Materials of construction, relative costs

Materials of construction Relative cost per ft of tray area (based on carbon steel = 1)... 

Cost. Bubble-cap plates are appreciably more expensive than sieve or valve plates. The relative cost will depend on the material of construction used for mild steel the ratios, bubble-cap valve sieve, are approximately 3.0 1.5 1.0. 

If the inside surface of a large reactor is stainless steel, clad steel plate is the material of construction for the reactor shell. The extra cost for stainless steel cladding is relatively low. Highly polished surfaces in such reactors can best be obtained by electric polishing, which we effect by a special method. At present it is not possible to construct 100-m3 or 200-m3 reactors with enamelled inside walls. If sufficient protection could be provided against damage to enamel, which on large... 

The relative costs of three materials of construction in relation to mild steel... 

The choice of material of construction will influence the extent of possible corrosion and may affect the retention of other deposits, for instance corrosion resistant titanium tubes have been known to foul more rapidly than some stainless steel alloys under similar conditions. It is unlikely in large cooling water systems, e.g. power station condensers, that treatment of the heat exchange surfaces will be considered as a feature for the reduction of fouling, due to the relatively high costs involved including initial cost and maintenance. 

Industrial nitric acid processes are basically of three types (1) ambient, (2) medium, and (3) high pressure. For the 1 ambient pressure variety, a low pressure drop contactor like packed tower is desired. The other two types can be handled by a relatively high pressure drop contactor like plate column. It may be noted here that the NO absorption train constitutes a major portion of the nitric acid plant cost since the material of construction (SS-304 ELC) is relatively expensive. Table 3.2 compares packed and plate columns for NO absorption. 

Polyethylene (PE) and polypropylene (PP) exemplify a class of materials called polyolefins. Composites based on these resins are relatively new by the standards of those early materials of construction. Recent efforts to use these types of materials combine inherent cost-effectiveness with a wide spectrum of end-use applications as film, fiber, and moldings. The impetus for this remarkable development is attributed to the ease of polyolefin manufacture with effective production and purification of the monomers from a variety of sources, ongoing improvements of the catalyst, and large well-controlled polymerization units. Consequently, a strong market demand for good performance and cost-effective materials have spurred a multibillion dollar industry. 

Capital costs for vapor compression systems are usually higher than for multiple-effect systems, because they are usually designed for a lower temperature difference across the evaporator. As a result, greater heat transfer surface is required. In addition, the compressor and drive are relatively expensive. Equipment costs are affected by variables such as feed properties, materials of construction, available energy supply, and calandria type. Expected maintenance and necessary spare parts must be also evaluated. Heat exchangers must be provided to exchange heat between feed and condensate and between feed and product. Other costs that must be considered, but are less easily defined, are the penalty for interrupted operation during repairs and the part load response. 

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