Hi Brian, I can see this thread has taken off in many directions, so hope you do not become confused by my replies.
My Q. >> 1. Is it first cooled Your A,. > Yes. Our producer gas goes through a water cooled heat exchanger. The temperature of the product gas by the time it gets to the flare pipe is close to if not at ambient. Our immediate post-heat exchanger TC indicates that the gas right out of the heat exchanger is a bit below ambient but, to error on the side of caution, I'll state with some assurance that by the time it hits the flare outlet, it is most certainly below 100F (38C). Reply. Even at 38C, your gas will carry both moisture by way of humidity, and sub-micron carbon blacks, which will give you the white core in the centre, and the red tinges around the outside of the flame. My Q. >> and cleaned of dust and moisture? Your A. > Mmmm, sort of. Straight out of the gasifier shell, the product gas goes through a GEK cyclone. Then it goes through the above described heat exchanger. So the cyclone clears out whatever it does. Then the hard temperature drop in the heat exchanger, we assume, crashes out a lot of moisture which we assume collects in the heat exchanger's sump. Reply. The cyclone at best, will pull out dust to a particle size of 10 micron, that's like talcum powder. You next clue is in the condensate water, which will be either clear, or shades of yellow right through to black with floating tar. If yellow, this will indicate the presence of pyrolisis distillates (read that as tar), and will show up in the flare contributing to the yellow colour. Black smelly condensate, will show up in the flare as the stinging radiation that you can test with your hand. It will be best to get rid of your assumptions, and start recording details from the clean outs, because they provide a large amount of information. By comparing these cleanouts after each test, you can then evaluate any change you make to the gasifying parameters. Right now, the next key point is the flare outlet. However, we intend to have a 40 micron filter between the heat exchanger and the flare. We HAD one in there but our first couple of efforts were, shall we say, "suboptimal". (We could also say, "downright ugly".) The "tar" we made looked and stuck like asphalt, I'm pretty sure we could have resurfaced some streets with the gunk we made! Given that, the 40 micron filter element was destroyed. The filter housing is still in-line and we have a replacement element in hand, but we're a bit leery of our own incompetence and have not yet been bold enough to install the new element. Reply. I can understand your need for a course 40 micron filter, but you may as well just leave it out for flare tests, as the gas would be far to dirty in both dust and tar for an engine. Particulate going into an engine should be less than 2 micron to prevent abrasive wear. My Q. >> 2. If not,what temperature is the gas at the exit point of the gasifier? Your Q.> Do you mean the flare pipe? Or do you mean the air input manifold inside the gasifier? Reply. Neither. I am referring to the outlet connection for the gas to the cyclone. If you are not quenching the gas to below 500C quickly, then you will make sub-micron soot that will pass straight through the cyclone, and be carried by the gas humidity to your flare. If you mean the flare, I don't really understand the question, but I'll guess the answer is "no". If you mean the air input manifold in the gasifier, then the answer is, "control, sort-of, monitor, yes". Our initial design included both "push" of input air and "pull" of producer gas. We're using an air compressor to push the air into the gasifier. We were also using a blower to pull the product gas just before the flare. For several reasons, we concluded the pull wasn't needed and we've deleted the blower so now we only push the air into the gasifier. I'm not entirely happy with our fine control of that flow. We have coarse control, but not fine. I'm intending to shop for an additional regulator to give us fine control this upcoming week. We do have a standard mechanical (Dwyer) float flow meter at the air inlet of the gasifier so we can manually read/record our air input volume/time. Reply. While the gasification principles you employ may be creating a tar gas, that needs to be established from the down stream information before you start making any sort of changes to those parameters. I will say though, that you can affect the gas quality changing from suction to blown. My Q. >> 4. What temperature is the flare exhibiting from the probe I saw you using in the flare? Your A. > Humph. I don't like that TC. Seems pretty much pointless to me. The slightest puff of breeze and the flame is anywhere BUT on that TC. Even when the air is still, the flare dances around so much that I don't believe the accuracy of the readings we get from that TC. But the numbers from the time of the afternoon video were anywhere from 260 - 650C (500 - 1200F) and at the time of the night video were 480 - 650C (900 - 1200F). But I have close to zero confidence in the quality of that data. Reply. The flare TC while not accurate, is close enough to indicate the presence of tar. A reasonably clean gas free of tar should not be hotter than 1,050C and over that your gas is in tiger country! I think the way your flare is designed is adding to the problem, as the white core at high velocity can also indicate unmixed gas, which will revert into soot in the flare itself. This will of course give you the red tinge. You do need a controlled pressure air supply into your flare mixing chamber to match the pressured gas coming out, as just aspirated air will be inadequate. ------------- While I have limited comment to answering your questions regarding the flare within the experience we have accumulated, it would seem your gasification parameters may not be providing you with complete tar cracking. Don't panic, but start by assessing the condensate quality, then change and test only one thing at a time. Hope this may be of assistance. Doug Williams, Fluidyne. _______________________________________________ Gasification mailing list [email protected] http://listserv.repp.org/mailman/listinfo/gasification_listserv.repp.org http://gasifiers.bioenergylists.org http://info.bioenergylists.org
