PRESERVING OUR VITAL RESOURCE
Graham Rideal (pages 26-31)
Discussion of our dependence on clean water, some of the steps we need to take to ensure its availability and the impact of new filtration techniques.
EFFECTS OF POST-COATING BY GENERATING A THIN SECONDARY PARTICLE LAYER ON SURFACE FILTERS FOR DUST SEPARATION
Qian Zhang and Eberhard Schmidt (pages 31-37)
Periodic cleaning is necessary in surface filtration to limit the pressure drop, which increases as more dust is deposited. Higher cleaning efficiency can be achieved with lower adhesion of the dust cake on the substrate on the one hand and higher cohesion in the dust cake on the other. The operational behaviour of surface filters can be influenced positively by raw gas conditioning, e.g. by dosing of additives. This paper introduces experimental investigations into the effects of the so called post-coat filtration, which is a novel conditioning concept for surface filtration. An additional thin particle layer is generated by filtration of aerosols on the main dust cake before cake discharge is done. Experiments were performed with needlefelts as the test filters, limestone as the main dust and carnauba wax or sodium chloride as the post-coat particles on a surface filter test apparatus (manufactured according to VDI guideline 3926-1). The effects observed in single filtration cycles are presented and discussed.
SOFTWARE FOR STATISTICAL DESIGN OF EXPERIMENTS AND EMPIRICAL MODELLING OF CAKE FILTRATION
Mikko Huhtanen, Antti Häkkinen, Bjarne Ekberg and J. Kallas (pages 38-49)
This paper introduces software developed to improve the efficiency and quality of typical test filtration tasks and to simplify and rationalize the interpretation of test results. The software consists of two different modules.
The first module creates experimental designs according to initial information provided by the user. The test designs are created by applying the basic principles of factorial designs in such a way that the variations in the investigated ranges of the desired process variables are taken into account systematically. The utilization of different kinds of factorial designs also means that the amount of experiments needed to achieve the required accuracy can be minimized. The second module of the software analyses the experimental results by utilizing standard multivariate data analysis techniques. The meaningful information from a given table of experimental data is extracted and used to create regression models that quantify the relationships between the studied process variables. These models can be further applied to predict new values, for visualizing the relationships between the different variables, or for selecting the variable combinations in order to reach the predefined process objectives.
The current software is capable of creating experimental designs for five different kinds of filters, namely the automatic vertical pressure filter, double-sided automatic vertical pressure filter, horizontal membrane filter press, horizontal vacuum belt filter, and the ceramic capillary action vacuum disc filter. The suitability of the applied techniques for each filter type has also been verified by performing a large number of experiments. Some of the experimental results with the automatic vertical pressure filter are presented in this paper to illustrate the procedure developed and also to demonstrate the quality of the final results obtained by the applied methods.
ROTATIONAL PARTICLE SEPARATOR: AN EFFICIENT METHOD TO SEPARATE MICRON-SIZED DROPLETS AND PARTICLES FROM FLUIDS
J.J.H. Brouwers, H.P. van Kemenade and J.P. Kroes (pages 49-60)
The rotational particle separator (RPS) has a cyclone type housing within which a rotating cylinder is placed. The rotating cylinder is an assembly of a large number of axially oriented channels, e.g. small diameter pipes. Micron-sized particles entrained in the fluid flowing through the channels are centrifuged towards the walls of the channels. Here they form a layer or film of particles, material which is removed by applying pressure pulses or by flowing of the film itself. Compared to conventional cyclones the RPS is an order of magnitude smaller in size at equal separation performance, while at equal size it separates particles ten times smaller. Applications of the RPS considered are ash removal from hot flue gases in small scale combustion installations, product recovery in the stainless environment for pharmaceutical/food, oil water separation and demisting of gases. Elementary formulae for separation performance are presented and compared with measurements performed with various RPS designs.
DEVELOPMENT OF INNOVATIVE FIBRE MATERIALS FOR TECHNICAL APPLICATIONS – FINE POLYVINYLIDENE FLUORIDE FILAMENTS AND FABRICS
Stephan Walter, Wilhelm Steinmann, Gunnar Seide, Thomas Gries and Georg Roth (pages 60-64)
Development of new materials and processes for technical applications usually requires extensive interdisciplinary cooperation. It is seldom that innovative and sophisticated materials evolve solely from one technical or scientific discipline’s efforts. In this paper the development of fine melt spun polyvinylidene fluoride multifilament yarns, the processing, fabric production and property investigation are presented. It outlines what it takes to exceed the state-of-the-art for existing fibre materials and their applications. The steps of material selection, experimental evaluation of a process window for melt spinning PVDF, yarn processing and fabric formation are reported in detail. Furthermore, a model for the crystalline structure formation during melt spinning and drawing PVDF fibres is presented.