Chemical processing economics

J. Happel and D. G. Jordan, Chemical Process Economics, 2nd ed., Marcel Dekker, New York, 1975. 

Contrac tors bids offer the most rehable information on cost. Order-of-magnitude costs, however, may be required for preliminary studies. One way of estimating them is to obtain cost information from similar facihties and scale it to the proposed installation. Costs of steel storage tanks and vessels have been found to vaiy approximately as the 0.6 to 0.7 power of their weight [see Happel, Chemical Process Economics, Wiley, 1958, p. 267 also Williams, Chem. Eng., 54(12), 124 (1947)]. AU estimates cased on the costs of existing eqiiipment must be corrected for changes in the price index from the date when the equipment was built. Considerable uncertainty is involved in adjusting data more than a few years old. 

Happel, J., Chemical Process Economics. Wiley, New York, 1958,... 

Adequate information must be available for installed costs of piping and pumping equipment. Although suppliers quotations are desirable, published correlations may be adequate. Some data and references to other published sources ate given in Chapter 20. A simplification in locating the optimum usually is permissible by ignoring the costs of pumps and drivers since they are essentially insensitive to pipe diameter near the optimum value. This fact is clear in Example 6.8 for instance and in the examples worked out by Happel and Jordan (Chemical Process Economics, Dekkcr, New York, 1975). 

Other detailed studies of line optimization are made by Happel and Jordan (Chemical Process Economics, Dekker, New York, 1975) and by Skelland (1967). The latter works out a problem in simultaneous optimization of pipe diameter and pumping temperature in laminar flow. 

Remember this is for a fixed per-pass conversion and inlet composition and flowrate. If the desired conversion is decreased, the inlet temperature can be increased and the reactor size reduced. Of course, this means that more unreacted material in the reactor effluent must be recovered and recycled. Keep in mind the difference between the per pass conversion, which is a crucial design optimization variable, and the overall conversion of the entire process, which is typically quite close to 100% because the cost of raw materials imposes a severe economic penalty on a process with low overall conversion. A lower per-pass conversion translates into a higher recycle flow with its associated higher energy and capital costs. But chemical process economics usually dictate that capital investment can be justified to save energy, and both energy and capital can be expended to reduce losses of raw materials and/or products. 

Apart from development of new catalysts with enhanced activity, few processes with innovative chemistry are currently developed for C-H transformation in aromatics. Though new processes using cheaper raw materials or reducing the number of reaction steps may seem attractive at first glance, efforts for process development including research, scale-up, pilot plant, and timeline must be considered. Especially for large scale-synthesis of bulk chemicals process economics... 

The base case" is for payout time of 2yr, steam cost of 0.50/1000 lb, vapor flow rate Ga = 15 lb mol/(hr)(sqft). Although the capital and utility costs are prior to 1975 and are individually far out of date, the relative costs are roughly the same so the conclusions of this analysis are not far out of line. Conclusion For systems with nearly ideal VLB, R is approx. 1.2Rmin and N is approx. 2.0A/min-(Happel and Jordan, Chemical Process Economics, Dekker, New York, 1975). 

Mitsubishi Gas Chemical process. Economic data (France conditions, mid-1986)... 

J. HappcI, "Chemical Process Economics, John Wiley Sons, Inc., New York, 1958. 

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