Gary L. Foutch

The Sorption Capacity of Boron on Anionic-Exchange Resin

Boron sorption capacities on anionic-exchange resins vary with temperature, concentration, and resin crosslinkage. A semiempirical correlation, developed from boron solution chemistry, is presented to account for these variations. The relationship, based on boron chemistry and changes in Gibbs energy, can be stated approximately as Q = a{sub 1}C{sub B}{sup a{sub 2}}Z{sup a{sub 3}} exp[{minus}(a{sub 4}T + a{sub 5}T{sup 2} + a{sub 6}Z{sup 0.5})]. Correlation parameters, which vary with resin type, are evaluated experimentally. Parameter values for macroporous resin Diaion PA 300 and for gel-type resins Diaion SA10 and Amberlite IRN 78LC are presented. The resulting expression is used to determine boron sorption and desorption limitations on ion exchangers at various temperatures and concentrations, and to determine the interfacial boron concentration in equilibrium and rate models.

Comparison of near-wall treatment methods for high Reynolds number backward-facing step flow

A comparison of near-wall treatment methods using different turbulence models for flow over a backward-facing step is presented. A Reynolds number (Re) of about 38,000 (U ∞ = 44.2 m/s), based on the step height and the mean stream velocity, was considered. An appropriate near-wall treatment method is critical to the choice of turbulence model used to predict wall-bounded flow. Predictions were obtained by applying standard wall functions, non-equilibrium wall functions and a two-layer model with six different turbulence models. These results were compared with data by Driver and Seegmiller (“Backward-facing step with inclined opposite wall—experiments by driver and seegmiller”, 1985a, http://cfd.me.umist.ac.uk/ercoftac [2003, Jan 31]). Non-equilibrium wall functions with modified k − ϵ models predicted the closest reattachment length. However, the two-layer model gave results more representative of the entire flow pattern. The predictions show that a proper combination of turbulence models and near-wall treatment methods give reliable results.

An evaluation of mass-transfer coefficients for new and used ion-exchange resins

Abstract Mass-transfer coefficients for cation and anion exchange were determined for new and used condensate-polishing resins in use currently at two power plants. Experiments were performed over a concentration range from 65 to 3240 ppb sodium and 100 to 5000 ppb chloride at superficial velocities from 0.015 to 0.033 m/s in both mono and mixed beds. Using a simple industry-standard experimental technique, overall mass-transfer coefficients were obtained in the range from 1.2 × 10 −4 m/s to 2.5 × 10 −4 m/s. Fouled resins had coefficients 30 to 40% less than new resins. The method used to calculate these mass-transfer coefficients is compared with alternative data treatments that separate film and particle rate steps. Observations are compared with literature data.

Biological production of acetaldehyde from ethanol using non-growing Pichia pastoris whole cells

Acetaldehyde has been produced biologically using whole-cellPichia pastoris in a semibatch fermentor. Ethanol and air were fed continuously, and the product, acetaldehyde, was removed by the air stream. Operation of the reactor exceeded 100 h, maintaining high alcohol oxidase activity. Low cell-mass concentration (9.9 g/L) minimized product inhibition. Ethanol concentration in the broth, oxygen concentration in the air, and pH were evaluated for their effects on the fermentation process.

The role of polymer support crosslinking on reaction rates for solid-phase peptide synthesis

Etude comparee de la vitesse de synthese de polyphenylalanine sur 2 supports de polystyrene reticules respectivement avec 1 et 2% de DVB; la vitesse est beaucoup plus elevee avec le copolymere le moins reticule

Kinetics of Boron Sorption and Desorption in Boron Thermal Regeneration System

Boron is used in the primary coolant of pressurized water reactors in nuclear power generation for shim control. If boron concentration is decreased, fewer neutrons are adsorbed and more fission occurs. When boron concentration increases, less fission occurs. The boron concentration can be controlled by the use of ion-exchange resins operating in the Boron Thermal Regeneration System (BTRS). A better understanding of BTRS kinetics can enhance its potential use for chemical shim control. The concentration and temperature effects on boron sorption and desorption with Amberlite IRN-78LC resins are investigated both experimentally and theoretically for BTRS operating conditions from 0.1–0.2 mol/dm3 boron and 10–60°C. A model, based on a postulated boron-sorption mechanism, assuming linear driving force through the film with fast, reversible, local reaction equilibrium, is presented. Comparison with experimental data validates that the model predictions are reasonable. The results are also applicable to other boron ion-exchange systems, such as initial breakthrough predictions from water polishers used in manufacturing microchips.

Chapter 4 – Ion Exchange Borate Kinetics

Boron sorption from an aqueous solution onto an ion exchange resin involves several mechanisms, including dissociation and ionization of boric acid molecules both in solution and within the resin phase, complex formation, and protonation of N -methylglucamine function groups in boron-specific (chelating) resins.

Bead Settling During Cation and Anion Resin Separation

The production of ultrapure water by ion exchange requires thorough mixing of cationic and anionic resins. In many cases the resins are regenerated requiring bead-type separation prior to chemical treatment with the respective acid or base. Resin separation is predictable based upon backwash conditions, resin properties, and system geometry. An important factor in an accurate model is the drag coefficient relationship. There are numerous models available and the choice can result in significant prediction differences. This article presents data for resin bead fall within a full-depth column and discusses which drag coefficient model is most applicable. The expression by Massey showed the best agreement for this application.

Multi-Component Mixed-Bed Ion Exchange Modeling in Aminated Waters

A model for multi-component mixed-bed ion exchange in pH adjusted water is developed. Film diffusion controlled mass transfer is combined with bulk-phase reaction to determine mixed-bed effluent-concentration profiles. The cationic resin is initially in the hydrogen form. As exchange progresses, the hydrogen cycle is replaced by the amine cycle which produces a characteristic of amine form operation, sodium throw. The model predicts the transient sodium outlet concentration surge.