A rinsing passivation agent for chemical cleaning of power plant boilers and a one-step rinsing passivation process

Abstract

The invention discloses a rinsing and passivating agent for chemical cleaning of utility boilers and a rinsing and passivating one-step process. The rinsing and passivating agent contains, by mass, 25% to 40% of ethylenediaminetetraacetic acid, 5% to 10% of mercaptobenzothiazole, 2% to 4% of sodium hexametaphosphate, 2-5% of thiourea, and balance water. The rinsing and passivating agent of the present invention is simple, safe, non-toxic, and is easy to prepare, rinsing and passivating are performed by one step, the dosage of the agent is low, the rinsing and passivating temperature is low, the time is short, and environmental protection and energy saving are achieved. An excellent passivation film is formed on the metal surface, and the agent is suitable for various cleaning media, such ashydrochloric acid, sulfuric acid, citric acid, EDTA sodium salt and EDTA ammonia salt, and the like.

Description

technical field [0001] The invention belongs to the technical field of chemical cleaning of electric power or chemical industry equipment, and is used for surface rinsing and passivation after pickling of metal surfaces, in particular to a rinsing passivation agent used for chemical cleaning of power plant boilers and a one-step process of rinsing passivation. Background technique [0002] While entering the 21st century, my country's thermal power generation units have also entered the era of 1000MW ultra-supercritical units. In recent years, most of the newly-built units are subcritical, supercritical and ultra-supercritical units. With the increase of unit capacity, great changes have taken place in the unit structure and equipment materials. The requirements for the cleanliness of the heating surface and the water vapor quality of the unit are more stringent. come higher. Chemical cleaning of thermal equipment is a necessary technical measure to clean the heated inner s...

AI Technical Summary

Problems solved by technology

High passivation temperature and long time are common (high energy consumption)

The recommended passivation agent, such as sodium nitrite, has an excellent passivation effect, but because it is a carcinogen, it is easy to cause environmental pollution

The passivation effect of phosphate and polyphosphate is average, and the residue of phosphate will bring hidden dangers to the safe operation of newly built supercritical units and ultra-supercritical units in the future, and will also affect the pH value of the boiler water for a long time after the boiler is started. low

The passivation rinse of hydrogen peroxide can only be rinsed with phosphoric acid and polyphosphate, and it is also easy to cause the disadvantage of passivation of phosphate and polyphosphate after passivation

Hydrazine passivation itself has strong toxicity, and the time is as long as 20 to 50 hours

Dimethyl ketone oxime, acetone or acetaldehyde, the passivation temperature is also high, and the residual drugs are unacceptable for supercritical units

The EDTA oxygenation passivation process is only suitable for EDTA cleaning

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