For more than 50 years, Refratechnik has carried out research and development in the field of biogenic silica. First experiences in thermal processes have led to a continuous expansion of know-how and our own production of the material. The thermal insulating properties have been further developed and specialised for today’s applications. The development of the special insulation REFRATHERM® Eco for use in the heavy clay industry opens up convincing new applications.

1. REFRATHERM® Eco
High-end insulation
for the tunnel kiln car

2. REFRATHERM® Eco –
high insulating biogenic silica
Biogenic silica (SiO2) is pro-
duced through the burning
of biomass, the ashes of
which mostly contain SiO2.
REFRATHERM® Eco is thus
based on a naturally renewable
resource.
For more than 50 years,
Refratechnik has carried out
research and development in the
field of biogenic silica. First expe-
riences in thermal processes have
led to a continuous expansion of
know-how and our own produc-
tion of the material. The thermal
insulating properties have been
further developed and specialised
for today’s applications.
The development of the special
insulation REFRATHERM® Eco
for use in the heavy clay industry
opens up convincing new appli-
cations.
Production
The term biogenic silica shows
the origin of the product.
In modern biomass power plants,
subject to quality controls, these
raw materials are used as an
­energy source because they burn
CO2 neutrally. That means, when
burned, no more CO2 is released
than the plant had previously
absorbed from the atmosphere.
An aspect which is becoming
increasingly important for the
raw materials of the future.
Characteristics
Biogenic silica is chemically very
pure and consists of 94-96% SiO2.
The main phases after a special
burning process are amorphous
­silica, tridymite and cristobalite.
This causes the high melting point
of approx. 1650 °C. In production,
the volatiles burn but the micro-
porous structure of the SiO2 is
maintained. This structure results
in both the extremely low thermal
conductivity as well as the low
bulk weight.
Biomass power plant
Tunnel kiln car with
REFRATHERM® Eco insulation
2©Refratechnik Ceramics GmbH

3. REFRATHERM® Eco based on
microporous silica shows a unique
combination of well-defined
­characteristics such as high insu-
lation, good flow properties, set
grain structure. This allows for
very low installation heights and
thus more usable firing capacity
for the brick manufacturer.
The installation time of the insu­
lating layer in the tunnel kiln car
can be reduced by about 50%
depending on the flow properties
set.
Typical characteristics
• Sintering point: 1550 °C
• Melting point: 1650 °C
• High microporosity and
thus excellent insulation
• Perfectly optimised flow
properties
• Low density
• Extreme low thermal
conductivity
REFRATHERM® Eco –
the ideal insulation in the tunnel kiln car
Microporous structure of the SiO2
Comparison of insulation effect
ThermalconductivityinW/m·K
Temperature °C
REFRATHERM® Eco
0.5
0.6
0.4
0.3
0.2
0.1
0
250 600 800 1000
BUROLIT® 230 BUROLIT® G
Technical specifications:
General
Raw material basis Biogenic silica
Condition of material not ground / dried
Mineralogical composition Amorphous silica, tridymite, cristobalite
Application Thermal insulation
Maximum grain size mm 4
Physical properties
Bulk density kg/m3
100-160
High temperature behaviour approx. °C
Sintering point
Melting point
1550
1650
Chemical analysis Weight % (Typical, free of loss on ignition)
SiO2 92-97
K2O+Na2O 2-4
MgO 1.0
Al2O3 1.0
CaO 1.0
Fe2O3 1.0
Remainder 1.0
Loss on ignition Weight %
Carbon C 6.0
Moisture 1.0
3©Refratechnik Ceramics GmbH

4. Cs1-010-10/2015
Refratechnik Ceramics GmbH
Barkhausener Str. 55
49328 Melle
Germany
Phone +49 5427 81 0
Fax +49 5427 81 102
ceramics@refra.com
www.refra.com
Cs1-010-10/2015