Feasible designs definition

Since the reflux ratios are, by definition, dependent on the net flow of a particular CS, the same arguments put forward in Sections 7.3.2 wiU hold for reflux ratios with regard to net FPs. For instance, choosing a FP that will lead to CS2 having a negative net flow will cause the value of R 2 to also be negative in this CS. However, because is defined as the ratio of liquid flowrate to the net flowrate in a particular CS, the actual value of in a particular CS depends on the quality of the feed, and whether the side-draw product is liquid or vapor. Just as we have conveniently represented net flow patterns in >-space, we can also then construct lines of constant reflux in the >-space, which will ultimately allow us to hone in on feasible designs, as will be illustrated in Section 7.4. In order to do this, it is necessary to write all our reflux equations in terms of v and as shown in the equations below... 

In the case of this cybernetic definition, a design problem, or specifically problem formulation, is considered as input while the design is considered as the output of our designing system. The term transformation describes all complex design activities that occur during the entire process. In the case of routine design processes, the probability of this transformation P(T) = 1. It means that there is no doubt that a transformation will take place and a feasible design will be produced. Such situation may be called... 

We start with a definition of the problem and based on this, we identify the candidates (such as, molecules, mixtures and formulations) through expert knowledge, database search, model-based search, or a combination of all. The next step is to perform experiments and/or model-based simulations (of product behavior) to identify a feasible set of candidates. At this stage, issues related to process design are introduced and a process-product match is obtained. The final test is related to product quality and performance verification. Other features, such as life cycle assessment could also be introduced at this stage. 

The same modern incinerators equipped with scmbbers, bag-filters, electro-precipitators, secondary combustion chambers, stacks, etc., are equally efficient for disposal of hazardous PCBs, dioxin, USEPA priority pollutants, and so on, if they are properly designed, installed, and managed. Incineration technology is definitely feasible, and should not be overlooked. The only residues left in the incinerators are small amount of ashes containing metals. The metal-containing ashes may be solidified and then disposed of on a landfill site. 

With the exception of one supplier all indicated that this model is also suitable for small and very small enterprises. Considering the answers to the first question it still has to be examined whether a comprehensive contract design (with the definition of the obligations of the involved parties) and the definition of a new charging basis will be feasible also in very small enterprises, since only rather small quantities of the products are moved. 

The economic feasibility of the process should be established at this stage. Again, this is only an introductory assessment performed more to establish that the plant is not definitely a loss-maker, rather than deciding that it is a particularly attractive proposition. A full and detailed economic evaluation of the plant and process is performed later in the design study (see Chapter 6) after the process route has been finalised, a detailed equipment listing prepared, and preliminary equipment designs have been performed. The following steps need to be performed to establish the economic feasibility of the process ... 

Table 8.1 describes the steps of the methodology in more detail. The procedure starts with the Problem definition production rate, chemistry, product specifications, safety, health and environmental constraints, physical properties, available technologies. Then, a first evaluation of feasibility is performed by an equilibrium design. This is based on a thermodynamic analysis that includes simultaneous chemical and physical equilibrium (CPE). The investigation can be done directly by computer simulation, or in a more systematic way by building a residue curve map (RCM), as explained in the Appendix A. This step will identify additional thermodynamic experiments necessary to consolidate the design decisions, mainly phase-equilibrium measurements. Limitations set by chemical equilibrium or by thermodynamic boundaries should be analyzed here. 

Eront-End Engineering and Design (FEED) focuses on obtaining accurate cost estimates for the major items of process equipment and further definition of the most sensitive parts of the overall project cost. It is denoted Eront-End because this is performed prior to final corporate board and financial approval for the overall project. EEED costs typically 5 to 10% of the overall project cost - thus for a 1,000 million project expenditure of about 100 million will be required. Only after the feasibility and FEED will the cost error be in the vicinity of +1-5%. In many instances, especially for new technology or for a remote location or offshore, the error will still be in the region of +/-10% or more. 

There is no succinct and universally accepted definition of a pilot trial. It is usually open in design and small in scale. Its use sometimes implies some degree of uncertainty either about the safety (for example narrow therapeutic ratio) or efficacy of the medicine, or doubt about testing it in a particular context or indication. Pilot studies may examine feasibility (i.e. examine in one small-scale study the sense and practicability of testing a... 

Since the Estimation task is not defined in the class diagram, the manager makes use of the unconstrained type Task to insert it into the task net as an untyped task. This modification degrades the consistency level of the task net to weakly consistent. Unfortunately, inconsistencies are introduced, as well The flowsheet design task has to be supplied with the estimation as input parameter. This was excluded in the process definition by the value false of the tag AllowStandardParameters. Therefore, the manager has to switch off consistency enforcement explicitly to make the modification feasible. 

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