Biomass direct reduced iron

A method for producing direct reduced iron (DRI) from iron ore using biomass (as a source of reductant) and microwave energy (as a heating source) in a hearth furnace, the method including counter-current movement of (a) a material, the material including iron ore and biomass, the material at least initially being in the form of briquettes of iron ore and biomass, successively through a preheat zone and a reduction zone in a direction from an inlet (the inlet end) to an outlet (the outlet end) and discharging DRI from the outlet and (b) a flow of combustible gases produced by heating material and reduction of iron ore in the material in the reduction zone to the preheat zone (at the inlet end), combusting combustible gases arising from such heating of biomass and reduction of iron ore by air or oxygen-enriched air fed burners in the preheat zone, maintaining an anoxic atmosphere in the reduction zone, supplying microwave energy to facilitate reduction of iron-containing material in the anoxic atmosphere, with the microwave energy being delivered via a plurality of microwave applicators in the form of horns into a lower sub zone of the reduction zone directly onto the material below the horns, with the horns having perforations that enable reduction gases arising from such reduction to pass therethrough while is at least substantially preventing microwave energy from passing therethrough, thereby allowing the reduction gases to be sufficiently unrestricted by the horns so that reduction gases can flow into an upper sub zone of the reduction zone so that reduction gas flowing from the reduction zone to the preheat zone does not exceed a threshold bulk gas velocity.

An apparatus for producing direct reduced iron (DRI) from iron ore fragments and biomass, the apparatus including a furnace that includes a chamber having:

• (a) an inlet for a material including iron ore and biomass at one end and an outlet for direct reduced iron at the other end,
• (b) the following zones:
• (i) a feed zone that includes the inlet,
• (ii) a preheat zone for heating the material and reducing iron ore in the material and releasing volatiles in biomass in the material, the preheat zone including a plurality of air or oxygen-enriched air fed burners for generating heat by burning combustible gases in a top space of the preheat zone, with the combustible gases including combustible gases originating within the furnace,
• (iii) a reduction zone for heating material and reducing iron ore in the material and forming DRI, the reduction zone including an upper sub zone and a lower sub zone and an interface separating the subzones that is configured to so that (a) microwave energy is at least substantially prevented from passing through the interface to the upper sub zone and (b) reduction gases produced in the lower sub zone from reduction of iron ore can flow through the interface into the upper sub zone, a plurality of applicators arranged in rows across a width of and along a section of a length of the reduction zone for supplying microwave energy into the lower sub zone for heating the material in the lower sub zone, the applicators having outlet openings for microwave energy, at least substantially all of the applicators in each row being configured so that microwave energy forms a regular field pattern;
• and
• (iv) a discharge zone that includes the outlet;
• and
• (c) a conveyor for receiving and transporting the material through the zones from the inlet to the outlet.