A heat producing device utilizing solid carbonaceous material, especially material of cellulosic composition such as corn cobs, as fuel. The heat producing device includes a gasifier for the carbonaceous material. The gas outlet of the gasifier leads to a burner. A cyclonic burning chamber and particle separator are connected to the discharge of the burner. The cyclonic burning chamber and particle separator has a heat outlet and a particle discharge outlet. An adjustable air inlet and mixing chamber are installed in the heat outlet for adding ambient air to reduce the temperature of the heat discharged from the heat outlet. A discharge fan has an inlet connected to the mixing chamber and an outlet for discharging the heat received therefrom to a drying chamber or other heat utilizing source.