Daily Topic (June 27)

1. The quality of the aerodynamic conditions in the furnace plays a vital role in the safe and economical operation of the boiler. The stability and economy of boiler operation depend to a large extent on the performance of the burner and the aerodynamic conditions in the furnace. It is not only related to the combustion stability of the normal operation of the boiler, but also to the economy of boiler operation and even the safety of the heating surface. The success of the boiler aerodynamic field test directly determines the quality of the aerodynamic conditions in the furnace. Problems such as poor combustion stability under low load, low boiler main and reheat steam temperatures, and local over-temperature on the heating surface due to poor aerodynamic conditions of the boiler can be partly compensated for by operation adjustment methods. However, most of these adjustment methods affect the economic efficiency of boiler operation. For example, commonly used methods to increase steam temperature include moving the flame center upward or increasing ventilation. Although the steam temperature is increased, it also causes local over-temperature on the heating surface, which must be controlled by desuperheating water, and at the same time increases the level of fly ash combustibles. The increase in ventilation volume increases the amount of flue gas discharged from the boiler. * * Increased exhaust heat loss. What is more serious may be that the boiler has poor combustion stability under low load, and oil must be added to support combustion. 2. The impact of fly ash combustibles on boiler operating economy. The amount of fly ash combustibles in boiler operation, that is, the loss of incomplete combustion of fuel, is an important indicator of the economic performance of boiler operation. During boiler operation, the fineness of pulverized coal in the pulverizing system has a great influence on fly ash combustibles. During boiler operation, the excess air coefficient (oxygen content of flue gas) is also an important factor that affects the level of fly ash combustibles. At the same time, the height of the flame center also affects the level of fly ash combustibles by affecting the time the fuel stays in the furnace. In addition, the operating conditions of the pulverizing system, such as the amount of powder carried by the third wind, will also affect the level of fly ash combustibles, resulting in increased losses from incomplete combustion of fuel. 3. The impact of dust accumulation on the heating surface of the boiler on the economical and safety of the boiler operation. Ash on the heating area of ​​the boiler affects the heat exchange of the heating surface, causing the heat absorption of the working medium to decrease, causing the heating surface to overheat, and the boiler exhaust temperature to rise, seriously affecting the efficiency of the boiler. When the dust accumulation is severe, the cross-sectional area of ​​the flue gas flow is reduced, the flow resistance of the flue gas is increased, the power consumption of the induced draft fan is increased, and the operating load of the boiler is even limited or the boiler is forced to shut down. Due to dust accumulation, the temperature of the rear flue gas increases, which affects the safe operation of the rear heating surface. Due to the reduced heat absorption of the soot working material in the heating area, not only the soot heating surface is over-temperature, but also the main and reheat steam temperatures are low during normal operation of the boiler. Measures taken to increase the main reheat temperature during operation by raising the flame center and increasing the furnace air volume not only result in local over-temperature of the heating surface, but also increase the exhaust heat loss and fly ash combustibles, seriously affecting the economics and safety of the boiler operation. Statistics show that about 70% of boiler accidents are "four-pipe" leakage accidents. 4. The impact of continuous and fixed boiler rows on boiler operating economy. The continuous discharge and fixed discharge of boilers are a kind of working fluid discharged by the boiler to the atmosphere under the working pressure of the steam drum. Since the pressure and temperature of the working fluid are high during discharge, the heat loss is very large. Therefore, while ensuring the quality of boiler water and steam, the amount of pollutant discharge from the boiler should be reduced as much as possible. At present, most boilers are designed with program-controlled systems for fixed discharge to achieve program control. After the discharge is completed, the fixed discharge door is closed. When the tightness of each fixed discharge valve is good, the loss of working fluid and heat will not be too great. However, since the continuous-row system always maintains a certain opening during normal operation, the tightness of the continuous-row valves becomes worse and worse under long-term erosion, and the leakage flow gradually increases. Even if the valve is fully closed, the leakage flow still remains. * * Higher than normal sewage discharge volume not only reduces the thermal efficiency of the boiler, but also increases the water replenishment rate. 5. The impact of air leakage from the boiler body and auxiliary systems on the economic operation of the boiler. Air leakage from the boiler body not only increases the heat loss of the boiler exhaust smoke, but also increases the output of the suction fan. In severe cases, it may even cause insufficient air suction in the boiler and limit the full-load operation of the unit, or cause the boiler to be forced to burn with low oxygen, affecting economic operation. The increase in air leakage of the air preheater caused by the abnormal working of the air preheater sealing device is an important aspect. Air leakage in the pulverizing system of the pulverized coal furnace not only increases the tertiary air volume and the output of the powder exhaust fan, but also increases the amount of pulverized material carried by the tertiary air, which increases the level of fly ash combustibles and affects the economical operation of the boiler. The combustion of these pulverized coal in the upper part of the furnace may cause the heating surface of the superheater to overheat.

Optimized boiler operation is the key to achieving stable, efficient, reliable and environmentally friendly combustion. The existing optimal operation control mode generally adopts air distribution and powder distribution, furnace negative pressure fluctuation control, oxygen control, fly ash combustible material control, exhaust gas temperature control, etc. based on the combustion adjustment test report under certain working conditions (including the minimum stable output test without oil injection under the designed coal type).