METHOD FOR MANUFACTURING DIRECT REDUCED IRON AND DRI MANUFACTURING EQUIPMENT

Abstract

A method for manufacturing Direct Reduced Iron wherein iron ore is reduced in a DRI shaft by a reducing gas including hydrogen obtained by extraction from coke oven gas through a hydrogen separation unit, the remaining part of such coke oven gas being at least partly injected in the transition section of said DRI shaft to set the carbon amount of said Direct Reduced Iron from 0.5 to 3 wt. % and a DRI manufacturing equipment including a DRI shaft (1) and a hydrogen separation unit (5), wherein said hydrogen separation unit (5) inlet is connected to a coke oven gas supply (6) and includes a first outlet connected to the DRI shaft to inject hydrogen separated from said coke oven gas and a second outlet connected to the transition section of said DRI shaft (1) to inject at least part of the remaining part of such coke oven gas.

Claims

1-14. (canceled)

15: A method for manufacturing Direct Reduced Iron, the method comprising: reducing iron ore is reduced in a DRI shaft by a reducing gas including hydrogen obtained by extraction from coke oven gas through a hydrogen separation unit; and at least partly injecting a remaining part of the coke oven gas in a transition section of the DRI shaft to set the carbon amount of the Direct Reduced Iron in a range from 0.5 to 3 wt. %.

16: The method as recited in claim 15 wherein the reducing gas further includes top gas exiting the DRI shaft, the top gas being mixed with the hydrogen obtained by extraction from coke oven gas.

17: The method as recited in claim 15 wherein the reducing gas further includes additional reducing gas selected from the group consisting of hydrogen and biogas, the additional reducing gas being mixed with the hydrogen obtained by extraction from coke oven gas.

18: The method as recited in claim 15 wherein the reducing gas further includes either (1) top gas exiting the DRI shaft, the top gas being mixed with the hydrogen obtained by extraction from coke oven gas or (2) additional reducing gas selected from the group consisting of hydrogen and biogas, the additional reducing gas being mixed with the hydrogen obtained by extraction from coke oven gas, wherein the reducing gas is heated after being mixed.

19: The method as recited in claim 18 wherein the heating of the reducing gas is performed by using CO.sub.2 neutral electricity.

20: The method as recited in claim 15 wherein the reducing gas is injected in the DRI shaft in a reduction section.

21: The method as recited in claim 15 wherein the top gas coming from the DRI shaft is scrubbed to remove water before being mixed into the reducing gas.

22: The method as recited in claim 15 wherein a remaining part of such coke oven gas is partly injected in a cooling section of the DRI shaft.

23: The method as recited in claim 15 wherein the carbon content of the Direct Reduced Iron is set from 1 to 2 wt. %.

24: DRI manufacturing equipment comprising: a DRI shaft; and a hydrogen separation unit having an inlet connected to a coke oven gas supply and including a first outlet connected to the DRI shaft to inject hydrogen separated from coke oven gas from the coke oven gas supply and a second outlet connected to a transition section of said DRI shaft to inject at least part of a remaining part of the coke oven gas.

25: The DRI equipment as recited in claim 24 further comprising a mixer including a first inlet connected to the first outlet of the hydrogen separation unit and a second inlet connected to a top gas outlet of the DRI shaft.

26: The DRI equipment as recited in claim 25 wherein the mixer includes a third inlet connected to an additional reducing gas supply.

27: The DRI equipment as recited in claim 25 wherein the mixer is connected to a reduction section of the DRI shaft.

28: The DRI equipment as recited in claim 24 further comprising a scrubber connected to a top gas outlet of the DRI shaft.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Other characteristics and advantages of the invention will emerge clearly from the description of it that is given below by way of an indication and which is in no way restrictive, with reference to the appended FIGURES in which:

[0029] FIG. 1 illustrates a DRI manufacturing equipment according to the invention.

DETAILED DESCRIPTION

[0030] Elements in the FIGURE are illustration and may not have been drawn to scale.

[0031] FIG. 1 is a schematic view of a DRI manufacturing equipment according to the invention. The DRI manufacturing equipment includes a DRI shaft 1 comprising from top to bottom an inlet for iron ore 10 that travels through the shaft by gravity, a reduction section located in the upper part of the shaft, a transition section located in the midpart of the shaft, a cooling section located at the bottom and an outlet 12 from which the direct reduced iron is finally extracted.

[0032] On top of the shaft, the top gas exiting the DRI shaft is collected in a pipe 20 which can optionally be connected to a scrubber 2 located on the top gas outlet of the DRI shaft. The top gas exiting from the DRI shaft usually comprises H.sub.2, CO, CH.sub.4, H.sub.2O, CO.sub.2 and N.sub.2 in various proportions. The top gas scrubbing operation allows removing water vapor from the rest of the stream to improve its reduction potential.

[0033] In a preferred embodiment, after scrubbing, the top gas comprises from 40 to 75 vol % of H.sub.2, from 0 to 30 vol % of carbon monoxide CO, from 0 to 10 vol % of methane CH.sub.4, from 0 to 25 vol % of carbon dioxide CO.sub.2, up to 5 vol % of H.sub.2O, the remainder being nitrogen N.sub.2. It is preferred to have, after scrubbing, a ratio of H.sub.2/N.sub.2 from 1.5 to 3 in such top gas.

[0034] Once the top gas exits the scrubber 2, it can optionally be compressed and can either be sent back to the DRI shaft or sent to one of the inlets of a mixer 4 through a connecting pipe 21.

[0035] Another inlet of said mixer 4 can be connected to a reduction gas supply 3. Such reduction gas can consist in hydrogen or in a hydrocarbon gas, like methane for example. In a preferred embodiment, the hydrogen supply is fed with green hydrogen produced without CO.sub.2 emission, for example by water or steam electrolysis that can be powered with CO.sub.2 neutral electricity.

[0036] CO.sub.2 neutral electricity includes notably electricity from renewable source but can encompass the use of electricity coming from nuclear sources as it is not emitting CO.sub.2 to be produced. CO.sub.2 from renewable source is defined as energy that is collected from renewable resources, which are naturally replenished on a human timescale, including sources like sunlight, wind, rain, tides, waves, and geothermal heat.

[0037] In another embodiment, the reductant gas supply consists in a biogas, which is a renewable energy source that can be obtained by the breakdown of organic matter in the absence of oxygen inside a closed system called bioreactor. Biogas can be produced from raw materials such as agricultural waste, manure, municipal waste, plant material, sewage, green waste, food waste or any biodegradable materials. A preferred bio gas is for example biomethane.

[0038] A third inlet of the mixer 4 is connected to the outlet of a separation unit 5. Such separation unit 5 is connected to a Coke Oven gas supply 6. Coke oven gas composition is usually comprising 3 to 6 vol % of CO, 1 to 5 vol % of CO.sub.2, 36 to 62 vol % of H.sub.2, 16 to 27 vol % of CH.sub.4, the remainder being nitrogen. Coke oven is produced as a by-product of the coke production and is usually used to fire the coke oven battery or simply burned. In most cases, its further use results in CO.sub.2 emissions in the atmosphere.

[0039] The separation unit 5 allows extracting hydrogen from such stream and sending such hydrogen to the mixer 4 through a connecting pipe 50.

[0040] The separation unit can be based on any suitable industrial process of separation of gases, like physical and chemical absorption processes, adsorption processes or membrane processes.

[0041] In a preferred embodiment, the separation unit is a Pressure Swing Adsorption (PSA).

[0042] In another embodiment, the separation unit is a membrane, preferably a ceramic microporous membrane.

[0043] The reduction gas produced in the mixer 4 through the addition of the top gas, additional reductant gas and hydrogen from Coke Oven Gas, can optionally be heated through heating means provided to the mixer, such heating means being for example preferably powered by CO.sub.2 neutral electricity or by burning a part of the coke oven gas. In a preferred embodiment, the temperature of the reduction gas is set to a range from 700? ? C. to 1000? C., preferably from 800 to 1000? C.

[0044] This reduction gas is then sent back to the DRI shaft, preferably in its reduction section through a pipe 11.

[0045] Coming back to the separation unit 5, the remaining part of the gas obtained after extraction of the hydrogen, is being sent back to the transition section of the DRI shaft 1 through a connecting pipe 51.

[0046] The injection of this gas is made to increase the carbon content of the Direct Reduced Iron to a range from 0.5 to 3 wt. %, preferably from 1 to 2 wt. % which allows getting a Direct Reduced Iron that can be easily handled and that keeps a good combustion potential for its future use.

[0047] The DRI manufacturing equipment may further comprise a recycling loop in the cooling section that allows extracting part of the gas present at that level to send it in a scrubber 30 and in a compression unit 31 before reinjecting it in the shaft 1.

[0048] In a preferred embodiment, part of the gas transported in the connection pipe 51 can be injected in such recycling loop of the cooling section after the compression unit to allow increasing the carbon content of the Direct Reduced Iron in the cooling section as well.

[0049] It is also possible to inject part of the gas transported in the connection pipe 51 in the reduction section of the DRI shaft, as such gas has a reduction power thanks to its content in CO and remaining H.sub.2.

[0050] By using the method according to the invention, Direct Reduced Iron can be manufactured with the appropriate quality and yield, while remaining CO.sub.2 neutral and taking optimal advantage of the gas co-product from coke manufacturing. It also allows decreasing the use of fossil energy like natural gas.