An efficient integrated power generation system of solid waste coupled with anaerobic fermentation and incineration is proposed. Solid waste anaerobic fermentation is adopted to generate biogas, which enters the biogas burner to burn and generates high-temperature flue gas, and the flue gas heats the steam-water system and the primary and secondary air through the heater and air preheater in the unit. Under the condition that the heat generated by solid waste incineration in the boiler is not changed, the energy entering the steam turbine to do work is increased, thus the power generation efficiency of the whole unit increases. At the same time, according to the first law of thermodynamics and the second law of thermodynamics, the reasons for power generation efficiency and exergy efficiency improvement are analyzed. The results show that, compared with the case unit, the proposed high-temperature flue gas system with biogas combustion can increase the net power generation by 8.69 MW. In addition, the power generation efficiency and power generation exergy efficiency of the new system has increased by 3.56 percentage points and 9.74 percentage points, respectively. Economic analysis shows that the proposed coupling system is equipped with an anaerobic fermentation biogas combustion system, and the dynamic recovery period is 3.78 years, which has obvious economic advantages.

In order to select high activity catalysts for urea hydrolysis, the kinetic and thermodynamic characteristics of urea catalytic hydrolysis reaction were studied by using batch reactor and continuous operation pilot plant, and the effects of different catalysts on hydrolysis reaction temperature, energy consumption and variable load response time were compared. The results show that, the activation energy of the hydrolysis reaction can be reduced by adding catalyst (the activation energy of the liquid diammonium hydrogen phosphate is 65.3 kJ/mol, and that of the solid alumina is 52.9 kJ/mol), and the urea conversion can be improved. The addition of catalyst increases the hydrolysis reaction rate and decreases the hydrolysis reaction temperature. Due to uneven distribution and insufficient contact, the catalytic activity of solid alumina catalyst decreases in the continuous operation reactor. The energy consumption of ammonia production by catalytic hydrolysis is about 1%~3% lower than that of ordinary hydrolysis, and the response time of hydrolyzer changing load is not shortened by adding diammonium phosphate and alumina catalyst.

Blade fractures and cracks occurred on low pressure second last stage moving blade of a steam turbine before and after the blade optimization. In order to find out the cause of this type blade failures and prevent subsequent reoccurrence, the blade failure, operating parameters and historical records were checked, and the materials and fractures of some failed blades were analyzed through physical and chemical inspection. Moreover, the centrifugal stress of the blade and the vibration characteristics of the gear train before and after optimization were numerically analyzed by finite element method. The results show that, the blade fracture is a high peripheral fatigue fracture. Before optimization, the main reason for cracks and fractures at the connection transition between the top of the inner cambered surface and the shroud on the steam outlet side of the blade is that the blade has a large torsional recovery under working conditions, resulting in severe compression of the shroud, and stress concentration and fatigue damage occur at the connection transition between the top of the inner cambered surface and the shroud on the steam outlet side. The unreasonable design of blade root structure is the main factor for high cycle fatigue cracking of blade root, while the vibration of the sixth pitch diameter of the first stage of blade impeller system falling into the "3-coincide point" resonance area is the secondary factor for blade failure. After optimization, the main reason for the fracture is the unreasonable design of the blade root structure, and the vibration of the eleventh pitch diameter of the second stage of the blade impeller system falling into the "3-point" resonance area is the secondary factor causing the blade root failure.

By taking a supercritical 600 MW opposed firing boiler as the research object, the temperature deviation law of main steam on both sides is analyzed and verified through hydrodynamic modeling, and a technical scheme is put forward to optimize the temperature deviation of main steam from the perspective of water side. After adopting this steam temperature optimization scheme, the main steam temperature deviations on both sides of the boiler reduced by 44.6%, 95.8% and 28.0% respectively under 50%, 75% and 100% BRL conditions. This scheme can realize safe and economical operation of the unit, and has good guidance and reference value for the same type of boiler.

In order to realize zero liquid discharge, a power plant treated circulating wastewater by the combination process of two stage softening and clarification, media filtration, ultrafiltration, nanofiltration (NF) and reverse osmosis (RO), and treated terminal wastewater by the combination process of chemical softening, tubular microfiltration (MF), NF, seawater desalination reverse osmosis, electrodialysis (ED) and evaporative crystallization. After the above measures were taken for 1 year, insufficient NF output was found in the circulating wastewater treatment system, and serious MF membrane organic fouling and ED silicon scaling was observed in the terminal wastewater treatment system. Thus, the causes of the membrane fouling was analyzed and the desulfurization process water was optimized to reduce the chemical oxygen demand (COD) of desulfurization wastewater from the source. Moreover, the MF operation mode was optimized, so as to slow down the MF organic pollution phenomenon. In addition, the RO concentrated water of circulating water treatment mode was adjusted, and the total silicon mass concentration was reduced to less than 1 mg/L before being fed into the ED equipment, to solve the problem of the ED silicon scaling.

To solve the problem of low recognition accuracy of transformer insulation oil gas fault diagnosis, the slime mold algorithm (SMA) is improved by the reverse learning strategy to form the improved slime mold algorithm (ISMA), thus to improve the global optimization ability and optimize the support vector machine (SVM). An ISMA-SVM optimized fault diagnosis model is established, and the sample set is used for learning and training. The diagnosis and recoginition results are compared with that of the greywolf algorithm (GWO-SVM) and the particle swarm optimization (PSO-SVM), it shows that the accuracy of the ISMA-SVM fault diagnosis and recognition is 93.3%, which is 6.66 and 10.66 percentage points higher than that of the GWO-SVM and PSO-SVM, respectively.

The variable operating condition of thermal power units makes the data show multi-modal characteristics, which leads to the decrease of prediction accuracy of the regression soft sensor model based on shallow network structure. An improved BP neural network (back propagation neural network, BPNN) soft sensor method is studied. Firstly, the original data features are extracted by using the strong deep learning ability of stacked sparse autoencoder (SSAE), and then the extracted features are analyzed by BPNN. The experimental results show that, the mean square error of the SSAE+BPNN soft sensor method is 0.135 8×10^–3 and the square correlation coefficient is 0.983 2. It is proved that its prediction accuracy and generalization ability are significantly better than those of BPNN. It is applied to the soft sensor of carbon content in fly ash of a flexible peak-shaving 660 MW ultra-supercritical generator set, and the average relative error of the prediction results is 0.91%, the overall relative error is less than±5%, indicating the method has good engineering application value.

In order to study the corrosion behaviors of candidate materials for superheater of supercritical boilers in high-temperature flue gas environment, three austenitic heat-resistant steels including S31042, S31035 and C-HRA-5 were exposed to laboratorial simulated coal-fired flue gas for hot corrosion tests. The tests were carried out at 650, 675, 700 and 725 ℃. On the sample surface, there were three conditions including no coating, coating with real coal ash, and coating with corrosive simulated coal ash. The test duration was 500 h. The corrosion kinetic curves of the three materials were obtained through experimental research, and corrosion behaviors of the material were analyzed by XRD, SEM and EDS. Moreover, corrosion resistance of the three materials was compared. The results indicated that, the three materials had excellent resistance to oxidation and corrosion under the conditions of no coating and coating with real coal ash. Under the condition of coating with corrosive simulated coal ash, the material corrosion intensifies and the corrosion products are layered. The temperature effect was different under different coating conditions. S31042 had the best corrosion resistance, and the corrosion resistance of S31035 and C-HRA-5 materials was comparable.

Welding of dissimilar steels is a widely used connection method for super-heater tubes of boilers in power plants. Taking the TP304H/T22 dissimilar steel welded joint with backing plate at the superheater outlet of a thermal power unit as the research object, the formation mechanism and influence of cracks in the welded joint are analyzed through macro measurement, microstructure analysis, EDS energy spectrum detection and tensile test. The results show that, the differences in thermal expansion coefficients of the three substrates and stress concentration are the cause of the cracks of the dissimilar steel weld with backing plate and crack propagation in nickel base weld filler. The weld is the weak link in room temperature tension, while the fusion line and base metal are the fracture parts in high temperature tension.

The high-temperature and high-pressure (300 ℃/10 MPa) corrosion electrochemical behavior and oxide film microscopic features of Incoloy 800H alloy aged at 675 ℃ for 0~10 000 h in alkaline environament were investigated systematically. By means of electrochemical test, long-term immersion test, scanning electron microscope/transmission electron microscope observation, Raman spectroscopy/fast Fourier transform analysis and other methods, the electrochemical activity, evolution of oxide film morphology and composition characteristics of the 800H alloy with extension of aging time were systematically studied. The results show that, the value of open circuit potential and self-corrosion potential E_corr of the 800H alloy in high-temperature and high-pressure water can be slightly increased by aging treatment, but the effect of aging time extension on the electrochemical behavior was not significant. A passive to trans-passive process was depicted. The oxide film of the 800H alloy formed in high-temperature and high-pressure water had a multilayer structure: the most outer layer was the dispersed large particle oxides composed of Fe₂O₃ or NiFe₂O₄; the middle layer was relatively compact small size oxides, mostly NiFe₂O₄ or FeCr₂O₄; while the inner layer was dense and continuous oxides, amorphous or nanocrystalline oxide containing Cr and a small amount of Fe. The 800H alloy has good corrosion resistance and surface stability in alkaline high temperature and high pressure water of 300 ℃/10 MPa.