Trouble Shooting of Boilers

Trouble shooting in Boiler operation & reduction of auxiliary

power consumption

Presented by

S. SivakumarAGM- O&M Contracts

Cethar Vessels Ltd, Trichy

Cethar Vessels Ltd, Trichy 2

CETHAR VESSELS LIMITED

Leading manufacture of AFBC , CFBC , WHRB for sponge iron kiln Gas, cement kiln gas ,DG exhaust gas & supply of power plant on EPC basis for more than two decades .

Tied up with Riley Power Inc, USA for PC fired boilers of sub critical & super critical pressure. Collaboration with Riley / Siemens Benson Technology for super critical PC boilers.

Collaboration with Siemens for Super Critical CFBC boilers.

Tied up with OJSC power machineries , Russia for turbine design and Manufacturing.

Executing O & M contracts of captive power plants of any Capacity through Cethar energy ltd.


Major projects under execution:

2x 135 MWe IPP with CFBC Boiler - M/s.Aryan Coal Benification

2 x 350 MWe PF Fired Boiler - M/s.Ind Barath energy Ltd.

2 x 350 MWe PF Fired Boiler - M/s.Meenakshi energy Ltd.

2 x 150 MWe IPP with CFBC Boiler - M/s.Shree cement

2 x 150 MWe IPP with PF Fired Boiler - M/s.Vandana vidhuyut

3 x 70 MWe CFBC Boiler - M/s.Jayprakash associates

65 Boilers are under execution for IPP, CPP & Co-gen

10 IPP & Captive power plants are under execution


Credentials

CVL had designed, manufactured, erected and commissioned more than 1000 FBC boilers.

Based on our versatile experience during operation and maintenance, we have listed few problems faced and the causes, solution given

for the information to this elite league


Low steam generation

Identifications

• Low steam pressure, low

steam flow in the control

room

Causes

• Fuel quality

• Low air box pressure will

lead to high bed

temperature and

limitation in fuel feeding

• Heavy air leakage in the

system and limitation in

combustion air to

furnace.


Low steam generation

Identifications

• Low steam pressure, low

steam flow in the control

room

Causes

• Heavy flue gas leakage

in the system and

limitation in ID fan

• Fouling in evaporation

surface.

• Deposition in the

evaporator tubes due to

water chemistry


Low steam temperature

Identifications

• Low steam temperature

indication in control

room at boiler outlet and

turbine inlet

Causes

• Passing of desuper heater

control valve

• Low volatile fuel

• Low bed temperature

operation

• Inadequate “excess air”

operation

• Fouling in super heater


High steam temperature

Identification

• Steam temperature at

boiler outlet and turbine

inlet is more

Causes

• Low feed water

temperature to boiler

• High volatile fuel burning

• High excess of air

• Low air box pressure

• Inadequate de-super

heating


Furnace pressure fluctuation /

positive furnace pressure

Identifications

• Furnace pressure

indication variation in

control room

Causes

• Instrument calibration and

impulse tube attachment intact

• ID fan damper malfunctioning

• Fuel input variation to furnace

• Pressure part leakage


Furnace pressure fluctuation /

positive furnace pressure

Identifications

• Furnace pressure

indication variation in

control room

Causes

• Fouling in the gas path

• Accumulation of ash in gas path

and ash chute

• Leakage in flue gas duct and

limitation of ID fan

• Erosion of ID fan impeller


Sagging of Super heaters

Identification

Visual inspection during shut down

Causes

Flame impingement onsuper heater during startup.

Frequent lifting of Drumsafety valve

Over heating of superheater coils due to boileroperation with clinker


Sagging of Super heaters

Identification

Visual inspection during shut down

Causes

Compartment transferwithout adequate steamflow

Boiler operation with morefuel fines


Boiler operation with clinker formation

Identification

Uneven combustor bed temperature

Load raising restriction

Significant variation in air box pressure

Cause

Damage in bed thermocouples.

Damage of air nozzle.

Fuel nozzle damage

Improper air fuel mixture


Low Air box pressure

Identification

Low air box pressure with normal bed pressure and optimum FD airflow at MCR

Cause

FD ducting bellow leakage, heavy air leakage in FD duct, failure of air nozzle and leakage in air heater.

Inspection and rectification on the above to be taken up


Coal Jamming in PA line / Mixing nozzle

Identification

Bed Temperature Drop

High negative furnace pressure

PA line back pressure

Cause

High moisture, low PA header pressure at PA line shall lead to jamming. Inspection from coal feeder to PA line and mixing nozzle, adequate PA header air pressure to be taken care


Frequent tripping of FUEL feeder

Identification

• Trip alarm in DCS.

• Bed temperature drop.

• High negative furnace

pressure

Causes

Presence of any foreign materials and cleaning.

High moisture and de-choking

Feeder drive mechanicalarrangement failure andrectification


Identification

• Feeder speed showing

zero

• Feeder motor over

load trip.

Causes

Testing condition of motor

Testing the speed control drive healthiness

Frequent tripping of FUEL feeder


Oil firing start up failure

Identification

No bed temperature rise even after 2 hrs of light up

Causes

Inspection for nozzle choke &inadequate oil pressure(6Ksc)

Ensure optimum air boxpressure.

Ensure proper bed materialsize(2.36 to 0.86).

Ensure appropriate charcoalsize and moisture freecharcoal.

Inspection of bed condition


High exit flue gas temperature

Identification

• High flue gas

temperature at the outlet

of APH

Causes

• High excess air

• Fouling in evaporator,

super heater and air pre

heater


High unburnt carbon in ash

Identification

• High % LOI in ash as

per lab report

Causes

• Operating the boiler with

clinker

• Inadequate air supply

• Fuel quality

• High amount of fines in

fuel

• Heavy load fluctuation and

instable furnace condition


High unburnt carbon in ash

Identification

• High % of LOI in ash

Causes

• Low air box pressure

• High PA pressure

• Improper distribution of

fuel in furnace


High Plant Heat Rate• Identification

• Steam leakage in boiler and

steam piping

• Low turbine inlet steam

pressure and temperature

• Condenser low vacuum

• High exhaust steam

temperature & pressure

• Action to be taken

• Steam leakage to be arrested

• Operating the turbine at

design temperature and

pressure

• Condenser air ingress to be

rectified

• HP heater under

performance

• Turbine inspection for

depositions


High Plant Heat Rate

Identification

• Low boiler efficiency

• Low Feed water

temperature

• High turbine wheel

chamber

Action to be taken

• Combustion system

heating surface area to be

checked.

• Rectify air ingress, flue gas

leakage are to be attended.

• Insulation condition to be

checked and rectified.

• Turbine blade failure

causes exhaust steam

temperature


Auxiliary power consumption

reduction

•After plant commissioning and stabilization the design

margin in the equipment shall be optimized by

implementing modification in the system, providing

VFD for the following equipments


Auxiliary power consumption reduction

• Cooling water pumps

• CEP

• Boiler Feed pumps(case study given)

• Fans(case study given)

• ACC fans


Auxiliary power consumption

reduction

• Optimization of coal handling plant operation

• Optimization of AHP operating and

Compressors

• Optimization of make up water consumption and

WTP operation


Case study I :

Reported issue:

Excess coal consumption


Plant design details:

Plant capacity : 1 X 8 MWe co-gen plant

Boiler capacity : 40 TPH

Type of firing : AFBC

Steam pressure : 68 ata

Steam temperature : 495 °C


Design Fuel Analysis

Moisture : 13.98%GCV : 6100 kcal/kg


Plant visit was made,boiler operating data,fuel input were

collected and analyzed


Boiler data:

Boiler operating capacity : 37.5 TPH

Steam pressure : 68.007 ata


Feed water temperature : 122°C

Flue gas temperature leaving APH : 132°C

O2 in flue gas is : 4%


Fired fuel analysis and efficiency

GCV : 3950 Kcal/kg

Moisture : 31.50%

Efficiency achieved : 81.7%

Reasons for lower Efficiency:

Excess fired fuel moisture comparing to design fuel

moisture

Lower GCV of fuel comparing to design

Loss in efficiency due to the above is 3.501%


Conclusion:

Corrected efficiency is 85.2%

Fuel moisture to be controlled for achieving the

guaranteed thermal Efficiency of the boiler

Expected Fuel saving by controlling moisture is 7.6 TPD


Case study II :

Reported issue:

Excess steam temperature drop


Plant design details:

Plant capacity : 1 X 8 MWe

Boiler capacity : 40 TPH



Steam temperature at boiler O/L : 495 °C


Steam temperature at T/G I/L : 470°C

Fuel GCV as fired : 3950 Kcal/kg

Boiler efficiency : 82 %


Observation:

Design Steam temperature drop : 5°C

Excess Steam temperature drop : 20°C

Excess energy loss by steam : 1.5 TPD

Considering 335 days operation the : 502 MT/year

excess fuel consumption.


Conclusion:

Steam line insulation to be rectified.

Steam traps in steam line to be set right.


Case study III :

Reported Issue:

Low thermal Boiler efficiency


Design data:

Plant capacity : 1 X 8 MWe

Boiler capacity : 40000 kg/hr





Feed water temperature : 126 ° C


Air temperature at APH I/L : 40°C


PG TEST DATA:

Power generation : 1 X 8 MWe

Boiler capacity : 37,500

kg/hr




Air temperature at APH I/L : 38°C


Achieved boiler efficiency with : 82 %

Imported coal

% O2 in flue gas : 4.5%


Parameters after 12 months of PG test:

Power generation : 8 MWe

Boiler capacity : 38,000 kg/hr


Steam temperature : 495 ° C


Flue gas temperature after APH : 159 ° C

% O2 in flue gas : 4.5%


Results:

Due to increase of flue gas temperature the following

losses have been increased.

1) Dry flue gas loss.

2) Loss due to moisture in flue gas.

3) Loss due to hydrogen in flue gas.

4) Air moisture loss.


The overall thermal efficiency reduction is 2%.

Equivalent coal consumption : 4878 kg/day.

Considering 335 day operation : 1635 MT/335day

Coal consumption

Reason:

Fouling in the cold air side of APH due to high moisture

content imported coal .

Rectification:

Periodic inspection and cleaning APH by water Jet.


CASE STUDY-IV

POWER REDUCTION OF BOILER FEEDWATER PUMP


Boiler Details

Boiler capacity : 140 Tph

Steam pressure : 86 kg/cm² (g)

Drum pressure : 98 kg/cm² (g)

Steam temperature : 510°c

Fuel : Baggasse

Type of firing : Traveling grate


Boiler Feed Pump Details

Feed pump capacity : 92.1 Cum/hr

Head : 1231 mwc

Speed : 2980 rpm

No.of pumps : 3 (2w + 1s)

Pump driven by : Motor with VFD

Drum level control by : FCV


Existing operating data

Feed water flow : 144 M3


Control valve opening : 35%

Pump operating speed : 2900 rpm

Feed water suction pressure : 3.5 kg/cm²

Feed water delivery pressure : 138 kg/cm

Power consumption : 790 Kw (2 pumps working)


Initially boiler feed pump was operated at constant

speeds of around 2900 rpm and drum level control was

operated by varying the feed control valve with three

element level control .


MODIFIED DATA :

Feed water flow : 144 m3/hr


Control valve opening : 100%

Pump speed : (2675 – 2700 ) rpm

Power : 660 kw (2 pumps working)

Power saving : 790 – 660 = 130 Kw

Drum level control was implemented by VFD operation of the

feed pump .The feed control valve was kept 100 % open and

system pressure drop has been reduced from boiler feed pump to

economizer . Based on the drum level VFD speed was varied in

automatic control.


CASE STUDY-V

FD fan motor power consumption reduction


FD Fan Power Saving with VFD

Boiler Capacity : 40 TPH


Steam Temperature : 485 +-5 Deg CEL

Type of boiler : AFBC

FD fan motor : 250kW

Speed : 1440 rpm

Fuel : Imported coal



Initially FD fan was operated without VFD and

the details of operating data are given

Steam generation : 37.5 TPH

Power generation : 8 Mwe

FD fan damper opening : 38%

Fan speed : 1440 rpm

Power consumption : 195kW

O2 in flue gas : 4%



Data after implementation of VFD for FD fan

Steam generation : 37.5 TPH

Power generation : 8 MWe

FD fan damper opening : 100%

Fan speed : 1250 rpm

Power consumption : 160kW

O2 in flue gas : 4%



Pressure drop in the damper has been eliminated by

damper full open and the power saving was

achieved through speed control

Power saving : 35kW / hr

840 kW/Day

281400kW for 335 days



Fuel saving (Plant heat rate of 4050Kcal/kWh

and fired GCV of fuel is 3950 Kcal)

---861 kg/day

--- 26 MT / month

--- 312 MT / year

---12.5 lakhs per annum


Any questions please?

Thanks

“CVL”

Documents

Trouble Shooting of Boilers