DEECOM™

Historically, after first use all filter elements include an amount of deep-seated, immovable contamination that increases throughout the elements’ lifetime. Filter elements are usually validated using a mass-weight measurement (known as the Benchmark Weight) that shows the amount of residual, immovable contaminant following a cleaning process. As this amount increases some users have determined limits at which their filters are considered to have reached the end of their useful life i.e. they contain too much contaminant to produce a good quality product at the desired rate.

The lifetime of a filter is often projected when filters are new in the form of expected number of cleans or overall throughput. When the preset limit is reached the filters are disposed of and replaced with new elements. 

Trials have shown that filter elements which have been regularly cleaned using TEG solvent processes and have subsequently been rejected, having reached the end of their useful life, can be re-claimed by the DEECOM™ process to a state at which they can be returned to service in a polymer line.

A large number of disc filter stacks from a large film manufacturer have been repeatedly processed using DEECOM™. These stacks are traditionally un-drained and plugged with between 5kg and 20kg of frozen PET.

The high quality nature of PET film product demands that the cleaning of the filter equipment is meticulous to avoid inclusions in product that can lead to large amounts of scrap or even the rejection of entire batches.

The original aim of DEECOM™ was to find an alternative to TEG solvent use. However the development program made clear that not only was the process capable of successfully replacing high temperature solvents but also reducing or removing the requirement for supplementary cleaning steps such as ultrasonic tanking and chemical washing.

Trials on filter stacks of up to 96 discs have repeatedly showed that benchmark validation results were attained after a single DEECOM™ process only.

Trials have been carried out on a pilot sized filter from an elastomer plant and found to be successful. After a six-hour cleaning process the bubble point and mass validation tests were passed with results equal to those of TEG cleaning. The mechanism of degradation is such that no hazardous by-products are created.

The majority of DEECOM™ processes have been carried out on full-scale candle element filter bundles. A feature of the on-line operation of these bundles is a pressure surge when they are returned to station after cleaning. This surge is thought to correspond with the displacement of residual, lightweight, inert contamination from the filter media when high online pressures are reached. The level of displaced contamination is unpredictable and surges of differing size occur.

Pressure surges of this type are widely experienced in the polymer manufacture industry and have long been accepted as an inevitable effect of the filtration process. As a result, polymer process lines can expect, immediately following installation of a cleaned filter bundle, a period when lower quality product is produced. This material is often scrapped or it may be sold at a reduced rate as second grade product.

Filter stacks cleaned using the DEECOM™ system have shown significantly reduced levels of surges when returned to polymer lines. Consequently, full-quality production can resume sooner than has been possible using alternative cleaning methods, i.e. higher levels of saleable polymer can be produced more quickly.