9. Februar 2014

Thank you Pascal to give me an opportunity to explain a little further what I experiented with open top systems and what my opinions on them are and how I came to a new open top design and a new gasifieing method. Also to express my gratitude to you as the furst man to realy fully understand the potentials of the new and revolutionary concept in gasifieing. If it was not you who tested this method inyour already fully build cogeneration setup, maybe the "DriZzleR" and the "DriZzleR Method" would had gon unnoticed. Therefor I say "The DriZzleR" is a team. PASCAL and LUK.

What I am writing below in this little article is my own opinion based only on what I learned and observed myselve. I am not a scientist and If I am missing the point or telling nonsense then please join in and correct me.

A litle history is at place. When Dr Reed in the eighty’s invented the stratified downdraft , by that, one could say: he is the father of the FEMA. Was the man who wrote the FEMA manual “LaFontaine”, not a coworker with Reed? Anyway somewhere I read that Reed was very euphoric  about his invention because it beeing an open top system thus it overcame many of the limits of the closed Imbert design. This specialy in the field of stationary systems.

This euphorism did not lasted long. Open top systems got fast a bad reputation. “Do not even bother building one you will produce nothing but tar”, is a commen reaction on forums that people get when they mention their desire to build one.

Despite that reputation and the negative comments, there are always people that keep trying to develop a workable open top, simply because it’s advantages over the Imbert.

Because of these advantages so many FEMA’s have been build (and search the net), even today this design further atracts many builders.  

But as many FEMA builder soon expirienced The FEMA, as practicaly every open top gasifier, has the big problem that it is almost impossible to keep the oxidationzone fixed at a certain level. The oxidation has a tendency to wander upwards to where the oxigen is. With the oxidation kreep-up, the  temperature in the coalbed drops and the gasifier gets too cool, and unable to crack all volatiles and tar. Tar condenses further on the road, with all the known problems with it.

Some attemps have been made to stop this kreeping-up of the oxidation, by trying to fix it around a nozle system.  As is  known from Imbert. Groeneveld did it with his central Nozle and Mukunde with his angled Nozle pointed in the reduction. They both booked more or less succeses. I have also wandered that road in the begining. I tested with A central nozle from above, a central nozle from below....without nozle.

But still, keeping the oxidation fix, remains problematic. Specialy when one has a fluffy air-transparant feedstock such as blocks or chips.


It is dificult to predict the balance air from top/ air from nozle(s) over time and when this balance or unbalance eventualy disturbes the oxidation. People who have followed my tests know, that I myself tried to get more control over the process, by keeping a constant, and vast amount, of  material above my oxidation (My so called “Material Lid”), Mukunde does more or less the same and has even for this purpose build a very high (2.5metres) and slender gasifier tower. He thus has A real masive material lid. It helps also that his fuel (rice peals) is very dense.

Appart from the “Material Lid” I experimented later with a ring cutted around my material tube. (The so called “Slit”). At this “Slit” I observed the kreeping-up came to a stand still.

With every adaption, my gas quality got better and better. It motivated me, to withstand the long nightly burn sessions, glaring for hours in the flare, untill my eyes acked. At last came a giant step forwards which made it even possible to me, to produce tarfree gas with a basic simple gasifier (The DriZzleR) together with a basic simple fuel feed technique (The DriZzling method). This technique made it easy and simply to fix the oxidation on spot.  I discovered this technique after observing the nice blue flare from a dying out gasifier. When I finaly found a way to reproduce this phenomen of a starving gasifier, the DriZzleR was born. Somewhere july/august 2013 I described this invention, filmed it, and named it later “The DriZzling Method”.

This new concept does not only produces tarfree gas, but as prooved by Pascal (Crank) in his cogenerating setup, The DriZzleD gas is perfect engine grade gas. 

Why is it that a “DriZzleR” produces engine grade gas and other open tops as FEMA are producing tar. Lets have a look at this drawing of a simplified DriZzleR. 


Schema of an OPEN-TOP Drizzler-Gasifier


Fundamental diference is; that the oxidationzone in a "DriZzleR" gasifier is not able to kreep up, This by the simple fact that in a "DriZzleR" there is no possibility to kreep up. Where the hopper or the fuel tube in a standard gasifier is kept full, (See a sketch of a stratified gasifier). Or where it is filled up by an auger in order “to feed it” and not to “starve it”, in a Drizzler the hopper is almost completely empty. (apart from a few hundreds gramm coal and the regular few hundred gram fuel to prevent it from burning out). The hopper in the DriZzleR is kept systematicaly at the lowest level. (This level can vary from fuelsort to fuelsort). The little bit material (red in the drawing) is part reduction,coalbed and oxidation, all in one. I call it the “Flaming Pyrolysebed”
Of course, By saying this I excagerated a bit, The layers drying, pyrolysing, oxidating, reducing still are existent but they are so close reacting, that the one can not destabilise the other.
Just an example. In a clasical closed imbert style gasifier, The oxidation (The little exstreme hot ball of fire around the nozle’s) has enormous much to empower. It must; dry and pyrolyse the full hopper of feedstock. At the same time it must bring, in water shift, the mass of falling off condenswater from the fuel without cooling too much down, keeping enough temperature to crack all the light and heavy volatiles and still be able to start the reduction. That is realy the reason why an Imbert is so hard to dimension, to fit nicely  every process together.
In a DriZzleR the whole proces is supersimple. The oxidation, is in contrary to an Imbert Style, very dominant. Not a small ball of fire but a gigantic surface of oxidation to the relative small amount amound of fuel. (only a few hundred grams). The litlle bit of fuel gets dryed almost inmlediatly if not already partly by falling down in the hot fuel tube. It also gets almost inmediatly pyroliest and the little amount of nasty’s getz easely and without any stress handled by the dominant and big oxidation. Theroreticaly all the traditional layers are there but practicaly one can say ‘'”In the Flaming pyrolyses, they are all in one”.
As Stuart Perkins very understandable describes;
The concept is incredibly simple. By restricting the amount of fuel
being gasified to that which is in the immediate vicinity of the
pyrolysis zone, that is, no "full" hopper above, you eliminate the
excessive tars being produced. By keeping the tars being produced to an
absolute minimum, these tars are quite handily cracked by the pyrolysis
zone and voila...engine grade gas. Sometimes, the simplest solutions
evade us for years... We, people that is, are too smart to do the
simple things. Good job Luk, for being smart enough to try something
so obvious the rest of us missed it. ;o)
Because the “pyrolyse/oxidation” or better called the “Flaming pyrolysebed” stays always fixed on the same level by a targeted and limited feed of fuel, there are no nozles needed for fixation of the oxidation zone. Also nozle’s are not needed for suply of oxigen to keep the oxidation going, because trough the open top, the Flaming pyrolysebed is richly flooded with air. One need no lid since there is no build up of gas in the hopper, therefor no puffs. There is no need for a preheating system, because the flaming pyrolysebed gives off so much heat, it inmediatly heats up the inflowing air. Also the fuel tube does not suffer from heat losses because it is vented around the “DriZzle tube” by the upwards streaming gas in the double mantle. No smoke too because the littel amount of fuel is on the spot transferred into coal. No fear for gaspoisining no CO. A "DriZzleR" can be operated fearly safe. 
That does not mean that I will take any responcibility for accidents whatever. Gassing of wood is still a dangerous business. Do not even begin if you are not aware of that and if you are not sure of what you are doing.

”Th DriZzler Method" is “just in time" feeding of the gasifier that little amount that the gasifier is able to inmediatly process. That is the real secret. The method is more important than the gasifier design. Although this new method has led to a very simple gasifier ‘'”The DriZzleR” I am sure it can be aplied to almost any other gasifier design. You can use “The DriZzleR Method” in an Imbert, a GEK, a Victoria and also in a FEMA. And here I am back at the beginning of this article.
There is, as I am aware of, great resistance in the gasifier world to try “DriZzling”. It does away with all the cherished and pampered gasifiing dada’s. Such as nozle designs and openings, airpreheating, complicated formula’s for gasifier dimensions, etc. etc. Seeing that newer gasifier designs are even more going the sofiticated road, it is hard to believe that, one of the most simple gasifier ever build, is able to produce the same and even better quality engine grade gas as the superengineerd types.
See the sketch. It can not be more simple. Only a drum (the ashpit), a Pipe in the drum welded on the lid of the drum, (the DriZzling fuel in pipe), a plate with a hole and a tube under the hole,(the restriction and reduction) unlike Imbert nor very critical, and the length of the reduction pipe according to the wished temperature (The longer the pipe the cooler the exit gas)  If too much gasspeed add eventual a bell. Finaly a grate. As said when one like to make a quick test open your imbert style, close the nozles and start DriZzling. 

One important remark to people asking me for drawings. The “DriZzler” is for us, Pascal and me still a laboratory gasifier project and tests lead still to constant adaptions. But the adaptions are detail adaptions.

The most important in a “DriZzleR” is not the machine but the method.

This is maybe the little disadvantage of a “DriZzleR” One has to get the Knack. One has to get to feel how much or how little fuel one can suply. Best to practise while flaring. In the learnproces always keep an eye on the flare. First, when you burn the charcoal, apears a nice blue flare, later an ugly yellow red and when temperature comes up it gets violet and blue violet. Overall It can take a bit longer to get a flare. By big underpressure around and above 40milibar, with airtransparant fuel as chips beware that your reduction tube is not sucked empty. 

As said above. Restriction is not critical. Pascal (Crank) connected on his same DriZzleR gasifier a 1.6liter VW car engine and later it worked fine, with the same setup, also with a small honda.

When you get the Knack by DriZzling, you can later easely automatises “DriZzling” with an augerfeeder based on time interval.
Beware. This is only the fact with generators connected and controlled by the grid and by small generators where the load is little. By isle operation with variable load on a bigger engine and generator, a level controler for the “Flaming Pyrolysebed” will be needed. Pascal  right now is testing several options. Tom is testing with temperature changes. 

So if you want to try. Much succes. Me and Pascal are ready to help.

Post here your experiences so we can all learn from it. More heads, more knowledge. And be fair. If you post or mention somewhere else your results give credit to the inventors, me and Pascal, and use the right terminology “DriZzleR”, “DriZzleR gasifier” and “DriZzing Method”. 

Thank you all 

Luk.

Kommentare:

  1. Nice work, Luk! Stephen is sending me a Victoria. I am certainly going to try DriZzling.

    A couple of questions: are any of the downstream components affected? In other words, can we keep the same cyclone, the same media filter, the same radiator? I keep seeing the term "engine-grade gas," and I'm wondering if that means right from the "gas out" tube, or after all the typical filtering...

    Thank you!!!

    Troy

    (BigDaddy on the forum)

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  2. Troy,
    Good you will try DriZling. Realy like to have some more people on board. because The DriZzling method is a complet fresh way of running a gasifier and we are still in the laboratory fase. The more testers, the more experience. We do not know yet everything and learn from the small but steady growing group of brave people that are willing to try, as much as we are learning from our own tests.

    As for your question, as once Stephen also said, If the flare is clear blue you can run an engine of it. You can Judge for yourself how an unfiltered DriZzler flare looks like, in the flare examples on this blog.The problem is neither Pascal nor me Have dared to risk our engine with gas straith of the gasifire. It sure is tarfree gas. This we can tell from our vacuum blower when after a session it still runs and start inmediatly. A Vacuum blower having thin fins stucks up inmediatly when tar condensate on the fins. But tar is not the only isue. There is the ultra fine soot that mixes with the condensate and makes a nasty fine abrasive pasta that might kill an engine fast or at least shorten its life. I hope Pascal jumps in on this because he has the most experience. He actualy runs his gas first to a cyclone, then he has a bag filter made of some material as used in welding blankets and then he cools the gas into a heatexchanger and after that he takes the excesive water out the gas in a primitive condensor made of plastic pipes. Reffering to engine grade gas, we do not meanDriZzleR gas is ready to run in your engine straith out of the gasifier. No gasifier can do that. There is still the temperature isue and the soot isue. Tar, as produced in the other open top The FEMA, is no isue in a DriZzler.

    Luk

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  3. Hello,

    Regarding the problem of automatic feeding. You could can try a "constant pressure method". That means is to drop more fuel when pressure drops to less than 40mbar (or whatever pressure you need to drive a certain engine). A lower pressure (e.g. 38 mbar) means there is not enough fuel left, gas passes easier through gasification zone - start the feeding auger. A higher pressure (eg. 42 mbar) means there is enough fuel, stop the auger. Not sure if this works but I'm sure that different pressures (having the same blower rpm) means different gas speed in the pipes. Constant pressure means constant flow of gas.

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    1. Hi Anonymous :-)
      why are you not posting your name?

      The fuel feeding to be regulated via the underpressure is difficult. The DriZzleR works just in time. Only the absolutely necessary amount for gasification. Once the vacuum has fallen, it is already too late. Then there is nothing combustible in the gasifier. Also, a control for different load conditions in island operation can not be regulated. The generator sucks sometimes more or less gas from the gasifier with various underpressure. The aim is always to keep the flamming pyrolysis at the same height.

      regards Pascal Kirchner

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