Relative cost

In the case of a liquid recycle, the cost of this pressure increase is usually small. Pumps usually have low capital and operating costs relative to other plant items. On the other hand, to increase the pressure of material in the vapor phase for recycle requires a compressor. Compressors tend to have a high capital cost and large power requirements giving higher operating costs. 

Ultrasonic nebulizers are almost free of clogging from solute, have better detection limits, and have become popular despite their high cost relative to the pneumatic forms. A typical construction of an ultrasonic nebulizer is shown in Figure 19.17. 

Multiple-hearth roasting offers ease of operation, abiUty to handle a wide variety of ores or blends, and Httle downtime. On the other hand, these furnaces are no longer being built because of their high capital and labor costs, relatively low sulfur dioxide off-gas, need for added fuel, and marginal opportunity for waste-heat recovery. 

Anthraquiaone vat dyes have been used to dye cotton and other cellulose fibers for many decades. Despite their high cost, relatively muted colors, and difficulty ia appHcation, anthraquiaone vat dyes stUl form one of the most important dye classes of synthetic dyes because of their all-around superior fastness. 

Steam-Generating Facilities These form the second largest investment item for chemical-plant auxiliaiy equipment. Variations in capacity, location indoors or outdoors, the type of fuel used, pressure and temperature levels, and the type of process served have an important effect on actual cost as well as on cost relative to other auxiliaiy items. Package boiler instaUations can be purchased as shop-built units which are assembled, piped, and wired ready to be erected on the owner s foundations. They are available in units up to about 136,000 kg/h (300,000 Ib/h), although units larger than about 45,360... 

Relatively low capital cost Relatively small space requirements Ability to collect particulates as well as gases Collected substances may be recovered by distillation... 

Solvent Recovery The largest current industrial use of pei vapo-ration is the treatment of mixed organic process streams that have become contaminated with small (10 percent) quantities of water. Pei vaporation becomes vei y attractive when dehydrating streams down to less than 1 percent water. The advantages result from the small operating costs relative to distillation and adsorption. Also, distillation is often impossible, since azeotropes commonly form in multicomponent organic/water mixtures. 

Type of Fuel Expected Actual Maintenance Cost Relative Maintenance Cost Factor... 

Assembly on crankshaft is virtually impossible, except with very short or built-up crankshafts Cost relatively high Hardness of shaft unimportant... 

Cost relatively low Hardness of shaft important with harder bearings... 

Phenol, formaldehyde, and urea have been copolymerized to achieve resins and subsequent networks with improved flame retardance and lower cost relative to phenol-formaldehyde analogues. The condensation of a phenolic methylol group with urea (Fig. 7.32) is believed to be the primary reaction under the weakly acidic conditions normally used. 

The decision theory is valid for variable costs but does not consider the problem of capacity allocation. In many contexts, screening capacity is a sunk cost, and there is a need to consider the straw that broke the camel s back, the first compound that exceeds capacity. There is no need to ration resources that are not scarce and have trivial variable costs relative to the potential value that their use can create. This reasoning leads naturally back to use of easily understood, intuitive flow and capacity visualizations for the relevant simulations. 

Instrumental cost Relatively low Medium-high (e.g. Raman, NMR, PyFTIR)... 

Approximate cost relative to polyethylene, volumetric basis. 

Operating cost may be relatively high (D) Operating cost relatively low (A)... 

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