In order to solve the safety and economic issues of mixed combustion of multiple fuels such as gas, lignite, and coal slurry in power plant boilers, an evaluation method for the blending of multiple fuels was proposed. Firstly the constraints on the moisture, volatile matter, calorific value, and sulfur content of the fuel entering the furnace under different loads are established, based on the fuel characteristics and various requirements for safe operation of the unit, and then the minimum comprehensive power supply cost and the optimal blending scheme for multiple fuels under different loads are determined through blending experiments. The experiments were conducted on a 300 MW power plant boiler, and the results showed that, on the premise of meeting the constraints of the incoming fuel, the fuel cost for power plants can be decreased by increasing the proportion of economic coal blending based on the principle of minimizing comprehensive power supply costs. This study will provide important reference for the study of multi fuel blending in power plant boilers.

In order to explore the way of high efficiency and low nitrogen combustion in oxy-fuel combustion, the experimental study on oxy-fuel staged combustion characteristics of Shenfu bituminous coal and Yunnan inferior bituminous coal was carried out on the down-draft furnace of Dongfang Boiler Test Center, and the burnout characteristics and nitrogen oxide emission characteristics of two kinds of coal under oxy-fuel staged combustion conditions were explored. The experimental results show that under the condition of oxy-fuel combustion, the combustion efficiency of Shenfu bituminous coal can reach more than 99%, and the NO_x emission concentration in flue gas can be controlled within 19.10 mg/MJ by using over-fire air staged combustion and reasonable control of oxygen staged feeding. The combustion efficiency of Yunnan inferior bituminous coal is slightly lower due to the delay of ignition and the long enough residence time required for burnout. However, the combustion efficiency can reach more than 90 % with reasonable oxygen classification, and the NO_x emission concentration in flue gas can be controlled within 16.83 mg/MJ. The effect of furnace temperature of oxy-fuel combustion on the cumulative formation and release curve of NO_x is consistent with that of air combustion. The higher the furnace temperature, the faster the heating rate of pulverized coal particles. The higher combustion efficiency and lower NO_x emission concentration can be found by adopting oxy-fuel staged combustion and reasonably controlling the timing and position of oxygen staged injection, so as to achieve high efficiency and low NO_x emission of oxy-fuel combustion.

The overheating of boiler heating surface seriously affects the safe operation of the power plant. It is of great significance for the safety of boiler to predict the tube temperature of heating surface and to take appropriate preventative measures. A data driven-based model for tube temperature prediction is proposed in this study. Firstly, the key variables affecting the tube temperature are selected by grey correlation analysis that affect the wall temperature of the heating surface, and a wall temperature prediction model based on long short term memory (LSTM) neural network is constructed. Then, the correlation feature coefficients under similar historical operating conditions are defined, and the predicted wall temperature obtained by the LSTM neural network is corrected to improve the model's prediction accuracy. Finally, an on-duty supercritical boiler with 600 MW capacity is taken as the case study. Results showed that the relative error of the proposed prediction model is within (−2.5%, 2.5%). The average relative error is 0.40%, and the average tube temperature prediction error is 2.24 ℃. It indicates that the proposed model is helpful for the tube temperature prediction of the boiler under complex operating conditions.

The combustion of biomass will not increase carbon dioxide emissions, and the development of biomass coal coupled power generation technology is a feasible way to accelerate the transformation and upgrading of electricity. The compressed biomass and coal powder are ground in different coal mills without mixing, and are fed into the furnace by different burners. This method does not require additional biomass treatment equipment or setting up a biomass fuel treatment workshop, which can greatly save investment and factory space. The key limiting technical factor is whether the pulverizer of the power plant can effectively grind biomass Pellet fuel, and how to evaluate the adaptability of the existing pulverizer to the new coupling fuel. To this end, a medium speed coal mill experimental platform was built to analyze the adaptability of the medium speed coal mill in grinding biomass particles. The results show that the grinding output of the medium speed coal mill decreases when grinding wood chip biomass particles, and the effective output correction coefficient is 0.65~0.70; When the ZGM medium speed coal mill grinds sawdust particles, the loading force characteristics and separator characteristics both vary significantly at the particle size boundary of 0.2 mm. Therefore, the screening fineness R₂₀₀ and R₅₀₀ can be considered as the measurement standards for the uniformity of biomass particle materials ground by the coal mill; Compared with pulverized coal, the increase of loading force of milled biomass particles or the increase of rotating speed of the current separator has a large difference in the influence of fineness distribution, which needs further in-depth research.

The power industry is the core of the energy system as well as a major carbon emitter. The zero-carbon development of it is the key to the process of carbon neutralization in China. From the perspective of carbon emission, energy resource endowment, industry status, existing problems and development trend, the general situation, low-carbon development path and effect of the electric power industry in the United States, Germany, France and Britain in the European Union was analyzed. Several enlightenments combined with the current situation of the electric power industry in China were summarized, hoping to provide reference for the low carbon development of Chinese electric power industry.

Conventional industrial steam turbines are usually equipped with quick-closing inlet valves to realize emergency shutdown of the turbine. In this paper, a negative pressure inlet condensing steam turbine was studied has low inlet parameters, large inlet steam volume flow and small pressure difference between inlet and exhaust steam ends. In order to reduce the intake pressure loss, the quick-closing inlet valves are not employed, but a redundant large-diameter rapid vacuum breaker valve is used at the exhaust end of the turbine. When the turbine needs emergency shutdown, open the quick vacuum breaker valve, so that the atmosphere quickly enters the exhaust end of the turbine, the pressure of the exhaust end of the turbine rapidly rises, In this paper, the steam turbine whose inlet and exhaust steam pressure difference is 40 kPa is studied, and the pressure difference between the inlet end and the exhaust end of the turbine could reach 0 within 4 seconds, so that the turbine is closed, and the purpose of emergency shutdown of the turbine is achieved.

Condensate downcomer vibration is a common phenomenon in the direct air cooling system, which endangers the safe operation of the air cooling system when the vibration is serious. The pipe vibration model is established based on the fluid solid coupling method. The two-phase flow characteristics of the condensate pipe are analyzed using the theory of flow induced vibration and fluid cavitation. The model analytical calculation and numerical simulation are carried out for the condensate pipe of a 660 MW ultra supercritical unit. The results show that saturated or nearly saturated condensate flows from the air cooling platform along the condensate downcomer to the hot well of the steam exhaust device by gravity flow. When the potential energy of water is released, two-phase flow excitation and cavitation phenomena occur. Based on this analysis, the causes of condensate vibration and cavitation noise are found, By using multi-stage Venturi tubes and porous orifice plates in the condensation water pipeline of the power plant to eliminate the condensate potential energy, avoid excessive pipeline vibration and noise, and eliminate the hidden danger of pipeline vibration.

The failure of boiler tubes in thermal power units will cause non shutdown of units and greater economic losses. Deposits in boiler tubes are an important reason for their failure, and reducing deposits in boiler tubes is of great significance to the safe and stable operation of units. It is found that the formation of deposits is related to many factors, such as overheating of furnace tubes, high heat load, poor water vapor quality, water vapor phase transition, working medium disturbance and pipe surface defects. Combined with the flexibility of units, deep peak shaving operation, environmental protection reform and other conditions, the formation mechanism and influencing factors of various types of deposits are analyzed with actual accident case pictures. The effects of overheating, salt concentration and corrosion under scale caused by deposits in furnace tubes are further discussed. The countermeasures for feedwater quality, boiler shutdown protection, unit startup steam purification, unit peak shaving, boiler tube replacement, boiler transformation and maintenance are proposed, which can effectively reduce the generation of boiler heating surface deposits and reduce the risk of boiler tube failure.

To effectively alleviate the high-temperature corrosion of the water-cooled walls on both sides of the opposed wall combustion of a 660 MW unit's boiler and the erosion caused by coal particle impingement, a solution was proposed to deflect the swirl burners near the side walls by 3.5° towards the center of the furnace. This solution was based on an understanding of the causes and mechanisms of high-temperature corrosion and considering the on-site equipment conditions. Numerical simulations were conducted to analyze the combustion in the boiler before and after the burner deflection. A comparative analysis was performed on the changes in temperature distribution, velocity field, concentration field, and particle trajectories resulting from the burner angle deflection. The proposed solution was also implemented in practical engineering. The results of the numerical simulations and engineering application demonstrated that after deflecting the burner angles, the airflow inside the furnace concentrated towards the center, resulting in a reduction of coal particle impingement near the side walls and mitigating erosion. Additionally, the temperature near the side walls decreased, leading to a decrease in reducing atmosphere and a reduced risk of high-temperature corrosion. The combustion efficiency of the boiler remained unaffected. The findings of this study can serve as a reference for preventing and managing high-temperature corrosion and water-cooled wall erosion in boilers of similar types.

Under the background of carbon peak and carbon neutralization, the importance of thermal power generation in northwest China has been further increased. Due to the high proportion of high alkali coal in this area, serious slagging and contamination come out easily in the process of burning high alkali coal in boiler. It's of vital importance to solve the problem of safe burning of high alkali coal ensuring the safety of electric power in China. The present situation of high-alkali coal combustion technology at home and abroad is introduced in this paper. With more than ten years' research, the high-alkali coal combustion technology in China has been improved remarkably, and the related achievements have been popularized and applied in the electric power industry. The blending ratio of high alkali coal in boiler has been increased from less than 60% to more than 90%, though the full burning of high alkali coal has not been realized yet. This paper introduces different technical routes to realize full burning of high alkali coal and analyzes the equipment parameters and operation of typical boilers burning high alkali coal. Generally speaking, pulverized coal boiler, fluidized bed boiler and liquid slag boiler have their own advantages and disadvantages in the adaptability to high alkali coal, with technical bottlenecks to be further studied and broken through. In order to ultimately solve the high alkali coal combustion problem, more new technologies need to be introduced.