Dry Ice Blasting is a Solution for Cleaning a Heat Recovery Steam Generator (HRSGs)
In combined-cycle power plants, heat recovery steam generators (HRSGs) are intricate, expensive, and important systems. In order for the plant to operate efficiently, these generators must be kept clean. But with so many cleaning methods and options available, which one is best?
What is a HRSG?
HRSGs are the thermodynamic links between the gas turbines and steam turbines. They’re custom-engineered and installed to meet the specific operational and performance requirements.
A well-designed HRSG unit is designed to withstand heavy cycling operations and strategically reduces the cost of electricity. It’s also engineered to be incredibly reliable and flexible. Common types of HSRGs include:
- Horizontal drum units. This is by far the most popular type. Gas flows horizontal while water is heated in vertically arranged tubes. This produces a natural circulation effect.
- Vertical drum units. In this system, gas flows vertically across horizontal evaporator tubes. This type of system uses a drum, which is ideal when space is at a premium. Vertical drum units are often used for oil applications.
- Horizontal once-through units. This type of system is basically the same as the standard horizontal HRSG, except that it doesn’t require a high-pressure drum. As a result, it’s far more flexible and efficient. It can support unlimited daily cycling.
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Cleaning HRSGs Using Dry Ice Blasting
Precautions Needed When Cleaning a HRSG
HRSGs must be thoroughly cleaned on a regular basis. Cleaning helps remove deposits and corrosion, which can reduce performance and drive up costs. For many years, the standard options for cleaning have included high-pressure water blasting, grit blasting, and CO2 blasting. However, extreme caution must be taken when using these methods.
With each of the aforementioned methods, there’s always the risk of accelerating tube corrosion, leaving behind deposits, or pushing removed deposits into inaccessible areas of the HRSG. High amounts of pressure can also damage tube fins and other sensitive parts. Because of this, dry ice blasting has quickly become the preferred method.
Benefits of Using Dry Ice Blasting for Cleaning HRSGs
Dry ice blasting is a simple, yet effective process. Some of the specific benefits include:
- The beauty of dry ice blasting is that the dry ice transitions straight from a solid into a gas. In other words, it bypasses the liquid phase. This makes it a totally clean process.
- No abrasion. Dry ice blasting is much like sandblasting, except that there’s no abrasion. This improves the longevity of HRSGs without prematurely damaging key system components.
- No entrapment. With sand or other particulate matter, there’s virtually no risk of entrapment. Unlike other methods that can force small debris back into inaccessible areas, dry ice blasting keeps the HRSG free of material.
- Entirely safe. Considering that dry ice sublimates into the environment, it’s a totally safe and clean process for everyone – including employees, equipment, and the local environment.