Sealing valve arrangement for a shaft furnace charging installation

Abstract

A sealing valve arrangement for a shaft furnace charging installation including a shutter that cooperates with a valve seat and a shutter-actuating device for moving the shutter between a closed position in sealing contact with the valve seat and an open position remote from the valve seat, where the shutter-actuating device includes a tilting shaft connected to the shutter, an electric motor with an output shaft connected to the tilting shaft, and a braking device associated with the electric motor, where the braking device is configured for, when engaged, preventing the output shaft of the electric motor from rotating, the shutter-actuating device further including a transmission means arranged between the output shaft of the electric motor and the tilting shaft, wherein the transmission means is configured for transmitting rotational movement of the output shaft of the electric motor to the tilting shaft, where the transmission means includes a backlash configured for having a predetermined amount of allowed rotation between the output shaft of the electric motor and the tilting shaft.

Claims

1. A sealing valve arrangement for a shaft furnace charging installation, said sealing valve arrangement comprising: a shutter that cooperates with a valve seat; a shutter-actuating device for moving said shutter between a closed position in sealing contact with the valve seat and an open position remote from said valve seat; wherein said shutter-actuating device comprises: a tilting shaft connected to said shutter; an electric motor with an output shaft connected to said tilting shaft, said electric motor disposed between a braking device and said tilting shaft; said braking device associated with said electric motor, said braking device being configured for stopping said output shaft of said electric motor from rotating; and a transmission means arranged between said output shaft of said electric motor and said tilting shaft, wherein said transmission means comprises a backlash configured for having a predetermined amount of allowed rotation between said output shaft of said electric motor and said tilting shaft, whereby a rotational movement of said tilting shaft is absorbed by the transmission means and not transmitted to said output shaft or to said braking device such that said output shaft is immobilized by said braking device.

2. The sealing valve arrangement according to claim 1, wherein said predetermined amount of allowed rotation is between 0.1° and 0.5°.

3. The sealing valve arrangement according to claim 1, wherein said braking device is an electric motor-brake.

4. The sealing valve arrangement according to claim 1, wherein said predetermined amount of allowed rotation is between 0.25° and 0.35°.

5. The sealing valve arrangement according to claim 1, wherein the shutter is configured to move when the braking device is engaged and the shutter is in the closed position.

6. The sealing valve arrangement according to claim 1, wherein an underneath side of said shutter is configured to receive outside pressure such that said shutter is disposed against said valve seat and said tilting shaft is thereby further rotated.

7. The sealing valve arrangement according to claim 1, wherein said transmission means comprises a gearing mechanism configured to provide the backlash.

8. The sealing valve arrangement according to claim 7, wherein said transmission means comprises a planetary gear, helical gear or bevel gear.

9. The sealing valve arrangement according to claim 1, wherein a soft sealing means is arranged between said shutter and said valve seat, wherein said soft sealing means is compressible under high pressure.

10. The sealing valve arrangement according to claim 9, wherein said soft sealing means is a silicone seal ring.

11. A lower sealing valve housing for a shaft furnace charging installation, said housing comprising a sealing valve arrangement according to claim 1, and; said valve seat supported by said housing and cooperating with said shutter of said sealing valve arrangement.

12. A method for operating a sealing valve of a shaft furnace charging installation, wherein said sealing valve comprises a sealing valve arrangement according to claim 1, said method comprising: operating said electric motor connected to said tilting shaft so as to bring said shutter into a sealing contact against said valve seat; stopping said electric motor and engaging said braking device so as to stop said output shaft of said electric motor from rotating; applying outside pressure to an underneath side of said shutter so as to further press said shutter against said valve seat, wherein said tilting shaft is thereby further rotated; wherein said transmission means is configured so as to absorb a further rotation of said tilting shaft without transmitting this further rotation to said output shaft of said electric motor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) A preferred embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:

(2) FIG. 1 is a perspective view of a lower seal valve assembly with a sealing valve arrangement according to the invention; and

(3) FIG. 2 is a cross-sectional view of the lower seal valve assembly of FIG. 1.

DESCRIPTION OF PREFERRED EMBODIMENTS

(4) Generally, a shaft furnace installation comprises a shaft furnace with a shaft furnace charging installation arranged thereabove for feeding charge material into the shaft furnace.

(5) The shaft furnace charging installation may comprise a single hopper. Generally however, two or more hoppers are provided, allowing one hopper to be filled with charge material, while the charge material of another hopper is fed into the shaft furnace. As is well known in the art, each hopper comprises a material gate at the hopper outlet for maintaining the charge material in the hopper or releasing the charge material into the shaft furnace. Each hopper is furthermore equipped with an upper seal valve at the hopper inlet and a lower seal valve at the hopper outlet. These upper and lower seal valves are used to seal off the hopper pressure from atmosphere and from furnace pressure, respectively.

(6) FIGS. 1 and 2 schematically represent a lower seal valve assembly 2 of a shaft furnace charging installation.

(7) Such a lower seal valve assembly 2 comprises a valve housing 4 with an inlet 6 communicating with a hopper outlet and an outlet 8 communicating with a distribution device (not shown) for feeding charge material into the shaft furnace. The charge material received from the hopper via the hopper outlet and that passes through the inlet 6 of the valve housing 4, then passes through the outlet 8 and arrives to the distribution device.

(8) The lower seal valve assembly 2 further comprises an annular valve seat 10 that is situated inside the valve housing 4, and a sealing valve arrangement 14 with a valve closing element, or shutter 12, that is adapted to cooperate with the valve seat 10 for sealing the inlet 6. The shutter 12 is operatively connected to a tilting shaft 24 by means of a support arm 22 in order to move the shutter 12 into and out of contact with the valve seat 10. The sealing valve arrangement 14 is configured to move the shutter 12 between an open position (not shown) and a closed position as seen on FIGS. 1 and 2. The shutter 12 is further equipped with an annular soft sealing means 16, which is, in the embodiment shown, associated with the shutter 12.

(9) The sealing means 16 is to be pressed against a sealing surface on the valve seat 10 for providing gas-tightness. Alternatively, the sealing means 16 may be provided on the valve seat 10.

(10) The sealing valve arrangement 14 further comprises an electric motor 26, a transmission means 28 and a braking device 30. The electric motor 26 comprises an output shaft (not shown) cinematically coupled with the tilting shaft 24 via the transmission means 28.

(11) The electric motor 26 is operated to rotate the tilting shaft 24 so as to move the shutter 12 between the open position and the closed position. The rotation from the open position to the closed position is of an angle comprised between 0 and 100°.

(12) When the shutter 12 is in the closed position, the braking device 30 is engaged and the electric motor 26 is turned off, thereby essentially maintaining the shutter 12 in the closed position. The braking device 30, which may be an electric motor brake, is preferably triggered simultaneously with the electric motor 26 being turned off. It will be understood that a short delay in turning off the electric motor 26 may be tolerated. Such delay should however not exceed a few seconds, preferably not exceed 2 seconds, in order to avoid overheating of the electric motor 26. Similarly, when the shutter 12 is in the open position, the braking device 30 can be engaged and the electric motor 26 can be turned off.

(13) As no voltage is applied to the electric motor 26 while the shutter 12 is maintained in the open or closed position, the electric power consumption of the electric motor 26 can be reduced. Also, heating up of the electric motor 26 can be reduced, thereby avoiding the need for additional cooling of the electric motor 26. Essentially, electric power is only needed while the shutter 12 is to be moved from the open position to the closed position and vice-versa.

(14) The transmission means 28 arranged between the output shaft of the electric motor 26 and the tilting shaft 24 comprises a backlash, or play, configured for having a predetermined amount of allowed rotation between the output shaft of the electric motor 26 and the tilting shaft 24. Thus, even with the braking device 30 engaged when the shutter 12 is in its closed position, certain movement of the shutter 12 is possible. The transmission means 28 may comprise a gearing mechanism, preferably a planetary gear.

(15) As the pressure in the hopper is reduced, the pressure difference between shaft furnace and hopper increases. This increasing pressure difference acts on the underneath side 32 of the shutter 12 and pushes the shutter 12 tighter against the valve seat 10, causing rotational movement of the tilting shaft 24.

(16) However, due to the backlash provided by the transmission means 28, the rotational movement of the tilting shaft 24 caused by the above mentioned pressure difference is absorbed by the transmission means 28 and not transmitted to the output shaft of the electric motor 26, nor to the braking device 30. Thus, the rotational movement of the tilting shaft 24 cannot damage the output shaft of the electric motor 26 which is immobilized by the braking device 30.

LEGEND OF REFERENCE NUMBERS

(17) TABLE-US-00001 2 lower seal valve assembly 4 valve housing 6 inlet 8 outlet 10 annular valve seat 12 shutter 14 sealing valve arrangement 16 sealing means 22 support arm 24 tilting shaft 26 electric motor 28 transmission means 30 braking device 32 underneath side of shutter