CN103600938B - Automatic coal dredging device for raw coal conveying system in thermal power plant - Google Patents
Automatic coal dredging device for raw coal conveying system in thermal power plant Download PDFInfo
- Publication number
- CN103600938B CN103600938B CN201310488919.5A CN201310488919A CN103600938B CN 103600938 B CN103600938 B CN 103600938B CN 201310488919 A CN201310488919 A CN 201310488919A CN 103600938 B CN103600938 B CN 103600938B
- Authority
- CN
- China
- Prior art keywords
- coal
- raw coal
- air
- puff prot
- raw
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Landscapes
- Air Transport Of Granular Materials (AREA)
- Control Of Conveyors (AREA)
Abstract
The invention discloses an automatic coal dredging device for a raw coal conveying system in a thermal power plant. The automatic coal dredging device comprises a plurality of air jet holes and an air supply system, the air jet holes are formed in the inner wall of a raw coal conveying system device, the air supply system is communicated with the air jet holes through air pipelines, and the operating state of the air supply system is changed by a control system. The automatic coal dredging device is simple in structure, convenient to operate, low in cost, high in economic performance and safe and reliable in operation, less vibration is generated, and normal operation of other devices cannot be affected. By the aid of the automatic coal dredging device, the problem of coal blockage failure due to various reasons is fundamentally and thoroughly solved, and normal coal supply of a coal feeder and normal operation of a subsequent device are ensured.
Description
Technical field
The present invention relates to Shu Mei field, thermal power plant, a kind of dredger for dredging coal charge.
Background technology
Powder manufacturing apparatus in heat power plant boiler system is properly functioning is the key of boiler normal combustion, coal supply normal
Whether directly affect process and the Boiler Stable Combustion of pulverized coal preparation system, therefore in boiler normal course of operation, induction system
Normal enough coal supplies it is critical that.Conveyer system of raw coal 1 includes storing the raw coal bucket 11 of raw coal, passing sequentially through reducer pipe
12, the feeder 15 that coal spout 14 connects with raw coal bucket coal dropping port, is provided with feeder between reducer pipe 12 and coal spout 14 and enters
Coal mouth gate valve 13, arranges oriented coal pulverizer and transmits the feed belt 16 of raw coal, in raw coal bucket below the lower coal mouth of feeder 15
Raw coal drops to feeder from the coal dropping port of raw coal bucket through reducer pipe by gravity, then the feed belt below feeder is sent to
Coal pulverizer, during raw coal transmits often because former pit ash inferior is big, viscosity greatly, particularly rainy season raw coal wet
Degree is big, makes the raw coal in raw coal bucket occur on feeder top overstocking phenomenon, causes raw coal bucket to block, it is impossible to ensure enough to
Coal amount, causes the coal amount entering coal pulverizer to reduce, affects the operation of coal pulverizer and follow-up equipment, further result in boiler combustion
Shakiness, unit load shedding, reduces the safety and economic operation efficiency of boiler.
At present, during feeder is properly functioning, when chute blockage phenomenon occurs, process frequently with following three kinds of modes:
1) using the mode that vibrator beats, shortcoming is that vibration is big, easily affects the operation of other equipment, and work efficiency is the highest, the most also
There is the defect shaking more real and more real, even make anti-clogging coal liner plate on coal bunker wall get loose and cause more serious consequence.2) sledgehammer is used
The method manually beaten, sledgehammer easily smashes equipment, and labor intensity is big, and the most more rapping, coal cinder is the most solid, and not only working performance is low
Under, in some instances it may even be possible to the safety of staff is threatened.3) using air bubble or dredging machine, shortcoming is also inefficient,
Operation maintenance workload is big.
Summary of the invention
The technical issues that need to address of the present invention be to provide a kind of apply in the conveyer system of raw coal of thermal power plant from
Dynamic thin device for coal, it is possible to fundamentally thoroughly solve the chute blockage fault caused due to a variety of causes, it is ensured that the normal of feeder supplies
Coal and follow-up equipment properly functioning.
For solving above-mentioned technical problem, the technical solution adopted in the present invention is:
Automatic sparse device for coal in the conveyer system of raw coal of thermal power plant, including being arranged on conveyer system of raw coal equipment
Several puff prots on inwall and air supply system connect with puff prot by air line, described air supply system passes through to control
System processed changes duty.
The concrete structure of described air supply system is: described air supply system includes by pipeline and thermal power plant compressed air
The air compressor of system connectivity, the outfan of air compressor passes through pipeline communication one air accumulator, and the outfan of air accumulator divides
Tong Guo not connect with each puff prot by air line；It is respectively provided with a valve on described each air line.
Being improved by of air supply system of the present invention: be provided with the heating for heated compressed air in described air accumulator
Device, the controlled end connection control system of heater.
The concrete structure of described control system is: described control system includes switch board, is arranged in conveyer system of raw coal
For gathering the disconnected coal signal pickup assembly of lower coal amount and being arranged on each air line above feed belt below feeder
Electromagnetic valve；The input of described switch board is connected with the outfan of disconnected coal signal pickup assembly, and the outfan of switch board is respectively
It is connected with the controlled end of heater and each electromagnetic valve.
The concrete structure of described disconnected coal signal pickup assembly is: described disconnected coal signal pickup assembly is for exist by hinge
Baffle plate in coal mouth frame and the induction apparatus that triggered by swung amplitude under feeder, the outfan of induction apparatus connects and controls
The input of cabinet；The amplitude of fluctuation of described baffle plate determines according to coal-feeding quantity.
The another kind of structure of described disconnected coal signal pickup assembly is: described disconnected coal signal pickup assembly is for being arranged on transmission skin
Weighing and sensing assembly below band, the outfan of weighing and sensing assembly connects the input of switch board.
The present invention is improved by: described in the puff prot that is arranged in conveyer system of raw coal use inverse raw coal conveying direction to depend on
The secondary mode of operation alternately opened.
Owing to have employed technique scheme, the technological progress that the present invention obtains is:
Present configuration is simple and convenient to operate, with low cost, economic performance is high.The present invention is during thin coal, by control
Air supply system is controlled by system processed, thus realizes the inwall from each equipment of conveyer system of raw coal and start to dredge coal operation, passes through
Raw coal is dredged by gas, and the vibration of generation is less, safe and reliable to operation, does not affect the properly functioning of other equipment.This
Bright application can realize unattended, the requirement of Automatic Control, after the disconnected coal of conveyer system of raw coal blocking, it is possible to automatically collect
Signal, realizes further dredging automatically the starting of coal operation, automatic dredging and is automatically stopped, the most thorough solve due to
The chute blockage fault that a variety of causes causes, it is ensured that the normal coal supply of feeder and follow-up equipment properly functioning.
Accompanying drawing explanation
Fig. 1 is the structural representation of the present invention.
Fig. 2 is the control principle schematic diagram of the present invention.
Wherein: 1. conveyer system of raw coal, 11. raw coal buckets, 12. reducer pipes, 13. gate valves, 14. coal spouts, 15. feeders,
16. feed belts, 2. puff prot, 3. air supply system 31. air compressor, 32. air accumulators, 33. valves, 34. heaters, 4. control
System processed, 41. switch boards, 42. break coal signal pickup assembly, 421. baffle plates, 422. induction apparatuss, 423. weighing and sensing assemblies, and 43.
Electromagnetic valve, 5. air line.
In Fig. 1, the direction of arrow is the conveying direction of raw coal.
Detailed description of the invention
With specific embodiment, the present invention is described in further details below in conjunction with the accompanying drawings:
A kind of automatic sparse device for coal in the conveyer system of raw coal of thermal power plant, its structural representation is as shown in Figure 1.
Including air supply system 3, control system 4 and several puff prots 2, wherein to be separately mounted to conveyer system of raw coal 1 each for puff prot 2
On the inwall of individual equipment, puff prot 2 is connected with air supply system 3 by air line 5, and air supply system 3 is in the control of control system 4
Lower change duty.
Conveyer system of raw coal described in the present embodiment includes complying with that raw coal conveying direction sets gradually from top to bottom is former
Coal bunker 11, reducer pipe 12, gate valve 13, coal spout 14, feeder 15 and feed belt 16, puff prot is provided with five altogether.Its
Being provided with the first puff prot in middle coal spout 14, reducer pipe 12 is provided with the second puff prot, and raw coal bucket 11 sets the most successively
It is equipped with the 3rd puff prot, the 4th puff prot and the 5th puff prot.
Wherein air supply system 3 includes air compressor 31, air accumulator 32, valve 33 and heater 34.The number of valve 33
Measure identical with the quantity of puff prot 2, be separately positioned on the pipeline connecting puff prot；Heater 34 is arranged in air accumulator, adds
The controlled end connection control system 4 of hot device 34, starts under the instruction of control system or closes, in the winter time to storage during startup
Compressed air in gas tank heats.The input of air compressor 31 is by pipeline and thermal power plant compressed air system
Connection, the outfan of air compressor 31 passes through pipeline communication one air accumulator 32, and the outfan of air accumulator 32 passes through air respectively
Pipeline 5 connects with each puff prot 2.
Control system 4 includes switch board 41, disconnected coal signal pickup assembly 42 and several electromagnetic valves 43, electromagnetic valve 43
Quantity is identical with the quantity of puff prot 2, is separately positioned on the pipeline connecting puff prot；Disconnected coal signal pickup assembly 42 is arranged on
In conveyer system of raw coal 1 below feeder, above feed belt, it is used for gathering lower coal amount.The input of switch board is believed with disconnected coal
The outfan of number harvester 42 connects, and the outfan of switch board is respectively with the controlled end of heater and each electromagnetic valve 43 even
Connect.
Disconnected coal signal pickup assembly 42 can be baffle plate 421 and the combining form of induction apparatus 422, it is also possible to is to be separately provided
Weighing and sensing assembly 423.
As used baffle plate 421 and the combining form of induction apparatus 422, baffle plate 421 is then by hinge coal under feeder
In mouthful frame, baffle plate on feed belt under the effect of raw coal to raw coal conveying direction deflection；Induction apparatus 422 is also disposed at coal supply
Under machine in the frame of coal mouth, and triggered by swung amplitude；The outfan of induction apparatus connects the input of switch board；Described gear
The amplitude of fluctuation of plate determines according to coal-feeding quantity.Adopt the structure the disconnected coal signal pickup assembly of form, in operation process, when
When raw coal amount that feed belt normally carries is normal, baffle plate tilts certain angle, and now baffle plate can trigger induction apparatus, switch board
Receiving induction apparatus when being in triggering state, do not start electromagnetic valve action, air line ends；When raw coal amount reduces, i.e. say
Bright conveyer system of raw coal blocks, and now baffle plate angle of inclination diminishes, it is impossible to triggering induction apparatus, controller does not receives sensing
The signal that device returns, just starts to start electromagnetic valve action, and air line is opened, and puff prot is jet in conveyer system of raw coal, reaches
To the effect dispelling raw coal.
When disconnected coal signal pickup assembly 42 is as individually used weighing and sensing assembly 423, then weighing and sensing assembly 423 is arranged
In the lower section of feed belt, for measuring the raw coal amount of conveying on feed belt, when raw coal amount is less than standard value, weighing and sensing
Assembly 423 sends signal to switch board, and switch board controls electromagnetic valve action after receiving signal, and air line is opened, puff prot
Jet in conveyer system of raw coal, reaches to dispel the effect of raw coal.
It is defeated that two kinds of the most heretofore described disconnected coal signal pickup assembly 42 versions can be simultaneously located at raw coal
Send in system, to guarantee accurately to detect the raw coal amount fallen from feeder.
The work process of the present embodiment is as described below:
Open the gate valve 13 of feeder coal feed point, carry material to feeder, coal pulverizer and follow-up equipment successively.
When raw coal normally falls and there is not blocking, the conveying direction of raw coal is as shown in the sensing of arrow in Fig. 1, in coal bunker
Raw coal enter raw coal bucket, through reducer pipe 12, the gate valve 13 of feeder entrance, feeder import coal spout 14 after send into coal supply
Machine 15, raw coal falls into the feed belt 16 below feeder after feeder, thus realizes to coal pulverizer feeding.
When raw coal occurs blocking in induction system, disconnected coal signal pickup assembly collects the raw coal sending into feed belt
Amount can not meet requirement, causes belt to break coal, and disconnected coal signal pickup assembly sends the alarm signal of " belt break coal " to switch board,
Start the electromagnetic valve action on each air line simultaneously.
During switch board controls electromagnetic valve action, puff prot is used the most alternately to open against raw coal conveying direction
Mode of operation.I.e. it is first turned on being positioned at the electromagnetism being arranged on the first air line connected with the first puff prot in coal spout
Valve, makes the first puff prot spray air-flow to coal spout, and the work surface of compressed air entrance coal spout carries out the dredging in coal seam；When reaching
During to preset time, switch board closes the electromagnetic valve on the first air line, opens simultaneously and is arranged on and the second spray in reducer pipe
Electromagnetic valve on second air line of QI KOU connection, makes the second puff prot spray air-flow to reducer pipe, and compressed air enters and becomes
The work surface of footpath pipe carries out the dredging in coal seam；The like, it is then shut off the second puff prot and opens the 3rd puff prot, close the 3rd
Puff prot opens the 4th puff prot, closes the 4th puff prot and opens the 5th puff prot, until the 5th puff prot preset dredging time
Arriving, first round dredging process terminates, thus realizes the timing controlled that inverse raw coal conveying direction carries out dredging successively.
After completing a high pressure draught dredging process, if disconnected coal signal yet suffers from, then switch board controls electromagnetism valve actuation
Make, carry out second and take turns dredging, until raw coal can normally carry.
The present invention is as used in the winter time, and raw coal is relatively big due to humidity, easily occurs that coal cinder is tied in the course of conveying of raw coal
The phenomenon of ice, therefore needs to freeze the coal cinder freezed or be dried in raw coal course of conveying, and now switch board can control
The heater being positioned in air accumulator enters duty, and according to the temperature value set in switch board, carries out compressed air certainly
Dynamic heating, so that raw coal is freezed during thin coal and is dried by compressed air.
When the present invention realizes the running status of air supply system also by manual control mode, now all open at electromagnetic valve
Under logical state, the valve on Non-follow control air line just can realize manually dredging coal.
Claims (1)
1. the automatic sparse device for coal in the conveyer system of raw coal of thermal power plant, it is characterised in that: include being arranged on raw coal defeated
Send several puff prots (2) on system (1) equipment inner wall and the supply connected by air line (5) with puff prot (2)
System (3), described air supply system (3) changes duty by control system (4)；Described air supply system (3) includes by pipe
The air compressor (31) that road connects with thermal power plant compressed air system, the outfan of air compressor (31) passes through pipeline
Connecting an air accumulator (32), the outfan of air accumulator (32) is connected with each puff prot (2) by air line (5) respectively；Institute
State and on each air line (5), be respectively provided with a valve (33)；Described air accumulator is provided with the heating for heated compressed air
Device (34), the controlled end connection control system (4) of heater (34)；Conveyer system of raw coal includes complying with raw coal conveying direction from upper
Raw coal bucket (11), reducer pipe (12), gate valve (13), coal spout (14), feeder (15) and the transmission skin set gradually under and
Band (16), puff prot is provided with five altogether, is provided with the first puff prot in coal spout (14), and reducer pipe (12) is provided with the second spray
QI KOU, raw coal bucket (11) is disposed with the 3rd puff prot, the 4th puff prot and the 5th puff prot, described setting from bottom to top
Puff prot in conveyer system of raw coal uses the mode of operation that inverse raw coal conveying direction is the most alternately opened；
Described control system (4) includes switch board (41), is arranged in conveyer system of raw coal (1) below feeder on feed belt
Side is for the disconnected coal signal pickup assembly (42) gathering lower coal amount and the electromagnetic valve (43) being arranged on each air line (5)；
The input of described switch board is connected with the outfan of disconnected coal signal pickup assembly (42), the outfan of switch board respectively with heating
The controlled end of device and each electromagnetic valve (43) connects；
Described disconnected coal signal pickup assembly (42) be by hinge under feeder the baffle plate (421) in coal mouth frame and
The induction apparatus (422) triggered by swung amplitude, the outfan of induction apparatus connects the input of switch board；The pendulum of described baffle plate
Dynamic amplitude determines according to coal-feeding quantity；Described disconnected coal signal pickup assembly (42) is for be arranged on the weighing and sensing group below feed belt
Part (423), the outfan of weighing and sensing assembly connects the input of switch board；The two breaks coal signal pickup assembly (42) together
Time be arranged in conveyer system of raw coal.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201310488919.5A CN103600938B (en) | 2013-10-18 | 2013-10-18 | Automatic coal dredging device for raw coal conveying system in thermal power plant |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201310488919.5A CN103600938B (en) | 2013-10-18 | 2013-10-18 | Automatic coal dredging device for raw coal conveying system in thermal power plant |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN103600938A CN103600938A (en) | 2014-02-26 |
| CN103600938B true CN103600938B (en) | 2017-01-11 |
Family
ID=50119229
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201310488919.5A Active CN103600938B (en) | 2013-10-18 | 2013-10-18 | Automatic coal dredging device for raw coal conveying system in thermal power plant |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN103600938B (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103979230A (en) * | 2014-05-20 | 2014-08-13 | 国家电网公司 | High pressure steam hopper dredging device |
| CN104384148B (en) * | 2014-11-20 | 2016-09-07 | 中冶焦耐工程技术有限公司 | Coal-fired BASK winding-up blockage removal system |
| CN105460440B (en) * | 2015-12-28 | 2018-05-29 | 莱歇研磨机械制造(上海)有限公司 | A kind of powder cabin helps streaming system |
| CN109250524A (en) * | 2017-07-13 | 2019-01-22 | 大唐环境产业集团股份有限公司 | A kind of anti-blocking device for discharging |
| CN112791834B (en) * | 2021-01-21 | 2024-06-14 | 烟台龙源电力技术股份有限公司 | Anti-blocking device of coal mill and boiler |
| CN116300665B (en) * | 2023-05-24 | 2023-10-13 | 山东宏桥新型材料有限公司 | Linkage interlocking control circuit of air cannon |
Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SU880892A1 (en) * | 1979-11-16 | 1981-11-15 | Волгоградский Производственный Отдел Всесоюзного Ордена Ленина Проектно-Изыскательского И Научно-Исследовательского Института "Гидропроект" Им.С.Я.Жука | Receptacle for mobile cement storage |
| CN201785051U (en) * | 2010-08-06 | 2011-04-06 | 天瑞集团水泥有限公司 | Automatic detecting anti-blocking device of discharge bin |
| CN202030219U (en) * | 2011-04-06 | 2011-11-09 | 南通市华峰化工有限责任公司 | Screw feeder |
| CN202098736U (en) * | 2011-05-26 | 2012-01-04 | 煤炭工业济南设计研究院有限公司 | Ring type device capable of loosing coal bunker |
| CN203158773U (en) * | 2013-01-23 | 2013-08-28 | 濮阳中石集团有限公司 | Novel coal feeder |
| CN203222265U (en) * | 2012-12-11 | 2013-10-02 | 濮阳市亚利机械制造有限公司 | Intelligent air cannon |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| TW218915B (en) * | 1992-05-15 | 1994-01-11 | Mitsui Petroleum Chemicals Ind | |
| GB2430166A (en) * | 2005-08-02 | 2007-03-21 | Dps | Fluidising apparatus |
| CN201224584Y (en) * | 2008-04-14 | 2009-04-22 | 戴光荣 | One gas storage bag multi-connection air cannon |
| CN202400491U (en) * | 2012-01-17 | 2012-08-29 | 哈尔滨润河科技有限公司 | Coal chute pneumatic unblocking device capable of realizing automatic control |
-
2013
- 2013-10-18 CN CN201310488919.5A patent/CN103600938B/en active Active
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SU880892A1 (en) * | 1979-11-16 | 1981-11-15 | Волгоградский Производственный Отдел Всесоюзного Ордена Ленина Проектно-Изыскательского И Научно-Исследовательского Института "Гидропроект" Им.С.Я.Жука | Receptacle for mobile cement storage |
| CN201785051U (en) * | 2010-08-06 | 2011-04-06 | 天瑞集团水泥有限公司 | Automatic detecting anti-blocking device of discharge bin |
| CN202030219U (en) * | 2011-04-06 | 2011-11-09 | 南通市华峰化工有限责任公司 | Screw feeder |
| CN202098736U (en) * | 2011-05-26 | 2012-01-04 | 煤炭工业济南设计研究院有限公司 | Ring type device capable of loosing coal bunker |
| CN203222265U (en) * | 2012-12-11 | 2013-10-02 | 濮阳市亚利机械制造有限公司 | Intelligent air cannon |
| CN203158773U (en) * | 2013-01-23 | 2013-08-28 | 濮阳中石集团有限公司 | Novel coal feeder |
Also Published As
| Publication number | Publication date |
|---|---|
| CN103600938A (en) | 2014-02-26 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN103600938B (en) | Automatic coal dredging device for raw coal conveying system in thermal power plant | |
| CN203571779U (en) | Automatic coal loading device for drier | |
| CN105773834A (en) | Ceramic raw material independent-grinding centralized preparation technique and device | |
| CN205721339U (en) | A kind of industrial fluidized bed boiler automation control system | |
| CN106006035A (en) | Pneumatic calcium hydroxide conveying system | |
| CN206488272U (en) | A kind of continual and steady coal feeder in stokehold | |
| CN207065614U (en) | A kind of fuel delivery means for Production of Ceramics | |
| CN206648022U (en) | A kind of fluidized bed furnace | |
| CN104085625A (en) | Full-automatic coal bunker water cannon dredging device | |
| CN205652841U (en) | Intelligent feeding management system is carried to strength powder | |
| CN202149494U (en) | Co-combustion device of sludge | |
| CN204154090U (en) | brown coal drying device | |
| CN202770120U (en) | Coal slime powder burn-back furnace combustion apparatus | |
| CN205014392U (en) | Take air -cooled slag extractor of doing of air conveying system | |
| CN105442415B (en) | A kind of vertical drying tower and asphalt mixing plant | |
| CN112849794A (en) | Coal bunker prevents chute blockage device | |
| CN105180185A (en) | Air-cooled dry slag extractor with pneumatic transmission system and control method of air-cooled dry slag extractor | |
| CN113834299B (en) | Material drying system and control method thereof | |
| CN207169823U (en) | A kind of pneumatic breaking sifter | |
| CN103979230A (en) | High pressure steam hopper dredging device | |
| CN209127645U (en) | Tap water concave convex rod combined filtration sand high temperature discharging cooling device | |
| CN205619362U (en) | Chaff boiler oil gravity system device | |
| CN206927271U (en) | The Anti-blocking structure of Industrial Boiler electric precipitation pneumatic ash transmitting system | |
| KR20110030115A (en) | Choking preventing device for coal feeder and choking preventing method using this | |
| CN108571744B (en) | Intermittent slag discharging control system and method capable of preventing dust emission for boiler |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C06 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant | ||
| CP01 | Change in the name or title of a patent holder |
Address after: 050031 No. 6 Jianbei Street, Chang'an District, Shijiazhuang City, Hebei Province Patentee after: China Electric Power Construction Group Hebei electric survey and Design Research Institute Co., Ltd. Address before: 050031 No. 6 Jianbei Street, Chang'an District, Shijiazhuang City, Hebei Province Patentee before: Hebei Province Power Surveying Design & Research Institute |
|
| CP01 | Change in the name or title of a patent holder |