A furnace system includes a furnace and a preheater configured to preheat material before it enters the furnace. The system further includes a duct system including a mixing chamber disposed between the furnace and preheater. The duct system further includes an exhaust duct in fluid communication with an exhaust fluid outlet of the furnace and configured to vent fluid exhausted from the furnace. The exhaust duct is in fluid communication with the mixing chamber and configured to redirect a portion of the fluid exhausted from the furnace to the mixing chamber. The duct system further includes a preheater duct in fluid communication with the mixing chamber and a fluid inlet of the preheater and configured to direct fluid from the mixing chamber to the preheater. The system further includes a duct scraper configured for movement within the mixing chamber to move particulates from the mixing chamber into the exhaust duct.