Membrane contactors surface area

Contactors have a number of advantages compared to simple liquid/gas absorb-er/strippers or liquid/liquid extractors. Perhaps the most important advantage is high surface area per volume. The contact area of membrane contactors compared to traditional contactor columns is shown in Table 13.2. Membrane contactors provide 10-fold higher contactor areas than equivalent-sized towers. This makes membrane... 

A pilot plant on recovery of copper from ammoniacal etching solutions was run with a good performance, as described in refs. [186,187]. LIX54 in kerosene was used as the membrane phase in SLM. Large pilot-plant HF contactors Liqui cel (diam. 25.4 cm, length 71.1 cm) with surface area of 130 m2 have also been used [186]. 

In addition to the design of the solid-gas contactor device, the yield of a desulfurization process directly depends on the physicochemical properties of the used adsorbent crystallite size of the active phase, specific surface area, and porous texture. In the case of a microporous membrane, if the gas flow is forced across the microporosity, it can be expected that the retention will be highly efficient. In return, the low amount of adsorbent restricts the potential applications to the elimination of traces in high-purity gas or to the design of integrated filters for miniaturized devices like micro fuel cells. 

Membrane-assisted solvent extraction processes have known an increasing number of applications in the last decades [1 ]. This technique not only overcomes the limitations of conventional liquid extraction, such as flooding, intimate mixing, limitations on phase flow rate variations, and requirement of density difference but also provides a large surface area of mass transfer per volume of contactor [5]. Excellent reviews of the technology and its applications were presented by Ho and Sirkar in 1992 [6], and by Gabelman and Hwang [7]. 

In general, membrane-supported liquid-liquid extraction is offered as a micro-porous hollow fibre module (Fig. 2.23). The membrane contactor contains thousands of micro-porous hollow fibres knitted into an array that is wound around a distribution tube with a central baffle. The hollow fibres are arranged in a uniform open packing allowing the utilisation of the total membrane surface area. The liquid flows over the shellside (outside of the hollow fibre), is introduced through the distribution tube and moves radially across the array of hollow fibres and then around the baffle and is carried out by the collection tube. 

Figure 4.11 illustrates, respectively, a common HFM module used in such applications and a plant where 48 degassing modules each having 220 m membrane surface area are being used for degassing water. In fact, membrane degassing of water in ultrapure water treatment is probably the largest application of membrane contactors [1,2,6]. 

In Figure 25.22, the scheme of experimental setup used for membrane extraction experiments was presented. The setup consisted of membrane contactor with aqueous and organic circuits, two pumps, and the control equipment flowmeters, pressure gauges, and valves. Two phases aqueous and organic solutions circulated countercurrently. Membrane contactor X50 2.5 x 8 Liqui-Cel Extra-Flow, Celgard, was used in the system. The characteristics of the membrane were shown in Table 25.17. The small volume module houses 11,000 capillaries with 1.9 m inner surface area. The module possesses the central baffle, which enables uniform flow inside the shell. 

Membrane contactor (MC) is a phase-contacting device for use in gas absorption and stripping (degassing) processes as well as in biomedical gas transfer processes [44, 46]. The function of the membrane is to facilitate diflfusive mass transfer between contactir phases such as liquid-liquid, gas-liquid and gas-gas. The membrane phase contactor uses polyolefins, e.g., polypropylene (PP) microporous hollow fibres membranes, which are packed densely in a high surface area module. Since membranes are hydrophobic and have small pores (0.05—0.1 3m), water does not pass through the membrane pores easily. The pressure required to force water to enter the pore is called the breakthrough pressure, which for a PP membrane with a pore size of 0.05 pm is greater than 10 bar g. 

Despite the wide availability of flat-sheet membranes and the impressive permeability they offer, the hollow fibre configuration is usually preferred due to its high packing density. The membrane surface area of commercial hollow fibre membrane modules varies in the contactor volume range of 1500-3000 m /m (Kumar et al, 2002), whereas in conventional contactors (bubble column, packed and plate columns) it is in the range of 100-800 mVm. Table 2.4 clearly shows that MC offers a much larger contact area per unit volume than other conventional absorbers (Yan et al, 2007). 

A hollow fibre polypropylene membrane contactor is used in the gas-solvent absorption pilot plant the solvent is drawn directly from the solvent capture plant. The membrane contactor, with about 8 m surface area between the solvent and flue gas, is designed to handle 10 kg h i of... 

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