An arrangement for direct reduction of iron ore pellets to sponge iron pellets

Abstract

An arrangement for direct reduction of iron ore pellets to sponge iron pellets, comprising: a direct reduction shaft (1), said direct reduction shaft (1) being a vertical shaft (1) in which iron ore pellets move through the shaft (1) in a vertical direction by the action of the gravitational force, said direct reduction shaft (1) comprising, an iron ore inlet (2), a feeding tube (3) for feeding iron ore pellets into the shaft (1), said feeding tube (3) extending through the iron ore inlet (2) into the shaft (1), a reduction gas inlet (4), a top gas outlet (6), provided at an upper part of the shaft (1), for removal of spent reduction gas, and a sponge iron outlet (7), provided at a lower part of the shaft (1), below the level of the reduction gas inlet (4) In a wall of the feeding tube (3), between said iron ore inlet (2) and the lower end (5) of the feeding tube (3), there is provided a plurality of openings (8) in said wall.

Description

[0001] An arrangement for direct reduction of iron ore pellets to sponge iron pellets

[0002] TECHNICAL FIELD

[0003] The present invention relates to an arrangement for direct reduction of iron ore pellets to sponge iron pellets, comprising: a direct reduction shaft, said direct reduction shaft being a vertical shaft in which iron ore pellets move through the shaft in a vertical direction by the action of the gravitational force, said direct reduction shaft comprising, an iron ore inlet, a feeding tube for feeding iron ore pellets into the shaft, said feeding tube extending through the iron ore inlet in a vertical direction a predetermined distance into the shaft, a reduction gas inlet, arranged at a level below a lower end of the feeding tube, a top gas outlet, provided at an upper part of the shaft, for removal of spent reduction gas, and a sponge iron outlet, provided at a lower part of the shaft, below the level of the reduction gas inlet.

[0004] BACKGROUND

[0005] Arrangements for direct reduction of iron ore pellets to sponge iron pellets may preferably use a feeding tube through which the iron ore pellets are introduced into the direction reduction shaft. The feeding tube extends into the shaft from an inlet of the shaft down to a level which may preferably be the upper level of a direct reduction bed formed by the iron ore pellets inside the shaft. Upstream the feeding tube there may be provided a valve arrangement that prevents gas from escaping from the shaft through the iron ore pellets intake. Accordingly, during operation of there will be a standing column of reduction gas in the tube. In an upper part of the shaft, there is provided a top gas outlet, through which used reduction gas is removed from the shaft. During operation, used reduction gas (removed as top gas) will transfer heat to the iron ore pellets inside the feeding tube by heating the tube wall from the outside of the latter. Thereby, heat from the gas contributes to preheating and drying of the iron ore pellets before the pellets exit the tube. The residence time for preheating and drying of the iron ore pellets is limited in normal operation. The initial water content of the iron pellets may differ depending on the circumstances. Preheating and drying of the iron ore pellets to a dry condition is advantageous for the subsequent reduction process of the pellets.It is an object of the present invention to improve the efficiency of a direct reduction shaft, and to have a controlled and efficient heating and drying of iron ore pellets as the latter are introduced into the direction reduction shaft through the feeding tube.

[0006] SUMMARY

[0007] The object of the invention is achieved by means of an arrangement for direct reduction of iron ore pellets to sponge iron pellets, comprising:

[0008] - a direct reduction shaft, said direct reduction shaft being a vertical shaft in which iron ore pellets move through the shaft in a vertical direction by the action of the gravitational force, said direct reduction shaft comprising,

[0009] - an iron ore inlet,

[0010] - a feeding tube for feeding iron ore pellets into the shaft, said feeding tube extending through the iron ore inlet in a vertical direction a predetermined distance into the shaft,

[0011] - a reduction gas inlet, arranged at a level below a lower end of the feeding tube, - a top gas outlet, provided at an upper part of the shaft, for removal of spent reduction gas, and

[0012] - a sponge iron outlet, provided at a lower part of the shaft, below the level of the reduction gas inlet, said arrangement being characterised in that, in a wall of the feeding tube, between said iron ore inlet and the lower end of the feeding tube, there is provided a plurality of openings in said wall.

[0013] The openings will enable gas to flow through the feeding tube, thereby contributing to an improved heating and drying of iron ore pellets present therein.

[0014] According to some embodiments, the openings are evenly distributed around the peripheral circumference of the feeding tube.

[0015] According to some embodiments, the openings are elongated, having a longitudinal axis extending in a vertical direction. The openings may comprise thin slots or slits that enable gas to pass through but prevents iron ore pellets from escaping through said slots.According to some embodiments, at least one or more of said openings are located in an upper region of the part of the feeding tube that extends inside the direct reduction shaft. Thereby, heating and drying of pellets also in an upper part of the tube, by direct action of gas flowing through the tube, is achieved.

[0016] According to some embodiments, the arrangement comprises a reduction gas source connected to the reduction gas inlet, a heater for heating the reduction gas before entrance into the direct reduction shaft.

[0017] According to some embodiments, the reduction gas source comprises a hydrogen gas source.

[0018] According to some embodiments, the arrangement comprises an iron ore pellets intake, through which iron ore pellets are introduced into the feeding tube, wherein said iron ore intake comprises a valve arrangement that prevents gas from escaping from the direction shaft through the feeding tube and the iron ore intake.

[0019] BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In the following, embodiments will be disclosed with reference the annexed drawing, on which

[0021] Fig. 1 is a schematic figure of an arrangement according to the present invention.

[0022] DETAILED DESCRIPTION

[0023] Fig. 1 shows an arrangement for direct reduction of iron ore pellets to sponge iron pellets. The arrangement comprises a direct reduction shaft 1 , said direct reduction shaft 1 being a vertical shaft 1 in which iron ore pellets move through the shaft 1 in a vertical direction by the action of the gravitational force. The direct reduction shaft 1 comprises an iron ore inlet 2 and a feeding tube 3 for feeding iron ore pellets into the shaft 1. The feeding tube 3 extends through the iron ore inlet 2 in a vertical direction a predetermined distance into the shaft 1. As an alternative there may be provided a plurality of feeding tubes corresponding to the feeding tube 3 disclosed herein.The arrangement further comprises a reduction gas inlet 4, arranged at a level below a lower end 5 of the feeding tube 3, and a top gas outlet 6, provided at an upper part of the shaft 1 , for removal of spent reduction gas. A sponge iron outlet 7 is provided at a lower part of the shaft 1 , below the level of the reduction gas inlet 4.

[0024] In a wall of the feeding tube 3, between said iron ore inlet 2 and the lower end 5 of the feeding tube 3, there is provided a plurality of openings 8 in said wall.

[0025] The openings 8 are evenly distributed around the peripheral circumference of the feeding tube 3.

[0026] The openings 8 are elongated, having a longitudinal axis extending in a vertical direction, and at least one or more of said openings 8 are located in an upper region of the part of the feeding tube 3 that extends inside the direct reduction shaft 1.

[0027] The arrangement further comprises a reduction gas source 9. Preferably, the reduction gas provided by the gas source 9 is hydrogen gas, and, preferably, the gas source 9 comprises an electrolyser arrangement. A heater 10, preferably an electric heater, is provided downstream the reduction gas source 9 as seen in a flow direction of the reduction gas. A gas cleaning device 11 , for cleaning the top gas and separating water steam from remaining hydrogen gas, is connected to the top gas outlet 6 and to a gas line via which reduction gas is delivered from the gas reduction source 9 to the heater 10 and further to the reduction gas inlet 7 into the direct reduction shaft 1.

[0028] The arrangement further comprises an iron ore pellets intake 12 through which iron ore pellets are introduced into the feeding tube 3, wherein said iron ore intake 12 comprises a valve arrangement 13 that prevents gas from escaping from the direct reduction shaft 1 through the feeding tube 3 and the iron ore intake 12. A control unit 14 is configured to control the valve arrangement 13 of the iron ore intake 12, to control the iron ore pellet intake rate into the feeding tube 3.Finally, the arrangement further comprises a discharge device 15 arranged in connection to the sponge iron outlet 6. The control unit 14 is configured to control the flow rate of direct reduced iron through the sponge iron outlet 7 by controlling the discharge device 15.

Claims

CLAIMS1. An arrangement for direct reduction of iron ore pellets to sponge iron pellets, comprising:- a direct reduction shaft (1), said direct reduction shaft (1) being a vertical shaft (1) in which iron ore pellets move through the shaft (1) in a vertical direction by the action of the gravitational force, said direct reduction shaft (1) comprising,- an iron ore inlet (2),- a feeding tube (3) for feeding iron ore pellets into the shaft (1), said feeding tube (3) extending through the iron ore inlet (2) in a vertical direction a predetermined distance into the shaft (1),- a reduction gas inlet (4), arranged at a level below a lower end (5) of the feeding tube (3),- a top gas outlet (6), provided at an upper part of the shaft (1 ), for removal of spent reduction gas, and- a sponge iron outlet (7), provided at a lower part of the shaft (1 ), below the level of the reduction gas inlet (4), said arrangement being characterised in that, in a wall of the feeding tube (3), between said iron ore inlet (2) and the lower end (5) of the feeding tube (3), there is provided a plurality of openings (8) in said wall.

2. An arrangement according to claim 1, wherein the openings (8) are evenly distributed around the peripheral circumference of the feeding tube (3).

3. An arrangement according to claim 1 or 2, wherein the openings (8) are elongated, having a longitudinal axis extending in a vertical direction.

4. An arrangement according to any preceding claim, wherein at least one or more of said openings (8) are located in an upper region of the part of the feeding tube (3) that extends inside the direct reduction shaft (1).

5. An arrangement according to any preceding claim, comprising a reduction gas source (9) connected to the reduction gas inlet, and a heater (10) for heating the reduction gas before entrance into the direct reduction shaft (1).

6. An arrangement according to claim 5, wherein the reduction gas source (9) comprises a hydrogen gas source.

7. An arrangement according to any preceding claim, comprising an iron ore pellets intake (11), through which iron ore pellets are introduced into the feeding tube (3), wherein said iron ore intake (11) comprises a valve arrangement (12) that prevents gas from escaping from the direction shaft (1) through the feeding tube (3) and the iron ore intake (11).

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