Technical Comparison Between Guodian Futong Steel Belt Conveyor and Chain Conveyor -REV1

Beijing Guodian Futong Science & Technology Development Co.,Ltd | China Electric Power Research Institute

: ABP 6-13 Building, No.188 Nansihuan Xi Road, Fengtai District, Beijing China 100070

: +86 10 51968383 | : +86 10 58387676 : http://www.epri.sgcc.com.cn/gdft

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Technical comparison between Steel belt conveyor and Chain (steel plate) conveyor

Item Steel belt conveyor Chain (steel plate) conveyor

1.Technical background Research and development by Guodian Futong:

� In 1997, Sanhe Power plant introduced steel belt dry bottom ash handling

systems for 2×350MW units as an experimental project. But the high cost of this

imported system and spare parts as well as clinker problem in Changchun Thermal

Power Plant strongly impeded the promotion of this new technology.

� In 2000, China National Power Company listed The Research on the Steel Belt Dry

Bottom Ash Handling System and its Key Components for Coal Fired Boilers as the key

technology project of the State Power Corporation with the project No. KJ00-02-15,

which is aimed to fill up the gap of domestic dry bottom ash handling system, to

imporve the technology, substitute traditional wet ash handling system.

� Project team conducted research and test on the key technology.

� Developed dry bottom ash handling technology with independent intellectual

property rights and has been awarded national patent.

� In May, 2002, steel belt conveyor dry bottom ash handling system passed the

technical identification by National Power Company.

Steel belt conveyors has been in operation in more than 200 units worldwide since

1986 with sable and safe system. It is the most advanced and mature technology at

present.

Futong steel belt conveyor dry bottom ash handling system has been awarded 15

patents, including 4 international patents from Australia and India. And its new

technology was applied for the latest international patents in Russia, Australia,

America, Vietnam and India through PCT in 2010.

Chain (steel plate) conveyor: Firstly invented by Japan's Kawasaki Heavy Industries Ltd.

After the application in small units, potential dangers exist. As a result, it is

immature technology with no industrial applications.




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2. Difference on key

components of the

conveyor

Key component of steel

belt conveyor – structure

and connection of high

temperature resistance

super steel belt are

shown in the figure:

The super belt is formed

of heat resistance,

wearing resistance

stainless steel mesh, and

overlapped carrying pan

of steel belt. Each

overlapped carrying pan looks like inclined ladder and fixed together by stainless steel

bolt and lock bar.

Features:

A: Due to the flexible component steel belt mesh, the relatively tightness between

Key component of Chain (steel plate) conveyor

– chain structure and connection are sown in

the figure:

Connection between the chain plate and chain is

connected by many connecting pins (shown as

the figure below). Adjacent chain plate speads

and composes conveying path.

Connecting pin




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carrying pan can be effectively guaranteed by reasonable pressing force (Note: the

process can ensure pressure by nail electric welding) and overlapping arrangement of

carrying pan, so as to prevent leakage of fine ash onto the lower section. Some fine

ash accumulated on the lower part because of cooling air, it can be effectively

conveyed to discharge outlet by fine ash cleaning chain under the super steel belt.

B: When super belt conveys bottom ash, bottom ash can be flatly spread on the steel

belt, whose effective width is 1.2m. The heat exchange surface area between the

cooling air and bottom ash is large so the cooling effect is googd. The maximum

capacity of the steel belt conveyor can reach 100t/h with strong capability to adapt

the load changes of boilers.

C: Impact bars for large clinker can effectively avoid direct impact of the large clinker

onto the super steel belt. And because of the overlapping arrangement of the carrying

pan up on the steel belt, as well as the large number of carrying idlers across the

width of steel belt under the belt, the direct impact from the bottom ash to the mesh

is effectively avoided, so as to prolong the service life of the steel belt.

D: Due to the line contact between adjacent carrying pans, the carrying pan can rotate

by the axis of that through cylinder, so as to reduce additional resistance. In addition,

friction between the super steel belt mesh and cylinder can transmit driving force. It is

the surface contact between the steel belt mesh and cylinder. As a result, the

A: Connection between the chain plate and the chain is hard-wired. Fine slag is easy to leak

through the gap between adjacent chain plates. Although installed the below fine ash clean

plate, it is difficult for the clean plates to scrape bottom ash from the tail of the conveyor to

the upper ash channel, so as to cause a large accumulation of fine ash and serious wear and

tear of the tail curved plate and cleaning plate.

Tail of conveyor and Curved cleaning plate

A: The Chain (steel plate) conveyor is composed of several channels. The height of the

scrapper is only 200mm and the volume of each trough is the same. As a result, the capacity

of this system is limited and the capability to adapt load change is poor.




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adhesion is strong while the wear is small.

Super steel belt

E: The special structure of steel belt can have free expansion to any direction in hot

condition, and free draw back in cold condition, without potential dangers such as

chain break. It will not reduce efficiency of the boiler or cause boiler shutdown.

And it can adapt to any working condition of boilers.

Super steel belt conveyor

F: The steel belt of the conveyor is supported by many carrying idlers across the width

of the steel belt. In the condition of high bottom ash rate, the load is distributed

evenly across the width and length of the conveyor, so the super steel belt is not

easily deformed.

Ash trough

A: When the steel plate (chain) conveyor is in operation, bottom

ash accumulates in each ash trough. This conveyor is like bucket

chain conveyor, with poor cooling effect.

B: This steel plate (chain) conveyor is the modified product of

traditional scrapper chain conveyor. Using chain drive, it can be

avoid chain deformation in long term hot operation condition.

The impact of large clinker, as well as the changes of center

Drive and return Sprockets

distance of the chain caused by uneven accumulation of the total expansion of both sides,

may cause chain jump and jam, and other accidents. In the high rate of bottom ash

condition (ash rate ≥ 5t/h), the drive chain may suddenly break, causing serious boiler

shutdown accident.




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Carrying idler of super steel belt

G: Guaranteed service life of steel belt is longer than 55000 hours. Based on domestic

and international project applications, the average service life of the super steel belt is

more than 10 years.

Chain break after plastic deformation Sudden break of chain

E: Chain plates are supported by small carrying idlers on both sides. In the condition of high

bottom ash rate, they are easily deformed.

Carrying idlers at both side of chain plate Figture of carrying idlers at both side

F: For steel plate (chain) conveyor, there are only two 600MW units operation projects.

From October 2008, chain plates block accidents happened six times and the chain plates

have been changed. Other two 300MW steel plate (chain) conveyors has changed the whole

set of chain plate since 2008. It is hard to ensure safe and stable operation.

3. Design of clinker The clinker crusher is integral cast structure: The shutting door is inserted structure:




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crusher A: The clinker crusher is composed of impact bars, pre-crushing bottom door, shell,

driving hydraulic cylinder, monitor system, hydraulic power pack and piping. The key

hydraulic components, such as oil pump and adjusting valves, are imported ones.

Hydraulic pre-crushing bottom doors (clinker crusher)

B: The body of clinker crusher is made of high temperature resistance, abrasion and

wear resistance material, can be used as shutting door and crusher. It designed to be

free maintenance structure with 30-year service life.

C: The crushing teeth of clinker crusher use hydraulic drive. It can flexible open and

close as the shutting door. And it can effectively pre-cool and pre-crusher clinkers.

Clinkers, large than 200mm, fall onto the impact bars firstly to be pre-cooled. Then

they can be crushed by tooth-like horizontal moved extrusion heads, then conveyed

by ash conveyor. The impact bars can withstand the impact of 2-ton clinker falling

A: This structure did pass practical application verification.

Inserted shutting gate




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within 40m without deformation and damage.

D: The open and close of clinker crusher is horizontal movement. Vertical force is born

by the immobile impact bars. The shutting door is not forced and will never open

automatically even if the cylinder does not work properly.

E: The falling and crushing process can be monitored by camera system. When the

extrusion heads closed, they are used to open and close ash hopper.

Video camera detection online

F: Clinker crusher is evaluated by projects applications (more than 9 years’ operation)

to be safe and reliable.

G: Clinker crusher is Futong’s patented technology and owns independent intellectual

property rights, with national patent No. ZL01200943.1 and Australian patent No.

2006100112.

Shutting gate installation site

A: Does not own independent intellectual property right.




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4. Features of the

structure of ash conveyor

Section structure of steel belt conveyor:

1.upper cover of conveyor 2. Ash guidance plate 3. Super steel belt 4. Guidance idlers

to prevent line deflection of carrying layer of steel belt 5. Carrying idlers of steel belt

6. Assistant air inlet on the lateral side of conveyor (check type) 7. Guidance idlers to

prevent line deflection of return layer of steel belt 8. Carrying idlers of return layer 9.

Cleaning chain supporting wheel 10. Fine ash clean scrapper

Features:

A: There are two layers of the conveyor, the upper on be super steel belt and the

Section structure of steel plate (chain) conveyor:

The fundamental problem of steel plate (chain) conveyor is sourced from its

side-double-chain drive mode, which shortages cannot overcome by itself.

A: The steel plate (chain) conveyor is one layer arrangement, which means the chain and

chain plate (ash trough) combined. It does not have misalignment adjusting device. The

misalignment caused by large clinker impact or uneven heat expansion cannot be adjusted.




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lower one be fine ash cleaning chain.

Section structure of steel belt conveyor

B: Ash guidance plate is above the steel belt to lead the ash onto the whole width of

steel belt. It can improve the cooling effect. And the guide plate is sealed under the

shell and isolated from dust which can ensure clean environment, also forms cooling

wind flow channel.

C. Bearing blocks are designed at the outside of shell. Carrying idlers, return idlers and

other rotation parts are dust proof sealed on the lateral plate of shell. Bearings work

in low temperature, dust-free environment to ensure reliable operation.

D. All bearing blocks, carrying idlers and return idlers can be overhauled and replaced

outside the shell.

Section structure of steel plate (chain) conveyor

B: In the operation of steel plate conveyor, the temperature of chain plate will reach more

than 300 ℃. The horizontal expansion amount will more than 5mm (usually, the expansion

coefficient for steel 1mm/m. 100 ). ℃ The space between chains will increase. When the

head wheel engages, vertical chain link will rub drive wheels ring trough, which cause extra

wear of the chain.

C: Because of the falling down of the bottom ash, the materials accumulated on the chain

plate are not even, which may cause heat unevenness of two sides chains and cause

difference heat expansion. Meanwhile, when head wheel engages, two sides horizontal

chain links are asynchronous, which may cause incline of the chain plate relative to the drive

shaft and cause extra wear of the chain.

D: Double-chain drive depends on stress of two chains. If uneven wear happens, or other

factors cause one of them strength reduction or damage, the security of the system is

reduced greatly.

E: Due to principle of double chain drive is meshing transmission mode, it has its own

problems. The uneven wear and different speeds may affect safety operation and service




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Appearance of steel belt conveyor

life. In the high temperature and high dust condition, it will not ensure 55000 hours service

life.

For the steel belt conveyor, using the basic principle of belt drive, the above problems do

not exist. The key component of dry bottom ash handling system is ash conveyor, which

safety and stable operation can ensure normal operation of the boiler.

Appearance of steel plate (chain) conveyor

5.Performance

parameters

The guaranteed service life of steel belt is longer than requirement in bidding

document, which requires that service life of mesh is longer than 50000h. All data are

based on theoretical calculation and project application.

Steel plate conveyor cannot reach the requirement of 50000h service life. Even if the

manufacturer promises, the data is short of supports by theory and practical application.




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6. Cooling technology of

bottom ash

At present, steel belt conveyer is the most advanced cooling technology for bottom

ash in the field of air cooling bottom ash handling system. Market share is larger than

99%.

A: For domestic coal-fired units which have large bottom ash rate, Guodian Futong has

developed two new technologies and filed patents respectively. They are reviewed by

State Patent Office in January 2006 and registered international patents. The patent

number 200610011273.1 and 200610011274.6 respectively. These two patented

technology is to solve the cooling problem in large clinker condition. The technology

has been applied in dry bottom ash handing system of # 1, # 2 units in Huaneng

Shang’an power plant.

B: The patent technology can effectively deal with large bottom ash rate (change of

the coal quality) in 1000MW units and can support safety and stable operation.

The bottom ash cooling technology exists insurmountable faults, and China domestic power

groups rarely use it.

7.Manufacture

technology

In the tender, Guodian Futong has described its material selection, surface treatment,

quality inspection in detail. And there are more than 30 units manufacture references.

Ash conveyor is the key component and Guodian Futong controls its quality by the

following measures.

A: Material selection: shell of conveyor heavy-duty H section steel for the skeleton.

Carrying idlers are made from thick-walled seamless steel pipe. Conveying mesh is

manufactured by imported ultra-low carbon stainless steel. And key components,

such as cylinder and its shaft, are conducted non-destructive ultrasound test.

B: Control of components: components and self manufactured components are

strictly checked and timely complete the "FT-QR8-25 components inspection

record card”. And establish more than 100 inspection record card for key components.

Each component has a complete set of quality record after manufacture.

C: Part Assembly: Qualified components are assembled next. Assemble is conducted

in strict accordance with “FT-QRT-24b production process card” and the

No




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“TZ2005-01A technical requirements of steel belt conveyor factory assembly,

testing, commissioning and packaging”.

D: Operation and commissioning: after assemble the shell, steel belt and cleaning

chain should be installed based on practical length and angle of the project and

conduct 48 hours test, and then fill out the form TZ2005-01A steel belt conveyor

factory acceptance form. For oversized steel belt conveyor (extra length, width or

large capacity), it is required to do load test.

E: Delivery: Pass the test and qualified, fill out FT-QR8-26B steel belt conveyor factory

acceptance, and signed FT-QR7-28d product certification. Then do the equipment

disintegration, packaging and delivery.




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8. Practical application Until November 2010, reference of Guodian Futong’s dry bottom ash handling system

include 22 1000MW units, 88 600MW-660MW units, 63 300MW-350MW units and 36

200MW and below units. The longest reference is 9 years and 8 months. It is a

technology mature system which can meet the requirement of safety and reliability.

And its feature of energy-saving and environmental benefit is remarkable.

The number of reference projects of Guodian Futong’s bottom ash handling system

has reached 209 sets until now.

There are only 4 operation reference, 2 x300MW units (A plant) and 2x 600MW units (B

plant) and bottom ash rate is less than 2 t/h.

All ash troughs have been replaced in B plant within 2 years from 2008.

There were six times of blockage of chain plate in A plant and replaced steel ash trough from

October, 2008.

Connection pin out of ash trough

Damage of ash trough and much bottom ash accumulated at back side

9. Standardization A: Entrusted by national standards committee, Guodian Futong has completed the

compilation work of industry standard of air cooling steel belt conveyor (Dry bottom

ash handling system).

B: Entrusted by national standards committee, Guodian Futong is doing the

compilation work of industry standard of technical requirements of clinker crusher.

No

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Technical Comparison Between Guodian Futong Steel Belt Conveyor and Chain Conveyor -REV1