Pickling is the main method for removing a large amount of oxidizing substances and corrosion products inside a gas boiler, and also has the effect of eliminating scale. The pickling process is usually carried out after 1-3 weeks of boiler operation. 

1.Cleaning tools

Boiler energy saver, steam drum, water wall, hydrochloric acid, ammonium bifluoride.

2.Cleaning method

1) First, at the beginning of the pickling work, the boiler’s economizer, steam drum and water wall are filled with demineralized water.

2) The boiler is ignited. When the temperature of the boiler rises to 70-80℃, the boiler is turned off, and then the pickling operation can be performed. Before the pickling operation, the superheater should also be recharged with demineralized water until the water overflows into the steam drum to prevent acid or acid vapor from being introduced into the superheater.

3)When the acid is charged into the boiler, the boiler should not be ignited under any circumstances. The steam drum and other venting holes should be opened to remove the hydrogen generated by the reaction of acid and iron. Before making sure that the hydrogen has dissipated, avoid open flames or use electrical equipment that generates sparks to avoid the risk of hydrogen explosion.

4) Finally, after the acid filling is completed, let the boiler and economizer soak for about 6 hours in the solution, then drain the acid and rinse the superheater with demineralized water. The acid is discharged. After the acid is drained, the boiler feed water pump is operated, and the water of one economizer is filled into the boiler to prevent the water supply shutoff valve from leaking.

3.Matters needing attention

The gas boiler can be pickled with 5% hydrochloric acid with 0.25% ammonium difluoride inhibitor added. The acid solution is injected into the boiler through the pickling joint on the steam drum down pipe, and the acid filling of the economizer is carried out through the recirculation pipe. The filling of the acid solution should be carried out until the liquid level in the steam drum temporary water level gauge rises significantly until the liquid level rises above the cyclone separator, but it should be noted that the acid liquid cannot enter the superheater, otherwise it will cause serious damage.