Ash is a difficult material to handle. And an expensive one—the conveyors that collect it must be replaced every few years due to the conditions they operate in. But companies can reduce expenses associated with maintaining an ash handling system and increase their lifespan by installing a well-designed conveyor.
Challenges in Ash Handling: Temperature and Acidity
Designing a conveyor to handle ash well while minimizing operational costs is a challenge due to harsh conditions the conveyor must operate in: high temperatures, high acidity, high abrasion, and explosions all work against system efficiency.
High temperatures speed corrosion and cause thermal expansion, which affects how the conveyor’s components perform. Thermal expansion can be especially problematic if the engineers who design the conveyor don’t understand it. When they don’t understand it, they won’t, for example, design the chute connections to the furnace properly, and the connections will break.
Breaks in improperly welded joints also cause problems when they allow the hot, acidic water to leak. Not only is the water a problem in the conveyor, where it corrodes internal components, but it becomes a hazard to workers and corrodes the outside of the conveyor.
Challenges in Ash Handling: Abrasion
Abrasion in ash handling systems largely occurs from the ash, which has sharp edges like glass. Due to the mechanical wear ash produces, maintenance crews must often replace conveyor parts. As burdensome as this is, conveyor manufacturers will at times exacerbate the issue by using wear parts that are difficult to renew. Shutdowns of up to a week are not unheard of while renewing these systems (as unacceptable as it is in a high-production environment).
Challenges of Ash Handling: Explosions
Clinkers (chunks of ash) cause problems in conveyors when they create an explosion, which sometimes happens when they’re dropped into the water. The explosion often deforms the conveyor box because the sides aren’t strong enough. Once the sides deform, the chain guidance system doesn’t work correctly, and wear increases.
Explosions are made worse when the steam isn’t vented properly, which occurs too often in ash handling systems. Some manufacturers even foolishly try to contain the steam in the conveyor. This just forces it into the furnace.
Addressing the Challenges of Ash Handling
Reducing Abrasion
Wear and damage are inevitable in ash handling systems, but we’ve come up with ways to make maintenance easier and less costly. We designed the cheaper and easier-to-replace parts, like a low-cost, standard chain, to bear the wear in our conveyor. And we make these parts easily accessible. Other examples include the drive sprockets and paddles. We use segmented, three-piece drive sprockets so maintenance personnel can replace worn segments without removing or breaking the chain. Our paddles connect to the chains via bolt-on frames that personnel can quickly disassemble and replace.
To make repairs less frequent and increase wear life, we add AR plating on the floor and AR wear liners to support and guide the chain. AR wear liners will outlast the chain by a large factor.
We furthermore reduce wear by keeping the paddles off the floor and sidewalls, and we ensure the conveyor chain runs as slow as possible. Running the chains slow reduces wear by minimizing mixing. Less mixing improves the removal rate of ash and reduces the breakdown of clinkers. It’s best to remove the clinker in a large format before it breaks down into tiny pieces that cause even more wear—clinkers don’t get inside the chain rollers; fine grit does.
Explosions and Corrosion
To address clinker explosions, we control the steam released through special vents that return the water to the conveyor. We also build the conveyor box extremely strong: each sidewall has ten bends. Using stainless steel further increases the conveyor’s strength, and it allows the conveyor to resist corrosion. (We offer galvanized steel, which is cheaper, but it will not last as long.)
To further address corrosion, we elevate the tail just like the head so the take-up system, sprockets, and bearings are not under water.
Conclusion
Due to the harsh conditions, ash handling systems will always require frequent maintenance and repair. But by investing in a well-designed system, manufacturers can reduce the cost of replacements and increase the lifespan of the conveyor. By allowing wear on low-cost parts, the price of replacements goes down. Making these parts easily accessible results in less downtime. A strong box and rust-resistant materials ensures the integrity of the systems remains, increasing how long the system can be used before needing replaced.
