Power Plants Shifting to Dry Bottom Ash Handling

For years, wet bottom ash handling has been the standard for power plants throughout the world. Systems that use impounded hoppers or submerged scrapper conveyors have traditionally handled ash using water as a primary medium.

Now, however, a growing emphasis on environmentally-friendly production has caused many power plants to reconsider elements of their production process that aren’t green – and that includes ash handling.

Higher costs – including those associated with disposal of waste and other by-products – have driven this paradigm shift. As a result, power plants have thoroughly analyzed their production processes to find ways to minimize waste, achieve efficiency, promote environmentally-friend procedures, and cut costs.

When it comes to ash handling, that means replacing water with another common medium: air.

The result is dry bottom ash handling. These systems frequently continue to burn bottom ash, using ambient air instead of water during the extraction and cooling phases. This results in a lower cost, because there is no need to dispose of or treat the water that is used in a wet process – plus there are lower emissions and heat energy. One study found that total operation cost of a dry system versus a wet one reduced costs by more than 50 percent.

These benefits are why newer plants are considering adopting dry bottom ash handling. For example, there’s a story about a new 800 MW coal-fired plant, located in Germany, that is using a dry bottom ash handling technique known as Drycon instead of traditional water.

In Drycon, hot ash lumps are reduced in size as they fall down the conveyor belt, where they are met by currents of air that fuel the re-burning effect. One by-product: more thermal energy is released that goes back into the boiler to help generate steam.

The owners presumably will be free of water treatment and disposal costs, and claim to take advantage of lower life-cycle costs.

These latest innovations have caused many plant owners to consider converting to dry bottom ash handling conveyor systems and techniques. The benefits could help streamline production, cut costs, and make facilities more environmentally friendly in the process.