AUTOMATION IN FILTRATION SYSTEMS: HOW TELEMETRY COULD IMPROVE OPERATING MARGINS FOR BOTH SUPPLIER AND OPERATOR
D. Harris (pages 34-37)
The operation of separations equipment can be labour intensive, with high consumables costs. Incorrect operation or equipment malfunction may directly impact process economics. The use of automation at the simplest level may allow better planning of scarce labour resource interventions or avoid unexpected process upsets. More sophisticated automation of the system, in combination with the selection of the right separations technology, may significantly reduce or practically eliminate the need for manual intervention in normal operation.
At the highest level, systems can be augmented with remote monitoring and telemetry, allowing installations to send operating data and requests for assistance to a central location. Through the communications network, alerted engineers can take control of the system from their desk to perform diagnostic investigations, make operational modifications, and determine when there is a requirement for physical intervention. Similar systems may also allow the effective operation of multiple pilot trials in different locations, or even different countries, with a minimum of engineering staff required for support.
Case studies are presented to describe the various approaches taken, and outline some of the cost benefits that may be achieved both by the process owner and by the equipment vendor.
NEW THINKING ON WET MAGNETIC TREATMENT OF FELDSPAR
P. Fears (pages 38-39)
Traditionally, magnetic separation has only been introduced into the processing flow sheet of a feldspar operation at the dry stage, late in the process. Flotation is used to remove most other contaminants. Now, as companies try to reduce their reliance on flotation, wet high intensity magnetic separation is proving to either partially or totally replace the need for flotation.
COMPARISON OF MEMBRANE FILTER PRESSES WITH BELT FILTER PRESSES AND CENTRIFUGEs
E. Mayer(pages 40-49)
Wastewater sludge dewatering is usually accomplished by three devices: solid-bowl decanter centrifuges, belt filter presses, and recessed filter presses (both standard and membrane (or diaphragm)). Of these, the membrane filter press produces the driest cakes (as well as the cleanest filtrate), which is best suited for land application, incineration, or further processing. As a consequence, most wastewater sludge dewatering in Europe utilizes membrane filter presses, while belt filter presses and centrifuges are primarily used in the US because of more landfill space. However, space is becoming limited and more filter presses are being utilized in the US. This paper presents an overview of membrane filter presses, where they have been used, and how they compare to centrifuges and belt filter presses via many case histories for a variety of wastewater sludges.
A NEW METHOD TO DETERMINE the PARTICULATE FILTRATION EFFICIENCY OF SUBMICRON CARTRIDGE FILTERS
C. Peuchot and N. Petillon (pages 50-55)
Submicron cartridge filters are broadly used to clarify, purify or decontaminate many liquids in several industrial fields. Such applications are the processing of ultrapure liquids for making electronic components, the cold sterilisation of wines, bioliquids and pharmaceutical solutes, and the decontamination of industrial solvents and washing liquids. Microfiltration cartridge filters, with ratings below 3 µm, are installed as prefilters and are pleated, agglomerated or wound. The performance and ability to use these prefilters are determined in laboratory conditions according to standard methods adopted by filter makers and large end users. For instance, the rating is determined using water or a mineral oil as the test fluid, ISO MTD according to ISO 12103 as a test powder, and online particle counting with light extinction instruments to count particles at various sizes upstream and downstream of the test filter to calculate its instantaneous efficiency.
Reading technical brochures of submicron filters show they are mainly characterised by their microbial rating (they are regarded as sterilising if they reduce to a given ratio the number of standard microorganisms). Very few brochures state a micron rating based on particle size and when they do, they do not refer to any test method. To answer the need of several large end users, IFTS has developed a new protocol to measure filtration efficiency during the clogging of submicron and microfiltration cartridges. This paper describes the test powder chosen, the test circuit designed, validation results, criteria and typical test results obtained for several cartridges bought on the market.
ON-LINE MONITORING AND OPTIMISATION OF BAGHOUSE FILTER OPERATIONS TO REDUCE OPERATING COSTS AND MINIMISE PARTICULATE EMISSIONS TO AIR
W. Averdieck (pages 55-58)
Operators of many industrial plant have made significant improvements in reducing particulate emissions to air by fitting high performance baghouse dust collectors. Emissions from such processes are highly abated provided the baghouse filter operates to its design condition, and the relevant control issue is to effectively monitor for changes in the condition of the bag filter associated with filter leakage and bag rupture.
ABOUT 20 YEARS OF OPERATION EXPERIENCE OF WASTEWATER FILTRATION IN GERMANY
M. Barjenbruch and T. Rolfs (pages 59-64)
In 1977, the first large-scale wastewater filtration in Germany started operating (in the city of Darsheim). The number of applications stagnated for several years, but at the beginning of the 1990s wastewater filtration units were installed due to the demand for lower effluent values to protect the water bodies. Currently, about 180 wastewater filtration plants in different technical variations are in operation. Most of them were built to observe very low phosphorous concentration values (< 0.5 mg Ptot/L). The German standards of dimensioning and design are summarized in the DWA Working Sheet A 203 (1995) “Wastewater filtration with deep bed filters after biological treatment”. After about 20 years of operation, a great number of experiences have been obtained which are presented in this report, with particular reference to the design and the operation of filtration units planned in future.
OXYGEN ENRICHMENT OF AIR FOR DIESEL ENGINES: A PROCESS EVALUATION STUDY
P. Chitta and B.J. Tatarchuk (pages 66-71)
Supply of oxygen enriched air helps increase reaction conversion rates and efficiencies in various combustion applications such as in diesel engines. This paper discusses the results of sorbent screening. Initially the sorbents are screened based upon nitrogen adsorption and moisture removal capacities at different activation temperatures and adsorption times. This study includes testing of the active zeolites under multiple adsorption-regeneration cycles. The results are presented as N2 and O2 adsorption isotherms. Finally, a comparative study of various cyclic adsorption-desorption processes comprising of pressure swing, temperature swing, temperature aided pressure swing and rapid pressure swing is presented. The adsorption experiments are carried out in a fixed bed reactor and the sorbents consist of molecular sieves and other cation exchanged zeolites that include LiLSX, RE-LiLSX, LiX, NaX, LiCuX, 13X, 3A, 4A and 5A types.
SIMILARITY ANALYSIS OF CONSTANT PRESSURE CAKE FILTRATION
A.K. Gholap, J. Peddieson and S. Munukutla (pages 73-79)
A similarity analysis of constant pressure cake filtration was carried out based on a single set of governing equations applicable to both the cake and slurry regions. A finite difference method was used to obtain numerical solutions for several forms of the effective diffusivity function appearing in the model. A representative set of results is presented graphically. It was found that, while details of the predicted concentration profiles were quite diffusivity function sensitive, certain qualitative features of the predictions were diffusivity function insensitive. This suggests that experimentally observed details of the behaviours of specific slurries can be matched with particular diffusivity functions while preserving qualitative features common to all slurries.
SIMULATION OF LIQUID PHASE ACCUMULATION FOR THE CENTRIFUGAL DEWATERING OF ACTIVATWD SLUDGE
M. Mota, J.A. Teixeira, G.N. Abaev, I. Yelshyna and A. Yelshin(pages 80-86)
Centrifugation of activated sludge is a frequently used dewatering process but, in spite of this, there is a need for a fitting function for moderate and high sludge concentrations. Liquid phase accumulation kinetics during centrifugation may be used as a source of information about the sedimentation properties and the governing mechanism during cake formation. For this purpose, activated sludge at different concentrations was investigated on a laboratory centrifuge with a centrifugation factor of 2667. The following sludges were used in the experiments:
(1) Activated sludge from a thickener (with and without flocculant treatment)
(2) Sludge taken after an industrial centrifuge decanter, treated with Flottweg Z62-4 flocculant and collected from a dumping pound
(3) Sludge (2) after anaerobic treatment
(4) Sludge (2) with a dispersed solid additive.
Using the experimental data for an asymptotical analysis, a dimensionless fitting function was obtained that adequately describes the dependence of liquid volume vs. time for the centrifugation of activated sludge. For the highly concentrated sludge it was found that the dewatering occurs through cake compression. Analysis of deformation models leads to the conclusion that for the compressible cake it is necessary to introduce a parameter characterising the cake plasticity dependence on the centrifugation time. The developed model was validated by fitting numerous experimental data. The main advantage of the proposed model is the possibility to fit the liquid phase accumulation kinetics during centrifugation over a wide range of activated sludge concentration values, from suspensions up to structured and paste-like cake consistency.