Industrial furnaces, steel ladles, tundishes and kilns operate with intense heat inside a steel structure.
The refractory lining protects the equipment from direct heat, flame, slag or molten metal. But the refractory alone may not provide the required level of insulation.
Heat can still travel through the lining and reach the external shell.
Microporous insulation is installed behind the refractory to control this heat transfer. Its exceptionally low thermal conductivity allows a thin layer to provide strong thermal resistance.
This makes it particularly valuable when lining space is limited.
Microporous Insulation Technology
Microporous insulation is a compact, high-temperature insulation material made from fine silica particles, reinforcing fibres and infrared opacifiers.
These materials are compressed into rigid boards, flexible panels or application-specific shapes.
The structure contains extremely small pores. These pores restrict the main ways in which heat travels through insulation.
As a result, microporous insulation can provide effective thermal protection without requiring a thick backup layer.
Why Does the Backup Layer Matter?
A high-temperature lining normally contains several materials.
The working lining faces the process. It must resist temperature, chemical attack, erosion and mechanical wear.
A safety or permanent lining provides additional protection behind it.
The backup insulation is placed closer to the steel shell. Its purpose is to slow the remaining heat before it reaches the equipment structure.
Although this layer is hidden, it can influence:
- External shell temperature
- Heat retained inside the process
- Required lining thickness
- Thermal stress on the steel structure
- Fuel or electrical energy demand
- Temperature stability during holding and transfer
The backup layer therefore needs to be treated as an engineered part of the lining, not simply as a space-filling material.
How Microporous Insulation Controls Heat Transfer
Heat moves through an industrial lining by solid conduction, gas conduction and thermal radiation.
Microporous insulation is designed to restrict all three mechanisms.
It limits heat flow through solid particles
Heat can travel through direct contact between solid particles.
Microporous insulation uses very fine particles with limited points of contact. This reduces the continuous solid paths available for heat to follow.
It restricts heat carried by gas
Gas inside conventional insulation pores can transfer heat from the hot side to the cold side.
The pores inside microporous insulation are extremely small. Gas molecules cannot move and transfer energy efficiently through this structure.
This is one of the main reasons for the material’s low thermal conductivity.
It controls infrared radiation
Thermal radiation becomes increasingly important as temperature rises.
Infrared opacifiers within the insulation absorb and scatter this radiant energy. Less radiation passes through the material towards the shell.
These three effects work together to create strong thermal resistance within a compact thickness.
How Can a Thin Layer Provide Strong Insulation?
Thermal resistance depends on two main factors:
Thermal resistance = material thickness ÷ thermal conductivity
A thicker layer normally provides more resistance.
However, a material with much lower thermal conductivity can provide high resistance even when its thickness is limited.
This is why insulation materials should not be compared by thickness alone.
The thermal conductivity must be compared at a representative mean temperature. Temperature limits, shrinkage, compression strength and installation conditions must also be considered.
For example, a microporous grade with a thermal conductivity of 0.048 W/m·K at a mean temperature of 400°C can provide substantially more resistance per millimetre than many conventional backup boards.
What Changes When Microporous Insulation Is Added?
A correctly selected microporous layer changes the temperature profile across the complete lining.
More of the temperature drop occurs within the backup insulation. Less heat reaches the steel casing.
More heat remains inside the equipment
Heat that would otherwise travel through the shell remains available within the process.
In ladles and tundishes, this supports metal-temperature retention during holding, transfer and casting.
In furnaces and kilns, it allows more of the supplied energy to remain in the heated chamber.
The external shell operates at a lower temperature
Reducing the heat reaching the shell can lower the external surface temperature.
This helps reduce thermal exposure around the equipment and limits the temperature load placed on the steel structure.
The lining can remain compact
Increasing conventional insulation thickness is not always possible.
A thicker lining may reduce internal volume, interfere with anchors or require structural changes.
Microporous insulation improves thermal resistance without necessarily increasing the overall lining envelope.
The process becomes more thermally stable
A stronger thermal barrier slows the movement of heat through the lining.
This can reduce rapid temperature changes at the shell side and support more consistent operating conditions.
Same Lining Space, Stronger Thermal Control
In a calculated steel-ladle lining comparison, 13 mm ceramic-fibre board was replaced with 10 mm of LadlePro™ microporous insulation.
The complete lining remained 295 mm thick.
The calculated shell temperature decreased by 35°C, while heat loss through the shell fell by 23.2%.
The comparison demonstrates an important design principle.
The thermal performance of a lining can be improved by upgrading the backup material rather than increasing the total wall thickness.
This approach is useful in ladles where internal capacity, refractory configuration and shell dimensions need to remain unchanged.
Microporous Insulation Compared With Calcium Silicate
Calcium silicate boards are widely used as industrial backup insulation.
However, where space is restricted or lower thermal conductivity is required, microporous insulation can provide more thermal resistance within a thinner section.
In one defined furnace comparison, 65–85 mm of microporous insulation was compared with 115 mm of calcium silicate board.
The microporous system produced an approximately 20°C lower shell temperature. Calculated heat loss decreased by 66% for the stated lining and operating conditions.
These results should not be applied as a fixed percentage to every furnace.
The actual improvement depends on the existing refractory, operating temperature, available thickness, surface conditions and installation quality.
The comparison shows why thermal conductivity and complete lining design matter more than board thickness alone.
Where Is Microporous Insulation Used?
Microporous insulation is suited to high-temperature equipment where space and thermal control are both important.
| Application | Typical installation position | Main design requirement |
|---|---|---|
| Steel ladles | Behind the permanent or safety lining | Retain metal temperature within a fixed lining space |
| Torpedo ladles | Between refractory and steel shell | Control shell temperature during metal transport |
| Tundishes | Behind the refractory lining | Support temperature consistency during casting |
| Electric arc furnaces | Behind compatible refractory-lined zones | Restrict heat conducted towards the shell |
| Industrial furnaces | Between refractory and casing | Improve wall insulation without a major rebuild |
| Kilns and calciners | Behind brick or castable lining | Reduce thermal load on the shell |
| Heat-treatment equipment | Behind the hot-face system | Create a compact and responsive lining |
Microporous insulation is normally used as backup insulation.
It does not replace the working refractory that protects the equipment from process contact, chemical attack and wear.
Selecting the Right Format
The insulation format should match the equipment geometry and installation method.
Rigid boards
Rigid boards are suitable for flat or gently curved sections.
They provide a stable thickness and can be cut to fit around equipment details.
Flexible panels and quilts
Flexible formats follow curved shells more closely.
They are useful for ladles, cylindrical furnaces, pipes and areas where rigid boards would create open joints.
Custom shapes
Machined and formed components can be produced for doors, burner blocks, penetrations and complex geometries.
Custom parts help maintain insulation continuity around areas that are difficult to cover with standard boards.
What Should Be Checked Before Selection?
Microporous insulation should be selected as part of the complete refractory design.
The engineering review should include:
- Normal and peak operating temperature
- Expected temperature at the insulation interface
- Existing refractory materials and thicknesses
- Available space for backup insulation
- Target external shell temperature
- Equipment geometry
- Mechanical pressure on the insulation
- Anchors, supports and penetrations
- Moisture exposure
- Furnace heating and cooling cycle
A thermal calculation can then estimate the temperature at every material interface.
This confirms whether the insulation grade is suitable and whether other lining materials will remain within their approved temperature limits.
Installation Quality Is Part of Thermal Performance
Even a high-performance insulation material can lose effectiveness if it is installed with gaps.
The layer should form a continuous thermal barrier between the refractory system and steel shell.
Keep joints close
Boards and panels should meet with tight, controlled joints.
Open spaces create direct paths for heat to bypass the insulation.
Fit around anchors carefully
Anchors and penetrations can act as thermal bridges.
The material should be cut accurately around these components without leaving unnecessary openings.
Avoid excessive compression
The insulation must be held securely without being crushed.
Over-compression can reduce the installed thickness and damage the material structure.
Protect the panels during refractory work
Microporous boards should not be punctured or broken while the next lining layer is installed.
Damaged sections should be replaced before the lining is closed.
Select moisture protection where required
Wrapped or hydrophobic formats may be needed where the insulation could be exposed to moisture during storage, installation or operation.
The selected protection must remain compatible with the lining and heat-up procedure.
How Should Performance Be Verified?
The improvement should be measured under comparable operating conditions.
Shell thermography is one of the most useful verification methods. It can show changes in surface temperature and identify areas where joints, anchors or damaged insulation are affecting performance.
Other useful measurements include:
- Contact temperature readings at fixed shell locations
- Heat-flux calculations
- Process temperature drop
- Fuel or electrical consumption
- Heating and holding time
- Refractory campaign records
The equipment load, process temperature and operating stage should be recorded with each measurement.
This makes it possible to separate the effect of the insulation from normal changes in production.
Frequently Asked Questions
Is microporous insulation the same as ceramic-fibre insulation?
No.
Both are used for high-temperature insulation, but their structures, thermal conductivity, density, flexibility and installation requirements are different.
The correct material depends on the application and available lining space.
Can microporous insulation replace ceramic-fibre board?
Yes, in suitable backup applications.
The replacement thickness should be confirmed through a thermal calculation and application review.
Can it be installed directly against the steel shell?
In many backup-insulation systems, the microporous layer is positioned close to or directly against the shell.
The final position depends on the complete lining design, attachment method and equipment conditions.
Does the thinnest panel always provide enough insulation?
No.
The required thickness depends on operating temperature, refractory construction, shell-temperature target and thermal bridges.
The thinnest available product should not be selected without checking the full thermal profile.
Can microporous insulation be used as the working lining?
It is generally designed as backup insulation.
A compatible refractory is still required to resist direct process contact, erosion, molten material and chemical attack.
Improve the Lining, Not Its Size
Microporous insulation provides a practical way to improve thermal performance when conventional backup materials require too much space.
Its low thermal conductivity allows a thin layer to control heat movement between the refractory system and the steel shell.
The final solution should be based on the existing lining profile, operating temperature, equipment geometry and required shell condition.
Share your lining drawing, material thicknesses, operating temperature and shell-temperature data with Lanexis for an application-specific thermal review.
