DRY SCRUBBER ASH
PRB coals will have a lower heating value which will require more coal to be consumed per megawatt/hour; however PRB coals also have a lower ash content.
Coal from the Powder River Basin tends to produce ash with high calcium content, and can be highly reactive when exposed to moisture.
The primary difference in chemical composition between bituminous and PRB ash is the high amount of calcium compounds found in the PRB ash, and the almost non-existent percentage in most bituminous ashes.
PRB ash typically sets up hard in the presence of moisture and produces a buildup of ash handling equipment. Laboratory testing has shown this buildup occurs inside of three minutes.
Dew point temperatures in fly ash dry scrubber baghouses can be as low as 18° F, creating an environment ideal for buildup if the material comes in contact with cool metal surfaces. A completely dry vacuum system is recommended to prevent problems with handling the ash. This can be achieved by blowing heated air through the line prior to conveying. As an alternative to heated air, rubber elbows can be used to prevent buildup in direction changes.
Other precautions must be taken when handling PRB dry scrubber ash in a vacuum system, due to the high moisture and calcium content, and the stickiness of the material. Large diameter ash intakes are used to prevent arching in the hoppers. To prevent blinding the filter bags, PTFE (polytetrafluoroethylene) membrane bags are use in the filter/separator unit. Insulation of the conveying line, exhauster airline, and filter/separator is also recommended. It is also important to maintain dry conditions in the ash storage silo – UCC generally uses flat bottom silos with fabric fluidizing elements. Silo pressure is kept at a slight positive to ensure no ambient moisture enters the silo.
BOTTOM ASH SYSTEMS
United Conveyor offers the broadest range of state-of-the-art dry bottom ash handling solutions. Four different system types – Hydraulic, Mechanical, Pneumatic and Vibratory – have been developed to address the particular characteristics of each individual power plant. With hundreds of installations and nearly 90 years of experience, UCC provides the confidence and peace of mind our customers demand. All of the below options eliminate the need for ash storage ponds.