Chemical foam cleaning of gas turbines in a power plant

Name of the service: Chemical cleaning of gas turbine compressors using the foam method

Date: April – May 2024

Name / facility: Power plant, GE 7FA gas turbines

description of the problem

A power plant in the US, owned by a major energy company, encountered serious problems with deposits on the compressor blades of the GE 7FA gas turbines. These deposits were restricting the compressors‘ throughput, which directly affected the turbines’ efficiency and reduced the power generated by the turbine units. During the inspection, a deposit was noticed on the compressor surface. This was caused by a faulty air filtration system and the incorrect application of raw water in the fogging process.

removal of compressor blade with deposits

The client initially decided to carry out the cleaning operations himself. After performing a water flush, a slight improvement was found, but this did not solve the problem. The power plant management contacted Ecol North America, who already had experience in chemical cleaning of turbines gained from other projects.

the proposed solution

Chemical cleaning of gas turbine compressors using foam as an active substance carrier was proposed, enabling the effective removal of difficult-to-wash deposits such as sodium, calcium and silicon, responsible for the decrease in equipment performance. The foam cleaning technology, developed by Ecol, was designed to restore optimum operation of the turbines and compressors without affecting their internal surfaces.

During the preparatory phase of the project, a vision was held, on the basis of which a comprehensive action plan was prepared, as well as a modification project for the implementation of the envisaged solutions.

The turbine was mechanically prepared for foam injection. A process monitoring system and measuring station have been installed. The purpose of this is to protect the turbine components and the need to control and monitor the entire process and its physical and chemical parameters. Finally, the agent was applied using connected nozzles.

what you need to know: the impact of sediment

effect of deposits on the performance of gas turbine blades

• The turbine blades are designed in a lobe shape to ensure optimum performance.
• Sediment changes the shape of the blades and flow channels, which affects their aerodynamics.
• The increased roughness of the blade surface causes an increase in surface area, which promotes further deposition of contaminants.
• Sediment restricts the free flow of air which reduces the efficiency of the blades and leads to an overall decrease in turbine efficiency.
• Deposits can also contribute to corrosion and fatigue due to stress.
• In gas turbines (GT), deposits can further clog the cooling channels of the blades, negatively affecting their durability.

general progression of implementation stages:

1. Sediment analysis: As a result of not being able to sample the turbine deposits on site, data from previous analyses from the Washington Energy Facility were used, allowing the selection of appropriate chemical solutions.

2. Process preparation: The Ecol team carried out the planning and preparation of the chemical installations.

3. Test feeding of foam due to: Detecting possible problems at the initial stage, checking that the foam has the correct consistency during the injection process into the compressor and testing the process assumptions used, related to the modification of the initial parameters in terms of optimising performance.

4. Cleaning process: Chemical cleaning of turbine compressors using foam was carried out, removing harmful deposits from the blades and rotor.

5. Neutralisation and passivation: After cleaning, the entire turbine surface was neutralised and passivated to protect it from further corrosion.

6. Performance measurement: The client compared the performance of the equipment before and after cleaning, taking into account identical weather conditions.

results / conclusions

Following the maintenance work, the turbines at the power station have regained their nominal capacity.

Performance was measured in April 2024 before cleaning and again in May 2024 after cleaning.

Increased actual power: The output of turbine 1 increased by 8 MW and turbine 2 by 9.5 MW. The chemical cleaning process alone was responsible for an increase of 5 MW for turbine 1 and 6.5 MW for turbine 2. The power parameters in both cases returned to nominal power.
Removed deposits: 89.8kg of deposits was removed from turbine 1 and 92kg from turbine 2. This is a key element that has helped to improve airflow and recover the full efficiency of the turbines.

conclusions:

The implementation of this project has highlighted the advantages and effectiveness of the chemical cleaning method for gas turbines developed by Ecol, which has contributed to improving the energy efficiency of power plants. This is a milestone in the commercialisation of this technology, which fits in with decarbonisation efforts and promotes sustainability in the energy industry.

CO₂ limit

deposits in turbines and compressors contribute to economic losses

Deposits in turbines and compressors contributes to economic losses due to reduced plant efficiency. Just as importantly, they lead to unnecessary greenhouse gas emissions (CO₂), which has a direct negative impact on the environment. Keeping flow systems clean results in more efficient use of fuel power and energy production, which translates into not having to emit thousands of tonnes of CO₂ into the atmosphere.

curiosity: estimated emissions CO₂ by a particular type of power plant:

450 kg CO₂/1MWh → gas turbine with simple cycle
750 kg CO₂/1MWh → the latest large supercritical coal blocks
900 kg CO₂/1MWh → old generation coal-fired units
1100 kg CO₂/1MWh → old generation lignite-fired unit

summary

The implementation was a multi-dimensional project, based not only on cleaning, but also on the effective management of logistics and execution of the work. It is also an example of the successful implementation of organisationally and technologically complex projects in energy and industry.

The main advantage of chemical cleaning with active foam over other methods of cleaning gas turbine compressors is the time taken to perform such a service, which is at least several times shorter, which also makes such a process more efficient from an economic point of view.

The realised service has become another milestone in the commercialisation of chemical cleaning of gas turbines. It is one of Ecol’s technologies that fits in with environmental responsibility through decarbonisation, a process of reducing carbon dioxide (CO2) emissions into the atmosphere, which is key in the fight against climate change. In the context of energy, this means reducing CO2 emissions per unit of energy produced, in this case per megawatt (MW). This is achieved by introducing more efficient technologies, using renewable energy sources and optimising industrial processes.

By using advanced cleaning methods for turbines and compressors, we can increase energy efficiency and reduce the consumption of fossil fuels, which directly translates into a reduction of harmful gas emissions into the atmosphere. This approach not only supports the fight against climate change, but also promotes sustainability in the energy industry.

Never give up on what you believe in

After 30 years of believing in cleaning gas turbines with foam, the opportunity came to perform this type of service in Denver. Ecol and the client also believed in the idea and wanted to give it a try. It’s a great success story. I could have given up on the idea many times over the years, but I was determined to make it happen. Thank you to everyone involved in making it happen. Together we have opened the door. Now there will be many more projects to come.
– Danny Foster, Chief Operating Officer, Vice President Ecol North America.

good to know: sources of deposits

sources of sediment and pollution

sources of sediment and flow path contamination in different types of turbines or compressors:

steam turbines

substances dissolved or suspended in the steam entering the turbine (impurities from the water (e.g. silica; hardness); salts (e.g. sodium; phosphates); metals (e.g. copper); corrosion products from the boiler (e.g. iron oxides), etc.).

gas turbine air compressors:

airborne substances (ambient dust, ash, soil, bio-particles, oil from leaking bearing housings; scale/debris from water injection (fogging), turbine cleaning with offline and online methods, raw water intake from evaporative coolers)

gas turbines:

combustion residues from fuel combustion combined with airborne substances (see above)

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