A hearth furnace for producing direct reduced iron, comprising: a first combustion chamber; a first rotating hearth within the first chamber configured to receive onto its surface iron oxide materials from a first chamber inlet disposed over the first rotating hearth; and a first set of rabbles disposed over the first rotating hearth to interact with the iron oxide materials, the first set of rabbles configured to push the iron oxide materials on the surface of the first rotating hearth towards a first chamber outlet located towards one of an inside edge of the first rotating hearth or an outside edge of the first rotating hearth as the hearth and the first set of rabbles move relative to one another, the first set of rabbles being configured to interact with the iron oxide materials over the entirety of the surface of the rotating hearth between the inside and outside edge of the first rotating hearth; a second combustion chamber; a second rotating hearth within the second chamber, the second chamber having a second chamber inlet connected to the first chamber outlet of the first combustion chamber and configured to receive materials pushed to the first chamber outlet and direct the materials onto the second rotating hearth of the second combustion chamber; a second set of rabbles disposed over the second rotating hearth of the second combustion chamber, the second set of rabbles configured to push the materials received from the first combustion chamber onto the surface of the second rotating hearth towards a second chamber outlet of the second combustion chamber located towards one of an inside edge or an outside edge of the second rotating hearth of the second combustion chamber as the second hearth and the second set of rabbles moves relative to one another, the second set of rabbles being configured to interact with the received materials over the entirety of the surface of the second rotating hearth of the second combustion chamber between its inside and outside edges; and one or more gas transfer channels connecting the first and second combustion chambers, the gas transfer channel being wider than the chamber inlet of the second combustion chamber and configured to transfer reduction gases and heat from a reduction reaction of the received material in the second combustion chamber to the first combustion chamber. a first combustion chamber; a first rotating hearth within the first chamber configured to receive onto its surface iron oxide materials from a first chamber inlet disposed over the first rotating hearth; and a first set of rabbles disposed over the first rotating hearth to interact with the iron oxide materials, the first set of rabbles configured to push the iron oxide materials on the surface of the first rotating hearth towards a first chamber outlet located towards one of an inside edge of the first rotating hearth or an outside edge of the first rotating hearth as the hearth and the first set of rabbles move relative to one another, the first set of rabbles being configured to interact with the iron oxide materials over the entirety of the surface of the rotating hearth between the inside and outside edge of the first rotating hearth; a second combustion chamber; a second rotating hearth within the second chamber, the second chamber having a second chamber inlet connected to the first chamber outlet of the first combustion chamber and configured to receive materials pushed to the first chamber outlet and direct the materials onto the second rotating hearth of the second combustion chamber; a second set of rabbles disposed over the second rotating hearth of the second combustion chamber, the second set of rabbles configured to push the materials received from the first combustion chamber onto the surface of the second rotating hearth towards a second chamber outlet of the second combustion chamber located towards one of an inside edge or an outside edge of the second rotating hearth of the second combustion chamber as the second hearth and the second set of rabbles moves relative to one another, the second set of rabbles being configured to interact with the received materials over the entirety of the surface of the second rotating hearth of the second combustion chamber between its inside and outside edges; and one or more gas transfer channels connecting the first and second combustion chambers, the gas transfer channel being wider than the chamber inlet of the second combustion chamber and configured to transfer reduction gases and heat from a reduction reaction of the received material in the second combustion chamber to the first combustion chamber.