Looking for flame resistant insulation materials:

I'm looking to improve the efficiency of my Blichmann floor burner over a series of fairly simple projects.

My first step is to make a close-kept wind screen to keep the hot gases in contact with the boil kettle.

I need an insulation that:
1) doesn't catch fire
2) is rigid
3) can be shaped without special tools

What is out there?

Currently I am using a fitted cardboard box. It's helped quite a bit when it doesn't catch fire.

Is your kettle wide enough?

I have never had similar issues with my Blich burner, and I live in a rather windy area.

There's a type of manufactured building stone or concrete that is aerated and very light weight. It comes in blocks and can be cut and shaped with normal saws and knives etc.

Being a mineral-based product I'm pretty sure it is fire proof.

I'm sure builders etc here on the forum will be able to put a name to what I'm talking about.

Anybody?

i bought a roll of steel flashing and then made two layers seperated by bolts with nuts on either side to create an airspace between the two layers. Then I wrapped the outside of that in high temp bubble insulation..let me see if I have a pick handy if I do ill post one or try to get one tommorrow to show you what I did. it works incredibly well and I have used it for over a year. You have to be careful NOT to shroud your gauges and valeves etc though or youll dmage them from the heat.

Couchy said:

There's a type of manufactured building stone or concrete that is aerated and very light weight. It comes in blocks and can be cut and shaped with normal saws and knives etc.

Being a mineral-based product I'm pretty sure it is fire proof.

I'm sure builders etc here on the forum will be able to put a name to what I'm talking about.

Anybody?

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sounds like you are talking about pumice maybe..

Rockwool is a mineral insulation that is cheap, waterproof, and fireproof. It is not completely rigid, but it does come is batts that hold their shape.
Bonus... it's not itchy.

jabba11 said:

sounds like you are talking about pumice maybe..

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No, pumice is a naturally occurring material. The stuff I'm talking about is man-made.

One brand here in Australia (and maybe world-wide) is Hebel. Comes in blocks and panels of various shapes and sizes:

"Hebel panels and blocks are highly fire resistant (do not burn and will not explode even under extreme bushfire conditions), have high acoustic absorbing properties and, because Hebel is a masonry product with in-built insulation, it assists in improving energy ratings."

http://www.hebelaustralia.com.au/Pages/About/High-performance-lightweight.aspx

jabba11 said:

i bought a roll of steel flashing and then made two layers seperated by bolts with nuts on either side to create an airspace between the two layers. Then I wrapped the outside of that in high temp bubble insulation..let me see if I have a pick handy if I do ill post one or try to get one tommorrow to show you what I did. it works incredibly well and I have used it for over a year. You have to be careful NOT to shroud your gauges and valeves etc though or youll dmage them from the heat.

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You can do a simpler version of what jabba is talking about with a single shell chimney (in addition to the burner wind screen.) The biggest benefit comes from keeping the hot combustion gases in close proximity to the bottom and walls of the BK, instead of letting them dissipate once they get around the bottom. The chimney will get hotter than an unshrouded BK, so it does represent a contact burn hazard. Insulating the outside of the chimney would provide slightly improved effeciency, but it's a case of diminishing returns over just the chimney alone. A double shell chimney will stay cooler on the outer shell, and the improved safety might be worth the extra fabrication effort. Use metal spacers to keep a consistent BK to chimney spacing. A little study of furnace or water heater flue sizing rules would help optimize the chimney to BK spacing (flow cross sectional area.) A simple 2D schematic is shown below.

Brew on

Ah, so that's called a "chimney". That's exactly the idea I was going for. The spaced concentric metal chimneys seem like a good idea, since I am concerned about the obvious contact burn hazard.

I also assume a more insulated chimney is best, since what I am trying to avoid is heat escaping to the ambient air so easily.

DSorenson said:

I'm looking to improve the efficiency of my Blichmann floor burner over a series of fairly simple projects.

My first step is to make a close-kept wind screen to keep the hot gases in contact with the boil kettle.

I need an insulation that:
1) doesn't catch fire
2) is rigid
3) can be shaped without special tools

What is out there?

Currently I am using a fitted cardboard box. It's helped quite a bit when it doesn't catch fire.

Click to expand...

Space Shuttle tiles should do the job nicely. Maybe there are some used ones out there :cross:

DSorenson said:

Ah, so that's called a "chimney". That's exactly the idea I was going for. The spaced concentric metal chimneys seem like a good idea, since I am concerned about the obvious contact burn hazard.

I also assume a more insulated chimney is best, since what I am trying to avoid is heat escaping to the ambient air so easily.

Click to expand...

Chimney insulation will have a minor effect. Most of the heat that is lost (doesn't go into the wort in the BK) is in the exhaust flow out the top of the chimney (between the chimney and the BK walls.) In the case of a double shell chimney, the second most important source of heat losses will be the convective air currents between the two shells. The best way to minimize this loss is to prevent free air flow between the shells, which can be accomplished by sealing the gap between the shells at the top of the chimney. This could be done by cutting tabs in one of the shells with the length of the tabs equal to the gap between shells, and then bending the tabs at 90 deg towards the other shell. The remaining small gaps could be sealed with a high temp silicon (automotive.) Before going to the trouble of insulating the outer shell, I would recommend test runs to see how hot the outer shell gets (an infrared thermometer would be good for this.) Unless it gets over about 120-125 deg F, I wouldn't bother to insulate the outer shell.

Brew on

Insulating the chimney does help. Made one myself, check out the pot skirt link in my sig.

Here is where I got some of the info... http://www.vrac.iastate.edu/ethos/fi..._Andreatta.pdf

purplehaze said:

Insulating the chimney does help. Made one myself, check out the pot skirt link in my sig.

Here is where I got some of the info... http://www.vrac.iastate.edu/ethos/fi..._Andreatta.pdf

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Purplehaze: It looks like your chimney is single shell. Is this correct? If so then insulation will be much more effective than it would be on a double shell chimney. I want to work on a double shell chimney, since if it is constructed correctly, it will hold it's shape a lot better than a single shell, and it may not be necessary to mess around with insulation.

Also, thanks for the link to the paper. I need to take some time to read and understand it. Now that I am retired, it might be fun to get some open source CFD software and model some different configurations.

Brew on

Sorry it took so long heres what I was talking about..

Id also like to remphasize the bit about NOT shrouding your gauges and valves etc...yes this is like a double walled chimmney or gas vent pipe. I shudder to think what a piece of stove pipe that big would cost though

We have that brick in our heat treat ovens here @ work, and we call it "fire brick", lightweight, easy to cut, and messy.

Stealthcruiser said:

We have that brick in our heat treat ovens here @ work, and we call it "fire brick", lightweight, easy to cut, and messy.

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Fire brick, huh? You have interested the OP.

DSorenson said:

Fire brick, huh? You have interested the OP.

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There are many versions of firebrick, from dense, relatively poor insulators, to porous, insulating firebrick. I would not choose porous firebrick for insulating a BK after having worked with it in college. If you want to insulate, I think purplehaze is on the right track with the welding blankets.

Brew on

We be sportin' the "porous , insulating" version.

Works well on the walls and doors of our 1000 + plus degree oven.

Stealthcruiser said:

We be sportin' the "porous , insulating" version.

Works well on the walls and doors of our 1000 + plus degree oven.

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Yeah, good stuff, for its intended applications. I used a 3000 F (1650 C) version for a small gas fired lab furnace. But, it is crumbly if handled too much. Building an easy to use, and remove, shell of it for a BK isn't worth the trouble IMHO. A metal shell, with or without blanket insulation will stand up much better to the type of handling it will receive in a homebrewing application. YMMV.

Brew on

doug293cz said:

Yeah, good stuff, for its intended applications. I used a 3000 F (1650 C) version for a small gas fired lab furnace. But, it is crumbly if handled too much. Building an easy to use, and remove, shell of it for a BK isn't worth the trouble IMHO. A metal shell, with or without blanket insulation will stand up much better to the type of handling it will receive in a homebrewing application. YMMV.

Brew on

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I guess I am going to go with this option then! Now if I can just get to building it...