Hollow fiber, configuration

Microfiltration and UF membranes can be asymmetric, with a denser side and a more open side, or uniform without macrovoids (See Figure 16.3). The open area behind the denser surface in an asymmetric design means there is less resistance to water permeating the membrane. Operating pressure can be lower and the membrane systems can be more productive. The limitation of the asymmetric design is that the material, predominately used in the hollow fiber configuration, is not as strong as the uniform cross section. 

The temperature profiles for both feed and sweep sides are shown in Figure 9.13 with a maximum for each profile. Since the overall module was adiabatic, the feed gas was heated by the exothermic WGS reaction. The highest feed-side temperature was 158 °C at about z = 15 cm. Beyond that, the feed-side temperature reduced, and it became very close to the sweep-side temperature at the end of membrane reactor. This was due to the efficient heat transfer provided by the hollow-fiber configuration. 

The two most common RO membrane configurations used in water treatment today are spiral-wound and hollow fiber. The spiral-wound elements can operate at a higher pressure and at a higher silt density index (SDI) than the hollow fiber type, and thus may require less pretreatment (and are more tolerant of pretreatment upsets). They also are easier to clean than the hollow fiber type. The main advantage of the hollow fiber configuration is that it has the highest amount of membrane area per unit volume, thus requiring less space. Since there is only one hollow fiber element per pressure vessel, it is easier to troubleshoot, and it is easier to replace membrane modules. 

Modern distillation plants have unit capacities of about 25,000 t/d. The energy consumption is approximately 95 KWh/to distillate in the form of saturated steam of a pressure of about 2.2 bar and 4 to 5 KWh/to distillate in form of power for the pump drives. All distillation processes produce a distillate containing only 20 to 30 ppm salts (total dissolved solids). Reverse osmosis (RO) will be the alternative to distillation. The modules which are successfully employed are of the "spiral wound" or the "hollow fiber" configuration. Under favorable conditions, the economic service lifetime of the modules resp. the membranes is about 5 years and warranties for such a figure are given by manufacturers. 

Developed a one-dimensional non-isothermal model for the novel WGS membrane reactor with a C02-selective membrane in the hollow-fiber configuration using air as the sweep gas. 

We have developed a mathematical model for the countercurrent WGS membrane reactor with a CO2-selective membrane in the hollow-fiber configuration using air as the sweep gas. With this model, we have elucidated the effects of system parameters on the novel WGS membrane reactor for synthesis gases from steam reforming and autothermal reforming. The modeling results show that H2 enhancement via CO2 removal and CO reduction to 10 ppm or lower are achievable. For comparison and the completeness of the modeling work, we have also developed a similar model for the cocurrent WGS membrane reactor. 

We have developed a one-dimensional non-isothermal model for the countercurrent WGS membrane reactor with a C02-selective membrane in the hollow-fiber configuration using air as the sweep gas. Figure 1 shows the schematic of each hollow-fiber membrane with catalyst particles in the reactor. The modeling study of the membrane reactor is based on (1) the CO2 / H2 selectivity and CO2 permeance reported by Ho [1, 2] and (2) low-temperature WGS reaction kinetics for the commercial catalyst copper oxide, zinc oxide, aluminum oxide (CuO/ZnO/ AI2O3) reported by Moe [3] and others [4]. In this modeling study, the model that we have developed has taken into account critical system parameters including temperature, pressure, feed gas flow rate, sweep gas (air) flow rate, CO2 permeance, CO2 /H2 selectivity, CO concentration, CO conversion, H2 purity, H2 recovery, CO2 concentration, membrane area, water (H20)/C0 ratio, and reaction equilibrium. 

Kandwal, P., Ansari, S.A., Mohapatra, P.K., A highly efficient supported liquid membrane system for near quantitative recovery of radio-strontium from acidic feeds. Part II Scale up and mass transfer modeling in hollow fiber configuration, J. Membr. Sci. 405 06, 85, 2012. 

Lu et al. [Ill] later reported on the development of solid-state electrochemical linear actuators with a polyaniline yarn-in-hollow fiber configuration using an ionic liquid electrolyte. These yarn-in-hollow fiber actuators, which were constructed using a triflic acid-doped polyaniline solid fiber inserted into a triflic acid-doped polyaniline hollow liber. A porous polyacrylonitrile insert separated the two electrodes, which contained the [BMIM] [Bp4] electrolyte (Figure 2.27). It was demonstrated... 

In a slight modification to this solid-state actuator configuration, Lu et al. [108] reported the fabrication and performance of solid-state electrochemical linear actuators with a unique polyaniline solid-in-hollow fiber configuration. The basic device structure consists of a polyaniline solid fiber... 

Flat sheet membranes in a plate-and-frame unit offer the greatest versatility but at the highest capital cost (P6). Membranes can easily be cleaned or replaced by disassembly of the unit. Spiral-wound modules provide relatively low costs per unit membrane area. These units are more prone to foul than tubular units but are more resistant to fouling than hollow-fiber units. Hollow-fiber modules are the least resistant to fouling when compared to the three other types. However, the hollow-fiber configuration has the highest ratio of membrane area per unit volume. 

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