Stop Press

KnitMesh offers a range of equipment designed to accelerate the separation of either primary or secondary immiscible liquid dispersions. The attached overview shows how dispersions are usually formed and which coalescers are appropriate for the resulting applications.

Primary Dispersions
Originally patented by KnitMesh, the DC Coalescer was developed from a concept invented at the University of Manchester Institute of Science & Technology in the 1960's. The essence of the design is to use a composite of two materials with very different surface free energies - typically metal and plastic. This simple principle offers notable advantages over conventional, single medium alternatives.

The combination of both high and low surface free energies mean effective separation irrespective of which phase is dispersed. Secondly, the rate of coalescence when droplets are captured and meet at the junction points of the two dissimilar materials is significantly increased.

Key Benefits
	Improved separation efficiency
	Higher capacities allow de-bottlenecking of conventional separators
	Large cost savings in pressure vessels
	Efficiency maintained even with phase inversion of dispersed liquid
	High free volume means smaller pressure drop

Secondary Dispersions
In secondary dispersions, the droplets are so small they do not readily wet a surface or settle under gravity - typically 1 to 30µm. In cartridge form with the liquid flowing from the centre radially outwards, the Dusec Coalescer is made up from a selection of fibre materials.

Adhesion forces capture intercepted droplets onto the fibre surface at selective points where clusters form until coalescence takes place and the droplets grow. Viscous drag forces increase until exceeding the adhesion forces which causes the droplets to separate from the fibre and move further into the coalescer fibre bed where the process is repeated.

Eventually the droplets reach primary dispersion size - ie predominantly >60µm. The outer layer of the cartridge is the same composite construction as a KnitMesh DC (primary) coalescer which accelerates separation.

Key Benefits
	Fibre topology and surface property combined with optimised layer compositions mean higher capacities
	Higher loadings and absence of jetting from outer layers mean higher packing densities
	Smaller vessel size means capital cost reduction
	Separation efficiency down to 10 ppm free entrainment
	Pressure drop minimised
	Quick performance recovery following feed condition changes

Mechanical Seal Design
Experience of coalescer duties in hydrogen peroxide production led KnitMesh to develop a new style of cartridge in which a 'mechanically bonded' seal replaces the resins normally used to secure the end caps to the cartridge fibres. The new seals, combined with carefully selected fibres, mean the cartridge can resist even the most aggressive solvents.

Dusec Plus
Designed to achieve high performance with minimum pressure drop, the Dusec Plus model provides a high capacity alternative to conventional Dusec cartridges. The smaller diameter and increased packing density make it suitable for applications where it is necessary to maximise the effective area of the coalescer media in a given size of vessel.

- ends -

Issued on behalf of:
KnitMesh Limited
June 2000

For further information contact:

     LAMC
     45 Saxbys Lane, Lingfield, Surrey RH7 6DP
     England
     Tel: +44 1342 833313   Fax: +44 1342 832864
     E-mail: suemather@btinternet.com