Saturday, October 8, 2011

Plumbing the gasifier - Part 2

It's been a while since I posted. I haven't had as much time to put in as usual; but I still manage.

I have run 3" PVC pipe from the condensate tank forward to the vicinity of the hay filter; this part isn't finished yet.  I went ahead and started work under the hood, and I am facing several challenges. I would like to run as much 3" pipe as possible throughout the system, to avoid restrictions which will reduce performance later. Unfortunately, 3" PVC is big, and fittings are expensive and clunky. So I had to transition to 2" for the last bit.

I wanted to get a check valve for the front blower, to keep air from backing into the woodgas line and causing problems. I found a 2" check valve at Lowes; but the internal spring was too much for my bilge blower. I decided to make my own:

I got the idea from a friend who made the same thing, and this is the critical part: you need a disc of flat PVC, but where do you get one? You have to make one. Turn your oven to 250 degrees, and cut the PVC pipe to a sufficient length. Slit one side. Place it on the rack (the tinfoil was unneeded) and close the door.

Keep an eyey on things, when it begins to droop, wait another minute and pull it out. For me this happened just as the oven got to temperature. I tried stretching it against the rack; this wasn't necessary, but you can see how flexible it is:

Immediately flatten it with a board; it will take whatever shape you press right then (I later made one to fit the side of a paint can). Let cool and it hardens up again. Voila! Flat PVC. No nasty smells, either.

It was a good idea - unfortunately, I found that even without a flapper in place, the PVC screen was too restrictive for my wimpy blower, and cut the airflow drastically. So I just am using a pipe cap for now, in lieu of a proper check valve.

I have to have a final filter for the gas, before it goes into the engine. This can be paper, or better - foam. I took a sheet and blew through it - it works fine. So how to get that surface area into a compact space? This is what I came up with:

A pipe in the middle of this paint can is drilled full of holes, and wrapped with foam. The gas flows into the pipe, through the foam and into the can (and on to the engine). Here's the pipe - note the flat PVC top:

And the foam:

Sealed with duct tape (low temperatures here):

Now I need the outlet pipe. I made another "oven piece" and wrapped it around the can. Then I cut a piece of pipe to fit the profile. This is tricky! I was going for a tangential entry, to help swirl the gas flow and spread out the suction. Here it is glued up:

It fits so:

That's all for today. Like I have said, it's a bunch little things that aren't very impressive, but put together it's a lot of learning for me. Baby steps...I really want to get this done, so please be patient - it will happen!