boiler ppt

Operation Of BoilersOperation Of Boilers

Operation Of BoilersOperation Of Boilers

�� The load control rangeThe load control range

�� The steady regime of boiler operationThe steady regime of boiler operation

�� The allowable boiler rangeThe allowable boiler range

�� The unsteady regime of boiler operationThe unsteady regime of boiler operation

The Load Control RangeThe Load Control Range

The automatic control system of a boiler The automatic control system of a boiler

responds quickly to the load without the responds quickly to the load without the

interference of the operating personnel. interference of the operating personnel.

The lowest limit is from 40The lowest limit is from 40--50% of rated 50% of rated

load. Smaller boilers not used for power load. Smaller boilers not used for power

stations have much lower control rangestations have much lower control range

The steady regime of boiler The steady regime of boiler

operationoperation

The steam parameters vary insignificantly The steam parameters vary insignificantly

at any load. The lowest limit is from 30at any load. The lowest limit is from 30--

40% of rated load40% of rated load

The Allowable Load RangesThe Allowable Load Ranges

The allowable load ranges include loads The allowable load ranges include loads

from limit of control range to the lowest from limit of control range to the lowest

load at which the boiler can function load at which the boiler can function

steadilysteadily

The Unsteady Regime of Boiler The Unsteady Regime of Boiler

OperationOperationLoad variation and fluctuation of steam Load variation and fluctuation of steam

parameters occur due to internal or external parameters occur due to internal or external

disturbancesdisturbances

Internal disturbances are variations in:Internal disturbances are variations in:

�� Flow rateFlow rate

�� TemperatureTemperature

�� Fuel consumption rateFuel consumption rate

�� Combustion air flow rateCombustion air flow rate

External disturbances are variations in:

� Steam pressure

� Load of the turbo-alternator

� The degree of opening of start-up and shut down

device

The Unsteady Regime of Boiler The Unsteady Regime of Boiler

OperationOperation

Steam Generators TestingSteam Generators Testing

�� Cold testingCold testing

�� Hydrostatic TestingHydrostatic Testing

�� Welding testingWelding testing

�� Hot testingHot testing

�� Flow measurementFlow measurement

�� Temperature measurementTemperature measurement

�� Dryness fraction of steam leaving the drumDryness fraction of steam leaving the drum

Flow MeasurementFlow Measurement

Steam, water, air and gas flow should be Steam, water, air and gas flow should be

measured using orifice, nozzle or venturi tubes measured using orifice, nozzle or venturi tubes

so as to check any flow meters connects in the so as to check any flow meters connects in the

boiler lines. These measuring instruments boiler lines. These measuring instruments

should be manufactured according to certain should be manufactured according to certain

standards, say ASME Performance Test standards, say ASME Performance Test

Codes.Codes.

�� Temperature measurementsTemperature measurements

These are carried out by using different types These are carried out by using different types

of thermocouples.of thermocouples.

�� Dryness fraction of steam leaving the Dryness fraction of steam leaving the

drum:drum:

this can be measured by a separating and a this can be measured by a separating and a

throttling calorimeter.throttling calorimeter.

Bringing a Boiler on LoadBringing a Boiler on Load�� In bringing a boiler on load the key parameter In bringing a boiler on load the key parameter

to be maintained is temperature. to be maintained is temperature.

�� In this case it is not maintained constant but In this case it is not maintained constant but is changed according to a predetermined is changed according to a predetermined pattern. pattern.

�� This a pattern is a compromise between the This a pattern is a compromise between the desire to bring the boiler ondesire to bring the boiler on--load as load as quiklyquikly as as possible and the risk of boiler damage by possible and the risk of boiler damage by thermal stresses arising from uneven.thermal stresses arising from uneven.

Bringing a Boiler on LoadBringing a Boiler on Load

There are four stages:There are four stages:

1.1. Warming up before circulation is Warming up before circulation is establishedestablished

2.2. Warming up after circulation is Warming up after circulation is establishedestablished

3.3. Stage when significant quantities of Stage when significant quantities of steam are being takensteam are being taken

4.4. Bringing the boiler on loadBringing the boiler on load

1.Warming up before circulation is 1.Warming up before circulation is

establishedestablished

�� During this phase the limit on the system During this phase the limit on the system is the temperature of boiler tubes. is the temperature of boiler tubes.

�� Until circulation is established there is a Until circulation is established there is a risk of local overheating in regions of risk of local overheating in regions of pockets of trapped steam and of serious pockets of trapped steam and of serious uneven heating between adjacent tubes.uneven heating between adjacent tubes.

�� Limited input of energy into the system is Limited input of energy into the system is needed and light oil burners are used.needed and light oil burners are used.

�� The provision of boiler circulation pumps The provision of boiler circulation pumps removes this stage from procedure.removes this stage from procedure.

2.Warming up after circulation is 2.Warming up after circulation is

establishedestablished

�� During this phase the main concern is stresses During this phase the main concern is stresses on the boiler drum arising from uneven on the boiler drum arising from uneven heating along its length or through the heating along its length or through the thickness of its metal. thickness of its metal.

�� These limitations are met by restricting the These limitations are met by restricting the permissible rate of rise of drum pressure and permissible rate of rise of drum pressure and hence of drum temperatures. hence of drum temperatures.

�� Progressively more energy is taken from the Progressively more energy is taken from the system by steam flow to drains and slightly system by steam flow to drains and slightly tighter input is needed. tighter input is needed.

�� Careful control of the energy input is most Careful control of the energy input is most important at this stage and this is achieved by important at this stage and this is achieved by varying the number of oil burners if applicablevarying the number of oil burners if applicable

3.Stage when significant quantities of steam 3.Stage when significant quantities of steam

are being takenare being taken

�� This stage is present when boilers used for This stage is present when boilers used for industrial processes are also used to generate industrial processes are also used to generate power, and then turbine conditions must match power, and then turbine conditions must match with the steam output conditions. with the steam output conditions.

�� The limit now passes to the maximum The limit now passes to the maximum permissible value in the superheater tube metal permissible value in the superheater tube metal temperatures.temperatures.

�� The steam and fuel flows are increasing since The steam and fuel flows are increasing since appreciable energy is being taken from the appreciable energy is being taken from the system, but the steam flows are not yet system, but the steam flows are not yet adequate to ensure superheater cooling.adequate to ensure superheater cooling.

�� Considerable drainage on the superheater may Considerable drainage on the superheater may still be necessarystill be necessary

4.Bringing the boiler on load4.Bringing the boiler on load

�� Here the limit is still the superheater Here the limit is still the superheater temperature.temperature.

�� During this section there must be smooth During this section there must be smooth change from the light oil used in the initial change from the light oil used in the initial stages of boiler operation to the heavy fuel stages of boiler operation to the heavy fuel oil used under spontaneous operation. oil used under spontaneous operation.

�� The sequential ignition of these burners The sequential ignition of these burners provides the fine control of the energy provides the fine control of the energy needed. needed.

�� As each burner is put into service, care must As each burner is put into service, care must be taken to see that it ignites properly, and be taken to see that it ignites properly, and that it burns with bright smokeless flame and that it burns with bright smokeless flame and does not subsequently go outdoes not subsequently go out

�� The following are the minimum The following are the minimum

standards for the operation as listed standards for the operation as listed

in ASME Section VI, VIIin ASME Section VI, VII

On a daily basis, boiler operation

¨ Test performed and the results,� ¨ Unusual boiler conditions,� ¨ Changes in equipment status and the reason

¨ Steam pressure� ¨ Stack temperature� ¨ Flame condition,� ¨ Confirmation that no smell of gas or evidence

of fuel leaks exists� ¨ Confirmation that no steam or water leaks

from the boiler� ¨ Operator’s name, initials, and dates of log

entry.


�� Confirmation that pressure and temperatures Confirmation that pressure and temperatures are within the guidelines set by the are within the guidelines set by the manufacturer of the boiler.manufacturer of the boiler.

�� In no case shall the pressures/temperatures beIn no case shall the pressures/temperatures be

greater than the manufacturergreater than the manufacturer’’s maximum s maximum allowable working pressure/temperatures. allowable working pressure/temperatures.

�� The maximum allowable pressure and or The maximum allowable pressure and or temperature are denoted on the nomenclature temperature are denoted on the nomenclature plate affixed to the boiler (data plate).plate affixed to the boiler (data plate).


�� Observation of condition of the flame to Observation of condition of the flame to determine if it is even, and not off determine if it is even, and not off colorcolor..

�� Gas burner flame should be Gas burner flame should be blueblue with varying with varying amounts ofamounts of yellowyellow on the flame ends on the flame ends depending upon the firing rate.depending upon the firing rate.

�� The flame should be even around the burner.The flame should be even around the burner.

�� Oil burner flame should be bright yellow Oil burner flame should be bright yellow without dark trails off the end of the flame.without dark trails off the end of the flame.

On a weekly interval, the boiler operation

�� Observing the boiler during its shutdown Observing the boiler during its shutdown and startand start--up cycle while listening for the fuel up cycle while listening for the fuel solenoids to activate and listening for any solenoids to activate and listening for any unusual noises (unusual noises (such as the fuel valvesuch as the fuel valvesolenoid chatteringsolenoid chattering, , buzzing loudlybuzzing loudly, etc.), etc.)

�� Testing low water cutTesting low water cut--off and boiler lowoff and boiler low--water alarm for lowwater alarm for low--pressure boilers while in pressure boilers while in operation. The test must show the boiler will operation. The test must show the boiler will shut off if a low water condition exists.shut off if a low water condition exists.

On a weekly interval, the boiler operation

�� Visual checks of ignition and flame detection Visual checks of ignition and flame detection system, looking for any abnormal conditions, such system, looking for any abnormal conditions, such as frayed wires, loose or broken conduit, loose as frayed wires, loose or broken conduit, loose wiring, etc.wiring, etc.

�� Checking the firing rate controls and linkage for Checking the firing rate controls and linkage for freedom of movement and linkage connections.freedom of movement and linkage connections.

�� Cleaning fuel oil filters and strainers. Unless your Cleaning fuel oil filters and strainers. Unless your boiler is equipped with dual filters, this must be boiler is equipped with dual filters, this must be done with the boiler shutdown.done with the boiler shutdown.

�� Always shutdown the fuel oil Always shutdown the fuel oil pump(spump(s) and valve ) and valve off to the fuel oil filters prior to cleaning or off to the fuel oil filters prior to cleaning or replacement.replacement.

�� Following approved lock out, tag out procedures.Following approved lock out, tag out procedures.

On a monthly interval, the boiler operation

�� Visually checking the boiler during Visually checking the boiler during shutdown and startshutdown and start--up.up. Make sure Make sure the burner fan runs through its pre the burner fan runs through its pre and and postpost--purgepurge ventilation cycles.ventilation cycles.

�� Watch and listen to the fuel Watch and listen to the fuel solenoid valves to insure they are solenoid valves to insure they are closing as prescribed by the closing as prescribed by the manufacturermanufacturer’’s recommendations.s recommendations.


�� Checking all floor drains in the boiler Checking all floor drains in the boiler room for proper operationroom for proper operation..

�� First look down the drain to see if First look down the drain to see if water is visible, which will indicate the water is visible, which will indicate the automatic drain charging system is automatic drain charging system is working properlyworking properly ..

�� Put about one gallon of water down Put about one gallon of water down each drain to insure that the drain is each drain to insure that the drain is free from clog. free from clog.

�� If water can not be seen in the drain If water can not be seen in the drain indicate such on the boiler room log indicate such on the boiler room log and notify the maintenance person to and notify the maintenance person to have the situation corrected.have the situation corrected.


�� Inspecting the combustion air louvers Inspecting the combustion air louvers and or ventilation screens both inside theand or ventilation screens both inside the

boiler room and outside.boiler room and outside. They must be They must be free from dust and debris, clean if free from dust and debris, clean if necessary.necessary.

�� Visually checking the boiler stack, Visually checking the boiler stack, looking for areas of overheating, looking for areas of overheating, blackened area where flue gasses are blackened area where flue gasses are escaping, areas of rust, free operation of escaping, areas of rust, free operation of barometric damper (barometric damper (if equippedif equipped), and ), and joints coming apart or holes in flue joints coming apart or holes in flue ducting.ducting.

On a quarterly basis, boiler On a quarterly basis, boiler

operation operation

�� Testing the flame safeguard control Testing the flame safeguard control system. This test shall verify proper system. This test shall verify proper operation of control devices and cause operation of control devices and cause a safety shut down and lockout. a safety shut down and lockout.

�� The boiler should not restart without The boiler should not restart without resetting the flame safe guard control. resetting the flame safe guard control.

On a quarterly basis, boiler On a quarterly basis, boiler

operation operation

�� Testing low gas pressure limit control Testing low gas pressure limit control system. Slowly close the gas valve upstream system. Slowly close the gas valve upstream from the lowfrom the low--pressure gas limit control.pressure gas limit control. This This should cause the burner to shut off and lock should cause the burner to shut off and lock out.out.

�� For oil fired burners, conduct the same test. For oil fired burners, conduct the same test. without damaging the fuel oil pumps or the without damaging the fuel oil pumps or the system.system.

�� Checking alternate fuel supply system by Checking alternate fuel supply system by switching to the backup fuel source.switching to the backup fuel source.

Fireside parameter Monitoring and Fireside parameter Monitoring and

ControlControl

�� The preservation of boiler operation and The preservation of boiler operation and performance includes meeting underlined performance includes meeting underlined design assumptions and process control. design assumptions and process control.

�� The boiler design involves the energy balance The boiler design involves the energy balance between the fireside and the steam side between the fireside and the steam side parameters.parameters.


ControlControl

�� In a typical fossil power plant, there is more In a typical fossil power plant, there is more steam side instrumentation installed with the steam side instrumentation installed with the original control system than there is flue gas original control system than there is flue gas side instrumentation. side instrumentation.

�� However, the fireside provides the heat However, the fireside provides the heat energy input to the boiler system and it is energy input to the boiler system and it is extremely important to control the fireside extremely important to control the fireside operating parameters to ensure the boiler operating parameters to ensure the boiler performance. performance.


ControlControlTypically, the boiler lacks fireside control.Typically, the boiler lacks fireside control.

�� The fuel and air are mixed, combustion The fuel and air are mixed, combustion takes place in the burner system and the takes place in the burner system and the next monitoring point in the flue gas path next monitoring point in the flue gas path is the boiler exit temperature.is the boiler exit temperature.

�� Basically, there is nothing in between. Basically, there is nothing in between.

�� There is a simple logic to converting from There is a simple logic to converting from a two point control, burner and boiler exit a two point control, burner and boiler exit temperature, to a three point control; i.e., temperature, to a three point control; i.e., burner, furnace exit gas temperature burner, furnace exit gas temperature ((FEGTFEGT), then boiler exit temperature), then boiler exit temperature..

�� This extra control point, This extra control point, FEGTFEGT, can have a , can have a major impact on boiler performance and major impact on boiler performance and reliability.reliability.

Fireside parameter Monitoring Fireside parameter Monitoring

and Controland Control

�� Basically, the furnace exit point Basically, the furnace exit point

separates the radiation zone from separates the radiation zone from

the convection pass. the convection pass.

�� FEGTFEGT is one of the most important is one of the most important

interface parameters in boiler interface parameters in boiler

design and operation. design and operation.

Fireside parameter Monitoring Fireside parameter Monitoring

and Controland ControlTypical boiler gas side design involves the Typical boiler gas side design involves the

followingfollowing

�� Input/plan areas (Btu/sq. ftInput/plan areas (Btu/sq. ft--hr) hr)

�� Gas temperature entering first pendant Gas temperature entering first pendant

surface over the archsurface over the arch

�� Gas temperature leaving the furnace Gas temperature leaving the furnace

�� Location and quantity of furnace wall Location and quantity of furnace wall

blowersblowers

�� Burner input and burner clearance Burner input and burner clearance

�� Total heat available to burner zone Total heat available to burner zone

(Btu/(Btu/sq.ftsq.ft......--hr) hr)

Operational parameters affecting Operational parameters affecting

FEGTFEGT

�� Excess air level Excess air level

�� Furnace heat absorption rate Furnace heat absorption rate

(modified by soot blowing) (modified by soot blowing)

�� Burner selections, Burner tilt Burner selections, Burner tilt

�� Low NOx operations Low NOx operations

�� Fuel quality Fuel quality

�� Air inAir in--leakage leakage

FEGTFEGT

�� A furnace A furnace startupstartup probe is probe is sometimes used to protect the sometimes used to protect the superheatersuperheater and and reheaterreheater tubes prior tubes prior to the establishment of steam flow. to the establishment of steam flow.

�� Unfortunately, the current Unfortunately, the current startupstartupprobes can not be used for the probes can not be used for the complete flue gas temperature complete flue gas temperature range. range.

FEGTFEGT

�� For many years the industry has For many years the industry has been actively involved in developing been actively involved in developing more accurate instrumentation, more accurate instrumentation, analysis methods, and performance analysis methods, and performance improvement techniques for the fire improvement techniques for the fire side parameters control. side parameters control.

FEGTFEGT�� A furnace A furnace startupstartup probe is probe is sometimes used to protect the sometimes used to protect the superheatersuperheater and and reheaterreheater tubes prior tubes prior to the establishment of steam flow. to the establishment of steam flow.

�� Unfortunately, the current Unfortunately, the current startupstartupprobes can not be used for the probes can not be used for the complete flue gas temperature complete flue gas temperature range. range.

�� For many years the industry has For many years the industry has been actively involved in developing been actively involved in developing more accurate instrumentation, more accurate instrumentation, analysis methods, and performance analysis methods, and performance improvement techniques for the fire improvement techniques for the fire side parameters control. side parameters control.

FEGTFEGT

�� There are many techniques that There are many techniques that can be used to obtain the FEGT can be used to obtain the FEGT onon--line, line, i.ei.e, direct measurement , direct measurement or from calculations. or from calculations.

�� Direct measurement techniques Direct measurement techniques can be intrusive and noncan be intrusive and non--intrusive. Operators can use this intrusive. Operators can use this information to balance information to balance combustion.combustion.

FEGTFEGT

FEGT control is a critical parameter FEGT control is a critical parameter which canwhich can

be used to preserve the boiler be used to preserve the boiler operation andoperation and

performance including, emission, performance including, emission, reliability,reliability,

and safety. and safety.

FEGTFEGTIf FEGT deviates from the design value the If FEGT deviates from the design value the following following

Undesired condition can occur:Undesired condition can occur:

�� Increased Increased slaggingslagging/ fouling of water / fouling of water walls, walls, superheatersuperheater, and economizer, and , and economizer, and air heaters air heaters

�� Increased corrosion rates of Increased corrosion rates of superheatersuperheaterand and reheaterreheater tubestubes

�� Potential of convective pass tube Potential of convective pass tube overheating (creep damage), requiring overheating (creep damage), requiring more more attemperationattemperation

�� Altered design conditions which are more Altered design conditions which are more difficult to correct by the operator difficult to correct by the operator

�� Increased flue gas temperature in the Increased flue gas temperature in the boiler exit which increases heat loss and boiler exit which increases heat loss and lowers efficiency lowers efficiency

FEGTFEGT

FEGT provides an operational safeguard and FEGT provides an operational safeguard and

indictor for the boiler operation. indictor for the boiler operation.

The following influential Factors will be discussed:The following influential Factors will be discussed:

�� SlaggingSlagging and fouling controland fouling control

�� Soot blowing Soot blowing

�� Superheat steam temperature controlSuperheat steam temperature control

�� Low NOx firing Low NOx firing

SlaggingSlagging and fouling and fouling

controlcontrol�� One of the important characteristics of the One of the important characteristics of the

fuel from a boiler design view point is the fuel from a boiler design view point is the

slaggingslagging and fouling control. and fouling control.

�� The formation of slag deposits is caused by The formation of slag deposits is caused by

the deposition of molten ash on surfaces the deposition of molten ash on surfaces

receiving heat by radiation such as the receiving heat by radiation such as the

furnace and radiant sections of the furnace and radiant sections of the

supereheatersupereheater. .

�� Entrained in the gas stream, molten ash Entrained in the gas stream, molten ash

particles strike the wall or tube surface particles strike the wall or tube surface

becoming chilled then solidifybecoming chilled then solidify. .

SlaggingSlagging and fouling and fouling

controlcontrol

�� If slag is allowed to accumulate on the lower If slag is allowed to accumulate on the lower

furnace walls, furnace exit gas temperature furnace walls, furnace exit gas temperature

will rise and the will rise and the slaggingslagging area is forced area is forced

higher into the furnace. higher into the furnace.

�� The effect on the furnace performance can be The effect on the furnace performance can be

drastic. drastic.

�� Proper boiler operation requires keeping the Proper boiler operation requires keeping the

ash particles away from the walls and in ash particles away from the walls and in

suspension in the gas stream until the ash is suspension in the gas stream until the ash is

sufficiently cool to be admitted to the sufficiently cool to be admitted to the

convection pass. convection pass.

Parameters that result in Parameters that result in

increased deposition increased deposition

�� SlaggingSlagging

�� Fuel qualityFuel quality

�� Combustion problems and poor Combustion problems and poor flame stabilityflame stability

�� Low excess OLow excess O22 or Oor O22 imbalanceimbalance

�� Inadequate sootInadequate soot--blowingblowing

�� High FEGTHigh FEGT

�� Fouling Fouling


increased deposition includeincreased deposition include

�� Maintain the hot furnace can reduce the Maintain the hot furnace can reduce the furnace furnace slaggingslagging problem. problem.

�� Limiting FEGT to a minimum 55Limiting FEGT to a minimum 55°°°°°°°°CC below below the ash softening temperature can the ash softening temperature can substantially improve the substantially improve the convective convective pass fouling problempass fouling problem, because the dry , because the dry ash leaving the furnace will not stick to ash leaving the furnace will not stick to the steam tubes. the steam tubes.



�� If the If the foulingfouling and and blockageblockage in the in the convective pass is reduced, the convective pass is reduced, the superheat soot blowing and fan superheat soot blowing and fan power can be reduced which power can be reduced which improves the heat rate.improves the heat rate.

�� It also prevent soot blower erosion.It also prevent soot blower erosion.



�� If the fuel being burned is changed, If the fuel being burned is changed,

the ash fusion temperature for new the ash fusion temperature for new

fuel can be obtained from the fuel can be obtained from the

laboratory test laboratory test

�� A new A new FEGT limitFEGT limit can be established can be established

by the operator and to adjust other by the operator and to adjust other

operational parameters to minimize operational parameters to minimize

the potential of the potential of slaggingslagging/ fouling/ fouling. .

The combustion system should be The combustion system should be

tuned to achieve the followingtuned to achieve the following�� Uniform flue gas temperature and Uniform flue gas temperature and

flow distributionflow distribution

�� Uniform distribution of excess OUniform distribution of excess O22

�� Minimize fly ash unburned carbon Minimize fly ash unburned carbon

content content

�� Minimize air heater leakage and Minimize air heater leakage and

casing aircasing air--inin--leakageleakage

�� Balance secondary air and fuel Balance secondary air and fuel

distributiondistribution

�� Proper primary air/fuel proportionProper primary air/fuel proportion

Soot blowingSoot blowing

�� Ash slag and soot deposits on the tubes Ash slag and soot deposits on the tubes

act as insulators that prevent heat act as insulators that prevent heat

transfer. transfer.

�� It can also restrict the flow of flue gas. It can also restrict the flow of flue gas.

Therefore, keeping the gas side of boiler Therefore, keeping the gas side of boiler

tubes clean is essential to preserve the tubes clean is essential to preserve the

boiler operation. boiler operation.

�� Soot blowing has proved to be the most Soot blowing has proved to be the most

practical method of removing the practical method of removing the

deposits. deposits.


�� Observation of the boiler for Observation of the boiler for slaggingslagging

and fouling patterns and for soot and fouling patterns and for soot

blower effectiveness should be made blower effectiveness should be made

on a regular basis.on a regular basis.

�� A prime concern in soot blower A prime concern in soot blower

operation is to minimize the boiler tube operation is to minimize the boiler tube

erosion. Soot blowers must be erosion. Soot blowers must be

maintained in good operating maintained in good operating

condition.condition.


Effective soot blowing should consider:Effective soot blowing should consider:

�� Blowing frequencyBlowing frequency

�� Blowing timeBlowing time

�� Blowing sequence Blowing sequence

�� Blowing pressureBlowing pressure

�� Nozzle position Nozzle position

Soot blowingSoot blowing�� FEGT can be used as the FEGT can be used as the primary indicatorprimary indicatorto establish the scheme for automatic to establish the scheme for automatic soot blowing or to soot blowing or to alert the operatoralert the operator to to start the manual sootstart the manual soot--blowing operation. blowing operation.

�� If FEGT exceeds the original design value, If FEGT exceeds the original design value, this indicates that the furnace is dirty and this indicates that the furnace is dirty and the operator should initiate the furnace the operator should initiate the furnace soot blowing and the soot blowing should soot blowing and the soot blowing should be stopped when FEGT has been reduced be stopped when FEGT has been reduced below the original design value.below the original design value.


�� The overThe over--blowing in the furnace is blowing in the furnace is wasting the energy and can also create wasting the energy and can also create soot blower erosion problem in the water soot blower erosion problem in the water wall tube.wall tube.

Superheat steam temperature Superheat steam temperature

controlcontrol�� For the tangentially fired furnace, the For the tangentially fired furnace, the burner tilts are typically used as one of burner tilts are typically used as one of the methods to control the final steam the methods to control the final steam temperature. temperature.

�� The use of tilting up option to achieve The use of tilting up option to achieve desired steam temperatures should be desired steam temperatures should be applied at low and intermediate loads applied at low and intermediate loads only. only.

�� Burner tilts position should be horizontal Burner tilts position should be horizontal or angled slightly downward at high or angled slightly downward at high loads. loads.

Superheat steam temperature Superheat steam temperature

controlcontrol�� The reason for tilts down or horizontally is to The reason for tilts down or horizontally is to increase residence time for complete increase residence time for complete combustion.combustion.

�� The burner tilts up condition may increase The burner tilts up condition may increase FEGT, which can increase the potential of FEGT, which can increase the potential of slaggingslagging and fouling problems as discussed and fouling problems as discussed previously.previously.

�� If the final steam temperature can not be If the final steam temperature can not be reached, other options such as increase reached, other options such as increase excess air should be considered in excess air should be considered in conjunction with the burner tilting to conjunction with the burner tilting to maintain FEGT within the allowable limit.maintain FEGT within the allowable limit.

Low NOx firingLow NOx firing�� Wall fired low NOx burners normally Wall fired low NOx burners normally result in longer flames and higher result in longer flames and higher unburned carbon content.unburned carbon content.

�� The potential of secondary combustion The potential of secondary combustion could become more intense and increase could become more intense and increase fouling and fouling and slaggingslagging of the convection of the convection pass and air heaters. pass and air heaters.

�� The underThe under--stoichiometric combustion, stoichiometric combustion, typically used in the low NOx firing, will typically used in the low NOx firing, will result in starvation of oxygen in the result in starvation of oxygen in the furnace areas. furnace areas.

Low NOx firingLow NOx firing�� This can creates areas of reducing This can creates areas of reducing atmosphere, which can accelerate atmosphere, which can accelerate fireside wastage of water wall tubes. fireside wastage of water wall tubes.

�� Delayed combustion or secondary Delayed combustion or secondary combustion sometimes produce high combustion sometimes produce high FEGT. These high temperatures can cause FEGT. These high temperatures can cause overheating of overheating of superheatersuperheater and and reheaterreheatertubes. tubes.

�� It is essential for the operator to It is essential for the operator to maintain the original design FEGT to maintain the original design FEGT to minimize other side effects. Otherwise minimize other side effects. Otherwise tradeoffs are required and comprise the tradeoffs are required and comprise the multiple system objectives.multiple system objectives.

Using the InfraUsing the Infra--ViewView®®InfraredInfrared

Thermometers Thermometers

�� The furnace exit gas temperature The furnace exit gas temperature ((FEGTFEGT) in a boiler is a critical ) in a boiler is a critical parameter which requires monitoring parameter which requires monitoring during boiler startduring boiler start--up and onup and on--line line operation.operation.

�� StartStart--up up FEGTsFEGTs must be controlled so must be controlled so as not to exceed allowable as not to exceed allowable superheatersuperheater tube metal temperatures.tube metal temperatures.

�� Many boilers use airMany boilers use air--cooled probes, cooled probes, which must be retracted when which must be retracted when temperatures reach temperatures reach 538538°°°°°°°°CC..



�� Maintaining the FEGT within the design Maintaining the FEGT within the design limit during the normal operation can limit during the normal operation can ensure boiler operability, thermal ensure boiler operability, thermal performance and boiler reliability.performance and boiler reliability.

�� The problem in the past is the lack of onThe problem in the past is the lack of on--line instrumentation to measure the high line instrumentation to measure the high flue gas temperature.flue gas temperature.



�� WaterWater--cooled HVT probes have been used cooled HVT probes have been used for many years to measure gas for many years to measure gas

temperature above temperature above 538538°°°°°°°°CC�� Because of the probe length and weight Because of the probe length and weight limitations, HVT is used primarily for limitations, HVT is used primarily for testing purposes and not for continuous testing purposes and not for continuous operation.operation.

Typical InfraTypical Infra--ViewView®® Boiler Thermometer InstallationBoiler Thermometer Installation

InfraInfra--ViewView®®InfraredInfrared ThermometersThermometers

�� InfraInfra--ViewView®®InfraredInfrared Thermometers are Thermometers are remote sensing infrared detectors that remote sensing infrared detectors that are permanently flange mounted on are permanently flange mounted on any port, door or penetration into the any port, door or penetration into the boiler or furnace. boiler or furnace.

�� It is a lightweight device and can also It is a lightweight device and can also be used as a portable system for testing be used as a portable system for testing purposes. purposes.


�� The InfraThe Infra--ViewView®®patentedpatented design is design is supplied with a rugged protectivesupplied with a rugged protective--cooling jacket that is factory assembled cooling jacket that is factory assembled and preand pre--piped with an air cooler, piped with an air cooler, purging and filtering system designed purging and filtering system designed to work in most severe service to work in most severe service environmentsenvironments..


�� Customer supplied compressed air Customer supplied compressed air and two wire shielded signal cable and two wire shielded signal cable is all that is necessary for operation is all that is necessary for operation when integrated in a when integrated in a 44--20mA20mA signal signal loop supplied from a DCS, digital or loop supplied from a DCS, digital or analoganalog recording device. recording device.

�� The InfraThe Infra--ViewView®®infraredinfrared "non"non--contact" sensors monitors flue gas contact" sensors monitors flue gas temperatures in the boiler or temperatures in the boiler or furnace ranging from furnace ranging from 120120°°CC to to 1,6501,650°°C.C.

�� The proprietary infrared spectral response of The proprietary infrared spectral response of the Infrathe Infra--View thermometer is preView thermometer is pre--set set specifically to detect infrared emissions from specifically to detect infrared emissions from hot COhot CO22 gas. gas.

�� This is accomplished by filtering out all other This is accomplished by filtering out all other wavelengths of infrared energywavelengths of infrared energy. .

�� Modern infrared thermometry has advanced Modern infrared thermometry has advanced significantly with the use of "selective significantly with the use of "selective filtering" of the incoming infrared signalfiltering" of the incoming infrared signal. .

InfraInfra--ViewView®®InfraredInfrared

ThermometersThermometers

�� Specifically, selected narrow band spectral Specifically, selected narrow band spectral responses are necessary in order to see through responses are necessary in order to see through atmospheric interferences in the sight path, to atmospheric interferences in the sight path, to obtain a measurement of gas or other substance obtain a measurement of gas or other substance which is transparent to a broad band of infrared which is transparent to a broad band of infrared energy.energy.




�� "Infrared radiation is observed as emitted from "Infrared radiation is observed as emitted from excited molecules of gases. Many of the energy excited molecules of gases. Many of the energy transitions which take place in gases excited transitions which take place in gases excited thermally or electrically result in radiation thermally or electrically result in radiation emission in the infrared region. emission in the infrared region.



�� Gaseous emission differs in character from solid Gaseous emission differs in character from solid emission in that the former consists of discrete emission in that the former consists of discrete spectrum lines or bands, with significant spectrum lines or bands, with significant discontinuities, while the latter shows a discontinuities, while the latter shows a continuous distribution of energy throughout a continuous distribution of energy throughout a broad band spectrum." Gases such as CO and CObroad band spectrum." Gases such as CO and CO22

exhibit a strong but narrow infrared spectral exhibit a strong but narrow infrared spectral response that can be detected with sensitive response that can be detected with sensitive infrared sensors utilizing the specific spectral infrared sensors utilizing the specific spectral filter.filter.



�� Since COSince CO22 gas is a bygas is a by--product of the product of the combustion of all fossil fuels, its unique combustion of all fossil fuels, its unique spectral response was selected because of its spectral response was selected because of its applicability to all boilers and furnaces applicability to all boilers and furnaces regardless of the fuel burned.regardless of the fuel burned.



�� With a concentrations of COWith a concentrations of CO22 gas typically gas typically found in fossil fuel burning utility and found in fossil fuel burning utility and industrial boilers, there is a high enough industrial boilers, there is a high enough level (level (10 10 -- 12%)12%) to reach a threshold of to reach a threshold of detection where the Infradetection where the Infra--View sensor can View sensor can measure the average or peak temperature measure the average or peak temperature directly within the field of view of the directly within the field of view of the instrument.instrument.



�� Because the InfraBecause the Infra--View "sees" the COView "sees" the CO22 gas gas within the boiler as semiwithin the boiler as semi--transparent or transparent or opaque medium, within the conical field of opaque medium, within the conical field of view (view (30:130:1) the largest volume of gas ) the largest volume of gas molecules are oriented farthest away from molecules are oriented farthest away from the sensor.the sensor.

�� Hotter gases, because of the selective Hotter gases, because of the selective spectral filter, are spectral filter, are favoredfavored over the cooler over the cooler gases located nearer the sensor comprising gases located nearer the sensor comprising a smaller volume in the field of view.a smaller volume in the field of view.



�� As a consequence, the InfraAs a consequence, the Infra--View will sense View will sense heated flue gas in the boiler yielding a heated flue gas in the boiler yielding a temperature reading that is indicative of the temperature reading that is indicative of the overall boiler environment.overall boiler environment.

�� Secondly, the quick response time (100 Secondly, the quick response time (100 msecmsec.) .) when averaged over say, 10 seconds (100 when averaged over say, 10 seconds (100 readings in all) generates a representative readings in all) generates a representative temperature reading of the dynamic upward flow temperature reading of the dynamic upward flow of heated gases past the sensor posting the of heated gases past the sensor posting the processed data in a time vs. temperature processed data in a time vs. temperature relationship.relationship.

ConclusionConclusion�� The preservation of boiler operation and The preservation of boiler operation and performance requires proper fireside performance requires proper fireside operating fireside control.operating fireside control.

�� Basically, the existing boilers are lacking Basically, the existing boilers are lacking of proper fireside control. of proper fireside control.

�� The fuel and air are mixed, combustion The fuel and air are mixed, combustion takes place in the burner system and the takes place in the burner system and the next monitoring point in the flue gas next monitoring point in the flue gas path is the boiler exit temperature.path is the boiler exit temperature.

�� It is recommended that the process be It is recommended that the process be converted from two point control, burner converted from two point control, burner and boiler exit temperature to three and boiler exit temperature to three point control; i.e., burner, FEGT, then point control; i.e., burner, FEGT, then boiler exit temperature. boiler exit temperature.

ConclusionConclusion

�� This extra control point, FEGT, can have a This extra control point, FEGT, can have a

major impact on boiler performance and major impact on boiler performance and

reliability. reliability.

�� The InfraThe Infra--view system provides wide view system provides wide

range flue gas temperature measurement range flue gas temperature measurement

and is a low cost effect instrumentation and is a low cost effect instrumentation

to measure theto measure the FEGT onFEGT on--lineline. .

�� The system has been demonstrated The system has been demonstrated

successfully in more than successfully in more than 400 sites400 sites to to

provide realprovide real--time information for boiler time information for boiler

operation, performance, and reliability operation, performance, and reliability

improvement.improvement.

boiler ppt

Documents

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allowable boiler

boiler operators

boiler operationconfirmation

boiler lines

boiler operation test

temperature of boiler

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