Ash handling in pneumatic conveying can create problems such as wear, dust, plugging, and erosion. It’s essential to consider each of these problems and how to avoid them, as resulting damage can be expensive and time-consuming to correct. In this article, we’ll look at each problem and how it can be minimized when conveying fly ash.
What is Fly Ash?
Fly ash is a byproduct of coal combustion and is composed of the fine particles of burned fuel released from coal-fired boilers along with flue gases. Fly ash can be mixed with lime and water to create a material similar to Portland cement, improving its strength and making it easier to pump. This makes fly ash a useful product in blended cement and hollow blocks as well as other building materials.
Fly ash used to simply be released into the atmosphere, but new environmental standards now mean that emissions have to be captured and cleaned using air pollution control equipment.
Four Considerations when Handling Fly Ash
Pneumatic conveying systems often encounter challenges due to the small particle size and abrasiveness of fly ash. Typical challenges that can result in unwanted cost and wasted time, include:
- Wear: Fly ash contains silicon dioxide, which makes it highly abrasive and frictional. As it slides on and impacts the pipes or tubes within the system, fly ash wears them down and results in the need for repairing or replacing system components. This is especially the case for material traveling at high velocity. The solution: consider ceramic-lined or ceramic-coated system components such as Ceram-BackⓇ elbows, and use a pneumatic conveying test to check the velocity of your system is optimized.
- Plugging: Systems containing fly ash can get clogged up, known as plugging, especially if the material is moved too slowly through the system or if it is exposed to moisture (fly ash is hygroscopic, meaning it absorbs moisture from the air). This impedes flow and limits how much material gets through the system at any given time. The solution: use a pneumatic conveying test to check the velocity of your system is optimized. This test will tell you the line pressure and size that should be used.
- Dust: Due to the fine particle size and aeratable characteristic of fly ash, dust generation can be an issue particularly at any transfer points within a system. Dust is not only annoying, but exposure to it can also be unsafe. It is also combustible as it contains unburned carbon, so there is the potential for explosions. The solution: handle fly ash gently so it doesn’t get overly aerated and follow the Occupational Health & Safety Administration’s (OSHA) dust generation control policy.
- Environmental: Releasing uncleaned fly ash into the atmosphere is harmful to water, land, and animals, including human beings, and is costly to remove. With our growing ecological awareness, we now know that it’s important to have an environmentally safe conveying system. It’s estimated that 22 millions tons of fly ash produced annually in the US is recycled. The solution: pneumatic conveying systems should be completely enclosed.
If you’re building a new system for handling fly ash, it’s critical that it’s designed properly and take into consideration all the challenges you could experience and how to overcome them. It’s especially critical to start out with the correct velocity and pressure in your system and ensure that the components you use are fit for purpose - i.e. they are the correct size and made of suitable material - to avoid many of the challenges you could experience and increase system capacity.
With the many challenges involved when handling fly ash, it’s best to talk to an expert. At Progressive Products, we can help you understand which material and which components are right for your system. Contact us today.