Economic Loop Design

Sample Problem 6. A loop which has the ratio a = G/H = 3 and j3 = W/H = 5, and the solution indicates the Bending Moment = 50,000 Ib./in. and the Expansion Stress = 30,000 psi, the loop exceeds the allowable limits. 

Design a 17-type symmetrical expansion loop to yield the maximum moment and stress equal to the allowable limits. 

Therefore, the distance of the guide G = 5.7(if). If the G is increased to 5.7(H) then the new shape will yield a stress of 15,000 psi. which is equal to the allowable stress. 

The system is treated with square comer intersections. 

The system is composed of straight pipe elements of uniform size and thickness. 

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In the course of this chapter the economic-driven design (classical design) was implicitly compared with a new bi-optimized design (green design) for the case of a MTBE RD column. A set of indicators can be used to compare both designs ( ) exergy loss and a) closed loop control performance. 

ALWRs are expected to be deployed ia the United States and ia Asian counties. However, France will use improved versions of standard reactors, considering them to be amply safe and economical. The reactors were modified after the Three-Mile Island-2 (TMI-2) accident. The company Framatome that has built most of the reactors of France is associated with Babcock Wilcox ia the United States. The new Framatome 1500 MWe N4 PWR is an extension of the successful four-loop units of 1300 MWe originally designed by Westiaghouse. Full emphasis is givea to safety, ecoaomy, and rehabiUty. More severe design criteria than those ia the former model have beea adopted. 

Systems are designed to function normally even when a single instrument or control function fails. This is achieved with redundant controls, including two or more measurements, processing paths, and actuators that ensure that the system operates safely and reliably. The degree of redundancy depends on the hazards of the process and on the potential for economic losses. An example of a redundant temperature measurement is an additional temperature probe. An example of a redundant temperature control loop is an additional temperature probe, controller, and actuator (for example, cooling water control valve). 

The starting point in the development and designing of a closed water loop system is an inventory of the amounts and the quality of the process and transport water flows which are needed for the various steps in the production process. Each production step where process or transport water is involved causes a certain amount of wastewater. The pollution of this water is strongly dependent on the process step. The selection of separate treatment steps which, together, comprise a closed loop water system is complex. As already mentioned, various complete treatment scenarios can be developed and designed to satisfy the requirements set for process and transport water and treatment of wastewater. A technical and economic evaluation, in combination with environmental sustainability assessment, is necessary to determine the treatment system which is most appropriate. 

Economic analysis of designs at lower natural hypochlorite strengths equally show potential investment benefits. They are, however, much less significant than the batch and high concentration cases described above. While an economic case can be made for retrofitting an in-loop reactor to a system that already has an end-of-pipe treatment system based on payback, it is not always clear that this is a better option than an end-of-pipe hybrid system as described earlier in the chapter. For a particular system the optimum solution is often as much a function of the required expenditure on the heat exchangers as it is the relative cost of the reactor options. 

Besides the two main characteristics of sensitivity as well as specificity of a sensor, the industrial, military, and other standards demand the device to be portable, economical, autonomous, and power efficient. In order to address some of these characteristics, the authors in their respective laboratories have been working on improving the design of the prototype, as shown in Figs. 15.6 and 15.7, respectively. The necessaiy electronics consisting of local oscillators, beat oscillators, smaller cavities, mixers, and phase-locking loops have been assembled in prototypes. As of this date the device needs further evaluation in an operational environment to establish a set of encyclopedic data and for comparison with unknown toxins. 

Luyben (1993a) provided valuable insights into the characteristics of recycle systems and their design, control, and economics, and illustrated the challenges caused by the feedback interactions in such systems, within a multi-loop linear control framework. Also, in the context of steady-state operation, it was shown (Luyben 1994) that the steady-state recycle flow rate is very sensitive to disturbances in feed flow rate and feed composition and that, when certain control configurations are used, the recycle flow rate increases considerably facing feed flow rate disturbances. This behavior was termed the snowball effect. ... 

Arbel et al. (1997) give a detailed account of this procedure applied to a fluidized catalytic cracker unit control is possible when only one of the four dominant variables is under feedback control. The effectiveness of the partial control scheme is limited in satisfying the economic objectives when only one dominant variable is in closed-loop control. Superior reactor performance is achieved when all four dominant variables in the reactor are used. However, this requires manipulated variables that were not part of older FCC designs. The new manipulators have been added on modern units to make... 

The semicontinuous design allows a more efficient heat recovery than a batch system. Heat recovery is perfomed by means of indirect economizers (Figure 12). Steam produced in the bottom deodorized oil-cooling section is sent in a closed thermosiphon loop to the top bleached oil-heating section to heat the incoming oil. A single thermosiphon system has a recovery efficiency of 50%. With a double system, coupled with a low-pressure steam-production device, up to 75% of heat can be recovered. 

A thorough analysis of the capital and operating economics was made for the system described above. The basis for this estimate is shown in Table III, and relatively conservative assumptions have been made for the cost of the various utilities, maintenance, operating supplies, overhead, and capital charge rate. The analysis was based on designing the plant for the equivalent of 7000 hr/yr of full load operation. The capital costs, broken down into the gas interface loop and the regeneration system, are shown in Table IV. The cost for the scrubber loop and its asso-... 

Suction piping should be designed without loops or pockets. The suction line is generally one or two sizes larger than the pump suction nozzle. Table 7-2 gives unit pressure drops at various flow rates, which will give economical pump discharge header sizes. Leads to the header are one size smaller — but not smaller than the pump nozzle. 

Economics Thanks to its design, the Casale split flow loop process is highly efficient for a given capacity, process benefits include low investment due to smaller sized equipment and low medium-pressure steam consumption (22 bar, superheated) of 750 kg/metric tons and almost stoichiometric raw material consumption. 

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