JP2013210165A - Device for supplying fluidizing particles to fluidized bed gasifying furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device for supplying fluidizing particles to a fluidized bed gasifying furnace, capable of preventing outside air from flowing inside the furnace from a casting part of fluidizing particles when casting the fluidizing particles into the fluidized bed gasifying furnace.SOLUTION: A device for supplying fluidizing particles to a fluidized bed gasifying furnace includes: a conveyor casing 443 equipped with a tubular peripheral wall extending from an opening 445a to a particle casting part 17; a screw shaft 444 that can convey the fluidizing particles supplied from the opening 445a by rotation of the conveyor casing in the conveyor casing 443; and a fluidizing particle accumulation part 42 that is deposited at the upper side of the opening 445a and supplies the fluidizing particles filled inside from the opening 445a in the conveyor casing 443 so as to be piled up on the fluidizing particles in the conveyor casing 443. The conveyor casing 443 is tilted so that the particle casting part 17 side becomes an upper position than the opening 445a side.

Description

  The present invention relates to a fluidized particle supply apparatus that supplies fluidized particles into a fluidized bed gasification furnace that extracts combustible gas from the waste by heating the waste in a fluidized bed in which fluidized particles are fluidized.

  Conventionally, a gasification system disclosed in Patent Document 1 is known. In this gasification system, as shown in FIG. 3, the fluidized particles discharged together with incombustibles from the fluidized bed gasification furnace 100 are returned to the fluidized bed gasification furnace 100 to be circulated. ing. Specifically, it is as follows.

  The fluidized bed gasification furnace 100 has fluidized particles (for example, cinnabar sand) inside the furnace, and heats the waste in the fluidized bed 102 in which the fluidized particles are fluidized, thereby combustible gas ( Remove pyrolysis gas). In the fluidized bed gasification furnace 100, wastes, incombustibles and the like after the combustible gas is taken out are discharged out of the furnace together with the fluidized particles. The fluidized particles discharged to the outside of the furnace together with the incombustibles and the like are separated from the incombustibles and the like in the separation device 104 and then returned to the furnace by the fluidized particle circulation elevator 106 and the like to constitute the fluidized bed 102 again. To do.

  Here, in the fluidized bed gasification furnace 100, since combustible gas is generated in the furnace, unnecessary air from outside the furnace (other than air that is actively supplied into the furnace for combustion control). It is necessary to prevent air) from entering the furnace. In the fluidized bed gasification furnace 100, the fluidized particle injection valve 108 is provided at a site where the fluidized particles discharged together with incombustibles and the like are returned (input) into the furnace again. By closing 108, the unnecessary air is prevented from flowing into the furnace.

JP 2004-263886 A

  However, in the above fluidized bed gasification furnace 100, when returning the discharged fluidized particles into the furnace, the fluidized particle introduction valve 108 is opened to introduce fluidized particles. Air may flow into the furnace.

  Therefore, in view of the above problems, the present invention provides a fluidized bed that can prevent external air from flowing into the furnace from the fluidized particle charging site even when the fluidized particles are charged into the fluidized bed gasification furnace. It is an object of the present invention to provide a fluidized particle supply apparatus for a gasification furnace.

  In order to solve the above problems, the present invention provides a fluidized particle supply device for supplying fluidized particles into a fluidized bed type gasification furnace from a particle input unit provided in the fluidized bed type gasification furnace, wherein the fluidized particle A conveyor casing having a cylindrical peripheral wall extending to the particle input portion at a position horizontally separated from the opening, and is rotatably accommodated inside the conveyor casing. A screw shaft capable of conveying the fluidized particles supplied from the opening to the conveyor casing by the rotation to the particle charging unit and the upper side of the opening can be filled with the fluidized particles. In addition, the fluidized particle reservoir for supplying the filled fluidized particles to the conveyor casing from the opening so as to be stacked on the fluidized particles in the conveyor casing. And, equipped with a. And the said conveyor casing inclines so that the said particle insertion part side may become an upper position rather than the said opening part side.

  According to such a configuration, the fluid particles in the fluid particle storage unit and the conveyor casing function as a material seal, so that even when fluid particles are introduced into the fluidized bed gasification furnace, the external air remains in the fluid particles. It is possible to prevent the particles from flowing into the fluidized bed gasifier through the supply device. Specifically, when the fluidized particle reservoir is filled with fluidized particles, the fluidized particle reservoir is supplied so as to be stacked on the fluidized particles in the conveyor casing through the opening. At least the inside of the conveyor casing in the vicinity of the opening is filled with fluid particles and becomes dense due to the weight of fluid particles in the fluid particle reservoir stacked on the upper side, and at the bottom of the fluid particle reservoir, When the flowing particles are in a dense state due to the weight, the flowing particles function as a material seal, and the flow of air from the flowing particle storage unit to the particle input unit through the conveyor casing is prevented. Moreover, even when the fluidized particles are transported toward the particle input portion in the conveyor casing by the rotation of the screw shaft, the force acts on the fluidized particles toward the opening due to the inclination of the conveyor casing. The dense state of the fluidized particles around the opening is maintained, and the function as a material seal is maintained. As a result, while supplying fluidized particles into the fluidized bed gasification furnace from the particle charging unit, it is possible to prevent external air from flowing into the fluidized bed gasification furnace through the fluidized particle supply device. Can do.

  In the fluidized particle supply apparatus according to the present invention, the fluidized particle supply device includes a drive unit that rotationally drives the screw shaft, and a control unit that controls the drive unit, and the fluidized particle storage unit is configured to store the fluidized particles stored therein. Preferably, the control unit has a level meter capable of detecting an upper end position, and the control unit stops the driving unit when the upper end position of the flowing particles detected by the level meter becomes lower than a predetermined height position.

  According to such a configuration, the control unit detects that the number of fluidized particles stored in the fluidized particle reservoir is reduced (the upper end position of the fluidized particles is lower than the predetermined height position) by the level meter, and the control unit By stopping the conveyor, the supply of fluidized particles into the fluidized bed gasifier is automatically performed before the fluidized particles in the fluidized particle storage unit and the conveyor casing are reduced so that the fluidized particles do not function as a material seal. Can be stopped.

  As described above, according to the present invention, the fluidized bed gas that can prevent external air from flowing into the furnace from the fluidized particle injection portion even when the fluidized particles are charged into the fluidized bed gasification furnace. An apparatus for supplying fluidized particles to a chemical furnace can be provided.

It is a block diagram of the gasification system concerning this embodiment. It is a schematic block diagram of the fluidized particle supply apparatus which concerns on this embodiment. It is a block diagram of the conventional gasification fusion system.

  Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

  The fluidized particle supply apparatus of this embodiment supplies fluidized particles to a fluidized bed gasification furnace used in, for example, a gasification system that extracts combustible gas from waste. In the following, first, the gasification system 10 will be described with reference to FIG. 1, and then the fluidized particle supply device will be described.

  The gasification system 10 includes a fluidized bed gasification furnace 11, a fluidized particle circulation unit 20, and a gas processing unit 30.

  A fluidized bed gasification furnace (hereinafter, also simply referred to as “gasification furnace”) 11 heats waste in a fluidized bed 18 in which fluidized particles are fluidized, thereby combustible gas (pyrolysis) from the waste. Gas). The gasification furnace 11 includes a furnace body 12 having fluidized particles therein, a waste supply unit 13 for introducing waste into the furnace body 12, and fluidizing and discarding fluidized particles inside the furnace body 12. And an air supply unit 14 for supplying air for burning an object. In the lower part of the furnace body 12, there is provided a discharge part 15 for discharging a mixture of waste particles and the like after the fluidized particles, incombustibles and combustible gas are taken out. An exhaust unit 16 for discharging the generated combustible gas is provided. In addition, a particle input unit 17 for supplying fluidized particles from above the fluidized bed 18 is provided at an intermediate portion in the height direction of the furnace body 12.

  The fluidized particles are particles for forming the fluidized bed 18 inside the furnace body 12 and heating the waste. That is, when the fluidized particles heated to a high temperature by the combustion of a part of the waste are mixed with the waste, the waste is gasified and combustible gas is generated. In the present embodiment, for example, silica sand is used as the fluidized particles. More specifically, for example, cinnabar No. 4 or cinnabar No. 5 is used as the fluidized particles.

  The fluidized particle circulation unit 20 includes an incombustible material discharge device 21, a fluidized particle circulation elevator 22, a fluidized particle storage tank 23, and a fluidized particle supply device 40, and the fluidized particles discharged from the furnace body 12. Is returned to the furnace body 12 again.

  The incombustible material discharge device 21 separates the fluidized particles, the incombustible material, and the like from the mixture discharged from the discharge unit 15 of the furnace body 12. The fluidized particles separated from the mixture by the incombustible material discharging device 21 are conveyed to the fluidized particle circulation elevator 22 by the fluidized particle conveyor 24, and the incombustible materials separated from the mixture by the incombustible material discharging device 21 are incombustible. The product is conveyed to the incombustible material yard 26 by the material conveyor 25.

  The fluid particle circulating elevator 22 conveys the fluid particles separated by the incombustible discharge device 21 to a position above the particle input unit 17 of the furnace body 12. The fluid particle circulation elevator 22 switches the fluid particles transported to the upper position by switching the first damper 22a and the second damper 22b to the fluid particle supply device 40, the fluid particle storage tank 23, or the incombustible material yard 26. Supply. Specifically, the fluid particle circulating elevator 22 normally supplies fluid particles to the fluid particle supply device 40. Then, the fluid particle circulating elevator 22 switches at least one of the first damper 22a and the second damper 22b when the fluid particles stored in the fluid particle storage part of the fluid particle supply device 40 reaches a predetermined amount. Thus, the supply destination of the fluidized particles is switched to the fluidized particle storage tank 23 or the incombustible material yard 26. Then, when the fluidized particles stored in the storage region are reduced from the predetermined amount, the fluidized particle circulating elevator 22 switches the fluid particle supply destination to the fluidized particle supply device 40 by switching the first damper 22a. .

  If the fluidized particles continue to be used in the gasification furnace 11, the particle size of the fluidized particles increases due to adhesion of incombustibles and the like, and the air permeability in the fluidized bed 18 changes, so the particle size is larger than a predetermined value. The formed fluid particles are sieved in the incombustible material discharge device 21 and supplied to the incombustible material yard 26.

  The fluidized particle storage tank 23 stores a predetermined amount of fluidized particles, and the amount of fluidized particles circulating when the furnace body 12 is started up or between the furnace body 12 and the fluidized particle circulating unit 20 is greatly reduced. When the amount of fluidized particles in the furnace body 12 is increased, fluidized particles are supplied to the fluidized particle circulation elevator 22.

  The gas processing unit 30 includes a gas reforming furnace 31, a gas cooler 32, a bag filter 33, an induction fan 34, and a pyrolysis gas (a gas containing a combustible gas) discharged from the gasification furnace 11. ) Reforming treatment is performed.

  The gas reforming furnace 31 reforms (cracks) the pyrolysis gas discharged from the gasification furnace 11 to decompose tar and the like contained in the pyrolysis gas and can be reused as fuel gas or raw material gas (combustible) Gas). The gas cooler 32 cools the combustible gas reformed in the gas reforming furnace 31. The bag filter 33 removes dust, dust and the like from the combustible gas after cooling. The induction fan 34 attracts the pyrolysis gas generated in the gasification furnace 11 to the gas processing unit 30. As the pyrolysis gas is attracted from the gasification furnace 11 (furnace main body 12) by the induction fan 34, the pressure in the gasification furnace 11 becomes atmospheric pressure or less.

  The combustible gas subjected to the reforming process in the gas processing unit 30 is supplied as a fuel to a subsequent gas turbine, a gas boiler, or the like.

  Next, the fluidized particle supply device 40 will be described with reference to FIG.

  The fluid particle supply device 40 includes a fluid particle storage unit 42, a fluid particle transport unit 44, and a control unit 46.

  The fluidized particle storage unit 42 stores the fluidized particles supplied from the fluidized particle circulation elevator 22 and supplies the stored fluidized particles to the fluidized particle transport unit 44. The fluidized particle reservoir 42 is provided on the reservoir main body 421, the connection part 422 connecting the reservoir main body 421 and the fluidized particle transport unit 44, and the upper part of the reservoir main body 421, and flows into the reservoir main body 421. A charging unit 423 capable of charging particles and a plurality (four in this embodiment) of level meters 424a, 424b, 424c, 424d attached to the storage unit main body 421 are provided.

  The reservoir main body 421 has a hollow column shape extending vertically, and stores fluid particles therein.

  The connection part 422 connects the lower end part of the storage part main body 421 and the screw conveyor 441 so that the inside of the storage part main body 421 communicates with the inside of the screw conveyor 441 in the fluidized particle transport part 44.

  Each level meter 424a, 424b, 424c, 424d is in contact with the upper end position (the height position of the boundary surface between the stored flow particle and the space above it) of the flow particle stored in the storage unit main body 421. Detect without contact. As such a level meter, for example, a capacitance type level meter, a paddle type level meter, a laser type level meter or the like is used.

  Each level meter 424a, 424b, 424c, 424d outputs a detection signal when it detects the upper end position. In the present embodiment, four level meters (a first level meter 424a, a second level meter 424b, a third level meter 424c, and a fourth level meter 424d) are attached to the storage unit main body 421. Specifically, the four level meters 424a, 424b, 424c, 424d are arranged in a line at intervals in the vertical direction.

  In addition, although only one level meter 424a, 424b, 424c, 424d of this embodiment is provided in the horizontal plane direction (same height position), it is not limited to this. That is, a plurality of level meters may be provided in the horizontal plane direction (same height position). Thereby, the misdetection of the level meter due to the deviation of the flowing particles in the reservoir main body 421 can be prevented. In particular, it is preferable that a plurality of level meters are provided at the same height position (in this embodiment, for example, the height positions of the level meters 424a and 424b) in the lower stage (lower part of the storage unit main body 421). According to such a configuration, erroneous detection of the level meter is effectively prevented.

  The fluidized particle transport unit 44 includes a screw conveyor 441 and a drive unit 442 that drives the screw conveyor 441.

  The screw conveyor 441 includes a conveyor casing 443, a screw shaft 444 accommodated inside the conveyor casing 443, and a support portion 448.

  The conveyor casing 443 includes a casing main body 445, an inspection port portion 446, and a fluid particle discharge portion 447.

  The casing body 445 has a cylindrical peripheral wall, and both ends of the peripheral wall are closed. A connection part 422 of the fluid particle storage part 42 is connected to an opening part 445 a provided at the upper end part of one end part (left end part in FIG. 2) of the casing body 445. As a result, the inside of the storage unit main body 421 and the inside of the casing main body 445 communicate with each other through the connection unit 422.

  The inspection port 446 is an opening provided at the upper end of the other end of the casing body 445 (the end opposite to the one end: the right end in FIG. 2). A lid 446 a is attached to the inspection port portion 446. By removing the lid 446a, the inside of the casing body 445 can be inspected from the inspection port portion 446.

  The fluidized particle discharge unit 447 discharges the fluidized particles in the casing body 445 into the particle input unit 17 of the furnace body 12. Specifically, the fluidized particle discharger 447 connects the lower end of the other end of the casing body 445 and the particle charging part 17 of the furnace body 12, and connects the interior of the casing body 445 and the interior of the furnace body 12. Communicate. The fluid particle discharge unit 447 is connected to the particle input unit 17 in an airtight state. Thereby, the inside of the fluid particle storage part 42 communicates with the inside of the casing main body 445 and the inside of the fluid particle discharge part 447 in an airtight state through the inside of the fluid particle discharge part 447.

  The support body 448 is inclined in such a manner that the end on the fluid particle discharge part 447 side (particle input part 17 side) is positioned higher than the end on the connection part 422 side of the fluid particle storage part 42. Support. Specifically, the support portion 448 supports the casing body 445 so that the central axis of the casing body 445 is, for example, 15 ° with respect to the horizontal. The angle of the central axis of the casing body 445 with respect to the horizontal is preferably 10 ° to 45 °. Thus, when the angle of the central axis is 10 ° to 45 °, there is no significant difference in the material seal effect due to the compaction of the fluid particles in the casing body 445. On the other hand, when the angle of the central axis is less than 10 °, the material sealing effect due to the compaction of the fluidized particles in the casing body 445 is reduced, and air flows in the casing body 445.

  The screw shaft 444 includes a shaft main body 444 a extending in the same direction as the casing main body 445, and screw (spiral) blades 444 b provided on the peripheral surface of the shaft main body 444 a, and the inside of the casing main body 445 includes the shaft main body 444 a. It is accommodated so as to be rotatable around the central axis.

  The drive unit 442 is connected to a screw shaft 444 (shaft body 444a) housed in the casing body 445, and rotationally drives the screw shaft 444 based on an instruction signal from the control unit 46. In this way, when the screw shaft 444 is rotated by the drive unit 442, the fluidized particles are conveyed through the inside of the casing main body 445 from the end on the fluidized particle storage unit 42 side toward the end on the fluidized particle discharge unit 447 side. Is done.

  The control unit 46 is connected to the level meters 424a, 424b, 424c, 424d and the drive unit 442, and based on the detection signals from the level meters 424a, 424b, 424c, 424d, the drive unit 442, the fluidized particle circulation elevator. 22 and an instruction signal are output to the waste supply unit 13 and the like. Specifically, it is as follows.

  In the fluidized particle storage unit 42 at the start of operation of the fluidized bed gasifier 11, there is an amount of fluidized particles such that the upper end position of the fluidized particles is between the second level meter 424b and the third level meter 424c. Reserved. And the control part 46 drives the fluid particle supply apparatus 40 and the elevator 22 for fluid particle circulation.

  When the supply amount of the fluid particles from the fluid particle supply device 40 to the furnace body 12 is larger than the fluid particle supply amount from the fluid particle circulation elevator 22 to the reservoir main body 421, the upper end of the fluid particles in the reservoir main body 421. The position gradually decreases. When the upper end position reaches the position of the second level meter 424b, the control unit 46 receives the detection signal from the second level meter 424b and stops the driving unit 442 (that is, stops the fluidized particle supply device 40). ) An instruction signal is output toward the drive unit 442. Thereby, the fall of the upper end position of the fluid particle in the storage part main body 421 stops, and the material seal effect by the fluid particle in the casing main body 445 from the fluid particle storage part 42 is maintained.

  Temporarily, the difference between the supply amount of the fluid particles from the fluid particle supply device 40 to the furnace body 12 and the supply amount of the fluid particles from the fluid particle circulation elevator 22 to the reservoir main body 421 is very large. When the upper end position of the flowing particles in the main body 421 is lowered to the first level meter 424a, the control unit 46 receives a detection signal from the first level meter 424a and stops the waste supply unit 13 Is output toward the waste supply unit 13 to stop the supply of waste into the furnace body 12. Thereby, the production amount of the combustible gas in the furnace body 12 is reduced. For this reason, the material seal effect by the fluidized particles is reduced by reducing the amount of fluidized particles in the reservoir main body 421, so that even if air flows into the furnace body 12 through the fluidized particle supply device 40, The reaction between the combustible gas and the air in the furnace body 12 can be suppressed.

  When the upper end position of the fluidized particles is lower than the second level meter 424b, the fluidized particle supply device 40 is stopped. Therefore, the fluidized particles circulating elevator 22 supplies the reservoir main body 421 with the fluidized particles supplied to the reservoir main body 421. The upper end position of the fluidized particles gradually rises. When the upper end position rises to the third level meter 424c, the control unit 46 receives the detection signal from the third level meter 424c and instructs to drive the drive unit 442 (that is, to operate the fluid particle supply device 40). The signal is output toward the drive unit 442.

  When the supply amount of the fluid particles from the fluid particle supply device 40 to the furnace main body 12 is smaller than the fluid particle supply amount from the fluid particle circulation elevator 22 to the reservoir main body 421, the upper end of the fluid particles in the reservoir main body 421. The position gradually rises. When the upper end position rises to the fourth level meter 424d, the control unit 46 outputs an instruction signal for stopping the fluidized particle circulating elevator 22 to the fluidized particle circulating elevator 22. As a result, the supply of fluid particles from the fluid particle circulation elevator 22 to the reservoir main body 421 is stopped and rubbed, while the drive unit 442 continues to drive, so that the supply of fluid particles into the furnace main body 12 is maintained. In addition, the upper end position of the flowing particles in the storage unit main body 421 gradually decreases. Accordingly, when the upper end position is lowered to the third level meter 424c, the control unit 46 receives the detection signal from the third level meter 424c and sends an instruction signal for driving the fluid particle circulating elevator 22 to the fluid particle. Output toward the circulating elevator 22.

  Note that the control unit 46 may switch the first damper 22a instead of turning the fluid particle circulating elevator 22 on / off. In this case, since the fluidized particle circulation elevator 22 continues to operate, it is possible to control the amount of fluidized particles supplied to the reservoir main body 421 without stopping the extraction of non-combustible materials from the furnace body 12.

  According to the fluidized particle supply device 40 described above, the fluid particles in the reservoir main body 421 and the casing main body 445 function as a material seal, so that external air can be supplied even when fluid particles are introduced into the furnace body 12. Can be prevented from flowing into the furnace main body 12 from the particle input unit 17 through the fluidized particle supply device 40. Specifically, when the storage unit body 421 is filled with fluid particles, the reservoir unit body 421 supplies the filled fluid particles so as to be stacked on the fluid particles in the casing body 445 through the opening 445a. . As a result, at least the inside of the casing body 445 around the opening 445a is filled with the fluidized particles, and is densely packed by the weight of the fluidized particles in the reservoir body 421 stacked on the upper side. In addition, the flowing particles are densely packed by the weight of the upper flowing particles at the bottom of the reservoir main body 421. As a result, the fluidized particles act as a material seal, and the flow of air from the fluidized particle reservoir 42 to the particle inlet 17 through the casing body 445 is prevented. In addition, even when the fluidized particles are transported toward the particle introduction unit 17 through the casing body 445 by the rotation of the screw shaft 444, the force acts on the fluidized particles toward the opening 445a due to the inclination of the casing body 445. The dense state of the fluidized particles at least around the opening 445a of the casing body 445 is maintained, and the function as a material seal is maintained. Accordingly, it is possible to prevent external air from flowing into the furnace main body 12 from the particle input section 17 through the fluidized particle supply device 40 while supplying the flowing particles from the particle input section 17 into the furnace main body 12.

  Further, the control unit 46 stops the screw conveyor 441 (drive unit 442) by detecting that the second level meter 424b has decreased the amount of fluidized particles stored in the storage unit main body 421. And the supply of fluid particles into the furnace body 12 can be automatically stopped before the fluid particles do not function as a material seal due to the decrease of fluid particles in the casing body 445.

  In addition, the fluid particle supply apparatus of the present invention is not limited to the above-described embodiment, and it is needless to say that various changes can be made without departing from the gist of the present invention.

  In the above embodiment, the fluid particle storage unit 42 is provided with a plurality of level meters (first to fourth level meters 424a, 424b, 424c, 424d), but only one may be used. In this case, if the first level meter 424a is provided, the fluidized particles flow into the furnace body 12 before the fluidized particles do not function as a material seal due to the decrease of the fluidized particles in the storage body 421 and the casing body 445. The supply of particles can be stopped automatically.

DESCRIPTION OF SYMBOLS 11 Fluidized bed type gasifier 17 Particle input part 40 Fluidized particle supply apparatus 42 Fluidized particle storage part 46 Control part 424a 1st level meter 424b 2nd level meter 424c 3rd level meter 424d 4th level meter 441 Screw conveyor 442 Drive part 443 Conveyor casing 444 Screw shaft

Claims (2)

A fluidized particle supply device that supplies fluidized particles into a fluidized bed gasification furnace from a particle input unit provided in the fluidized bed gasification furnace,
A conveyor casing having a cylindrical peripheral wall having an opening for receiving the fluidized particles and extending to the particle input portion at a position away from the opening in the horizontal direction;
A screw shaft that is rotatably accommodated in the conveyor casing, and that is capable of conveying the fluid particles supplied into the conveyor casing from the opening by the rotation to the particle input unit;
Arranged above the opening, the fluidized particles can be filled therein, and the filled fluidized particles are supplied from the opening into the conveyor casing so as to be stacked on the fluidized particles in the conveyor casing. A fluidized particle storage unit that
The conveyor casing is a fluidized particle supply device that is inclined such that the particle input part side is positioned higher than the opening part side. The fluidized particle supply device according to claim 1,
A drive unit for rotationally driving the screw shaft;
A control unit for controlling the drive unit,
The fluidized particle reservoir has a level meter capable of detecting the upper end position of fluidized particles stored inside,
The said control part is a fluid particle supply apparatus which stops the said drive part, if the upper end position of the said fluid particle detected by the said level meter becomes lower than predetermined | prescribed height position.

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