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Welcome to the virtual tour of the MSU power plant. Michigan State University has a cogeneration plant that generates all the electrical power for the university. They supply all the heat to campus by steam lines. In the summer the steam is used to run LiBr refrigeration units for air conditioning -- Yes you can use heat to cool....Here are some photos of the power plant.
Aerial View of the T.B. Simon Power Plant.
Please be patient as this page loads. I have scanned a large overall process schematic and an enlarged portion of boiler 1 and turbine 1 to enable you to see detail.
MSU runs four boilers and four turbines. The overall process schematic shows the flow schemes but it is difficult to see a much stream detail on the overall schematic. The legend is small to read so I provide here most of the legend:
Here is a close-up of the cycle for turbine1.
Note that the superheaters share the same boiler housing as the regular steam. The superheaters are the serpentine shaped tubes at the top of the boiler. The steam passes through the superheaters just before it exits.
Note there is an open feedwater preheater (deaerator) and a closed feedwater preheater for each cycle. Exercise: Scroll back up to the overall schematic. What is different about the steam cycle for turbine number 3? Answer at bottom of page.
Note that the 90 psig steam that is fed to the campus (see bottom of overall schematic) returns as condensate and is cleaned up and fed into the open feedwater preheater. In one sense the campus is acting like a condenser for the power plant! On the other hand it is getting heat without having to maintain furnace or boiler equipment for each building. The fact that campus acts like a condenser is important. MSU is not near a large enough body of water to pull cooling water from it. They are not permitted (and would not want) to raise the temperature of the Red Cedar river. Therefore they have to use some of the power they generate to run cooling towers to chill the water. Cooling towers are the large, industrial-looking rectangular structures that you often see water vapor emanating from at all times of the year. If you drive by the power plant you will see them across from the power plant, on the north side of service road. Remember the psychometric charts from your material and energy balance course? Evaporation causes cooling. Here is a photo of a the cooling towers. Here is another photo.
Ion Exchange. Inlet water has to be treated to remove anions and cations. Here is a picture of the cation exchange units using ion exchange resins. They work on the same principles as home water softeners. The anion resin tanks are larger and not shown.
Open Feedwater Preheaters. After pretreatment,
the inlet water passes through the open feedwater preheaters (deaerators).
The open feedwater preheaters have an upper section that has some
trays and the inlet water flows across them. Steam is sparged up
through them. The heating decreases the solubility of the
dissolved oxygen as well as preheating the water. Here are some
Photo1 shows the overall layout with the upper section at the top and the lower tank below.
Photo2 shows the upper trayed section from a little closer. The inlet piping is on the back side that isn't shown.
Closed Feedwater Preheaters. Steam at 185 psig is extracted after a few turbine stages and sent to a closed feedwater preheater. This heat exchanger is a tube-in-shell design. The use of the open and closed feedwater preheaters is important for reasons discussed in the text.
Coal is dumped from an automatic scale in 200 lb batches into the mills where it is ground to a fineness resembling baby powder.
Ball Mills. The power plant has two types of
mills: ball mills and attrition mills. A ball mill uses steel
balls about the size of bowling balls that run in a race (another
name for a track) and crush any coal that is in their way! Here
are some photos:
Balls - These are solid steel balls about a foot in diameter! The powerplant has several sets that they use in different sizes races as the balls wear down. These are a little dusty.
Race close-up - This is the race that the balls roll in. The upper race holds the balls in place. The grooves allow the coal to drop down into the race.
Race - This photo gives a better perspective on the overall size of the races. They are about 5-6 feet in diameter.
Ball Mill - Now the race is held within the ball mill housing.
Ball Mill motor - It takes a lot of power to turn the ball mill. Here is a motor. The lower race is the the one that actually turns. Look in this photo for: (1) The pushbutton in the front of the picture that is the size of a standard light switch - compare with the motor to see how BIG it is!; (2) look at the coupling area to see where the motor shaft passes into the mill to turn the lower race.
Attrition Mills. The other type of mills that the plant uses are attrition mills that work on the principle of repeatedly passing the coal through a series of steel fingers, some fixed and others rotating. The coal gradually breaks into powder. The outlet of the mill includes a blower that blows the fine powder up to the boiler furnace. This is a picture of one side of an attrition mill that is being serviced. Notice the inlet chute where the coal drops down the chute into the mill and also notice the green motor that drives the mill and blower. When the coal is finely ground it moves to the blower section to the left and is conveyed up the round pipe to the boilers. Here is another picture of the mill from the other side. On the rightmost rotor of this picture you can see the centrifugal blower impellers that move the air and pulverized coal into the conveying pipe.
The crushed coal is conveyed pneumatically using primary combustion air into the furnace side of the boiler. The boilers are about 4 stories high so they can't fit in a picture! This picture shows the burner feed entrance lines that convey the coal. Notice that the boiler is just a square structure! You can see the exterior steel walls. Inside the walls is layer of refractory brick and then the boiler tubes line the walls. Most of the inside is empty! Secondary combustion air is blown up the center to keep the coal stirred up and the ash off the walls.
Combustion air blowers supply air to the furnace side of the boilers. The blower is in the round housing. Note the motor attached to the blower. The combustion air is carried up through the rectangular ducts. These blowers are on the bottom floor below the furnaces. All this building air being blown into the furnaces by these blowers and the coal conveyers creates a slight vacuum in the building relative to outside!
After the steam is superheated, it enters the turbines. Here is a picture of turbine4. The silver pipe going in the side is the 850-870 psig superheated steam inlet. The turbine is contained in the square box in the left. The 185 psig outlet and the 90 psig outlet are below the floor and can't be seen in the picture. The round housing immediately to the right of the square turbine box directs the outlet steam to the condenser that is immediately below the floor (the location will be more obvious from looking at turbine 1 picture to be shown below). There is a shaft that connects to the generator that is in the long cylindrical housing. The smallest circular housing on the far right contains a smaller DC generator that supplies current to electromagnets within the generator. If you look back at your physics book you will recall that moving a wire near a magnet causes current. In a generator, a turning shaft moves windings of wires by electromagnets to generate voltage and current. In this case the voltage supplied to campus is 13,800 V! Most buildings south of the river step this voltage down at the building. North of the river there is a distribution station where the voltage is stepped down for the older buildings. Vitually all the wires are underground. (Yes MSU is one of the most beautiful campuses in the country and this helps!)
Here is a picture of turbine3. Note how much shorter this turbine is compared to turbine 4. Again, the turbine is in the square housing. At the top of the square housing you can see some rocker arms. These rocker arms control throttle valves that regulate the inlet steam flowrate.
Here is a picture of turbine1. Turbines 1 and 2 are identical and the oldest turbines. Note the rounded housing at the turbine outlet that connects directly to the white cylindrical condenser immediately below the floor. The condenser is directly attached to assure a minimum pressure difference since the condenser is maintained at subatmospheric pressure.
Here is a turbine outlet condenser right below another of the turbines. The cooling water enters in the large pipe on the left, makes a pass down the length of the heat exchanger, is redirected back to this end making a second pass and then exits on the right. This is known as a two-pass heat exchanger. This condenser is very important for keeping a low pressure on the turbine outlet. By keeping the temperature low, the pressure will be low -- remember the phase rule? Note the access flanges provided in the end of the heat exchanger for maintenance.
If you are interested in more details of turbines including pictures of turbine 3 and generator 3 taken apart, then follow this link to turbine details.
Steam for heating (90 psig) leaves below the turbine area through a pair of 30 inch steam lines. This picture is taken from the floor below the turbines looking up at the steam lines. Why are there two lines? Answer at bottom of page.
Steam leaves the power plant through a steam tunnel. There is always a strong HOT wind coming into the power plant from the tunnel due to the slight vacuum in the plant. Vacuum? Review why in the discussion of combustion blowers above.
There are several air compressors in the plant to furnish compressed air. This particular unit compresses air to 400 psig. This air is used periodically though the day to blow any ash deposits off the inside walls of the furnace (where the boiler tubes are) to maintain good heat transfer. The drive motor is gray. The compressor is within the circular green housing.
Thanks for joining us on this tour! Thanks to Mr. Roy Gies of the MSU Power Plant for his willingness to share the facilities and make it educational! Schematics courtesy of the MSU Power Plant. Web page assembled by Prof. Carl Lira, Michigan State University, Department of Chemical Engineering.
Answer to what is different about turbine 3: there isn't a condenser. The outlet is used for 90 psig steam only.
Answer to why there are two steam lines: in case one needs to be serviced the campus will never be without heat!
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