Separations Technology最新文献

The present work includes experimental and theoretical studies of the characterization of filter cakes. A filter test apparatus, in which the local pressure profile can be determined during the build up of the filter cake was developed. Efforts were made to minimize the influence of settling and the so called wall-effects related to the pressure measurements. Also a method to calculate local filtration properties (specific filtration resistance and porosity) was developed. In the method, conventional empirical equations describing the relation between the local filtration properties and the local pressure were used. The basic idea is to direct the calculation in such a way that the obtained numerical values of the parameters in the empirical equations reflects the local conditions. The developed method was found to be superior compared to a method where only average data on the filtration properties was used to calculate the corresponding parameters. Finally, the method was found to be stable as well as reliable.

Comparisons are made between three different models for calculating the entropy for separating a polydispersed system of particles from a fluid. These three entropy models provide the efficiency of a separation and the criteria for the separation. Previous models for either monodispersed or regular solution do not provide constrains for the models. The model for calculating the entropy for separating a solid-liquid system of polydispersed particles is rigorous. The rigorous entropy model is then compared to the regular solution and monodispersed models in calculating a separation efficiency and sedimentation criteria. The comparisons of the three models show only a negligible difference in the calculations for the efficiency of the separation and the sedimentation criteria. Hence, the simpler monodispersed model may be used for systems with distributions in particle size.

Soil contamination from hazardous materials has existed since the beginning of the industrial age. At that time, unwanted liquid products were disposed of by dumping into unlined pits. Today, the chemical industry is faced with cleaning up these old hazardous waste sites as well as any new site. The hardest part associated with successful soil remediation is the separation of the adsorbed contaminant from the soil. Current research has demonstrated promising results for the destructive separation of hazardous contaminants using bioremediation. This paper addresses the process and results for biological destruction of contaminants from a town gas soil using Mycobacterium sp.

The efficiency of solid-liquid separation in coagulation-sedimentation processes depends greatly upon the performance of the coagulant with respect to the production of suitable floc properties. High-molecular weight polymers that function by interparticle bridging can serve as very effective coagulant-aids, however, the dynamic processes of polymer adsorption and macromolecular rearrangement may have a decided effect upon the determination of floc characteristics. Ideally, adsorption would occur rapidly with the macromolecule in an extended, rod-like conformation; this configuration increases the effective collision radius and results in rapid growth. However, effective separation by sedimentation is best achieved by dense, compact flocs characterized by reduced interparticle distances. In addition, the resulting sludge must ultimately be dewatered; therefore, the ease with which water flows around and through the settled flocs is of considerable importance. These requirements call for floc properties that are not completely compatible with one another. Consequently, efficient coagulation processes must compromise and employ operational conditions that produce flocs suitable for the subsequent solid-liquid separations.

Separation of close boiling point mixtures of alkylphenols, such as p-cresol/2,6-xylenol, and m-cresol/ 2,6-xylenol has been attempted using NaX zeolites. Effect of the cation on the selectivity has also been investigated. The NaX zeolite adsorbs p-cresol and m-cresol selectively from their mixtures with 2,6-xylenol, while CaX and BaX zeolites preferentially adsorb 2,6-xylenol. The selectivity seems to be decided by the diffusion in the zeolite framework.

Solutions of the deep bed filtration equations are sought for situations involving spatially varying initial porosites and temporally varying superficial velocities and inlet concentrations. Results of a general nature are obtained for both a quasistatic model and a diffusionless model. In the latter case it is shown that one numerical solution can sometimes be used to infer information about a class of problems.

As a step towards development of an efficient method for separation of cephalosporin C from fermentation broth, reactive extraction in supported liquid membrane has been investigated using simulated feed solution. Experiments were conducted in a diaphragm type cell with Celgard-2400 membrane as the solid support and Aliquat-336 as the carrier dissolved in butyl acetate as the diluent. Cephalosporin C was permeated across the membrane from an alkaline feed phase of carbonate buffer into an acidic strip solution of acetate buffer via a coupled transport phenomenon involving Cl ions. The permeation process was analyzed from the hypothesis of an overall transport dependance on diffusion across the liquid membrane and total re-extracting in the stripping phase.

Granular filtration of polydispersed aerosols were studied experimentally. The objectives of the study were to investigate the effect of deposited particle size on the increase of the unit collector efficiency and to quantify the increase for predicting filter performance. An algorithm for determining the effluent concentration histories of polydispersed aerosol filtration was presented. Together with the correlations developed in this work, prediction of filter performance can be made readily. Good agreements between experiments and predictions based on the correlations established in this work were observed.

Recovery of polyvinyl alcohol (PVA) by ultrafiltration (UF) from simulated desizing wastewater is investigated. Batch experiments were conducted to examine the performance characteristics of the OF membranes of the hydrophilic and hydrophobic types and of different pore sizes. The performances of those membranes were compared using several characteristic parameters of the ultrafiltration process. The experimental results have indicated that the ultrafiltration performances of different membranes are not be easily judged by a single characteristic parameter alone. Instead, several characteristic parameters must be considered simultaneously. In the context of overall performances, the hydrophilic membranes are found to be superior to the hydrophobic types. The OF membrane of a lower molecular weight cut-off (MWCO) is definitely a better choice than that of a higher MWCO. The effects of operating pressure, temperature and mixer speed on the ultrafiltration performances were also explored. Reduction of the pollution strength of the permeate in terins of chemical oxygen demand (COD) was also considered.

A mathematical model for a simulated moving bed adsorption system is presented using a more precise approach. In this precise approach the differential equations along with appropriate boundary conditions are written for each adsorption column as distinct from the section approach adopted by previous workers in order to examine the column dynamics of the actual system. An axially dispersed plug flow model with linear driving force rate expression for mass transfer and nonlinear Langmuir equilibria are considered. The time-dependent boundary conditions for each column are formulated and related to switching time. Computations are performed for several cycles till the cyclic steady state is reached. The results obtained from the present model for the limiting cases of linear glucose-fructose and nonlinear monoethanolamine-methanol systems are compared with available experimental data and are found to agree well. The effect of various process parameters on the performance of systems are investigated and the distinction from the section approach is emphasized. The present study reveals that the system performance and dynamics are strongly dependent on axial dispersion, eluent-to-feed ratio, bed length and switch time. It is observed that there exists a set of optimum values of all the parameters for best process performance, which can be evaluated from the present simulation.