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Operating factors affecting the flue gas temperature at the boiler outlet: 1. The impact of changes in the degree of slagging and soot accumulation on the heating surfaces on the flue gas temperature at the furnace outlet. This phenomenon is unavoidable, especially since overly large coal powder particles exacerbate coking and worsen the heat transfer process inside the furnace. This causes an increase in the flue gas temperature at the furnace outlet. Another instance was a change in wind temperature, which raised the temperature in the combustion zone and led to slag formation on the heat-exchanging surfaces. This not only affected the heat transfer in those surfaces but also caused an increase in the flue gas temperature at the furnace outlet; worse still, it could damage the burners. 2. The effect of changes in boiler load on the flue gas temperature at the furnace outlet. During operation, changes in the boiler load lead to variations in fuel consumption; as a result, the shape and values of the temperature field within the furnace also change, which in turn causes changes in the amount of radiation heat transfer within the furnace. However, the magnitude of these changes in radiation heat transfer is not equal to the magnitude of changes in fuel consumption. According to the experiments, when the boiler load changes from half load to full load, the load increases by 100%; the average flame temperature in the furnace rises by about 200°C, and the radiant heat transfer in the furnace increases by around 70%. This indicates that the rate of change of radiant heat transfer within the furnace is less than the rate of change of load. Therefore, as the boiler load increases, the exhaust gas temperature at the furnace outlet rises. 3. Effect of changes in the excess air coefficient on the flue gas temperature at the furnace exit. The effect of the excess air coefficient is very significant, for two main reasons. Firstly, an increase in the excess air coefficient leads to an increase in the amount of heat-absorbing material inside the furnace, thereby increasing the heat capacity of the flue gases. This results in a decrease in the temperature at the flame center, as well as a shift of the flame center upward. As a consequence, the flue gas temperature at the furnace outlet rises. If the excess air coefficient increases significantly, the heat absorbed by the air supplied to the furnace due to its heating by the flame exceeds the reduction in radiant heat transfer resulting from the decrease in the average temperature of the flue gases inside the furnace; in such cases, the flue gas temperature at the furnace outlet decreases. Secondly, changes in the excess air coefficient also alter the physical properties of the ash, as the ash melting point of certain coal types is related to the \"atmosphere\" of the flue gases; a oxidizing atmosphere results in a lower melting point compared to a reducing atmosphere. This leads to more severe slagging on the heated surfaces near the burner, thereby increasing the exhaust gas temperature at the outlet of the furnace. Therefore, during the operation of the boiler, a proper negative pressure should be maintained to reduce air leakage from the boiler. 4. Effect of flue gas recirculation condition on furnace exit temperature. The position at which the recirculated flue gas is introduced into the furnace varies, and different amounts of recirculated flue gas have different effects on the flue gas temperature at the furnace outlet; therefore, this can be used as a means to adjust the steam parameters of the boiler.