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#BoilerManual #ProtectingPressureParts #Section10 #Page3

SUPERHEATER PROTECTION

Special attention must be given to protecting the superheating surfaces, particularly during startup as they are located in the hottest areas of the convection pass. During operation of the bypass system, fluid flow through the SH's is less than flow through the furnace circuits. The reheater is in effect an additional superheater inserted ahead of the intermediate pressure turbine and is placed in service in tandem with the SH, so it requires the same protection.

The two primary methods of protecting the SH's are to match fluid flow to firing rate during ramping and normal operation, and to limit gas temperature entering the SSH during startup until steam flow through each tube is sufficient for protection.

Gas temperature is limited to 1000 F entering the SSH until all water is removed from each tube and total steam flow is greater than 10% of rated flow. Ten percent flow is required to insure an even distribution of flow to each tube. The 1000 F limit is measured by the thermoprobes.

As previously stated, the superheater loops must be cleared of all condensate. The reason for the water removal requirements is that there can be no steam flow through a partially filled tube. Those portions of the tube not in contact with the water leg will be subject to high temperature and can overheat and fail. Water is removed from drainable SH's and RH's simply by opening all drains and vents. Removal is not as simple with the non-drainable pendant SH's and RH's since the water must be boiled away.

Thermocouples attached to the outlet legs of the SSH tubes will indicate when they have boiled out. The thermocouples will read saturation temperature while water remains in the tube. The reading will rise sharply as the tube is boiled clear and flow is established. SH tubes adjacent to the sidewalls are normally the last to boil out.

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#BoilerManual #OptimizingCombustion #Section9 #Page3

COMBUSTION LOSSES

It may be well to distinguish here between perfect and complete combustion. Perfect combustion is the result of supplying the exact amount of oxygen for burning all of the combustible elements of the fuel and utilizing in combustion all of the oxygen supplied. Complete combustion, on the other hand, results in the combustion of all the combustible elements of the fuel but does not utilize all of the oxygen supplied. If perfect combustion could be accomplished in the boiler furnace, there would be no unavoidable combustion losses. When combustion is complete, but not perfect, there are losses due to the supplying of too great an amount of oxygen, and hence air (4.32 lbs. of air yields 1 lb. of oxygen). The more nearly complete combustion can be made to approach perfect combustion, the less the loss that will occur in burning the fuel.

The real measure of the efficiency of combustion is found in the relationship existing between the amount of air theoretically required for the burning of the fuel and the amount of air actually supplied. In other words, the individual cyclone fuel/air ratios dictate the efficiency of combustion taking place inside that cyclone.

Not all of the Btu's available in the fuel are converted to heat and absorbed by the steam generation equipment. Some of the fuel may be unburned, leaving carbon in the ash, or carbon may be burned incompletely to form some CO instead of CO2. Usually all of the H2 in the fuel is burned. By far the greatest heat loss is that lost up the stack. Since the heat in the fuel is determined from a base of ambient temperature, all the products of combustion must be cooled to the same ambient temperature if all the heat is to be utilized. Higher temperature than ambient exiting the stack then represents a loss.

From a practical point of view, it is necessary to use more than the theoretical air requirements to assure sufficient oxygen for complete

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#BoilerManual #Ramping #Section8 #Page3

At this point the most critical step in the startup of a UP boiler begins (Figure 2). When the above conditions are reached the 201 valves are opened slightly. The 207 valve closes a proportional amount in order to maintain a constant temperature through the PSH and some flow is passed directly from the PSH to the SSH for the first time. Total steam flow to the turbine is unchanged. Flow is now divided between the 201 valves and the 205 valve via the flashtank, as opposed to all flow through the 205 valve before the 201's were opened. The bypass system continues to distribute the remaining flow to the feedwater heaters, deaerator and condenser.

The 201 valves are opened based on load demand and will increase pressure in the SSH and flow to the turbine. As flow to the turbine is increased, flow to the flashtank is reduced. When the SSH pressure exceeds the flashtank pressure the 205 non-return valve will close (Figure 3). All flow to the turbine is directly through the 201's . As the 201 valves open, the 207 valve is driven closed and the 202 begins closing to maintain boiler pressure. When superheater pressure reaches approximately 2000 psig, the 201 valve is wide open. To complete the pressurization of the superheater the 200 valves are pulsed open to pass full minimum flow through the SSH to the turbine (Figures 4 and 5). The 202 valves will then close completely, taking the system off the bypass.

This gradual pressurization of the SSH from 500 psi to normal operating pressure and increase of generator output from 6.5 to 33% load is referred to as the SSH pressure ramp. The system is designed to provide a fully automatic ramp. The system is designed to provide a fully automatic ramp. The opening of the 201 and 200 valves are preprogrammed based entirely on the megawatt (MW) load demand. Final load and the rate of load change are set by the operator at the MW demand station. Firing is automatically increased to maintain steam temperature as the flow is increased through the superheaters. During the ramp, control of the firing rate is based on gas temperature as measured by the thermoprobes. When minimum load is reached, firing rate control is based on the actual steam temperature.

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BoilerManual #BypassSystem #Section7 #Page3

To understand the need for a bypass system, the difference between the UP boiler and typical drum type natural circulation boiler should be considered.

DRUM TYPE BOILER

During the startup of the drum type boiler, the boiler is filled to a normal water level in the steam drum and firing is initiated. A steam/water mixture is generated in the tubes in the high heat input areas of the furnace. The steam/water mixture is less dense than the water being supplied to the furnace water walls. The steam/water mixture is forced upward by the denser water in the supply circuits and a natural circulation effect is created. As more heat is added, circulation is established in the boiler, with steam being generated in the riser tubes and being replaced by water from the supply tubes.

Those tubes which are in hotter areas of the furnace generate more steam than tubes in cooler furnace areas thus, carry a higher flow. The natural circulation effect provides more flow to the tubes in the hotter areas keeping them cooled to safe limits and preventing overheating.

UNIVERSAL PRESSURE BOILER

The UP boiler is a once-through unit. Flow is controlled entirely by the boiler feed pumps. There is no natural circulation effect to offset imbalanced heat inputs to the furnace. To prevent overheating of tubes in the high heat input areas, a minimum design flow and pressure must be maintained in the furnace circuits. Minimum flow is 33% (1,400,000 lb./hr) of full load flow. This minimum flow must be maintained anytime the unit is fired.

Early in the startup sequence, turbine steam requirements are much

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#BoilerManual #CycloneOperation #Section6 #Page3

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Alt = Image of a complex logic diagram is sideways with the bottom along the right edge and top along the left edge. Labeled Fig. 1 Fuel and air flow control--cyclone firing. Label is off to the bottom right of the diagram.

#BoilerManual #CycloneDescription #Section5 #Page3

3. Primary Air Damper (Figures 1 & 3) - 12-17% of the total air to the cyclone enters the radial burner tangentially and imparts a whirling motion to the incoming coal. This cyclonic action moves the coal out of the burner throat and into the cyclone.

4. [b]Tertiary Air Damper (Figures 1 & 3) - 4-6% of the total air to the cyclone is admitted at the front of the burner and is used basically for cooling the burner front.

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Alt = Labeled Fig. 2 Cyclone furnace. The drawing is identical to Section 3's Fig. 6 but labeled and marked somewhat differently. What was marked as "Coal inlet" is now marked "Crushed coal inlet." Only the Cyclone barrel is marked as such with no marking for its neck. Furnace wall, Sec. air, Furnace wall tubes, and Windbox are pointed out on the left in top down order, and coming out of the windbox is marked Primary-tertiary air duct, but somewhat upward from that is marked the Primary-tertiary air shut-off damper (inside duct). the Crushed coal inlet rises from what's marked as Radial burner.

#BoilerManual #Lighters #Section4 #Page3

The air cylinder operates on compressed air supplied at 80 - 125 psi. The air must be clean and dry to keep the cylinder functioning properly. Flow control valves are used to control the speed of the piston stroke. {A word about the air compressors used to supply this and workshop functions: Taking air from the atmosphere and compressing it will precipitate its moisture content and there are moisture traps located in various places along the compressed air pipes. When they malfunction, they're repaired or replaced.}

Other air valves are mechanically operated by the cylinder drives. The pressure signal from these valves are used for position indicators and interlocks. The oil valve will open only when the atomizer is fully inserted and will close when it is retracted, based on the signals through these air valves.

The oil spray is ignited by the high energy spark ignitor. Power to this ignitor is supplied from a transformer based on a pressure signal from the mechanical valves on the air cylinder drive. Electricity flows the length of the probe to the spark gap.

The 10,000 volt, 23 milliampere spark created across the 1/8 inch gap ignites the coal. The lighter can use Number 1 and 2 fuel oil. The fuel oil must be passed through a 60 mesh strainer and supplied to the atomizer at 150 to 250 psi.

The lighter capacity can be varied to some extent by varying the fuel oil supply pressure between150 and 250 psi. The oil capacity of the lighter is 900 lb/hr and requires a size 3820M mechanical sprayer plate.

In addition to cylinder drive air, the lighter requires seal and purge air supplies. The air supply to the lighter seal requires six SCFM of air suplied and a pressure of at least 2 inches of water greater than the windbox pressure. This seals the lighter assembly against dust or ash accumulations which could hinder lighter movement.

Purge air requires approximately 5.5 SCFM {Standard Cubic Feet per Minute} of air at 50 psi to purge fuel oil from the supply lines and atomizer when the lighter is removed from service. This prevents fuel oil from draining into the burner and windbox

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#BoilerManual #AirAndGasFlow #Section3 #Page3

Outside air (at ambient temperature) is drawn into the Forced Draft (FD) fans and propelled through the Tubular Air Heater (AH) where it is preheated. This preheated air is referred to as Secondary or Combustion Air, and mixes with the fuel at the cyclone. There are actually three separate air flow paths entering the cyclone. We will discuss all three later in this section. Within the cyclone, the fuel/air mixture is ignited and combustion by-products (gases) are produced.

These gases, commonly called flue gases, are drawn out of the boiler by the Induced Draft (ID) fans. As the flue gases pass through thte pendant (hanging) and horizontal convection surfaces, heat is given up by the gas and transferred to the tubes. The mechanics of heat transfer are discussed later in this section.

Upon exiting the boiler, the flue gases first pass through the tubular air heater, then through the precipitator. From the precipitator, the gases are drawn through the ID fans and exits to the atmosphere through the stack. The expected operating pressure and temperatures throughout the air and gas system are tabulated in Table 1.

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#BoilerManual #FluidCirculation #Section2 #Page3

It must be remembered that heat and temperature are not the same thing. A considerable amount of heat is added to this mixture while its temperature holds constant at saturation. Even though the temperature is holding constant, this heat is not disappearing or being wasted, it is converting water to steam.

There are various stages in the process as water is converted to steam so a steam/water mixture will exist. Steam quality is a term that refers to the percntage of the mixture that has been converted to steam. A 40% quality means that 40% of the water has been converted to steam. The broken lines in Figure 3 indicate the range of steam qualities. From saturated water 0% quality (Point A) water goes through a water to steam conversion between points A and B. Saturated steam exists at point B at a quality of 100%.

If additional heat is added beyond the point of saturated steam, point B, the temperature will again begin to rise for any constant pressure as showin in Figure 3. Anywhere beyond the saturated steam line, steam is said to be superheated from points B to C.

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Alt = Figure 3 labeled Steam quality. The graph is incremented identically to Figure 2 but point A is labeled "Saturated water (0% quality" at the intersection of the 600 degree temperature mark and the 600 Btu/lb mark, while Point B is labeled "Saturated steam (100%) quality)" but the line between the two points is labeled 1500 psi. There is a Point C in the upper right corner of the graph, tracing a curve between it and Point B labeled "Superheated steam".

@Su_G #BoilerManual #UnitDescription #Section1 #Page3
"
vessel. This design would limit the consequences of a pressure part rupture.

While several water tube boiler designs were patented between the late 1700's and the mid 1800's, it was not until 1856 that a significant breakthrough occurred. The design incorporated inclined water tubes connecting water spaces at the front and rear of the furnace with a steam space above. It provided better water circulation and more heating surface than other designs, along with a reduced steam explosion hazard.

Steam was originally used for local heat and power generation. With the advent of practical electric power generation and distribution, utility companies were formed to serve customers over wide areas {see also the Rural Electrification Authority--REA--movement considerably later}. The first such electric generating station in America was the Brush Electric Light Company in Philadelphia. Four 73 hp {horse power} B&W boilers were installed in this plant in 1881. The first utility plant to use steam turbine exclusively for electric power generation was the Fisk Steet Station of Commonwealth Edison in 1903. Ninety-six B&W boilers, rated at 500 hp each, drove the turbines. The boilers operated at 170 psi {pounds per square inch} and 70 F superheat.

Boiler size and unit efficiency are, of course, much greater today than in the early 1900's {keep in mind that this manual is circa 1980s} Several technical advances have made these increases possible. Primary among these is the use of water cooled furnace walls. The water cooled walls greatly reduce refractory maintenance problems {this reads as "insulationary maintenance problems"}, lower gas temperatures leaving the furnace, help reduce fouling and slagging {again, to be explained later} and provide more heating surface with better circulation characteristics to generate more steam.

Improvements in metal technology and separation devices have allowed the use of higher operating pressures and higher steam temperatures for increased capacity and higher efficiency. The increasing use of economizers, air heaters, feedwater heaters, and multi-stage turbines with reheaters have also greatly improved cycle efficiency. Also,
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Ink Diaries: The Promotion Wheel Starts Turning.

Check out this video interview with Ink cast member Stephanie Almeida who plays Stephanie Rahn, The Sun’s first Page 3 girl after Murdoch took over the paper and kicked his climb and our decline into gear.

https://www.actionnews5.com/video/2023/03/07/bluff-city-life-tuesday-07-march-pt-2-8/

#theatre #Ink #StephanieRahn #RupertMurdoch #Page3