Thursday, March 19, 2015

Cofiring biomass

One of my work projects is testing cofiring of small amounts of wood chips with coal in coal-fired power plants. The idea is that it's a way to reduce pollutants discharged to the atmosphere without requiring significant overhaul of an existing coal-fired power plant. Additional benefits include creating a market for Alaskan scrap wood that would otherwise be disposed of, and reducing carbon footprint.

Since this has been a rather publicized project, I'm taking the unusual step of revealing real names here.

I am working with a forester colleague, Dave Nicholls, who lives in Sitka. He, of course, is interested in finding markets for Alaskan wood products. We also have on board my very first grad student, one Zack Wright. He is a 4th-generation Alaskan and super bright, motivated, practical, and grounded. The three of us have been test firing small amounts of biomass at our local power plant in Fairbanks, where the power plant people have been extremely enthusiastic and accommodating. Not only did they give us access and support to do our testing in their plant, but they made sure to schedule it when their top-notch operations guy was on shift. That guy was amazing--he sat in his control room and stared at SCADA screens, pushing and pulling knobs and levers all through the burning to make sure that power output was constant. 5-15% aspen wood chips were added to a single burner's combustion stream. Among the parameters monitored were efficiency, firing rates, excess oxygen, NOx emissions, CO emissions, and smokestack opacity.

Here are the wood chips for the test burn. This pile here is 40 tons:

A bucket of coal! I am weighing samples to get bulk density. This photo was taken by my colleague Amanda Byrd.

And a bucket of pure biomass:

Here is a mixture of approximately 5% biomass by mass. This photo is another of Amanda's.

We had monitoring equipment on the roof. This photo also by Amanda. This is the power plant manager, Dave Fish, and Chad Schumacher of Superior Pellet Fuels, a local pellet and densified wood product manufacturer. Chad sold us the wood chips for testing at a greatly reduced cost. He has giant piles of scrap wood that he'd love to find a market for! I think Chad is a man a bit ahead of his time, always investing in products that Alaskans don't realize they need yet. I just hope they catch up to him so his business stays viable, as he deserves and we need!

One difficulty with biomass is the higher water content, especially when the wood is freshly cut and not given time to "season". Just to give you perspective, typically recommended drying times for logs to heat homes are 2 years in the Outside world, and at least one summer in Fairbanks (things dry fast here in summer since it is quite dry, and it remains warm at night). These chips could in theory dry very quickly, since they are tiny and allow a lot of air access. However, air doesn't flow very well to the interior of chip piles. Also, anything one does to artificially dry an energy product (such as heating) requires energy input, which of course somewhat negates the energy production of the biomass. It's quite a challenge when energy is so expensive!

So is it just me, or can you visually SEE how wet these chips are?

Coal mined in Interior Alaska is also unusually high in moisture (up to 30%, where in Pennsylvania it would be under 10%), so it does help reduce the contrast and mitigate that particular challenge of cofiring, although of course moisture during a combustion process will always eat up precious energy!

In other news, the girls are really cute when they snuggle on the couch:

And in other other news, I was visiting with our machinist today, and he showed me photos of himself as a young undergraduate art student, making the cross for the parish hall at St. Matthews Church! This must have been the mid 70's. Wow, how beautiful it was then! Those walls and that cross are all painted a drab brown now.

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