Multistage mixers

A successful variation of oil agglomeration was used for removal and dewatering of soot from a 1—3% soflds suspension consisting of <5 — fim particles in refinery process waters (Fig. 8). Heavy oil was added to the dilute slurry and intensely agitated in a multistage mixer. The soot agglomerated with the oil to form 3—5 mm pellets that were easily screened from the water (95). The pellets contained only 5—10% water. The process was modified to recover very fine clean coal, and it produced highly uniform, hard, spherical pellets 1—2 mm in diameter. 

Any mixer and settler can be combined to produce a stage, and the stages in turn arranged in a multistage cascade. 

FIG. 15-29 Kerr-McGee multistage mixer-settler, a) and (h) For uranium, (c) For vanadium extraction. 

Liquid-Liquid Extraction The actual configuration of mixers in multistage mixer-settlers and/or multistage columns is summarized in Section 15. A general handbook on this subject is Handbook of Solvent Extraction by Lowe, Beard, and Hanson. This handbook gives a comprehensive review of this entire operation as well. 

In fact viscosity reduction of diene elastomer blends with QDI show an optimum based on mixer discharge temperature. Figure 16.13 shows the results of two experiments done on the 16 L scale. The viscosities represent the viscosity of the fourth stage of a multistage mixing experiment. These compounds were 60/40 blends of either BR or SBR with NR and contained 50 phr of N-234 carbon black. 

Figure 3.49. Multistage mixer-settler cascade with entrainment backmixing. M and m refers to mixer and S and s to settler stagers are 1 to N.

In this process developed by Lurgi [17], the phenolic effluent is contacted with the solvent in a multistage mixer-settler countercurrent extractor (Fig. 10.8). The extract, containing phenol, is separated into phenol and solvent by distillation and solvent is recycled to the extractor. The aqueous raffinate phase is stripped from solvent with gas, and the solvent is recovered from the stripping gas by washing with crude phenol and passed to the extract distillation column. 

Although the most useful extraction process is with countercurrent flow in a multistage battery, other modes have some application. Calculations may be performed analytically or graphically. On flowsketches like those of Example 14.1 and elsewhere, a single box represents an extraction stage that may be made up of an individual mixer and separator. The performance of differential contactors such as packed or spray towers is commonly described as the height equivalent to a theoretical stage (HETS) in ft or m. 

Laboratory Extractors. Pilot-Scale Testing, and Scale-Up. Several laboratory units arc useful in analysis, process control, and process studies. The AKUFVE contactor incorporates a separate mixer and centrifugal separator. It is an efficient instrument for rapid and accurate measurement of partition coefficients, as well as for obtaining reaction kinetic data. Miniature mixer-settler assemblies set up as continuous, bench-scale, multistage, countercurrent, liquid-liquid contactors are particularly useful Tor the preliminary laboratory work associated with flow-sheet development and optimization because these give a known number of theoretical stages. 

Fig. 10.4 Flow diagram for the crosscurrent multistage mixer-settler.

Multistage High Pressure Mixer-Settler System... 

From this knowledge, the idea of using a mixer-settler system for the extraction with supercritical fluids was derived. The purpose of this project is to build a multistage high pressure apparatus and to compare the separation efficiency and behaviour of the new system with that for a conventional column. 

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