Membranes Operating cost effects

Although considerable research has been conducted with Pd-alloy foils, tubes, and thinner composite membranes, long-term durability and stability need to be further demonstrated, especially in the fuel reforming or WGS operating conditions, for acceptance of this technology in a commercial sector. Furthermore, mass-scale and cost-effective production of industrial-scale Pd-alloy thin-film composite membranes need to be demonstrated to be competitive in the hydrogen production and purification market. 

Kvaerner Chemetics have developed a novel, patented process [1] for the removal of multivalent anions from concentrated brine solutions. The prime market for this process is the removal of sodium sulphate from chlor-alkali and sodium chlorate brine systems. The sulphate ion in a brine solution can have a detrimental effect on ion-exchange membranes used in the production of chlorine and sodium hydroxide consequently tight limits are imposed on the concentration of sulphate ions in brine. As brine is continuously recycled from the electrolysers back to the saturation area, progressively more and more sulphate ions are dissolved and build up quickly in concentration to exceed the allowable process limits. A number of processes have been designed to remove sulphate ions from brine. Most of these methods are either high in capital or operating cost [2] or have large effluent flows. 

Flux. The film model (Equation 6.6) illustrates that increasing flux has an exponential effect on CP. If we accept that fouling is a consequence of CP the impact of excessive flux is obvious. As a result high flux membranes tend to be short lived and foul unless improved fluid management is able to enhance k. Selection of the appropriate flux and crossflow velocity is a trade-offbetween capital and operating costs (see cost of fouling below). 

In conclusion, the demonstration runs have shown that the membrane contactor dehumidification system is effective when the total loads of the refrigerated cell do not require an evaporative temperature of the cooling coil below —10 °C. In these conditions it has been shown that energy, operating costs and C02 emissions can be decreased up to 20% when optimized systems are built. The optimization is related mostly to the selection of adequate pumps, fans, heat exchangers. 

At CEA, the studies on this process have started more recently. The two critical components of the process components are the high-temperature decomposition reactor and the SDE. Beside the European project mentioned above on the process heat reactor for S03 decomposition, CEA studies therefore focus on the electrolysis section, with a pilot now in operation in Marcoule (see Figure 7). Indeed, a major challenge for the HyS process is the development of an efficient, cost-effective SDE. Prevention of S02 migration through the separation membrane of the electrolyser, which leads to undesired sulphur deposits, remains a major technical hurdle to overcome. Like for all electrolytic processes, economic competitiveness of the cycle will also depend on the minimisation of electrolysis overvoltage and on components lifetime (membrane, interconnectors). 

Adequate pretreatment is one of the fundamental keys to successful and cost-effective operation of an RO system. Pretreatment is designed to prevent or minimize membrane fouling, scaling and degradation of membrane performance and materials. This chapter covers mechanical and chemical techniques and technologies that are commonly used to pretreat RO systems. 

The submerged MBR system is a small-footprint, single-process unit that can achieve a high-quality standard with low solids production. The membrane systems typically utilize either micro- or ultramembranes configured as hollow fibers, flat sheets, or tubes depending upon the manufacturer. Experience over the past decade has proved MBRs to be reliable and cost-effective for high-quality effluent applications, and relatively easy to maintain and operate. The key parameters for MBR... 

Although MF and UF membranes have been shown to be a viable option as feed pretreatment for RO, long-term operating and cost data are required to verily that membrane pretreatment is more cost effective than conventional pretreatment. 

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