A rotary bottom ash regenerating (RBAR) system [100] comprises a cylindrical body [110] that receives ash [17] containing reactant particles [10] that are partially reacted limestone compounds having unreacted cores [13] from a furnace. Sensors [140] sense physical parameters within the cylindrical body [110]. A controller [170] receives the output of the sensors [140] and information indicating the amount of unreacted core [13] and causes a fluid actuator [135] to spray a proper amount of regeneration fluid regulator [135] from a plurality of spray nozzles [131] to different locations within the cylindrical body [110] to regulate the temperature and to cause the reactant particles [10] to have a require content of regeneration fluid. This causes the reactant particles [10] to be regenerated and reused. This results in a lower limestone costs and less overheating of ash handling systems.