Strategies for Reduced Size of Large-scale Membrane Systems

10 Strategies for Reduced Size of Large-scale Membrane Systems 

Membrane, module and system performance are interdependent on each other. The membranes have to meet flux and selectivity requirements for a given application. There is a trade-off curve available between flux and selectivity so a preferred strategy is to supply a membrane that meets minimum selectivity and then boost the flux. But meeting the requirements in the lab for flux and selectivity are only the initial step since the membrane has to be designed and engineered into a working installation. 

Reducing the number of modules required for a system therefore has a 4-fold multiplier in reducing the steel and construction costs going into an installation. Membrane area per spiral wound module has improved over the years with a more refined selection of feed and permeate spacers. This then allows for more functional membrane area to be packaged into every module. This reduces the total number of required modules in large-scale installations. 

For new system builds the same strategy can be done with spiral wound modules designed for natural gas treatment. Grace has constructed a 30-cm (12-inch) diameter module versus the standard 20-cm (8-inch) diameter module. Since membrane area is a squared function of diameter, the ratio of 144 to 64 means a 225% increase in membrane area per module. Although the larger diameter modules and pressure housings each cost more there is potential for reduction in total system cost. 

of course, higher flux for a membrane would increase the volume of permeate output from the full-scale module. If selectivity is maintained than the total number of modules required is reduced. 

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