Membrane Cost Analysis

The methods developed by EBC and others in the late 1990s using hydrocyclones and phase-inversion techniques may be sufficient for separation of the treated oil from the aqueous phase and biocatalyst. However, a cost analysis of such methods may be necessary to determine the economic feasibility. Recent work using hydrophobic membranes, magnetically separable immobilized biocatalysts and other techniques may provide alternate methods for separation of oil and recycling biocatalyst. A comparison of these techniques with each other and the previously investigated hydrocyclone techniques is needed to demonstrate improvements in the separation efficiency. 

Based on a simple economic analysis, it appears that, when seawater is used as the salt solution, a membrane with a water flux in PRO of about 1 x 10 2cm3/cm2-sec ( <200 gal/ft2-day) is required to make the process economically viable in today s economy, even if the installed membrane cost is as low as 100/m2. The highest flux we projected under these PRO conditions among the RO membranes tested was only somewhat greater than 1 x 10 cm3/cm -sec ( 2 gal/ft -day), for a power output of 1.6 watt/m2. 

Kaldis, S.P., Skodras, G. and Sakellaropoulos, G.P. (2004) Energy and capital cost analysis of C02 capture in coal IGCC processes via gas separation membranes. Fuel Processing Technology,... 

In this paragraph, a sensitivity analysis is made of the costs of the different processes. It must be noted in advance, however, that it is very difficult to provide really accurate quantitative cost estimations, because of the lack of information on, for example, membrane selectivity and life-time and the costs of supported membranes and sealing. An attempt to provide yet a quantitative cost analysis has been made in [21],... 

The method of choice to determine, under meaningful conditions, the location of synthetic ion channels and pores in bilayer membranes is fluorescence depth quenching (FDQ) [4, 11]. In this well developed but costly analysis, the position of a quencher in the lipid bilayer is varied systematically. Analysis of the dependence of the efficiency to quench a fluorescent synthetic ion channel or pore on the position of the quencher reveals transmembrane, central or interfacial location (Fig. 11.13b-d). 

The results of this analysis are summarized in Figures 11a and 11b. The capital cost analysis indicates that the membrane system is very attractive compared to either alternative technology. Capital cost for the continuous centrifuges is at least four-fold higher, while the precoat filter is two-fold more costly. The cost per kilogram of enzyme produced, which includes all operating costs and capital depreciation over ten years, indicates that the membrane system can achieve the same separation at half the cost for centrifugation. 

Jiao K, Li X (2009) Three-dimensional multiphase modeling of cold start processes in polymer electrolyte membrane fuel cells. Electrochim Acta 54 6876-6891 Bar-On I, Kirchain R, Roth R (2002) Technical cost analysis for PEM fuel cells. J Power Sources 109 71-75... 

Table 3.5. Base case cost analysis of the five fermentation membrane configurations. Adapted from...

A cost analysis and comparison between two anaerobic processes for the treatment of wastewater was also carried out by Pillay et al. [6.23]. The first configuration consisted of a conventional system coupling a digester with a sedimentation unit. In the second configuration the sedimentation step was replaced by a membrane separation unit treating a side stream. Pillay et al [6.23] report that for a 60 Ml d plant the MBR process results in capital savings of about 27 % when compared with the classical configuration. 

A cost analysis of an extractive membrane bioreactor (EMB) for wastewater treatment has been reported by Freitas dos Santos and Lo Biundo [6.24]. The EMB studied was similar with those reported in Chapter 4. Calculations were carried out for a feed flowrate of 1 m h of wastewater polluted with dichloromethane at a concentration of 1 g l A minimum pollutant removal rate of 99 % and 8000 h of operation per year were considered. As expected, the analysis indicated that the costs are strongly dependent on the pollutant flow entering the bioreactor to be transformed. Two key parameters, namely the total membrane area required and the external mass transfer coefficient, were studied. The results show that the costs and membrane area decrease significantly as the mass transfer coefficient increases from 0.5 x 10 to 2.0 x 10 m-s (these values are typical for large units, while laboratory measured values harbor around 5x10 m-s [624]). Using a mass transfer coefficient of 1.0 x 10 m s the authors calculated the costs and the membrane area required for different wastewater flowrates. These results are shown in Fig. 6.3. 

Goddin63 presented a detailed cost analysis for recovering C02 from casinghead gas where bulk removal is effected by membrane separation followed by a conventional gas treating process. His analysis showed that for feed gas containing more than 30% C02, the process heat requirements for a membrane separation process are approximately 30 to 40% lower than for a cryogenic process. When compared to an acid gas removal process using DEA as a solvent, the membrane separation process requires only 20 to 25% of the process heat requirement. 

A water quality parameter (WQP), which considers colloid, organics and salt rejection, was established for the membranes investigated. A linear relationship between WQP and log pore diameter was found. Finally, a complete cost analysis was replaced by the evaluation of A) membrane cost as a function of dean water flux and operation at fouled conditions, B) WQP as a function of membrane cost, C) ferric chloride cost, and D) energy costs. 

Filteau G., Moss P. (1997), Ultra-low pressure RO membranes an analysis of performance and cost. 

A detailed cost analysis for a polymer electrolyte membrane fuel cell power plant of 5 kW was provided in 2006 by Kamarudin et al. According to their data, the total cost of such a plant will be about 1200 of which 500 is for the actual fuel-cell stack and 700 for the auxiliary equipment (pumps, heat exchangers, etc.). The cost of the fuel-cell stack is derived from the components as 55 /kW for the membranes, 52 /kW for the platinum, 128 /kW for the electrodes, and 148 /kW for the bipolar plates. 

This chapter has reported the basic features of a membrane reactor the properties of selective membranes, fabrication methods, actual markets and a cost analysis are described and assessed. 

The case studies analysis, which focused on hydrogen production processes, demonstrates the potential of membrane reactor technology in terms of improving performance and reducing operating temperature, even if some crucial obstacles have yet to be overcome, as developing a reliable fabrication method and reducing membrane costs. 

However, there were a few attempts to evaluate the operation costs of PMRs in terms of energy consumption. For example, Ryu et al (2005) performed an energy cost analysis of a PMR applied for removal of humic acids, dyes and 4-chlorophenol from water (Table 21.4). The pilot scale PMR was composed of a 500 dm reactor with MF submerged membranes (effective surface area of 8 m ) above which UV-A lamps were positioned (365 nm, 300 W). In the bottom of the reactor an air blower was mounted. The permeation was conducted by means of a suction pump. The PMR was found by the authors to be cost effective (9.65 kWh/m ) compared to other conventional processes. However, it was also noted that many terms including capital cost, membrane replacement and maintenance should be also considered to build a complete budget (Ryu et aL, 2005). Such an economic analysis of various membrane systems and applications was recently discussed by Calabrb and Basile (2011). 

Table 21.4 An energy cost analysis of a PMR with submerged membranes...

Key words membrane bioreactors, cost analysis, productivity. 

Di Luccio M, Borges C P, Alves T L M, (2002), Economic analysis of ethanol and fructose production by selective fermentation coupled to pervaporation effect of membrane costs on process economics , Desalination, 147,161-166. 

Yeo K, (2010), Cost Analysis of Membrane Bioreactors to Reverse Osmosis Filters, http //nature.berkeley.edu/classes/esl96/projects/2010flnal/YeoK 2010.pdf. 

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