attempting to use grain for gasification
Posted 01 June 2011 - 10:55 AM
Our local Landcare group is interested in exploring possibilities for renewable fuels here, and concluded using grain through a gasifier to replace diesel in tractors was a possibility. At first we thought we would order a GEK and play with that, but realised we needed to design a gasifier specifically for the fuel type. So back to basics using Swedish data (http://www.fao.org/d...00.htm#Contents
and we have come up with a trial design. In the next few months we will build this, instrument it and see if grain can be used in this way.
The design is below, and thoughts and ideas are welcome...this is a real step in the dark for us
Posted 21 June 2011 - 08:56 PM
I am very interested in what you find. I was thinking about using corn cobs since they are a little larger and easier to work with than small grains in a gasifier. I hope you luck but I know some people are going to say that you shouldn't use food for energy but if it is cost effective when grain is 3-4 dollars a bushel then i say have at it. Good luck to ya.
Posted 27 June 2011 - 04:10 AM
Well, the beast has been built...see photo...and next week we should know if grain can be used in one of these things, or perhaps get an idea of how to modify it to make it work. I see no moral issue in farmers ising grain to drive their tractors to grow more food. As a farmer, I know I have all the gear to handle grain...augers, bins, etc...and one thing for sure, there is plenty of fuel about when you are harvesting. Wood chips are hard to move in bulk, are difficult to prepare, and you need a whole set of other equipment.
I'll keep you posted about what happens.
Posted 04 July 2011 - 05:43 AM
After about 3 hours the machine started to play up, and eventually stopped producing gas. I suspect the ash buildup on the grate (note the way the ash zone temp began to fall, and we couldn't get it up...that is where the reduction reactions occur, so I guess it filled with ash and those reactions eventually stopped. Air flow in varied from about 2 l/sec to 4, sometimes even 6, although when the high flow rates happened the gas stopped...I suspect the fire "tunnelled through the ash chamber"...if you moved the agitator, the flow dropped back to 3-4 usually.
We are going to excavate it next sunday once it has cooled and see what is going on with the ash business. I have ordered a bigger opening SS mesh (2.5 mm) which I hope will fix the problem.
Interesting the temps that it got to (>1200 deg C) and even more interersting that the thermocouples withstood this.
We are also going to try out a bigger throat to try and increase the gas flow rates.
Note the suction pressure measurements is wrong..either my setup or a fault in the algorithm.
We refuelled at about 120 min, and i all I estimate 50 kg wheat was burnt.
The plus is that we have shown wheat can be gasified OK, the negative is that we need to tweak the design to make it stable
Posted 26 July 2011 - 07:27 PM
Very interesting. Thank you for posting and keeping us updated. Will you be trying other grains or just wheat? Maybe a mixture of different grains would work well. What other grains do you have in the area?
I am very intrigued in your progress. Do you have any information on the gasifier dimensions you are using? Such as an Imbert or something else.
Posted 28 July 2011 - 12:04 AM
Posted 29 July 2011 - 01:00 PM
First of all good luck and good job!!
I have heard that the characteristics of the gasifier change depending on when you are sucking or blowing the gasifier. If you don't want to gunk up your fan but want to stay sucking on the gasifier you could go to an ejector set up. There is a nice venturi ejector that uses compressed air here on the gek website. might be something to use.
do you plan to use the gasifier for engine use or heating?
if for engine use I would try to stick with sucking on the gasifier to mimick the engine pull.
Good job though and I am awaiting more updates!
Posted 01 August 2011 - 03:50 AM
stable. We found that there were too many problems operating as a
downdraft gasifier with a throat, such as melting of equipment,
coking, bridging, low gas flow rates, so made a major change and set
it up as an updraft gasifier with no throat. Operates beautifully
(once it has heated up), very stable operation, good gas quality and
flow using wheat. In hindsight it makes sense...downdraft gasifiers
are designed to operate on chunky fuels, usually 2 cm diam and up.
Wheat is much higher density and the void space is less. Flow rates in
the voids must be higher leading to the problems above. Plus the idea
of trying to maintain a fire at and above the throat, with just
glowing charcoal below is inherently unstable. Plus, as the wheat
shrinks in size, it eventually gets blown through the mesh grate so
the ash is really unburnt charcoal. In the updraft system, the fire
naturally sits on the grate, and if anything I suspect the ash is
being blown out with the gas to large extent. Our next task will be to
design a constant feed system, mechanical agitation (possibly not
required) and work on the options of introducing some steam at the
grate, and maybe feeding exhaust gases from an engine back into the
furnace about halfway up. The other challenge is to work out how to
introduce the wheat at the grate, because that's where you want the
new fuel to appear, not at the other end of the furnace. I will put
some pics up on the website www.billswestvicag.com over the next
couple of days
Posted 18 September 2011 - 08:08 AM
Posted 01 October 2011 - 05:28 AM
Our first attempt at running a motor was neither a failure or a success. The motor (10 HP Honda petrol) ran briefly, but the plug oiled up. The gas is still too dirty after a water trap (copper piping and jam jar in a bin full of water), an oil bath air cleaner (ex landrover), so have now added an in line oil filter (why?...its what was on hand) which has been washed and dried. In future we will also warm the Honda motor up by running on petrol before switching to gas. Unfortunately, the next attempt will be in front of an audience (see above) so here's hoping.
Finding now that we are starting with partially burnt grain (ie what remains when we shut it down) that the beast gets going very quickly....about 15 minutes from cold, which isn't bad considering it weighs in excess of 60 kg of steel now.
I have prepared a handout for the do next Tuesday, if you want to have a look the link is below. One interesting news item is that we can only afford to burn about 40% of the known reserves of fossil fuel if dangerous climate change is to be avoided...so why are companies still looking for more????
Posted 03 October 2011 - 12:59 AM
Posted 05 October 2011 - 12:18 AM
Posted 20 October 2011 - 07:16 AM
Also, consider heat drying the fuel to about 100 - 150 C before using it in the gasifier.
Very interesting project - please continue on.
Posted 23 October 2011 - 10:45 PM
Posted 24 October 2011 - 01:30 PM
In a setup like you have, the reduction zone will be doing several jobs:
- Cracking tars
- Reducing CO2 to CO
- Some H2O to H2 conversion
These are all fairly slow reactions and work best in the presence of a hot carbon source. (1000 C) There is a good chance that there is a shortage of sufficient hot carbon and time for this step of the process, as that is common in most biomass. One way to test this is to force it into hot carbon overload and see if the problem goes away.
The easiest way to do this test is to get a lot of hot charcoal briquets to help supply this carbon. Load up the reactor with a starting layer of this and light it up. Keep adding charcoal until you have about 1/2 meter of hot burning charcoal in the reactor.
At this point, start adding in the grain mixed with 20% charcoal briquets, and keep feeding in that mixture as you do the run. The charcoal reduction process and tar cracking are endothermic (absorb heat) so over time, the charcoal bed will start cooling down a little. If you can use the heat of the gas coming out to pre-heat the air coming in, that helps, but is not mandatory for this test.
Slow down your air flow into the reactor to about 1/4 of what you are used to. This will give more time for the cracking and reduction processes to occur.
If this combination helps with tar reduction then you are on the right track. I am not sure if you will be able to maintain this hot carbon zone for a long time without some more heat coming in though, but it should work for a test and does not require changing the equipment.
Good luck and thanks for the effort.
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