Utility Consumption History: Total Ash Ton/Hr
The total ash produced indicates the total amount of ash currently being produced from the two fluidized bed boilers. The quantity of ash produced varies as the amount of coal varies in response to the university's energy demands.
Ash is made up of minerals in the coal that do not burn. The limestone added in the fluidized bed boilers also ends up as ash. There are two types of ash, bottom ash and fly ash. The bottom ash is made up of larger particles that are removed from the bottom of the boilers. The fly ash is very fine and is carried out of the boiler with the combustion gases. This ash would leave the boiler as particulate or smoke if it was not collected. The fly ash on the fluidized bed boilers is collected with fabric filters or baghouses. The baghouses remove over 99.5% of the fly ash before the combustion gases are discharged out the stack.
All ash is shipped to the Metro Waste Authorities landfill located east of Des Moines. Approximately one third of the ash is used to solidify liquid wastes for disposal in the landfill. The remaining two thirds of the ash is placed in the landfill along with other wastes.