¦ENGINEERING
PHOTO: JENIKE & JOHANSON INC.
GETTING BIOMASS ASH TO FLOW AGAIN
A project at Dominion Energy’s Altavista, Hopewell and Southampton power stations solved the facilities’ biomass fly ash handling challenges. BY JAYANT KHAMBEKAR, JOSH MARION AND RIAD DANDAN
M
odern power stations are increasingly looking at renewable fuel sources such as biomass. While using biomass as fuel provides several benefits, the combustion ash can be particularly challenging to handle compared to the typical ash from coal combustion. Biomass fly ash can be highly cohesive and frictional, and can set up in the silo like concrete. To solve ongoing issues related to fly ash, three power stations operated by Dominion Energy followed a
systematic and scientific approach to design biomass fly ash handling systems that provide reliable flow. Dominion Energy is one of the major power generation companies in the U.S. At Dominion, focus is always on progress and using the latest scientific technology to do things in an improved manner. Recognizing the need of time, Dominion converted three of its existing coal-fired power stations in Virginia—the Altavista, Hopewell and Southampton Power Stations—to 100%
Figure 1: Original fly ash unloading silo (top); arrangement below the silo outlet (bottom). PHOTO: JENIKE & JOHANSON INC.
biomass fuel. These facilities use wood chips and waste wood as fuel and each can produce up to 51 MW of electricity. The three stations have similar biomass handling systems. At each of them, fly ash generated is first collected in ash hoppers and is then pneumatically conveyed into an ash unloading silo. The ash is fed into the unloading silo at temperatures between 250 and 300 degrees Fahrenheit and then sits in the silo until a truck arrives at the site. The storage time without discharge can vary from four hours up to two days. The original ash unloading silo’s intended use was for coal fly ash. It consisted of a 26-foot diameter cylinder section, followed by a conical hopper (made from carbon steel—no liner) that converged at 36 degrees
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26 BIOMASS MAGAZINE | ISSUE 1, 2021
