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#BoilerManual #OptimizingCombustion #Section9 #Page19

7. What three materials in coal are important to its suitability as fuel?

........ 1. __________________________________

........ 2. __________________________________

........ 3. __________________________________

8. What are the four steps that can help prevent iron sulfide formation?

........ 1. __________________________________

........ 2. __________________________________

........ 3. __________________________________

........ 4. __________________________________

9. What is slag viscosity and why is it critical to the cyclone furnace?

10. Name five conditions which affect coal-ash deposits in your furnace.

........ 1. __________________________________

........ 2. __________________________________

........ 3. __________________________________

........ 4. __________________________________

........ 5. __________________________________

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#BoilerManual #OptimizingCombustion #Section9 #Page19

7. What three materials in coal are important to its suitability as fuel?

........ 1. __________________________________

........ 2. __________________________________

........ 3. __________________________________

8. What are the four steps that can help prevent iron sulfide formation?

........ 1. __________________________________

........ 2. __________________________________

........ 3. __________________________________

........ 4. __________________________________

9. What is slag viscosity and why is it critical to the cyclone furnace?

10. Name five conditions which affect coal-ash deposits in your furnace.

........ 1. __________________________________

........ 2. __________________________________

........ 3. __________________________________

........ 4. __________________________________

........ 5. __________________________________

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#BoilerManual #Ramping #Section8 #Page19

data shown in Figure 9. There was no stabilization period, which in this case was badly needed.

Convection pass outlet and PSH outlet temperatures were too low to begin the ramp. Since both temperatures were low, the 207 valve was further closed than it normally would be had proper pre-ramp conditions been established.

The initial opening of the 201 valves drove the 207 valve completely closed. The 207 valve could not compensate for the increased flow through the 201 due to the low initial temperatures. This resulted in a flow increase when there should have been merely and exchange. Due to the increased flow, PSH temperature dropped sharply approximately 15 minutes into the ramp. This was aggravated by the fact that the increased flow was from low temperature convection pass steam. Firing rate was increased drastically to offset the low PSH temperature. Convection pass temperature rose sharply 20-25 minutes into the ramp. Furnace circuit temperatures were not taken, but it is possible they were in alarm at this point.

Firing rate was lowered to near normal at 25 minutes and the system began to stabilize. From about 30 minutes on, the pressure ramp was fairly smooth, as convection pass temperature was sufficiently high. 202 and 201 valve actions stabilized, while MW and throttle pressure increased smoothly.

Temperature control was still not good, however. Firing rate was erroneously increased from 50 to 70 minutes at a time when it should have been leveled off as shown by the dotted line. The rising CP outlet and PSH temperatures should have indicated that firing needed to be held steady rather than increased. Main steam, PSH and CP outlet temperatures all went dangerously high, and in all probability, so did furnace circuit temperatures.

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#BoilerManual #Ramping #Section8 #Page19

data shown in Figure 9. There was no stabilization period, which in this case was badly needed.

Convection pass outlet and PSH outlet temperatures were too low to begin the ramp. Since both temperatures were low, the 207 valve was further closed than it normally would be had proper pre-ramp conditions been established.

The initial opening of the 201 valves drove the 207 valve completely closed. The 207 valve could not compensate for the increased flow through the 201 due to the low initial temperatures. This resulted in a flow increase when there should have been merely and exchange. Due to the increased flow, PSH temperature dropped sharply approximately 15 minutes into the ramp. This was aggravated by the fact that the increased flow was from low temperature convection pass steam. Firing rate was increased drastically to offset the low PSH temperature. Convection pass temperature rose sharply 20-25 minutes into the ramp. Furnace circuit temperatures were not taken, but it is possible they were in alarm at this point.

Firing rate was lowered to near normal at 25 minutes and the system began to stabilize. From about 30 minutes on, the pressure ramp was fairly smooth, as convection pass temperature was sufficiently high. 202 and 201 valve actions stabilized, while MW and throttle pressure increased smoothly.

Temperature control was still not good, however. Firing rate was erroneously increased from 50 to 70 minutes at a time when it should have been leveled off as shown by the dotted line. The rising CP outlet and PSH temperatures should have indicated that firing needed to be held steady rather than increased. Main steam, PSH and CP outlet temperatures all went dangerously high, and in all probability, so did furnace circuit temperatures.

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#BoilerManual #BypassSystem #Section7 #Page19

recovery. When the capacity of the 220 valve has been exhausted, valve 240 will open and pass steam to the condenser as required to maintain flashtank pressure.

Flashtank pressure reaches its setpoint of 500 psi. Steam flow through the SSH increases to approximately 4% of full load flow and is admitted to the turbine for rolling to synchronous speed.

As increased flashtank steam becomes available, the high pressure heater steam control valve, 220, will open. The high pressure heater will reach an operating pressure of 450 psi. Heater drains return flow to the condenser. At this point, the main steam line drain valve, MS-2, can be closed.

Throughout the warmup period, it is very important to monitor the water quality. If the proper water quality is not obtained, ti will be necessary to initiate a hold in the startup.

We have discussed the various stages of t he startup Bypass System from initial circulation to rolling of the turbine. The remaining portion of startup ramping will be discussed in a following section.

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#BoilerManual #BypassSystem #Section7 #Page19

recovery. When the capacity of the 220 valve has been exhausted, valve 240 will open and pass steam to the condenser as required to maintain flashtank pressure.

Flashtank pressure reaches its setpoint of 500 psi. Steam flow through the SSH increases to approximately 4% of full load flow and is admitted to the turbine for rolling to synchronous speed.

As increased flashtank steam becomes available, the high pressure heater steam control valve, 220, will open. The high pressure heater will reach an operating pressure of 450 psi. Heater drains return flow to the condenser. At this point, the main steam line drain valve, MS-2, can be closed.

Throughout the warmup period, it is very important to monitor the water quality. If the proper water quality is not obtained, ti will be necessary to initiate a hold in the startup.

We have discussed the various stages of t he startup Bypass System from initial circulation to rolling of the turbine. The remaining portion of startup ramping will be discussed in a following section.

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#BoilerManual #CycloneOperation #Section6 #Page19

* Feeder temperature normal.
* Cyclone jacket cooling water on.
* Coal detected at feeder inlet
* Coal detected on feeder belt (5 second delay).

The main flame monitor delay (20 seconds) begins to time when the feeder is started. During this 20 seconds, if the lighter is not successfully lit, the cyclone will trip. At the end of the time delay, if a main flame is not detected the cyclone will trip. Also, at the end of the 20 second time delay, the primary/tertiary air and secondary air shutoff dampers and feeder outlet valve are checked for proper position. If an of these devices are not at the proper position for longer than 10 seconds, the cyclone will trip.

The lighter will remain in service at least five minutes after the cyclone is successfully lit. The Main Flame light will light white when a main flame is being detected.

The Cyclone Trouble light will flash amber when a cyclone trouble alarm is present. The pushbutton, when depressed, acknowledges the alarm and changes the flashing alarm to a steady indication.

When the cyclone is not successfully lit, the analog control for thte feeder and the secondary air velocity damper are commanded to light off. Once the cyclone becomes successfully lit, the analog controls are released to set the firing rate of the cyclone.

When the cyclone is stopped or tripped, it will go into the following shutdown sequence:

1. Feeder stops.
2. Feeder outlet valve closes.
3. Lighter shutdown.

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#BoilerManual #CycloneOperation #Section6 #Page19

* Feeder temperature normal.
* Cyclone jacket cooling water on.
* Coal detected at feeder inlet
* Coal detected on feeder belt (5 second delay).

The main flame monitor delay (20 seconds) begins to time when the feeder is started. During this 20 seconds, if the lighter is not successfully lit, the cyclone will trip. At the end of the time delay, if a main flame is not detected the cyclone will trip. Also, at the end of the 20 second time delay, the primary/tertiary air and secondary air shutoff dampers and feeder outlet valve are checked for proper position. If an of these devices are not at the proper position for longer than 10 seconds, the cyclone will trip.

The lighter will remain in service at least five minutes after the cyclone is successfully lit. The Main Flame light will light white when a main flame is being detected.

The Cyclone Trouble light will flash amber when a cyclone trouble alarm is present. The pushbutton, when depressed, acknowledges the alarm and changes the flashing alarm to a steady indication.

When the cyclone is not successfully lit, the analog control for thte feeder and the secondary air velocity damper are commanded to light off. Once the cyclone becomes successfully lit, the analog controls are released to set the firing rate of the cyclone.

When the cyclone is stopped or tripped, it will go into the following shutdown sequence:

1. Feeder stops.
2. Feeder outlet valve closes.
3. Lighter shutdown.

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#BoilerManual #CycloneDescription #Section5 #Page19

7. To achieve the highest flame temperature, is a large or small amount of excess air desirable?

8. Coal is burned almost instantly in the cyclone. How is this operating characteristic used to control boiler output?

9. Which type of rated coal is best suited for low load operating conditions? High viscosity coal or low viscosity coal?

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#BoilerManual #CycloneDescription #Section5 #Page19

7. To achieve the highest flame temperature, is a large or small amount of excess air desirable?

8. Coal is burned almost instantly in the cyclone. How is this operating characteristic used to control boiler output?

9. Which type of rated coal is best suited for low load operating conditions? High viscosity coal or low viscosity coal?

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#BoilerManual #Lighters #Section4 #Page19

Questions for Mark IV oil lighters

1. What is the main purpose of the lighter?

2. What are the three secondary purposes of the lighter?
..........1. ____________________________________
..........2. ____________________________________
..........3. ____________________________________

3. True or False.
Under certain circumstances, the oil lighter can be used to carry load.

4. At what distance should the igniter spark gap be set?

5. True or False.
The lighter always travels into and away from the lightoff position at the same speed.

6. Name the three operating conditions of the lighter.
..........1. ____________________________________
..........2. ____________________________________
..........3. ____________________________________

7. What is the sequence of events for normal lighter shutdown?

........................................................................................................... (Continued)

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#BoilerManual #Lighters #Section4 #Page19

Questions for Mark IV oil lighters

1. What is the main purpose of the lighter?

2. What are the three secondary purposes of the lighter?
..........1. ____________________________________
..........2. ____________________________________
..........3. ____________________________________

3. True or False.
Under certain circumstances, the oil lighter can be used to carry load.

4. At what distance should the igniter spark gap be set?

5. True or False.
The lighter always travels into and away from the lightoff position at the same speed.

6. Name the three operating conditions of the lighter.
..........1. ____________________________________
..........2. ____________________________________
..........3. ____________________________________

7. What is the sequence of events for normal lighter shutdown?

........................................................................................................... (Continued)

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#BoilerManual #AirAndGasFlow #Section3 #Page19

This bellmouth differential is effected by the secondary air control damper and the FD fans and will be discussed in greater detail in the Cyclone Description and Operation section.

TOTAL OR EXCESS AIR

The continuous measurement of combustion air is necessary to optimize efficiency of operation and to assure effective control of available heat losses. The amount of total air that should be used can be determined by continuously monitoring the constituents of the flue gas (CO2, O2, and unburned gases). However, unburned gases, primarily carbon monoxide (CO) should never be present with proper combustion.

Ideally, a given amount of air is required to completely burn a given amount of fuel. The exact amount of air can be calculated from an analysis of the specific fuel, and is called theoretical air. 100% total air means 100%of the air theoretically required for complete combustion of the fuel without excess. Higher percentages indicate theoretical air plus excess air. For instance, 125% total air means 100% theoretical air plus 25% excess air. Some excess air is always required to account for minor imperfections throughout the system. The cyclone is not 100% efficient, coal flows are not perfectly balanced, air flow is not distributed perfectly, etc.

The cyclone is designed to operate most efficiently at full load. At lower loads, excess air must be increased. When cyclones are removed from service, some air passes through the idle dampers. This leakage does notcontribute to combustion, but does show up as excess air to the O2 monitoring equipment. Consequently, to maintain good combustion over the entire load range, excess air requirements are higher as cyclones are removed from service (Figure 14).

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#BoilerManual #AirAndGasFlow #Section3 #Page19

This bellmouth differential is effected by the secondary air control damper and the FD fans and will be discussed in greater detail in the Cyclone Description and Operation section.

TOTAL OR EXCESS AIR

The continuous measurement of combustion air is necessary to optimize efficiency of operation and to assure effective control of available heat losses. The amount of total air that should be used can be determined by continuously monitoring the constituents of the flue gas (CO2, O2, and unburned gases). However, unburned gases, primarily carbon monoxide (CO) should never be present with proper combustion.

Ideally, a given amount of air is required to completely burn a given amount of fuel. The exact amount of air can be calculated from an analysis of the specific fuel, and is called theoretical air. 100% total air means 100%of the air theoretically required for complete combustion of the fuel without excess. Higher percentages indicate theoretical air plus excess air. For instance, 125% total air means 100% theoretical air plus 25% excess air. Some excess air is always required to account for minor imperfections throughout the system. The cyclone is not 100% efficient, coal flows are not perfectly balanced, air flow is not distributed perfectly, etc.

The cyclone is designed to operate most efficiently at full load. At lower loads, excess air must be increased. When cyclones are removed from service, some air passes through the idle dampers. This leakage does notcontribute to combustion, but does show up as excess air to the O2 monitoring equipment. Consequently, to maintain good combustion over the entire load range, excess air requirements are higher as cyclones are removed from service (Figure 14).

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#BoilerManual #FluidCirculation #Section2 #Page19

Note that the flow does not follow the ordered number of cyclones. However, there is a very important pattern which should be kept in mind not only for operational purpose, but also for functional reasons.There are 14 separate flow paths, one beginning with each cyclone. Flow is arranged such that feedwater entering the first circuit of one cyclone discharges after the seventh circuit of the seventh cyclone through which it flowed.

A further distinction is made by the fact that the fourteen cyclones are grouped into two separate flow paths (A&B). Path A cyclones include the four lower cyclones of the furnace front wall together with the three upper cyclones of the furnace rear wall. Path B is just the opposite, as illustrated in figure 17.

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Alt = Figure 17 labeled "Cyclone flow paths (A & B)" depicts a row of cyclones along the upper edge labeled REAR WALL, with an arrow in the upper left pointing rightward labeled FLOW B with each cyclone along that edge labeled in descending order B7 thru B1. Opposite the row of B cyclones closer to the bottom is a corresponding row of cyclones labeled, in descending order, A7 thru A1, and labeled FRONT WALL. An arrow at the lower left pointing rightward is labeled PATH A. Lines are drawn in complicated manner to illustrate how the flow relates to each cyclone and each cyclone to each other.

#BoilerManual #FluidCirculation #Section2 #Page19

Note that the flow does not follow the ordered number of cyclones. However, there is a very important pattern which should be kept in mind not only for operational purpose, but also for functional reasons.There are 14 separate flow paths, one beginning with each cyclone. Flow is arranged such that feedwater entering the first circuit of one cyclone discharges after the seventh circuit of the seventh cyclone through which it flowed.

A further distinction is made by the fact that the fourteen cyclones are grouped into two separate flow paths (A&B). Path A cyclones include the four lower cyclones of the furnace front wall together with the three upper cyclones of the furnace rear wall. Path B is just the opposite, as illustrated in figure 17.

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Alt = Figure 17 labeled "Cyclone flow paths (A & B)" depicts a row of cyclones along the upper edge labeled REAR WALL, with an arrow in the upper left pointing rightward labeled FLOW B with each cyclone along that edge labeled in descending order B7 thru B1. Opposite the row of B cyclones closer to the bottom is a corresponding row of cyclones labeled, in descending order, A7 thru A1, and labeled FRONT WALL. An arrow at the lower left pointing rightward is labeled PATH A. Lines are drawn in complicated manner to illustrate how the flow relates to each cyclone and each cyclone to each other.

@Su_G #BoilerManual #UnitDescription #Section1 #Page19

The combustion of the combustible elements and compounds of the fuel with all the oxygen requires a temperature high enough to ignite the constituents, mixing or turbulence, and sufficient time for complete conbustion. These factors are referred to as the three T's of combustion.

The heat released as a result of combustion is then transferred to the heat absorbing surfaces of the boiler. In boiler practice, the heat of combustion of a fuel is the amount of heat expressed in Btu, generated by the complete combustion, or oxydation, of a unit weight of fuel (1 lb.).

There are three modes of heat transfer; radiation, convectin and conduction. All the varied phases of heat transfer involve one or more of these modes coupled with a temperature difference between a heat source and heat receiver.

Radiation is the transfer of heat energy between bodies without dependence on the presence of water in the intervening space. All matter radiates, and the transfer of heat (thermal radiation) is one important manifestation of this phenomenon. Radiation occurs when a hot object gives off heat in a straight line away from itself. Radiation is considered the primary mechanism of heat transfer in a furnace, with heat radiating from the hot fire to the cooler furnace walls.

Convection is the transfer of heat from one point to another within a fluid (gas or liquid) by the mixing of one part with another. Heat is transferred by convection when boiler flue gases pass over the tube surface and also when the steam or water pass over the internal surfaces of the tube. Convection is the primary mechanism of heat transfer which occurs in the convection pass of the boiler.

Conduction is the transfer of heat from one part of a body to another part of the same body, or from one body to another when they are in physical contact.

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@Su_G #BoilerManual #UnitDescription #Section1 #Page19

The combustion of the combustible elements and compounds of the fuel with all the oxygen requires a temperature high enough to ignite the constituents, mixing or turbulence, and sufficient time for complete conbustion. These factors are referred to as the three T's of combustion.

The heat released as a result of combustion is then transferred to the heat absorbing surfaces of the boiler. In boiler practice, the heat of combustion of a fuel is the amount of heat expressed in Btu, generated by the complete combustion, or oxydation, of a unit weight of fuel (1 lb.).

There are three modes of heat transfer; radiation, convectin and conduction. All the varied phases of heat transfer involve one or more of these modes coupled with a temperature difference between a heat source and heat receiver.

Radiation is the transfer of heat energy between bodies without dependence on the presence of water in the intervening space. All matter radiates, and the transfer of heat (thermal radiation) is one important manifestation of this phenomenon. Radiation occurs when a hot object gives off heat in a straight line away from itself. Radiation is considered the primary mechanism of heat transfer in a furnace, with heat radiating from the hot fire to the cooler furnace walls.

Convection is the transfer of heat from one point to another within a fluid (gas or liquid) by the mixing of one part with another. Heat is transferred by convection when boiler flue gases pass over the tube surface and also when the steam or water pass over the internal surfaces of the tube. Convection is the primary mechanism of heat transfer which occurs in the convection pass of the boiler.

Conduction is the transfer of heat from one part of a body to another part of the same body, or from one body to another when they are in physical contact.

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