Rainy weather is often the last thing anyone wants to see on the forecast, whether your plans involve a round of 18, a day out on the boat, or a power plant CCR basin closure.
Water, while vital for life, can be an expensive nuisance when it comes at the wrong time and place.
For electric power utilities, closing a CCR basin during rainy season often result in the following scenarios:
- Missed deadlines
- Excessive chemical expenses, and
- Over-budget labor due to out-of-scope ash drying.
But with the help of modern superabsorbent polymer (SAP) technology, saturated coal ash can be efficiently dried and stabilized, despite the local weather patterns.
Traditional CCR Drying Method
Traditional CCR drying methods include:
- “Flipping” and
- Quicklime application (or other cementitious additives).
- Coal Ash Flipping
Flipping is simply the manual turning of stockpiled CCR material with heavy equipment, for the purpose of accelerating the draining of residual water by gravity. During excessively rainy or humid periods, flipping is often insufficient and can require weeks to months of extra labor.
- Quicklime Application
Quicklime exothermically reacts with water and “cooks” the water off, resulting in a dry, stable material; however, excess moisture slows the curing process of quicklime, increases the required quicklime dosage rate, and can cause increased crack formation over time.
Related Article: CCR Stabilization with Superabsorbent Polymers
Why Superabsorbents?
When SAPs are blended into saturated CCR material, at very low dosage rates (0.25%-1.5% by weight), SAP particles absorb the free liquid within minutes, removing the liquid from the ash matrix and modifying the thixotropic properties of saturated CCR. In other words, SAPs transform unstable “liquid” ash to a “dry” stackable solid that can be easily loaded, transported, and landfilled.
Related Article: 5 Myths About Superabsorbent Polymers for Waste Solidification
Furthermore, SAPs remove excess water from the exothermic reaction with quicklime, allowing minimized lime dosage rates, faster curing times, and reduced crack formation in the stabilized mixture. Initial lab testing and field applications at active CCR sites have demonstrated that the quicklime dosage rate can be decreased by 3-5% with a minimal SAP amendment rate (0.3%-0.7%), resulting in potential cost savings of $10,000-$20,000 per 10,000 cubic yards of treated CCR. For a 500,000-ton CCR excavation, that equates to $500,000 to $1,000,000 savings, in chemical costs alone over the life of the project.
Wet weather is a given and cannot be avoided, but with the help of modern superabsorbent polymer (SAP) technology, saturated coal ash can be rapidly dried and stabilized within predictable timeframes and drastically reduced quantities of drying chemicals, despite the local weather patterns.
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