Centrifugal contactors equipment

Typical regions for application of contactors of different types are given in Table 13.2. The choice of a contactor for a particular application requires the consideration of several factors including chemical stability, the value of the products and the rate of phase separation. Occasionally, the extraction system may be chemically unstable and the contact time must then be kept to a minimum by using equipment such as a centrifugal contactor. 

The types of equipment used, which range from stirred tanks and mixer-settlers to centrifugal contactors and various types of columns, affect both capital and operating costs [9]. In the decision to build a plant, the choice of the most suitable contactor for the specific situation is most important. In some systems, because of the chemistry and mass transfer rates involved, several alternative designs of contacting equipment are available. In the selection of a contactor, one must consider the capacity and stage requirements solvent type and residence time phase flow ratio physical properties direction of mass transfer phase dispersion and coalescence holdup kinetics equilibrium presence of solids overall performance and maintenance as a function of contactor complexity. This may appear very complicated, but with some experience, the choice is relatively simple. 

Often the products of nuclear reactions have very short half-lives. This is especially true for the heaviest elements obtained by bombardment of heavy targets with heavy ions. To identify and characterize such short-lived nuclides, fast separations are required solvent extraction techniques are well suited to provide the required fast separations. For example, the SISAK method [68] has been successfully used in conjunction with in-line gas jet separators at heavy ion accelerators to identify short half-life actinide isotopes produced by collision of heavy atoms. The Sisak method involves use of centrifugal contactors, with phase residence times as low as tenths of a second, in conjunction with in-line radiometric detection equipment. 

Centrifugal Contactors. These devices have large capacities per unit, short residence times, and small holdup. They can handle systems that emulsify easily or have small density differences or large interfacial tensions or need large ratios of solvent to feed. Some types are employed as separators of mixtures made in other equipment, others as both mixers and settlers, and some as differential contactors. 

Develop the hardware (e.g., centrifugal contactors, sensors, and other devices) and accompanying equipment, such as waste-treatment systems. 

Flowsheet testing and data collection were performed using the General Atomic Company solvent extraction pilot plant equipment shown in Figure 1. Included in this equipment are several 5.1 to 7.6 cm (2 to 3 in.) diameter cylindrical glass pulse columns, a 15-2 cm (6 in.) diameter annular pulse column, a centrifugal contactor (Robatel Co.) and associated tanks, feed systems and concentrators. 

Two techniques appear to be useful for the bidentate extraction of actinides. The first is liquid-liquid solvent extraction, a method which has several advantages. Currently, however, the type of equipment needed (mixer-settlers, centrifugal contactors, etc.) is not available at RFP. We are better equipped to use a column technique. This can be done by sorbing the bidentate extractant on an inert solid support, loading ion exchange columns with the sorbent, and proceeding with column runs (extraction chromatography). 

Since these efficiency correlations are based on limited systems (ethanol extmction only) and in only one size contactor (16-stage Savannah River mini-mixer-settlers or 2 cm Argonne high-speed centrifugal contactor), their applicability to other systems and/or equipment is unknowa. 

Contacting equipment used in the extracting section must have low holdup to minimize solvent degradation from the intense fission-product radioactivity. Here, centrifugal contactors or pulse columns are preferred to mixer-settlers. In the scrubbing section and in the balance of the solvent extraction plant, mixer-settlers are often used. 

CodecontaminatioiL The codecontamination section consists of the HA extraction section equipped with short-contact-time centrifugal contactors and the HS scrubbing section equipped with pulse columns. In the HA section, uranium and plutonium in the aqueous feed and reflux from the HS section are extracted into the organic stream containing 30 v/o TBP. In the HS section any ruthenium extracted by TBP is scrubbed into the aqueous phase with 3 M HNO3. Then any zirconium-niobium in the TBP is scrubbed with 0.3 M HNOa. Scrubbing is at 50°C to enhance decontamination of ruthenium. 

FIG. A.l. Different types of continuous extraction equipment, (a) Mixer-settler, (b) Spray column, (c) Pulsed column, (d) Tubular centrifugal contactor. 

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