Online water washing based on the presence of corrosives in inlet air

Dale Davis, Rahul Chillar, Eric Gebhardt of GE have been awarded a patent for a waterwash system that incorporates a corrosive measurement system to decided when waterwashing needs to be done. Below are excerpts from their patent application.

Water wash systems are commonly used to remove contaminants and reduce corrosives on the compressor. Some water wash systems operate while the turbomachine operates. These are commonly referred to as "on-line" water wash systems. On-line water wash systems typically use de-mineralized water (hereinafter "de-min water") to clean the compressor. However, a cleaner stronger than de-min water is required to reduce or eliminate some corrosives. Determining when to operate an on-line water wash system may aid in reducing the level of corrosion developing the compressor. 

Some known systems require an offsite analysis to determine the level and types of corrosives entering a compressor. These systems delay the start of mitigation efforts. These systems may not be directly linked with the mitigating actions. 

There is a need for a method that analyzes, in real-time, the level of at least one corrosive within an airstream entering the compressor. The method should determine whether a mitigating action should be implemented. The method should link the analysis of the corrosives in the airstream with operation of the on-line water wash system. 

The cleaning solution may be an acidic solution to reduce corrosion of a caustic nature. Alternatively, the cleaning solution may be a basic solution to reduce corrosion of an acidic nature. 

Generally, the water wash system may operate as follows. An operator may initiate the on-line water wash system which triggers a rinse cycle that uses at least one cleaning fluid. Next, a wash cycle commences; which may include at least one cleaning solution comprising the at least one cleaning fluid and at least one cleaning agent. Additional rinses may follow to rinse away some of the corrosives and the cleaning solution from the compressor. 

The corrosives are separated from the sample air by dissolving in water or cooling through a heat exchanger, and the pH checked to determine if the corrosive is acidic or basic.

A chemical agent can be mixed with a cleaning fluid, creating a cleaning solution that may reduce the level of corrosive deposits on the compressor. Here the clean solution may be considered mildly basic. If the operating environment of the turbomachine is caustic in nature, then the deposits on the compressor may be caustic in nature. The mildly acidic cleaning solution may react with the basic deposits on the compressor, neutralizing, and possibly mitigating the corrosion. 

Then depending on the results of this unit, the online waterwash system may be triggered, either manually or automatically.