Pratica di Shadowing: Power Plant | How it Works Power Plant Steam Cycle - Impara a parlare inglese con i video
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Music In
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a power plant, the steam cycle is essential to the production of electricity.
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The boiler heats water to produce steam, and the turbine uses the steam to turn the generator, which produces electricity.
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The condenser turns the steam back into water and the cycle begins again.
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In this part we'll take a look at boilers.
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A boiler does two things.
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It burns fuel to produce heat and it uses this heat to turn water into steam.
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From the outside boilers look like big boxes.
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Some may be over 200 feet tall.
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This boiler is called a drum type boiler because it has a component called a steam drum on top.
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The drum collects the steam made by the boiler.
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The walls of vertical metal tubes that line the inside of the boiler are connected to the steam drum.
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These tubes are frequently referred to as water walls because they're filled with water.
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The steam that's used to drive the turbine is produced in the water walls.
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The water walls surround an open area in the boiler that's called the furnace.
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This is where combustion occurs, that is, where the fuel is burned.
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The burners that supply the fuel to the furnace are usually located either in the corners
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or on the sides of the furnace.
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These burners are designed to burn coal.
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If your plant uses oil or natural gas, the burners will be somewhat different.
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Now that we've seen where combustion takes place, let's turn our attention to the requirements for combustion.
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A boiler needs a continuous flow of fuel and air in order to maintain the fire in the furnace.
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Let's look at a typical boiler and see how fuel and air are supplied.
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We'll start with the fuel, which in our example will be coal.
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A conveyor system carries the coal from the coal yard to the plant.
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At the plant, machines called pulverizers grind the coal into a fine powder.
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There are several kinds of pulverizers, so your plant may use a type that looks different from this one.
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Once the coal is in the form of a fine powder, it can be delivered to the boiler.
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Let's look at an illustration of a boiler and its support systems to see how this can be accomplished.
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In this example, the pulverizer is located here.
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Air is blown into the pulverizer to carry the powdered coal to the boiler.
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In this example, an exhauster is also included and helps draw the coal out of the pulverizer.
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The flow of air through the pulverizer carries the coal into the burners in the boiler.
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Additional air is blown into the furnace by forced draft fans.
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This ensures that the proper amount of air is in the furnace to support the combustion of fuel.
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Once the fuel is blown into the furnace, it is ignited.
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The heat in the furnace raises the temperature of the water in the water walls.
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A mixture of steam and hot water rises up into the steam drum.
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In the steam drum, the steam is separated from the water.
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The water recirculates back to the water walls through large pipes called downcomers.
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After the steam is further heated by heaters called superheaters, it flows from the boiler to the turbine.
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This is what a typical turbine looks like.
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A turbine converts the energy from the steam that flows through it to mechanical energy that turns a generator.
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The main steam line from the boiler enters the turbine here.
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The generator is connected directly to the turbine by a shaft.
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In this cutaway drawing of a turbine, you can see the blades located inside.
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Each set of rotating blades is commonly called a wheel.
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Stationary blades, sometimes called diaphragms or nozzles, help direct the steam from one set of rotating blades to the next.
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The stationary blades look similar to the rotating blades, but they are attached to the turbine casing and they don't move.
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As the steam passes through the turbine, the stationary blades direct the steam to the rotating blades causing them to turn.
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The steam gives up thermal energy, or heat, and pressure.
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The rotating blades cause the turbine shaft to spin, and that turns the generator.
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After the steam from the boiler gives up much of its energy in the turbine, it flows into the condenser.
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A condenser is a large heat exchanger.
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It removes heat from the steam and converts the steam back to water.
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We'll use this illustration to explain how a condenser works.
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Inside there are many small tubes with cold water running through them.
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As steam is exhausted from the turbine, it passes over the tubes, is cooled, and condenses into water.
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The water which is called condensate drips into the bottom of the condenser.
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The area at the bottom of the condenser is called the hot well.
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A system called the condensate feed water system completes the steam
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cycle by sending the water back to the boiler where it becomes steam again.
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Because the water is used over and over, the steam cycle is called a closed system.
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The condensate feed water system is actually made up of two systems.
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The condensate system removes the condensate from the hot well.
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Then the feed water system feeds it back to the boiler.
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The water that is pumped into the boiler is called feed water.
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It replaces the water that leaves the boiler as steam.
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In addition to pumping water from the hot well back to the boiler, the condensate feed water system also heats the water.
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This increases the efficiency of the cycle.
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The water is heated by heat exchangers called feed water heaters.
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They use steam extracted from the turbine as their heat source.
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This steam is referred to as extraction steam.
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Another important system associated with the condenser is the circulating water system.
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This system supplies the water that flows through the condenser tubes.
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The condenser circulating water system can be either an open system or a closed system system.
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In an open system, the water comes from a large body of water such as a lake, a river or an ocean.
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It passes through the condenser tubes where it picks up heat from the steam.
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Then it's returned to the source.
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So the water flows through the condenser only one time.
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In a closed system, the same water is used over and over again.
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A cooling tower is used instead of a large body of water.
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The water
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that passes through the condenser tubes continues on to the cooling tower where it is cooled by air
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that flows through the tower.
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The cooled water then passes back through the condenser tubes to repeat the cycle.
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Another system we need to discuss is the make-up water system.
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Its job is to replace water that's lost from the steam cycle.
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Valves, pumps, piping, joints, and other parts involved in the steam cycle can all leak.
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Since it's impossible to prevent all leakage, water must eventually be added to replace the water or steam that leaks out.
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When more water is needed, the makeup water system feeds it into the condensate system.
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Water that's used in the steam cycle must be purified to keep scale and foreign material from accumulating in the boiler.
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The make-up water system purifies the water, which is then stored in tanks until it's needed.
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In this topic, we looked at three important components involved in the power plant's steam cycle.
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The boiler, the turbine, and the condenser.
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We also discussed some systems that support the steam cycle.
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The boiler fuel and air systems, the condensate feed water system, the condenser circulating water system, and the make-up water system.
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Take some time now to answer some practice questions about what was covered in this topic.
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From the outside, boilers look like big boxes.
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Some may be over 200 feet tall.
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This boiler is called a drum type boiler because it has a component called a steam drum on top.
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The drum collects the steam made by the boiler.
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The walls of vertical metal tubes that line the inside of the boiler are connected to the steam drum.
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These tubes are frequently referred to as water walls because they're filled with water.
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The steam that's used to drive the turbine is produced in the water wall.
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In this cutaway drawing of a turbine, you can see the blades located inside.
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Each set of rotating blades is commonly called a wheel.
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Stationary blades, sometimes called diaphragms or nozzles, help direct the steam from one set of rotating blades to the next.
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The stationary blades look similar to the rotating blades, but they are attached to the turbine casing and they don't move.
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The condensate feed water system is actually made up of two systems.
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The condensate system removes the condensate from the hot well.
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Then the feed water system feeds it back to the boiler.
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The water that is pumped into the boiler is called feed water.
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It replaces the water that leaves the boiler as steam.
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Steam flows from the boiler to the turbine because of differences in pressure.
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Steam like any other gas or liquid moves from areas of high pressure to areas of low pressure.
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The steam pressure is at its highest as it exits the boiler.
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The high pressure in the boiler pushes the steam out through the main steam line, through the turbine and into the condenser.
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As the steam gives up its energy in the turbine and is converted into water in the condenser, the pressure drops dramatically.
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When steam first enters the condenser, it fills the available space, but as the steam condenses, taking up less and less space,
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a vacuum or negative pressure is created in the condenser.
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This negative pressure tends to draw more steam through the turbine and into the condenser.
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Once the steam is condensed into water or condensate, it collects in the hot well.
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Now the condensate has to be moved from the low pressure
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area in the condenser back to the high pressure area in the boiler.
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This is done with a series of pumps in the condensate feed water system.
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One pump called the condensate or hot well pump removes water from the hot well.
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Next, the feed water pump pushes the water into the boiler.
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Some plants use a third pump called a condensate booster pump between these two.
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Each pump along the line adds pressure to the water.
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By the time the water leaves the feed water pump, its pressure is high enough to overcome the pressure in the boiler and the water is forced into the boiler drum.
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There is a relationship between steam flow through the turbine and the demand for electric power on the power generation system.
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This relationship is helpful in understanding why steam flow has to be controlled.
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Basically, if more power must be generated to meet an increase in demand,
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steam flow must be increased to cause the turbine to work harder to turn the generator.
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On the other hand, if less power is required, steam flow must be decreased.
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Another reason that controls are necessary is
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that the amount of steam flow to the turbine and the amount of water pumped back to the boiler must be equal.
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If they aren't, then either the boiler or the turbine will be damaged.
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Let's see why.
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Let's say that the amount of steam going to the turbine
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and the condenser is greater than the amount of water pumped back to the boiler.
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As a result, the water level in the boiler drum drops.
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Boiler tubes are constantly exposed to intense heat in the furnace.
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In fact, the temperature is so high that it could melt the tubes.
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The reason the tubes don't melt is that the water and steam flowing through them keep the tubes cool.
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If feed water flow doesn't keep up with steam flow, water boils off faster than it's replaced.
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Eventually, there won't be enough water to keep the tubes from overheating and failing.
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In this case, the boiler drum water level would rise.
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In a short time, this excess water would be carried out of the boiler drum
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along with the steam to where it could damage components such as the boiler super heaters.
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Damage from mismatched steam
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and water flows can be prevented by controlling the flow of steam entering the turbine
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and the flow of feed water to the boiler.
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The turbine steam control valves are located in the main steam line to the turbine.
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They are used to regulate the flow of steam into the turbine.
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In this illustration of a typical turbine, the steam control valves are located here.
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If more power is needed from the generator, the valves are opened wider.
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This causes more steam to flow through the turbine, more mechanical energy to be received by the generator, and more electric power to be produced.
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The reverse occurs when the steam control valves are closed down more.
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When the steam flow is varied, the feed water flow to the boiler must be varied equally.
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In this system, feed water flow to the boiler is controlled by a valve in the feedwater line going to the boiler.
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The feedwater control valves are opened and closed to match feedwater flow with steam flow.
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In some plants, this control is accomplished by varying the speed of the feedwater pump.
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Other plants use a combination of both methods.
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Regardless of which method is used, the important point to remember is that steam flow and feedwater flow must be controlled so that they're balanced.
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A specific amount of heat is needed to produce a given amount of steam.
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The source of that heat is the fuel that's burned in the boiler furnace.
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Therefore, a specific amount of fuel is required to produce a given amount of steam.
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Boiler fuel systems are designed to control the amount of fuel supplied to the boiler.
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In this part, we're interested in the basic idea of how a fuel system works.
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To illustrate this, we'll look at an example of how the amount of coal going to the burners of a typical coal-fired boiler is controlled.
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Coal is ground into a fine powder in a machine called a pulverizer.
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Usually, several pulverizers are provided for each boiler.
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From the pulverizer, the powdered coal is blown into the boiler furnace and burned.
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Coal is fed into the pulverizer by a device called a coal feeder, which is located above the pulverizer.
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There are several different types of feeders.
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This is an illustration of one type of coal feeder.
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In this feeder, paddles move around, dumping coal into the pulverizer.
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Controlling the speed of the paddles controls the flow of coal.
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If more coal is needed, the speed of the paddles is increased.
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If less coal is needed, the paddles are slowed down.
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Boilers using oil or gas have regulating valves that vary the flow of fuel.
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When the amount of fuel increases or decreases, the air flow into the boiler must also increase or decrease to ensure proper combustion.
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This can be done by adjusting inlet vanes
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or discharge dampers on the fans that supply air to the boiler or by adjusting the speed of the fans.
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The operation of a boiler involves balancing various flows such as the flows of steam
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and water and the flows of fuel and air.
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But at any time the unexpected can happen, disrupting normal boiler operation.
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If such an event threatens the safety of people or equipment in the plant, you're faced with an emergency condition.
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Most plants have written step-by-step procedures for responding to emergency conditions.
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It's important that you know your plant's procedures and follow them.
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But since a procedure can't be written for every problem, you'll have to understand how your plant works in order to know what's happening
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and be able to take the right corrective action.
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Let's examine the general actions that should be taken during any plant operation emergency.
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Basically, there are three actions.
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First, determine the nature of the emergency condition.
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Second, put the plant in a safe condition.
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And third, return the plant to normal.
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We'll start by discussing how to determine the nature of the emergency condition.
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An operator's first indication that something is wrong is frequently an enunciator alarm.
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The alarm system monitors levels, temperatures, pressures, and flows in plant systems.
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If a variable exceeds a preset limit, an alarm sounds and an annunciator window lights in the control room.
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To find out what caused the alarm, the operator must check other indicators to determine the status of the system involved and any associated support systems.
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Then he can take the next step, putting the plant in a safe condition.
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If there is immediate danger, the operator must take immediate action to protect equipment and personnel.
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At this point, the emergency has been handled.
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But there's a third step.
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The plant must be returned to normal.
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Now that we've covered three general steps for dealing with a plant operation emergency, we'll apply them to a specific emergency.
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The loss of fire or flame out in a boiler is an emergency condition that requires immediate action.
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Frequently, operators can see the flame directly from the control room or on a television monitor.
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Some boilers have flame scanners which are electronic devices that monitor the flame.
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If a flame out occurs and immediate action isn't taken, steam pressure drops.
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That's because the heat input to the water in the boiler has stopped, causing steam production to stop.
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After it has been determined that a boiler flame out has occurred, the next step is to put the plant in a safe condition.
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The real danger with the flame out is
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that a combustible mixture of fuel and air can collect in the boiler
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because fuel and combustion air are still being fed into the furnace.
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If the operator simply relights the burners, the boiler could explode.
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In this case, to make the plant safe, you must first stop the flow of fuel into the boiler.
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Then you have to get rid of all the unburned fuel before relighting the burners.
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This is done by using the air flow through the furnace to blow the the fuel out, an operation called purging.
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After the boiler has been purged, you must perform the third step, returning the plant to normal.
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In this example, that involves relighting the burners and increasing boiler steam pressure to normal.
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If for some reason the burners can't be relit, the unit must be shut down.
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Keep in mind that you must know your plant's emergency procedures in advance.
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If you wait until an emergency occurs to study them, it's too late.
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In this topic, we saw how steam and water flows through the steam cycle and how this flow is controlled.
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We also discussed the basics of how the flow of fuel to a boiler is controlled.
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And we discussed some basic steps for handling a plant operation emergency.
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This is a good time to check your understanding with some practice questions.
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Steam flows from the boiler to the turbine because of differences in pressure.
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Steam, like any other gas or liquid, moves from areas of high pressure to areas of low pressure.
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There is a relationship between steam flow through the turbine and the demand for electric power on the power generation system.
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This relationship is helpful in understanding why steam flow has to be controlled.
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Basically, if more power must be generated to meet an increase in demand,
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steam flow must be increased to cause the turbine to work harder to turn the generator.
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On the other hand, if less power is required, steam flow must be decreased.
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When the amount of fuel increases or decreases, the air flow into the boiler must also increase or decrease to ensure proper combustion.
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Let's examine the general actions that should be taken during any plant operation emergency.
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Basically, There are three actions.
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First, determine the nature of the emergency condition.
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Second, put the plant in a safe condition.
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And third, return the plant to normal.
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Contesto e sfondo
Il video spiega il funzionamento del ciclo di vapore in un impianto elettrico, focalizzandosi su caldaie e turbine. È una risorsa eccellente per gli appassionati di scienza e tecnologia, ma anche per chi vuole migliorare l'inglese tecnico e la comprensione auditiva. I concetti sono spiegati in modo chiaro, con termini specifici ma accessibili, il che lo rende perfetto per esercitarsi con tecniche come lo shadowing in inglese.
5 frasi chiave per la comunicazione quotidiana e tecnica
- "The boiler heats water to produce steam" (La caldaia riscalda l'acqua per produrre vapore): utile per descrivere processi industriali.
- "The turbine uses the steam to turn the generator" (La turbina usa il vapore per far girare il generatore): fondamentale per capire la produzione di elettricità.
- "A continuous flow of fuel and air" (Un flusso continuo di carburante e aria): frase chiave per parlare di combustioni e sistemi meccanici.
- "Pulverizers grind the coal into a fine powder" (I polverizzatori macinano il carbone in una polvere fine): termine tecnico utile per descrivere macchine industriali.
- "Stationary blades direct the steam to the rotating blades" (Le pale fisse dirigono il vapore alle pale rotanti): essenziale per spiegare il funzionamento delle turbine.
Guida passo passo allo shadowing per questo video
Lo shadowing in inglese è un metodo fantastico per migliorare la pronuncia inglese e l'intonazione. Ecco come affrontare questo video in modo efficace:
- Ascolta il video una volta intero: Concentrati sul contesto generale, non sulle parole singole. Nota il tono e il ritmo della voce.
- Seleziona un frammento di 30 secondi: Scegli una parte con frasi semplici, come la descrizione della caldaia o della turbina. Ripeti il frammento più volte finché non lo capisci bene.
- Imita immediatamente dopo il parlante: Usa la tecnica dello shadow speech: ascolta una frase, pausa e ripettala subito, cercando di copiare il tono e la pronuncia. Non ti preoccupare di errori: l'importante è l'immediaticità.
- Confronta la tua versione con il video: Nota le differenze nella pronuncia di parole come "pulverizers" o "turbine". Usa un shadowing site per registrare la tua voce e confrontarla con l'originale.
- Ripeti il processo ogni giorno: Dedica 10 minuti al giorno a questo esercizio e noterai progressi in poche settimane. La costanza è la chiave per migliorare la pronuncia inglese!
Con questo video, non solo impari termini tecnici utili, ma anche eserciti la tua capacità di ascoltare e ripetere in tempo reale. Lo shadowing è un modo divertente e efficace per avvicinarti all'inglese fluido: iniziamo oggi stesso!
La grammatica di questo video
Le strutture che chi parla usa di più, con le parole esatte del video:
| Struttura | Nel video |
|---|---|
| Forma passiva be + participio passato — conta ciò che accade, non chi lo fa | is called · are connected · is produced |
| Present perfect have/has + participio passato — un’azione passata che conta ancora adesso | we've seen · have written · has been handled |
| Frasi relative who / which + frase — un’informazione in più su una persona o una cosa | water which is · water, which is · feeder, which is |
Cos'è la tecnica dello Shadowing?
Shadowing è una tecnica di apprendimento delle lingue supportata da studi scientifici, originariamente sviluppata per la formazione dei traduttori professionisti e resa popolare dal poliglotta Dr. Alexander Arguelles. Il metodo è semplice ma potente: ascolti un audio in inglese di madrelingua e lo ripeti immediatamente ad alta voce — come un'ombra che segue il parlante con un ritardo di solo 1–2 secondi. A differenza dell'ascolto passivo o degli esercizi di grammatica, lo shadowing costringe il tuo cervello e i muscoli della bocca a elaborare e riprodurre simultaneamente i modelli di discorso reale. La ricerca dimostra che migliora significativamente la precisione della pronuncia, l'intonazione, il ritmo, il discorso connesso, la comprensione dell'ascolto e la fluidità del parlato — rendendolo uno dei metodi più efficaci per la preparazione alla prova di speaking dell'IELTS e per la comunicazione reale in inglese.