Procedure for Boiler Gauge glass line up & Flushing

Boiler Gauge glass: is a transparent glass of shape tubular, flat or square blocks fitted to the boiler steam drum to facilitate a visual indication of the water level of a steam drum. These types of glasses are manufactured by borosilicate glass which is robust, temperature & chemical resistant.

 

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Line up of Gauge glass:

• Ensure all tools & required PPEs are taken to operate the valves (Hand gloves, Safety goggles, “F” rods etc)
• Ensure steam & water side valve of gauge glass are healthy & operating properly
• Ensure there are no any leakages
• Ensure steam side & water side valves are closed
• Ensure gauge glass drain valve is open & drain is connected/extended to safe location
• Now crack open the steam valve & check for any leakages in gauge glass. Wait for some times until system heats uniformly.
• Then crack open the water side valve, wait for some time for stabilization
• Then close the drain valve
• Open the steam valve & water valve fully
• Observe water collected in glass & showing the level
• Cross check the level glass with other side level glass or control room transmitter reading or with Hydra step

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Flushing of gauge glass

Ensure all tools & required PPEs are taken to operate the valves (Hand gloves, Safety goggles, “F” rods etc)

Step-I

• Close the water side valve & open the drain valve for flushing, wait for some time
• Then close the drain valve & open the water side valve

Note: After opening the water side valve, water level should retain its normal operating level, if not then there might be blockages in valve or line

Step-II

• Close the steam side valve & open the drain valve for flushing, wait for some time
• Then close the drain valve & open the steam side valve

Note: After opening the steam side valve, water level should retain its normal operating level, if not then there might be blockages in valve or line

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10-tips to reduce LOI/unburnt in Boilers

 

 1-Optimization of fuel moisture in the fuel:

Higher moisture in the fuel leads to unbalanced draft in the furnace or combustion chamber. Which ultimately results into poor mixture of air & fuel, higher moisture fuel demands more excess air. So optimization of fuel moisture will help to reduction in LOI.

2-Maintaining balanced draft in furnace:

Unbalanced draft is nothing but more FD air/less ID draft or less FD air /More ID Draft.

More FD & less ID causes back fire & improper mixing of air & fuel.

More ID & less FD causes escape of fuel particles from furnace without proper combustion

3-Maintaining 3Ts of combustion:

3Ts of combustions are: Temperature, Time & Turbulence

Temperature: For proper combustion temperature of the furnace must be sufficient enough to burn the fuel completely.

Time: There must be sufficient time for combustion

Turbulence: There should be proper turbulence in furnace for proper mixing of air & fuel

4-Increasing the secondary air quantity & pressure:

This will help to increase the residence time of fuel in furnace resulting into complete combustion

5-Maintaining the required excess air:

Lesser excess air than required will lead to incomplete combustion that is conversion of carbon into carbon monoxide instead of carbon di-oxide. So sufficient air is required to achieve complete combustion.

6-Using correct or designed GCV of a fuel:

Read>>>>>>Why do high pressure Boilers have higher efficiency??

Lesser GCV fuel requires more air for combustion, even may not achieve the designed parameters of Boilers like flow, pressure & temperature.

7-Ultimate & Proximate analysis of fuel:

In order to achieve proper combustion, we must know the contents of fuel properly. Need to operate the Boilers at designed parameters of fuel. For example if FC of the fuel increases, then need to increase air & combustion time and need to reduce turbulence.

So it is very important to know the fuel contents.

8-Operating the Boilers at stable loads:

Stable loaded Boilers will not lead into much LOI, as air & fuel mixture is constant & will not vary frequently. LOI cannot be reduced in variable load boilers.

9-Operating the Boiler at little positive draught:

Operation of Boiler at positive draught will help for complete combustion. If boiler is operated at more negative draught, then there will be more chances of escaping of unburnt fuel particles from the furnace & causing secondary combustion at super heaters & other convective zones.

10-Reusing unburnt or cinder:

Generally unburnt/cinder from Boiler Bank & economiser zones are re-injected into furnace by using “Cinder re-injection” system. This will help in re-burning of cinder & reduction in LOI

 Procedure for Boiler Gauge glass line up

 

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16-Perfect reasons for more fuel consumption of Boilers

Following are the 16-reasons for increase in Boilers fuel consumption

1. Decreased economiser inlet feed water temperature:

On every 6-8 deg C decrease in Economiser inlet feed water temperature causes the rise in Boiler fuel consumption by 1%.

2. Increased Boiler outlet  flue gas  temperature:

On every 22 deg C increase in flue gas temperature causes the reduction in Boiler efficiency by 1% & hence boiler fuel consumption increases for generating same steam.

3. Increased moisture content in the fuel

Boilers fuel consumption increases as the moisture in the fuel increases. As it requires more excess air & reduces combustion efficiency leading to unburnt losses

4. Increased excess air

10-Tips to reduce LOI in Boilers

Increase in excess air causes dry flue gas loss & hence more fuel consumption. And also leads to more auxiliary power consumption.

5. Increased unburnt loss

Unburnt fuel or incomplete combustion of fuel leads to increased consumption of fuel. Unburnt is due to improper air fuel mixture or unbalanced draught or variation in the fuel quality

6. Higher blow down

Blow down water carries saturated water/steam through it, so leads into more fuel consumption. Maximum acceptable blow down rate for normal Boiler operation is 0.5 to 1%.

7. Operating the Boiler at lower or partial loads

Operating the Boilers on partial load requires more excess air & leads to incomplete combustion forming unburnts.

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8. Operating the boiler at non-standard operating parameters

Operating the Boilers at non standard parameters like pressure, temperatures, flow etc will lead to the higher fuel consumption

9. Leakage into & out of the Boilers

Air & flue gas leakages into the Boiler & out of the Boiler will reduce the working efficiency there by increasing the boiler fuel consumption

10. Steam leakage

It is a direct cause for higher steam consumption. Generally steam leakage is from vent & drains valves, welding & flange joints

11. Boiler heating surfaces internal scaling

Pressure parts namely water wall tubes, economiser tubes & super heater coils internal & external scaling will result into poor heat transfer, which increases fuel input to produce required amount of steam.

Pressure parts internal scaling can damage the pressure parts by over heating

12. Radiation & Convection losses

Radiation & convection losses in the boiler causes increased fuel consumption. These losses may be due to uninsulated or unlagged surfaces of boiler

13. Lower combustion air temperature

On every 20 Deg C decrease in combustion air temperature leads to Boiler efficiency reduction by 1%

14. More ash content in the fuel

More ash content in the fuel takes away heat associated with it during discharging through hoppers. Especially bed ash is having more temperature. Also higher ash fuel are having lower GCV

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15. More Volatile matters (VM) in the fuel

Calorific value of the fuel reduces as the VM increases. Boilers using Lower GCV fuel consume more fuel

16. Other potential reasons for increased fuel consumption of a Boiler are;

Boiler design related issuers

Wrong selection of auxiliaries like fans & fuel feeding system

Low quality of Bed materials

Defects in fuel burners & fuel spreaders

Over refractory on internal heating surfaces

Faulty field instruments

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Calculated reasons for increase in Turbine specific steam consumption

1. Lower vacuum

Turbine consumes more steam, if vacuum in condenser is maintained on lower side.

Example:  Consider a 20 MW Steam Turbine having Inlet steam parameters 65 kg/cm2 & 490 Deg C & Vacuum maintained in condenser is -0.9 kg/cm2.

Calculate the steam consumption of turbine at vacuum -0.9 kg/cm2 & -0.85 kg/cm2

A-Steam consumption Q at -0.9 kg/cm2 to develop 20 MW power

P =Steam flow X( Enthalpy of inlet steam-Enthalpy of exhaust steam)/ 860

Enthalpy of inlet steam at inlet steam parameters =810 kcal/kg

Exhaust steam enthalpy at -0.9 kg/cm2 vacuum = 619 kcal/kg

Then, 20 = Q X (810-619)/860

Q1 = 90 MT

B- Steam consumption Q at -0.85 kg/cm2 to develop 20 MW power

Exhaust steam enthalpy at -0.85 kg/cm2 vacuum= 623 kcal/kg

Then, 20 = Q X (810-623)/860

Q 2= 90.9 MT

It is clear that, Turbine operating at -0.9 kg/cm2 vacuum consumes lesser steam as compared to turbine operating at vacuum-0.85 kg/cm2

2. Lower inlet main stream pressure& temperature

Turbine operating at higher main steam pressure consumes lesser steam as compared to turbines operating at lower pressure

Example: Consider a 20 MW Steam Turbine having Inlet steam temperature 490 Deg C & Vacuum maintained in condenser is -0.9 kg/cm2.

A-Inlet steam parameters: Pressure: 65 kg/cm2 & temperature 490 deg C , Enthalpy = 810 kcal/kg

Exhaust steam parameters P = 0.9 kg/cm2 & Enthalpy = 619 kcal/kg

Steam consumption of Turbine Q = P X 860 / (Enthalpy of inlet steam-Enthalpy of exhaust steam)

Q = 20 X 860 / (810-619)

Q1 = 90.05 MT

B-Inlet steam parameters: Pressure: 87 kg/cm2 & temperature 515 deg C , , Enthalpy = 818 kcal/kg

 

Steam consumption of Turbine Q = P X 860 / (Enthalpy of inlet steam-Enthalpy of exhaust steam)

Q = 20 X 860 / (818-619)

Q2 = 86.43 MT

It is clear that, Turbine operating at pressure 65 kg/cm2 & temperature 490 deg C consumes more steam as compared to turbine operating at 87 kg/cm2 & temperature 515 deg C

3. Higher extraction/bleed steam flow

Steam turbines consume more steam to develop same power on higher steam extraction as compared to lower extraction.

Example: A condensing & extraction steam turbine having Inlet steam flow 105 TPH at pressure 65 kg/cm2 & 490 Deg C & Vacuum maintained in condenser is -0.9 kg/cm2.

Here we can cross check the power generation by steam turbine by increasing the extraction flow keeping inlet steam constant.

A-Extraction pressure = 2 Kg/cm2 & Temperature = 150 Deg C, flow = 75 TPH, Exhaust steam to condenser = 30 TPH

Enthalpy of inlet steam, H1 = 810 kcal/kg

Main steam flow Q1 = 105 TPH

Enthalpy of extraction steam = H2 =660 kcal/kg

Extraction steam flow Q2 = 75 TPH

Enthalpy of exhaust team = 620 kcal/kg

Exhaust steam flow Q3 = 30 TPH

Power developed by steam Turbine P = (Q2 X (H1-H2) / 860) + (Q3 X (H1-H3) / 860 )

P = (75 X (810-660) / 860) + (30 X (810-620) / 860) = 19.7 MW

B- Extraction pressure = 2 Kg/cm2 & Temperature = 150 Deg C, flow = 65 TPH, Exhaust steam to condenser = 40 TPH

Enthalpy of inlet steam, H1 = 810 kcal/kg

Main steam flow Q1 = 105 TPH

Enthalpy of extraction steam = H2 =660 kcal/kg

Extraction steam flow Q2 = 65 TPH

Enthalpy of exhaust team = 620 kcal/kg

Exhaust steam flow Q3 = 40 TPH

Power developed by steam Turbine P = (Q2 X (H1-H2) / 860) + (Q3 X (H1-H3) / 860 )

P = (65 X (810-660) / 860) + (40 X (810-620) / 860) = 20.16 MW

It is clear that, Turbine power generation at same inlet main steam flow will increase as extraction flow gets decrease & vice versa

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4. Higher pressure/temperature of extraction & bleed steam

Higher pressure/temperature of extraction & bleed steam leads to increased steam consumption to generate same power or power consumption reduces at same inlet flow.

Example: A condensing , extraction & bleed steam turbine having Inlet steam flow 105 TPH at pressure 65 kg/cm2 & 490 Deg C & Vacuum maintained in condenser is -0.9 kg/cm2

 A-Bleed steam 10 kg/cm2 & Temperature 200 Deg C, flow =25 TPH, Extraction pressure = 2 Kg/cm2 & Temperature = 150 Deg C, flow = 60 TPH, Exhaust steam to condenser = 25 TPH

Enthalpy of inlet steam, H1 = 810 kcal/kg

Main steam flow Q1 = 105 TPH

Enthalpy of bleed steam = H2 =674 kcal/kg

Bleed steam flow Q2 = 25 TPH

Enthalpy of extraction steam = H3 =660 kcal/kg

Extraction steam flow Q3 = 60 TPH

Enthalpy of exhaust team H4= 620 kcal/kg

Exhaust steam flow Q4 = 20 TPH

Power developed by steam Turbine P = (Q2 X (H1-H2) / 860) + (Q3 X (H1-H3) / 860 ) +(Q4 X (H1-H4)/860)

P = (25 X (810-674) / 860) + (60 X (810-660)/860) + (20 X (810-620)/860)

P = 18.82 MW

B-Bleed steam 14 kg/cm2 & Temperature 260 Deg C, flow =25 TPH, Extraction pressure = 2.5 Kg/cm2 & Temperature = 170 Deg C, flow = 60 TPH, Exhaust steam to condenser = 25 TPH

Enthalpy of inlet steam, H1 = 810 kcal/kg

Main steam flow Q1 = 105 TPH

Enthalpy of bleed steam = H2 =704 kcal/kg

Bleed steam flow Q2 = 25 TPH

Enthalpy of extraction steam = H3 =669 kcal/kg

Extraction steam flow Q3 = 60 TPH

Enthalpy of exhaust team H4= 620 kcal/kg

Exhaust steam flow Q4 = 20 TPH

Power developed by steam Turbine P = (Q2 X (H1-H2) / 860) + (Q3 X (H1-H3) / 860) + (Q4 X (H1-H4)/860)

P = (25 X (810-704) / 860) + (60 X (810-669)/860) + (25 X (810-620)/860)

P = 18.43 MW

It is clear that, Turbine power generation reduces at higher extraction or bleed steam pressure &temperature

Note: Steam consumption of turbine increases if,

1-Bleed steam & extraction steam pressure increases

2-Bleed steam & extraction steam temperature increases

3-Bleed steam flow & extraction steam flow increases

4. Increase of exhaust steam temperature due to more clearance in labyrinth seals

Turbine steam consumption increases if exhaust steam temperature to condenser increases.

Also read 16-Perfect reasons for increasing the fuel consumption of Boilers

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