The citric acid is easy to cause precipitation during chemical cleaning for thermal power equipments.Thus

a series of experiments simulating the practical chemical cleaning conditions were conducted to figue out the mechanism of precipitation

including the classification of precipitates and the factors affecting the precipitation.Based on the achieved mechanism

the controlling measures were proposed.The results show that

for the high concentration of Fe2+reacting with the unionized citric acid available in solution

ferrous citrate

who has a low solubility

is formed

resulted in precipitation.Under the confirmed cleaning conditions(initial citric acid concentration

pH

temperature)

Fe2+concentration is the dominating factor affecting the precipitation.It is suggested that specific erperiments should be performed to define Fe2+concentration in citric acid cleaning liquid prior to chemical cleaning.A specified anti-sedimentation agent can also be utilized to prevent precipitation.