Introduction

Cleaning tubes / finned tubes contaminated with sulphur, which is brought over as part of contamination from the firing medium, may be seen as creating a corrosion issue that compromises the integrity and efficiency of the equipment. This report aims to highlight the corrosion risks, which have already formed prior to cleaning, but are associated with using water as a cleaning method and suggest a viable solution to mitigate these risks.

Corrosion Risks

The assumed primary corrosion risk associated with cleaning sulphur-contaminated convection section tubes with water is the formation of sulphuric acid. When sulphur compounds, present on the tube surfaces, contact with water they can react to form a mild sulphuric acid solution. In reality, the moist sulphur is already corroding the tubes / finned tubes with its corrosive nature and does lead to severe damage to the metal surfaces of the tubes/fins.
1. Acid Dew Point Corrosion: The presence of sulphur compounds can lower the dew point of the flue gases, leading to the condensation and formation of sulphuric acid on the tube surfaces. This phenomenon, known as acid dew point corrosion, can cause localized corrosion and pitting, which can significantly reduce the lifespan of the tubes.
2. General Corrosion: The sulphuric acid can cause general corrosion of the metal surfaces, tubes and fins. This type of corrosion can lead to thinning of the tube walls, resulting in reduced mechanical strength and potential failure of the tubes under operational conditions.

IGS Tube Tech Solution

IGS Tube Tech cleans convection sections where sulphur is present, using the bespoke Remote Operating Vehicle (ROV) technology. The technology offers rapid removal of deposits, preventing the formation of corrosive levels of sulphuric acid from causing damage. Also, we add a neutralising agent to the cleaning water stream and the effluent catchment area to mitigate the corrosion risks and take the solution to a neutral PH. The agent reacts with sulphuric acid to form a neutral compound. This neutralisation process helps to prevent the formation of corrosive sulphuric acid. Additionally, the neutralising agent can help to maintain a more alkaline pH in the cleaning water, further inhibiting the corrosive effects of any residual sulphuric acid and make the effluent less hazardous for disposal.

Conclusion

Cleaning sulphur-contaminated convection section tubes with water poses perceived corrosion risks due to the formation of sulfuric acid. However, by using Tube Tech ROV technology, with accurate and precise cleaning activity, limits the amount of water in any one area at a time and fouling is removed before corrosion has started, adding soda ash to the cleaning water reduces any further risks. Implement this measure will help ensure the longevity and reliability of the convection section tubes, thereby improving the overall efficiency and safety of the industrial processes.

Rev.1 Aug 25 2024