session03 pet-01.coal handling

7/29/2019 Session03 PET-01.Coal Handling

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Power Engineering and Training Services, Inc. （PET)

2011 Climate Change Action Clean Coal Technology International

Cooperation Project CCT Transfer Project Dispatch Technology

Interaction (USC Coal-fired Power Plant Operation Technology)

Coal Handling at Power Station



1

Copyright© Power Engineering and Training Services Co.,Inc. All rights reserved.

Table of contents

Sheet No.

1. Coal transporting systems and coal storage 3 ～ 6

2. Coal handling at Misumi Power Station 8 ～ 22

3. Coal blending 24 ～ 25



1. Coal transporting systems and coal storage methods



3


Coal transporting systems for thermal power stations

Import fromabroad

Exportingcountries

Australia

Indonesia

China

Russia

U.S.

Ocean-goingvessel

Ocean-goingvessel

Ocean-goingSU vessel

Coal center

Coal center

Coal transfer station

Domesticvessel

Domesticvessel

Domesticvessel

DomesticSU vessel

Coal berth

Large coal-fired PS

★First of all, I would like to explain how the coal is moved fromforeign countries to the power stations in J apan.

Around 1980, as the capacity of power generating units in J apan grew bigger, the production capacity of

domestic coal became rather limited. Against this background, J apan began to import coal from foreigncountries in consideration of the stability and economics of fuel supply. At present, J apan imports most of itscoal as fuel from Australia, Indonesia and other countries. The main type of coal is bituminous coal. Besides,we also burn a variety of coals including sub-bituminous, semi-anthracite and other coals. Together with thecoal for steel industry, J apan on the whole imports approximately 60% of its coal from Australia and 20%from Indonesia in one year from April 2009 to March 2010.

The picture here shows how J apanese power stations accept andtransport the coal imported from foreigncountries.

Large coal vessels of 100,000DWT (hold from 60,000 to 150,000DWT) are normally used in J apan totransport coal from abroad. Roughly, there are two ways to accept such large coal vessels. First in one way,if the power station has port facilities to allow large coal vessels to enter the port, the imported coal can bedirectly accepted into the quay of power station. The upper part in this picture indicates the case like that. Inthis case, the water at the berth of coal unloading pier needs to be at least -14m deep. Big unloadingfacilities are also required for unloading coal. At most of the newly-built power stations with large capacitiesper unit, this process is applied for coal handling.

In another way, at the coal-fired power stations with small-and-medium-sized capacities, the coal isunloaded from big coal vessels first and accepted into the coal center in J apan. (Such coal centers arenormally located on the premises of the iron mills where large amount of coal is consumed.) Then, the coalis transported from there by small domestic vessels to the nearby power stations. The middle part in thispicture indicates the case like this. In this case, small unloading facilities will be fine for coal handling.

At The Chugoku Electric Power Co., Inc. (CEPCO), a coal transfer station is set up to play the same roleas a coal center. It is helpful in improving the efficiency of logistics and streamlining the existing coalacceptance and storage facilities. This coal transfer center accepts most of the coal used by the coal-firedpower stations of CEPCO. Afterwards, the coal is transported to the nearby power stations by smalldomestic vessels. The lower part in this picture shows the case like that. Moreover, at this coal transferstation, coal unloaders are applied on the big coal vessels thattransport coal from abroad and the domesticcoal vessels that transport coal to power stations. In this way, the coal acceptance facilities at power stationscan thus be streamlined.

On the next page, I would like to give an introduction to the coal transfer station and domestic SU vessel.



4


Coal transfer station and self unloader collier

（Coal transferstation）

（Self unloader collier）

Coal storage capacity:

300,000t

Annual handling quantity:

Approx. 3 million tons

Coal incoming system: One

Coal outgoing system: Two

Model: 5,000DWT

Incoming

Outgoing

★Now let me give a brief introduction to the coal transfer station and self unloader collier.

(1) As for the coal transfer station, its coal storage capacity is 300,000 tons and its coal handlingquantity amounts to approximately three million tons. It consists of one coal incoming system and

two coal outgoing systems. Coal comes in by big SU coal vessels of 100,000 tons. Every day, thecoal goes out from this coal transfer station to four coal-fired power stations.

(2) Self unloader collier is of 5,000DWT model. It transports coal every day from this coaltransfer center which is about 150 to 200km far from the power stations.



5


Coal storage methods (1/2)

・Weather exerts no influence on operation at all.

・It is possible to operate both acceptance/discharge systems in a completely automatic manner.

・It will be difficult to discharge coal when bridge emerges in discharge system.

・Weather conditions for windbreak and the like hinder operation.

・Manned operation is required when discharger starts operation.

・Multiple brands of coal can be stocked, but stockout loss is big.Operability

・Ignition elimination and ventilation help prevent dust in silo from exploding.

・Keeping away from air may prevent spontaneous combustion.

・Oxygen in silo may be lacking.

・There is risk of coal dust explosion.

・Coal pile may break down when rain falls.

・There is risk of falling down from coal pile when handling temperature detector tube.Safety

・Dust occurs in silo, but the surrounding area is not environmentally contaminated.

・ Noise is the lowest.

・Windbreak and water sprinkler are needed to prevent coal pile from dust.

・Actions need to be taken to control water pollution arising from rainwater drainagetreatment equipment.

Environment

・Only small site area is needed.

・Strong support for ground is required.・Vast site area is needed.

・Able to counter unreasonable ground subsidenceSiting

Silo body, Bottom hopper,

Discharge tunnel,

Pile foundation (all over under silos)

Hopper at the bottom of silo (Concrete structure)

Pile foundation (all over under silos)

Underground tunnel for discharge conveyor

Land clearing for coal yard (ground improvement)

Underground piping for rainwater drainage

Rail ballast for stacker/discharger travelling

C i vi l

e n gi n e e r i n

g

Silo body (welded steel plate)

Concrete siloSteel plate siloWindproof fence (Steel structure with metal wires)Ar c h i -

t e c t ur e

Distributor (trimmer), plow feeder (travelling), belt conveyor,

Silo fire-prevention equipment (dust collector, temperature detector, gas detector, water sprinkler)

Bucket wheel type stacker/discharger,

Belt conveyor,

Water sprinkler, drainage system, wastewater treatment facility, fire hydrant,

temperature detector

M e c h a ni c a l

e q ui pm e n t C

om p o s i t i on

Contour

Silo coal storage modeOutdoor coal storage modeStorage mode

★In this table, we give a description about how J apanese coal-fired power stations generally storethe accepted coal.

Well, I would like to explain what is described in this table.



6


Coal storage methods (2/2)


・It is possible to operate both acceptance and discharge systems in a completely automatic manner.

・Multiple brands of coal can be stocked, but stockout loss is big.


・It is difficult to operate in a completely remote automatic manner.

・When multiple brands of coal are stocked, stockout loss is big.Operability

・The indoor space is so big that there is no risk of dust explosion.・The space in dome is so big that there is no risk of dust explosion.

・There is risk of falling down from coal pile when handling temperature detector tube.Safety

・Small amount of dust occurs indoors, but the surrounding area is not environmentally

contaminated.

・ Noise of indoor machines is low.

・Small amount of dust occurs indoors, but the surrounding area is not environmentally

contaminated.

・Small portion of sound of indoor machine operation spreads outdoors.Environment

・Strong foundation is required all over under slot bunker.・Strong foundation is required for peripheral and central part.Siting

Slot bunker (concrete structure)

Pile foundation (all over bunker)

Peripheral retaining wall

Coal storage floor, underground tunnel for discharge conveyor

Pile foundation (peripheral and central part)

C i vi l

e n gi n e e r i n g

Building (steel structure)Dome (steel structure with central column)Ar c h i -

T e c t ur e

Distributor (trimmer), plow feeder (travelling), belt conveyor

Silo fire-prevention equipment (dust collector, temperature detector, gas detector, sprinkler)

Stacker (rotating)

Discharger (Bucket chain)

Belt conveyor

Ventilator, fire hydrant,

temperature detector, dust collector

M e c h a ni c a l

e q ui pm e n t C

om p o s i t i on

Contour

Slot bunker coal storage modeDome coal storage modeStorage mode

★In the next, I would like to explain what is described in this table.



2. Coal handling at Misumi Power Station



8


(1) Location of Misumi Power Station

Yamaguchi

Hiroshima

Shimane

Okayama

Tottori

Misumi

Tokyo

MisumiKyoto

Indonesia

Jakarta

Misumi P/S

5300km

Now I would like to give an introduction to Misumi Power Station. It is about 5,300km towardnorth-northeast of J akarta. Misumi Power Station is located between Hamada City andMasuda City, facing the J apan Sea in the west of Shimane Prefecture.

In order to ensure the stable supply of electricity, the ChugokuElectric Power Co., Inc.(CEPCO) had planned the construction of Misumi Power Station as an essential coal-firedpower generation source for the first half of the 21st century. At Misumi Power Station, we hadbrought together an abundance of all the thermal power generation expertise that CEPCO hadaccumulated so far and brought in the latest technologies at that time.



9


North

Seawall

Seawall

West Seawall

Coal Berth

Ash Pond

Partition

East Seawall

Coal SiloBoiler House

Turbine House

FGD

Coal Conveyor

Outlet of Cooling

water

(2) Cover Shot of Misumi P/S

○ Output: 1 million kW

○ Operation started: June 25, 1998

○Thermal efficiency: 43% (Gross, HHV-based)

○ Steam condition: Temp. 600℃, Pressure 24.5MPa

○ Environmental facilities

・SOx control: Wet limestone-gypsum type FGD

system (Desulfurization efficiency: 90% or greater)

・NOx control: Two-stage combustion type, Low-

NOx burner, SCR system (Denitrification efficiency:

80% or greater)

・Soot & dust control: ESP (Precipitation

efficiency: 99% or greater)

The land for Misumi Power Station was located near the relatively gentle hills, so the land

development itself was not that hard. Meanwhile, most of the coastline is the eroded shorewith small entrances and exists that allow big coal vessels to enter directly.

Besides, the area of Misumi Power Station was sandwiched by two fishing harbors. (Show thelocation in the north of the picture.) In this area, the wind from northeast is strong in winter andthe seawall of ash pond is vulnerable to high waves. The area of Misumi Power Station is composed of the drilled hills (equivalent to 300,000m2)and waterfront landfill (equivalent to 390,000m2). The total area amounts to about 690,000m2.Next to the power station, an area of approximately 320,000m2 for ash pond (with an ashtreatment capacity of 5.6 million m3) has been reserved.

In the following, I will first mention about the output, start of operation, thermal efficiency,steam condition, and environmental facilities of Misumi Power Station. After that, I will refer todifferent facilities and give an introduction respectively to each of them.



10


Major Equipment (Steam generator)

Source: Abstracted fromCEPCO documentation

Type: Radiative reheat variable pressure

once-through boiler

Max Continuous Rate: 2,900t/h

Steam pressure and temperature:

SH outlet 25.4MPa/604degC

RH outlet 4.5MPa/602degC

Fuel: Coal, Light Oil as auxiliary fuel

- USC variable pressure once-through boiler is adopted for improvement

of efficiency and operability at middle load.

- Heavy Oil facility is excluded for simplification by adopting high

turndown pulverizer and lowering minimum load at coal firing without

oil.

-Split burners and furnace denitrification are incorporated to improve the

low-NOx combustion technology.

- Control by gas re-circulation and dampers is adopted for characteristic

of different steam temperature for various coals.

*Turndown ratio: Proportion of the rated fuel flow per burner to the

controllable minimum fuel flow. 《The bigger a burner is, the more freely

its fuel flow (load) can be adjusted.》

Here is a description of the main specifications of boiler (steam generator).

This boiler is a radiative reheat variable pressure once-through model. Its maximumcontinuous rate (MCR) is 2,900t/h. At this point, the overload in summertime is not taken into

account. However, the steam capacity is designed to satisfy the rated output even under thecondition that the boiler has deteriorated with time.

The pressure is designed as 25.4MPa at the superheater outlet and the temperature at 604degrees Celsius (℃). The pressure at the superheater inlet is 4.50MPa and the temperature is602 degrees Celsius (℃). Coal is used as the fuel and light oil as the auxiliary fuel.



11


Turbine/generator

Source: Abstracted from CEPCO documentation

Type: Horizontal revolving-field synchronous

generator

Output: primary generator 657,000kVA

secondary generator 474,000kVA

Cooling system

Stator water-cooled

Rotator hydrogen-cooled

Voltage: 22,000V

Power factor: 90% delay

Generator

Type: 2 shaft 4 flow exhaust reheat condenser

turbine (CCF-46")

Output: 1000MW

Steam pressure and temperature:

MSV inlet 24.5MPa/600degC

RSV inlet 4.50MPa/600degC

Rotation speed:

primary turbine 3600rpm

secondary turbine 1800rpm

Turbine

- Turbine inlet steam condition 24.5MPa/600degC is adopted for higher efficiency.

- Proven and reliable type of 2 shaft 4 flow exhaust reheat condenser is adopted.

- High pressure rotor is made of chrome-alloy developed for 600degC steam

- 4 valve type for governor, 2 valve type for intercept valve of large diameter

of 25 inch. Fewer valves-arranged provide maintainability.

- All of condenser tubes are made of titanium for corrosion resistance, anti suspended solids,

economic efficiency.

- The blade at final stage of low pressure turbine is sized 46 inch, developed for higher efficiency

and less loss in exhaust chamber by 3D flow design.

Here is a description of the main specifications of turbine and generator.

- Turbine inlet steam condition 24.5MPa/600degC is adopted for higher efficiency.- Proven and reliable type of 2 shaft 4 flow exhaust reheat condenser is adopted.

- High pressure rotor is made of twelve chrome-alloy developed for 600degC steam, soenough strength can be secured even under high temperature.

The lower part is the primary turbine. Its rotation speed is 3,600rpm. The upper part is thesecondary turbine, which rotation speed is 1,800rpm.



12


Coal acceptance and storage system

4,600ｔ/ｈ× 2Receiving

Conveyors

Type Continuous Bucket Chain

2,800ｔ/ｈ × 2

Coal

Unloader

Type Steel Silo of Square type

33,000ｔ × 12 chambers

Coal Storage

Silo

・Concrete Silos are popular for coal storage but Steel Silo was adopted for more storage capacity

per installation area, shortening of construction period, less cost and higher reliability

・Continuous unloaders of large capacity are adopted considering bad weather conditions in

winter. They can unload coal from 60,000 t c lass vessel in 1.5 day including approach and

departure time.

・Receiving conveyors, coal storage silo and supplying conveyors are automatically operated from

BOP control room.

Receiving conveyor

Recycle conveyor

Hereby, I would like to explain the main specifications of the coal acceptance and storagesystems.

Coal is mainly imported from Australia and is discharged by unloaders that are arrangedat dock on the premises of Misumi Power Station. In concern of the tough winter weatherconditions specific for the J apan Sea, two 2,800t/h continuous unloaders are available. The coal equivalent to the hold of one 60,000DWT coal vessel can be discharged inabout fifteen hours by unloaders. This is of the top unloading rate in J apan. (The spaceable to hold three unloaders is kept for future use.)

The unloaded coal is then stored in this coal storage silo.

Taking account of the dust initiated by monsoon (wind and snow) in winter and the sitearea of power station, angular centralized steel coal silos are applied in a form of indoorcoal storage.

Coal storage silos are installed on the shallow part of supporting rocks. The foundation isdirectly supported by rocks. At the same time, coal storage silos also function as barriers

against the noise on the border of power station site.Besides, one more conveyor system is installed for coal recirculation (recycle) in coal silodischarge system. On one side, It serves to protect the coal in coal storage silos fromnatural temperature rising. On the other side, it is used to convey coal between silos (forcoal relocation).

Due to tough weather conditions in winter, coal vessels might be prohibited to enter theport. Considering this, we have studied the receivable quantity (days) in winter todetermine the coal stock requirements for coal silos according to the data of previousclimatic and hydrographic conditions (for approximately ten years). Coal stockrequirement is about 400,000 tons in the process of commercial operation of Unit One at1,000MW.



13


Outline of coal unloading, storing, and transporting systems

NCoal bunker

Unloader

Unloader

Scale

Discharger

discharge

conveyor

Stockout conveyor

Slant conveyor

Scale

Iron separator Iron separator Acceptance

conveyor

Scale

Metal

detector

Discharge conveyor

SilosStacker

Recycling conveyor

(Bottom)

(Top)

2 systems900t/hCoal sending conveyor

1 conveyor 900t/hCoal recirculation (recycle)

conveyor

9 conveyors900t/hCoal discharge conveyor

9 units900t/hCoal discharger

12 silos33,000t/siloCoal silo

3 units4,600t/hCoal stacker

3 conveyors4,600t/hCoal stockout conveyor

2 systems4,600t/hCoal acceptance conveyor

2 units2,800t/hUnloader

QuantityCapacityFacility

Drive room

★ Here is the overall system diagram of coal unloading, storing, and transporting facilities atMisumi Power Station.

In concern of the tough winter weather conditions specific for the J apan Sea, the coal equivalent to

the hold of one 60,000DWT coal vessel is discharged by two 2,800t/h continuous unloaders whichare the largest in J apan. There are two conveyor systems. One is for coal acceptance and anotheris for coal sending. In consideration of the environment around belt conveyors such as dust, noiseand so on, gallery type in enclosed structure is adopted for conveyor. (When conveyor doesnt fitgallery type, the plates to protect coal from falling are set under the belt and the windproof platesare built at the side of frame. In this way, the systems can be free from the scattering of fallingcoal.)

For the coal acceptance conveyor systems, the route from the dock where coal is unloaded to coalstorage silos (hereinafter referred to as coal silos or silos ) is made the shortest. Coal isaccepted from unloaders and sent to coal silos. In principle, coal is sent to two silos of differentrows simultaneously. To do this, two acceptance conveyors are frequently available for use.

In the midst of acceptance system, magnet separator (electromagnetic suspended type) is fixed at

acceptance conveyor transfer section to remove foreign substances in coal. In addition, coalweighing device (load cell belt scale) and coal sampling device (belt sampler) are set atacceptance conveyor systems (4,600t/h× 2 units).

The coal sending system conveyors are compactly arranged by using slant conveyors which arepartly in the form of dual belts.

In the following, I would like to explain the specifications of these facilities one by one. (Let megive a brief description about them.)



14


Operating methods of coal unloading, storing, and transporting systems

Approx. 400,000 tonsCoal storage capacity

Water washing belt cleaning equipment and coal water treatment system are employed.Working condition

Soundproof rollers are applied. Noise control

Unloader & conveyor: Sealed type (Gallery is installed.)

Joint tower: Dry-type dust collector is installed.Dust control

Environmental

protection

Coal storing and transporting systems (from unloader to coal silo and then bunker) are operated

automatically for start-up and shut-down with the touch of a button.

However, coal unloaders are operated by operators in a semi-automatic way.

Automation

Coal is sent every day.Coal sending time: From AM8:00 to PM21:00 (including the inspection at the beginning and end of work

shift).

Working condition

Coal equivalent to usage is sent to bunkers. Two conveyors are available.

Coal is blended on the belts at the exit of the coal silos.Coal sending requirement

9,000T per dayCoal sent to boiler

Coal

sending

Possible time for coal unloading: From AM6:00 to PM21:00

Time of coal unloading: From AM8:00 to PM21:00 (Coal is also unloaded on Saturdays and Sundays.)

Unloading condition: Wave height smaller than 0.7m and wind speed lower than 16m/s in front of the pier

Working condition

Berth water depth: -14m

Time for entering port: From sunrise until sunset (at port gateway)

Condition for entering port: Wave height smaller than 1.3m and wind speed lower than 10m/s (maximum

wind speed 15m/s) outside the harbor

Port condition

Basically 60,000DWT class and specifically 80,000DWT class with special widthTransportation

Approx. 2.5 million tonsAnnual unloading quantity

Coal

unloading

Contents as designed Subjects

★ Now let me explain in detail the operating methods of coal unloading, storing, and transportingsystems at Misumi Power Station.



15


Coal unloader and coal acceptance system to the coal silo

Scale accuracy:±0.5%Load cell belt scaleAcceptance scale

Two conveyors are installed to preparefor the case that the belt of one conveyor is damaged or so.

Sealed belt,gallery (elevated part)

Coal acceptanceconveyor

Sealed belts are used at stacker gate.Travelling tripper Coal stacker

Truss gutter Coal stockoutconveyor

For back-check in business transactionsFull-range belt sampler Coal sampling

system

In concern of the tough conditions for coal vessels to enter the port in winter,adding one more unloader in future has been taken into account.

Bucket elevator continuous

Coal unloader

ApplicationModelFacility

★ (First of all), I will give a description of the coal unloading system diagram and explain the name andmodel of each facility.

Next, I would like to tell about the capacity and quantity of coal unloaders and explain why this specificmodel has been selected. Also, I will mention about coal acceptance conveyor.

(1) Capacity (Unloader capacity): 2,800t/h/per unitIn view of the limited conditions for coal vessels to enter the port due to tough monsoon in winter featured bythe Japan Sea, we unload the coal in half a day.

(2) Quantity: 2 units

Even if two unloaders are used in the case of Unit One commercial operation, berth occupation rateincreases to some extent, but there is no influence on coal stock variations inside coal silos and days ondemurrage for coal vessels outside the port.

(3) Type: Bucket elevator continuous type

The bucket chain type excelled in the aspects of automation, operability at the time coal is scooped out frombottom (dependency on bulldozer operation), responsiveness to the upward and downward movement of coal vessel in line with wave height, and so on. Therefore, bucket chain continuous unloades have beenadopted.

(4) Capacity (Conveyor carrying capacity) : 4,600t/h per system× 2 systemsBelt widths for general-purpose products are used (2,400mm or less in maximum). In case that the belt of one conveyor is damaged or so, coal can still be discharged at 50% capacity to offset the extension of unloading time. Therefore, two conveyors have been installed.



16


Coal storage silo

Steel-framed structure (To hold acceptance

equipment)Roof truss

Steel plate welded structure (Trunk body of silo)Upper

structure

Steel-framed reinforced concreteLower

structure

Spread foundation (Constructed on rock bed)Foundation

Structure

12 silos (16 silos in future) Number of silos

Approx. 31m in length×31m in width×46.5mIndividual size

Approx. 139m in length×105m in

width×95.5mOverall size

★ In the following, I will give a description of the coal silos for coal storage.

(1) Coal storage capacity: 396,000 tons (33,000 tons/per silo×12 silos). The overall size isapproximately 139m in length×105m in width×95.5m.

When planning for facilities construction of Misumi Power Station, 60,000DWT size is designed asthe main type of vessel for accepting coal. (In fact, mainly an 80,000DWT bulk coal carrier widerthan 60,000DWT size coal vessel chartered by Chugoku Electric Power enters the port ever sinceUnit One started its commercial operation.)

Therefore, one silo is set for one type of coal in principle for managing coal silos. Under thisprecondition, the capacity of one coal silo has been determined to ensure that coal of one60,000DWT size vessel could be stocked in two silos and each silo should be capable of holding33,000 tons.

(2) Type: Angular centralized steel coal silo

Angular centralized steel coal silos are developed by Chugoku Electric Power in joint effort withthe manufacturers. Compared to the conventional cylindrical concrete ones, they are superior in

the aspects of space factors (site area), construction period, construction process, quality control,cost and so on. Besides, angular centralized coal silos have drastic barrier effects against thenoise of power station. Consequently, when they are built near the border of power station site, thenoise from power station to neighborhood can thus be mitigated.

(3) Size of coal silo: 31mL × 31mB× 59.5mH per silo



17


Breakdown of coal stock requirement

400,000 tonsCoal stock requirement

Suppose that the biggest supplier,

Australia incur a delay in loading

Prepared for coal

supply disruptions

To make up for the coal deficit due to

bad weather in winter

Prepared for

climatic/hydrographic

conditionsStorage for

emergency

Space for loading optionsPrepared for

variations in cargo

carrying capacity

To deal with variations of shipping

schedules

Running space

Equivalent to the capacity of one vessel

with the biggest size

Acceptance space

Storage for

operation

ReferenceItem

★ This table here describes the breakdown of coal stock requirement.

In consideration of the tough hydrographic and climatic conditions in winter, maximum cargocarrying capacity of coal vessel, unloading simulation, and other factors that may influence, coal

stock requirement for Unit One of Misumi Power Station at the time of 1,000MW has beendesigned as approximately 400,000 tons.

However, there are preconditions that count stated as below.

・Coal consumption: 9,000t/per day

・Storage mode: Silo type (One brand of coal is stocked in one silo. Coal is discharged in aprinciple of first-in first-out.)

・Coal vessel: 60,000DWT size (Including 80,000DWT size bulk coal carrier chartered byChugoku Electric Power)

・Others: Stockpile coal in the space for acceptance before winter comes. Meanwhile, keep thislevel to prepare for the unpredictable bad weather.



18


Shape of the discharger hopper

Discharger traveling

rail

Discharger-side operation

panel

Cable duct

Discharger

Housing lining

Discharge

conveyor

Load dispatching control

system for the

discharger

Drainage canal

Hopper

Discharger

rotary wheel

★ This figure on this slide shows the simplified shape of the discharge part. Hereby I would like toexplain the structure of this discharge part.

The only coal discharge outlet of the coal silo is the hopper atthe bottom. The required factor forstable operation is to select the shape of coal discharge outletthat allows natural discharge due togravity.

The combination of the long-slit structure and the traveling discharger adopted in the coal silo inMisumi Power Station has a simple structure. It also has been adopted in many large silos, and itsreliability is high.

There is no record of blockage in the actual operations in Misumi Power Station, whichdemonstrates the appropriateness of the facility and specifications.



19


Fire extinguishing system for coal silos

Indoor fire hydrant system

(Discharge conveyor paths and

discharger inspection spaces)

Discharge conveyor

space

Lower Part of

Coal Silo

Water spray extinguishing

system

(Upper part of the stored coal)

Stored coal

Water spray extinguishing

system

Upper surface of the

acceptance conveyor

belt

Upper surface of the

seal belt of the coal

feeding part of the

stacker

Inside Coal Silo

Indoor fire hydrant systemAcceptance conveyor

space

Upper Part of

Coal Silo

Fire Extinguishing SystemTarget of Fire

ExtinguishingTarget Area

Auto valve unit for water sprinkling

Spray head

Indoor fire hydrant

Acceptance conveyor

Discharge conveyor space

For extinguishing

Wastewater for

testing

For extinguishing

Indoor fire hydrant

Nozzle for dust prevention and

water sprinkling

★ This figure here shows the fire extinguishing system for the coal silos.

The coal for storage is designated as a combustible material under Fire Service Act of J apan. Therefore, in accordance with Fire Service Act of J apan, fire extinguishing system for coal silo hasbeen constructed in which indoor hydrants and water spray nozzles are set in the following way.

(1) Water spray extinguishing system is installed in the part of tripper conveyor belts in the upperpart of coal silos. In addition, indoor hydrants are installed indoors in the upper part of coal silos.

(2) Water spray system is available for the surface of coal under storage.

a. Indoor hydrants which are installed in the room for tripper conveyors in the upper part of coalsilos are available to be put into action.

b. Remote automatic valves are fixed to water spray fire extinguishing system for the coal surfacein the upper part of coal silos and for the part of tripper conveyor belts. They are operated from thecontrol room for outdoor equipment.

c. Indoor fire hydrants are even able to deal with the room for discharge conveyor belts in theupper part of coal silos.

d. Besides that automatic fire alarms and small fire extinguishers are installed.



20


Coal silo disaster prevention monitoring instruments

3 units30kW1,000m3/minExhaust fan

3 units30kW500m3/minAir supply fan at the bottom of

the silo

3 untis22kW1,000m3/min

Air supply fan in the corridor at

the sheds attached to both sides of

the silo

3 units315kW2,100m3 /minCoal silo ventilation fan

QuantityCapacityAir flowVentilation facility

(Ventilation equipment inside coal silos)

Monitoring ITV

Level gauge

CO gauge

O2 gauge

CH4 gauge

Thermometer

Thermometer

at the top part

of the hopper

Thermometer

inside the coal

storage tank

Dust collecting

ventilation system

Fire hydrant

sprinkling

system

Expected fires in the coal silo (indoor storage method) include fire from natural heating of coal,oxygen deficit due to combustible gas released from coal, and explosion due to fire or coal dust.

Misumi Power Station is implementing the following measures to prevent such disasters andensuring the safety of the coal silo.

The figure shows the arrangement of coal silo disaster prevention monitoring instruments.(a) Methane gas (CH4) concentration gauge

In consideration to gas generation from oxidation and heating of coal inside the coal silo, methanegas detectors are installed on the upper part of the coal silo where exhaust gas circulationaccumulates, and continuous monitoring is implemented.

(b) Carbon monoxide (CO) concentration gauge

In consideration of the generation of carbon monoxide gas from low-temperature oxidation insidethe coal silo, carbon monoxide gas detectors are installed near the inspection corridors andcontinuous monitoring is implemented.

(c) Oxygen (O2) concentration gauge

In consideration of the decrease in oxygen gas concentration from the oxidation of coal and failureand suspension of ventilation systems, oxygen gas detectors are installed inside the coal silostorage tank to implement continuous monitoring in order to prevent accidents from oxygen

depletion during patrol and maintenance work at the conveyor routes. In the initial phase of spontaneous combustion of stacked coal, carbon monoxide gas is released while the oxygen gasconcentration changes; thus, oxygen gas detectors are installed inside the coal silo storage tanksto detect spontaneous combustion, and continuous monitoring is implemented.

(d) Air thermometer

Since no one is present inside the coal silo storage tanks during normal operation, temperaturedetectors are installed for early detection of heating inside the coal silo storage tanks, andcontinuous monitoring is implemented.

(e) Coal thermometer inside the coal silo storage tanks

The most effective monitoring method to prevent spontaneous combustion is to directly measureinside a coal storage tank.

Wired detectors are used inside the coal silo storage tank to implement continuous monitoring.

(f) Monitoring ITV

ITV cameras are installed in some parts inside the coal silo to enable monitoring from the outsidefacility control room. The lights installed in the ITV monitoring areas turn on in conjunction with thecamera.



21


Coal discharge

Discharge wheel

Discharge wheel driving

system

Driving system for traveling

Discharge conveyor

・Discharge capacity: 90 to 900 t/h

・ Number of installed units: 12 units

・Model: Double rotation wheel

travelling model

・Traveling distance: About 150m

・Traveling speed: Dual-speed

switching method with two speed

This discharger can travel for about 150 meters on the track along the discharge conveyor inside thebasement culvert of the coal silo, covering 1 to 4 coal silo storage tanks on lines A, B, and C in the coal silo.It is a dual-speed switching method with two traveling speed.

The shape of the discharge wheel is curved, which efficiently digs the coal that receives vertical pressure onthe slit and hopper shelf.

Scraped coal is transferred to the boiler coal bunker via the discharge conveyor located directly below thedischarger.

During regular operation, the discharger travels at a constant speed and automatically reverses the travelingdirection at both ends of the coal discharge area (zone). The discharger stops for a certain period of timewhile reversing the direction of the travel. The discharger is also equipped with a traveling position detector.

The regular discharge operation mode interlocks the discharge wheels and the downstream conveyor of thedischarger, and the discharger almost evenly discharges coal by travelling both ways inside the limiteddischarge traveling space.

At the start of a discharger operation, the discharge is controlled by setting the target value of the dischargewheel rotation speed for the designated discharge amount.

After a certain period of time elapses from the discharge start, the weighing signal of the weigher and thedesignated discharge amount are compared and the increase or decrease is adjusted, performing automatic

control of the discharge amount so that the discharge amount becomes almost constant (quantitativedischarge).

The figure shows the system diagram of the quantitative discharge automated control system of thedischarger.

Let me say a few words about this system diagram.



3. Coal blending



23


Coal blending method

Low accuracy

Once coal blending ratio is specified,

coal can be blended automatically

with high accuracy.

It is possible to blend coal automatically with high

accuracy.Accuracy

No specific facility is required.

Equipment is more complicated. Coal

blending hopper and discharge scale

are needed.

It is workable only if discharger is available.

Equipment &

maintenance

cost

The machine like a bulldozer is

used to drop down the coal that is

going to be blended into the

underground hopper. Coal is

blended while the coal is being

carried from that hoper to the belt

conveyor under the hopper.

The coal to be blended is discharged

one brand by another.

The coal is stored in a number of

hoppers at the plant. The required

amount of coal is paid out by

quantitative feeders which are

installed under the hoppers. Then,different brands of coal are blended

on the belt conveyors.

When coal is being blended, multiple dischargers for

different coal silos will be operated simultaneously. In this

regard, coal blending ratio is freely designed, ranging from

10% to 90% by regulating the quantity of different

dischargers. Coal is blended on the belts of underground

conveyors beside coal silos (on the west side). In this way,

multiple types of coal can be blended for operation.

Blending

method

Facility

Coal blending by bulldozer Coal blending by hopper Coal blending on conveyor belts (Misumi P/S)

払出コンベア

払出機

コンベア

混炭ホッパ混炭ホッパ

払出

計量器

クラッシャ

コンベア

Underground hopper

地下ホッパ

コンベア

★(1) Coal blending by bulldozer

The machine like a bulldozer is used to drop down the coal that is going to be blended into the undergroundhopper. Coal is blended while the coal is being carried from that hoper to the belt conveyor under the hopper.

Accuracy of coal blending is rather low, but no specific facility is required. In this sense, sometimes it mayafter all be employed as a simple approach for blending.

(2) Coal blending by hopper

The coal to be blended is discharged one brand by another. The coal is stored in a number of hoppers at theplant. The required amount of coal is paid out by quantitative feeders which are installed under the hoppers.

Then, different brands of coal are blended on the belt conveyors. In this way, once coal blending ratio isspecified, coal can be blended automatically with high accuracy. However, as the equipment is morecomplicated, the equipment and maintenance cost grow bigger. This can be regarded as the weak point of the coal blending by hopper.

(3) Coal blending on the conveyor belts

The appropriate amount of coal is scooped out one type by another from the coal storage silos according tothe quality and brand of the coal by more than two dischargers. Different types of coal get together and areblended on the belt conveyors in the lower part. Compared with blending coal by hopper, this method ismore complicated in terms of control. However, on the whole, the equipment and maintenance cost is lowerand automatic control also makes operation easier.

As for steel coal silos, travelling plow feeder is installed to function as coal discharger. Therefore, coalblending hopper has not been used for the following reasons. In other words, coal is blended on belts bysimultaneously operating several units according to the designedcapability of discharger.



24


Pre-examination of coal properties

Coal ash elution

Exhaust gas

Wastewater treatmentAsh characteristics

Ash wear

EP

Temp. rise

Mill

Firing

Slagging

Combustibility

Handling

FGD

Items to be pre-examined

％Basicity, Acidity, OthersAsh analysis

％50mm or lees, 2mm or lessParticle size

℃Fusion point

℃Melting point

℃Initial deformation point

Fusion temp.of ash

％Arsenic

％Selenium

％Fluorine

％Boron

％Chlorine

％Sulfur

％ Nitrogen

％Oxygen

％Hydrogen

％Carbon

Ultimateanalysis

－H G I

－Fuel ratio

％Total sulfur

％％

％％

％％

％％

Proximateanalysis

％Total moisture

％Moisture

kJ/kgHeating value

％Coal blending ratio

Items of coal properties to be pre-examined

Data of Coal GradeDifferent types of coal have different combustion

characteristics. Therefore, in line with steam generator

combustion management which covers NOx, unburnedmatter in ash, slagging, precipitator performance, and so on,

it is of critical i mportance to blend multiple types of coal for

achieving better coal properties with higher combustibility.

Different types of coal have different combustion characteristics. Therefore, in line with boiler

combustion management which covers NOx, unburned matter in ash, slagging, precipitator

performance, and so on, it is of critical importance to blend multiple types of coal for achievingbetter coal properties with higher combustibility.

When designing coal blending ratio, testing of coal properties after blending is performed on the

basis of the data of coal grade, which include the information obtained in advance such as heating

value, moisture, total moisture, proximate analysis results, ultimate analysis results, ash

composition and so on. Coal blending ratio is designed approximately to ensure that the properties

of blended coal are within the permission of coal properties designed for boiler.

The table shows the data of coal grade applicable for testing coal properties. And The other table

describes the items to be pre-examined.

In the following, I would like to give an explanation of the above.

session03 pet-01.coal handling

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