在燃油锅炉的运行管理中，我们经常会接触到一个词“超低负荷运行”，那么锅炉多大负荷运行才算是超低负荷运行？超低负荷运行有什么危害呢？

In the operation management of the fuel boiler, we often come into contact with a word "ultra low load operation", then how much load of the boiler operation is the super low load operation? What are the hazards of ultra low load operation?

一般锅炉正常负荷变化范围是：燃煤锅炉为额定负荷的70%～100%，燃油锅炉为额定负荷的60%～100%。低于这个范围运行时即视为超低负荷运行。

The scope of the normal load change of the boiler is: 100% to 70% of the rated load, the fuel oil boiler is 60% ~ 100% of the rated load. The lower than the scope of operation that is regarded as a super low load operation.

锅炉超低负荷运行的危害主要有：

The main hazards of the operation of the ultra low load of the boiler:

（1）燃油锅炉水循环可靠性下降

(1) the reliability of boiler water cycle decreased

燃油水循环通常采用自然循环方式。超低负荷运行时，因为锅炉投入燃料量少，整个炉膛温度下降，水冷壁受热减弱，锅炉水循环流速会相应降低，水循环可靠性下降。

Natural circulation mode is usually used in fuel oil water cycle. Low load operation, because the boiler fuel is less, the entire furnace temperature is decreased, the water wall is weakened, the boiler water circulation flow rate will be decreased, and the water cycle reliability decreased.

（2）难以保证蒸汽的品质

(2) it is difficult to ensure the quality of steam

随着锅炉负荷的降低，蒸汽的温度和湿度将会受到影响，尤其是对于有过热器的锅炉而言，当锅炉负荷降低时，出口汽温也随着下降，难以维持额定的汽温，蒸汽品质变差。当过热蒸汽温度下降到低于额定值时，汽水系统受热面工况将进入危险区，这时的负荷被称为技术上的最低允许负荷。

With the decrease of boiler load, temperature and humidity will be affected by the steam, especially for boiler superheater, when the boiler load decreases, steam temperature decreased, it is difficult to maintain the rated steam temperature, steam quality variation. When the superheated steam temperature drops below the rated value, the heating surface of the steam water system will enter the danger zone, when the load is known as the minimum allowable load.

（3）锅炉尾部受热面，如空气预热器、省煤器以及热水锅炉本体的尾部受热面等酸腐蚀加剧

(3) the heating surface of the boiler tail, such as the air preheater, the provincial coal heater and the hot water boiler body, such as the heated surface, such as the heated surface

通常锅炉按正常符合设计锅炉受热面和排烟温度，排烟温度一般都会高于露点温度。超低负荷运行时，炉内各部温度均不同程度下降，最终排烟温度也会降低。极易使低温受热面的金属壁温低于硫酸汽的露点温度，硫酸蒸汽便会在低温受热面上结露，从而造成低温受热面的腐蚀。

Normal boiler according to the normal design of boiler heating surface and smoke exhaust temperature, exhaust gas temperature is generally higher than the dew point temperature. The temperature of each part of the furnace is decreased at different degrees, and the temperature of exhaust gas will be decreased at the low load operation. Easy to make low temperature heating surface of the metal wall temperature below the dew point temperature of sulfuric acid sulfuric acid vapor, steam will be in the low temperature heating surface condensation, resulting in the low temperature corrosion.

因此，燃油锅炉在运行管理中，应尽量避免锅炉超低负荷运行的情况发生。

Therefore, the operation of the fuel boiler in the management, should try to avoid the occurrence of ultra low load operation of the boiler.