I almost always blog about Vermont Yankee, but today I am taking a break from nuclear and its issues. Today is about coal.
This afternoon was the culmination of the coal course I gave. We finished the class work last week, and today we visited Public Service of New Hampshire Merrimack Station, near Bow, New Hampshire. It was a beautiful winter day, and the PSNH people were great. The huge scrubber construction project means parking space at the plant is at a premium, so we left our cars at the Park and Ride and PSNH picked us up in two vans.
PSNH was very well set up for the tour. Within the plant, we wore ear protection. Next to points of interest, PSNH had a diagram set up on an easel. The guide would point to parts of the diagram and then to parts of the plant. It was very easy to understand what we were seeing. I have taken tours of nuclear plants, and never seen anything so thoughtful, cheap and effective. The plant was gritty compared to a nuclear plant, but not nearly as dirty as I expected it to be. The plant was surprisingly clean, actually.
The plant has two cyclone fired boilers. I didn't know that these types of boilers are designed to make very little fly ash, and lots of molten slag. The plant doesn't need ash ponds, but instead has relatively small ash hoppers. The slag was beautiful. I loved looking through a port to see streamers of molten slag flow into the quenching water. Strands and streamers of dark glassy material and lighter glassy material, flowed into water, backed by an orange glow.
All the slag is ground coarsely and sold as roofing material. The small amount of ash is sold as an additive for concrete. It's nice to see a coal plant so well run, with all the byproducts made into something useful.
We also looked though welders glasses into a port at the fire box. I didn't enjoy that as much, perhaps because I had seen similar things back-in-the-day when I worked on NOx control at Acurex (now part of A D Little consulting).
We saw the anhydrous ammonia tanks for Selective Catalytic Reduction (SCR) of NOx. Merrimack was one of the first plants to use SCR. We also saw the huge sulfur-and-mercury scrubber under construction. The cost of the scrubber is close to $500 million dollars, and building it has been very controversial. On the other hand, the influential Granite Geek blog just posted that the scrubber looks like a good choice in the current political climate.
One thing I had not realized was that this boiler was designed in the 60s for a certain type of coal. That's the kind of coal it can burn. They can buy this type of coal from three places in Appalachia, or from Venezuela or Europe. They buy from Appalachia and Venezuela. They have to check every train to understand the properties of the coal, and they do a fair amount of coal blending. The idea that we import coal from Venezuela to New Hampshire was strange to me, and PSNH tries to avoid importing coal. But boilers are designed for coal of a certain level of heat content, ash content, sulfur content, water content. They can get this type of coal from only certain places.
I was very impressed with the plant and the courtesy and professionalism of the people who work there. I was also impressed with being able to walk right in to the control room and stand around. They told us: don't push any buttons, they all work! But we were allowed in. Again, different from a nuke plant.
I also will take a small amount of credit for the success of the trip. My course introduced people to basic coal and pollution control technology, so everyone was able to understand what they were seeing. We all had a good time.
I include my course plan here. I leave out the names of my guest speakers, since I haven't asked them if they wanted to be on my blog.
All Around the Coal Boiler
ILEAD Winter, 2010
First Session Thursday January 14
• Thermodynamics of Heat Engines
• Types of Coal
• Ordinary Types of Coal Boilers: Stoker, Tangential, Cyclone
• Fancy combustion: Supercritical, IGCC, Gasification
Second Session Thursday January 21
• Particulate and particulate control methods
• SOx and control methods
• Guest presentation: Advanced control methods: Cleaner Power Without Scrubbing.
• Participant report on particulate control history (2.5 microns)
Third Session, Thursday January 28
• NOx Control methods, past present and future
• Mercury control
• Guest presentation: Representative of Northeast Utilities (NU) on the scrubber at the Merrimack plant
• Participant report on mercury controversies
Fourth Session, Thursday February 4
• Earth and Water: The slurry and ash ponds
• Recycling coal ash and sulfur
• Guest presentation: Coal ash and recycling
• Participant report on ash pond disaster at TVA
Fifth Session, Thursday February 11, field trip to the Merrimack Coal Plant
Participant reports cover historical topics (the history of regulation or an incident or technology). Each report is ten minutes long, with five minutes for questions. Participants do not need a technical background in order to prepare a report.
Second session, January 21:
• History of particulate control controversies (2.5 microns)
Third session: January 28:
• History of mercury emission controversies
• The ash pond disaster at TVA and its implications
We will discuss other possible reports during the first class session.