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?