31 replies to this topic

[laharum-australia]

Hi Everyone
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
https://docs.google....uthkey=CI_Bx8MF

[laharum-australia]

The link above seems not to work now, so I have placed the reviews of gasifier design on my website www.billswestvicag.com if you are trying to access them

[meschke]

Hello,  
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.

meschke

[laharum-australia]

Hi
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.
Billhttps://docs.google.com/leaf?id=0B9Z3pi0ZMJ9iNDllZDJhZTUtZWM1Zi00M2JlLWEwN2UtMTU2MjRmNTRjMTBl&hl=en_GB&authkey=COLpn8wC

[laharum-australia]

We ran the beast on Sunday. Initially there was a lot of condensation, but we think this came from the heat beads used to get it going, as it disappeared after a while. The flame was invisible in daylight, and you have to poke a piece of paper into it to see it was alight.
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
https://docs.google....MzOTE5&hl=en_GB

[meschke]

Hello,
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.  
Thanks

Meschke

[laharum-australia]

We have done several runs now, and stability seems to be the biggest issue. On the plus side, we can make gas from wheat , on the neg side, the temperatures went too high (melted one thermocouple, blew a hole through the SS mesh) and flame quality keeps varying. Tackling in various ways. The grain seems to stick together, fire cuts a pathway through, and you get complete combustion instead of gas production. So we need better agitation. Re the temp thing, the critical issue seems (what what I have read) the velocity of the gas. Grain has lower void space than usual clunky fuels used, so we think the throat has to made much wider. In fact our next run is going to be set up with no throat, and also as an updraft system instead of the downdraft imbert type. If it works, it has several engineering advantages, and issues will move to how much tar production occur. We are also blowing now not sucking...mainly so we don't muck up the fan

[meschke]

Hello,
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!

Anthony

[laharum-australia]

We have run the gasifier several times now trying to get it a bit more
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

[laharum-australia]

Our gas flow rates are a tad high for a venturi system I think...upwards of 15 l/sec I estimate, and thats only with 1.1kPa pressure from the fan. Our aim is to stick this thing onto a 140 HP tractor eventually and do a seasons work

[laharum-australia]

We have made several changes now, automated feed in system, agitator driven from below (windscreen motor from a car, right angle drive from a dead angle grinder.. Most importantly we now sense the current the agitator motor is using and switch on the fuel drive when this value goes below a set point. Works well, fuel is added as multiple short bursts so we no longer get busts of tar etc in the gas. Next we plan to fit a condensor and filter on the gas outlet, and feed it into an old Honda petrol motor. Gas flow is god, in fact there is an audible roar when it is flat out!

Attached Files

•  gasifier 18 sept.jpg   134.96K   3 downloads

[laharum-australia]

It looks as if the whole concept is starting to get a bit more attention...we have been asked to go to this and smoke everyone out! Should be a good day

Attached Files

•  lcare.jpg   109.63K   0 downloads

[HarryN]

Hi, I am thankful to the APL group for the changes to this site so that posting is possible again.

I am following this thread and your web site - very interesting work.

[laharum-australia]

More problems along the way...slips for beginners I guess. The change to the agitator drive system has resulted in voltage and noise somehow earthing out through the thermocouples, and things went wrong when we earthed the whole system out to reduce this problem...burnt out the device sensing the current on the agitator. Now repaired, and altering the thermocouples so they are isolated from the system (now mounted in  piece of heat resistant glass).
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????
https://docs.google....mZDdl&hl=en_GB

[laharum-australia]

Have been musing on the way our current design works. One odd fact is the absence of ash. It seems as if the grain converts into very light "rice bubble" type lumps which get progressively smaller, and end up being blown out with the gas flow. In my mind, I visualise the upper part of the furnace as being a swirling mass of incandescent lumps. I guess we have fluked onto this with the decision to go updraft, and then to feed the fresh fuel into the seat of the furnace. In a way it may be better described as a partly fluidised bed system. It probably means we are going to have to work on insulating the upper part of the chamber so it reaches higher temperatures, and maybe placing some swirl mechanism up there. We are finding we can reduce the depth of fuel in the combustion chamber to about 30-40 cm which will mean the weight and size of this thing can be reduced a lot. Anyway, just some thoughts about what we think is going on, and perhaps reflects the issues with designing a gasifier which runs on a fine grained fuel such as wheat. Comments on this concept are very welcome from you more experienced people.

[laharum-australia]

Well, the day went successfully, nice clear gas flare, and great relief when the motor ran OK at considerable revs (spontaneous applause from the 40 or so farmers present....likened to early attempts at powered flight by one wag). So it seems the concept is now proven...it is possible to use wheat as a fuel, and produce gas which will run an engine. Funds are pretty well depleted, so we will refine the present arrangement (still having problems with electronics, fuel leakage around the shaft of the agitator etc). If we had our druthers, I think we would rebuild from scratch with some major design changes. A few thoughts so far...a square furnace, with a hinged side door to allow access to the grate for cleaning, lots of insulation particularly at the top of the furnace, dual jacket only at the bottom half (but not over the access door), possibly some kind of internal cyclone in the top of the furnace. Time will tell, the concept is proven, the economics look right, just keep beavering along

[meschke]

congratulations.  I am very excited for you guys.  Thank you for keeping us updated.  I'm sorry I don't have anything to add to your efforts except praise.

meschke

[HarryN]

I wonder if you can reduce the tars a bit more in the gasifier somehow.  Just kicking around ideas - perhaps load it up with charcoal first and light that up.  When it is quite hot, it might act as a better reduction zone to crack the tars.

Also, consider heat drying the fuel to about 100 - 150 C before using it in the gasifier.

Very interesting project - please continue on.

Harry

[laharum-australia]

First, if the unit is shutdown, you end up with a charcoal mass with which to start it next time, ie don't add new fuel fuel for a short time before shutting it down, all the grain is converted to charcoal ready to go next time. As far as cracking the tars goes, I think we need to insulate the top of the unit so that it gets hotter in that part...it gives us some hassles with the temp of the gas exitting the unit, but should be feasible. Again, using the exit gas to heat the incoming fuel seems logical. It is getting to a stage where we may be better to rebuild from scratch now we know a bit more about what we need, but funds are limiting that option and we most likely will use the current unit to promote the cause until resources become available. We wrote up a summary of the day which we hope will be published in the Landcare magazine...distributed right across the state, and I have put it at this link if you are interested
https://docs.google....Q2NThl&hl=en_GB

[HarryN]

Hi, I was not able to read your paper - it seemed to require a sign in of some kind.  In any event, I really like the work you are doing on this.  I have some ideas that might help with the tar formation, but they are sort of a guess of course.

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.

Harry