PROCESS AND APPARATUS FOR DIRECT REDUCTION WITH ELECTRICALLY HEATED-UP REDUCTION GAS

Abstract

Process for the direct reduction of metal oxides (2) using a reduction gas, which is based on at least one precursor gas, wherein at least one precursor gas (15, 22) is based on reformer gas obtained by catalytic reforming of hydrocarbon-containing gas (4) in a reformer (3), and in the preparation of the reduction gas at least one precursor gas based on reformer gas is heated up by means of electrical energy. An apparatus for the direct reduction (1) of metal oxides (2) by means of a reduction gas comprises a catalytic reformer (3) for producing a reformer gas, a reformer gas line (5) for removing reformer gas from the catalytic reformer (3), a reduction unit (9), a reduction gas line (8) for introducing reduction gas into the reduction unit (9), and at least one precursor gas line (6), wherein at least one precursor gas line extending from the reformer gas line comprises an electrical gas heating device (7, 10, 17), and at least one precursor gas line (6) extends from the reformer gas line (5), and each precursor gas line (6) opens out into the reduction gas line (8).

Claims

1. A method of direct reduction of metal oxides using a reduction gas based on at least one precursor gas, wherein the at least one precursor gas is based on reformer gas obtained by catalytic reforming of hydrocarbonaceous gas in a reformer, preparation of the reduction gas involves heating the at least one precursor gas based on reformer gas, and optionally additionally also heating one or more further precursor gases, by means of electrical energy, wherein the one or more further precursor gases optionally comprises the at least one precursor gas or another precursor gas, wherein at least a portion of the electrical energy is introduced by means of plasma.

2. The method as claimed in claim 1, wherein the at least one precursor gas based on the reformer gas is heated by the electrical energy to a temperature within a range of up to 200° C. above an exit temperature from the reformer.

3. The method as claimed in claim 2, wherein the at least one precursor gas envisaged for electrical heating, prior to the heating by means of the electrical energy, is already heated in another way to at least 700° C.

4. The method as claimed in claim 3, wherein the at least one precursor gas, which is envisaged for the electrical heating, by means of the electrical energy to more than 800° C.

5. The method as claimed in claim 1, wherein on introduction of the reduction gas into a reduction unit containing the metal oxides to be reduced, the temperature of the reduction gas is in the range of 800° C. to 1100° C.

6. The method as claimed in claim 1, further comprising adding hydrocarbonaceous additional gas to the further precursor gas which is heated by means of electrical energy.

7. The method as claimed in claim 6, further comprising reforming at least a portion of the hydrocarbonaceous additional gas in situ before the reduction gas is introduced into a reduction unit containing the metal oxides.

8. (canceled)

9. The method as claimed in claim 1, further comprising directly reducing metal oxides using at least one additional reduction gas.

10. An apparatus for directly reducing metal oxides by means of a reduction gas, the apparatus comprising: a catalytic reformer for producing a reformer gas, a reformer gas conduit for discharging of the reformer gas from the catalytic reformer, a reduction unit, a reduction gas conduit for introducing reduction gas into the reduction unit, at least one precursor gas conduit, comprising an electrical gas heating apparatus, and wherein the at least one precursor gas conduit proceeding from the reformer gas conduit comprises an electrical gas heating apparatus, and wherein each precursor gas conduit opens into the reduction gas conduit, and wherein the electrical gas heating apparatus comprises at least two plasma burners.

11. The apparatus as claimed in claim 10, wherein the apparatus for direct reduction of metal oxides comprises at least one additional reduction gas conduit for introduction of additional reduction gas into the reduction unit.

12. The apparatus as claimed in claim 10, further comprising the electrical gas heating apparatus comprises at least one heating chamber having at least one of the plasma burner, at least one exit opening for exit of heated gas, and at least one entry opening for entry of precursor gas, and having at least one longitudinal heating chamber wall extending longitudinally when viewed from the entry opening toward the exit opening, wherein the plasma burner is disposed in a middle of the heating chamber, and wherein the entry opening is disposed between the plasma burner and a longitudinal heating chamber wall.

13. The apparatus as claimed in claim 10, further comprising the electrical gas heating apparatus comprises at least one heating chamber having at least one of the plasma burners, at least one exit opening for exit of heated gas, and at least one entry opening for entry of precursor gas, and at least one longitudinal heating chamber wall extending longitudinally when viewed from the entry opening toward the exit opening, wherein the entry opening is disposed and the heating chamber is shaped such that an introduced stream of the precursor gas flows from the entry opening to the exit opening in spiral form around the plasma burner between the plasma burner and the longitudinal heating chamber wall.

14. The apparatus as claimed in claim 13, wherein the entry opening is in an unsymmetric arrangement relative to the longitudinal axis of the heating chamber, and the entry opening is capable of guiding precursor gas into the heating chamber tangentially to the longitudinal heating chamber wall.

15. The apparatus as claimed in claim 13, wherein the hydraulic diameter of the entry opening is in the range from 25% to 75% of the hydraulic heating chamber diameter.

16. The apparatus as claimed in claim 13, wherein the heating chamber comprises a cylindrical entry section with the entry opening and a conical exit section with the exit opening, and the hydraulic diameter of the entry opening is in the range from 25% to 75% of the diameter of the entry section.

17. The apparatus as claimed in claim 13, wherein the heating chamber comprises a cylindrical entry section with the entry opening and a conical exit section with the exit opening, wherein the ratio of a height of the entry section to the diameter of the entry section is in the range from 1 to 10.

18. The apparatus as claimed in claim 13, wherein the heating chamber comprises a cylindrical entry section with the entry opening and a conical exit section with the exit opening, wherein the angle of the lateral heating chamber wall of the exit section to the longitudinal axis is in the range of 5°-45°.

19. The apparatus as claimed in claim 10, wherein the gas heating apparatus comprises at least one heating chamber in which there are multiple plasma burners.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0108] The invention is elucidated by schematic, illustrative drawings of embodiments.

[0109] FIG. 1 shows a schematic of an embodiment of a method of the invention and of an apparatus of the invention for direct reduction of metal oxides by means of a reduction gas.

[0110] FIGS. 2a and 2b show schematics of longitudinal sections and cross sections through one embodiment of part of an electrical gas heating apparatus.

[0111] FIG. 3 shows a schematic of a section through an embodiment of part of an electrical gas heating apparatus.

[0112] FIGS. 4a to 4i show schematics of variants of the arrangement of plasma burners in a heating chamber of a gas heating apparatus.

[0113] FIGS. 5a and 5b show schematics of longitudinal sections and cross sections through a heating chamber in one embodiment.

[0114] FIGS. 6a and 6b show schematics of longitudinal sections and cross sections through a heating chamber in another embodiment.

[0115] FIGS. 7 and 8 show further embodiments largely analogous to FIG. 1.

DESCRIPTION OF THE EMBODIMENTS

Examples

[0116] FIG. 1 shows a schematic of an embodiment of an inventive apparatus for direct reduction 1 of metal oxides 2 by means of a reduction gas.

[0117] In a catalytic reformer 3, reformer gas is produced by catalytic reforming of hydrocarbonaceous gas 4.

[0118] The reformer gas is discharged from the catalytic reformer 3 via the reformer gas conduit 5.

[0119] A precursor gas conduit 6 proceeds from the reformer gas conduit 5. The precursor gas conduit 6 comprises an electrical gas heating apparatus 7.

[0120] The precursor gas is based on the reformer gas and is heated up by means of electrical energy in the electrical gas heating apparatus 7. The precursor gas conduit 6—beyond the electrical gas heating apparatus 7 when viewed in flow direction away from the reformer—opens into a reduction gas conduit 8. The latter itself opens into a reduction unit 9; it introduces reduction gas into the reduction unit 9.

[0121] The metal oxides are within the reduction unit 9; in the case shown, the reduction unit 9 is a reduction shaft in which there is a solid material bed comprising the metal oxides. In the reduction unit 9, the metal oxides 2 are directly reduced by means of the reduction gas flowing through the material bed.

[0122] The reformer gas conduit 5 may optionally also additionally have an opening into the reduction gas conduit 8; this is represented by a branch from reformer gas conduit 5 which is shown by a dashed line. In this way, it is possible for some reformer gas to bypass the gas heating apparatus 7 and be added as additional gas to the heated precursor gas.

[0123] It would be possible in principle, in FIG. 1, for the purpose of preparation of the reduction gas, for there also to be further precursor gas conduits for supply of further precursor gases; this is not shown additionally for better clarity.

[0124] FIGS. 2a and 2b show longitudinal sections and cross sections through one embodiment of part of an electrical gas heating apparatus 10 having a heating chamber 11 with a plasma burner 12. The plasma burner 12 is arranged in the middle of the heating chamber 11. This can clearly be seen in cross section in FIG. 2b along the line A-A from FIG. 2a. The heating chamber 11, which is a round cylinder in the example shown, is bounded by the longitudinal heating chamber wall 13. Precursor gas—shown as an arrow—is introduced into the heating chamber 11 through the entry openings 14a, 14b, 14c, 14d. Heated gas—represented by a block arrow—is discharged from the heating chamber 11 through an exit opening which is not shown additionally—represented by an arrow. The precursor gas is introduced into the heating chamber 11 between the longitudinal heating chamber wall 13 and the plasma burner 12. The stream of the precursor gas 15 from the entry opening 14a shown is thus between the plasma 16 and longitudinal heating chamber wall 13. It would also be possible for multiple heating chambers of this kind with one plasma burner each to be present in the electrical gas heating apparatus.

[0125] FIG. 3 shows a section through an embodiment of part of an electrical gas heating apparatus 17 having a heating chamber 18 with the plasma burner 19. The heating chamber 18 is essentially in cylindrical form, with the plasma burner 19 essentially along the cylinder axis 20. An entry apparatus 21 with entry opening introduces precursor gas 22 tangentially into the heating chamber 18, and after entry it flows around the plasma burner 19 to the exit opening 23. The cylinder axis 20 runs through the exit opening 23 for discharge of the heated gas. It would also be possible to provide multiple heating chambers of this kind with one plasma burner each in the electrical gas heating apparatus.

[0126] FIGS. 4 a-i show variants of the arrangement of plasma burners in a heating chamber of a gas heating apparatus in which there are multiple plasma burners. In particular, possible forms of arrangement are annular, semicircular or part-circular, radially around the longitudinal axis of the heating chamber, which is shown in FIGS. 4a, 4b, 4c. FIG. 4a shows, in oblique view in a section through a cylindrical heating chamber 24 at right angles to the longitudinal axis—corresponding to the flow direction of the gas to be heated, indicated by arrows—how multiple openings 25 are present in a ring for mounting of plasma burners. The plasma burners may stand with their longitudinal axis, for example, at right angles or oblique relative to the longitudinal axis of the heating chamber 24. FIG. 4b shows, in a section through a cylindrical heating chamber 26 at right angles to the longitudinal axis—corresponding to the flow direction of the gas to be heated—how multiple openings 27 are present in a semicircle for mounting of plasma burners. FIG. 4c shows, in a section through a cylindrical heating chamber 28 at right angles to the longitudinal axis—corresponding to the flow direction of the gas to be heated—how multiple openings 29 are present in a semicircle for mounting of plasma burners. FIG. 4d shows, in a longitudinal section through a section of a heating chamber as in FIG. 4a, how multiple rings of plasma burners can be installed; what are shown are the openings 25 for assembly, the longitudinal axis 30 of the heating chamber and the gas flow direction 31. FIG. 4e shows this in a corresponding view for an arrangement in which there is in each case only one plasma burner per position along the longitudinal axis.

[0127] FIG. 4f shows, in a corresponding view, an example of how the plasma burners can be oriented with respect to the longitudinal axis. The arrows indicate that the plasma burners are inclined toward the longitudinal axis. FIGS. 4g and 4h show, in a view largely analogous to FIG. 4a, that the plasma burners indicated by arrows may be directed to the center of the gas flow—shown in FIG. 4g—or virtually tangentially to the gas flow—shown in FIG. 4h. The direction vector of the incoming plasma burner flow—corresponding to the arrow directions in FIGS. 4g and 4h—may thus be at least partially axial and/or at least partially tangential to the flow of the gas from the gas inlet opening to the gas outlet opening.

[0128] FIG. 4i shows, in schematic form, by a section at right angles to the longitudinal axis of a variant of a heating chamber 32, how the gas stream 33 to be heated is introduced between plasma burner 34 and wall of the heating chamber 32.

[0129] FIG. 5a shows a longitudinal section through a heating chamber 35 comprising a cylindrical entry section 36 with entry opening 37 and a conical exit section 38 with exit opening 39. The hydraulic diameter of the entry opening 37 is 45% of the diameter of the entry section.

[0130] The ratio of diameter of the entry opening 37 to the radius of the entry section 36 is 90%.

[0131] The angle α of the lateral heating chamber wall of the exit section to the longitudinal axis 40 is 35°.

[0132] The plasma burner 41 is disposed in the middle of the lid section 42; a carrier gas conduit 43 for supply of carrier gas is also shown.

[0133] The entry opening is in a nonsymmetric—i.e. unsymmetric—arrangement relative to the longitudinal axis of the heating chamber. In the case of such an eccentric arrangement, the stream of the precursor gas introduced can flow in a spiral along the longitudinal heating chamber wall—in the entry section and in the exit section; the stream is not introduced aimed radially at the longitudinal axis, but is introduced tangentially to the longitudinal heating chamber wall.

[0134] For illustration of a selection of other options for the shape of the entry opening or positioning thereof with respect to the longitudinal axis 40, outlines of a round entry opening are shown by a dotted line, and of a rectangular entry opening by a dashed line.

[0135] FIG. 5b shows a view of the apparatus shown in FIG. 5a from the top. Analogously to FIG. 5a, outlines of variants of the entry opening are also shown by a dotted and a dashed line.

[0136] FIGS. 6a and 6b show, in views largely analogous to FIGS. 5a and 5b, an embodiment in which the entry opening 45 is offset to the side by comparison with FIG. 5a in the entry section 44. Introduction of the gas stream to be heated into the cylindrical entry section 44 is in spiral form.

[0137] FIG. 6b shows in schematic form, by a section F-F′, viewed from above, how the entry is drawn in the form of a spiral around the cylindrical entry section 44. The dashed line shows the outline of the edge C in the region of the opening of the entry opening into the cylindrical entry section.

[0138] The spiral portion could also extend less far or further; the shape of the entire entry section could also follow the spiral defined by the inlet 46.

[0139] FIG. 7 shows, analogously to FIG. 1, how, in the electrical gas heating apparatus 47, a plasma burner 48, the plasma of which is produced with electrical energy utilizing carrier gas from the carrier gas conduit 49, heats the precursor gas reformer gas in the precursor gas conduit 50 in the gas heating apparatus 47. The electrical energy is introduced into the precursor gas by means of plasma.

[0140] FIG. 8 shows, largely analogously to FIG. 1, an embodiment of an apparatus of the invention in which there is an additional reduction gas conduit 51 for introduction of additional reduction gas into the reduction unit 52. What is also shown by dashed lines is the optional addition of natural gas 53 into the precursor gas conduit 54 upstream of the electrical gas heating apparatus 55. What is heated is a precursor gas which is a mixture of natural gas 53 and reformer gas; this precursor gas is based on reformer gas.

[0141] Although the invention has been illustrated and described in detail by the preferred working examples, the invention is not limited by the examples disclosed, and other variations can be derived therefrom by the person skilled in the art without leaving the scope of protection of the invention.

LIST OF REFERENCE NUMERALS

[0142] 1 Apparatus for direct reduction [0143] 2 Metal oxides [0144] 3 Reformer [0145] 4 Hydrocarbonaceous gas [0146] 5 Reformer gas conduit [0147] 6,6′,6″,6′″ Precursor gas conduit [0148] 7 Gas heating apparatus [0149] 8 Reduction gas conduit [0150] 9 Reduction unit [0151] 10 Gas heating apparatus [0152] 11 Heating chamber [0153] 12 Plasma burner [0154] 13 Longitudinal heating chamber wall [0155] 14a,14b,14c,14d Entry openings [0156] 15 Precursor gas [0157] 16 Plasma [0158] 17 Gas heating apparatus [0159] 18 Heating chamber [0160] 19 Plasma burner [0161] 20 Cylinder axis [0162] 21 Entry apparatus [0163] 22 Precursor gas [0164] 23 Exit opening [0165] 24 Heating chamber [0166] 25 Openings for mounting of plasma burners [0167] 26 Heating chamber [0168] 27 Openings for mounting of plasma burners [0169] 28 Heating chamber [0170] 29 Openings for mounting of plasma burners [0171] 30 Longitudinal axis [0172] 31 Gas flow direction [0173] 32 Heating chamber [0174] 33 Gas stream to be heated [0175] 34 Plasma burner [0176] 35 Heating chamber [0177] 36 Entry section [0178] 37 Entry opening [0179] 38 Exit section [0180] 39 Exit opening [0181] 40 Longitudinal axis [0182] 41 Plasma burner [0183] 42 Lid section [0184] 43 Carrier gas conduit [0185] 44 Entry section [0186] 45 Entry opening [0187] 46 Inlet [0188] 47 Gas heating apparatus [0189] 48 Plasma burner [0190] 49 Carrier gas conduit [0191] 50 Precursor gas conduit [0192] 51 Additional reduction gas conduit [0193] 52 Reduction unit [0194] 53 Natural gas [0195] 54 Precursor gas conduit [0196] 55 Gas heating apparatus