FILTRATION (Volume 16 Number 4) is the official journal of The Filtration Society and the American Filtration & Separations Society.
David Chezaud; Scientific Director and Founder; FlowerSEP, Village d’Entreprises Lasserre 47310 Estillac, France.
This paper describes some of the features of new equipment for laboratory scale filtration testing. Descriptions are provided for the Filtration Performance Test, which facilitates the automated acquisition of constant pressure filtration data, and Filtration Performance Software which facilitates data analysis, including the automated calculation of characterising parameters such as specific cake resistance and cake compressibility. Exemplar experimental data are presented to show equipment/analysis performance in relation to repeatability measurements, filtration cell diameter, particle diameter and particle shape. The use of the approach to aid process scale equipment specification is also considered and some examples are given.
INTRODUCTION
The Filtration Performance Test is a tool for precisely analysing how a suspension behaves during filtration over a wide range of experimental conditions to ensure the best filtration possible; experimental variables include filtration pressure, deliquoring pressure and the chosen filter media. Achieving such precision has required several years of development including numerical simulation, trial comparisons, ergonomic studies with a designer and user feedback. The result is a product that is patented all over the world. The aim of the Filtration Performance Test is to, in just a few minutes, assess product filterability in order to:
• increase the productivity of an industrial processes
• anticipate the variability of a valuable product
• amortise more quickly the investment on equipment.
With reference to Figure 1, a simple and secure agitated tank was specially designed and its protection ensured by an anti-projection receptor. The human machine interface (HMI) fitted to the FPTLab has been designed to be intuitive, all the trial information is traceable and libraries of products can be created. Filtration tests can follow quickly one after another, with or without deliquoring, the only requirement being to connect-click a new filtration cell. The HMI screen allows:
• all traceability parameters to be entered
• live plotting of t/V = f(V)
• determination of filtration resistance, including a colour coding system for filterability
• calculation of the correlation coefficient
• immediate production of a filtration report
• data back-up from trials.
Post processing via the specially developed Filtration Performance Software allows:
• import of trial data
• production of personalized filtration reports
• cake compressibility determination
• objective and comparative analysis
• standardised filterability report.
GENERAL ASPECTS OF THE FILTRATION PERFORMANCE TEST LAB (FPTLab)
The FPTLab (Figure 1) allows the quick measurement of filtration parameters such as cake specific resistance and compressibility. Its operation is based on the integrated form of Darcy’s law at constant pressure which shows the relationship between filtration time and volume of filtrate collected according to equation… download article FILTRATION (Volume 16 Number 4)
REPEATABILITY MEASUREMENTS FOR SPECIFIC CAKE RESISTANCE
This section presents exemplar repeatability tests for the FPTLab with 6 µm diameter calcium carbonate spheres dispersed in water. Here, five different trials were carried out at an applied pressure of 3 bar using a 3 cm diameter filtration cell. The trials were compared in terms of calculated specific cake resistance and a statistical analysis was performed. Figure 3 shows that the results are within the 95% confidence interval (shown in blue) and hence the measurement of specific cake resistance is considered to be repeatable… download article FILTRATION (Volume 16 Number 4)
INFLUENCE OF CELL DIAMETER ON SPECIFIC CAKE RESISTANCE
This section presents a study of the influence of filter cell diameter on specific cake resistance. The trials were again carried out on the FPTLab equipment with calcium carbonate spheres. In each case five different trials were performed at an applied pressure of 3 bar using two different cells of 1 cm and 3 cm diameter, respectively. Statistical tests with a 95% confidence interval were done on the calculated specific cake resistances and these showed that the mean values for both cells are not significantly different (see Table 2). Hence, wall effects can be neglected and it is concluded that measurements with the 1 cm cell are representative of those with the 3 cm cell, and the reduction of diameter is validated… download article FILTRATION (Volume 16 Number 4)
INFLUENCE OF PARTICLE DIAMETER ON SPECIFIC CAKE RESISTANCE AND COMPRESSIBILITY
This section presents measurements for the influence of particle diameter on specific cake resistance and compressibility coefficient. The trials were again carried out using the FPTLab, in this case with 20 µm and a 50 µm calibrated spheres of poly methyl methacrylate (PMMA, see Figure 4) dispersed in water. For each particle size three different trials were done at 1, 3 and 5 bar applied pressure using the 1 cm diameter filtration cell. The results are shown in Table 3… download article FILTRATION (Volume 16 Number 4)
INFLUENCE OF PARTICLE SHAPE ON CAKE SPECIFIC RESISTANCE AND COMPRESSIBILITY
This section illustrates the effects of particle shape on specific cake resistance and compressibility. Two types of particles in aqueous suspension were used in the FPTLab, namely 20 µm diameter PMMA spheres (Figure 4) and 20 µm diameter calcium carbonate needles (Figure 5). For each shape, three different trials at 1, 3 and 5 bar applied pressure were performed with a 1 cm diameter filtration cell. Table 4 shows the results… download article FILTRATION (Volume 16 Number 4)
FURTHER USES OF THE FILTRATION PERFORMANCE TEST
In addition to the range of tests described above, the results from the Filtration Performance Test, e.g. specific cake resistance and compressibility coefficient measurements, can be used to aid the choice of solid-liquid separation device at the process scale. Figure 6 is an exemplar chart which indicates how the data obtained from the FPTLab is related to the typical requirements of some filter and centrifuge types; the Laminar Flow CS is a centrifugal separator that was jointly developed between FlowerSEP and the Atomic Energy Committee (Nuclear Energy Direction)… download article FILTRATION (Volume 16 Number 4)
APPLICATION OF THE PROCESS DESCRIBED
download article FILTRATION (Volume 16 Number 4)
CONCLUSIONS
The Filtration Performance Test repeatability and the use of a 1 cm diameter cell were validated by means of a range of experiments with the FPTLab. Different measurement possibilities were shown. The FPTLab is a new device that allows a quick and reliable measurement of specific cake resistance and cake compressibility coefficient. Knowing these parameters can guide a choice of industrial equipment or predict the impact of product variability on the whole process. Use of the FTPLab also allows the prediction of bottlenecks in an industrial process. For research and development units, it allows an optimization of operating pressures for the solid-liquid separation step. More over with the cell of filtration ‘clik’ and connect, you can quickly select the filtration media adapted to your needs.
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