Multi-stage membrane systems

These membranes, evaluated at different temperatures, presented promising results [93]. They also presented good stability and a CO2 flux higher than 0.5m7m hbar was obtained at 55 °C, which is approximately the flue gas temperature. This membrane was tested and used for simulation and optimization of multi-stage membrane systems used... 

L. Zhao, R. Menzer, E. Riensche, L. Blum, D. Stolten, Concepts and investment cost analyses of multi-stage membrane systems used in post-combustion processes, Energ. Proced., 1,... 

Figuie 5.5 Example of a multi-stage or multi-loop membrane system... 

Single- and multi-stage membrane GS system for H2 recovery... 

Blood fractionation has been commercially practiced using microfillralion ceramic membranes. A multi-stage system is used where alumina membranes with varying pore... 

Figure 2.30 Design and operation schematic of a multi-stage, feed-and-bleed UF cross-flow system. Each membrane stage contains four UF modules in series. Fa, Fb and Fc represent recycle streams operating at 140, 171 and 202 gpm. P, Pn and Pm are recirculation pumps.

Figure 3.8 (a) A membrane bioreactor-based system for treating landfill leachates, (b) A multi-staged RO and reject RO integrated membrane system for treating landfill leachates. Source [17]. 

More complex multi-pass SWRO systems include the system used in Ashkelon, Israel, which uses four RO passes in series to treat seawater from an open water intake in the Mediterranean Sea (40,700 mg/1 TDS). The permeate must be produced with less than 0.4 mg/1 boron and 20 mg/1 chloride. Thus, a series of passes with changes in pH was necessary to obtain the required permeate water quaHty. The first pass has a recovery of 45% and is operated at neutral pH. Permeate from the feed end is collected as product, while permeate from the concentrate end is collected and flows to the second pass, which operates at 85% recovery and pH > 8.5 to achieve greater boron removal. The concentrate firom the second pass continues to the third stage, also operated at 85%, but at low pH. The objective of the third pass is to achieve higher recovery without salt precipitation. However, the boron removal in the third pass is minimal at low pH, and a fourth pass (high pH, 90% recovery) treats the third pass permeate for boron removal. Overall, the recovery is approximately 44%, and the plant uses 25,600 SWRO membranes and 15,100 BWRO membranes [3,51]. 

Membrane processes for this analysis include SWRO, BWRO, low-pressure RO (LPRO), brine recovery RO (BRO), pressurised MF/UF (pMF/UF), immersed membrane bioreactor (iMBR), cross-flow membrane filtration (XMF) and electrodeionisation (EDI). Membrane process characteristics for water treatment are detailed in Table 5.1. Typical process flow schematics of RO membrane plants are shown in Figures 5.1 and 5.2. RO/NF systems are typically multi-stage and single-pass or multi-stage and double-pass, as shown in Figures 2.21-2.23. 

Redox reactions at the interface between immiscible liquids fall into two classes. The first class includes spontaneous processes that occur in the absence of external electromagnetic fields. This type of redox transformation has been investigated in bioenergetics [2], model membrane systems [20] and at oil/water interfaces [1]. Redox reactions in the second class occur at the interface between immiscible electrolytes when external electrical fields are applied to the interface, and under these conditions interfacial charge transfer reactions take place at controlled interfacial potentials [11, 35, 36]. Such electrochemical interfacial reactions are usually multi-stage processes that proceed through five stages (i) diffusion of reactants to the interface (ii) adsorption of reactants onto the interface (iii) electrochemical reaction at the interface (iv) desorption of products from the interface (v) diffusion of products from the interface. 

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