Travelling grate Boiler cold start up procedure

 

1.Objective:

This document is created to provide enough information to operation team for or carrying out the Boiler cold start up activity safely and smoothly.

2.Equipment details:

Make: XXX

Working pressure/Temperature: 110 kg/cm2/545 deg C

Capacity: 115 TPH

 3.Responsibility:

Shift In charge, Control room engineers and Boiler operators

 4.Recommended Safety PPEs:

Safety shoes, safety helmet, Face shield, Safety goggles, Boiler apron, hand gloves, ear plugs

 5.Tools/resources required:

 Fire wood, charcoal, diesel and pocking rods, walkie- talkies, Bagasse, coal, tractor dozers, JCB etc

 6.Man power required:

Shift In charge, Boiler Control room engineer, Boiler 1^st class and 2^nd class operator, Ash handling operator, Bunker/Silo operator, Fuel yard operators, Mechanical technicians unskilled labours for Boiler and supporting E&I engineer/Technician.

 

7.Potential Hazards Identified:

Back fire, flue gas leakage, steam & hot water leakages, employees over confidence, poor housekeeping, miss communication, slip/trip, entanglement, explosion/burst etc

 

8.Safety Checks and precautions:

• Ø  Ensure all the required competent man power is available and are using job related specific PPEs.
• Ø  Ensure all the resources are available.
• Ø  Ensure adequate illumination at all the operating/working areas.
• Ø  Ensure proper ventilation at all the operating/working areas
• Ø  Ensure no any slippery area or accumulation of water at all the operating/working areas
• Ø  Ensure no walkway/road blocks
• Ø  Ensure proper housekeeping at all the operating/working areas
• Ø  Ensure firefighting system/appliances is healthy and ready to use on immediate requirement
• Ø  Avoid use of mobile while working
• Ø  Ensure all the rotating parts of equipment are guarded fully
• Ø  Ensure all the hot surfaces of the Boiler are insulated properly
•  
• 9.Pre-start up checks-I
• Ø  Ensure all maintenance activities on Boilers are completed & work permits are closed and equipment are normalised for operation.
• Ø  Ensure all equipments pre-start up trials conducted and are healthy to operate continuously.
• Ø  Ensure Boiler’s all man hole doors (Furnace, super heater, bank zone, drum, economiser, plenum hopper, furnace front hopper etc) are closed.
• Ø  Ensure Boiler thermal expansion pointers are available at all the desired locations and their initial readings are okay.
• Ø  Ensure ESP and APH man hole doors are closed.
• Ø  Ensure all safety valves Gags are removed.
• Ø  Ensure steam drum vent, super heater vents and drains are open
• Ø  Ensure start up vent MOV is open and control valve is closed initially
• Ø  Ensure water wall headers all drains are closed
• Ø  Ensure main steam stop valve and bypass valves are closed
• Ø  Ensure IBD & CBD root valves are open and MOV valve is closed
• Ø  Ensure DM water pump is healthy and its valve to Deaerator is open for initial make up.
• Ø  Ensure HP & LP dosing pumps are healthy and their discharge valves to steam drum and Deaerator are open.
• Ø  Ensure Deaerator inlet steam line valve is closed
• Ø  Ensure deaerator vent line valve and vacuum breaker valves are open
• Ø  Ensure Deaerator outlet to BFP inlet valve is open
• Ø  Ensure all BFPs suction valves are open and discharge valves are closed
• Ø  Ensure all BFPs are healthy to start on immediate requirement
• Ø  Ensure feed control stations (30% and 100%) isolation valves and MOVs are open and control valves are in closed condition.
• Ø  Ensure attemperator isolation valves are open and control valve is in closed condition
• Ø  Ensure Bagasse screw feeders and extractors are heathy and their pre-trial is done
• Ø  Ensure coal spreaders bearing cooling water lines inlet & outlet valves are open
• Ø  Ensure FD & SA air dampers to furnace and OFA ducts are open and are set at desired positions.
• Ø  Ensure instrumentation & service air compressors are healthy and ready for immediate use.
• Ø  Ensure maintenance activities on AHP are completed and ready to take in service
• Ø  Ensure ESP hopper heaters and insulator heaters are ON
• Ø  Ensure APH bypass damper is open and main damper is partially or fully closed
• Ø  Ensure Coal handling plant and Bagasse handling plants are healthy and their interlocks tests are conducted and found okay.

 

10.Pre-start up checks-II

Tank level

• Ø  Ensure Drum level is 40-50%
• Ø  Ensure Deaerator level is 65%
• Ø  Ensure Feed water tank level is 70-80%
• Ø  Ensure DM water storage tank levels are 80-90%
• Ø  Ensure cooling tower level is 80%
• Ø  Ensure tank levels showing in are matching with local gauge glass levels.
• Ø  Ensure feed water parameters are normal

 

Fuel

• Ø  Ensure abundant Bagasse/coal is available at yard
• Ø  Ensure Bagasse/coal parameters (Moisture, Ash & GCV) are normal
• Ø  Ensure bagasse silos are full and silo gates are open
• Ø  Ensure coal bunker level is 80-90%
• Ø  Ensure tractor dozers and JCBs are available at yard
• Ø  Ensure Diesel level at DG tank is 90-95% and another 3000-4000 litres diesel is available for immediate top up
• Ø  Ensure Diesel transfer pump is healthy and running normal

 

11.Boiler start up Procedure

• Ø  Stack fire wood/ baled bagasse inside the furnace for light up
• Ø  Start ACWP pump and ensure all the parameters like discharge water pressure, bearing vibrations, temperature etc are normal
• Ø  Start the Instrumentation air compressor and ensure all the operating parameters are normal by evidencing loading and unloading pressures are as per desired.
• Ø  Start service air compressor and ensure all the operating parameters are normal
• Ø  Start the ESP rapping system
• Ø  Start the ash handling system
• Ø  Start the coal spreaders
• Ø  Start the Sub merged belt conveyor (SMBC) and ensure enough water level in conveyor trough.
• Ø  Fire the fire woods and slowly rise the furnace temperature up to 175-200 deg C
• Ø  Start Bagsse handling system and maintain silo levels 100%
• Ø  Start ID fan at 10% reference followed by FD & SA fans and ensure balanced draft in furnace i.e + or – 2 to 3 mmwc and ensure fans operating parameters (Bearing vibration & temperature) are normal.Note that, initially one stream of fans shall be started and second stream shall be started once boiler reached at rated main steam pressure and temperature.
• Ø  Ensure SA fans static pressure at discharge is 400-450 mmwc initially and increase gradually based on fuel feeding.
• Ø  Start CR fan and maintain discharge static pressure 350-400 mmwc
• Ø  Start fuel feeding system, start bagasse screw feeder followed by bagasse extractor at 5 to 10% reference initially
• Ø  Gradually go on increasing the furnace temperature by increasing fuel feeding slowly.
• Ø  Based on fuel feeding, gradually rise ID, FD & SA fans speed and always ensure balanced draft in furnace.
• Ø  Keep continuous communication with Boiler field team and get the feedback on combustion in furnace.
• Ø  At drum pressure 2 kg/cm2 close drum air vent valves
• Ø  At steam pressure 3 to 5 kg/cm2, close all the super heater air vent valves.
• Ø  Start HP & LP dosing system and ensure operating parameters (Discharge pressure, flow & tank levels) are normal.
• Ø  Start rising the Boiler pressure and temperature as per OEM given start up curve.
• Ø  Keep crack open CBD valve
• Ø  If drum level is coming down, start the BFP and maintain the drum level. Initially maintain the drum level through single element (30%) control valve and keep it in manual mode.
• Ø  If drum level increases, give blow down through IBD. Note that, during start up drum level can be maintained in the range of 30 to 80%. Do not allow to cross drum level > 85%
• Ø  At 5 to 7 Kg/cm2 main steam pressure, close the primary super header drain valves.
• Ø  At pressure 7 to 10 kg/cm2, stop the firing & give blow down through IBD and water wall bottom headers for 1 mi. Ensure normal drum level (40-50%) during blow downs.
• Ø  At 7 to 10 Kg/cm2 main steam pressure, close the secondary super header drain valves.
• Ø  At 10 to 15 Kg/cm2 main steam pressure, open start up vent control valve 10% and then close the radiant super heater header drain valves.
• Ø  Gradually open the start-up vent control valve as per requirement to ensure minimum cooling steam flow through super heater coils and also to rise the main steam temperature
• Ø  Always ensure that, minimum cooling steam is flowing through the super heaters when Boiler is under firing.
• Ø  Keep on noting down the Boiler all headers thermal expansion readings at various temperature and pressure. And escalate if thermal expansions found non-uniform.
• Ø  Ensure Ash is discharging from all the hoppers (Plenum, Economiser, APH and ESP hoppers)
• Ø  Ensure bearing vibrations of BFP and fans are normal.
• Ø  Ensure fuel feeding and handling system are running normal.
• Ø  At 40-45 kg/cm2, gradually open the main steam by pass valve and start to charge the main steam line.
• Ø  Check and confirm the steam and water coming out from main steam drain lines.
• Ø  Gradually increase the main steam pressure and temperature and open main steam stop valve slowly (MSSV) after ensuring steam line has heated up and condensate has been removed completely. Note that, before opening MSSV, pressure at inlet and outlet of the valve is almost equal, this helps for easy operation of the valve
• Ø  After opening MSSV, close by pass valve.
• Ø  After ensuring proper charging of the main steam line, give clearance to Turbine engineer for vacuum pull up and other start up activities. And open the MSSV as per their requirement.
• Ø  Increase the main steam pressure and temperature up to rated parameters i.e pressure 110 kg/cm2 and Temperature 545 deg C
• Ø  At rated pressure and temperature, start the second stream of fans i.e ID, FD & SA fans & ensure fan & motor’s bearing vibration and temperatures are normal.
• Ø  When boiler steam flow reaches more than 30% of its MCR, close the start-up vent control valve.
• Ø  Charge ESP at inlet flue gas > 120 deg C
• Ø  After normalisation of start-up, once again ensure all equipment bearing vibration and temperatures are normal and there not exist any abnormality.
• Ø  Take drum level controller in Auto mode.

9-Functions of Boiler steam drum

A steam drum is a crucial component in many types of boilers, particularly in water-tube boilers. Its primary function is to separate steam and water to ensure the proper operation and safety of the boiler. Here are the main functions of a steam drum in a boiler:

1-Steam-Water Separation:

One of the key functions of the steam drum is to separate steam from the water in the boiler. When water is heated in the boiler's tubes, it turns into steam. The steam drum provides a space where this separation can occur. Steam, which is lighter than water, rises to the top of the drum, while water remains at the bottom.

2-Steam Storage:

The steam drum acts as a reservoir for steam, providing a buffer to ensure a continuous and steady supply of steam to the downstream processes or turbines. This helps maintain a more stable and consistent steam output.

3-Water Level Control:

The water level in the steam drum needs to be carefully controlled to ensure safe and efficient boiler operation. Control systems are used to maintain the desired water level within a specific range. If the water level falls below or rises above the recommended range, it can result in operational problems, including overheating, tube damage, or even a dangerous situation known as "dry-firing."

4-Pressure Control:

The steam drum also plays a role in controlling the pressure within the boiler. Pressure is maintained by controlling the rate at which steam is released from the drum to meet the demand of the system. A safety valve is typically installed on the steam drum to release excess pressure to prevent over-pressurization.

5-Steam Quality Improvement:

The steam drum helps in improving the quality of the steam. By allowing time for the separation of water droplets from the steam, it ensures that the steam leaving the drum is of a higher quality with fewer moisture content and impurities.

6-Blowdown Collection:

Impurities and sediment tend to accumulate in the bottom of the steam drum over time. The blow down process, where a portion of the water is periodically drained from the bottom of the drum, helps remove these impurities, maintaining the boiler's efficiency and reducing the risk of scale and corrosion.

7-Heat Storage:

The steam drum can also act as a heat storage unit, helping to stabilize temperature fluctuations in the system. It can store excess heat, releasing it as needed to maintain a consistent steam temperature.

In summary, the steam drum in a boiler is a critical component that ensures the efficient and safe operation of the boiler. It facilitates the separation of steam and water, provides storage for steam, controls water level and pressure, and contributes to the quality and stability of the steam produced. Proper maintenance and control of the steam drum are essential for boiler safety and performance.

8-Sudden Load Changes:

During sudden changes in steam demand or load, the steam drum provides a buffer for the system. It can release additional steam or absorb excess steam, helping to stabilize the pressure and ensure a continuous supply of steam to meet the load requirements.

9-Temperature Control:

The steam drum can help control the temperature of the superheated steam leaving the boiler. By adjusting the feed water flow rate and temperature, the drum can help maintain the desired steam temperature for specific industrial processes.

Overall, the steam drum is a critical component of a boiler system, responsible for maintaining steam quality, pressure, and water levels to ensure safe and efficient operation. Proper control and maintenance of the steam drum are essential for the longevity and performance of a boiler.

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