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This study is a numerical study to predict the temperature of the heat exchange tubes inside the pulverized coal-fired boiler through the conjugate heat transfer analysis. Due to the aspect ratio and number of tubes inside the pulverized coal-fired boiler, actual tube modeling analysis has rarely been conducted. Most of the research has been conducted through the porous media method, resulting in limited information on the temperature distribution of each tube. However, for the development of a digital twin model for improving the performance of the boiler and reducing maintenance costs, information on the local temperature of the tubes is required. In this study, all the tubes inside the boiler were modeled, and conjugate heat transfer analysis was performed to confirm the local temperature distribution. For this purpose, the analysis was conducted using Fluent 2020 r2, and the analysis model was constructed using more than 300 million structured grids. The calculation was performed considering conjugate heat transfer in the pulverized coal-fired boiler, heat exchange by steam inside the tubes, and conductive heat transfer of the tubes. As a result, it was confirmed that there is a significant deviation in the local temperature for each tube position. Furthermore, the maximum temperature of the PrSH tube ranges widely, between 492 and 532 degrees, depending on the tube's position. It was observed that the point of the highest temperature inside the tubes also varies for each tube due to the flow of external combustion gas. Based on these results, it is expected that strategic approaches to boiler design and maintenance can be achieved. Furthermore, it is anticipated to contribute to the high efficiency of power facilities by being utilized as basic data for the development of a digital twin model for the boiler. [ABSTRACT FROM AUTHOR]

Ammonia (NH3), as a derivative of hydrogen and energy carrier, is regarded as a low-carbon fuel provided that it is produced from a renewable source or a carbon abated process of fossil fuel. Co-firing ammonia with coal is a promising option for pulverized coal-fired power plants to reduce CO2 emission. Applying the co-firing in an existing pulverized coal-fired boiler can achieve satisfying combustion performance in the furnace but may affect the boiler performance. In the present work, a thermal calculation method was employed to evaluate the impact of ammonia co-firing on the boiler performance of an existing 600 MW supercritical utility boiler, covering the co-firing ratio range up to 40% (on heat basis). The calculations indicated that, as compared to sole coal combustion, co-firing ammonia changed the volume and composition and consequently the temperature and heat transfer characteristics of the flue gas. These resulted in increased variations in the heat transfer performance of the boiler with increasing of the co-firing ratio. The evaluations revealed that co-firing up to 20% ammonia in the existing boiler is feasible with the boiler performance not being considerably affected. However, the distribution of the heat transferred from the flue gas to boiler heat exchangers is significantly deteriorated at higher ratios (30% and 40%), resulting in over-temperature of the superheated steam, under-temperature of the reheated steam and considerable reduction in boiler thermal efficiency. It implies retrofits on the heat exchangers required for accommodating higher ratio co-firing in the existing boiler. The comparison study showed that co-firing 20% ammonia provides a superior boiler performance over co-firing 20% biomass producing gases and blast furnace gas. [ABSTRACT FROM AUTHOR]

The paper provides an outlook on future directions of research and the possible applications for pulverized coal-fired boilers. One potential direction for future research is to focus on the ways to improve the efficiency of pulverized coal-fired boilers. This could involve developing new combustion technologies that are able to more thoroughly burn the coal and produce less waste or finding ways to capture and use the excess heat that is generated during the combustion process. The pulverized coal combustion process in power boilers is still being improved by the preliminary cleaning of coal and the use of various catalytic additives. Another area of research that could be valuable is the development of advanced control systems and monitoring technologies for pulverized coal-fired boilers. These systems could be used to optimize the performance of the boiler and ensure that it is operating at maximum efficiency while also providing real-time data on the condition of the boiler and any potential problems that may arise. The analysis of literature shows that several future paths of development and scientific research related to the technology of pulverized coal combustion in boilers can be distinguished. [ABSTRACT FROM AUTHOR]

Balanced distribution of air in coal-fired boiler is one of the most important factors in the combustion process and is strongly connected to the overall system efficiency. Reliable and continuous information about combustion airflow and fuel rate is essential for achieving optimal stoichiometric ratio as well as efficient and safe operation of a boiler. Imbalances in air distribution result in reduced boiler efficiency, increased gas pollutant emission and operating problems, such as corrosion, slagging or fouling. Monitoring of air flow trends in boiler is an effective method for further analysis and can help to appoint important dependences and start optimization actions. Accurate real-time monitoring of the air distribution in boiler can bring economical, environmental and operational benefits. The paper presents a novel concept for online monitoring system of air distribution in coal-fired boiler based on real-time numerical calculations. The proposed mathematical model allows for identification of mass flow rates of secondary air to individual burners and to overfire air (OFA) nozzles. Numerical models of air and flue gas system were developed using software for power plant simulation. The correctness of the developed model was verified and validated with the reference measurement values. The presented numerical model for real-time monitoring of air distribution is capable of giving continuous determination of the complete air flows based on available digital communication system (DCS) data. [ABSTRACT FROM AUTHOR]