[q]Re-reading the article on the Kalle gasifier and his method of filtering only the very fine particles of charcoal into the reaction zone in order to get a high rate of gasification gave me an idea. As I have said on many occasions, it is the fuel handling process which need the most thought, when using alternative (solid) fuels Most of you will have seen these “bag-less” vacuum cleaners which use a cyclone action to spin the dust out of the airsteam. This is not new technology as it has been used in sawmill dust extraction systems for decades as a way of getting the sawdust away from the workplace. As you decrease the diameter of the conical cyclone container, the air speed increases and the dust particles experience a radial force which separates them from the airflow. Now if you inspect the contents of you vac-cleaner’s dust container, you will see all the large stuff in the big scuttle separated in a series of layers (depending on particle size and density). The very fine dust particles travel into a second smaller cyclone (Dyson dual-cyclone technology) where they are separated out into the inner container. – Exactly what you need for an efficient gasifier – only the fine stuff in the reaction zone! Now Kalle used an ingenious mechanical system for breaking up the charcoal into fine particles, using a poking method driven by an air diaphragm which moved in and out with the suction demand from the IC engine. This poking action ground up the larger charcoal particles and delivered them to the reaction zone. But the point is this; any gasifier has to process its fuel by a series or mechanical fuel handling steps which ultimately delivers the fuel to the reaction zone in a finely divided particulate form. If these mechanical processing operations can be done automatically, then even better.
So consider this as the fuel handling route. First you start with wood waste blocks or greenwood branches which first have to be chipped into ¼” chips. This is easily done with a high speed rotating blade – just using garden shredder technology. This shredder part will need a couple of hp to work it, but it only has to be run for a few minutes at the start of each batch.
Then you deliver these ¼” chips into a slowly revolving drying oven – which is heated by the waste heat of the engine exhaust or by burning some of the charcoal fuel. A hot gas stream is used to dry the chips and also carry away any water vapour or volatile compounds to the reaction zone. The chips are mechanically graded in this sifting drum oven (think of a stainless steel washing machine drum – both inner and outer parts – with different sizes of holes) and the chips slowly carbonise and get sorted into various sizes as they travel towards the bottom of the drum. A set of pulveriser wheels is used to break up the obstinate chips – but when they are charred they will become quite friable.
Another idea would be to make the inner drum from stainless steel, but with the holes punched like a cheese grater – rough, sharp and burry. The chips are introduced into the gap between the inner and outer drums and are grated and ground up as they pass downwards. The high speed gas stream is then used to continuously grade and deliver the charcoal dust by way of a cyclone into the reaction zone, where the now red hot charcoal dust is reacted with CO2 and hot steam to yield flammable wood gas constituents H2 and C0 which are fed to the IC engine, steam boiler or furnace. Any fine particulates which escape from the reaction zone in the gas flow can be returned to the cyclone in the hot gas flow. This system would be designed to work with a wide range of fuels, chips, husks, etc. [/q]
[a]
Sounds like your on to something here with the centrifugal grinding and separation of charcoal fines. Even I could use a good line drawing sketch on this one. I’m sure everyone else would appreciate. Can you just sketch one up, and scan and paste to E-mail? We need to use a variation of that same technology, to make a charcoal powered turbo jet engine. One that uses fuel cartridges that we both agree are the way to go, with powdered charcoal (see earlier Sept. E-mails on gasification and wastewatts). Maybe the cartridges could act in gasifier “fuel tanks” and the gas go to somewhat more conventional type turbojet engines, modified to the task.
Some pressure from the gasifier would be part of the final thrust. This because almost half of the energy is released gasifing the charcoal. I’m kicking this out to the gasification people, because their are some real Biomass wizards there. I think they all fell asleep. They can look up the first part of this post on wastewatts. Maybe they are interested in Babbington burners, for biooils too? [/a]
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