- The Filtration Society - http://www.filtsoc.org -

Volume 13, Issue 4

PURIFICATION OF CRUDE BIODIESEL USING POLYMERIC COMMERCIAL MEMBRANES
Magno José Alves, Suellen Mendonça Nascimento, Iara Gomes Pereira, Vicelma Luiz Cardoso and Miria Hespanhol Miranda Rei (pages 216-221)

The water washing step is a concern in biodiesel production, since it uses large quantities of clean water and generates wastewater to be treated. This paper proposes the application of a microfiltration process to purify crude biodiesel. The crude biodiesel was microfiltered in a deadend process at 1 and 2 bar trans-membrane pressure and with a membrane of 0.22 μm pore size. Observed permeate fluxes showed that there was a pronounced flux decline during the first 2 mins. of filtration. The stabilised flux was greater at 2 bar than at 1 bar, showing that a greater trans-membrane pressure enables greater fluxes. Density, viscosity and the acid value of water washed and permeate biodiesel samples were in accordance with international legislation.

Both water washing and membrane separation processes were able to reduce the amount of soap detected in the crude biodiesel. However, the proposed membrane process was not as efficient as the water washing method in reducing free glycerol content in the crude biodiesel. Especially at the highest applied pressure (2 bar), the permeate obtained was not in accordance with the legislation for free glycerol content (<0.02 wt%). The obtained results showed that the membrane process can be a suitable process for biodiesel purification. However, more specific pore size and material must be analysed in order to achieve the desired level for free glycerol content.

INFLUENCE OF WINDING PARAMETERS ON THE PERFORMANCE OF STRING WOUND FILTER CARTRIDGES – PART I
Pragnya S. Kanade and Someshwar S. Bhattacharya (pages 222-231)

Out of the many disposable filters options available, string wound cartridges/candle filters account for a significant proportion in terms of their application. Wound cartridges are produced by laying a yarn spirally around a perforated core, however, relatively little has been reported on the effect of winding parameters (such as wind ratio, yarn tension, gain etc.) on their performance. Apart from winding variables, the yarn properties, fibre fineness and testing parameters like flow rate and slurry concentration, play a deciding role in filtration behaviour.

This paper reports how wound cartridges have been produced on a newly developed filter winder with electronic controls and their performance assessed on a prototype single pass test rig. Both of these have been developed by the authors. Water or aqueous suspensions of standard test dusts were used as challenge media and comparisons between the cartridges produced on the newly developed winder and a commercial filter winder are reported. Validation tests were performed under the same test conditions. The analysis of filtrate samples was carried out to evaluate the performance of cartridges that had been formed using different winding variables.

PVSC SEWERAGE SLUDGE FILTER PRESS REHABILITATION PROJECT
Ernest Mayer, Sheldon S. Lipke, Marques D. Eley and P. Scholtyssek (pages 237-247)

Passaic Valley Sewerage Commissioners (PVSC) have experienced some sludge dewatering problems with their five ductile iron (DI) plate standard recess presses over the past 10 years. These problems are mainly associated with long dewatering cycles, filter plate scaling, press cloth blinding, and the lack of suitable lab tests for predicting performance. This paper will address these issues, provide some suitable lab test procedures, and suggest future press modifications for improved performance.

NEW CROSSFLOW FILTER MODULE DESIGN PARAMETERS: A THEORETICAL ANALYSIS OF CROSSFLOW FILTER PERFORMANCE LIMITS
Nicos H. Andreas and Christopher L. Cox (pages 247-256)

Exact analytical solutions for the pressure and flow distributions for a cylindrical crossflow filter operating at steady state laminar flow conditions are presented. New characteristic parameters and dimensionless groups that emerge from analysis of the solutions are identified and their significance demonstrated. The solutions obtained are valid only for zero fouling and quantify a performance envelope that can never be exceeded by any real crossflow filter. Two new dimensionless numbers that determine solution trends and are useful in scale up and generalization of empirical data are also identified.

Analysis is used to quantify the interdependence between the model parameters and to determine limiting values, such as a maximum crossflow filter tube length that may not be exceeded in order for solutions to be physically meaningful. The model also provides a theoretical prediction of the minimum surface area required to achieve a design average permeate flux, and can be used to design meaningful experiments and to extract model parameters from empirical measurements. The mathematical model developed and the solutions obtained can serve as a sure foundation for the rational and systematic addition of incremental complexities, e.g. variable viscosity, media fouling and cake build-up inside the tubes. Despite the simplicity of the model used it is shown that the solutions obtained provide useful tools for designers and operators of crossflow filters.