhibits better redox performance, while Cr and W modified PdCr and PdW catalysts show slightly lower redox performance. The results of the methane oxidation reaction confirm that the PdMo catalyst with moderate acidic sites displays excellent performance in the methane oxidation reaction, and its T₉₀ decreases by about 150 ℃, while the PdCr and PdW catalysts with more and less acidic sites show lower methane oxidation activity. The results indicate that the number of acid sites and the redox properties of the catalyst jointly determine the methane oxidation performance. This conclusion provides critical insights for design and preparation of catalysts for complete oxidation of methane at low temperatures.

Under the background of wide application of low nitrogen and oxygen combustion technology and deep peaking technology, the high temperature corrosion failure of water wall tubes is more serious in service process. The high-temperature corrosion behavior characteristics of the boiler water wall tube and high-speed arc spraying PS45 coated tube from a power plant were comparatively investigated. Moreover, the corrosion surface morphology, corrosion products compositions and corrosion cross section characteristics were systematically analyzed by means of SEM, EDS and XRD. The results show that, the high-speed arc spraying PS45 coating can effectively improve the high temperature corrosion resistance of water wall tubes, and the thickness of the surface corrosion layer is small. In the process of high temperature service, the PS45 coating shows better corrosion resistance due to its high content of Cr and Ni, and the thickness of the surface corrosion products layer is thin. However, the microscopic pores between the coating particles will lead to intrusion of high-temperature corrosion reactions, and even cause direct corrosion of the water wall tubes at the coating/substrate interface.

Energy saving and emission reduction in road transport field is an important part of the strategy to achieve carbon neutrality. Heavy commercial vehicles have high power and range requirements, and the transition from conventional internal combustion locomotives to hybrids with waste heat recovery is of great significance in improving engine efficiency and reducing energy consumption. However, the waste heat recovery system integrated with hybrid power in current research mostly adopts a simple layout, and only recovers a single form of waste heat energy from the cylinder liner water or flue gas, which has a limited degree of enhancement to the overall efficiency of the vehicle. Therefore, a waste heat recovery system based on the organic Rankine cycle that can simultaneously recover the waste heat from flue gas and cylinder liner water and operate efficiently under full operating conditions is proposed. The system is coupled with a series hybrid power system and operates under high-speed and suburban road conditions, the performance of the organic Rankine cycle system and the improvement effect of the overall energy efficiency of the integrated system are then investigated. The results show that, under the premise of considering the weight of the waste heat recovery system, the waste heat recovery system improves the engine efficiency by 2.85% and reduces the overall fuel consumption by 6.78% under high-speed USHWY conditions. Under urban road UDDS conditions, it enhances the engine efficiency by 2.30% and decreases the overall fuel consumption by 6.43%. The above results demonstrate the system’s fuel-saving capability and application potential. It is found that the organic Rankine cycle system has a large inertia, and the long-term stable operation of the engine plays a decisive role in improving the output power and efficiency of the system, so the system is suitable for matching with high-speed operation of heavy-duty hybrid vehicles.

Geothermal power generation, as one of the main ways to develop and utilize geothermal resources, is of great significance to promote the low-carbon and clean energy structure and the realization of the “dual carbon”. Firstly, the development history of geothermal resources in the world is analyzed. Then, main geothermal power generation technologies such as dry steam power generation, flash steam power generation, binary cycle power generation and wellhead power generation technology are overviewed. On this basis, the hot dry rock power generation, thermovoltaic power generation, supercritical CO₂ cycle power generation, combined power generation technology and multi-energy eomplementary power generation technologies such as geothermal-solar, geothermal-wind, geothermal-biomass, and geothermal-ocean energy, are elaborated in detail. Finally, combining with the current situation and existing problems of geothermal power generation in China, some suggestions for the development of geothermal power generation are put forward, to provide reference for the future development of geothermal power generation.