Power Plant Basics: The Steam Cycle

This is a better place to start than condensate and feed.

For some reason I don’t understand I get the nerves about posting these, so I’m telling myself that they are all rough drafts and I as I get better at the software and pacing I’ll come back and do a better version.

That being said the learning cycle has to be closed for any significant improvement to be made.  This means a product must be finished, and then examined for what parts of it are good and what parts are weak, and how the strong parts were executed, and how the weak parts can be improved.

*This is why all great architects do their great work so late in life:  The learning cycle is often 10 years from first concept to finished product to incorporate feedback.

One of the things necessary for this to work is time to become less attached to the product.  Another important ingredient is feedback (and the creator being receptive to that feedback while knowing when to ignore it and stick to the vision).

So here it is.

 

My intended audience is junior power plant operators who have been around valves and pumps and equipment before, but lack a big picture of how the parts are supposed to fit together.

 

Promotions and Cellulose Avionics

I’ve long had a conflicted view of leadership.  On the one hand I’m completely confident making decisions. I know I’m as smart as anybody, and I do a better job than most people of listening to the evidence and making unbiased decisions.  On the other hand I don’t like telling people what to do.  I don’t like conflict.  I don’t like being bossy.  I like being liked.  On the gripping hand I don’t really want to do the same job for the next 20 years, and it’s hard to change jobs from where I am without either a pay cut or the word “supervisor” attached to your job description.

So after applying for the Shift supervisor position once and having it disappear and re-appear under someone other than me, I went back to my comfortable job confident that eventually the job would open up again and be mine… I just didn’t expect things to move quite so quickly.

I showed up to work and was told that my supervisor was switching to a different crew, and that I would be moving up from Control Room Operator to shift sup.  My first official act was to counter-mand the night’s shift assignment left by my so recent boss to put our shift’s (albiet very junior) CRO on the board and move the guy on OT to cover me onto the floor.  This projected my confidence in the guy I had trained, and kept a familiar voice on the radio for my crew… And it felt right.

The next set of shifts came and for the most part things ran themselves on momentum.  Most shifts the guys do their rounds and work their list and who’s in charge doesn’t impact them… My second real act as leader was to schedule a paper-airplane contest.  This put my personality on the crew for the first time.  This showed them that we are allowed to have fun… And importantly, this let me throw a paper-airplane of the 17th floor of the boiler which I’d been tempted to do for around 6 years now.

Boiler tuning and Shadman adrift

When I started blogging I actually expected to spend a lot of time talking about how a pulverized coal boiler works.  The rube-golbergian complexity of it.  The overlapping systems.  The thermodynamics that I can wrap my physics background around combined with a enormous science kit that I can push the buttons on…  I love thinking about it.  Also I’ve spent a fair bit of time googling around about boiler tuning and boiler efficiency, and it’s incredibly difficult to find resources that aren’t written in almost indecipherable engineer speak.  I thought maybe I could be that resource for someone else.

Since then I haven’t written anything about it in months.  Part of that is because I’ve felt my input at work doesn’t seem to get much traction, which discourages me from putting as much energy into it as I used to… but most of it is the fact that my audience (a bunch of friends/acquaintnances on Facebook, and 20 random wordpress minions) doesn’t give a crap about running a pulverized coal power plant, and is much more interested in stories about me and my kid, or stuff I thought was funny.

Well last week one of the hits on my blog came from someone who googled “Boiler tuning” and I felt oddly guilty.  I felt I failed this anonymous stranger, and in missed an opportunity to make the world a better place.

So for you dear lost reader who will probably never come to my page again, and for my future wayward brother, who is more interested in tuning controls for drum level than the etymology of the word genitals or the history of yellow lego mini-figs, I post these 2 links which took me quite a while to stumble across and are the single best resource I found.  These articles by Tim Leopold in Power magazine are readable and useful.

http://www.powermag.com/instrumentation_and_controls/Boiler-Tuning-Basics-Part-I_1741.html

http://www.powermag.com/instrumentation_and_controls/Boiler-Tuning-Basics-Part-II_1859.html

Regulations

WARNING: todays entry is pretty technical, and will bore the crap out of most of you.

I believe in manmade global warming.

I think the EPA is an excellent idea.

I work at a coal fired powerplant.

I didn’t really seek it out, I was looking for work with the skill-set of a 1 term navy nuke electrician without going back for any further schooling and this is where I ended up.  I would feel better about working at nuke plant or a hydro plant, but I’m pretty comfortable where I am and not looking to move the family.  So it is what it is.

I do try and run the plant as efficiently as possible.  I’m the kind of guy who turns the light off when he walks out of a room.  I’m also the kind of guy who turns off the extra cooling tower fans when we drop load, or when the outside weather cools off.  The unit runs better at higher load, and when we’re running lower it makes me crazy.  Nothing I can do about it, the off-takers decide how much they want and that’s what we put out, but I still chafe at it.  And I lower the excess O2 bias.  This is subtle because people don’t automatically connect unused oxygen after the combustion process with waste.  It’s not like we’re paying for Oxygen… except we’re using electricity to run the fans that make sure there’s enough oxygen in the boiler.  But who cares about a little electricity?  We’re a power plant after all… Well wake up you shortsighted dummy.  The less electricity we use on sight, the less coal we burn for the same output.  The less lime we use to treat the sulfer in the coal.  The less ammonia we use to treat the NOx in the flue gas.  (The less CO2 we put out which effects the long term outlook of the planet, though there’s no money associated with that.  Fewer microns of mercury and other random heavy metals, which are currently unregulated…)

There’s a reason it’s called parasitic load.

The EPA regulates us on Sulfur Dioxide, Nitrous Oxides, and Carbon Monoxide.  [And opacity (which is a representation of the amount of ash particulate blown into the atmosphere, and the landfill treatment, and the water-quality of what we put back into the mississippi river, but these things aren’t really related to combustion as I’m discussing now]

Sulfur is in the coal.  It combusts into SO2, and we spray a lime slurry into the gas to absorb it and it falls out in the ash.

NOx is a byproduct of the operating temperatures.  Nitrogen makes up almost 80% of the air.  At high temperatures the Nitrogen bonds with the Oxygen (which makes up the bulk of what’s not nitrogen in the air.  We spray ammonia gas into the flue gas upstream of a giant catalytic converter which breaks it back into Nitrogen and water vapor.

NOx and SO2 both cause acid rain which has some negative effects on wild life and a very slow, but unrelenting, eating away of infrastructure (buildings and bridges).

CO is a byproduct of incomplete combustion.  Ideally the carbon of the coal combines with free oxygen to release energy and create the more stable CO2.  If there is insufficient O2 available at the burner then CO forms.

CO is directly poisonous to animal life.  CO also represents energy we didn’t get out of the coal.  Even if there was no EPA and the power industry was run by evil barons who didn’t care about the environment, they would still want to control CO for efficiency reasons.

EPA sets limits on each of these things, which is good.  The limits are not based on instantaneous values, but rather on averages over time.  NOx is controlled based on a 24hr average, while SO2 is controlled on a 3hr rolling average and CO on a 1hr running average.  No one I work with has been able to explain why the times are different for these 3 different things.  I read our air permit.  I did not see it explained there either.  Operationally, longer averages are better because they give you time to recover from an excursion without getting an exceedance.   Environmentally I’m not sure if there is a real difference.

The 1 hr average on CO is too tight.  If a burner gets temporarily starved for air this can cause a 10 minute spike in CO high enough to cause an exceedance.  The answer to this is to increase the amount of air to the boiler, but the fear of the violation has us running at high excess O2 all the time.  This results in inefficiencies and burning more coal.  This is not good for the environment.  Everyone wants to avoid a violation, and this outweighs our concerns about efficiency to the detriment of the environmental big picture.  If we had a longer time period in which to recover from spikes we could run the unit more efficiently, and better trouble-shoot the root cause of the CO spikes.

Who do I pitch this to?  Is it possible to get it changed or is it a pipe-dream?  How long would it take to get the change in effect?

Arguing with experts.

So today I was working as control room operator and Rusty was in the room monitoring the trends of his tuning work with satisfaction.  I mostly agree.  Primary air biases removed.  Tight MW control.  Tight pressure control.  O2 bias down to 0.75 from 0.9 (should be even lower though) with minimal CO spikes at full load.   And he installed a feed forward from coal flow to the attemperation valves for extra credit.

Then he asks me to look at a trend from last night where he has these tight little rhythmic MW swings.  I tell him they’re a side effect of the Feedwater swings (which were outside the scope of his work).  He says “Oh, so FW master is chasing these load swings.”  And I say “that’s what I thought too, but the FW swings start first.”

He takes a long pause to try and figure out how to explain systems to an idiot… and he goes for the Socratic “So how do the swings in FW propogate into the steam flow?”

“I don’t know.”

“Well the physics of it doesn’t make any sense.”

“I agree.  It doesn’t make any sense.  It still happens.  If data and theory disagree I go with the data 9 times out of 10.”

Another long pause.  “Well next time it happens try shifting the mode control from BoilerFollow+MW to BoilerFollow2.  If I’m right, the FW swings will stop.  If they don’t then we’ve ruled out the turbine valves as the root cause.”

This exchange irritated me a lot.  And the part that’s really hurting my brain, is that he has every right to be skeptical of my claim of data that he hasn’t seen (historical trends don’t have the precision to prove the case either way).  He didn’t say anything I wouldn’t when trying to convince someone that they were getting their cause and effect mixed up.  The guy with 34 years of power plant experience doubted my observational skills when I said something that didn’t make any sense.  This should not be a surprise.

It makes me wonder how well I’d get along with me.

Boiler Tuning

So the plant has brought in an expert to tune the boiler, primarily to deal with CO spikes.  He asks Doug if the Control Room Operator who will be on shift has been “Really watching things closely.”  And so Doug asks me to come in on overtime.  At somepoint…

…at some point I need to decide who my audience is at what they need to know.  Is this a story about me talking to a guy and him calling me intelligent/observant/hard working?  Or is this a story about the changes I wanted to make but didn’t have permission to that we paid a competent professional alot of money to do basically the same thing? Or is does this story require a long explanation of the Rube-Goldberg-esque machine that is a pulverized coal boiler.

I don’t know what I’m trying to do here.  I just feel like I should  be writing.

So, highlights:

I come in and say “Doug asked me to help tune this.”  And Miah (on shift supervisor) says “there’s not anyone better for the job”

Rusty (expert) says “I’ve never seen a boiler with logic like this” and I say “The only boiler I’ve ever had experience with is this one spending 2 years sitting in that chair.”  He replies “Looks like you didn’t waste it.”

Rusty makes changes to cap the downside of the PA air kicker.  I made this exact recommendation to Doug about a week ago… of course Rusty came to the conclusion with way less time thinking about it, but I guess that’s what makes him an expert.