I was wondering if anyone tried using fire bricks in the combustion area of a gasifier? It seems to me that the more heat you can keep in a small space without lose, the more efficient it could be?
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Yes. A couple of guys have tried to use the firebricks as the (or stiffened Kaowool) as the gasifier hearth inner surface. Proved your point.
This must be, and remain gastight. Poker poking; and thermal cycling very hard to keep this gas-tightness integrity.
The way to use the insulative fire and kiln bricks IMHO would be as in a modern wood stove.
A welded steel plate metal structure is the form, and gases-tight container.
The loose fit inner fire/kiln bricks as the insulator and sacrificial save-the-metals “wear” in direct hot char contact surface.
Steve Unruh
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Awesome, do you by chance have a link so I can look into them? I’m planning on turning a old gas water heater into one, and would like to use plaster of Paris and perlite to insulate the combustion chamber after doing some test runs on how fast it’ll burn through charcoal.
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Somewhere there is a picture from AussieDave showing the result of using a fire brick bored out to make a nozzle. Even it didn’t fair well at reactor temps. Of course that was at the heart of the reaction zone and not the perimeter. Convinced me to not try and use a fire brick to shield a black nipple nozzle.
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Here is a gasifier diabolo with an alumina coating of 3 tons of density per meter 3, at the stop of the passage of gases, in the throttle, we obtain 1600 degrees, but it takes 4 hours to reach cruising speed, and this is only very good gas coming out of it.
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Hello Robert , what type of Gasifier are you planning on building is it a raw wood or charcoal gasifier ? only you mention wanting to test how fast it will burn through charcoal .
If it is a charcoal system you are thinking of building then can I suggest that you do not need insulation at all as the charcoal you will be burning will be all the insulation you should need .
Dave
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One challenge of using refractory is the mass. It absorbs heat. This slows the time it takes to get the hearth up to temperature.
If you want to work with brick - there are a number of things to consider about brick which I will mention below. Another option is to use a castable refractory. This is a dry formulation that sufficient water is added to in order to make a formable paste. This is cast or formed and allowed to dry and then can be used. There are a number of grades/types. Some are quite smooth in texture while others are very gritty - containing an aggregate type of material.
When you talk fire brick - there can be a number of items not fully realized. There are different grades of fire brick. What most folks think of as fire brick are those used in wood burning stoves. Cheep store bought brick may only be 2000 degree rated. I sold 3000
degree rated brick. Generally speaking you can’t see the difference between them. Those yellow colored brick are not as insulating as one might think. They absorb and distribute heat. They are dense, hard and rather tough. This helps them to withstand fire wood being tossed onto them and such. They are dense from having been made as a “dry pack” refractory that is damp when formed under pressure and vibration in molds. then dried and vitrified in a kiln. They serve duty in a wood stove to be able to withstand the high temperature and act as a buffer between that high temperature and the stove. Ash that settles between the brick and the stove acts as an insulator - helping buffer the temperatures even more…
There are also brick which are far more insulating. I’m forgetting what they are called other than kiln brick. My dad knew the official designation. They are very light weight as the refractory appears foamed. These lightweight brick are soft and easily damaged - but of possible interest - easily reshaped. You could use a wood cutting carpenters saw to cut them. You could make a drill out of rod with a slight flattening on the end and run in a drill motor. Heck - a hand held screw driver would probably work.
Another brick is one generally found in steel mills. It is made of chrome and magnesite. I’ve only seen these a couple times. They are dense, dark - nearly black in color. I don’t know if there would be any benefit for using them.
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My favorite site to look at, I have not purchased from them. Lots of answers in FAQ section. My gasifier will have refractory, as I plan many experiments.
High Temperature Tools & Refractory | Supplies (hightemptools.com)
They are mostly into forging and metalwork.
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Those are not bad prices for the 3000F castable Mike. I didn’t want to look at what the shipping would be.
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Right now I’m going to try a charcoal gasifier first, because of how easy it looks to make. But I was thinking i could also make it so it can take wood as well, but that would be much further down the road right now. Looking at it, I got some plaster of Paris and some perlite that I’m planning to make the refractory with, because they seem to have the lowest thermal transfer. I’m also going to make it out of a 50 gallon gas water heater. 
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Right now I’m planning on using plaster of Paris, and perlite to insulate the burn area. And I’ll be making this out of a gas water heater, so it should hold a lot of charcoal.
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I have no experience with that.
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Hi Robert , if this is your first ever build can i suggest something that will hopefully help you .
Start off with a wood or a charcoal gasifier , don’t start off trying to build a duel fuel rig without first running one or the other .
If it is a charcoal gasifier you are wanting to start off with then please look at Garry Gilmores simple fire charcoal gasifier , you can search for it at the top of the page or go too YouTube .
Do not worry about pearlite and plaster of paris around the burn area its not needed as charcoal itself is a wonderful insulation , if you feel you really need to make sure the outside of your tank stays cool then wrap some glass wool insulation and then cover that with some thin steel to hold it in place if your worried about excess heat .
If you want something that will just run and run with little to no operator interference once going then you will be hard pushed to find a simpler way than a “Simple Fire”
If you decide to go down this route and want more info for building a rock steady gasifiers then ask away or look in the small engine section in the search window at the top of the page .
All the best Dave
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Do not forget, we are talking about insulation, but also we must understand the radiation of refractory concrete, which helps to work more in the heart of the biomass, attached a photo that lets you imagine the temperature.
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Here is a short video with another idea for temperatures, this was after a 35 miles drive and camera had exposure problems focusing on the char bed it was burning so hot and bright
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