Membranes capital cost

Installed capital cost + membrane capital cost) X capital charge rate... 

Tubular Modules. Tubular modules are generally limited to ultrafiltration appHcations, for which the benefit of resistance to membrane fouling because of good fluid hydrodynamics overcomes the problem of their high capital cost. Typically, the tubes consist of a porous paper or fiber glass support with the membrane formed on the inside of the tubes, as shown in Figure 24. 

FIG. 22-55 Typical capital-cost schematic for membrane equipment showing trade-off for membrane area and mechanical equipment. Lines shown are from families for parallel hues showing hmiting costs for membrane and for ancillary equipment. Abscissa Relative membrane area installed in a typical membrane process. Minimum capital cost is at 1.0. Ordinate Relative cost. Line with positive slope is total membrane cost. Line with negative slope is total ancillary equipment cost. Curve is total capital cost. Minimum cost is at 1.0. 

Equipment and Economics A veiy large electrodialysis plant would produce 500 /s of desalted water. A rather typical plant was built in 1993 to process 4700 mVday (54.4 /s). Capital costs for this plant, running on low-salinity brackish feed were 1,210,000 for all the process equipment, including pumps, membranes, instrumentation, and so on. Building and site preparation cost an additional 600,000. The building footprint is 300 itt. For plants above a threshold level of about 40 m Vday, process-equipment costs usually scale at around the 0.7 power, not too different from other process eqiiip-ment. On this basis, process equipment (excluding the ouilding) for a 2000 mVday plant would have a 1993 predicted cost of 665,000. 

Capital Costs A typical medium-scale RO seawater plant might produce 0.25 mVs (6 MGD). For a plant with an open sea intake, seawater salinity of 38 g/1, and conversion of 45 percent, the overall cost woiild be 26.5 miUiou (1996). A capital breakdown is given in Table 22-18. Capital charges are site specific, and are sensitive to the salinity of the feed. A plant of this size would likely contain six trains. For seawater RO, the Best estimate for the slopes of the family of lines in Fig. 22-55 is —0.6 for the equipment and 0.95 for the membranes. Capital charges, shown in TaBle 22-19, usually dominate the overall economics the numbers presented are only an example. Seawater economics are based on Shields and Moch, Am. Desalination Assn. Conf. Monterey CA (1996). 

FME Flexible membrane liner TCC Total capital cost... 

Because membrane equipment, capital costs, and operating costs increase with the membrane area required, it is highly desirable to maximize membrane flux. 

A good estimate is that each of these areas comprise 25% of the capital cost. Membrane replacement and a pump rebuild may be required after 5 to 6 years, so some provision for these costs should clearly be made because they are not insubstantial. 

Electrodialysis is a particularly economic process for low-salinity waters when compared to RO because, although the initial capital cost may be 10 to 15% higher, it generally requires no pretreatment, it produces a higher recovery rate (around 80-85%), it has a lower operating and maintenance cost, and the membranes last twice as long (up to 10 years). 

There are important trade-offs to be considered when designing a gas separation using a membrane. The cost of a membrane separation is dominated by the capital cost of the membrane, which is proportional to its area, the capital cost of any compression equipment required and the operating... 

This type of cell is limited by the performance of the anion-exchange membrane. The membrane can tolerate only a limited concentration of acid in the anolyte before backdiffusion of protons through the anion membrane becomes rather significant, causing a decrease in the cell s current efficiency, and acid gets into the salt stream. Unconverted salt in the product solutions can be eliminated by the use of the three compartment device, but this option substantially adds to the capital costs and operating complexity of the plant. 

Orica Australia Pty Ltd, formerly ICI Australia, is the largest manufacturer of chlorine and caustic soda in Australia. In December 1998, the Orica Board sanctioned a project to replace two mercury cell plants with new membrane plants. The plants are due to be commissioned sequentially at the end of 2000/mid-2001 at a total capital cost of US 100 million. 

Fig. 15.1 The balance illustrating the depreciation of the old diaphragm plant versus the capital cost of a new membrane technology plant.

World-scale producers use spreadsheet analysis to evaluate the economics of different options over the lifetime of the plant (often 20 years is assumed), taking account of operating, maintenance and capital costs. The chlor-alkali industry also expects the current density (CD) to increase in a manner that is dependent on membrane development. Other important factors expressed by producers about membrane technology choice included component lifetimes and reliability. 

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