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Liquid-Liquid Separation
Published in Pau Loke Show, Chien Wei Ooi, Tau Chuan Ling, Bioprocess Engineering, 2019
Hui Yi Leong, Pau Loke Show, K. Vogisha Kunjunee, Qi Wye Neoh, Payal Sunil Thadani
A mixer-settler is a batch vessel that consists of two stages. The first chamber is an area where the two phases are mixed thoroughly, and the second chamber is where the mixture settles. The two phases separate by the force of gravity. In the first phase, the presence of a mechanical impeller brings the solvent and the feed stream into close contact with each other to permit the solutes to transfer from one phase to the other. The agitator’s motor mechanism also drives a turbine that pumps the now-homogenized mixture into the settling tank. The size of mixer-settlers varies with their purpose; for instance, laboratory mixers contain just the primary mixing stage, but mixers used in the copper-processing industry require a minimum of three mixers, and each of these acts as both a mixer and a pump. The benefits of using mixer-settlers in series is that the mixing time is prolonged, ensuring that all the material mixes thoroughly and there is no opportunity for the unmixed material to end up in the settling tank.
Design of a Modular Annular Centrifugal Contactor for Lab-Scale Counter-Current Multistage Solvent Extraction
Published in Solvent Extraction and Ion Exchange, 2023
Dominic Maertens, Koen Binnemans, Thomas Cardinaels
Annular centrifugal contactors (ACCs) are appealing equipment for counter-current multistage solvent extraction (SX), because they allow for high throughput at short residence times, have a small liquid hold-up, and a small footprint.[1] Packed and pulsed columns are also efficiently used for SX processes, but their required height (associated with a lack of physical stage separation) necessitates a tall process facility and building infrastructure. Especially for R&D purposes this is not always practical nor cost-efficient. Mixer-settlers have the advantage of a good stage efficiency, scalability, flexibility and throughput, although they can have relatively large liquid hold-up, requiring larger volumes of liquids compared to ACCs, and longer running times to reach equilibrium or steady-state conditions.
Holdup and regime transition in reciprocating and rotating sieve plate column (RRSPC) for C6(mim)PF6 ionic liquid –water system
Published in Solvent Extraction and Ion Exchange, 2022
Liquid-liquid extraction is widely used in the front-end as well as in back-end process of nuclear, chemical, and pharmaceutical industries.[1] Mixer-settler is the most widely used liquid-liquid extractor because of its simplicity, reliability, operating flexibility and high throughputs. Mixer-settler can handle difficult-to-disperse systems, such as those having high interfacial tension and/or large phase density difference. However, mixer-settlers have some disadvantages too. These include, (i) larger size, ii) high hold-up (i.e., high material inventory) within equipment, (iii) large foot print area etc.[2] On the other hand, columnar equipments are of compact and small sizes, required less foot print area, but need to select judiciously and design precisely.
Demonstration of Aqueous Reprocessing of U-Zr and U-Pu-Zr Metallic Alloy Fuels Using an Ejector Mixer-settler with Tri-n-Butyl Phosphate (TBP) as the Extractant
Published in Solvent Extraction and Ion Exchange, 2021
B Sreenivasulu, S. Rajeswari, A. Suresh, N. Sivaraman
In the nuclear industry a special type of liquid-liquid contactors are required due to the stringent conditions.[19] The requirements of solvent extraction contactors are as follows; (i) it must to able to handle a high throughput, (ii) should operate over a wide range of flow rates, (iii) should be able to operate in highly radioactive background, (iv) should be able to be operated and maintained remotely, and (v) it should operate efficiently. Three types of primary contactors are generally used in the nuclear fuel cycle such as mixer-settlers, packed or pulsed columns, and centrifugal contactors.[20–22] Each contactor has its own advantages and limitations. Mixer-settler consists of a mixing and settling chambers in which mixing of the aqueous and the organic phases together and separation of the phases by gravity occur, respectively. The mixer-settler has discrete stage units which offer simple operation and a wide range of capacities. Mixer-settlers require large area of floor space, large solvent inventory, and long contact times resulting in increased solvent degradation.[23–25] There are number of mixer-settler designs which have been used commercially for applications.[26–29] Mixer settlers with air pulsing of different designs are in use in the nuclear fuel reprocessing industry. Koganti et al. have developed a high efficiency air pulsed ejector mixer-settler.[24] In this type of mixer-settler, dispersion of one of the phases and transfer of liquid between the stages is achieved by ejector which is fitted at the bottom of each mixer. Ejector mixer-settler is most ideal for process development and flow sheet testing with active liquids in laboratory scale.