Vermiculite Board hot face insulation on a biochar kiln

Insights on Using Vermiculite Board for Hot Face Insulation

I wanted to take a moment to share some valuable lessons learned about using Vermiculite Board for insulating hot surfaces, particularly in the context of our Biochar kiln prototype.

Project Overview

In this instance, we had Vermiculite Board cut into panels that were glued onto a mild steel surface. This specific area of the kiln is directly exposed to flames within the combustion chamber. Unfortunately, after only about ten uses, we decided to abandon this design, leaving the panels exposed to the elements for the past 12 months. As a result, you can see significant crumbling in the video but only on the edges.

Key Takeaways

Moisture Exposure: It’s clear that allowing moisture to come into contact with vermiculite is detrimental. This material does not perform well when subjected to wet conditions.

Heat Resistance: While we are still evaluating how well vermiculite withstands prolonged heat exposure, initial observations suggest that the adhesive used to bond the panels shows minimal signs of degradation.

Importance of Insulation: Failing to insulate surfaces can lead to serious consequences. Continuous exposure to high temperatures can cause metal components to corrode and warp over time. Proper insulation helps maintain structural integrity as long as it remains intact.

Durability of Vermiculite: Vermiculite boards tend to degrade primarily due to exposure to the elements or physical abrasion. In our case, we chose not to insulate higher up on the kiln since the flames do not reach that high, and we wanted to avoid potential peeling due to gravity.

Future Considerations

Will the insulation hold up? I believe it has a good chance of remaining intact in both lower and upper areas. I still maintain that vermiculite is a more cost-effective option compared to other high-heat materials like castable ceramics, bricks, and fiber plaster.

Looking ahead, I am optimistic about using vermiculite for our Black Ripple rocket-fired kiln, as it appears well-suited for our needs.

Facts about vermiculite board

From: https://www.v-core.co.za/vermiculite/ 

“Vermiculites crystal structure and chemical characteristics make it ideal for fire protection, insulation, and many more applications, e.g. as a growing medium in horticulture/agriculture. Contrary to asbestos it is non-carcinogenic, absolutely safe, and 100% recyclable!”

“Chemically, vermiculite is a hydrated magnesium aluminum silicate and exfoliates (expands) up to 20 times its original size when heated with over 1000 degrees Celsius. Exfoliated vermiculite is non-combustible, compressible, highly absorbent, and nonreactive and it also possesses high cation exchange capacity.”

“The color of raw vermiculite is light to dark and brownish to green. When exfoliated under heat, the color changes to an appealing lustrous gold/golden brown with a silver (or) bronze tint.”

See 2023 estimate and brochure below. Add probably 25% to compensate for price increases up to 2024.

Adios Amigos