With the structural upgrading of China's energy industry and the transformation of economic growth mode, clean energy power generation technology has been continuously and rapidly developed. As a high-power electric heating conversion device, electric boiler has become one of the effective technical solutions to enhance the operational flexibility of thermal power units and promote the reliable consumption of new energy power. In this paper, the allocation and accounting principles of electric boiler capacity and heat storage capacity in such projects are proposed. The calculation model of system optimization operation parameters and operation economy evaluation is established based on the principle of maximizing the economic benefits of enterprises, taking into account the factors of grid peak shaving depth dispatching limits. Combined with the actual situation of the multi-unit system of a thermal power plant in Northeast China, the optimal configuration capacity of the electric boiler of the project is 300 MW, and the heat storage capacity is 17 MW·h. At the same time, the optimal operation scheme of the whole plant is proposed. The results show that, under the condition of 30% peak shaving depth limit, the case power plant can add about 139.53 million Yuan in each heating season, and the project investment payback period is about 5 years. In the foreseeable future, the project will have long-term profitability.

With the continuous progress of the work of "carbon neutrality and carbon peak", the installed scale of photovoltaic, wind power and other new energy is expanding, energy saving and consumption reduction as well as flexibility improvement become the two key tasks the thermal power units faced. Through mathematical modeling and hourly calculation analysis for the hybrid system, performance and economic characters for solar-thermal systems replacing high pressure heaters are obtained. The calculation results indicate that, using solar thermal and coal fired hybrid system can realize sharp decline of the unit coal consumption, which is a most direct and effective method for coal saving and reducing consumption, it has great significance for life prolonging of the units to be retired from active service because of high coal consumption indexes. However, the economic benefit of the system itself is insufficient. So it can be supplemented with molten salt electric heater to improve the system's frequency modulation ability and enhance the project's profitability. According to the calculation, when the frequency modulation income is not considered, the system's yield is only 6.0%, but it can be increased to 8.0% after considering the frequency modulation income. Therefore, the hybrid system has double effects in improvement of both coal saving transformation and flexibility transformation.

In order to improve the flexibility of thermal power units, enhance the peak shaving capability of thermal power units coupled with molten salt heat storage system, and reduce project investment, a variety of electric heating molten salt energy storage systems coupled with thermal power plant were proposed. The thermal performance, peak shaving capacity and molten salt consumption of a 350 MW unit were analyzed with EBSILON software. An optimal system for deep peak shaving was proposed. The results show that, during the heat charging process, the electric heating system demonstrates a higher cycling efficiency as 33.2%, which enables the lowest power generation load to be reduced to below 25%. The flow rate of molten salt in this system is only 6.6%~31.2% to that of a steam heating system. During the heat discharging process, the water is drawn from the inlets of No.1 and No.2 high pressure heater. The water temperature is 182.4~242.7 ℃. The molten salt-condensed water heat exchanger is self-anti-condensation. The cycling efficiency during the heat discharging process is 32.7%~33.9% at different unit loads, indicating unit load has little effect on the cycling efficiency of the peaking shaving system. The research results can guide the engineering application of the deep peak shaving technology of thermal power units coupled with molten salt heat storage.

Flexible transformation of thermal power units is the key to build a new power system and achieve the goal of "carbon peak" and "carbon neutrality". In order to promote the flexibility of thermal power units, the coupling scheme for small steam turbine drive and motor drive liquid compressed carbon dioxide energy storage system and thermal power unit is put forward, and the thermodynamic system model is established. Moreover, the heat consumption rate and energy utilization coefficient are used to evaluate the system, the thermodynamic performance of the system is compared and analyzed, and the optimal coupling scheme of energy storage is established. The researches show that, in the energy storage stage, condensate water is extracted from the outlet of the condensate pump, and the compressed heat is absorbed and returned to the outlet of No.7 low-pressure heater. In the energy release stage, steam is extracted from the exhaust of the middle pressure cylinder, and the expanded CO₂ is heated and returned to the No.5 low-added hydrophobic cooler, the coupling system has the best performance. The heat consumption rate is 48.308 kJ/(kW·h) lower than that of the original system, and the energy utilization coefficient increases by 0.52 percentage point. Changing the inlet temperature and the mass flow rate of CO₂ expander can quickly change the load. After coupling with the energy storage system, the peak regulation capacity of thermal power unit increases by 17.1%, when the hot water tank is configured and the maximum heat is released, the peak regulation capacity of the unit increases by 37.4%, indicating the flexibility of thermal power unit is improved.

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.

With the completion of ultra-low emission transformation of thermal power plants, problems such as increased costs and excessive ammonia injection have arisen. Modeling and optimization of power plant operation data through machine learning has become an important means to solve the above problems. This article reviews the commonly used machine learning algorithms and their application scenarios in reducing nitrogen oxides. In terms of algorithm, the main algorithms of data preprocessing, modeling prediction and parameter optimization and their applicability to nitrogen oxides removal are summarized. The research directions of multi-operating condition data preprocessing method and the construction method of the objective function in multi-objective optimization are proposed. For the application level of the machine learning methods, such as low nitrogen combustion in the furnace, optimization of SCR denitration system, and comprehensive energy saving and consumption reduction of the whole system, the implementation methods and corresponding effects are summarized. The future research directions of long-period dynamic modeling control and multi-power plant joint modeling have prospected.

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.

Tibet is located in the hinterland of the Qinghai-Tibet Plateau, the area above 4 000 m accounts for 85% of the total area of the region, its geothermal resources are very rich. To realize the reasonable exploitation of geothermal resources, combined with the carbon peaking and carbon neutrality strategy, the current situation of the development and utilization of geothermal resources in Tibet is comprehensively combed, and the suggestions for the future development of the geothermal industry are put forward. The analysis shows that the geothermal resources of hydrothermal and dry hot rock in Tibet have large storage capacity, good quality, and excellent power generation potential. The shallow geothermal resources are mainly distributed in Lhasa, which can be combined with heat pump technology for local heating. At present, there are still some problems in geological exploration, technical improvement, equipment development, and operation management. It is necessary to develop ORC units, build EGS experimental platform, and scientifically develop deep geothermal energy. The research shows that the development and utilization of geothermal resources in Tibet should follow the principles of "survey-based, power generation-based, heating-assisted, equipment upgrading, and cascade utilization", promote the scientific exploitation and efficient utilization of geothermal resources, improve the geothermal industry chain, and effectively improve the energy consumption structure in Tibet.

In order to improve the energy utilization efficiency of high flexibility power generation system coupled with internal combustion engine and coal-fired unit, a new thermal system combined with the internal combustion engine and the coal-fired unit was proposed. By feeding the flue gas of internal combustion engine and the waste heat of cooling water into the thermal system of coal-fired generating unit, the coal consumption of coal-fired generating unit can be reduced. EBSILON software was used to model the composite system. Steam consumption rate and heat consumption rate of the coal-fired units were taken as evaluation indexes to analyze the thermal economy of the coal-fired unit under different composite schemes. The results show that, the heat consumption rate and steam consumption rate of the coal-fired unit can be significantly reduced by combining the waste heat of the internal combustion engine into the thermal system of the coal-fired unit. The closer the compound position of flue gas waste heat is to the boiler, the smaller the proportion of feed water and condensed water involved in flue gas heat exchange, and the lower the heat consumption rate and steam consumption rate of the unit. When one part of the flue gas waste heat is used to heat the high pressure heater feed water and the other part is used to heat the low pressure heater condensed water, more waste heat will be allocated to feed water, and the heat consumption rate and steam consumption rate of the unit wil decrease. After optimization, the heat consumption rate of the combustion engine and coal-fired unit combined thermal system can be reduced by 6.62% at most.

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.