Reduction Of Drum Level Deviation And Error In 600 MW Subcritical Boiler

Because of the changes of boiler load, combustion conditions, feed water rate, recycle pump and sootblowing, drum level often changes. Higher drum level or its sharp change can result in worse quality of water steam or water liquid into steam, which might cause salt deposit or water induction or blade failing. Lower drum level can cause blowdown invalidation and additive agent into steam and steam in common downcomer, which impact water recycle and might cause wallbube leak. Thus reduction of drum level deviation is one of important work to boiler unit safe operation.Dynamic characteristics of drum level was analyzed firstly and the analysis was carried out from two aspects:measurement and boiler operation. Status of drum install and downcomer, combusiton deviation and hydrodynamic force deviation effected the water levels of the two sides of the drum. Aiming at the measurement principle of the stage gauges, the causes of measure error were analyzed.Basing on the deviation conditions of drum levels in the 600MW subcritical boilers in Guohua electric power Co., experimental researches were conducted. The boiler operation conditions were researched as the influencing factors of drum level deviation and the focal factors were burners swing angles, mill running mode and recycle pumps running mode. The results provided the theroy directions to reducing deviation of drum levels. The special improving work was conducted in the No.1 boiler. And the effects of improving work were good by retrofiting the stage gauges and combustion tuning.The control measures of drum level deviation were researched finally. It was depicted and summarized the methods and the effects covering many aspects including combustion tuning, measurement contorl loop, measurement management and install and control optimization.