Retrofit design

Frameworks for examining flowsheets that account for modifications to existing processes in operations (i.e., design retrofitting)... 

Reliability and maintainability Machines and systems will be specified, designed, retrofitted, and installed with greater reliability and ease of maintainability. 

This chapter is organized to deal with a number of retrofit issues dedicated to batch plants. First, the typical features of batch plants are presented in Section 8.2. This is essential for the reader to understand the formulation of the batch design/retrofit problem in which they are intrinsically captured, as highlighted in Section 8.3. Section 8.4 is then devoted to... 

The continuous-time representation has the same ambition events are allowed to take place at any point in the continuous domain of time. This is carried out by introducing the concept of variable event time that can be defined either globally or for each unit. For this purpose, additional variables are necessary to determine the timings of events. Since a major fraetion of the inactive event-time interval assignments is eliminated with the continuoustime approach, the resulting mathematical models require less computational effort for their solution of the associated scheduling task involved in design/retrofit problems. However, the mathematical models involved in the continuous-time approach may embed more complicated structures compared with their discrete-time counterparts. 

Design/Retrofit Problems A Four-Level Framework... 

Whatever the case of batch plants, either of multiproduct or multipurpose nature, few works have addressed the retrofit problem compared with the batch plant design problem. Most of the mathematical formulations used to model the retrofit problem usually lead to optimization-oriented problems. It must be also emphasized that scheduling is intrinsically associated with batch plant design/retrofit, and is part and parcel of the formulation of both issues. It can be considered as a sub-problem of the design/retrofit problem. As highlighted in the compared formulation of these companion problems, the retrofit problem appears to be a more constrained problem. Yet, the basic solution strategy involves the same mathematical approaches and tools. 

Since the design/retrofit problem embeds batch plant scheduling, it systematically includes the determination of the production sequence and the equipment sizes based on a performance criterion. Equipment sizes are considered either as continuous variables or as discrete ones and so the problem can involve either discrete variables or a set of mixed ones. Most of the existing literature has focused on single objectives involving a cost criterion typically based on capital investment. This criterion is generally expressed as a non-linear function of the size of the equipment, following the six-tenths rule. 

Eor design/retrofit problems, profitability analysis is scarcely performed on net present value assessment, since most often a given production level has to be reached leading to fixed revenue. NLP formulations are developed that are later on reformulated as MILP problems such as those proposed by Voudouris and Grossmann (1992). This was possible by assuming discrete sizes for the potential equipment to be installed in the plant. 

The interested reader is referred to the abundant literature dedicated to the presentation of the methods implemented in the GAMS solvers. Only the basic principles of some algorithms that are different in nature and used recurrently for the solution of design/retrofit problems are outlined below. More information can be found in Ponsich and Azzaro-Pantel (2007). 

Stochastic methods Stochastic algorithms have proven their efficiency to tackle high combinatorial problems such as those encountered in design/retrofit problems. Stochastic methods (such as simulated annealing and tabu search) or techniques based on social intelligence (ant colonies and particle swarms) or cultural concepts have been largely... 

Design, Retrofit and Revamp of Industrial Water Networks using Multi-objective Optimization Approach... 

Consider a smaller refinery water network problem by ignoring some processes in Table 12.1, and perform design, retrofitting and revamping via multi-objective optimization for two objectives, namely, fresh water consumption and total flow through the regeneration units, as in this chapter. 

The overall mathematical program to tackle the simultaneous SC design-retrofitting and product development pipeline planning so as to maximize the expected CV... 

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