Knitmesh is a regular tower packing made from a crimped mesh of woven wire filaments. Every strand of this mesh is a bunch of a large number of thin filaments. (111 micron size). The package is cylindrical in shape and is made to a size which snugly fits the interior of a distillation column. Due to its high mass transfer efficiency, it is extensively used in laboratories, pilot plants and commercial installations, for distillation, gas-absorption and liquid extraction. To achieve high degree of mass transfer efficiency, an intimate contact between vapour and liquid phases is necessary. Knitmesh made from crimped mesh of woven wire filaments provides large surface to realize the desired interphase mixing.

MECHANISM

Capillary action of the strands of knitmesh helps in spreading the liquid uniformly over the wire mesh. As a result, there is no build-up of the liquid anywhere in the voids of the packing. Vapour therefore has a free access to every surface inside the packing. The high seperation efficiency is thus obtained as the available surface of the packing is most effectively utilized.

SALIENT FEATURES

Low value of HETP (Height Equivalent of Theoretical Plate). Typical values range from 100 to 150 mm. Low values of PDTS (Pressure Drop per Theoretical Stage). Typical values range from 0.04 to 0.05 mm of Hg, depending upon the vapour load.

	High vapour handling capacity: Vapour handling capacity of knitmesh is comparable to 25 mm metal pall rings.
	No reduction in efficiency even at low liquid irrigation rates: Capillary action of knitmesh helps it to achieve uniform wetting of the entire package even at low liquid loadings. Packing can work without loss of efficiency at a liquid irrigation rate as low as 0.3 mh (0.5 GPM/FT)
	Performance is independent of Packing Size : Unlike random packings, the properties of knitmesh are independent of packing size. Hence its performance characteristics such as HETP and PDTS are practically independent of packing diameter.
	No wall effect : Knitmesh draws liquid from the wall of the column into its interior by capillary action. No liquid redistributors are therefore necessary for a column packed with knitmesh.

ADVANTAGES

Advantages gained through use of knitmesh. Although knitmesh appears to be expensive at first sight, it will prove to be the most economical solution to your problem, if you weigh each of its following advantages

	Reduction in packed volume: This is achieved due to low HETP of the packing.
	Reduction in the cost of column shell and supporting structure: This follows as a consequence of lower packed volume.
	Saving in energy cost : This is possible through reduction in the reflux ratio.
	Reduction in product loss through product degradation: Use of knitmesh allows you to achieve reboiler temperature for a specified column top pressure. Lower reboiler temperature reduces the rate of degradation of heat sensitive materials present in the reboiler, resulting in high product yeild.
	High flexibility: Since knitmesh shows high performance over a wide range of liquid loadings, it is most suitable for the situations which demand flexibility, that is batch operations, unsteady state operations and multipurpose distillation jobs.
	Increased in throughput capacity : The wide range of operating velocities allows increase in column capacity 2-2.5 higher than conventional packing.