Why not use INSULATED fire brick (IFB)?

[exoplasmic]

Warning: rant follows...
I've seen a lot of designs for rocket stoves and batch rocket stoves that are built with the dense fire brick or perlite and "home made" or DIY firebrick ( at least use vermiculite!). Why don't folks buy insulated fire brick (IFB)? Anyone who builds a kiln (for pottery or ceramics) always uses the super light insulated fire brick because it looses so little heat. It is a perfect material for a combustion chamber. Does wood combustion gas degrade IFB so much that it is just not worth the expense to replace? Or is it just that people are not familiar with the stuff or don't know where to get it? It is more expensive, but not that much more. And when you use regular fire brick you should wrap it in ceramic wool. So you're not really saving anything. Plus IFB is so easy to re-shape. You can round it off with a sharp stick if you don't want to dull your knife or file. A box of 10 costs $35 on Amazon or eBay, Or pick it up at your refractory outlet (they will order it for you too). You need at least 2 boxes (20) for a typical heat riser. Maybe 3 boxes just to be sure. With free shipping it's not that bad. It is so worth it for "complete" combustion. As log as you have the three T's: Time, turbulence and temperature, plus 1 to 3% excess oxygen (no more than 3%) IFB is your icing on the cake.

(I wish I had more IFB).

[martinpolley]

I think it's mostly to do with durability. Adding wood, poking at the fire, scooping out ash, they're all going to abrade the bricks.

There's also the issue of cold starts. Regular firebrick takes longer to cool down than the insulated stuff, so if you fire regularly, you'll probably be starting warmer than with insulated bricks.

Having said that, I think a heat riser made of insulated bricks would work well. I'm pretty sure Adiel has done this (I think I saw it in one of his YouTube vids). So maybe he can chime in on how well it worked.

[satamax]

There's plenty of people who've used it. I think the culprit is, that theses are not cheap. If i could find as many ifb as heavy firebricks secondhand, or for free. I would use theses more. A cheap alternative, is to use splits and air entrained concrete behind.

[sothiseeker]

I have been playing around with designs and some little J tube models using local brick and clay, and am ready to graduate to actually building a stove now (I think). Just got a great deal on some new soft IFB 26, and am getting ready to build my burn tunnel and heat riser out of it. I have two questions for you helpful savants out there: 1) I am guessing I don't need to wrap soft IFB 26 in any further insulating material (rated to 2600 F) when using it for the J tube, does this sound right?. 2) I have enough hard FB rated to (I think) about 2300 F, and am planning on using it for the internal portion of the Feed Tube to ensure that loading wood/fire poking, etc don't wear it out too fast. Any problems combining hard and soft FB of different thermal capacities in the Feed portion of the J tube? Thanks in advance for any wisdom!!

[Deleted]

I've done exactly as you suggest. And its working VERY well. Ive also used a combined a perlite/refractory cement mix lined with hard firebrick in the feed. Again works great. They both work well. IFB is lighter and probably easier to work with and not that much more expensive really.

[azor]

Aug 7, 2015 19:42:02 GMT -8 sothiseeker said:

I have been playing around with designs and some little J tube models using local brick and clay, and am ready to graduate to actually building a stove now (I think). Just got a great deal on some new soft IFB 26, and am getting ready to build my burn tunnel and heat riser out of it. I have two questions for you helpful savants out there: 1) I am guessing I don't need to wrap soft IFB 26 in any further insulating material (rated to 2600 F) when using it for the J tube, does this sound right?. 2) I have enough hard FB rated to (I think) about 2300 F, and am planning on using it for the internal portion of the Feed Tube to ensure that loading wood/fire poking, etc don't wear it out too fast. Any problems combining hard and soft FB of different thermal capacities in the Feed portion of the J tube? Thanks in advance for any wisdom!!

from kiln experience,no real issues of IFB and hard brick together, the hard brick will expand and contract at a differs rates, so keep that in mind. Makes sense to use hard brick where wood pieces will be and clean out will occur.
no need to wrap 2600 IFB, as long as your mortaring it, as to not get air gaps in the riser.