Pervaporation tubular modules

A number of hydrocarbon separations have been intensely studied and piloted in recent years and commercialization is expected soon. Pervaporation is expected to be one of a number of proven options for sulfur and benzene removal from fuels and olefin/ paraffin separations. These plants will use robust, specially engineered polymer membranes, installed in large-scale tubular modules. 

Tubular loop reactors, 25 710 Tubular membrane modules, 25 821 Tubular pervaporation modules,... 

Morigami, Y., Kondo, M., Abe, J., Kita, H., and Okamoto, K. (2001) The first large-scale pervaporation plant using tubular-type module with zeolite NaA membrane separ. Purif. Tech., 25, 251-260. 

The effect of concentration polarization on specific membrane processes is discussed in the individual application chapters. However, a brief comparison of the magnitude of concentration polarization is given in Table 4.1 for processes involving liquid feed solutions. The key simplifying assumption is that the boundary layer thickness is 20 p.m for all processes. This boundary layer thickness is typical of values calculated for separation of solutions with spiral-wound modules in reverse osmosis, pervaporation, and ultrafiltration. Tubular, plate-and-ffame, and bore-side feed hollow fiber modules, because of their better flow velocities, generally have lower calculated boundary layer thicknesses. Hollow fiber modules with shell-side feed generally have larger calculated boundary layer thicknesses because of their poor fluid flow patterns. 

Both Mitsui [26] and Sulzer [27] have commercialized these membranes for dehydration of alcohols by pervaporation or vapor/vapor permeation. The membranes are made in tubular form. Extraordinarily high selectivities have been reported for these membranes, and their ceramic nature allows operation at high temperatures, so fluxes are high. These advantages are, however, offset by the costs of the membrane modules, currently in excess of US 3000/m2 of membrane. 

M. Kondo, M. Komori, H. Kita and K. Okamoto, Tubular-type Pervaporation Module with Zeolite NaA Membrane, J. Membr. Sci. 133, 133 (1997). 

FIGURE 6.27 General working principle of a pervaporation or vapor permeation module equipped with tubular ceramic membrane elements. 

In spite of all these hurdles, there are already industrial-scale applications of zeolite membranes for solvent dehydration [106] by pervaporation plants using tubular zeolite A membranes with 0.0275 m of permeation area each (see Section 10.2.3). Li et al. [280] have prepared large area (0.0260 m ) ZSM-5 membranes on tubular a-alumina supports. This work is also interesting from the industrial point of view because the authors used inexpensive n-butylamine as template. Indeed, the cost required for industrial modules, on a general basis, is still far from clear. However, it must be noted that most of the costs can be ascribed to the module, and only 10%-20% to the membrane itself [3]. This underlines again the importance of preparation of zeolite membranes on cheaper, alternative supports that can also pack more area per unit volume. 

Kondo M, Komori M, Kita H, and Okamoto K. Tubular-type pervaporation module with zeolite NaA membrane. J Membr Sci 1997 133 133-141. 

Tubular pervaporation and vapor permeation modules are also under development to house polymer membranes and promise more predictable performance, easier membrane replacement, isothermal operation, and lower costs. 

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