DONALDSON MEMBRANES ELIMINATES CMC EMISSIONS AT MAJOR CHEMICAL PLANT 1

The plant carries out a CMC milling process whereby a derivative of cellulose is formed by its reaction with alkali and chloroacetic acid. The cellulose is then used as a raw material and after several process phases it creates CMC grains, which are then pulverised into many particle sizes depending upon the end user’s requirements.

The resulting material is a colourless, odourless, non-toxic, water soluble powder or granules with a PH of 6.5 to 8.0, used in: detergents; soaps; food products (often diet foods and ice-cream); wallpaper adhesives; emulsion paints; pharmaceuticals and cosmetics.

During this process, following the pulverising stage at the mill, the product power is pre-separated by a cyclone filtration system, with centrifugal forces throwing the CMC dust particles to the outside of a swirling air stream and an overflow comprising the smallest particles gathering in a fabric filter collector.

It was at the fabric filter stage of the process that dust emission levels reached 150mg/nm3, which meant that significant amounts of the valuable CMC dust were being lost, which not only was expensive in terms of product loss but was also causing pollution to the environment.

The company asked Donaldson Membranes to carry out an inspection of the filter process, initially to ascertain the source of dust emission, by use of UV light and fluorescent powder. No leakage was detected from the filter unit housing and on further investigation it was shown that dust was able to permeate through the filter media that was employed in the unit.

Donaldson Membranes recommended replacement of the current filter media with Tetratex #6273 Polyester/epitropic antistatic needlefelt, supplied through a partner, an expert in filter bag manufacture and powder process technology.

Upon installation emissions dropped to less than 3mg/nm3 – a huge improvement upon the previous figure of 150mg/nm3 - and an acceptable and stable pressure was maintained.

Adam Rigby, sales Manager for Donaldson Membranes said: “ For the customer, this represents increased production and profit, whilst ensuring a pollution-free working and living environment. The CMC Plant Manager is extremely satisfied and we are pleased to provide such a successful solution to the problem.”

With emissions of pollutants into the environment and the workplace subject to ever more stringent legislative control, dust and fumes, toxic or not, must be removed. In addition, the solid particulate carried in the gas or liquid flow often represents a useful or valuable product, which must be efficiently separated or filtered for final use or further processing. For applications employing fabric filter media, the best available control technology for the capture of fine and difficult particulate is recognised as ePTFE membranes.

Donaldson Membrane’s Tetratex® Microporous ePTFE membrane filter media has a proven track record as a very high efficiency, highly effective fabric filter media, with several different membrane types available to achieve, subject to various parameters, the desired performance: Tetratex Release, Tetratex, Tetratex High Efficiency and Tetratex Ultra High Efficiency. These high performance laminates provide low pressure drop, higher air flow, and high efficiency, whilst delivering the highest particulate capture rates, unrivalled dust cake release, extended filter bag life and energy savings.