FILTER MEDIA DESIGN AND ITS INFLUENCE ON FILTRATION RESULTS –
POSSIBILITIES TO ENHANCE VACUUM AND PRESSURE FILTRATION
Alexander Seitz and Christoph Maurer (pages 44-51)
The design and characteristics of filter media, such as weave pattern, number of pores, pore shape, pore size, pore size distribution and permeability influence cake formation, cake filtration, particle retention, filter media lifetime as well as the resulting machine efficiency and productivity. In the end, the overall cost of ownership is affected.
By carrying out intensive laboratory analysis, filtration trials and scale-up testing, the influence of filter media design on the final filtration result during vacuum and pressure filtration is investigated and described in this paper. If everything is calculated and implemented thoroughly there can be a substantial contribution to achieving a higher production yield, while obtaining, or even improving, the final product quality. The paper compares the variables and performance criteria that require definition in order to select the most efficient filter media for a given application. An actual example of the guidelines used to judge filter media performance and some of the properties of enhanced future filter media is presented to conclude the paper.
Scalable Double Layer Weave (DLW) filter fabrics for different applications and requirements are presented. Laboratory and field tests illustrate how filtration results are dependent on the selection of appropriate filter media and their specific properties. Improved cake dryness and purity, better cake release, higher production capacity and, in the end, lower process costs result from new filter media design and careful selection.
DEVELOPMENTS IN FILTER MEDIA: INCORPORATING ADDITIONAL
Ian Chisem, David Fogg and Richard Lydon (pages 51-56)
As industry strives for increased levels of efficiency through rigorous process optimisation programmes, filter media suppliers must seek to add value to their products by improving product performance, lifetime, ease-of-use and maximising process up-time. Clear Edge has developed a comprehensive body of practical knowledge in solid-liquid separation together with a strong scientific understanding, using its state-of-the-art laboratories to understand the chemical and structural properties required to maximise performance. By way of illustration, two innovative filter media technologies are described herein.
It has been demonstrated that microporous coated media can improve blinding resistance, enhance throughput and improve filtrate clarity; these properties are mainly attributed to the surface filtration mechanism afforded by the microporous coating which is impregnated both onto and into the base filter media. Additional productivity gains result from increased retention efficiencies. To further enhance the value proposition, this technology can be used in combination with the elastomeric welded barrel neck product line, Coreflo™, which affords ease of cloth fitting with a leak free seal. Combining innovative solutions such as these results in tangible benefits for the customer: to demonstrate this the findings from a number of case studies are presented to prove the measurable added value of these technologies, either alone or used in combination.
INSIGHT INTO THE STICKY PHASE OF ACTIVATED SLUDGE AND ITS
IMPLICATION TO SLUDGE DEWATERING/DRYING OPERATIONS
Bart Peeters and Luc Vernimmen (pages 57-60)
The sticky phase of wastewater sludge poses a persistent challenge when the sludge volume is reduced in industrial dewatering-drying installations. At some intermediate dryness content, during its passage through mechanical dewatering and consecutive thermal drying, the sludge transforms into a rubbery material. This either adheres to the equipment surfaces or further agglomerates into large lumps by cohesion, thereby impeding the proper working of these unit operations. Although insight in the sticky phase of sludge is essential for smooth operations in industry, most literature pertains to research conducted in the context of sludge dewatering and drying as such, rather than to the concomitantly appearing sticky behaviour.
In this paper, we discuss the sticky phase: how it can be mapped, how its existence can be explained and how industry copes with it during daily operations. One strategy to deal with the stickiness, rigorously tested by the authors at lab- and full-scale over the past six years, is the conditioning of the sludge with polyaluminium chloride (PACl) which will be specifically highlighted.