The cooling efficiency of flat film was measured using a high-precision infrared thermal imager, and the film cooling efficiency between double-cross-row holes and single row holes is compared. The interaction between film holes and the influence of blowing ratio (M=0.65, 1.0, 1.5) and density ratio (DR=1.0, 1.5) on the cooling efficiency was analyzed. Moreover, the flow field with film cooling was compared using numerical calculation methods. The results show that, with the increase of the blowing ratio, the cooling efficiency of the single row holes decreases while that of the double-cross-row holes improved greatly, but the film coverage effect at the spanwise direction deteriorates. Increasing the density ratio will improve the cooling performance. However, the influence of double rows of film holes and blow ratio is much higher on the cooling effectiveness, compared with the density ratio. For the double rows of film holes cooling, the cooling jet forms a reverse kidney-shaped vortex downstream of the holes, which will prevent the jet blowing away from the cooling wall.

Thermal power units are faced with a variety of ways to sell electric heating products, such as electricity contract market, spot market electricity sales, auxiliary service market electricity sales, civil heating and industrial heating. It is necessary to optimize the distribution of limited thermal power unit electric heating products in various markets according to the market trading mechanism, operating costs and carbon emission cost to obtain maximum profits. The intelligent decision-making system can help thermal power units to provide the optimal group and bidding strategy at all levels of the market, business accounting and the optimal operation mode of units.

China has abundant high-alkali coal resources. This article provides a comprehensive review and summary of the research and engineering application progress of high-alkali coal combustion technology from the aspects of basic research, key technologies, and engineering practice. In particular, the latest status of the mechanism research and practice of fully burning Xinjiang high-alkali coal in a wet-bottom boiler is introduced. The review aims at providing a reference to develop more economic combustion technology that can safely co-fire a high proportion or even solely burn Xinjiang high-alkali coals in a long operational period.

Although the reserves of high-alkali coal represented by Zhundong coal is huge, the problem of coking on heating surface of the boiler is prominent during co-firing high-alkali coals in thermal power units, which not only reduces the boiler thermal efficiency, but also seriously threatens the safe, stable and economic operation of the unit. In order to solve this problem and promote the utilization of high-alkali coal, this paper reviews the researches on coking of the heating surface of high-alkali coal boilers and the prevention. Up to now, extensive researches have been carried out at home and abroad on the characteristics of coking on the heating surface of coal-fired boilers, coking mechanism, influencing factors, prevention and control measures, and so on, and fruitful research results have been achieved. On the basis of controlling the quality of coal, improving boiler structure, and optimizing boiler operation, the preparation of coating on the heating surface of boilers has also become an important technical path for preventing and controlling coking. In the future, the coating should possess excellent comprehensive properties such as high temperature resistance, corrosion resistance, wear resistance, thermal conductivity, thermal fatigue and so on, while having outstanding coking resistance. Meanwhile, the coating also should have desirable preparation economy and preparation efficiency, especially the on-site applicability.

In order to compare the particle formation characteristics of typical high-alkali and high-chlorine Xinjiang coal under combustion conditions, a three-stage high temperature drop tube furnace was used to carry out the combustion experiment of Zhundong coal (ZD) and Shaerhu coal (SEH) in air atmosphere. The characteristics of particulate matter after combustion were analyzed. Particulate matters were collected by Dekati low pressure impactor+ (DLPI+) and the mass-based particle size distribution, elemental compositions and morphology were discussed. The results showed that the particulate matter produced by the combustion of the two coal samples presents a double-peaked model. The fine particle yield of SEH is significantly higher than that of ZD. The main components of sub-micron particles were Na and Cl. The Cl in PM₁₀ accounts for 11.8% and 28.9% of the Cl content in ZD and SEH raw coal, and Na accounts for 2.66% and 7.53% of the Na content in ZD and SEH coal ash. High levels of alkali metals and Cl promoted the formation of fine particles. A large amount of Cl in SEH raw coal migrated into particles and contributed greatly to the formation of sub-micron particles.

FMEA is an effective reliability analysis method for identifying potential failure modes in a system and evaluating their criticality. Conventional FMEA has many shortcomings such as not considering the weights of different risk factors, RPN being very sensitive to changes in risk factors, difficulty in handling expert subjective scoring information, and not considering the propagation and impact relationships between failure modes. Aiming at these shortcomings, an improved FMEA method was proposed by introducing house of reliability, rough set theory and VIKOR method to improve the accuracy and objectivity of risk priority analysis of failure modes. Compared with the conventional FMEA, the improved FMEA can not only effectively deal with the various subjectivities and uncertainties in the risk assessment process but also rank the risk of the identified failure modes with taking into account the effects of failure propagation, which is able to rank the risk priority of failure modes in the case of attribute conflict and various uncertainties. Based on the proposed FMEA, a real-word application of risk priority ranking of the failure modes in wind turbine was carried out and the risk priority order of each failure mode and each subsystem were obtained. According to the ranking results, the weak links and key subsystems of the reliability of wind turbine were identified, and the hazard weight of each failure mode and subsystem was given, which can provide data support for the reliability optimization design of wind turbine.

Xinjiang high-alkali coal is a cost-effective power coal，but when it is used in large proportions, boiler equipment is prone to severe slagging problems. The design principles of the combustion system for boilers using Zhundong coal are inconsistent with conventional technical measures to improve low-load stable combustion performance. To solve this problem, based on the mechanism of stable combustion of pulverized coal, measures such as optimized layout of tiny oil ignition burners, interlaced arrangement of middle layer burners, online adjustable coal powder concentration and burner design optimization have been studied. The technology was applied in a 350 MW unit's deep peak regulation retrofit project using Zhundong high-alkali coal as fuel, and achieved a stable combustion load of less than 18% rated condition without oil injection.

To improve the flexibility of coal-fired units, boilers need to have good controllability and the ability to adapt to rapid load changes. The flexibility of the boiler is closely related to the performance of the control system, which is designed according to the dynamic characteristics of boilers. To study the dynamic characteristics of boilers, a dynamic model of a supercritical 660 MW coal-fired boiler is built in the Dymola platform. The results show that the response time of steam temperature is longer than that of steam flow. When the feedwater temperature, feedwater flow, and fuel quantity are stepped increase by 5%, the main steam temperature changes by 10.2 ℃, –28.5 ℃, and 35.7 ℃, respectively. In the process of adjusting the water-fuel ratio of the boiler, different times of change in feedwater and fuel flow can have different effects on the main steam temperature. The maximum deviation of the main steam temperature during the transient process reduces by 27.4 ℃ when the feedwater flow is delayed by approximately 100 s compared with the fuel flow. When the load change amplitude is the same, the larger the load change rate, the more severe the fluctuation of the main steam parameters, and the longer it takes to stabilize.

In order to reduce fuel procurement costs and ensure fuel supply, a certain power plant in Gansu burns a large proportion of Xinjiang high-alkali Guanghui coal and Xinjiang Energy coal. After burning the high-alkali coal, the boiler experiences severe high-temperature corrosion and coking on the heating surface, and the maximum load can only be carried to 85% ECR. In order to reduce high-temperature corrosion, research has been conducted on coal quality characteristics, combustion optimization adjustment, and equipment improvement technology for boilers. The research results show that, the boiler still experiences severe high-temperature corrosion even when burning low sulfur coal, which is mainly related to the high content of alkali metals such as sodium and calcium, as well as chlorine in Xinjiang coal. By increasing oxygen content, reducing primary air volume, weakening the swirling strength of outer secondary air of the burner, and increasing wall-attached air, operation adjustment measures can improve the high-temperature corrosion characteristics of the water wall to some extent. But to completely solve this problem, it is necessary to start with the use of additives, high-temperature corrosion prevention spraying, adding soot blowers, improving wall-attached air and burner design, and other corresponding technologies. The results of this study can provide useful reference and guidance for power plants that encounter similar problems during the process of high-alkali coal burning.

Further research on slag-tap boiler can promote the application of fully burning high-alkali coal technology. In this study, a supercritical 350 MW once-through double-U flame slag-tap boiler is taken as the research object and the combustion chamber, slag collection tube bundle and cooling chamber are taken as the calculation units, the thermal calculation is performed from the perspective of heat balance. The flow field, temperature field and component field in the boiler under design condition and at variable loads are studied. The deviations of several flue gas temperature results obtained by thermal calculation and numerical simulation are within 40 K. At the outlet of the combustion chamber, the deviation is only 1.2 K. The temperature deviation of flue gas at the outlet of cooling chamber is 15.6 K. After verification and comparison, it is concluded that the thermal calculation method adopted can be applied to the thermal calculation on double-U flame slag-tap boiler that fully burning high-alkali coal. The flow field is well organized. The recirculation zones formed by swirling flow can increase the movement path of pulverized coal particles in the combustion chamber and promote the burning. When the flue gas flows through the slag collection tube bundle, the temperature greatly reduces. The flow field is also disturbed, which can effectively capture the ash. At variable loads, the velocity field in the boiler decreases proportionally according to the reduction ratio of the amount of coal. However, the size of the recirculation zones is basically unchanged. The temperature level in the boiler reduces, when the amount of coal reduces from 100% to 75%, the flue gas temperature at the outlet of the combustion chamber reduces by about 75 K, and the flue gas temperature at the outlet of the cooling chamber reduces by about 200 K. This study can provide reference for fully burning high-alkali coal in double-U flame slag-tap boiler.