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.

Building a new power system focusing on new energy resources puts forward higher requirements for deep peak shaving of coal power unit. Through the requirement analysis of power grid and the comparison of various energy storage technologies, taking the system characteristics analysis of coal power unit as the starting point, a system and a operation mode were given which were based on molten salt thermal storage to assist deep peak shaving of coal power unit. Through theoretical analysis, the calculation methods of the main parameters of subsystems including the heating, heat storage and heat exchange of the molten salt system have been put forward.Taking a 660 MW coal-fired unit as an example, based on the analysis of the thermal boundary and peak shaving demand, the power and connection mode of the electric heating module of the molten salt system are calculated using the calculation method proposed in this article. The types of molten salt and the inlet and outlet parameters of the heat exchange system are selected. The capacity, salt consumption and tank volume of molten salt heat storage are determined. All the results provide reliable data support for accurate accounting of project investment and land occupation. This system and calculation method can provide reference for the preliminary design of similar projects.

The analysis of heat and mass transfer process has important guiding significance for the performance improvement of heat and mass transfer equipment. Through the analysis of the thermal resistance in the boundary layer, the author explores the development of the convective thermal resistance and thermal conduction thermal resistance in the laminar flow of the pipeline in the boundary layer, and establishes a mechanism model (R-P model) that conforms to the macroscopic characterization. The thermal resistance distribution law under the condition of Re and Pr, explored the internal mechanism of laminar flow enhanced heat transfer in the tube, and guided the optimal design of the flow-around structure. The results show that the heat conduction is absolutely dominant in the inlet stage, and the proportion of convection gradually increases after the full development. The mechanism of Re and Pr affecting heat transfer is different. When Re increases, the heat transfer must be strengthened. When Pr increases, it only increases the proportion of convection, and in the range of (Pr<1.8), thermal resistance always plays a major role. At the same time, it was found that adding a turbulent flow structure to the laminar flow in the pipeline would reduce the heat transfer effect.

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.

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.

Large proportion burning high-alkali coal will cause serious contamination to the heating surface of the boiler, and threat the device security and stable production of the power plant. The article compared flue gas temperature changes of three types of boilers burning Xinjiang Naomaohu high-alkali coal, XRD phase analysis and chemical composition analysis of ash slag was also performed. Analysis results indicate the composition of the ash block developed by short-term bonding is close to that of coal ash, and the texture is loose, and the heating surfaces can be kept clean by soot blowing optimization. The shell-like slag formed by long-term contamination is rich in SO₃ and Na₂O, the degree of sintering is high, and the texture is hard, controlling the flue gas temperature of the heating surface inlet can effectively reduce the fouling and slagging of the tube panel. The flue gas temperature at the convection heating surface inlet with tube panel gaps of about 50 mm should be controlled below 800 ℃, when the gaps are above 200 mm, the flue gas temperature should be controlled below 1 000 ℃. The results of the research can be used as a reference for the same type of boiler burning high-alkali coal.

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.

Zhundong has large coal reserves and low mining costs, making it the most economical fuel in the Xinjiang Zhundong region. However, Zhundong coal has strong slagging and fouling properties, which seriously restricts the safe and stable operation of boilers. Boilers in the Zhundong region usually require burning at least 20% low alkali coal, the low reserves and high prices of low alkali coal seriously constrain the cost reduction of power plants. In order to promote cost reduction, an experimental study on burning high ratio of Zhundong high alkali coal was conducted on the 350 MW unit boiler of Wucaiwan Power Plant. A collaborative optimization strategy was adopted to prevent and control slag and contamination on the heating surface of the boiler. This included adding kaolin to coal to regulate the composition of coal ash, and deeply optimizing the operating parameters of the pulverization system, combustion system, and soot blowing system. The test results show that the collaborative optimization strategy has solved the long-standing problems of large-scale slag flow on the water-cooled wall, clogging of the burner nozzle, and severe fouling of the convective heating surface of this type of boiler. The safety and load capacity of the boiler operation have been greatly improved, and the coal structure can be lastingly maintained as 92.5% Zhundong high alkali coal and 7.5% kaolin, with significant safety and economic benefits.

In order to solve the problems of high pollutant emission mass concentration, low energy utilization rate and high initial investment cost of conventional waste disposal power station, combined with the green transformation development needs of coal-fired power station. This paper proposes the technical ideas of coal-fired boiler station coupled with waste. A 30 t/d coal-fired boiler station coupled waste was built to analyze and study the impact of system operation on the efficiency of coal-fired power station, pollutant emissions and energy efficiency of waste disposal. And this paper uses three coupling methods of hot air, flue gas and steam water to achieve efficient and clean disposal waste on large coal-fired power station. The results show the three coupling methods are completely feasible to achieve efficient and clean disposal waste. The coupling of hot air can improve the effect of disposal waste and reduce the carbon content of fly ash and slag; the coupling of flue gas can ensure conventional pollutants such as SO₂, NO_x and dust reach the emission level of coal-fired power station without increasing the emission of dioxins. The coupling of steam water can improve the energy efficiency of disposal waste. This technology provides new technical ideas for the disposal of organic solid waste and has a broad application prospect.

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.