Boiler cleaning technology innovation: one-step pickling procedure optimization experiment and practical application

Special Engineering Department/Alger Lyu

Summary

It has been 33 years since the Berlin company began to clean boilers. It has cleaned more than 20 boilers in total. Berlin has its footprints from north to south. Because the predecessors planted trees, the descendants can enjoy the shade.

After so many years of work experience and technology accumulation, we have reached a technological watershed. Starting in 2019, cleaning technology in Taiwan began to change. The cleaning process before 2019 (Zhongding & Mitsubishi Heavy Industries of Japan) is divided into water washing → degreasing → water washing → pickling → secondary pickling → neutralization and rust prevention. The cleaning process after 2019 (Qiyi Company – General Electric Company) is divided into For water washing → degreasing → pickling → water washing → neutralization and passivation.

In response to the needs of the times, Berlin’s cleaning technology must also be improved and changed, and it began to plan this one-step experiment and engineering application, which requires VGB’s cleaning procedures and corrosion rates.

1. Berlin Company – History of Boiler Cleaning Project

2. Main reasons for boiler cleaning

After completing the installation of the preheating boiler and boiler group, the internal surfaces of the relevant equipment and pipelines should be cleaned of iron filings, rust and dirt so that they do not contain any oil seals to avoid the above-mentioned problems in the subsequent operation of the preheating boiler system and boiler. Any problems may occur due to residues.

3. Boiler cleaning cleaning process

Chemical cleaning using alkaline solutions is to remove residual oil and butter, while acid cleaning is to circulate a suppressed chemical solution with a specified concentration in the entire boiler that has been preheated to a specified temperature to remove iron filings. and other dirt deposited inside the boiler.

After chemical cleaning, neutralization and passivation are carried out in the boiler to neutralize residual chemical solvents and prevent metal rust during subsequent restoration work.

4. Small experimental test of one-step pickling

4.1 Purpose of cleaning

The one-step pickling method can reduce cleaning time and waste water volume. The original HCL cleaning process is water washing → degreasing → water washing → pickling → secondary pickling → water washing → neutralization and passivation. It is necessary to optimize the original HCL cleaning process from multiple cleaning solutions to one cleaning solution, and transform the boiler cleaning technology into a green industrial technology.

The original HCL cleaning process is water washing → degreasing → water washing → pickling → secondary pickling → water washing → neutralization and passivation. The cleaning process of the new method is changed to water washing → degreasing → pickling → neutralization and passivation → water washing, all of which are completed by the same cleaning solution.

4.2 The test conditions for the one-step pickling small-scale experiment are as follows. The test material is JIS STB410, non-heated, immersion type, and the volume of water is 1.5L.

4.3 One-step small experimental test (appearance before cleaning)

4.4 One-step small experimental test (degreasing operation)

4.5 One-step small experimental test (pickling operation)

4.6 One-step small experimental test (neutralization and anti-rust operation)

4.7 One-step small experimental test (blow-drying operation)

4.8 One-step small experimental test conclusion:

The experimental test ended on May 27, 2023. After the surface was dried, it was sealed in a transparent plastic bag and the rust on the outer surface was observed daily. The photo on the left shows the appearance condition observed on 2023/07/14.

5. Actual implementation cases of large-scale components

   Project name: DRAGON STEEL electric furnace A dust collection elbow pickling project

5.1 HCL one-step pickling, the conditions are as follows, no heating, circulation type, volume water volume 2525L.

5.2 DRAGON STEEL Electric Furnace A Dust Collection Elbow Pickling Project-Pipeline Configuration Operation

5.3 DRAGON STEEL Electric Furnace A Dust Collection Elbow Pickling Project – Internal Surface Before Cleaning

5.3 DRAGON STEEL Electric Furnace A Dust Collection Elbow Pickling Project – Internal Surface Before Cleaning

5.3 DRAGON STEEL Electric Furnace A Dust Collection Elbow Pickling Project – Internal Surface Before Cleaning

5.4 DRAGON STEEL electric furnace A dust collection elbow pickling project – cleaning operation in progress

5.5 DRAGON STEEL electric furnace A dust collection elbow pickling project – internal surface after cleaning

5.5 DRAGON STEEL electric furnace A dust collection elbow pickling project – internal surface after cleaning

5.5 DRAGON STEEL electric furnace A dust collection elbow pickling project – internal surface after cleaning

5.6 One-step cleaning results of DRAGON STEEL Electric Furnace A dust collection elbow pickling project

5.6.1 Corrosion rate of test piece

1. The corrosion rate results of this one-step cleaning are 13.524 (g/m²)and 11.152(g/m²), which conform to the VCB cleaning specification ≦20g/ m²。
2. The visual inspection of the surface appearance after cleaning is satisfactory.

5.6.2 One-step risk assessment

1. During the neutralization operation, a large amount of iron ion sludge will be deposited, which may not be completely discharged smoothly.
2. The sludge produced will adhere to the surface of the pipe wall and cannot be rinsed off. It requires manual wiping. However, after wiping, the surface will not rust after being dried.
3. The problem of sludge adhesion still needs to be improved in the future.