Biomass direct reduced iron

Patent metadata

Field	Value
Publication number	US-2023407423-A1
Application number	US-202118038139-A
Country	US
Kind code	A1
Filing date	Nov 24, 2021
Priority date	Nov 24, 2020
Publication date	Dec 21, 2023
Grant date	—

Abstract

A method and an apparatus for “recycling” a significant amount of heat within a linear hearth furnace by means of an endless conveyor that transports briquettes through the furnace from an inlet (briquette feed) end to an outlet (DRI discharge) end and then returns to the inlet end and transfers a significant amount of heat from the outlet end to the inlet end of the furnace.

First claim

1 . A method for producing direct reduced iron (DRI) from briquettes of a composite of iron ore fragments and biomass in a linear hearth furnace including a refractory-lined chamber having the following zones along the length of the furnace between an inlet for briquettes of iron ore fragments and biomass and an outlet for direct reduced iron: a feed zone that includes the inlet, a preheat zone, a final reduction zone and a discharge zone that includes the outlet, and an endless conveyor that moves through the zones from the inlet to the outlet and then returns to the inlet, with the conveyor having a base for receiving and supporting briquettes, the method including:
a) feeding briquettes onto the base of the conveyor in the feed zone; b) transporting briquettes on the conveyor through the preheat zone and heating briquettes and reducing iron ore in briquettes and releasing volatiles in biomass in briquettes, with heating including generating heat by burning combustible gases in a top space of the preheat zone via a plurality of air or oxygen-enriched air fed burners, with the combustible gases including combustible gases generated within the furnace; c) transporting heated briquettes on the conveyor from the preheat zone through the final reduction zone, with the final reduction zone being an anoxic environment, and supplying electromagnetic energy, such as microwave energy, into the final reduction zone and heating briquettes and reducing iron ore in briquettes and forming DRI; d) transporting DRI on the conveyor to the discharge zone at the outlet and discharging DRI from the discharge zone; and e) returning the unloaded conveyor from the outlet to the inlet of the furnace and repeating step (a) of feeding briquettes onto the base of the conveyor, with the base of the conveyor having a hot face temperature of at least 500° C. when it returns to the feed zone and before it is loaded with briquettes and thereby returning heat to the furnace and contributing to heating briquettes.

2 . The method defined claim 1 wherein step (a) includes forming a relatively uniform bed of briquettes on the conveyor.

3 . The method defined in claim 1 wherein the hot face temperature of the base of the conveyor in the feed zone before it is loaded with briquettes in the feed zone is at least 800° C. so as to recover heat therefrom.

4 . The method defined in claim 3 wherein the hot face temperature of the unloaded base of the conveyor in the feed zone before it is loaded with briquettes in the feed zone is at least 900° C. so as to recover heat therefrom.

5 . The method defined in claim 1 includes returning the conveyor to the inlet through a thermally-insulated chamber in a lower region of the furnace to maintain heat or minimise heat loss in the base of the conveyor between the outlet and the inlet of the furnace.

6 . The method defined in claim 4 includes heating the lower region of the furnace and therefore the base of the conveyor using hot gases from the furnace.

7 . The method according to claim 6 includes heating the base of the conveyor by transferring at least a part of hot gases produced by combusting combustible gases in the preheat zone to the lower region of the furnace and/or by transferring at least a part of hot gases produced in the final reduction zone to the lower region of the furnace and/or by electrical heating.

8 . (canceled)

9 . (canceled)

10 . The method defined in claim 1 wherein the mass percentage of biomass in briquettes is 20-45%, typically 30-45%, by weight on a wet (as-charged) basis.

11 . The method defined in claim 10 wherein the biomass includes a significant lignocellulosic component.

12 . The method defined in claim 9 wherein the balance of the composition of briquettes is (a) iron ore fragments (b) optionally flux/binder materials and (c) optionally additional carbonaceous material, such as coal or pre-charred biomass, in an amount of <5% by weight of the total weight of individual briquettes.

13 . The method defined in claim 1 includes controlling the method so that the bulk temperature of briquettes is at least 500° C. when briquettes leave the preheat zone and pass to the final reduction zone.

14 . The method defined in claim 1 wherein step (c) includes electromagnetic energy heating briquettes by at least 250° C. in the final reduction zone.

15 . The method defined in claim 1 includes releasing at least 90% of volatiles in biomass in the briquettes as a gas in the preheat zone.

16 . The method defined in claim 1 wherein step (c) includes generating a higher pressure of gases in the final reduction zone compared to gas pressure in the preheat zone and thereby causing gases generated in the final reduction zone to flow counter-current to the direction of movement of briquettes on the conveyor through the furnace.

17 . The method defined in claim 1 includes generating heat in step (b) by burning combustible gases in a plurality of burners that are spaced apart along the length of the top space of the preheat zone of the furnace and/or spaced across the width of the preheat zone of the furnace.

18 . The method defined in claim 17 includes generating heat in step (b) by burning combustible gases in a plurality of burners that are spaced across the width of the preheat zone of the furnace.

19 . The method defined in claim 17 includes adjusting the amount of air or oxygen-enriched air fed to each burner in step (b) to compensate for variations in combustible gas in the top space of the preheat zone.

20 . (canceled)

21 . An apparatus for producing direct reduced iron (DRI) from briquettes of a composite of iron ore fragments and biomass, the apparatus including a linear hearth furnace that includes a refractory-lined chamber having:
(a) an inlet for briquettes of 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 for briquettes;
(ii) a preheat zone for heating briquettes and reducing iron ore in briquettes and releasing volatiles in biomass in briquettes, 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 final reduction zone for heating briquettes and reducing iron ore in briquettes and forming DRI, the final reduction zone including a means for supplying electromagnetic energy, such as microwave energy, into the final reduction zone for heating briquettes; and
(iv) a discharge zone that includes the outlet, the discharge zone being configured for discharging DRI from the furnace; and
(c) an endless conveyor having a base for receiving and transporting briquettes through the zones from the inlet to the outlet and then returning to the inlet, the apparatus being configured to return the conveyor from the outlet to the inlet of the furnace with the base having a hot face temperature of at least 500° C. when it returns to the feed zone and before it is loaded with briquettes thereby recovering heat from the furnace and then returning heat to the furnace and contributing to heating briquettes.

22 . The apparatus defined in claim 21 wherein the conveyor includes a return leg that extends through a thermally-insulated chamber in a lower region of the furnace configured to maintain heat or minimise heat loss in the ba

Assignees

• Tech Resources Pty Ltd

Inventors

• Buckley Michael

Classifications

• Y02P10/134

  by avoiding CO2, e.g. using hydrogen · CPC title

• F27D11/12

  with electromagnetic fields acting directly on the material being heated · CPC title

• F27D2099/0026

  with a generator of electromagnetic radiations · CPC title

• F27D99/0033

  using burners · CPC title

• F27B9/30

  Details, accessories or equipment specially adapted for furnaces of these types · CPC title