High Temperature Filter Assembly with Geopolymer Sealant
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Solution Overview
Problem
High-temperature air filters face challenges in maintaining structural rigidity and filtering efficiency due to thermal expansion, poor adhesion, and mechanical stress, leading to air leakage and reduced performance over extended periods, especially when cycling between low and high temperatures.
Innovation Solution
A high-efficiency air filter assembly using a binder-free glass or mineral fiber filter media embedded in a solid inorganic geopolymer sealant composition, with a compressible heat-resistant fibrous material and flexible liner to prevent mechanical stress and ensure a resilient seal, within a stainless steel frame that can expand without damaging the sealant.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a resilient mat of glass fibers is compressed between the filter core and frame to provide sealing, then sealing capability is improved, but after prolonged exposure to high temperatures the glass fibers anneal and lose resiliency causing air leakage
Solution Approach 1:
The patent changes the material parameters by replacing organic binders with inorganic geopolymer sealant composition, enabling the sealant to maintain its sealing properties at high temperatures up to 500°C without the annealing problem that affects glass fiber mats
Solution Approach 2:
The patent uses a composite sealing system combining geopolymer sealant composition with heat-resistant fibrous material (such as alumina fibers or ceramic fibers) to create a sealant that maintains resiliency and sealing capability at high temperatures, overcoming the limitations of pure glass fiber mats
2Reliability
If ceramic adhesive is applied with a trowel to seal the filter assembly, then sealing is achieved, but uniform sealant depth and uniformity are difficult to obtain leading to leakages or blockage
Solution Approach 1:
The patent replaces the manual mechanical troweling process with an immersion method where the filter core is submerged in liquid geopolymer sealant, automatically achieving uniform sealant depth and distribution without manual intervention or complex tooling
Solution Approach 2:
The immersion method allows the sealant to automatically distribute itself uniformly across the filter core surfaces through capillary action and gravity, eliminating the need for precise manual application and achieving consistent sealing quality
3Adaptability or versatility
If the filter assembly is subjected to repeated cycling between low and high temperatures, then operational flexibility is improved, but thermal expansion differences cause separation and air leakage between sealers and frame members
Solution Approach 1:
The patent accounts for thermal expansion by selecting materials with compatible expansion coefficients and designing the sealant system to accommodate dimensional changes during temperature cycling, preventing separation and maintaining sealing integrity
Solution Approach 2:
The geopolymer sealant combined with heat-resistant fibrous material creates a composite that has both high-temperature stability and flexibility to accommodate thermal expansion differences between dissimilar materials during temperature cycling
4Strength
If adhesive is used to bond filter components, then structural strength is improved, but the adhesive powdering or crumbles at high temperatures
Solution Approach 1:
The patent fundamentally changes the chemical composition of the bonding agent from organic adhesive to inorganic geopolymer sealant, which maintains bond strength and structural integrity at high temperatures up to 500°C without powdering or crumbling
Solution Approach 2:
The patent eliminates the need for separate adhesive layers by using the geopolymer sealant composition to perform both sealing and bonding functions simultaneously, simplifying the structure and improving high-temperature performance
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The assembly maintains HEPA class H13 or higher efficiency and structural integrity over extended periods at temperatures ranging from 25°C to 500°C, reducing air leakage and requiring minimal burn-in, suitable for high-temperature applications like pharmaceutical processing.
Implementation Method 1
providing a resilient seal between the filter core and the frame which is capable of accommodating expansion of the frame upon heating
Implementation Method 2
a compressible heat-resistant fibrous material... providing a resilient seal between the filter core and the frame
Data Source
Figure 1a
Figure 1b
Figure 2
AI summary
A high efficiency air filter assembly (100) for high temperature applications comprising: a filter core (102) including a unitary sheet of air-permeable filter media folded in accordion fashion to form a plurality of side-by-side pleats with zig-zag edges on two opposite sides and flat panels on the other two sides, and a spacer member between opposing walls of successive pleats, a box-like metal frame (108) enclosing said filter core on four sides in air tight engagement to define an air flow opening extending between upstream and downstream sides of said assembly, wherein the zig-zag edges of the unitary sheet of air-permeable filter media are sealingly embedded in a solid inorganic sealant composition (118) in the frame, and wherein the unitary sheet of air-permeable filter media preferably consists of a binder-free glass or mineral fiber filter media. Use of the high efficiency air filter assembly in high temperature applications wherein the filter assembly is repeatedly or continuously heated to a temperature in the range of 200-500 °C.