Newbie First Run Questions
Posted 23 October 2011 - 12:56 AM
My GEK took its' maiden run this afternoon(!), and I'm hoping for a little advice from some experienced operators. On the bright side, I was able to produce gas on the first run and maintain a flame in the swirl burner for quite awhile. However, I observed that I was running quite hot on both thermocoulpes at 5" of vac. The upper temp was arounfd 1300F and the lower about 1500F, so I dropped the vac way down to about 0.5" to try to lower the temperature. I was only able to get down to about 1100F at between 0.5" and 1" of vac, so I shut the system down. On the way down to 1100 degree's, the flame lost it's ability to maintain itself. I went back up on vac before shutting down for a little bit to see if I could reestablish a self-sustaining flame, but I could not. The gas that was coming out at this time was flammable, but it would not sustain itself after I took the pilot light away.
So, I guess my question is this: why am I runnning such high temps at such low vac levels? I'm thinking I must have a leak somewhere in the combustion zone, but I'm not sure how to troubleshoot it.
Any thoughts would be really appeciated.
Posted 23 October 2011 - 02:44 PM
Experiment number two to follow today
Posted 21 November 2011 - 01:34 AM
A local sawmill grinds their waste into landscaping chips. I've been using that for feed stock. As far as i can tell, it works well. But then again, I'm new to this so I'm not sure what poor running feed stock looks/acts like.
I've put several more runs on the system since my last post. Most of the runs resulted in early shutdowns so that I could fix problems like air leaks that became apparent. However, yesterday I got a 2 1/2 hour continous run on the system. This was by far the longest run. I'm not sure where I am on the learning curve with this, but I have some questions after yesterday.
1) How long should it normally take to get the core temperature to stabilize around 800 degrees? It took my system about 45 minutes.
2) Is it normal to have a temperature variation between the two measurement points? I typically have a 50 to 100 degree difference between the two, and they alternate back and forth as to which one is the hot one.
3) What is considered 'normal' variation at each measurement point over time if your pull rate is held constant?
4) After a 2 1/2 hour run, the mason jar was about 1/4 full of dry soot. Is that normal?
I do have pics and vidoes from the very first run and also from yesterday. I will post them on the wiki as soon as I figure out how to log into it and post there.
Posted 01 December 2011 - 03:43 AM
From your brief description of the feed stock, it sounds perfect for our gasifier. Chip like chunks are the best (in a most ideal case, perfect cubes an inch on a side are the 'ideal fuel' however most are less than the ideal case but work just as fine. Do you have a picture of your feed stock? How big are they? Do you know how much moisture is in your feed stock?
To answer your questions above:
1. We suggest 750-900C for the top of the reduction temperature and anywhere from 700-850C for the bottom of the reduction bell. While the higher in the range of both temperatures are more ideal, you can get away with running the reactor in the lower of the ranges. But you definitely do not want to run an engine with reactor temperatures in the 600s. It should get up within proper temperature ranges in about 20 minutes or so. This will be the time that it takes to heat the entire system to its heating capacity before the thermal capacity is at a steady state.
2. Like I mentioned above there will be a temperature difference between the top of the reduction temperature (tred) and the bottom of the reduction temperature (bred). Tred will read combustion temperatures and Bred will read reduction temperatures. Sometimes these two temperatures will invert and you will see the bred reading is higher than the tred. This is the fluctuations that the thermocouple 'sees' in the reaction of a solid feed stock. The flickering of the flame if you will. However, if the bottom of reduction starts reading way higher outside of its temperature range ie: 900C, this is indicative of bridging or packing of the feed stock across the bell. When there is no charcoal in the reduction bell, the endothermic reactions cease and the hot combustion gasses increase the thermocouple reading that you see here. You will need to turn off the flow rates of the GEK, then open the door at the bottom of the reactor and with a curved stick, poke the bell. You will see char fall into place in the bottom of the reduction cone. You may also access the top of the reduction bell by poking a stick through the reactor lid cover (while the GEK is running with low flow).
3. See above.
4. The jar is a catch for soot and even condensate as well. This is normal. You will want to empty this out after your runs if there is more than a third in the jar.
It would be great to see pictures and video from your run. It seems like you are getting more familiar with it, looks like you might be graduating from being a newbie soon.
Posted 17 April 2012 - 05:39 PM
We had the same issue after we ran our gasifier a couple of times. The Tbred was tend to be higher than Ttred and both readings were above 1000C. Last time when we ran it, we found the Tbred was much higher than Ttred, which is definitely not normal.
We had a discussion about this issue, and suspected if there would be some leakings around the combustion zone, or probably because we ran out off woodchips (we didn't use the 10gal hopper, instead, we just fed the drying bucket and sealed it with a steel lid), also, our another suspicion was if we drag too much charcoal out at the bottom of reduction bell (before the last time running, we opened the ash out port since there's no ash in the ash container).
We are going to check if there are leakings this week, I will appreciate if someone can provide some suggestions or comments about our above suspicions.
BTW, we kept the readings of pressure on GCU display at the range of -30 ~ -60, I wonder if that reading equals 3" ~6" water in manometer?
Thank you all, let's enjoy our gasifiering
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