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#BoilerManual #ProtectingPressureParts #Section10 #Page10

Questions for protecting pressure parts

1. What are the two ways you can minimize overheating, thermal stress, and corrosion in your boiler?

........ 1. __________________________________

........ 2. __________________________________

2. What are the temperature limitations when filling the boiler with water?

3. What should you do to decrease the chances of an explosion when following a burner trip?

4. How can you reduce the chances of an explosion when you have observed dark and smoking flames in the furnace?

5. What is the minimum amount of feedwater flow needed when firing the boiler?

6. What is the maximum rate of temperature change at the convection pass outlet?

7. Name two ways you can detect a tube failure by monitoring indicators in the control room.

........ 1. __________________________________

........ 2. __________________________________

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#BoilerManual #ProtectingPressureParts #Section10 #Page10

Questions for protecting pressure parts

1. What are the two ways you can minimize overheating, thermal stress, and corrosion in your boiler?

........ 1. __________________________________

........ 2. __________________________________

2. What are the temperature limitations when filling the boiler with water?

3. What should you do to decrease the chances of an explosion when following a burner trip?

4. How can you reduce the chances of an explosion when you have observed dark and smoking flames in the furnace?

5. What is the minimum amount of feedwater flow needed when firing the boiler?

6. What is the maximum rate of temperature change at the convection pass outlet?

7. Name two ways you can detect a tube failure by monitoring indicators in the control room.

........ 1. __________________________________

........ 2. __________________________________

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#BoilerManual #OptimizingCombustion #Section9 #Page10

2. In order to keep cyclone coal carryover to the furnace to a minimum, keep coal sizing continuously as fine as possible (95% through 1/4" mesh or finer). Also, keep quantities

of primary air to a minimum to keep fires in the cyclone for as long as possible. Operate with as high an air temperature to the cyclone as possible.

3. Keep cyclone firing balanced at all times. Check fuel and air flow calibration for each cyclone frequently to be sure these readings are correct.

4. Other than the above operating variables, additional maintenance should be performed in the cyclone and lower furnace to keep any iron sulfide formed away from the tube surfaces. For this reason it is necessary to protect these surfaces by maintaining stud length (at least 1/4" or longer) and applying a good refractory coating that will remain intact on the tub es for a long period of time.

Item number 4 will be a continuous maintenance item, requiring cleaning and inspecting during outages. The other items are ones which the operator has the capability of controlling. Exercising such control will insure efficient and prolonged operation.

The other important criterion for establishing the suitability f coal for firing in the cyclone is the viscosity of the slag formed from the ash. Since satisfactory combustion of coal depends on the formation of a liquid slag layer in the cyclone, and since ash is removed from the cyclone and primary furnace in fluid form, the viscosity of the slag must permit slag flow at the temperatures experienced within the cyclone and furnace.

Slag will just flow on a horizontal surface at a viscosity of 250 poises. The temperature at which this viscosity occurs (T250) {in the term T250 the number is written as a subscript} is used as the criterion to determine the suitability of a coal from this point of view. The

T250 is calculated from a chemical analysis of the coal ash, and a value of

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#BoilerManual #OptimizingCombustion #Section9 #Page10

2. In order to keep cyclone coal carryover to the furnace to a minimum, keep coal sizing continuously as fine as possible (95% through 1/4" mesh or finer). Also, keep quantities

of primary air to a minimum to keep fires in the cyclone for as long as possible. Operate with as high an air temperature to the cyclone as possible.

3. Keep cyclone firing balanced at all times. Check fuel and air flow calibration for each cyclone frequently to be sure these readings are correct.

4. Other than the above operating variables, additional maintenance should be performed in the cyclone and lower furnace to keep any iron sulfide formed away from the tube surfaces. For this reason it is necessary to protect these surfaces by maintaining stud length (at least 1/4" or longer) and applying a good refractory coating that will remain intact on the tub es for a long period of time.

Item number 4 will be a continuous maintenance item, requiring cleaning and inspecting during outages. The other items are ones which the operator has the capability of controlling. Exercising such control will insure efficient and prolonged operation.

The other important criterion for establishing the suitability f coal for firing in the cyclone is the viscosity of the slag formed from the ash. Since satisfactory combustion of coal depends on the formation of a liquid slag layer in the cyclone, and since ash is removed from the cyclone and primary furnace in fluid form, the viscosity of the slag must permit slag flow at the temperatures experienced within the cyclone and furnace.

Slag will just flow on a horizontal surface at a viscosity of 250 poises. The temperature at which this viscosity occurs (T250) {in the term T250 the number is written as a subscript} is used as the criterion to determine the suitability of a coal from this point of view. The

T250 is calculated from a chemical analysis of the coal ash, and a value of

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#BoilerManual #Ramping #Section8 #Page10

taken to automate the control system to the point where the 201 valves are opened.

RAMPING PROCEDURE

1. Align firing rate master to the measured variable and transfer to automatic.

2. With the steam temperature master aligned, transfer to automatic.

3. Align boiler master and transfer to automatic.

4. Have the high pressure superheater stop valves, 200, ready for operation with the breakers in.

5. Place the 201 pressure reducing valves in automatic.

6. Unit is now ready to ramp. Have a second polishing demineralizer ready for service.

7. Manually increase boiler load on the turbine slightly above 10% of full load flow. The boiler will follow the turbine and the 201 valves will open to their initial position.

Some transient conditions may develop with the initial opening of the 201 valves. These should be allowed to settle out. All burners which are required to complete the ramp should either be in service or ready for immediate firing. Gas temperature, PSH temperature, CP outlet temperature, and SSH outlet temperature should be stable.

It is extremely important that the 202 and 207 valve positions can be allowed to stabilize. When those conditions are met, the ramp can be initiated.

8. The turbine-generator control should be automated to the megawatt demand station.

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#BoilerManual #Ramping #Section8 #Page10

taken to automate the control system to the point where the 201 valves are opened.

RAMPING PROCEDURE

1. Align firing rate master to the measured variable and transfer to automatic.

2. With the steam temperature master aligned, transfer to automatic.

3. Align boiler master and transfer to automatic.

4. Have the high pressure superheater stop valves, 200, ready for operation with the breakers in.

5. Place the 201 pressure reducing valves in automatic.

6. Unit is now ready to ramp. Have a second polishing demineralizer ready for service.

7. Manually increase boiler load on the turbine slightly above 10% of full load flow. The boiler will follow the turbine and the 201 valves will open to their initial position.

Some transient conditions may develop with the initial opening of the 201 valves. These should be allowed to settle out. All burners which are required to complete the ramp should either be in service or ready for immediate firing. Gas temperature, PSH temperature, CP outlet temperature, and SSH outlet temperature should be stable.

It is extremely important that the 202 and 207 valve positions can be allowed to stabilize. When those conditions are met, the ramp can be initiated.

8. The turbine-generator control should be automated to the megawatt demand station.

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#BoilerManual #BypassSystem #Section7 #Page10

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Alt = Labeled Fig. 3 Hot cleanup. The image is sideways with the bottom along the right edge and the top along the left edge. The image is very similar to Fig. 2 but focus is on the connection between the Flashtank and the Deaerator via valves 231 and 242; details of operation are in the main text.

#BoilerManual #BypassSystem #Section7 #Page10

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Alt = Labeled Fig. 3 Hot cleanup. The image is sideways with the bottom along the right edge and the top along the left edge. The image is very similar to Fig. 2 but focus is on the connection between the Flashtank and the Deaerator via valves 231 and 242; details of operation are in the main text.

#BoilerManual #CycloneOperation #Section6 #Page10

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Alt = Labeled Fig. 4 Cyclone test panel. The image is sideways with the bottom along the right edge and the top along the left edge. This image is a drawn rendering of the front of a rack-mountable box with vertical handles, one on the right and one on the left.
At the top center of the box is marked TEST PANEL. In the middle is a large rotary switch pointer, halfway surrounded by small squares indicating 9 possible positions to the right of the switch. The top position is marked Idle Damper and the switch appears to be engaged with that position. To the left of the switch are 3 columns of toggle switches and round lights marked LIGHTER. The column to the right of the switch is labeled CYCLONE with 3 columns of toggle switches and round lights, but at the top of the column it has one less light than the left hand column.
Between the two columns, below the rotary switch, are three lamps marked Transformer, Lighter on and Cyclone on. Between the two columns, above the rotary switch, are one toggle switch marked Trip, and two lights each marked Open/close, and Trouble respectively.

The left column of lights and switches under the LIGHTER label are, in top down order:
leftmost column are lights marked Ready, Close, Close, then a toggle marked Ltr. press. > 150 psi, then a light marked Stop, then a toggle marked Oil valve.
Middle column has lights, one unmarked below the LIGHTER label, Pri. Damper, Sec. Damper, then a toggle marked Air flow > 30%, then a toggle marked Lighter, then a toggle marked Lighter flame.The rightmost column under LIGHTER is all lights, marked in top-down order: Pri. air cold, Open, Open, Sec. air L.O., Start, and Flame.

The right hand column of lights and switches under the CYCLONE label are, in top down order:
left column consists of 3 lights and two toggles, labeled from top down, Closed, Stop, Trouble acking {sic}, Feeder speed > 24%, Jacket flow;
middle column has one light under the CYCLONE label, then the remainder are toggle switches marked, top down: Feeder out valve, Feeder, Main flame, Air temp. > 300 F, and Feeder in valve;
rightmost column are the lights labeled Ready, Open, Start, Established, then two toggles labeled Feeder unload and Coal on belt.

#BoilerManual #CycloneOperation #Section6 #Page10

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Alt = Labeled Fig. 4 Cyclone test panel. The image is sideways with the bottom along the right edge and the top along the left edge. This image is a drawn rendering of the front of a rack-mountable box with vertical handles, one on the right and one on the left.
At the top center of the box is marked TEST PANEL. In the middle is a large rotary switch pointer, halfway surrounded by small squares indicating 9 possible positions to the right of the switch. The top position is marked Idle Damper and the switch appears to be engaged with that position. To the left of the switch are 3 columns of toggle switches and round lights marked LIGHTER. The column to the right of the switch is labeled CYCLONE with 3 columns of toggle switches and round lights, but at the top of the column it has one less light than the left hand column.
Between the two columns, below the rotary switch, are three lamps marked Transformer, Lighter on and Cyclone on. Between the two columns, above the rotary switch, are one toggle switch marked Trip, and two lights each marked Open/close, and Trouble respectively.

The left column of lights and switches under the LIGHTER label are, in top down order:
leftmost column are lights marked Ready, Close, Close, then a toggle marked Ltr. press. > 150 psi, then a light marked Stop, then a toggle marked Oil valve.
Middle column has lights, one unmarked below the LIGHTER label, Pri. Damper, Sec. Damper, then a toggle marked Air flow > 30%, then a toggle marked Lighter, then a toggle marked Lighter flame.The rightmost column under LIGHTER is all lights, marked in top-down order: Pri. air cold, Open, Open, Sec. air L.O., Start, and Flame.

The right hand column of lights and switches under the CYCLONE label are, in top down order:
left column consists of 3 lights and two toggles, labeled from top down, Closed, Stop, Trouble acking {sic}, Feeder speed > 24%, Jacket flow;
middle column has one light under the CYCLONE label, then the remainder are toggle switches marked, top down: Feeder out valve, Feeder, Main flame, Air temp. > 300 F, and Feeder in valve;
rightmost column are the lights labeled Ready, Open, Start, Established, then two toggles labeled Feeder unload and Coal on belt.

#BoilerManual #CycloneDescription #Section5 #Page10

when more heat is generated by the combustion process than is lost to the surroundings.

The ignition temperature of coal may be considered to be the ignition temperature of its fixed carbon content. The gaseous constituents of coal are usually distilled off, but not ignited, prior to reaching the ignition temperature. It is the process of distilling off the gaseous constituents in the fuel which delays combustion.

Delayed combustion can result in many adverse effects in cyclone performance and general unit operation. Many factors contribute to inefficient operation fo the unit, whether it be fuel quality of preparation, air quantity or temperature, or general boiler operation.

Normally, operation for extended periods of time at loads below one-half of normal cyclone rating can result in a frozen slag tap. During low load operation, it is generally advisable to operate fewer cyclones at a higher loading. If the load were to be distributed to all cyclones, the limited heat input would not be sufficient to insure adequate slag tapping in any of the cyclones.

Regardless of the number of cyclones in-service, equal fuel and air input to each cyclone is recommended to help maintain event heat distribution to the boiler. This will help maintain the correct fuel/air ratio and insure that individual cyclone loading is maintained within design limits.

In most cases, the cyclone can handle loads greater than its design rating. However, operating at higher than design loads is not recommended because of the high localized heat input to the cyclone and furnace wall tubes.

The maximum theoretical temperature which can be reached by the products of combustion is known as the adiabatic flame temperature.

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#BoilerManual #CycloneDescription #Section5 #Page10

when more heat is generated by the combustion process than is lost to the surroundings.

The ignition temperature of coal may be considered to be the ignition temperature of its fixed carbon content. The gaseous constituents of coal are usually distilled off, but not ignited, prior to reaching the ignition temperature. It is the process of distilling off the gaseous constituents in the fuel which delays combustion.

Delayed combustion can result in many adverse effects in cyclone performance and general unit operation. Many factors contribute to inefficient operation fo the unit, whether it be fuel quality of preparation, air quantity or temperature, or general boiler operation.

Normally, operation for extended periods of time at loads below one-half of normal cyclone rating can result in a frozen slag tap. During low load operation, it is generally advisable to operate fewer cyclones at a higher loading. If the load were to be distributed to all cyclones, the limited heat input would not be sufficient to insure adequate slag tapping in any of the cyclones.

Regardless of the number of cyclones in-service, equal fuel and air input to each cyclone is recommended to help maintain event heat distribution to the boiler. This will help maintain the correct fuel/air ratio and insure that individual cyclone loading is maintained within design limits.

In most cases, the cyclone can handle loads greater than its design rating. However, operating at higher than design loads is not recommended because of the high localized heat input to the cyclone and furnace wall tubes.

The maximum theoretical temperature which can be reached by the products of combustion is known as the adiabatic flame temperature.

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#BoilerManual #Lighters #Section4 #Page10

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Alt = Labeled Fig. 6 Oil fill. The image is on its side such that the bottom is along the right edge of the page and the top is along its left, and it utilizes the mechanical symbols identified in the printed key on page 7. This image is identical to Fig. 5 except the solenoid conditions show what has occurred for the Oil Fill condition.

#BoilerManual #Lighters #Section4 #Page10

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Alt = Labeled Fig. 6 Oil fill. The image is on its side such that the bottom is along the right edge of the page and the top is along its left, and it utilizes the mechanical symbols identified in the printed key on page 7. This image is identical to Fig. 5 except the solenoid conditions show what has occurred for the Oil Fill condition.

#BoilerManual #AirAndGasFlow #Section3 #Page10

according to pressure drop curves. The specifics for air flow control will be covered in the Cyclone Description and Operation section.

Coal burns more rapidly and more completely when combustion air is heated. The tubular air heater, Figure 1, located in the secondary air path between the FD fans and the windbox, heats the combustion air to approximately 600 F.

The tubular air heater absorbs waste heat from the boiler flue gas and transfers this heat to incoming air. The air heater is essentially a nest of tubes expanded into tube sheets and enclosed in a suitable reinforced steel casing. Hot flue gases pass through the tubes and heat the tube metal. As cooler air (supplied by the FD fans) is passed over the hot tubes, it becomes heated.

FLUE GAS FLOW

The flue gas resulting from the combustion process travels up through the furnace to the convection pass (pendant and horizontal), Figure 7. As the flow reaches the furnace arch, it is deflected and caused to enter the superheaters more evenly. The gas then flows across the secondary superheater (SSH) and reheat superheater (RSH) surfaces in the pendant convection pass and down through the primary superheater (PSH), reheat superheater (RSH) and economizer in the horizontal convection pass, Figure 8. From the point of combustion until the flue gas leaves the unit, heat is continuously given up to the fluid passing through the unit's tubes to produce steam. The gas temperature starts at approximately 3000 F in the furnace and drops to approximately 690 F as it leaves the economizer at full load. From the economizer the flue gas flow takes sharp change in direction. It is here that the larger ash particles fall out of the gas stream. These particles are collected in ash hoppers located below the economizer. From the economizer, the gas flow is split. One

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#BoilerManual #AirAndGasFlow #Section3 #Page10

according to pressure drop curves. The specifics for air flow control will be covered in the Cyclone Description and Operation section.

Coal burns more rapidly and more completely when combustion air is heated. The tubular air heater, Figure 1, located in the secondary air path between the FD fans and the windbox, heats the combustion air to approximately 600 F.

The tubular air heater absorbs waste heat from the boiler flue gas and transfers this heat to incoming air. The air heater is essentially a nest of tubes expanded into tube sheets and enclosed in a suitable reinforced steel casing. Hot flue gases pass through the tubes and heat the tube metal. As cooler air (supplied by the FD fans) is passed over the hot tubes, it becomes heated.

FLUE GAS FLOW

The flue gas resulting from the combustion process travels up through the furnace to the convection pass (pendant and horizontal), Figure 7. As the flow reaches the furnace arch, it is deflected and caused to enter the superheaters more evenly. The gas then flows across the secondary superheater (SSH) and reheat superheater (RSH) surfaces in the pendant convection pass and down through the primary superheater (PSH), reheat superheater (RSH) and economizer in the horizontal convection pass, Figure 8. From the point of combustion until the flue gas leaves the unit, heat is continuously given up to the fluid passing through the unit's tubes to produce steam. The gas temperature starts at approximately 3000 F in the furnace and drops to approximately 690 F as it leaves the economizer at full load. From the economizer the flue gas flow takes sharp change in direction. It is here that the larger ash particles fall out of the gas stream. These particles are collected in ash hoppers located below the economizer. From the economizer, the gas flow is split. One

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#BoilerManual #FluidCirculation #Section2 #Page10

In the UP boiler, flow is maintained by the feed pumps. To insure that there is sufficient flow through each of the furnace tubes to prevent overheating, a minimum flow equal to 33% of full load flow must be maintained in the furnace circuits anytime the boiler is fired. In addition to this safety precaution, the firing rate must be properly matched to steam flow at all loads. This is to insure that there is enough flow to carry away all of the heat being transferred to the tube, or overheat failures could result. {This is a reason why a small heating boiler is used to bring this big boiler up to proper minimum flows when starting up from cold condition.}

The heat input to the boiler from combustion must also be evenly balanced across the furnace. Since each tube receives the same steam flow as other tubes in its circuit, they must all receive approximately the same amount of heat. Firing must be evenly balanced between all cyclones to equalize the heat input as much as possible.

At steady state conditions the feedwater flow-in equals the steam flow-out. The pressure level will be influenced not only by the valve restriction at the outlet, but also by the density of the fluid through the system. Therefore, it is important to note that a change in heat input will influence both pressure and temperature. It is possible to vary the flow and pressure at the outlet by changing the amount of valve restriction or at the inlet by changing both the feedwater flow and the heat input. It is important to note that a change in feedwater flow without a corresponding change in heat input will result in a change in the outlet steam temperature. During transient conditions, other factors such as the fluid and energy storage requirements which change with load, must be considered since they influence the feedwater flow and heat inputs.

CIRCULATION THROUGH THE UNIVERSAL PRESSURE BOILER

Economizer

Water is supplied through the feedwater control valve to the economizer inlet header, Figure 11, and flows upward through two banks. From the

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#BoilerManual #FluidCirculation #Section2 #Page10

In the UP boiler, flow is maintained by the feed pumps. To insure that there is sufficient flow through each of the furnace tubes to prevent overheating, a minimum flow equal to 33% of full load flow must be maintained in the furnace circuits anytime the boiler is fired. In addition to this safety precaution, the firing rate must be properly matched to steam flow at all loads. This is to insure that there is enough flow to carry away all of the heat being transferred to the tube, or overheat failures could result. {This is a reason why a small heating boiler is used to bring this big boiler up to proper minimum flows when starting up from cold condition.}

The heat input to the boiler from combustion must also be evenly balanced across the furnace. Since each tube receives the same steam flow as other tubes in its circuit, they must all receive approximately the same amount of heat. Firing must be evenly balanced between all cyclones to equalize the heat input as much as possible.

At steady state conditions the feedwater flow-in equals the steam flow-out. The pressure level will be influenced not only by the valve restriction at the outlet, but also by the density of the fluid through the system. Therefore, it is important to note that a change in heat input will influence both pressure and temperature. It is possible to vary the flow and pressure at the outlet by changing the amount of valve restriction or at the inlet by changing both the feedwater flow and the heat input. It is important to note that a change in feedwater flow without a corresponding change in heat input will result in a change in the outlet steam temperature. During transient conditions, other factors such as the fluid and energy storage requirements which change with load, must be considered since they influence the feedwater flow and heat inputs.

CIRCULATION THROUGH THE UNIVERSAL PRESSURE BOILER

Economizer

Water is supplied through the feedwater control valve to the economizer inlet header, Figure 11, and flows upward through two banks. From the

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@Su_G #BoilerManual #UnitDescription #Section1 #Page10

These material streams are all essential to the operation of the unit. They will be discussed in greater detail in

a later section of this manual.

COMPONENTS
LOCATION, DESCRIPTION & FUNCTION

See Figure 4 for the location of the following boiler components:

1 - Forced Draft Fan (FD)

2 - Feeders

3 - Cyclones

4 - Induced Draft Fan (ID)

5 - Air Heater

6 - Gas Recirculation Fans (GR)

7 - Furnace

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@Su_G #BoilerManual #UnitDescription #Section1 #Page10

These material streams are all essential to the operation of the unit. They will be discussed in greater detail in

a later section of this manual.

COMPONENTS
LOCATION, DESCRIPTION & FUNCTION

See Figure 4 for the location of the following boiler components:

1 - Forced Draft Fan (FD)

2 - Feeders

3 - Cyclones

4 - Induced Draft Fan (ID)

5 - Air Heater

6 - Gas Recirculation Fans (GR)

7 - Furnace

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