Technology

Adsorbent hollow fibres

nano-porous solutions limited specialise in the development and manufacture of adsorbent hollow fibres, which are customized to meet the requirements of specific applications. The adsorbents that are used within the novel fibre structure are commercially available and some are currently in a granular form (beads), while many others are more specialized.

Hollow fibre structure

The hollow fibre structure presents the adsorbent materials within a polymer support structure which makes the crystals more accessible, as compared with the beads. As can be seen from figure 1, the adsorbent hollow fibre has a very open, porous structure. During the manufacturing process, the polymer is redistributed, leaving the adsorbent crystals clear and accessible (see figure 2).

	Fig. 1 – Scanning electron microscope image (SEM) – cross section of fibre wall (approx 1mm)
	Fig. 2 – SEM image showing adsorbent crystals within the fibre structure

With beaded construction, the adsorbent is combined with a clay binder which is then formed into spheres of various diameters. As can be seen from figure 3, the surface of the bead is quite dense and certainly not as porous / open as the fibre. A closer look at the surface of the bead shows that the clay binder is covering the crystals – effectively blocking the sites for adsorption (see figure 4).

	Fig. 3 – SEM image – commercial adsorbent bead (approx 3mm in diameter)
	Fig. 4 – SEM image – surface of bead / adsorbent crystals blocked with clay binder

Advantages

Low mass transfer resistence
The porous, open nature of the fibre allows contaminants to move easily into the structure. Low mass transfer resistance is important for all applications, but is particularly helpful for applications where the pressures are low (< 5 bar) or even atmospheric.

Improved kinetics
The open structure and clear adsorption sites allow contaminants to move in to and out of the structure very rapidly, making the fibres extremely efficient filtration devices.

Fast regeneration
With the good kinetics, fibres can be regenerated quickly and efficiently using pressure swing, thermal swing or vacuum swing techniques.

Compact design
For dynamic applications (such as pressure swing adsorption) the fast regeneration will enable the adsorbent bed to be significantly reduced in size.

Low pressure drop
Pressure drop through hollow fibre modules is negligible - it has been measured at 1/100th of the equivalent packed bed of beaded adsorbent.

Install in any orientation
- For granular filled packed beds to work effectively, they must be installed vertically, to avoid by-pass and breakthrough of the contaminant. The fibre modules can be installed in any orientation.

Custom made fibres
Fibres can be formulated and manufactured according to the application requirements. Single or multiple adsorbents can be incorporated into the fibre structure to remove target contaminants, simultaneously.

No special filling techniques required
With granular adsorbents, special filling techniques must be adopted to ensure that the "bed" is tightly packed with minimal gaps. Adsorbent hollow fibres are tightly packed into a module, leaving no gaps - therefore eliminating all of these concerns, making it simple for customers to handle and exchange in the field.

Current range of adsorbent hollow fibres
nano-porous solutions limited has developed fibres to remove a range of contaminants including:-

• Hydrocarbons
  
• Water
  
• Volatile organic compounds
  
• Carbon dioxide