Reverse osmosis networks

El-Halwagi, M. M. (1992). Syndiesis of reverse osmosis networks for waste reduction. AlChE 1185-1198. 

In most industrial applications, it is rare that a single RO module can be used to address the separation task. Instead, a reverse-osmosis network (RON) is employed. A RON is composed of multiple RO modules, pumps and turbines, llie following sections describe the problem of synthesizing a system of RO modules and a systematic procedure for designing an optimal RON. Once a RON is synthesized, it can be incorporated with a mass integration framework (see Problem 11.6). 

Zhu, M., El-Halwagi, M. M., and Al-Ahmad, M. (1997). Optimal design and scheduling of flexible reverse osmosis networks. J. Membr. Sci., (in press). 

Prediction of reverse osmosis performance is usefiil to the design of RO processes. Simulation of RO processes can be separated iato two categories. The first is the predictioa of membrane module performance. The second is the simulation of a network of RO processes, ie, flow sheet simulations, which can be used to determine the optimum placement of RO modules to obtain the overaH process objective. 

Given the first type of simulation, it is advantageous to be able to design a system of RO modules that can achieve the process objective at a minimal cost. A model has been iategrated iato a process simulation program to predict the stream matrix for a reverse osmosis process (132). In the area of waste minimization, the proper placement of RO modules is essential for achieving minimum waste at a minimum cost. Excellent details on how to create an optimal network of RO modules is available (96). 

Membrane module network design, in reverse osmosis, 21 666 Membrane modules, 15 818-824 21 636 hollow-fiber, 15 819-821, 823 plate-and-frame, 15 821 selecting, 15 821-824 spiral-wound, 15 818-819, 823-824 tubular, 15 821... 

An industrial reverse osmosis unit consists of many semipermeable membranes packed around highly pressurized saltwater. As desalinated water is pushed out one side, the remaining saltwater, which is now even more concentrated, exits on the other side. A network of reverse osmosis units operating parallel to one another can produce enormous volumes of fresh water from saltwater. 

Cadotte discovered that aromatic diamines, interfacially reacted with triacyl halides, gave membranes with dramatically different reverse osmosis performance characteristics than membranes based on aliphatic diamines. 56 Before that time, the area of aromatic amines in interfacial membrane formation had been neglected because of two factors (a) the emphasis on chlorine-resistant compositions, which favored use of secondary aliphatic amines such as piperazine, and (b) poor results that had been observed in early work on interfacial aromatic polyamides. The extensive patent network in aromatic polyamide (aramid) technology may also have been a limiting factor. 

Figure 5.12 Topside and underside of the FT-30 composite reverse osmosis membrane (a) topside showing well-developed ridge-and-valley structure, and also an area of membrane barrier layer folded over upon itself (b) underside of the barrier layer (foldover zone) showing the network of micropores inside the ridge-and-valley structure.

---