BOILER & AUXILIARIES START-UP (COLD-START)

BOILER & AUXILIARIES START-UP (COLD-START)
INITIAL CONDITION:
Boiler is depressurised condition.
Boiler is filled up to the normal level.
All boiler auxiliaries are cleared for operation.
CC pumps cavities are filled.
LINE-UP:
The following systems/ equipments should be lined up and made ready for operation:
Aux. PRDS Steam system.
Fuel oil-handling system.
Instrument air system.
Plant air system.
Equipment cooling water system.
All three CC pumps: Cavity filling completed and discharge valves are kept open.
Both secondary and primary air heaters with associated dampers.
Both ID fans should be ready and lined up.
Both FD fans should be ready and lined up.
AC and DC scanner air fans.
SCAPH for primary and secondary air heaters.
Both PA fans should be ready and lined up.
Mills: Those required for full load operation should be made ready and which are not available should be isolated.
Coal feeders.
Both seal air fans.
Electrostatic precipitator.
Pent house pressurizing fan.
Soot blowing system – for air heaters.
Furnace temp. probes.
Water / steam sampling system.
The equipments readiness can be ensured by complying with the Recommissioning
checklists.
3.0 CHARGING OF SYSTEMS:
3.1 Charge aux. Steam to the boiler (from running unit or aux. Boiler). Ensure proper draining of the lines before charging. Aux. Steam for oil heating, oil lines tracing, atomizing steam, air heater, soot blowers and steam coil air heaters should be made available.
3.2 Start instrument air compressors and charge instrument air to boiler, turbine,auxiliaries and off-sites.
3.3 Start plant air compressors and charge plant air igniter cooling, air heater, air motors and other cooling/cleaning requirement.
3.4 Start equipment cooling water pumps and charge the coolers for all equipments.
3.5 Charge HF up to the burner front and keep it on long recirculation.
4.0 PRESTART CHECKS:
Fill the Boiler cold start-up checklist and get the deviations approved by the competent
authority.
5.0 START-UP:
The sequences of starting of the equipments are given below. For details refer to the
standard operating procedure of the individual equipment.
5.1 Start two CC pumps one by one and keep them in service. Check for the differential pressure and ensure that it is normal. Drum level has to be maintained high (about + 300 mm) before starting the pump and it should be maintained ‘Normal’ afterwards.
5.2 Start the secondary air heaters* one by one & keep the associated dampers open.
5.3 Start the primary air heaters one by one. Though it is not required as a purge permissive, it is better to keep them in service from the safety angle. Keep the gas outlet dampers closed, till air flow is established.
5.4 Start the first ID fan. Ensure that its suction & discharge dampers open to full. Also check for the closure of the suction / discharge damper / inlet vane of the other fan.
5.5 Gradually raise the IGV and then vane of the running fan and maintain a furnace draft of about –10mmwc.
5.6 Start the corresponding FD fan (if it is not available the other FD fan can be started). Ensure that the discharge damper of the running fan opens full and the blade pitch and discharge damper of the non-running fan closes full.
5.7 Gradually raise the load on the FD fan. Parallely control the IGV and vane of the running ID fan to maintain the furnace draft. (Ensure that the secondary air dampers are open and modulating). Raise the total air flow to more than 30% (630 tph), which is the purge requirement.
5.8 Put the wind box pressure control (aux. air dampers) in auto and maintain the desired wind box to furnace differential pressure.
5.9 Start the second ID fan. Ensure fuel opening of its suction and discharge damper.
5.10 Slowly raise the IGV and vane of the second ID fan and reduce those of the first ID fan to equalize the heading on both fans, always maintaining the furnace draft within limits.
5.11 Start the second FD fan. Ensure that its discharge damper opens fully.
5.12 Gradually raise the blade pitch of the second FD fan and reduce that of the first FD fan to equalise the loading on both fans maintaining the minimum air flow and normal furnace draft.
NOTE: If so desired, the second set of ID / FD fans can be started at a later stage (after
synchronization and auxiliary supply changeover) to reduce the auxiliary power
consumption and loading on station transformer. But keeping both the fans in service is
preferable from the operation flexibility point of view. It avoids tripping of the boiler on
protection in the event of outage of one fan and reduces the furnace disturbance at a later
stage while starting the second set of fans.
5.13 Put the furnace draft control in auto. However, the performance of the auto loop should be kept under observation during low load operation.
5.14 Start the AC scanner fan and keep it in service. Keep the other fan as auto standby. Ensure that the scanner air pressure is normal.
5.15 Charge the SCAPH of both FD fans. Regulate the steam flow to maintain the air heater cold end temp.
5.16 Close the HFO Trip Valve and Recirculation Valve (which were opened earlier for charging and warming up the oil lines – Refer Sec. 3.5). Open the Short Recirculation Valve.
5.17 After completing the above activities, ensure that the following Purge Permissives are satisfied and the ‘PURGE READY’ Light is ‘ON’:
1. All HFO nozzle valves are closed.
2. All mills are OFF.
3. No boiler trip.
4. All feeders are OFF.
5. All scanners sense ‘No Flame’.
6. All auxiliary air dampers are modulating.
7. Both PA fans are OFF.
8. All hot air gates are closed.
9. Air flow >30% and <40%.
10. HFO Trip valve is closed.
11. Wind box to furnace difference pressure is normal.
5.18 Ensure that the cold start-up checklist is completed in all respects and the deviations are noted.
BOILER LIGHT-UP:
5.19 Start the furnace purge cycle by depressing the ‘PUSH TO PURGE’ button. ‘PURGING’ light comes ‘ON’ and purging continues for 5 minutes (if the purge time is disturbed, it should be corrected).
5.20 If the purging is interrupted due to any reason (loss of one or more of the purge permissive), purging should be restarted.
5.21 On completion of purge ‘PURGE COMPLETE’ light becomes ‘ON’. MFT gets reset.
5.22 Open the HO Recirculation Valve and HO Trip Valve; close the Short Recirculation Valve.
5.23 Bring the HFO header pressure and temperature to normal value. Ensure that atomizing steam pressure is normal.
5.24 Ensure that Burner tilt is horizontal.
5.25 Select the oil burners to be fired. During cold start-up normally lower (AB) elevation oil burners are selected.
5.26 Give start command to the selected burner. It is preferable to start one burner at a time, by monitoring its performance at local. (Individual burner selection can be done by keeping its selector switch in Remote at local).
5.27 Check and ensure that the burner is firing properly. In case of poor flame or a leak, take out the burner immediately. Identify the cause and attend it.
5.28 After proving the first burner successfully select the next burner (preferably on the other side in the same elevation) and give start command. Ensure proper flame. Similarly all the four burners in the elevation (maximum) can be kept in service. Regulate the oil pressure.
5.29 Keep the furnace draft at normal values while cutting in oil burners.
5.30 Ensure that the auxiliary air dampers of the burners in service are open.
5.31 Check the chimney exit. If excessive black smoke is observed, adjust air flow.
5.32 Start Air preheater soot blowers. Check for any oil carry over with the help of oil carry over probe. Inspect the air heater through the inspection doors provided on the air side.
5.33 Maintain drum level within normal limits (+ 100mm). Keep economizer recirculation valve open when there is no feeding to the drum.
5.34 Monitor the boiler pressure increase and ensure that it is within allowable limits (It should not exceed a corresponding increase in saturation temp. of 100ºC/hr.).
5.35 At a drum pressure of 2kg/cm 2 close all SH vents and drains. Leave the start-up vents open.
5.36 Insert furnace temp. probe occasionally and ensure that the gas temp. is less than 540ºC.
5.37 Monitor the rate of increase of SH outlet temp. and ensure that it is within limits (less than 5ºC/min.).
5.38 Monitor the drum, SH and RH metal temp. and ensure that they are within limits. (Drum metal temp. raise should be within 2ºC/min.).
5.39 Start the dosing pumps and do chemical dosing as per Chemist’s advice. Open CBD as per the Chemist’s advice.
MAIN STEAM LINE CHARGING:
5.40 Do condenser vacuum pulling after making the associated system ready.
5.41 Ensure that MS, CRH and HRH line drains are open (turbine side) and system is ready for operation; turbine is on turning gear and stop/control valves are closed.
5.42 Ensure the readiness of HP/LP Bypass System.
5.43 When drum pressure reaches about 4 kg/cm 2 , start charging main steam line by gradually opening the bypass (warm up) valves of Boiler Stop Valves on both sides. {Ensure that the main valves are not in Auto. In auto the valves gets open command when the bypass valves are full open).
5.44 Open the Boiler Stop Valve Monitor the pressure rise of MS line bypass valves to full. Open HP Bypass warm-up valves to warm-up the CRH lines. Observe for any abnormality (like hammering etc.) in the system.
5.45 Open HP bypass valves partially and ensure that the pr. control valves, spray valves and the protection system is working properly.
5.46 Open HP bypass valves partially and ensure that the pr. control valves, spray valves and the protection system is working properly.
5.47 Monitor the pressure rise in the boiler. When the pressure exceeds 5kg/cm2, open Boiler Stop Valves and regulate HP Bypass Valves to control the pressure close start-up vents. Close HP Bypass worm-up valves.
5.48 Open LP Bypass Valves and keep it partially open at lower pressures. When the pressure improves control the LP Bypass Valve opening so as to maintain a pr. of about 12 kg/cm2 in the HRH.
5.49 When boiler pressure reaches 7kg/cm2, start the third CC pump and keep it in service.(NOTE: Pumps should not be started during intervals of rapid boiler water temp. change).
TURBINE ROLLING & SYNCHRONISING:
5.50 Raise the boiler parameters (by controlling the firing rate) as per the requirements of Turbine by following the allowable ramp rate.
5.51 At a main steam pressure of 15kg/cm2 and HRH pressure of 8-12 kg/cm2 reset the turbine (Refer Turbine start-up procedure).
5.52 At 50 kg/cm2 MS pressure, 12kg/cm2 HRH pressure and 350ºC MS/HRH temp. roll the turbine and synchronize the machine.
5.53 After taking block load, close HP/LP Bypass and keep it in auto with proper pressure set point.
5.54 Close CRH, HRH and MS drains. Ensure closing of MAL drains in auto.
5.55 Before the feed water flow to the boiler reaches the capacity of the low load line, one of the high capacity lines should be placed in service.
5.56 Economizer recirculation valves should be closed after establishing a constant feed water flow.
COAL FIRING:
5.57 Ensure that both ID / FD fans are in service and are equally loaded. Furnace draft control is put in auto.
5.58 Start the first PA fan. Ensure that its discharge damper opens in auto and the discharge damper of the other fan closes in auto.
5.59 Start the second PA fan. Ensure opening of its discharge damper. Load both the fans gradually and raise the PA header pressure to normal value. (PA fans should not be run without air flow for long duration)
5.60 Ensure that one of the seal air fans starts in auto. If not, keep it in service; keep the other fan as standby.
5.61 Open the gas dampers of the primary air heaters. Improve the primary air temperature.
5.62 Start the first mill (preferably bottom elevation) and keep it in service. Increase the loading gradually.
5.63 Keep the other mills in service as per the load requirement.
5.64 Gradually raise the steam parameters and unit load as per the start-up curves by observing TSE margins.