 The production of carboxy methyl cellulose (CMC) involves an alkali hydrolysis of a cellulosic feedstock followed by carboxylation. This causes the formation of sodium chloride which has to be washed out of the CMC before it can be further processed. Unfortunately this is not so simple, as CMC is soluble in water, so it has to be washed with an alcohol/water mixture usually with a minimum of 60% alcohol. There are three main grades of CMC, technical or crude CMC, purified and food grade. Food grade requires better than 99.8% pure CMC.
Multiple wash stages are required in a counter-current sequence to achieve the varying purity levels. The wash ratios utilized together with the high alcohol content, to stabilize the CMC in the presence of water, require counter current washing to keep the process economically feasible. Traditionally the CMC production was ran on series of up to 6 centrifuges, set up in counter-current mode but over the last 20 years the Pannevis GT filter has become the equipment of choice as it is possible to carry out from 3 up to 8 or more counter-current wash steps in a single unit under a sealed, re-circulatory nitrogen atmosphere. Pannevis GT filters easily achieve the purity requirements of all three grades, including the food grade.
The Pannevis GT filter offers all the advantages of the standard Pannevis RT filter including the capability to carry out multiple step counter-current washing. The filter housing is normally operated with a slight internal over-pressure using nitrogen, which is continuously re-circulated around the filter circuit so that all components including filtrate receivers and pumps are totally inert. A very small make-up of nitrogen is required to compensate for the gas exiting with the filter cake.
Large windows in the sidewalls and lights on the roof ensure complete visibility of the process inside the housing. The housing is designed to ensuring all internal surfaces are easily cleaned and self draining. Clean-in-place (CIP) is a standard option and the basic design is suitable for sanitary processes as all dead spots are eliminated, windows and nozzles are sloped to drain back into the housing and internal surfaces can easily be polished to any specified level.
As with all of the Pannevis RT based filters, the GT filter is extremely reliable and maintenance is simple. All the major service items including the cloth drive, bearings, pneumatic cylinders and sensors are mounted outside the housing, eliminating both the risk of product contamination and the need to access inside the filter housing for normal scheduled maintenance. Thus the inert integrity of the filter is maintained at all times.
Continuous filter cloth cleaning eliminates cross contamination and guarantees 100% product recovery. Cloth wash liquid can be recycled over the filter cake assuring total solids capture and minimizing the consumption of fresh liquid. Batch identification, when required, is easily achieved by carrying out semi-continuous operation. Full validation procedures to meet all FDA final product requirements are proven and available. When operating with solvent, the filters meet all the requirements of ATEX 95 category 2.
Larox is committed to helping its clients meet the following goals
§ Reduced lifetime production costs – especially energy based costs
§ Improved product quality, value and consistency
§ Improved safety, health and environmental performance | |
