"Whether you are shivering with cold or too hot, sleepy or wide-awake, spoken well or badly, dying, or doing anything else, do not let it interfere with doing what is right. For whatever causes us to die is also one of life's processes. Even for this, nothing is required of us than to accomplish well the task at hand." - Marcus Aurelius
The previous Career Autobiography post is here:
I didn't work at the coal-fired plant for as long as I would have liked to. There were a number of reasons that I moved on from that job - there was no single deal-killer, but all of the reasons combined added up to the need for making a change.
The plant manager who had originally hired me got a promotion, and his replacement was an absolute prick. One of his favorite pastimes was threatening people's job. No matter the issue - health problems, family problems, reporting a problem with the equipment, his first move was frequently to threaten the employee with job loss. All the wonderful and talented employees who had trained me at my first legitimate utility-type power plant began leaving. In one year, half the operators and more than half of the maintenance guys had quit. Each of them moved away took jobs commissioning new gas turbine combined cycle power plants.
In addition to frequently having my livelihood threatened whenever there was a hiccup at work, the California Energy Crisis had made the career at the little ACE Cogeneration plant very fragile. The power was sold under an exclusive contract to a single customer, Southern California Edison (SCE).
SCE and Pacific Gas & Electric, The state's two big utilites, were both suffering from the same problem: They could only charge residential customers fixed rates, but they had to pay variable rates for wholesale electricity. Wholesale electricity prices were being manipulated by the likes of Enron, and these two utilities were paying exorbitant rates for wholesale electricity. They were rapidly going broke, because they couldn't recoup those expenses from the residential and commercial customers.
To preserve its dwindling cash, SCE hadn't paid our little power plant for electrical power in 90 days - which is seriously in arrears for a business customer. Our small generating plant was giving SCE free electricity, while continuing to purchase train-loads of coal, and continuing to pay our salaries. At one point the company owners held a staff meeting, where we were informed that they had halted purchasing coal. The owners intended to burn our coal pile down, and that if nothing changed by the time it ran out, the plant would be shut down, and would be laid off. The coal pile at that point was going to last approximately 60 days.
I set about finding another job, because:
- I had a house payment to make, and the job no longer looked stable
- Gas Turbines seemed like a more promising career path than burning dirt
- I don't like working for jerks who threaten my livelihood on a whim
- All the people with any kind of ambition had already quit
We sold our house on acreage and moved into a tract house in Bakersfield, California - for what I hoped would only be a couple of years. This turned out to not be the case.
I had intentionally hired on with what I thought was a large and stable company, a company that owned a fleet of power plants scattered all over the country. Unfortunately, this company would soon dissolve (due to the very same California Energy Crisis) and the power plants would be sold off to various vulture investors. As a result, we ended up staying in Bakersfield much longer than I ever dreamed.
The new job was at a brand-new power plant that was then under construction - the La Paloma Generating Plant. The plant consisted of four generating units, each making 262 Megawatts, for a total of 1048 Megawatts - making it the largest power plant that I've worked at to date.
The plant's construction was behind schedule and way over budget - the final cost was on the order of $1 billion, when it probably should have cost 700-750 million. However the power plant design held tremendous potential. La Paloma used gas turbines that were new, interesting, and unusual. They were manufactured by the European firm ABB (acquired by Alstom Energy), to compete with the General Electric 7FA turbines that were being installed, seemingly everywhere.
There were a number of interesting features with the power train, and I'll start with the gas turbines. GE turbines compress air to about 200 psig, then use fourteen combustion cans to do the work of mixing and igniting the fuel. It's a rugged and reliable arrangement that GE perfected over decades of manufacturing heavy industrial turbines.
The ABB/Alstom turbines were much more advanced - and finicky and untested. They compressed the air to about 700 psig, injected fuel, and burned it in an annulus - similar to aircraft engines. The exhaust gas passed through a single turbine stage, and then more fuel was added and burned, before passing through four more turbine stages. This process, while odd, makes sense from an engineering standpoint. Turbine efficiency is proportional to turbine inlet temperature. If you don't want to increase the firing temperature to the point where turbine blades melt, you can add the fuel in stages.
Pictured below is a cutaway of one of the Alstom GT24B Gas Turbines. The right hand arrow points to the three rows of inlet guide vanes that are used to restrict airflow through the machine at lower loads. Air enters from the right side in this image. The other arrows point to primary and secondary fuel nozzles and the primary and secondary turbine sections.
There was another interesting aspect to these turbines, and that was heat of compression. Because the air was compressed to such high pressure, the temperature also increased dramatically. This air was needed to cool sections of the turbine, so before it could be used for that, the air had to be cooled down so that it could be used for internal cooling.
The air was taken out of the compressor, used to boil water in Once-Through Coolers (OTCs), then returned to the turbine for cooling and combustion air. There was a low pressure OTC at the 16th stage of the compressor section, and a high pressure OTC at the compressor discharge, after stage 22 of compression. The steam from the OTCs was blended with steam from the boiler to improve cycle efficiency.
The compressor discharge pressure was so high that each unit required its own gas compressor to ensure natural gas fuel had enough pressure to overcome the 700 psig compressor discharge pressure. For these turbines, pipeline pressure - which is quite high - wasn't always high enough.
The boilers on these units were also interesting. There was a standard low pressure economizer, evaporator, steam drum and superheater. This provided low pressure steam to the low pressure turbine, and hot water for the High Pressure Feedwater pump. Standard stuff. However, the high pressure section was a different critter.
The high pressure section of the boiler was a once-through design, with no steam drum. Water entered one end of the high pressure section, and superheated steam left the other end. No economizer, no evaporator, no drum, and no superheater - just a bundle of tubes that boiled 100% of the water, and turned it into superheated steam in a single pass.
To run a once-through boiler, super-pure water is a requirement, because 100% of the impurites will deposit inside the tubes, and eventually ruin the boiler. There is no process for blowing down a fraction of the water like you have on a drum boiler. Also the chemistry control on this boiler was all-volatile, so the pH control chemical also vaporized instead of being left behind to form scale in the dried out tubes.
Normally in a gas turbine power plant, the gas turbine is attached to a generator, and the steam turbine is attached to a different generator. This one was different.
The power train was arranged in a single-shaft design. The gas turbine spun the generator from one end, and the steam turbines spun the generator from the other end. The power train was laid out in a line, with all the machines coupled together.
When started, the generator (used as a motor) would crank the gas turbine up to firing speed, then the gas turbine would ignite. Eventually the gas turbine would get up to full speed, at which time the generator would stop being used as a motor. Then the gas turbine would be spinning the generator, and the generator breaker would close to make power. The low pressure turbine would be freewheeling this entire time, since it was connected to the other end of the generator, but there would not yet be any steam for it. As the boiler heated up and steam became available, the HP and LP steam turbine torgque would be added from the other end of the generator. It was unusual, but inventive and cool.
The high pressure turbine was also an odd beast. It was a stacked "barrel turbine" of 10 stages that produced maybe 10 Megawatts. More importantly, it reduced the high pressure steam pressure to a reasonable value, so that the more efficient LP/reheat turbines could extract the remaining power from the steam. The HP turbine ran at about 9500 RPM, ran through a gearbox down to 3600 RPM, and engaged via a SSS clutch to the LP/reheat turbine.
So the plant looked like this from the stack backwards: Boiler, Gas Turbine, Generator, LP/reheat steam turbine, SSS clutch, gearbox, HP steam turbine - all in a single line. One of the (theoretical ) selling points of this arrangement: It started itself up from cold without operator action other than pushing the "Go" button with a mouse. It could go from cold iron to full load in 90 minutes - an incredibly short time for a steam turbine warm-up.
And now, a few pictures. Sorry, they are low-res. That was the state of the technology back then...
Below: Preparing for installation of the Gas Turbine for Unit 1.
Below: The Gas Turbine inlet, first stage variable inlet vanes (stationary blades)
Below: Inside the turbine compartment. Unlike a GE engine, it is roomy, well-lit and comfortable while the engine is operating.
Below: The high pressure turbine. Inlet valves are up top, and the SSS clutch is to the left.
Below: Arrival of the Unit 1 Generator on site. These things are heavy. It damaged a bridge while going over the California Aqueduct.
Below: The LP/reheat turbine lower casing. Reheat section is to the right, Low Pressure section is to the left.
Below: LP/Reheat rotor about to be set in place.
Below: About to slide the generator sideways into place. LP/Reheat turbine casing is in the background.
Below: View of one of the units from above. The boxy brown thing is the air intake. The three pipes side by side are the generator iso-phase bus ducts, with the white generator breaker in the middle of them. The silvery lines are steam pipes.
Below: Setting the upper part of the stack for Unit 1 in place.
Below: Building a cooling tower
Below: GSU (main) transformer. 21KV to 230KV
Below: Gas compressor huts, with gas coolers at the left up on stands.
Below: Getting close.
Below: First fire, Unit 1 Turbine. They all smoked a lot at first, until the contaminants and protective coatings burned off.
La Paloma was my first experience with gas turbines, with exotic steam turbines, and with having to deal with surface water, and a ZLDS system.
Surface water contains a great deal of suspended solids - dirt and biologics - that must be removed before the water can be used in the cooling towers and in the water purification systems. This is done by clarifying and filtering the raw water that is taken from a surface source.
Below: The clarifier. This is the first step in getting muddy aqueduct water cleaned up. Chemicals are added to help solids clump and fall to the bottom. Clarification removes most of the suspended particles and algae. Junk that falls to the bottom becomes a sludge, which is pumped out and run through a filter press. Water that overflows the top and down the pipe to the right is much cleaner, but not yet clean enough.
Below: Water exiting the clarifier goes through a ten-cell multimedia filter to remove the remaining suspended solids. The beige trailers in the background are part of the water demineralization system.
Then there is water disposal. "ZLDS" stands for Zero Liquid Discharge System. Power plants that use cooling towers have to dispose of part of the water at all times, because they cool through evaporation. When water evaporates, it leaves behind dissolved solids that will concentrate and deposit on the evaporative media. This scale will foul the surfaces and make the cooling tower unable to remove heat from the cooling water.
An evaporative cooling tower requires continuous blowdown of wastewater, and this water
contains elevated levels of dissolved salts - mainly calcium, sodium, and
magnesium - stuff that will scale up the media in the cooling tower if allowed to concentrate
further.
If your power plant is not allowed to discharge waste water to a deep injection well, you build a ZLDS system to concentrate the cooling tower blowdown waste water. This process recycles as much water as possible back into the system, and you end up with bins full of salt. This is all that remains of those thousands of gallons of water that the cooling towers evaporated.
Below: Brine concentrators, for dealing with the cooling tower waste water blowdown. These were part of a very complex system designed to salvage water from the waste water stream, and remove the salts. The heat source for these was a pair of turbo steam vapor compressors that ran at very high RPM, and used about 5 Megawatts of power each. The concentrators we eventually nicknamed "the ICBMs".
Below: Inside a Brine concentrator, before it went into service.
Below: A view from the desert across the street.
Aerial shot. Gas compressor huts and Unit 1 are closest, and the ICBMs are up near the top.
Unfortunately, this job working with incredibly cool equipment ended up being a different hostile work environment, working for a different asshole. Funny note: One morning the boss announced that he had experienced chest pains over the weekend and had been taken by his wife to the Bakersfield Heart Hospital. One of the operators muttered, "I thought you had to have a heart to go to that hospital."
If you think of the father on the "Orange County Choppers" TV show, this is what the working environment was like. I'm a professional, and I treat others professionally, and expect the same treatment in return. Unfortunately, some people use the workplace as a venue to vent their rage.
Other than the toxic atmosphere, which eventually became institutionalized, the place was a marvel of ingenuity and automation - and I learned a lot while I was there. So eventually I moved on to another power plant just down the road from this one. At least we didn't have to sell our house and move for me to take the next job - which turned out to be awesome!
The next career autobiography post is here:
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