Smoke clean up

[chrisfallis]

Has anyone tried a low-tech way to reduce visible smoke stack emmissions? I googled electrostatic precipitators and they seem to work in the powerplant kind of environment where combustion is constant and monitored continuously. We would not have the same thing in a residential type of wood burner. And who wants to spent $40,000 of capital? What if you attached twenty or thirty feet of nearly horizontal pipe to the back of a boiler in leiu of a traditional chimney. My thought is that the pipe would eventually be cool enough to precipitate water vapor and unburned combustion products. It would be one big creosote catcher. If it was made of 8 inch plastic pipe in easy to handle 10 foot long sections, it would be easy to pull them apart and clean them weekly. A drain at the low end would allow the condensed water, and whatever witch's brew from the stove, to be diverted to a sanitary sewer. I would think that the effulent would probably eat metal pipe for lunch, but plastic may have a longer service life.

 

[Eric Johnson]

I tried an 8-inch add-on cat combustor on my old Royall 6150 conventional wood-fired boiler, and it didn't have the desired effect. Don't know why. I certainly had high enough stack temps.

Gasification is the obvious solution. I don't know if you consider that low-tech or not. I think the engineering and mfg. tolerances are pretty high-end, but the product itself is decidedly pedestrian (carbon steel boiler plate and refractory cement).

You might be able to retrofit an OWB or other conventional woodburner with refractory bricks and get it to burn clean on occasion, but I doubt that you'd see anything close to consistent results, mainly because wood is a pretty inconsistent fuel.

Your horizontal pipe idea, in addition to manufacturing creosote, would probably kill the draft, I'm guessing.

 

[chrisfallis]

I am thinking of this as an add-on to an already fairly cleanly gasifier. What got me started was seeing pictures of a Garn's chimney-less installations. There is a pipe straight out the back of the boiler and it vents about 3 feet above the ground level. I have always seen a big metal drum placed under the end of the outlet pipe. I'm speculating that in low boiler temperature conditions, water vapor condenses inside the boiler itself (not a good long term operating condition) and that the water drips out of the pipe and into the barrell. I think I read on this forum a thread that described a fairly steady stream of condensate from a cold-started Garn. if you extend that pipe further along, you are guaranteed to drop the flue temperature down to ambient and all kinds of nastiness will condense.

I live in suburbia and am trying to be a good neighbor. The less visible smoke and smell, the better. My neighbor’s condensing natural gas boiler pours steam out of a basement window exhaust port and it sometimes drifts into my yard. I comfort myself by saying that it is “just water”. Maybe I am getting to the point of diminishing returns for my effort.
%-P

 

[TCaldwell]

chris the 55 gallon drum at th end of the horizontal flue is there to contain the fly ash and large particulates, even with a 4.5' turbulator in the last pass , discharging flue gas temps at 300 deg the condensate plume is not much, as eric stated the long horizontal flue might accomplish the issue but would create too much water colunm differential, backpressure for the garn to operate.

 

[Eric Johnson]

I've forgotten, Chris, what are you running?

 

[chrisfallis]

In 1997-2001 I had a Tarm in the basement of my house. It had a 30 ft+ inside stack but I still attracted the attention of my neighbors while the boiler was idling or on start-up. The fire department actually showed up one day and wanted to use their axes on the basement door to see why my chimney was belching smoke. The boiler was idling on a spring day and was pyrolizing the wood. The gases went around the gasifier tunnel bypass valve and up the chimney. This was a fairly constant occurrence and I will attribute it to a lack of storage for the heat from the boiler and, of course, operator error.

I have my eyes on a Garn for installation next fall and I want it to be as clean as I can possibly make it.

 

[Eric Johnson]

A Garn burns pretty clean. As in zero smoke, from what I understand. In any event and as a practical matter, a lot less smoke than a modern EPA-compliant wood stove, I'd wager, regardless of what the stove sales literature says.

I've also noticed that the smoke from my EKO, on the rare occasions when it does produce a wisp of smoke during gasification, smells more like toasted wood than wood gas. It's kind of a mild, cooked wood smell. I'd bet the Garn is even better.