CFBC Boiler Startup - Load Operation - Shutdown
CFBC Boiler Startup - Load Operation - Shutdown
CFBC Boiler Startup - Load Operation - Shutdown
ABSTRACT
FIRST
TIME
CFBC
BOILER
STATRTUP
PROCEDURE,SHUT
DOWN
PROCEDURE
,
LOAD
OPERATION,INCREASING
AND
DECREASING THE LOAD OF BOILER
ASHVANI SHUKLA
CFBC BOILER STARTUP & OPERATION
Internal
Recirculation-Circulating
BY
ASHVANI SHUKLA
(C&I) RELIANCE
Fluidized
Bed Combustion
(IR-CFBC)
OPERATION
COLD STARTUP
LOAD OPERATION
SHUTDOWN PROCEDURES
COLD START-UP
Line up the water and steam side valves as per the startup requirement.
Line up all the dampers in air and flue gas path as per cold start up
requirement.
Verify the burner and associated systems are ready for operation.
Ensure the DCS and all the electrical systems are lined up for normal
operation
COLD START-UP
DP TEST:
Purpose
To reconfirm the DP across the bubble cap as per the design limits
at various air flow conditions.
Pre-Requisites
Verify the bubble cap for any physical damages or any blockages and
replace the damage bubble cap if any and clear the blockage by pinning.
Verify the floor panel seal welding for any cracks /damage and rectify the
defect if any.
Ensure that the manhole doors / Inspection doors are properly secured and
tightened on the air / gas ducting.
COLD START UP
PROCEDURE:
Note down the Wind box and bubble cap cold DP Corresponding to
60% & 100% MCR air flow.
COLD START-UP
BED MATERIAL FILLING:
Note:
Bed material size and chemical property must be maintained strictly as per
the specification for smooth start up and efficient operation.
Procedure:
Ensure the isolation gate above and below the Rotary feeder are open
Switch ON the rotary feeders at bed material bunker outlet and operate it at
minimum speed and start filling the bed material to the furnace.
Bed material shall be filled up to 600 mm heights above the bubble cap,
which is to be verified physically.
Record the minimum fluidization wind box pressure and PA air flow as these
are the guiding parameter during Cold startup.
COLD START-UP
BURNER:
PRE- START-UP CHECKS FOR BURNER
Opening/closing of combustion damper for all the burners are smooth with
complete travel.
Verify cooling air to scanners and peep holes are available as per the
recommendation.
Verify the operation of Natural Gas control valve opening and closing.
Maintain the rated Natural Gas pressure at Main fuel trip valve (MFT) inlet.
COLD START-UP
FURNACE PURGING:
Whenever the Pre interlocks are satisfied, the system is Ready for
purging and is indicated by the glow of lamp Purge ready to start.
Initiate the Purge start from DCS. At this stage Purge in progress
indication will appear. After the pre set time i.e. 5 minutes
Purge complete indication will appear.
MFT Reset:
COLD START-UP
NATURAL GAS FIRING
Burner ready to start indication will appear. Initiate burner start command to the
selected burner.
Whenever the burner start command is initiated the Following actions takes place.
Start up burner and Igniter gun assembly is inserted.
Ignition transformer energises & pilot gas shut off valve opens.
Ignition transformer will get de-energised after 5 seconds, after issuing the start
command.
Pilot flame is sensed by the flame scanner and the individual NG Shut off valves
will open and corresponding vent valve will get close.
Main flame is detected and fuel gas solenoid valve remains open in the circuit
& operation of the particular burner continues.
If the burner is stopped manually by STOP push button or tripped for
quenching of fire. Purge required signal will energised automatically.
COLD START-UP
CAUTION:
If the burner fails to light up, find out the cause of failure.
COLD START-UP
BOILER PRESSURING:
Increase the burner NG pressure by increasing NG flow to increase
the boiler pressure.
Maintain the furnace pressure around -3 to 5 mmH2O.
Maintain normal water level in Drum.
Whenever the steam drum pressure reaches about 2kg/cm2, close
the steam drum vent valve.
Whenever the pressure reaches to 3 kg/cm2 close the super-heater
header drains wing wall drain valves and SH enclosure panel drain
valves.
Intermittently fluidize the bed at regular intervals, so as to avoid over
heating of bed material.
COLD START-UP
CAUTION:
Firing rate to be adjusted in such a way to maintain the
Flue gas temperature at U beam inlet at 500c till 20% of
MCR steam flow is established.
Monitor and maintain the steam drum metal differential
temperature at 25C by modulating the firing rate.
COLD START-UP
COAL FIRING:
Whenever the Bed temperature reaches around 6000 C initiate the coal firing.
Prior to start the fuel feeders ensure seal air to the Coal feeder & Coal feed pipes
are open and maintain the required pressure.
Start two Drag Chain feeders & Gravimetric feeders (One from RHS and one
from LHS).
When Bed temperature will start increasing steadily after coal firing and O2 level
in Flue gas start reducing then continue the coal feeding.
Monitor the bed temperature raise closely, whenever the bed temperature
reaches 750 Deg C, Start the third DCF & gravimetric feeder at minimum coal
flow.
After reaching the bed temperature around 800 Deg C, Switch off the over bed
burners one by one gradually.
Raise the Boiler pressure up to rated pressure in accordance with the enclosed
Boiler Cold start up pressure raising curve.
IR-CFBC CONCEPT
COLD START-UP
CAUTION: - After switch off the burner, to cool the burner components
exposed to high temperature and to avoid back shifting of bed material
into burner wind box and air ducting sufficient air pressure has to be
maintained at the burner wind box.
CAUTION:
COLD START-UP
STEAM LINE CHARGING FOR FIRST BOILER:
Whenever the drum pressure reaches near the operating pressure make
preparation for charging the main steam piping and other distribution
lines.
Maintain the drum pressure 10 -15 Kg/cm2 below the operating pressure
till the steam line is charged.
Open the by-pass valve of the main steam stop valve to warm up the
Main steam line.
Open Main Steam Line isolation manual valve and then gradually open
the MSSV and close the MSSV by-pass valve after the MSSV is fully
open.
Keep the start-up vent valve open till the steady flow of steam (> 30%) is
ensured from the end users.
LOAD OPERATION
CAUTION:
While loading the boiler, feed & boiler water parameters should be in
recommended limit before increasing the steam flow beyond 50% of
MCR.
While increasing the firing rate always increase the air flow first and
then increase the fuel.
While loading the boiler, following conditions are to be ensured to achieve the
desired output.
LOAD OPERATION
OPERATION:
Bed dP, lower and upper furnace shaft dP must be maintained as per load
demand.
Mode of Operation
During low load operation i.e. < 60% MCR, the boiler operation may be semi
CFBC mode. Along with the increase in load i.e. > 60% MCR, the combustion
mode shifts to CFBC mode.
Load ramp up - Raise the load gradually but not more than 3% of MCR/ minute.
During load ramp up sufficient quantity of inventory is made available to control
the bed temperature fluctuations beyond safe limit.
OPERATION CONTROLS
BED TEMPERATURE CONTROL:
Bed temperature is a function of
Operating load
Excess air
Moisture in fuel
OPERATION CONTROLS
10
20
30
40
50
60
70
80
90
100
OPERATION CONTROLS
O2 level Curve
20.00
18.00
16.00
O 2 l ev e l i n %
14.00
O2 Level
12.00
10.00
8.00
6.00
4.00
2.00
0.00
0
10
15
20
30
40
50
60
Steam Flow in %
70
80
90
100
OPERATION CONTROLS
SOLID INVENTORY CONTROL:
The solids inventory control comprises two interrelated components:
OPERATION CONTROLS
Furnace Inventory Control
870 TO 950
900 to 970
FURNACE dP PROFILE
220 to 260
700 to 750
380 to 390
Adjust the primary & secondary air flow to suit the steam flow and bed
temperature.
CAUTION:
HOT START UP
Note:
Wind box needs to be purged with steam as per the Wind box
steam purging procedure. However air purging is not required if
average bed temperature is 600/750 Deg C.
HOT START UP
Below mentioned sequence to be followed to bring back the boiler into service during
hot startup.
Drain the bed through the bypass gate up to no unburnt coal is observed in the
bed.
Start the ID Fan, PA Fan and SA fan as per start-up sequence described in boiler
cold start up procedure
Bring back all the Fan and fuel feeder drives to the minimum speed/flow setting.
In case, bed temperature drops below 600/750 deg C, gas Burner support can be
taken.
Raise the boiler pressure to the rated pressure as per Hot pressurization curve.
Whenever the boiler rated pressure is attained, connect the boiler to CSDH as per
procedure describe in Manual.
Pressure. (Ata)
10
12
14
16
18
20
22
24
26
28
30
32
34
36
38
40
Time in min
Drum Pressure 70 -143 Ata
WARM START UP
WARM START UP:
Average Bed Temperature 600C (Indonesian/ Indian coal)
Average Bed Temperature 750C (Petcock)
OR
Average Bed Temperature 200C
After boiler tripping, if average bed temperature is <600/750 Deg C and
200 Deg C, boiler cannot be started directly with solid fuel feeding.
Note:
Wind box needs to be purged with steam as per the Win box steam
purging procedure. Apart from steam purging, Furnace purging also
need to be carried out as per Furnace Purging Procedure.
WARM START UP
Following sequence may be followed to bring back the boiler into service.
After completion of wind box steam purging, normalize the Dampers in air and gas
circuit.
Adjust the gas flow and airflow to raise the bed temperature.
Once the required bed temperature is attained, initiate the solid fuel firing as per
the procedure.
Whenever the boiler rated pressure is attained, connect the boiler to CSDH as per
procedure describe in manual.
BOILER SHUTDOWN
Boiler shut down can be of two types:
Planned / Normal shut down where the operator gets advance notice and
adequate time to shut down the boiler in an orderly manner.
Normal Shutdown:
Adjust the coal and air flow as per the steam flow.
When the load is reduced below 30 % of MCR, stop the fuel feeders
Stop the fans whenever the bed temperature reduced below 200 deg C Fan
stopping sequence is SA, PA and ID.
When the U Beam temperature is reduced below 500 deg. C Close the startup
vent valve.
BOILER SHUTDOWN
Stop the limestone/ make up bed material & MDC ash recycle rotary feeder.
Maintain the PA fan air at all locations to prevent solids sifting back.
Switch off the ESP transformer whenever the backend temperature drops
below 125C but keep the heaters and the rapping system in service.
Whenever the steam drum pressure drops to 2-kg/cm2 (g), open the start-up
vent
BOILER SHUTDOWN
Typical Indicative Curve for Boiler Forced Shutdown
160.0
140.0
Using high temp FW, increase water level to 6" below top of
drum and hold between 6" and 12" until zero pressure
120.0
100.0
80.0
60.0
40.0
n high
water level
until ze
press. is
20.0
0.0
0
30
60
90
120
150
180
210
Time in minutes
240
270
300
330
360
390
BOILER SHUTDOWN
CAUTION:
If personnel need to enter the unit, all solids must be removed completely from the
boiler including the furnace, U-Beam zone, super heater pass floor, MDC hoppers,
and ESP and wind box.
If the unit is shut down for a short period of time, store the solid inventory in the
MDC ash hopper and furnace.
EMERGENCY SHUTDOWN
Emergency shutdown is initiated as a result of equipment failure OR due to
MFT conditions.
Loss of Feed water supply - Boiler feed pump system is not available.
Loss of fan PA/ SA fans and/or induced draft (ID) fan are not available.
Loss of both water supply and draft - Black plant with the boiler trip
and isolated from the power grid, with only emergency power available.
This is the most important emergency situation.
Loss of solid fuel feed to furnace- If draft and feed water supply
equipment remain in service, this situation may be resolved quickly
enough to prevent emergency shutdown.
EMERGENCY SHUTDOWN
Emergency Response Actions and Priorities:
Following actions need to be taken for emergency situations:
During black plant condition establish steam flow through the startup vent and
bleed steam vents quickly to prevent safety valve lifting and loss of water.
Boiler tripping due to loss of feed water supply, immediate response should be to
restore feed water supply to maintain the safe water level; if not in the normal
operation range, at least up to the minimum visibility of drum direct level gauge glass.
Target is to restore a water feed to the drum within 5 to 7 minutes of the trip.
EMERGENCY SHUTDOWN
NOTE:
FUEL ANALYSIS
Fuel Ultimate Analysis
PETCOKE
PARAMETERS
INDONESIAN COAL
UNIT
Nominal
Nominal
Minimum
Maximum
CARBON
% by wt.
80.70
51.45
38.1
53.7
HYDROGEN
% by wt.
3.71
3.18
2.7
3.6
NITROGEN
% by wt.
1.37
1.04
0.6
1.1
OXYGEN
% by wt.
1.69
12.89
11.5
14.8
SULPHUR
% by wt.
7.33
0.70
0.1
0.7
MOISTURE
% by wt.
5.00
25.0
25.0
35.0
ASH
% by wt.
0.20
5.74
1.3
5.8
TOTAL
% by wt.
100
100
CV (HHV)
Kcal/kg
7895
4774
3539.7
5100
FUEL ANALYSIS
Fuel Ultimate Analysis
INDIAN COAL
PARAMETERS
UNIT
Nominal
Minimum
Maximum
CARBON
% by wt.
37.70
32.5
43.0
HYDROGEN
% by wt.
2.64
2.1
2.8
NITROGEN
% by wt.
0.84
0.6
0.9
OXYGEN
% by wt.
8.40
4.1
8.7
SULPHUR
% by wt.
0.42
0.3
0.5
MOISTURE
% by wt.
10.0
7.0
16
ASH
% by wt.
40.0
35
45
TOTAL
% by wt.
100
CV (HHV)
Kcal/kg
3600
3000
4100
Range
Silica
60-70%
Al2O3
25-30%
FeO
1-1.5%
TiO2
1-2.0%
MnO
Traces
CaO
0.54
MgO
0.23
P2O5
0.08
Na2O
0.22
K2O
0.45
< 500
100 %
< 400
90 %
< 300
60 80 %
< 250
10 %
< 140
0%
LIMESTONE
LIMESTONE SPECIFICATION:
Limestone sizing also affects consumption rate. Excessive course material can
cause increased bed drain rates and excessive fines can increase carryover
losses. The sizing should be as follows:
U.S. Mesh
micron
Percentage Passing
20
840
100 %
30
590
85 95 %
50
300
65 85 %
70
210
25 55 %
100
150
10 30 %
140
100
10 15 %
200
75
0%
UNIT
PPM
PPM
PPM
PPM
PPM
PPM
PPM
FEED WATER
<0.003
9.3-9.6
0.007
0.01
0.002
0.01
Nil
Nil
Nil
Nil
PPM
Nil
s/cm
0.2
PPM
Nil
PPM
Nil
PPM
PPM
0.02
0.2
UNIT
BOILER WATER
PPM
Nil
9.0 - 10
PPM
PPM
PPM
PPM
PPM
PPM
PPM
0.14
Nil
Nil
50
1
Nil
s/cm
Residual Disodium
Phosphate(Na2Po4) (Max)
PPM
PPM
Oil (Max)
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