Design problem statements

This case study is based upon the senior design report by Brass and Lee [5], which was prepared at the University of Pennsylvania in the Spring 2003. The design problem statement was formulated by the first author, who served as the faculty advisor. 

Have examined the primitive design problem statements presented herein and gained familiarity with some of the problem statements on the multimedia CD-ROM that accompanies this book. 

For additional details of this process design, see the design report by Lee et al. (1995). Also, see Problem A-Il.1.10 in the PDF, Design Problem Statements.pdf, on the multimedia CD-ROM that accompanies this textbook for the design problem statement that led to this design,... 

Samples of design reports are available in the libraries and repositories of technical reports maintained by companies and universities. In a few cases, they are available by Interlibrary Loan for example, the design reports prepared by students at the University of Pennsylvania since 1993. Note that titles of the problem statements that led to these reports are reproduced in Appendix II of this textbook, with full problem statements included in the file. Design Problem Statements.pdf, on the CD-ROM that accompanies this textbook. 

Table 4.1. Design problem statement in reactive distillation...

As can be inferred from the problem statement, for a given waste-reduction situation the MEN synthesis task attempts to provide cost-effective solutions to the following design questions ... 

S.A. Hiller, V.E. Golender, A.B. Rosenblit, LA. Rastrigin and A.B. Glaz, Cybernetic methods of drug design. 1. Statement of the problem—The Perceptron approach. Comp. Biomed. Res., 6(1972)411-421. 

For this example, the controller design was carried out using the MATLAB Model Predictive Control toolbox, which includes a QP solver. Three cases were considered in the preceding problem statement. 

Chemical process design, as it is commonly known, typically starts with a general problem statement with respect to the chemical product that needs to be produced, its specifications that need to be matched, and the chemicals (raw materials) that may be used to produce it. Based on this information, a series of decisions and calculations are made at various stages of the design process to obtain first a conceptual process design, which is then further developed to obtain a final design, satisfying at the same time, a set of economic and process constraints. The important point to note here is that the identity of the chemical product and its desired qualities are known at the start but the process (flowsheet/operations) and its details are unknown. 

Problem Statement and Design Criteria. Propose a suitable replacement for enamel for use in coating a human tooth. The primary design criteria are ... 

This example provides more detail on the solution of the problem that was introduced as Example 1.1. The original problem statement was to optimize the design of a distillation column to separate 225 metric tons per hour of an equimolar mixture of benzene, toluene, ethylbenzene, paraxylene, and orthoxylene with minimum total annualized cost. The feed is a saturated liquid at 330 kPa. The recovery of toluene in the distillate should be greater than 99%, and the recovery of ethylbenzene in the bottoms should be greater than 99%. 

The results from the rigorous model with the inputs specified as above show a flow rate of 1084.5 kg/h of n-hexane in the distillate product. This exceeds the requirements calculated from the problem statement (1065.5 kg/h). The simplest way to get back to the required specification is to use it directly as a specification for the column. From the Design tab on the column window, we can select Monitor and then Add spec to add a specification on the distillate flow rate of n-hexane, as shown in Figure 4.50. This specification can then be made active, and the bottoms flow rate specification can be relaxed. When the simulation is reconverged, the bottoms flow rate increases to 19,350 kg/h, and the n-hexane in the distillate meets the specification flow rate of 1065.5 kg/h. 

In addition to the fixed capital investment, we should also make an allowance for a process royalty. The problem statement did not specify whether the plant was to be built using proprietary technology, but it is reasonable to assume that a royalty will need to be paid. If a 15 MM royalty is added, then this annualizes to a cost of 3 MM/y, or roughly 0.5% of revenues, which is a reasonable initial estimate. This should be revisited during more detailed design when discussions with technology vendors take place. 

The problem statements are intentionally short, and little information is given beyond one or two references. Most of the problems are referenced to U.S. patents that give process concepts, chemical paths, and yield data, as this is often the starting point for technical and economic analysis in industrial design. There is no copyright on U.S. patents, and all of the referenced patents are available in the online material at http //books.elsevier.com/companions. Patent references are not given for older traditional processes, as flowsheets and yields for these processes can be found in the encyclopedias listed in Chapter 8. 

Conceptual process design is an underdefined problem. Only a very small fraction of the information needed to define a design problem is available from the problem statement. The design decisions of the process designer provide this missing information. For example, the designer makes design decisions about what kind of process units to use, how to interconnect those units, and so on. From this perspective, the conceptual... 

---