Process feasibility

A. Chauvel and co-workers. Manual of Economic Analysis of Chemical Processes Feasibility Studies in Eefining and Petrochemical Processes, McGraw-Hid Book Co., Inc., New York, 1980. 

The data used to generate the maps is taken from a simple statistical analysis of the manufacturing process and is based on an assumption that the result will follow a Normal distribution. A number of component characteristics (for example, a length or diameter) are measured and the achievable tolerance at different conformance levels is calculated. This is repeated at different characteristic sizes to build up a relationship between the characteristic dimension and achievable tolerance for the manufacture process. Both the material and geometry of the component to be manufactured are considered to be ideal, that is, the material properties are in specification, and there are no geometric features that create excessive variability or which are on the limit of processing feasibility. Standard practices should be used when manufacturing the test components and it is recommended that a number of different operators contribute to the results. 

The principal technological changes in the engineering control of air pollution were the perfection of the motor-driven fan, which allowed large-scale gas-treating systems to be built the invention of the electrostatic precipitator, which made particulate control in many processes feasible and the development of a chemical engineering capability for the design of process equipment, which made the control of gas and vapor effluents feasible. 

For the synthesis of chemicals from CO/H2 three considerations will influence the economics and process feasibility, namely the ratio of C0 H2, the loss of oxygen as by-product water or CO2, and the interrelation of chemicals/fuels. The two first points are exemplified in Table I. 

The process parameters developed at this stage may not be fully scalable however, one can process 20 to 100 g of material. Figures 16 and 17 show various smaller size units that can be used for process feasibility and preliminary development work. 

The need for a pilot plant is a measure of the degree of uncertainty in developing a process from the research stage to a full commercial plant. A modification to a well-known process may go direcdy from basic research work to design of a commercial plant using this approach for a brand new process risks a significant failure. Hence, one or more intermediate size units are usually desirable to demonstrate process feasibility as well as to determine safe scale-up factors. 

Control is the manipulation of a degree of freedom (e.g., heater, cooler or exchanger load, stream split fraction) in order to make a process feasible and/or economically optimal in the steady state. In this chapter, control is used in a static sense only process dynamics are not considered. 

To help carry out such an evaluation we have prepared a flow chart, shown in Table V, which presents the important considerations in a systematic manner. These are two main branches, zeolite selection and process feasibility. The process feasibility initially assumes the worst case for the design parameter estimates, but these can be revised if the zeolite selection process indicates that higher capacity or shorter MTZ might be encountered. Having... 

In conclusion, the approval of Restasis by the FDA is an important milestone in lipid emulsion research for ophthalmic application. This approval reflects the achievements of the last decade in terms of the availability of better ingredients, improved manufacturing processes, feasibility of sterilization, and better understanding of the optimization process. In all of the comparative studies done so far, positively charged SME achieved better ocular bioavailability regardless of the studied drug. Research efforts are underway to further explore the mechanism of interaction of positively charged SMEs with ocular tissues and to translate the results of this research into enhanced clinical performance. 

The observation that so many compounds reduce in such a narrow potential range is curious. We hypothesize that one reason is that many of these reactions are catalyzed via the TAA+/TAA-mercury couple. The mediated reactions then include reduction of compounds, like benzene, whose E° for single electron transfer is more negative than —3.1 V(SCE). A second reason for the possibility of reducing many compounds in this narrow potential range is that the reduction rates often depend on proton availability, which can be adjusted to make the process feasible. 

Solubility limitations require that the solvent-to-oil feed ratio be high an economic analysis is needed to establish process feasibility. The use of cosolvents or higher temperatures can be used to increase oil solubility and to decrease sol vent-to-oil feed ratio. These process modifications, however, cause additional thermal degradation. With cosolvents, thermal degradation occurs during the distillation step needed to remove these unwanted components (and flavors) from the desired extract. 

Progress in the techniques of classical strain development and metabolic engineering (Box 24) have made a growing number of fermentation processes feasible and economically attradive. Beside the bulk amino acids, lactic acid, penicillins for the pharmaceutical market, and some vitamins, for example vitamin C (ascorbic acid... 

It should be noted that the equivalent continuously operated process of the batch reactive membrane process is the membrane reactor depicted in Fig. 4.26(b). Here, the spatial coordinate z replaces the time coordinate of the batch process. Feasibility analysis has the task of estimating the retentate composition which is attainable at infinite reactor length. 

Patents provide valuable technology information for designers. Firstly, information about process feasibility may be collected with respect to chemistry, catalyst, safety and operation conditions. Qualitative data regarding the reaction engineering, such as conversion and selectivity, as well as the productivity and residence time are useful for the selection of the chemical reactor. Even more important are data regarding the reaction-mixture composition for the assessment of separations, namely with respect to byproducts and impurities. 

Oxidation of hydrocarbons with dioxygen is more facile when the C-H bond is activated through aromatic or vinylic groups adjacent to it. The homolytic C-H bond dissociation energy decreases from ca. 100 kcal mol-1 (alkyl C-H) to ca. 85 kcal mol-1 (allylic and benzylic C-H), which makes a number of autoxidation processes feasible. The relative oxidizability is further increased by the presence of alkyl substituents on the benzylic carbon (see Table 4.6). The autoxidation of isopropylbenzene (Hock process, Fig. 4.49) accounts for the majority of the world production of phenol [131] ... 

The many criteria that must be satisfied to make a process feasible on the industrial scale require that great care be taken in the development of each process to ensure safe and economical operation. The development of an industrial chemical process typically involves the following steps ... 

However, certain substituents can make the process feasible because they are able to stabilize the aryllithium. For instance, treatment of methoxybenzene with BuLi leads readily to the 2-lithio derivative 1 (Scheme 10.3). 

We note that the liquid/liquid extraction step accomplishes separations across three relatively azeotropic compositions namely, that between acetone and pentane. that between methanol and pentane, and that between water and pentane. It should also be noted that, since the extractor does not have to perform sharp separations, it requires an overall optimization to determine how many stages should be used. In principle, a single stage or, in other words, a simple decanter should suffice to make the process feasible. 

In commercial diarcoal production, diarcoal yields of 0.33-0,41 kg/kg dry feed are possible (4). However, the residence times for the solids used in commercial charcoal productiwi, 12 18 hours (4), would result in a rather large and expensive pyrolysis reactor. Shortff residence times of the solids in the pyrolysis process are required to make the CASST process feasible. To determine whether the required diarcoal yields can be achieved at shorter residence times, pyrolysis experiments with willow wood have been performed. 

Sedimentation and/or filtration (26,28) will be feasible for separating the insoluble chromium hydroxide precipitates (or chemical floes) from a wastewater. Other feasible solid-water separation processes for removing the insoluble chromium hydroxide include membrane filtration (such as ultrafiltration and microfiltration), continuous DAF, PC-SBR-sedimentation, PC-SBR-DAF. The following is a summary of the solid-water separation processes feasible for the combined application of chemical reduction and precipitation. 

Also in the case of the TBP process, only simulated HAW solutions have been until now used to study the process feasibility. Results have already been reported (9), which indicated that separation yields of about 99.9% can be obtained for Am after three successive extraction stages operating with a concentrated HAW solution adjusted to 0.1 — 0.2 M HN03, 0.65 M AI(N03)3 and 1.3 M NaN03. The back-extraction of all the actinides and RE from loaded TBP (30% in n-dodecane) was carried out by means of Na5 DTPA-glycolic acid solution which can be then used directly to separate Am and Cm from RE according to the Talspeak process (15). 

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