Cast Batch Box Rocket Mass Heater using LTGS

[sksshel]

I am currently planning to build a Cast Batch Box rocket mass heater (RMH) using Low-Temperature Geopolymer Setting (LTGS).



I've built a working J-Tube RMH out of LTGS in order to test the techniques and materials. So far so good. I will attach pics of all the items mentioned in this post as replies to the post.



My primary sources of information in this endeavor are:

- this website

- Erica and Ernie Wisner's book "The rocket mass heater Builder's Guide"

- Peter van den Berg's web site: batchrocket.eu/en/

- the LTGS website I was using is no longer available.



The primary design components are as follows:

- 6" Chimney and overall system

- The batch box will be 7 cast parts: (Floor, Right side, Left side, Back wall which includes the front bottom portion of the heat riser, Back bottom heat riser, Front top heat riser and Back top heat riser)

- I will use 5 forms to cast the batch box and heat riser (2 are reusable)

- Bell will be 3 layers with a 1/4" steel "lid" on top. The layers consist of 1 1/4" LTGS on the inside, 4" concrete bricks outside of that and a decorative stone veneer

- the Batch box will be raised off the floor 9"

- the Bell will be 13.5" x 13.5" x 67.4"

- the Bell ISA computes to 25.6 cu ft

- the Heat exchange will be a total of 8' long with 3 turns

- the Heat exchange ISA computes to 31.4 cu ft

- for a Total ISA of 57.0 cu ft .1 under the target ISA of 57.1 cu ft

- there is 2 3/4" clearance on each side of the heat riser inside the bell giving a 185 sq in CSA. This gives a 6.6/1 ratio exceeding the 5.0/1 requirement.

- a 1 1/2 story class "A" chimney will be installed inside the house through the ceiling and the roof.

- approximately 5 cu ft of LTGS will be needed at a cost of about $200 total (not including the J-tube prototype)



My questions:

1 - Will the LTGS use within the bell inhibit the system "draw"?

2 - Am I missing anything else?

[sksshel]

I am unable to upload any pics at this time. You can see them here:

permies.com/t/71834/Cast-Batch-Box-Rocket-Mass#599474

[Deleted]

The LTGS mixture has a relatively low thermal conductivity of about 0.3W/m*k
similar to underfired bricks.

With respect to the price you may also test the phosphate fertilizer mixture at:
Cheaper and user friendlier Geopolymerization Agents
donkey32.proboards.com/thread/2346/cheaper-user-friendlier-geopolymerization-agents

[sksshel]

Oct 28, 2017 9:37:45 GMT -8 @karl said:

The LTGS mixture has a relatively low thermal conductivity of about 0.3W/m*k
similar to underfired bricks.

Are you saying this mixture won't work for what I'm attempting?  I don't understand what "underfired bricks" are.  

[sksshel]

Oct 28, 2017 9:37:45 GMT -8 @karl said:

With respect to the price you may also test the phosphate fertilizer mixture at:
Cheaper and user friendlier Geopolymerization Agents

I've already purchased the components and tested the mixture.  Is it worth the effort to retrace the process several steps?

[Deleted]

Underfired bricks are not fired high enough to close all pores
and thus have a relatively low thermal conductivity.

Everything made with the help of water
has a porosity left over by the water.
Hard fired firebricks are completely vitrified, the pores closed and have thus a higher thermal conductivity.

If you have already purchased the components, just continue.

[esbjornaneer]

Steve it would be great to have an update on your progress, and any pictures of how you made the forms.

@karl do you mean that LTGS is about equivalent to insulated fire bricks for thermal conductivity?

[Deleted]

The above mentioned 0.3W/m*k at arount 1000°C/1832°F is a pretty good insulating value.
Lower conductivities are possible.
Depending on the clay or other amino silicates,
the kind and amount of binder and
finaly the amount of water
LTGS may even beat insulating fire bricks.

[esbjornaneer]

You are quite right Karl, the figures I have founf for insulated fire brick is 0.29 @ 600C and 0.33 @ 1000C. With this clarification of the temperature it is already more insulative than insulated fire bricks

[drooster]

Oct 28, 2017 5:42:24 GMT -8 sksshel said:

I am unable to upload any pics at this time. You can see them here:

permies.com/t/71834/Cast-Batch-Box-Rocket-Mass#599474

Thanks for the link.
You didn't get a single reply on your Permies thread, that's a shame.

Exactly how did you make the material for your J-tube lower casting?

[briank]

Oct 28, 2017 5:42:24 GMT -8 sksshel said:

I am unable to upload any pics at this time. You can see them here:

permies.com/t/71834/Cast-Batch-Box-Rocket-Mass#599474

You can link the photos in the thread there to this forum:


This is excactly what we need to see here as far as photo documentation goes. Thank you!

[esbjornaneer]

Dec 30, 2017 8:26:39 GMT -8 @karl said:

The above mentioned 0.3W/m*k at arount 1000°C/1832°F is a pretty good insulating value.
Lower conductivities are possible.
Depending on the clay or other amino silicates,
the kind and amount of binder and
finaly the amount of water
LTGS may even beat insulating fire bricks.

Do you know a figure for conductivity at lower temps too? 600C?

[Deleted]

I have only looked up the very high temperature conductivity,
which is the only of real interest as all others will be lower.

[sksshel]

Dec 30, 2017 13:20:10 GMT -8 drooster said:

Oct 28, 2017 5:42:24 GMT -8 sksshel said:

Thanks for the link.
You didn't get a single reply on your Permies thread, that's a shame.

Exactly how did you make the material for your J-tube lower casting?

[sksshel]

The inner form is made entirely from wood. I used "Liquid Nails" to hold it together. Once the LTGS is poured and cured, I burn-out the inner form with the first firing. That's of course after the outer form has been removed.